Aviation MRO HVAC Duct Guide — Hangar, Aircraft Paint Strip, Composite Repair, Avionics, Engine Test Cell, NFPA 409 + AS/NZS 60079 + AS 1668.2

Why aviation MRO HVAC is the hardest discipline in industrial ventilation

An aircraft hangar is the only HVAC environment in the country where a single ductwork failure can simultaneously trigger a confined-space fatality in a fuel tank, asphyxiate a composite repair technician on respirable carbon dust, ignite a hangar floor jet fuel spill the size of a swimming pool, expose an entire pre-paint preparation shop to IARC Group 1 hexavalent chromium aerosol, and send a 600 degree Celsius engine test cell exhaust plume into the wrong stack. Every ductwork drawing for a maintenance, repair and overhaul facility lands under the joint authority of CASA, the Defence Aviation Safety Authority DASA, Airservices Australia, the state EPA and the WorkSafe regulator. Aviation MRO ductwork sits at the intersection of NFPA 409 hangar fire protection, NFPA 410 aircraft maintenance, NFPA 415 aircraft fuel servicing ramps, NFPA 423 jet engine test cell, NFPA 86 industrial furnace and oven for autoclave composite cure, NFPA 30 flammable liquid, and the AS/NZS 60079 hazardous area framework that Australia adopts as the local IEC 60079 implementation for ATEX-equivalent zoning.

This guide is the same engineering reference our SBKJ application team uses when an Australian aviation MRO operator scopes duct fabrication for a hangar fit-out, a paint hangar conversion, a composite production line expansion, an avionics bay refurbishment or a jet engine test cell rebuild. We have built the duct fabrication machinery on projects ranging from regional turboprop line bases in Wagga Wagga and Coffs Harbour through to wide-body heavy maintenance at the major Australian capital city hubs and into defence depot support at Williamtown NSW, Amberley QLD, Edinburgh SA, Tindal NT and East Sale VIC. The patterns repeat. The hazardous area zoning is unforgiving. The CASA technical airworthiness chain compounds on top of the building code stack.

Six conditions make aviation MRO HVAC harder than any other industrial ventilation problem in the country. First — the hazardous area is permanent and intrinsic to the asset. An aircraft is by definition full of jet fuel JP-8, AVTUR Jet A-1 kerosene or AVGAS 100LL legacy general aviation petrol-equivalent, and Zone 1 hazardous area follows the aircraft around the hangar floor. Second — the dimensional scale is enormous. A Group I hangar holding a Boeing 787 Dreamliner at Qantas Mascot or a 747 cargo aircraft is 100,000 square metres of single-fire-area with 25 to 35 metres of clear span overhead, so the ductwork is sized for 700 cubic metres per second of make-up air supply against the largest single-building HVAC load in Australian commercial infrastructure. Third — the operator exposure mix is the worst in any sector. Jet fuel benzene, isocyanate TDI/MDI at 0.005 ppm STEL, Cr VI chromate at 0.05 mg/m cubed STEL, beryllium copper alloy connector machining at 0.001 mg/m cubed STEL, formaldehyde from phenolic composite resin, and respirable carbon fibre dust at 5 mg/m cubed all sit on the same hangar floor through a single working shift. Fourth — the regulatory chain is uniquely deep. CASA technical airworthiness sits over DEF (Aust) 5613 for defence platforms, IEC 60079 sits over AS/NZS 60079 for hazardous area, NFPA 409 sits over AS 1668.1 for smoke spill, and the building code Class 8 industrial classification sits over Class 7b storage if the same hangar holds bonded jet fuel. Fifth — the asset value at risk is extreme. A wide-body Boeing 787 Dreamliner in heavy maintenance check carries an asset value of 300 million Australian dollars on the hangar floor through a six-week D-check cycle, and an F-35A Lightning II in depot is 150 million Australian dollars per airframe, so any ductwork-initiated event that damages an aircraft is a defence procurement disaster. Sixth — the cycle time is intolerant of HVAC downtime. An airline runs a heavy maintenance bay on a strict slot schedule against contracted aircraft availability targets, so any HVAC outage that grounds an aircraft beyond the contracted window triggers contractual penalties measured in millions of dollars per day.

Aviation MRO process zones — eleven distinct ductwork environments under one roof

A modern Australian aviation MRO facility splits into eleven sequential or parallel process zones, each with its own ductwork specification. The duct designer cannot specify any zone in isolation because the building code, hazardous area framework, smoke spill system and fire suppression all chain through the entire facility.

Zone 1 — Aircraft hangar floor (Group I, II or III per NFPA 409). The single largest HVAC asset in the facility. A Group I wide-body hangar at Qantas Engineering Mascot Sydney, Brisbane, Melbourne, Cairns or Perth — sized for a 747 cargo or Boeing 787 Dreamliner or A380 wide-body — runs 80,000 to 120,000 square metres of single-fire-area with 25 to 35 metres of clear span overhead. NFPA 409 mandates 4 air changes per hour mechanical ventilation, smoke removal capability of 6 ACH within 30 seconds of fire alarm activation, high-expansion foam suppression at 1,500 litres per minute per square metre discharge density using UFC universal foam concentrate, ESFR sprinkler at 5 m intervals overhead, jet fuel spill drainage with separator pit, thermal imaging FLIR camera coverage of the entire hangar floor, and Zone 1 hazardous area classification within 1.5 metres of any aircraft per AS/NZS 60079.10.1. Group II at Jetstar Engineering Tullamarine and Virgin Australia Brisbane line maintenance falls in the 1,394 to 3,716 m squared single-fire-area range for narrow-body Airbus A320 and Boeing 737 service. Group III at Rex Engineering Wagga Wagga for the Saab 340 regional turboprop fleet and at Hawker Pacific corporate jet bays at Sydney, Melbourne and Cairns sits under 1,394 m squared. Group IV membrane-covered hangars are rare in Australian commercial aviation but appear on temporary RAAF deployment sites.

Zone 2 — Jet engine test cell. NFPA 423 governs the entire test cell design. Test cells for Pratt and Whitney, Rolls-Royce, GE Aerospace, CFM International, IAE V2500 and Honeywell engines run at TAE Aerospace Adelaide and Tindal RAAF for T56 turboprop and GE F404 fighter engine. The test cell is a bullet-shaped acoustic tunnel absorbing 50 to 130 dB of noise, with a 4 to 6 metre diameter inlet for bypass air and a sound attenuator at the exhaust end. The engine exhaust gas leaves the turbine at 600 to 800 degrees Celsius, mixes with bypass air through the augmenter section and exits the stack at 200 to 400 degrees after augmenter cooling. Atomised jet fuel is present continuously during testing, N2 or CO2 emergency suppression is mandatory, and continuous fuel-air ratio monitoring shuts the cell on any deviation. Duct material in the augmenter is 309S or 310S stainless at 3 to 6 mm wall thickness, cut on heavy-gauge plasma equipment and welded manually with full penetration TIG passes.

Zone 3 — Maintenance and overhaul hangar. The heavy maintenance bay where the D-check cycle (6-yearly major overhaul), C-check cycle (18 to 24 month intermediate overhaul), and base maintenance work is performed. Line maintenance for the light A-check, transit work, tow tractor parking and ramp activity occupy adjacent bays. Air change rate is 4 to 6 ACH for general ventilation, rising to 10 to 15 ACH during open fuel tank work or composite repair sanding inside the hangar.

Zone 4 — Aerospace paint booth. The polyurethane topcoat application zone for aircraft livery refresh and primer application. Modern aerospace paint chemistry includes Sherwin-Williams Imron AVI, Akzo Nobel Awl-grip, PPG Desothane, Mankiewicz Alexit and ZEUS — typically a chromate-free Skydrol-resistant polyurethane topcoat over an epoxy primer. The booth runs as a downdraft enclosure at 0.4 to 0.5 m/s vertical velocity, classifies as Zone 1 hazardous per AS/NZS 60079.10.1, uses conducted-only spraying because of solvent flash risk, requires supplied-air respirators for the operator, and discharges high-VOC plus isocyanate TDI/MDI exhaust at 200 to 1,500 ppmv VOC concentration. Pre-paint surface preparation includes Cr VI chromate conversion coating with Iridite or Alodine 1200 — the Cr VI exposure being phased out for non-chromate SAA, TSA and BSAA anodise alternatives.

Zone 5 — Paint stripping and chemical deplaint. The bath where existing paint is removed before livery refresh or corrosion inspection. Modern paint stripper chemistry is benzyl alcohol or phenol or n-methyl pyrrolidone NMP biodegradable replacement (Tytan, Eldorado, Bonderite Greesoff, EnviroStrip) since methylene chloride DCM was banned in EU 2014 and Australia 2023. The bath operates 50 to 80 degrees Celsius with intermittent steam clean rinse, generating high-VOC exhaust laden with paint debris particulate. Duct material is 316L stainless throughout with chemical-resistant gaskets at all flanged joints.

Zone 6 — Composite repair and autoclave cure. CFRP carbon fibre reinforced plastic, AFRP aramid Kevlar and GFRP glass fibre composite repair across Quickstep Composites Bankstown (F-35A vertical tail and horizontal stabilizer plus Boeing C-130 spare), Boeing Aerostructures Australia Fishermans Bend (Boeing 787 Dreamliner wing flap, aileron and spoiler plus 777X and 737 MAX work) and Marand Precision Engineering Melbourne and Adelaide. Autoclave cure runs at 180 to 200 degrees Celsius and 7 bar nitrogen pressure for 2 to 4 hours per cure cycle. Uncured prepreg dust during layup and cured composite dust during sanding, drilling and machining generate respirable carbon fibre at 5 mg/m cubed WES.

Zone 7 — Avionics bay and electrical equipment. Radar, navigation, communications, In-Flight Entertainment IFE, and Electronic Warfare EW equipment service across F-35A APG-81 AESA, E-7A Wedgetail Northrop Grumman MESA Multi-role Electronic Scanning Array, P-8A Poseidon APY-10 radar and BAE Systems Australia Mascot avionics shop work. The bay runs ESD-safe (electrostatic discharge controlled) with conductive flooring, ionised supply air and continuous static field monitoring. ASHRAE TC 9.9 Class A1 environment at 22 to 27 degrees Celsius and 8 to 90% RH with tight humidity ramp control to prevent condensation on cold-soaked aircraft electronics.

Zone 8 — Hydraulic shop and power pack bench. Test and overhaul of aircraft hydraulic actuators and power packs using Skydrol LD-4 phosphate ester hydraulic fluid, Mil-PRF-83282 synthetic hydrocarbon hydraulic fluid and Mil-H-5606 legacy mineral hydraulic. Skydrol phosphate ester is a skin irritant and aggressive dermatitis sensitiser, requiring fume hood and local exhaust ventilation LEV at every test bench.

Zone 9 — Engine, APU and accessory overhaul. Turbine engine, auxiliary power unit, gearbox, bleed valve, electronic hydraulic control unit EHCU and fuel control unit FCU service. TAE Aerospace at Adelaide and Tindal handles GE F404 fighter engine for F/A-18A Classic Hornet, T56 turboprop for C-130 Hercules and Lockheed P-3 Orion, and TF34 for older platforms. Toll Aviation, Honeywell, Goodrich Collins, Hamilton Sundstrand and Liebherr handle the accessory side. Process steps include degrease, ultrasonic clean, plasma electrolytic polish and non-destructive testing NDT inspection.

Zone 10 — Landing gear and oleo strut and tyre and brake overhaul. Heavy mechanical work on Messier-Bugatti-Dowty, Goodrich Collins, Honeywell, Eaton, Triumph, Bridgestone and Michelin landing gear assemblies. Legacy cadmium-plated parts are being phased out under Cd 0.01 mg/m cubed STEL exposure limit and IARC 1 carcinogen status, but components manufactured before phase-out continue to circulate through MRO. The strip and replate cycle generates Cd aerosol that requires dedicated extract to a HEPA-filtered scrubber.

Zone 11 — Specialty support shops. Machine shop with five-axis CNC, mill, turn, EDM electric discharge machining; magnetic particle inspection MPI, dye penetrant inspection DPI, eddy current EC, ultrasonic UT, thermography and X-ray radiography RT bays under CASA, ANSTO and ARPANSA licensing for ionising radiation; anodise and electroplate shops with chromate conversion Iridite phasing to non-chromate SAA/TSA/BSAA; aerospace welding bay for 4130 chromoly, stainless 304/316/321/347, A286, Inconel 625 and 718, titanium 6Al-4V, nickel Hastelloy C-276 and Monel using TIG, electron beam EB and laser beam LBW welding; chemical cleaning and vapour degrease (trichloroethylene TCE banned 2023, perchloroethylene Perc 50 STEL phasing, aqueous-based EnviroSolv, UltraSorb and Brulin biodegradable replacements); paint bake oven and IR infrared cure at 180 degrees Celsius for powder coat and 60 to 80 degrees Celsius for clear coat; wheel and tyre bay with Bridgestone, Michelin and Goodyear retread, inflation and balance; Ground Support Equipment GSE area for tug, tow bar, air-start, power-up unit and oxygen cart service.

NFPA 409 aircraft hangar group classification and high-expansion foam suppression

NFPA 409 is the single most important reference for any aircraft hangar ductwork design in Australia. Although AS 1668.2 mirrors most of the ventilation rate provisions, the hangar fire engineer always cross-references NFPA 409 because it sets the suppression and ventilation rates that the smoke spill system and the make-up air supply must match.

NFPA 409 splits aircraft hangars into four groups by single-fire-area and maximum aircraft tail height. Group I covers single-fire-area exceeding 3,716 square metres or hangars designed for aircraft with tail height over 8.5 metres. The Group I designation captures every wide-body heavy maintenance bay in Australia — Qantas Engineering Mascot Sydney Boeing 787 Dreamliner and A380 bay, Qantas Engineering Brisbane wide-body line bay, Boeing Defence Australia E-7A Wedgetail facility, the C-17A Globemaster III hangar at RAAF Amberley and Lockheed Martin Avalon F-35A depot facility. Group II covers 1,394 to 3,716 square metres single-fire-area, typical of narrow-body Airbus A320 and Boeing 737 line maintenance such as Jetstar Engineering Tullamarine and Virgin Australia Engineering Brisbane line bays. Group III covers single-fire-area under 1,394 square metres, typical of regional turboprop and corporate jet hangars including Rex Engineering Wagga Wagga for the Saab 340 fleet, Hawker Pacific corporate jet bays at Sydney, Melbourne and Cairns, and Avwest turbine engine work at Cairns. Group IV membrane-covered hangars are rare in Australian commercial aviation but appear on temporary RAAF deployment sites and forward operating bases.

Group I hangar suppression is the most demanding in any industry. NFPA 409 chapter 6 mandates high-expansion foam suppression at 1,500 litres per minute per square metre discharge density using UFC universal foam concentrate, with the foam generators sized to flood the hangar floor to 1 metre depth within 60 seconds of activation. Concurrent ESFR sprinkler protection at 5 metre intervals overhead provides secondary coverage. Jet fuel spill drainage with separator pit captures any spilled fuel before it can spread under the aircraft. Thermal imaging FLIR camera coverage of the entire hangar floor provides early detection. The combined system must hold a wide-body fuel spill fire to the area of origin and prevent flashover across the hangar floor.

The ductwork implications of Group I are significant. First, all hangar HVAC ductwork crossing fire compartment boundaries must hold a 250 degree Celsius / 2 hour smoke spill rating per AS 1668.1 and AS 1530.4 fire resistance level. Second, smoke removal at 6 ACH within 30 seconds of fire alarm activation requires dedicated smoke spill fans and ductwork separate from the general ventilation system — the smoke spill ducts are heavy-gauge construction in galvanised steel at 1.6 to 2.0 mm thickness with bolted flange joints rated for high-temperature operation. Third, the make-up air supply for the smoke spill exhaust must equal the exhaust flow within plus or minus 10% to prevent the hangar going negative pressure and pulling smoke from adjacent compartments. Fourth, the high-expansion foam generator is fed by a dedicated supply duct in galvanised at 1.2 to 1.6 mm thickness with quick-acting motorised dampers at every hangar entry point to prevent foam migration out of the hangar.

Smoke spill ductwork is fabricated on the SBAL-V galvanised configuration at 1.6 to 2.0 mm gauge with TDF flanges and continuous welded seams at any joint exceeding 1,500 Pa pressure class. Specification cross-reference to AS 4254.2 for medium-pressure galvanised ductwork construction, and to AS 1668.1 sections 5 and 6 for smoke spill system design and certification. The smoke spill exhaust fan is rated F300/120 — capable of operating at 300 degrees Celsius for 120 minutes per AS 1668.1 section 7. The duct connection from the fan to the building penetration is sleeved through a fire-rated wall opening with intumescent collar at the penetration.

AS/NZS 60079 hazardous area classification across an aviation MRO facility

AS/NZS 60079.10.1 is the Australian implementation of the IEC 60079 hazardous area framework. For aviation MRO the framework defines three zones based on the likelihood of an explosive atmosphere being present. Zone 0 covers continuous explosive atmosphere — the interior of an aircraft fuel tank during fuel-tank-entry maintenance qualifies, and during this entry the tank is inerted with gaseous nitrogen until oxygen falls below 4% by volume. Zone 1 covers explosive atmosphere likely to occur in normal operation — within 1.5 metres of an aircraft during fuelling, across a hangar floor during ramp and tow operations, inside an aerospace paint booth during conducted spray, inside the paint stripping bath canopy hood, and inside the engine test cell exterior shroud (the augmenter interior is non-hazardous because air velocity is permanent). Zone 2 covers explosive atmosphere unlikely to occur but possible — beyond 1.5 metres in the remainder of the hangar floor, within 3 metres of an open paint booth door, in the oxygen cart and AVGAS pushback service area, and in the lithium-ion battery storage room (because Li-ion off-gas including hydrogen fluoride HF and other electrolyte vapours can occur on thermal runaway).

The hazardous area classification drawing is the most important single document the HVAC duct designer needs before specifying any equipment. Every electrical penetration through the duct — fire damper actuator, smoke spill fan motor, supply air handler fan motor, control damper actuator, instrumentation transmitter — must be selected to the zone classification at the penetration point. Inside Zone 1 the electrical equipment must be Ex-d flameproof, Ex-e increased safety or Ex-i intrinsically safe to AS/NZS 60079.14, and the equipment certification must include compatible gas group (IIA for aviation kerosene, IIB for ethylene-containing solvent, IIC for hydrogen present during fuel cell APU service). Inside Zone 2 the equipment can be Ex-n non-incendive (a less stringent classification) but must still hold a current certificate.

The aviation MRO duct designer faces three specific hazardous area design challenges. First — the Zone 1 boundary follows the aircraft. As the aircraft is towed through the hangar, the Zone 1 boundary moves with it, so any electrical equipment at the hangar floor edge that was Zone 2 when the aircraft was parked in the centre of the hangar becomes Zone 1 when the aircraft moves to the edge during a wash or paint cycle. The standard solution is to classify the entire hangar floor as Zone 1 for the conservative case, which forces all electrical equipment to Zone 1 specification. Second — the aircraft fuel tank entry operation creates a moving Zone 0 boundary. The portable extract fans used to ventilate the tank interior must be Zone 0 rated (Ex-d Group IIA gas group rating with full continuous monitoring) and the extract hose connection to the rigid duct must include conductive bonding to ground through a low-resistance path. Third — the engine test cell shroud Zone 1 boundary transitions to non-hazardous inside the augmenter at the inlet bell mouth. Any electrical equipment at the augmenter inlet must be Zone 1 specification because of the boundary uncertainty under transient operating conditions.

AS/NZS 60079.14 governs the installation of electrical equipment in hazardous areas. The duct designer is responsible for ensuring that any equipment supplied by the duct fabricator (in-line dampers, fire smoke dampers, motorised dampers, balancing dampers with electric actuators) holds the correct certification before installation. The certification chain typically includes IECEx (international), ATEX (European but commonly recognised) and AS/NZS specific certifications. Equipment supplied without certification cannot legally be installed inside a Zone 1 or Zone 0 area and the duct contractor will be liable for the strip-out cost if discovered during the AS/NZS 60079.14 audit.

Jet fuel vapour extraction during aircraft fuel tank entry maintenance

Aircraft fuel tank entry is among the highest-risk maintenance operations in any aviation MRO facility. The interior of an aircraft fuel tank is by definition Zone 0 — continuous explosive atmosphere. ATA Spec 100 Chapter 28 governs the entire fuel tank entry procedure across commercial aviation worldwide, and CASA Civil Aviation Safety Authority approved entry permit procedures provide the Australian specific implementation. The operation is performed during heavy maintenance C-check and D-check cycles to inspect tank interior corrosion, replace fuel boost pumps, replace fuel quantity indication probes, repair sealant and address any fuel system airworthiness directive.

Before any entry the fuel tank is drained as far as physically possible — typically 90 to 99% of bulk fuel can be removed but residual fuel on tank walls, in low-point drains and in stringer fillet welds will continue to evaporate during the entry. The tank is then inerted with gaseous nitrogen until oxygen falls below 4% by volume, measured at multiple points inside the tank. Inerting alone does not allow entry — at 4% oxygen the atmosphere is acutely asphyxiating to any unprotected operator. Following inerting, the tank is ventilated with portable explosion-rated extract fans at 30 to 60 air changes per hour through flexible conductive ducting connected to the rigid ductwork in the surrounding hangar. Ventilation continues until lower explosive limit LEL falls below 10% of LEL for the residual fuel vapour (typically JP-8 or AVTUR Jet A-1) and oxygen returns to 19.5 to 23.5% by volume. Only then is the tank cleared for human entry, and even then the operator wears a supplied-air respirator with continuous LEL and oxygen monitoring on the chest pack.

The jet fuel WES is 200 ppm for kerosene total, 1 ppm STEL for benzene (the killer exposure — benzene is IARC Group 1 carcinogen and known leukaemogen), 10 ppm for naphthalene, and approximately 200 ppm for petroleum hydrocarbon as decane. AVGAS 100LL adds 0.05 mg/m cubed STEL for lead inorganic from the tetraethyl lead additive in legacy general aviation petrol. Operator-breathing-zone monitoring is continuous, the permit holder shuts the entry on any single WES exceedance, and the entry is logged against the operator's lifetime cumulative exposure record.

The fixed hangar ductwork that connects to the portable fuel tank extract operation is fabricated in 316L stainless at 1.5 mm gauge with full conductive bonding throughout. The 316L specification reflects the chloride content of jet fuel additives and the long service life expected of a fixed connection that may see hundreds of fuel tank entry cycles across the aircraft service life. Conductive bonding is achieved by spot welding a 25 mm copper braid pigtail across every flanged joint, with the entire duct system earthed to building structural steel at the fan housing and at every wall penetration. SBAL-V 316L configuration produces the rectangular sections and SBFB-1500 produces the round riser duct. Velocity is 8 to 12 m/s in the rigid duct to keep the residual fuel vapour above the LEL transport velocity and prevent stratification.

The connection from the rigid hangar duct to the portable fuel tank extract fan is a quick-release flanged joint with a flexible conductive hose adapter. The hose is rated for 80 degrees Celsius continuous and 120 degrees Celsius intermittent, with internal carbon-loaded conductive lining and external chloride-resistant outer braid. The hose is replaced on a 12 month rolling schedule against ATA Spec 100 Chapter 28 maintenance requirements.

Aerospace paint booth Zone 1 isocyanate and chromate exposure control

The aerospace paint booth is the second-highest-risk HVAC environment in an aviation MRO facility after the fuel tank entry operation. Modern aerospace paint chemistry combines polyurethane topcoat (Sherwin-Williams Imron AVI, Akzo Nobel Awl-grip, PPG Desothane, Mankiewicz Alexit, ZEUS) with epoxy primer that is resistant to Skydrol hydraulic fluid attack. Both components contribute to operator exposure through different mechanisms.

The polyurethane topcoat catalyst includes toluene diisocyanate TDI and methylene diphenyl diisocyanate MDI at 0.005 ppm STEL — among the lowest WES values in any industrial process and a known severe occupational asthma trigger. Once an operator is sensitised to isocyanate, any subsequent exposure can trigger anaphylactic-grade asthma. Sensitisation is dose-independent above a threshold; some operators sensitise after a single exposure, others after years. There is no safe re-exposure level for a sensitised operator and the only effective control is to remove the operator from the booth permanently. The booth classifies as Zone 1 hazardous per AS/NZS 60079.10.1 with conducted-only spraying (no electrostatic except dedicated systems with full hazardous area certification). Supply air enters the booth ceiling at 0.4 to 0.5 m/s downdraft velocity, exhaust velocity exceeds 8 m/s in the extract duct, supplied-air respirators are mandatory for the spray operator and continuous TDI/MDI monitoring at the operator breathing zone tracks against the WES limit.

Booth ductwork material is 316L stainless 1.5 mm gauge with full continuous TIG welding. The SBSF-1525 stitchwelder produces the longitudinal seams and circumferential joints with auto-stitch tacking, followed by manual TIG full penetration pass for any joint that holds isocyanate-laden exhaust. Any porosity or pinhole in the duct wall releases isocyanate vapour into the hangar atmosphere where sensitised operators may already be present. The SBAL-V 316L variant fabricates the rectangular supply and return sections at 0.025 m squared minimum face area, and the SBFB-1500 spiral former produces the 250 to 1,500 mm round connection duct to the carbon adsorber or regenerative thermal oxidiser RTO. SMACNA leakage class 6 (under 1% leakage at 1,000 Pa) is the minimum acceptable seal class — typical paint booth specifications target class A seal (under 0.5% leakage) for isocyanate containment.

Pre-paint surface preparation introduces a second exposure concern. Chromate conversion coating using Iridite or Alodine 1200 deposits a 0.5 to 2 micron Cr VI passivation layer on aluminium aircraft skin (2024, 7075, 6061 alloy) before paint application. The Cr VI hexavalent chromium WES is 0.05 mg/m cubed STEL — IARC Group 1 carcinogen, the killer exposure for any aerospace surface treatment shop. The treatment bath operates at ambient with acidic spray application or dip immersion, generating Cr VI aerosol at 50 to 500 microgram per m cubed in the extract stream. Duct material is 316L stainless 1.5 mm with full continuous welding because any porosity releases Cr VI directly into the hangar atmosphere where operators are exposed.

Australian defence and commercial aerospace are progressively phasing chromate conversion to non-chromate alternatives — Sulfuric Acid Anodise SAA, Tartaric Sulfuric Anodise TSA, and Boric Sulfuric Acid Anodise BSAA. These alternatives provide the corrosion protection without the Cr VI exposure but require different bath chemistry and operating conditions. The duct material for SAA, TSA and BSAA processes can step down to 304L stainless because chromate is absent, but most operators specify 316L throughout the surface treatment shop for legacy compatibility. Legacy F/A-18A Classic Hornet, Hawk MK127 lead-in fighter trainer, F-35A external panel touch-up and C-130 spare component repair lines at BAE Systems Williamtown and Boeing Defence Australia Amberley still run chromate processes alongside the non-chromate replacement bath.

Beyond isocyanate and Cr VI, the paint booth extract carries a complex VOC mix. MEK methyl ethyl ketone at 200 ppm WES, toluene at 50 ppm, xylene at 50 ppm, MIBK methyl isobutyl ketone at 50 ppm, methylene chloride DCM at 50 ppm (where legacy stripper stock remains — DCM is now banned in Australia from 2023), benzyl alcohol and phenol for the modern biodegradable stripper, and general VOC at total 1,000 to 5,000 ppmv depending on application loading. The VOC abatement strategy is typically a regenerative thermal oxidiser RTO operating at 760 to 870 degrees Celsius with 95 to 99% destruction efficiency, achieving the EPA Victoria stack discharge limit of 50 mg/Nm cubed. The connection duct from the booth to the RTO is sized for 5 to 10 m/s velocity in 316L stainless at 1.5 to 2.0 mm gauge.

Composite repair carbon fibre dust capture and autoclave cure ductwork

Aerospace composite repair generates respirable dust during sanding, drilling and machining of cured CFRP carbon fibre reinforced plastic, AFRP aramid Kevlar and GFRP glass fibre composite components. The work spans Quickstep Composites Bankstown for F-35A vertical tail and horizontal stabilizer plus Boeing C-130 spare component manufacture, Boeing Aerostructures Australia Fishermans Bend for Boeing 787 Dreamliner wing flap, aileron and spoiler plus 777X and 737 MAX carbon composite work, Marand Precision Engineering Melbourne and Adelaide for Boeing and Lockheed Martin composite assembly, Marathon Targets for target drone composite construction, and Insitu Pacific Brisbane for ScanEagle UAV composite airframe work.

Respirable dust WES is 5 mg/m cubed for unspecified composite dust and 1 mg/m cubed where the resin contains formaldehyde from PF phenol-formaldehyde or PRF phenol-resorcinol-formaldehyde composite resin. Operator exposure is acute during sanding of cured composite to reshape a repair patch or to remove damaged material before laying up a new patch. Carbon fibre dust is conductive and can short-circuit avionics in adjacent bays if not properly contained. Aramid Kevlar dust forms long fibrous filaments that are less respirable but cause skin irritation and itching. Glass fibre dust generates the classic respiratory irritation and ear-nose-throat sensitivity. Composite resin during layup carries formaldehyde at 1 ppm STEL and epoxy resin sensitisers that cause allergic contact dermatitis CR (allergic dermatitis).

Capture is at the source with downdraft sanding tables at 0.5 to 0.7 m/s face velocity or local exhaust ventilation LEV arms at 30 to 50 m cubed per hour each, ducted to a HEPA-filtered cyclone or bag house. The cyclone removes the bulk of the fibre and the HEPA bag house captures the respirable fraction. Discharge to atmosphere is at 1 mg/m cubed maximum after the HEPA filter to meet EPA Victoria permit conditions.

Duct material is 316L stainless 1.2 to 1.5 mm gauge with conductive bonding throughout. The 316L specification reflects the chloride content of some composite cleaning solvents and the long service life expected at fixed sanding tables in continuous production. Conductive bonding is mandatory because dry carbon fibre dust is electrically conductive, and electrostatic charge accumulation in the duct can ignite resin vapour or trigger an avionics ESD event in an adjacent bay. SBFB-1500 spiral former produces the 250 to 1,500 mm round duct at SMACNA leakage class 6 and integrated conductive earthing terminals are mandatory at every 6 m of run. Conductive bonding is achieved by spot welding a 25 mm copper braid pigtail across every flanged joint, with the entire duct system earthed to building structural steel.

Autoclave cure for composite consolidation runs at 180 to 200 degrees Celsius and 7 bar nitrogen pressure for 2 to 4 hours per cure cycle. The autoclave itself is a pressure vessel rated to AS 1210 and AS 4458, and the HVAC ductwork serves the autoclave room ventilation rather than the autoclave interior. The room runs 6 to 10 air changes per hour with conditioned supply at 22 plus or minus 2 degrees Celsius and 50 to 60% RH. Exhaust captures any nitrogen vent during depressurisation (which can asphyxiate the autoclave operator if not adequately diluted) and any resin off-gas during the cure cycle. Duct material is galvanised 1.2 mm for the general room supply and exhaust, stepping up to 316L stainless 1.5 mm for the autoclave vent connection where direct exposure to nitrogen depressurisation and resin off-gas occurs.

Jet engine test cell 600 C exhaust ductwork and acoustic tunnel

Jet engine test cells run the highest-temperature exhaust ductwork in any aviation MRO facility, and arguably the highest-temperature in any industrial sector outside of steel making and aluminium smelting. TAE Aerospace Adelaide and Tindal RAAF operate test cells for GE F404 fighter engine, T56 turboprop and TF34 platforms. Pratt and Whitney, Rolls-Royce, GE Aerospace, CFM International, IAE V2500 and Honeywell engines pass through partner facilities for overhaul and run-up testing. The LM2500 marine derivative engine is tested at adjacent industrial test cells for naval propulsion qualification.

NFPA 423 is the governing standard for jet engine test cell design. The test cell is a bullet-shaped acoustic tunnel absorbing 50 to 130 dB of engine noise across the audible frequency range. A 4 to 6 metre diameter inlet at the bell mouth admits bypass air to mix with engine exhaust, sound attenuators line the tunnel walls and the augmenter section downstream of the engine accommodates the high-velocity high-temperature exhaust plume. The exhaust gas leaves the engine turbine at 600 to 800 degrees Celsius, mixes with bypass air through the augmenter and exits the stack at 200 to 400 degrees Celsius after augmenter cooling.

The augmenter section duct material is 309S or 310S stainless at 3 to 6 mm wall thickness. 309S contains 22 to 25% chromium and 12 to 15% nickel, with elevated carbon content giving resistance to 800 degree Celsius continuous service. 310S contains 24 to 26% chromium and 19 to 22% nickel for service up to 1,150 degrees Celsius intermittent. Both grades are cut on heavy-gauge plasma equipment because the wall thickness exceeds the capability of shear cutting. SBPC1500 plasma table cuts 309S and 310S at 0.8 to 2.5 m per minute travel speed depending on plate thickness, with high-tolerance edge preparation suitable for welded joint preparation. The cut sections are then formed on the SBSF-1525 stitchwelder with the heavy-gauge roll set. Longitudinal seam stitch welding on the SBSF-1525 provides initial tacking followed by manual TIG full penetration pass with 309S filler rod for chemical compatibility. Every joint is verified with dye penetrant inspection DPI and the finished duct is pressure tested at 1.5 times design pressure for 30 minutes.

The exhaust stack section downstream of augmenter cooling drops to 304L stainless at 2 to 3 mm wall thickness because the temperature drops below 400 degrees Celsius. The SBSF-1525 stitchwelder produces this section with longitudinal seam construction and integrated TDF flanges. Thermal expansion at 400 degrees Celsius versus 20 degree Celsius ambient is significant — a 20 metre stack grows 88 mm linearly and bellows-style expansion joints are mandatory at every wall penetration and at every change of direction.

Concurrent fire suppression in the test cell uses N2 nitrogen or CO2 carbon dioxide deluge to prevent engine fuel fire propagation. Halon 1301 was the legacy suppression agent until international phase-out, with current systems using CEA-410 fluorinated agent or N2 inert gas as the replacement. Atomised jet fuel is present continuously during testing, so any inadvertent ignition can propagate through the augmenter and ignite the test cell interior. Continuous fuel-air ratio monitoring shuts the cell on any deviation outside the operating envelope.

The test cell ventilation system serves two functions. First, conditioned make-up air is supplied to the test cell control room and operator booth at 22 plus or minus 2 degrees Celsius and 50 to 60% RH for operator comfort during a 4 to 8 hour test run. Second, exhaust from the augmenter cooling section discharges to atmosphere through a 30 to 50 metre tall stack with diffuser at the discharge point to manage acoustic emissions. Make-up air supply is in galvanised at 1.2 to 1.6 mm gauge on the SBAL-V galvanised configuration. The augmenter exhaust is in 309S/310S at 3 to 6 mm gauge as above.

Avionics bay ESD-controlled clean air and ASHRAE TC 9.9 Class A1 environment

The avionics bay is where the most sensitive aircraft electronics are tested, repaired and recertified. The F-35A APG-81 AESA active electronically scanned array radar, the E-7A Wedgetail Northrop Grumman MESA Multi-role Electronic Scanning Array, the P-8A Poseidon APY-10 radar, and the In-Flight Entertainment IFE systems for Qantas, Virgin and Jetstar fleets all pass through avionics bays during scheduled maintenance and unscheduled repair. BAE Systems Australia Mascot avionics shop and Lockheed Martin Avalon avionics facility are the principal Australian avionics facilities for defence platforms; the airline avionics bays at Qantas Mascot, Virgin Brisbane and Jetstar Tullamarine handle the commercial side.

The avionics bay environment matches ASHRAE TC 9.9 Class A1 specification — 22 to 27 degrees Celsius dry bulb temperature with 8 to 90% RH humidity range, but with tight humidity ramp control to prevent condensation on cold-soaked aircraft electronics. An avionics box arriving from a flight at minus 55 degrees Celsius cabin altitude and 0 to 5% cabin RH cannot be opened in a 50% RH room without condensing water inside the chassis, which would short-circuit any energised circuit. The standard approach is to ramp the avionics box through a controlled warm-up cycle inside an environmental cabinet for 30 to 60 minutes before opening, with the surrounding room held at 35 to 45% RH to limit the condensation potential during transit from cabinet to test bench.

ESD electrostatic discharge control is the second avionics bay requirement. The bay runs ESD-safe with conductive flooring (vinyl tile with embedded conductive grid to a measured surface resistance of 1 megohm to 1 gigohm), ionised supply air (passing through static-dissipative air-bar ionisers at the supply diffuser face), and continuous static field monitoring at every workstation. Any operator entering the bay must wear ESD-safe footwear and a heel-strap or wrist-strap connected to the conductive floor.

The HVAC duct designer faces three avionics-specific challenges. First — the supply air diffuser face cannot introduce dust particles above the ISO 8 cleanliness threshold (per ISO 14644-1, 3.52 million particles per cubic metre at 0.5 micron). The supply train is a three-stage filtration with F7 bag pre-filter, F9 fine filter, and H13 HEPA final stage at the supply diffuser. Second — the supply air cannot carry an electrostatic charge that defeats the room ESD control. Static-dissipative ionisers integrated into the supply diffuser neutralise any charge picked up during transport through the duct. Third — the supply air humidity must hold within plus or minus 5 percentage points RH against the room setpoint. This requires a precision humidity-controlled air handler with steam injection or ultrasonic humidifier on the supply side, and chilled-water cooling coil for dehumidification on summer days.

Duct material in the avionics bay is galvanised G90 (Z275) at 1.0 to 1.2 mm gauge for the supply and return, fabricated on the SBAL-V galvanised configuration with TDF flanges and SMACNA seal class A. The galvanised specification is acceptable because the bay environment is conditioned and not exposed to corrosive process exhaust. Internal duct surfaces must be smooth (no exposed fasteners or sharp edges that could generate dust through air friction) and the duct interior is cleaned with HEPA-filtered vacuum before commissioning.

Paint stripping and chemical deplaint Zone 1 booth ductwork

Aircraft paint stripping is performed during livery refresh and during heavy maintenance to expose the aluminium skin for corrosion inspection. The strip cycle is among the highest VOC processes in the facility, generating 200 to 1,500 ppmv VOC concentration plus paint debris particulate.

Modern paint stripper chemistry is benzyl alcohol or phenol or n-methyl pyrrolidone NMP biodegradable replacement. Tytan, Eldorado, Bonderite Greesoff and EnviroStrip are the dominant brands across Australian aerospace MRO. The chemistry replaced methylene chloride DCM which was banned in EU 2014 and Australia 2023. Some legacy facilities continue to hold residual DCM stock under controlled inventory management and the duct designer must specify chloride-resistant material to handle any inadvertent DCM exposure during the phase-out period.

The strip bath operates at 50 to 80 degrees Celsius with intermittent steam clean rinse. The bath generates high-VOC exhaust plus particulate paint debris that requires capture at the bath canopy hood. Duct material is 316L stainless 1.5 to 2.0 mm gauge for the canopy hood and 304L stainless 1.5 mm for the connection duct to the carbon adsorber or RTO. Pre-2023 facilities running residual DCM stock require 316L throughout because of chloride attack on 304L. SBAL-V 316L variant fabricates rectangular sections at 0.025 m squared minimum, and SBFB-1500 spiral former produces 250 to 1,500 mm round riser at SMACNA leakage class 6 — critical because paint stripper VOC exceeding 50 mg/Nm cubed at the stack triggers EPA Victoria permit breach.

Operator exposure during strip operations is managed through booth zone classification (Zone 1 per AS/NZS 60079.10.1 inside the booth, Zone 2 within 3 m of the open door), supplied-air respirators for any operator working inside the booth, and continuous LEL and VOC monitoring at the operator breathing zone. Benzyl alcohol WES is 50 ppm 8-hour TWA, phenol WES is 5 ppm STEL, NMP WES is 25 ppm 8-hour TWA. None of these exposures matches DCM at 50 ppm STEL and IARC 2A classification, but the cumulative occupational exposure across an 8-hour strip cycle still requires respiratory protection.

Hangar make-up air supply and smoke spill ductwork construction

Hangar make-up air supply is the largest single ductwork run in an aviation MRO facility. A Group I wide-body hangar at 100,000 m squared single-fire-area with 25 m clear height requires 4 ACH mechanical ventilation, giving a make-up airflow of 100,000 x 25 x 4 / 3600 = 2,800 m cubed per second total. Across an 8-hour working day this is 80 million m cubed of conditioned air, and the air handlers serving a single Group I hangar are among the largest single-building HVAC loads in Australian commercial infrastructure.

Smoke removal capacity rises to 6 ACH within 30 seconds of fire alarm activation, requiring dedicated smoke spill fans and ductwork separate from the general ventilation. The smoke spill system holds a 250 degree Celsius / 2 hour smoke spill rating per AS 1668.1 and AS 1530.4 fire resistance level. Smoke spill ducts are heavy-gauge construction in galvanised steel at 1.6 to 2.0 mm thickness, fabricated on the SBAL-V galvanised configuration with TDF flanges and continuous welded seams at any joint exceeding 1,500 Pa pressure class.

The make-up air supply duct is in galvanised G90 (Z275) at 1.2 to 1.6 mm gauge for the main trunk and 1.0 to 1.2 mm for the branch runs. SBAL-V galvanised configuration produces the rectangular sections at 8 to 15 m per minute production rate. SBTF spiral tubeformer handles the 600 to 2,500 mm round trunk duct that feeds the diffuser ceiling array. Diffuser face velocity is 1.5 to 2.5 m/s at the hangar ceiling, dropping to 0.5 to 1.0 m/s at the hangar floor by the time the air mass has cascaded through the 25 m of clear span. Supply air condition is 22 plus or minus 4 degrees Celsius dry bulb (the wider tolerance reflects the difficulty of conditioning such large volumes against summer 35 degree Celsius and winter 5 degree Celsius ambient at typical Australian capital city sites).

For the heavy-gauge ESFR sprinkler riser plus 250 C / 2 hr smoke spill (hangar fire) the duct designer specifies manual fabrication using SBSF-1525 stitchwelder for the longitudinal seams on galvanised plate at 2.0 to 3.0 mm gauge. The SBSF-1525 produces the seam tack and the manual finish pass provides full penetration weld for the high-temperature service. Joint construction is bolted flange with high-temperature gasket (ceramic fibre or asbestos-free silicate-based gasket rated for 300 degree Celsius continuous and 600 degree Celsius intermittent).

Round spiral ductwork for composite dust and grinding extraction

The SBFB-1500 spiral former is the SBKJ workhorse for round duct fabrication in aviation MRO. Composite carbon dust extract, fuel tank vent, engine bleed-air vent, paint booth supply riser and return air trunk all use round spiral construction because the leakage performance is superior to rectangular at any given pressure class, and the structural strength against external impact (forklift, tow tractor) is also better in the round geometry.

The SBFB-1500 handles 250 to 1,500 mm diameter at 0.6 to 2.0 mm wall thickness across galvanised, aluminium and 316L stainless coil. Production rate is 12 to 25 metres of finished spiral per minute depending on diameter and wall thickness. SMACNA leakage class 6 (under 1% leakage at 1,000 Pa) is the standard performance, with class A (under 0.5% leakage) achievable through specific seam roll setup and additional sealant application at the spiral seam.

For composite dust extract the duct is 316L stainless at 1.2 to 1.5 mm gauge with conductive bonding terminals every 6 m of run. The bonding is achieved by spot welding a 25 mm copper braid pigtail across every flanged joint with the entire duct system earthed to building structural steel at the fan housing and at every wall penetration. Internal duct surfaces are smooth and continuous without exposed seams that could catch fibre deposits.

For paint booth supply riser the duct is 316L stainless at 1.0 to 1.2 mm gauge. The smooth internal surface prevents dust pickup from the supply air stream as it transports from the air handler to the booth ceiling diffuser array. Connection to the booth ceiling uses a rectangular-to-round transition piece fabricated separately on the SBAL-V and welded into the spiral riser.

For hangar make-up air return duct the duct is galvanised at 1.0 to 1.2 mm gauge. The lower-cost galvanised is acceptable because the return air is not contaminated by process exhaust (process exhaust is captured at the source and exhausted through a dedicated stack). Galvanised return duct provides 20 year service life at lower capital cost than stainless equivalent.

Heavy gauge engine test cell exhaust 309S and 310S stainless ductwork

The engine test cell augmenter section is among the most demanding fabrication challenges in any HVAC duct manufacturing environment. The combination of high temperature (600 to 800 degrees Celsius at peak), high pressure (1.5 to 2.5 bar gauge during full augmenter operation), corrosive exhaust gas chemistry (sulphur oxides, nitrogen oxides, carbon monoxide, water vapour at saturation), and acoustic loading (130 dB peak inside the tunnel) demands the heaviest gauge stainless ductwork in any non-process-industry application.

Duct material is 309S or 310S stainless at 3 to 6 mm wall thickness. 309S contains 22 to 25% chromium and 12 to 15% nickel, with elevated carbon content (0.08% maximum) for resistance to 800 degree Celsius continuous service. 310S contains 24 to 26% chromium and 19 to 22% nickel for service up to 1,150 degrees Celsius intermittent. Both grades resist scaling and oxidation at high temperature and maintain mechanical strength against the pressure load.

SBPC1500 plasma cutting table cuts 309S and 310S at 0.8 to 2.5 metres per minute travel speed depending on plate thickness. Plasma cutting is selected over shear cutting because the wall thickness exceeds shear capability. Plasma cuts maintain dimensional tolerance within plus or minus 1 mm across the cut length and provide a clean edge suitable for direct welding without subsequent edge preparation. The SBPC1500 is also used for plate notching, cutout work and edge preparation on heavy-gauge ducts up to 12 mm thick.

The cut plates are formed into cylindrical sections on the SBSF-1525 stitchwelder with the heavy-gauge roll set. The stitchwelder applies longitudinal seam tack welding with 309S filler rod at 0.5 to 1.5 m per minute weld speed. The stitch weld provides initial joint integrity; the manual TIG finish pass provides full penetration weld for the high-temperature service. Manual TIG is required because the seam weld must hold full mechanical strength at 800 degree Celsius continuous, where any porosity or incomplete fusion would propagate as a crack under thermal cycling and pressure loading.

Joint construction at the augmenter section is bolted flange with metal-clad ceramic fibre gasket rated for 600 degree Celsius continuous. Flange bolting is high-temperature alloy (A286 or Inconel 718) with appropriate thermal expansion allowance built into the bolt-up procedure. Cold pre-load on a hot flange must account for differential thermal expansion between the bolt and the flange to prevent stress relaxation at high temperature.

Every joint is verified with dye penetrant inspection DPI per AS 3978 weld inspection standard, and the finished duct is pressure tested at 1.5 times design pressure for 30 minutes before commissioning. Pressure test is performed at ambient temperature with the duct supported in its installed orientation. Following pressure test, the duct is heat-cycled through a controlled ramp from ambient to 800 degree Celsius operating temperature with thermocouples on every joint to verify thermal expansion and detect any post-fabrication weld failure.

Australian aviation MRO operators and the duct market

Australia hosts a substantial aviation MRO sector across commercial airlines, defence depot and component overhaul. Understanding the operator landscape is important context for any duct fabrication procurement decision because the operators drive the specification standards and the cycle time targets.

Qantas Engineering is the largest single MRO operator in the country, with bays at Sydney Mascot, Brisbane, Melbourne, Cairns and Perth. The Mascot Sydney facility holds wide-body D-check capability for the Boeing 787 Dreamliner and the residual A380 fleet. Brisbane handles wide-body and narrow-body intermediate maintenance. Melbourne, Cairns and Perth handle line maintenance and light overhaul. Qantas Group is ASX-listed under code QAN and is Australia's largest airline MRO by a wide margin.

Jetstar Engineering operates from Melbourne Tullamarine VIC, supporting the Jetstar narrow-body fleet (A320 family, 787 long-haul). The Tullamarine facility runs a Group II hangar suitable for narrow-body line maintenance.

Virgin Australia Engineering operates from Brisbane, Sydney and Melbourne with line and intermediate maintenance capability for the 737 narrow-body fleet and the legacy ATR turboprop on the Virgin Australia Regional Airlines operation.

Rex Engineering at Wagga Wagga NSW supports the Saab 340 regional turboprop fleet that Rex operates across the eastern Australian regional network. The Wagga Wagga facility is a Group III hangar with line and intermediate maintenance capability.

Boeing Australia spans three entities — Boeing Defence Australia at Brisbane for E-7A Wedgetail, C-17A Globemaster III, P-8A Poseidon and F/A-18F Super Hornet support; Boeing Aerostructures Australia at Fishermans Bend VIC for Boeing 787 Dreamliner wing flap, aileron and spoiler carbon composite plus 777X and 737 MAX work; and Insitu Pacific Brisbane (Boeing-owned) for ScanEagle UAV composite airframe.

Airbus Group Australia Pacific at Sydney and Brisbane handles Airbus Helicopters Australia Pacific commercial helicopter support and Airbus commercial aircraft support across the Australian network.

Sikorsky Helitech at Brisbane handles the Sikorsky helicopter range including the MH-60R Romeo Seahawk Australian Navy maritime helicopter.

BAE Systems Australia spans three principal sites — Williamtown NSW for RAAF Royal Australian Air Force MRO across the Hawk MK127 lead-in fighter trainer, the F/A-18A/B/C/D Classic Hornet legacy fleet during phase-out and the F-35A Lightning II in-service support; Hobart TAS for naval shipbuilding; and Mascot Sydney for avionics shop work.

Lockheed Martin Australia operates from Melbourne, Avalon and Williamtown for F-35A support, training and depot maintenance. The Australian F-35A fleet is contracted to 72+ airframes, making Lockheed Martin Australia the principal F-35A depot in the southern hemisphere. The Avalon avionics facility supports the F-35A AESA radar and electronic warfare suite.

TAE Aerospace at Adelaide and Tindal RAAF performs engine overhaul on GE F404, T56 and TF34 platforms across RAAF and partner air forces. The Adelaide and Tindal test cells are the principal jet engine test capability in Australia outside of Boeing Defence Australia at Brisbane.

Hawker Pacific (now part of Jet Aviation) handles corporate jet MRO at Sydney, Melbourne and Cairns. The corporate jet MRO sector supports Cessna Citation, Gulfstream, Bombardier and Embraer business jets across the Australian and southwest Pacific operator base.

Other operators include Toll Aviation for helicopter and small aircraft MRO across the Toll Group fleet, Rossi Aviation at Coffs Harbour for regional MRO, Pearce Aviation at Esperance WA for general aviation, Avwest at Cairns for turbine engine work, Pel-Air Aviation as the Royal Flying Doctor Service contractor, Skywest (now part of Qantas Group as Eastern Australian Airlines) for regional turboprop, GippsAero at Latrobe VIC for the indigenous GA8 Airvan and GA10 light aircraft, CD Aviation, Becker Helicopters and Helicopter Industries for general aviation light aircraft work.

RAAF bases hosting depot and squadron MRO include Williamtown NSW for air combat F-35A and Hawk, Tindal NT for F-35A and engine test, Amberley QLD for F-35A, C-17A, E-7A and KC-30A, Edinburgh SA for P-8A and AP-3C Orion, Pearce WA for training fleet, Richmond NSW for C-130J Hercules and East Sale VIC for training fleet and basic flying training.

Civilian airport MRO capability sits at Sydney Kingsford Smith YSSY, Melbourne Tullamarine YMML, Brisbane YBBN, Perth YPPH, Adelaide YPAD, Cairns YBCS, Darwin YPDN, Avalon YMAV, Bankstown YSBK, Essendon YMEN, Moorabbin YMMB and Archerfield YBAF. The major airline MRO bases are at the capital city airports; the corporate, charter and general aviation MRO bases are at the secondary airports.

Codes and standards — the aviation MRO regulatory stack

No aviation MRO HVAC design is complete without explicit verification against the regulatory stack. The standards below are the primary references; in any given project at least eight apply and on a defence depot facility often fifteen apply.

NFPA 409 — Standard on Aircraft Hangars. The governing reference for hangar fire protection globally. Chapter 4 defines hangar group classification, chapter 5 covers fire protection requirements (high-expansion foam, ESFR sprinkler, hangar floor drainage), chapter 6 covers ventilation (4 ACH minimum, 6 ACH smoke removal within 30 seconds), chapter 7 covers fuel storage and handling within the hangar, and chapter 8 covers building services. NFPA 409 is referenced by every Australian aviation MRO insurance underwriter as the design basis for hangar fire protection.

NFPA 410 — Standard on Aircraft Maintenance. Governs maintenance operations inside the hangar including hot work, paint application, paint stripping and fuel system work. Cross-references NFPA 409 for hangar construction and NFPA 30 for flammable liquid storage.

NFPA 415 — Standard on Aircraft Fuel Servicing Ramps, Drainage and Loading Walkways. Governs the fuel servicing ramp adjacent to the hangar where aircraft are refuelled. Drainage and spill containment provisions apply to the ramp surface and to any ductwork penetration of the ramp area.

NFPA 416 — Standard on Aircraft Fueling Truck. Governs the truck-mounted refueller equipment. Less directly relevant to hangar HVAC but referenced in the overall fuel servicing operation.

NFPA 418 — Standard for Heliports. Governs helicopter operations and heliport construction. Relevant to Sikorsky Helitech Brisbane and Airbus Helicopters Australia Pacific facilities where helicopter MRO is concurrent with helicopter operation.

NFPA 423 — Standard for Construction and Protection of Aircraft Engine Test Facilities. Governs jet engine test cell design including the acoustic tunnel, augmenter section, exhaust stack, fuel servicing, suppression and ventilation. The reference standard for any test cell duct design.

NFPA 86 — Standard for Ovens and Furnaces. Governs paint bake oven at 180 degrees Celsius for powder coat and 60 to 80 degrees for clear coat, and autoclave composite cure at 180 to 200 degrees Celsius and 7 bar nitrogen pressure. Mandates pre-purge cycle, flame supervision, high-temperature limit and explosion relief.

NFPA 30 — Flammable and Combustible Liquids Code. Governs jet fuel storage, hydraulic fluid storage and lube oil storage within and adjacent to the hangar. Sets minimum separation distances, ventilation requirements and electrical classification for storage areas.

NFPA 13 — Sprinkler Systems and NFPA 14 — Standpipe Systems and NFPA 70 NEC — National Electrical Code and NFPA 75 — IT Equipment provide the foundation building services references for hangar and avionics bay design.

NFPA 654 — Combustible Dust. Governs the paint flat dry powder coat area where paint solids and overspray accumulation create combustible dust hazard. Cross-references NFPA 409 for hangar floor accumulation.

AS 1668.2 — The use of ventilation and air-conditioning in buildings, mechanical ventilation in buildings. Section 4 sets the ventilation rate for aircraft hangar floor area at 4 ACH minimum, aligning with NFPA 409 chapter 6. Section 6 governs commercial kitchen and other process exhaust which extends to paint stripping and chemical cleaning bays.

AS 1668.1 — The use of ventilation and air-conditioning in buildings, fire and smoke control. Section 5 covers smoke spill system design at 250 degrees Celsius / 2 hour smoke spill rating. Section 6 covers fan and duct construction for smoke spill service. Section 7 covers fan rating at F300/120 for 300 degree Celsius operation over 120 minutes.

AS 4254 — Ductwork for air-handling systems in buildings. Parts 1 and 2 cover flexible duct and rigid duct construction respectively. The principal Australian reference for SMACNA-equivalent duct construction standards.

AS 1530.4 — Fire resistance tests for elements of construction. Sets the test method for verifying smoke spill duct fire resistance at 250 degrees Celsius / 2 hour and equivalent ratings.

AS 1851 — Routine service of fire protection systems and equipment. Governs the periodic service schedule for fire dampers, smoke dampers, smoke spill fans and other fire safety equipment connected to the duct system.

AS/NZS 60079.10.1 — Explosive atmospheres, Part 10.1: Classification of areas — Explosive gas atmospheres. The Australian implementation of IEC 60079.10.1, governing hazardous area zoning across the entire aviation MRO facility. Cross-referenced by AS/NZS 60079.14 for installation and AS/NZS 60079.17 for inspection.

AS 1940 — The storage and handling of flammable and combustible liquids. Australian equivalent of NFPA 30, covering jet fuel, hydraulic fluid and lube oil storage within and adjacent to the hangar.

AS 4332 — The storage and handling of gases in cylinders. Governs specialty gas storage for oxygen, nitrogen, argon, helium and hydrogen used in aircraft service operations.

AS/NZS 1596 — The storage and handling of LP Gas. Rarely relevant in aviation MRO because the principal flammable fuel is diesel for ground support equipment and jet fuel for aircraft. LPG appears only in legacy applications.

AS 3957 — Walls and ceilings — solid plasterboard linings. Governs the construction of the fire compartment walls separating the hangar from adjacent process zones (paint bay, composite shop, avionics bay).

AS 3000 — Electrical installations (Wiring Rules). The Australian wiring rules covering electrical installation across all building services including the duct system actuators and control wiring.

AS/NZS 3008 — Electrical installations — Selection of cables. Governs cable selection for high-temperature service in the smoke spill duct and avionics bay control wiring.

MIL-STD-1553 — Aircraft Internal Time Division Command/Response Multiplex Data Bus. The avionics communication standard relevant to F-35A, E-7A and P-8A platform support.

DEF (Aust) 5613 — RAAF Technical Airworthiness Regulations. The Royal Australian Air Force technical airworthiness framework that overlays defence aviation MRO requirements on top of the civil CASA framework. Applied to F-35A, F/A-18A Classic Hornet legacy support, Hawk MK127, C-17A, E-7A, P-8A and AP-3C support.

MIL-PRF-83282 — Hydraulic Fluid, Fire-Resistant Synthetic Hydrocarbon Base. The U.S. military specification for synthetic hydrocarbon hydraulic fluid used in defence aviation platforms. Cross-recognised by Australian RAAF maintenance procedures.

CASA Civil Aviation Safety Authority Civil Aviation Regulations CAR and Civil Aviation Safety Regulations CASR govern commercial aviation MRO across Australia. EASA and FAA cross-recognition applies to commercial component overhaul that may be installed on European or US-registered aircraft.

IATA Australia represents the Australian airline operator interest in international IATA standards including aircraft handling, ground support and MRO interface.

RAAFI Royal Australian Air Force Institute of Aviation Engineering provides the professional engineering body for RAAF aviation engineering officers and technical airworthiness assessors.

ICAO International Civil Aviation Organization sets the international civil aviation framework that Australia adopts through CASA implementing regulations.

Industry bodies and ARBS 2026 attendance

Several industry bodies shape the Australian aviation MRO HVAC landscape. The Aviation/Aerospace and Defence Industries Association of Australia AIAA represents the federal aviation and aerospace industry. The Australian Airports Association AAA represents the airport operator interest including hangar facility owners. The Institute of Aeronautical Engineers IAE within Engineers Australia provides the professional engineering body for aeronautical engineers. The Australian Council of Aviation Engineering ACAE provides cross-sector representation. CASA Civil Aviation Safety Authority is the federal regulator. Airservices Australia provides air traffic services. The Royal Australian Air Force RAAF and the Capability Acquisition and Sustainment Group CASG (formerly DMO Defence Materiel Organisation) drive defence aviation procurement. The Defence Aviation Safety Authority DASA provides the technical airworthiness regulator function for defence platforms. Defence Industries Australia DIA represents the broader defence industry. Aerospace Engineering Australia AEA, Aerospace Industry Association AIA (federal) and the Australia Aviation Network provide additional sector representation.

SBKJ Group will be at ARBS 2026 in Sydney through May 12-14 2026 with our SBAL-V auto duct line, SBFB-1500 spiral former and SBSF-1525 stitchwelder on the stand for live demonstration. Our application engineering team will be available for project scoping discussions on aviation MRO ductwork, hangar fit-out, paint booth integration, composite repair extract and engine test cell exhaust ductwork. Booking a 30-minute slot in advance through our contact page guarantees a dedicated session with a senior engineer.

SBKJ machinery sized for aviation MRO ductwork projects

SBKJ duct fabrication machinery covers the full range of aviation MRO ductwork requirements, from regional turboprop line maintenance hangar through to wide-body heavy maintenance bay and defence depot engine test cell. Seven SBKJ machine families are sized and configured for aviation MRO applications.

SBAL-V auto duct line for galvanised hangar make-up air. Our flagship rectangular duct line, configured for aviation MRO projects with G90 (Z275) galvanised coil at 1.2 to 1.6 mm gauge. Cuts, notches, folds, seams and TDF flanges in a single integrated pass at 8 to 15 m per minute line speed depending on duct size. SMACNA, AS/NZS 4254 and EN 1505 pressure-class compliant. Single-shift output 600 to 900 m of duct per shift on typical hangar make-up sizes (600 to 1,500 mm). Configured for the smoke spill spec at 1.6 to 2.0 mm gauge with continuous welded seams at any joint exceeding 1,500 Pa pressure class. SBAL-V auto duct line specification.

SBAL-V 316L stainless variant for paint booth and process exhaust. A reinforced-roll variant of the SBAL-V optimised for 316L stainless coil at 1.2 to 2.0 mm gauge. 316L-specific tooling (TDF flange dies hardened for stainless work-hardening), upgraded forming pressure to handle 316L yield strength of 485 MPa, and corrosion-resistant guideways. Single-shift output 350 to 500 m on 316L duct, lower than the galvanised variant because of slower forming speeds and the manual TIG finish pass required for isocyanate and Cr VI containment. The standard machine for aerospace paint booth supply and exhaust, paint stripping bath canopy hood, Cr VI chromate conversion bath extract and fuel tank vent ductwork.

SBAL-III auto duct line for medium-duty rectangular work. An economy-tier rectangular duct line for low-pressure-class supply and return duct in office, control room and operator amenity zones within the aviation MRO facility. Galvanised 0.6 to 1.2 mm gauge with TDF flanges suitable for SMACNA pressure class 1,000 Pa.

SBSF-1525 stitchwelder for longitudinal seam welded riser pipe. Heavy-gauge longitudinal seam welding capability for 304L, 309S, 310S and 316L stainless at 2 to 6 mm wall thickness. Single-pass auto-stitch tacking followed by manual TIG full penetration finish. The standard machine for engine test cell augmenter exhaust at 309S/310S 3-6 mm and for paint booth manual fabrication runs where the SBAL-V cannot handle the specific geometry.

SB-ZF1500 stitchwelder for medium-gauge riser pipe. A lighter-duty variant of the SBSF-1525 for stainless riser pipe at 1.5 to 3.0 mm wall. Suitable for paint booth exhaust riser, fuel tank vent rigid duct and composite extract riser. Single-pass production rate 2 to 4 m per minute depending on diameter and wall thickness.

SBFB-1500 spiral former for round composite extract and process duct. Round-duct fabrication for composite dust extract, fuel tank vent, engine bleed-air vent, paint booth supply riser and return air trunk. 250 to 1,500 mm diameter range covers everything from local exhaust ventilation arm through to main process exhaust riser. Spiral seam construction reduces leakage to under 1% at 1,000 Pa for SMACNA leakage class 6 — important for VOC-laden exhaust where any leakage emits regulated emissions or for Cr VI extract where any leakage releases IARC 1 carcinogen aerosol. Integrated conductive bonding terminals every 6 m of run for composite dust service. SBFB-1500 spiral former specification.

SBPC1500 plasma cutting table for heavy-gauge stainless. Heavy-plate plasma cutting for 309S/310S engine test cell augmenter at 3 to 6 mm and for any plate notching, cutout work and edge preparation on heavy-gauge ducts up to 12 mm thick. Plasma cuts maintain dimensional tolerance within plus or minus 1 mm across the cut length and provide a clean edge suitable for direct welding without subsequent edge preparation.

SBLR-600 laser cutting table for precision sheet metal. Fibre laser cutting capability for precision rectangular duct accessory fabrication — access doors, inspection ports, instrumentation penetrations, transition fittings and custom geometry. Cuts galvanised, stainless and aluminium up to 6 mm at high tolerance suitable for HVAC accessory work.

SBTF-1500 / SBTF-1602 / SBTF-2020 spiral tubeformers. The SBTF series handles the largest-diameter round duct in the aviation MRO market — up to 2,500 mm for hangar make-up air return trunk and for the main supply ducts feeding the ceiling diffuser array. The SBTF-1500 covers 250 to 1,500 mm, SBTF-1602 covers 250 to 1,600 mm, and SBTF-2020 covers 400 to 2,000 mm. All three models hit SMACNA leakage class 6 at standard setup and class A with additional sealant application.

Lead time on SBAL-V galvanised configuration is 12 to 14 weeks from purchase order to factory acceptance test. 316L stainless variant adds 2 weeks (14 to 16 weeks total). SBFB-1500 spiral former is 10 to 12 weeks. SBSF-1525 stitchwelder is 12 to 14 weeks. SBPC1500 plasma table is 8 to 10 weeks. Add 4 to 6 weeks ocean freight to Australian ports and 1 to 2 weeks for installation, mechanical commissioning and operator training by SBKJ engineers on site from our Box Hill North VIC service base.

Operator exposure monitoring and WES compliance

Operator exposure across an aviation MRO facility spans the most demanding mix in any industrial sector. The duct designer specifies the ductwork against the WES (workplace exposure standard) values that the WorkSafe regulator audits against. The list below covers the principal exposures and the WES values that apply.

Jet fuel JP-8 and AVTUR Jet A-1 at 200 ppm kerosene total, with naphthalene at 10 ppm and benzene at 1 ppm STEL as the killer exposure. AVGAS 100LL at the same base limits plus tetraethyl lead 0.05 mg/m cubed STEL. Hydraulic fluid Skydrol LD-4 (phosphate ester, skin irritant and dermatitis sensitiser) and Mil-PRF-83282 (synthetic hydrocarbon). Turbine engine oil Mobil Jet Oil II and Mil-PRF-23699 synthetic polyol ester POE with tricresyl phosphate TCP neurotoxin in heat decomposition products. Paint stripper benzyl alcohol, phenol or NMP biodegradable replacement with WES 50, 5 and 25 ppm respectively. Methylene chloride DCM at 50 ppm STEL (now banned but residual stock concerns). VOC general at 200 to 1,500 ppmv during spray application. MEK methyl ethyl ketone at 200 ppm STEL, MIBK at 50 ppm, toluene at 50 ppm, xylene at 50 ppm. Isocyanate TDI/MDI at 0.005 ppm STEL — the killer exposure for any sensitised operator. Epoxy resin as a skin sensitiser with no quantitative WES but workplace controls applied. Formaldehyde at 1 ppm STEL for phenolic composite resin. Cr VI hexavalent chromium at 0.05 mg/m cubed STEL — IARC Group 1, the killer exposure for surface treatment operations. Cd cadmium at 0.01 mg/m cubed STEL — IARC Group 1 for legacy plated landing gear parts. Be beryllium at 0.001 mg/m cubed STEL — extremely small but critical for copper-beryllium alloy connector and reflector work. N2 nitrogen at oxygen 19.5 to 23.5% by volume as the lower and upper limits for asphyxiation and oxygen enrichment respectively. O2 oxygen at 23.5% maximum enrichment for medical and emergency life support service. Composite carbon fibre dust at 5 mg/m cubed respirable. Aramid Kevlar dust and glass fibre composite dust. R32, R454B and R744 refrigerants for the air conditioning system serving the avionics bay and operator amenity zones. CO carbon monoxide at 30 ppm 8-hour TWA for the engine test cell exhaust environment and LPG furnace. HF hydrogen fluoride at 1.8 ppm STEL for lithium-ion battery off-gas and aluminium alloy etch. HCl hydrochloric acid at 5 ppm STEL for aluminium etch and pre-paint surface preparation. O3 ozone at 0.1 ppm STEL for UV cure equipment, corona treatment and ozone-depleting refrigerant. Particulate respirable dust at 5 mg/m cubed for sanding, grinding and composite repair operations.

Operator-breathing-zone monitoring is continuous in the highest-risk zones — fuel tank entry (jet fuel and benzene), paint booth (isocyanate TDI/MDI), pre-paint surface prep (Cr VI), composite repair (respirable dust and formaldehyde) and engine test cell (CO and particulate). The monitoring data feeds the duct designer's verification that the extract system delivers the required capture efficiency at the source.

Maintenance regime and as-built documentation

The aviation MRO duct system requires a structured maintenance regime to maintain compliance against the regulatory stack. The maintenance schedule typically includes monthly visual inspection of all hangar floor duct penetrations and damper positions, quarterly cleaning of paint booth exhaust ducts (paint deposit buildup is a fire risk and an airflow restriction), semi-annual inspection of smoke spill fans and dampers per AS 1851, annual hazardous area inspection per AS/NZS 60079.17 of all electrical equipment penetrating the duct, annual pressure test of the engine test cell augmenter ductwork at 1.5 times design pressure, quarterly verification of composite extract HEPA filter integrity and pressure drop, annual recertification of the avionics bay supply train HEPA filters at H13 99.95% efficiency, and continuous monitoring of operator-breathing-zone exposure across all high-risk zones.

The as-built documentation chain is the deepest in any industrial HVAC project. Welder qualification per AS 3992 weld procedure qualification, weld procedure specification WPS records per AS 3978, dye penetrant inspection DPI records per AS 2452, pressure test certificates per the project pressure test procedure, hazardous area certification chain per AS/NZS 60079.14 with IECEx certificates for all penetrating electrical equipment, fire damper certification per AS 1530.4 fire resistance testing, smoke spill fan certification at F300/120 per AS 1668.1, and ductwork balance certification per AS/NZS 5443. The complete documentation package is held by the operator for the life of the facility and surrendered to the next operator on any facility transfer.

CASA technical airworthiness chain documentation overlays the standard building documentation for any facility supporting CASA-registered aircraft. The CASA-approved maintenance organisation must hold the documentation against the relevant maintenance procedure and the duct system maintenance schedule integrates into the maintenance management system that the maintenance organisation operates. DEF (Aust) 5613 documentation overlays the same on defence platforms.

FAQ

What NFPA 409 group classification applies to a wide-body aircraft hangar in Australia?

Group I covers single-fire-area exceeding 3,716 m squared or hangar designed for aircraft with tail height over 8.5 m — wide-body Qantas Mascot and Boeing Defence Australia E-7A Wedgetail bays fall in this category. Group II covers 1,394 to 3,716 m squared for narrow-body Jetstar Tullamarine and Virgin Brisbane. Group III covers under 1,394 m squared for regional turboprop Rex Wagga Wagga and corporate jet Hawker Pacific. Group I mandates high-expansion foam suppression at 1,500 L/min/m squared discharge density and 4 ACH mechanical ventilation with 6 ACH smoke removal within 30 seconds.

How is jet fuel vapour extracted during fuel tank entry maintenance?

ATA Spec 100 Chapter 28 governs aircraft fuel tank entry. The tank interior is Zone 0 per AS/NZS 60079.10.1. The tank is inerted with gaseous nitrogen until oxygen falls below 4%, then ventilated with portable explosion-rated extract fans at 30 to 60 ACH through flexible conductive hose to fixed 316L stainless ductwork. LEL must fall below 10% and oxygen return to 19.5 to 23.5% before human entry. Operator-breathing-zone benzene monitoring at 1 ppm STEL is continuous.

What ductwork material is required for an aircraft paint stripping bay?

316L stainless 1.5 to 2.0 mm for the bath canopy hood and 304L stainless for the connection duct. Modern strippers (benzyl alcohol, phenol, NMP biodegradable) replaced methylene chloride DCM banned in Australia in 2023. Pre-2023 facilities with residual DCM stock require 316L throughout because of chloride attack on 304L. Bath operates 50 to 80 degree Celsius with intermittent steam clean and generates 200 to 1,500 ppmv VOC plus paint debris particulate.

How are isocyanate exposures controlled in an aerospace paint booth?

Polyurethane topcoat (Imron AVI, Awl-grip, Desothane, Alexit) contains TDI and MDI at 0.005 ppm STEL — the lowest WES in any industrial process. Booth is Zone 1 per AS/NZS 60079.10.1 with conducted-only spray, 0.4 to 0.5 m/s downdraft supply, supplied-air respirators mandatory, continuous TDI/MDI monitoring at the operator breathing zone and 316L stainless ductwork with full continuous TIG-welded seams. Any porosity releases isocyanate to the hangar and can trigger anaphylactic-grade asthma in a sensitised operator.

What is the Cr VI chromate conversion coating concern?

Chromate conversion (Iridite, Alodine 1200) deposits Cr VI passivation on aluminium aircraft skin before paint. Cr VI hexavalent chromium at 0.05 mg/m cubed STEL is IARC Group 1 carcinogen, the killer exposure for any aerospace surface treatment shop. Australian aerospace is progressively phasing chromate to non-chromate SAA, TSA and BSAA anodise alternatives, but legacy F/A-18A Classic Hornet, Hawk MK127 and C-130 spare repair at BAE Williamtown and Boeing Defence Australia Amberley still run chromate. Duct is 316L stainless 1.5 mm with full continuous welding.

How is composite carbon fibre dust captured?

Cured CFRP, AFRP Kevlar and GFRP composite generates respirable dust during sanding, drilling and machining at Quickstep Bankstown, Boeing Aerostructures Fishermans Bend and Marand Melbourne. WES is 5 mg/m cubed respirable, dropping to 1 mg/m cubed where formaldehyde from phenolic resin is present. Capture is at-source with downdraft sanding tables or LEV arms at 30 to 50 m cubed per hour, ducted to HEPA-filtered cyclone or bag house in 316L stainless with conductive bonding throughout because dry carbon fibre is electrically conductive.

What is the typical exhaust temperature in a jet engine test cell?

Engine exhaust leaves the turbine at 600 to 800 degree Celsius, mixes with bypass air through the augmenter and exits the stack at 200 to 400 degree Celsius after augmenter cooling. NFPA 423 governs the test cell. Augmenter duct material is 309S or 310S stainless at 3 to 6 mm wall thickness, cut on SBPC1500 plasma and welded manually with TIG full penetration. Stack downstream of augmenter cooling drops to 304L at 2 to 3 mm.

Which SBKJ machine handles 316L stainless aerospace paint booth ductwork?

SBAL-V auto duct line in 316L configuration with hardened TDF dies, upgraded forming pressure for 485 MPa yield, and stainless-compatible tooling. Single-shift output 350 to 500 m on 1.5 mm 316L. For round duct (composite extract, fuel tank vent, engine bleed-air) the SBFB-1500 spiral former handles 250 to 1,500 mm at 0.6 to 2.0 mm wall. SBSF-1525 stitchwelder produces 2 to 6 mm 316L riser with manual TIG finish.

What air change rate is required in an aircraft maintenance hangar?

NFPA 409 mandates 4 ACH minimum mechanical ventilation for Group I and II hangars, rising to 6 to 8 ACH during fuel tank entry, paint stripping, paint spray and composite sanding. Smoke removal at 6 ACH within 30 seconds of fire alarm. AS 1668.2 section 4 mirrors the NFPA 409 ventilation rates. AS 1668.1 governs the smoke-spill system at 250 degree Celsius / 2 hour fire-rated ductwork.

What lead time should we plan for aviation MRO HVAC duct fabrication machinery?

SBAL-V galvanised configuration 12 to 14 weeks, 316L stainless variant 14 to 16 weeks, SBFB-1500 spiral former 10 to 12 weeks, SBSF-1525 stitchwelder 12 to 14 weeks, SBPC1500 plasma table 8 to 10 weeks. Add 4 to 6 weeks ocean freight to Australian ports and 1 to 2 weeks for installation, commissioning and training by SBKJ engineers from our Box Hill North VIC service base. ARBS 2026 May Sydney is the practical venue for live demonstration and project scoping discussions.

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