Aft pressure bulkhead
Rear pressure seal component for aircraft cruising in the tropopause.
The aft pressure bulkhead, sometimes called the rear pressure bulkhead, seals the back end of the pressurized section on any aircraft that cruises in the tropopause zone. Its job is to keep cabin pressure stable during high-altitude flight and prevent the fuselage from bursting under the higher internal pressure.
Designs vary: curved bulkheads use less metal but cut into usable cabin space, while flat ones offer more room but add weight. Some patents propose building cavities into the bulkhead to reclaim cabin space. On several airliner models, manufacturers outsource production of this part to third parties. Though uncommon and time-consuming, the entire bulkhead can be replaced.
In the 21st century, interest grew in composite bulkheads, which promise lower production costs, easier sealing, no corrosion risk, and reductions in both weight and part count. In the early 2000s, Airbus Group built the largest resin film infusion structure then in production for the A380’s aft pressure bulkhead. German supplier Premium AEROTEC produced the world’s first thermoplastic rear pressure bulkhead in the 2010s, claiming a 75% cut in processing and assembly time and noticeable weight savings over aluminum.
Failures have occurred, with some causing total losses and others survivable. Regulators often mandate inspections, and engineers have developed techniques to check integrity both in service and during design to ensure sufficient strength for a safe lifespan.
In 1971, British European Airways Flight 706 crashed in Belgium, killing all 63 aboard, after corrosion from fluid contamination—likely from a lavatory—weakened the rear pressure bulkhead. The corrosion was undetectable by the inspection methods then available.
In 1985, Japan Air Lines Flight 123 crashed when its aft pressure bulkhead catastrophically failed. The failure traced back to a faulty repair after a tailstrike seven years earlier: a single repair patch had been cut in two “to make it fit.” The bulkhead’s rupture damaged hydraulic pipes running through it. Boeing later calculated the incorrect installation would fail after about 10,000 pressurizations; the aircraft had completed 12,318 successful flights before the crash.
In 2013, National Airlines Flight 102 crashed after loose freight on the main deck is believed to have punched through the aft pressure bulkhead, damaging nearby control systems.
- Design options
- curved or flat
- First thermoplastic bulkhead manufacture
- Premium AEROTEC
- Processing time reduction claimed
- 75%
- A380 bulkhead type
- largest manufactured resin film infusion structure then in production
- Flight 706 cause
- corrosion of the rear pressure bulkhead by fluid contamination
- Flight 123 cause
- faulty repair of the bulkhead after a tailstrike
- Flight 123 cycles before crash
- 12,318
Lore & Background
Aft pressure bulkheads can be either curved, which reduces metal needed but reduces usable space, or flat, which gives more internal space but adds weight. Patents have been filed proposing cavities within the rear bulkhead to provide more usable cabin space. Production has been outsourced to third party manufacturers on several airliners, and the bulkhead can be wholly replaced, though this is time-consuming and uncommon. During the twenty-first century, interest grew in composite bulkheads for lower costs, easier sealing, corrosion elimination, and weight and part count reductions. In the early 2000s, Airbus Group developed the largest manufactured resin film infusion structure then in production for the A380. Premium AEROTEC manufactured the world's first thermoplastic-based rear pressure bulkhead during the 2010s, claiming a 75% reduction in processing and assembly time and noticeable weight savings over aluminium counterparts. Multiple failure incidents have occurred. In 1971, British European Airways Flight 706 crashed due to corrosion from fluid contamination undetectable by then-current inspection techniques. In 1985, Japan Air Lines Flight 123 crashed after a faulty repair patch was incorrectly cut in two, failing after 12,318 pressurizations. In 2013, National Airlines Flight 102 crashed after loose freight is believed to have penetrated the bulkhead.
Reader's Guide
The aft pressure bulkhead is a critical structural component for aircraft operating in the tropopause, as it maintains cabin pressure and prevents structural failure from internal pressure. Its design involves trade-offs between curved and flat shapes, affecting space and weight. The article notes that patents have been filed to create cavities for more cabin space, and production has been outsourced on several airliners. Composite development in the twenty-first century aimed at cost, sealing, corrosion, and weight benefits, with Airbus Group producing a large resin film infusion structure for the A380 and Premium AEROTEC creating the first thermoplastic bulkhead with claimed processing time and weight savings. Failure incidents highlight the bulkhead's vulnerability: corrosion from fluid contamination caused the 1971 crash of British European Airways Flight 706; faulty repair led to the 1985 Japan Air Lines Flight 123 crash after over 12,000 pressurizations; and loose freight penetration is believed to have caused the 2013 National Airlines Flight 102 crash. These events have led aviation certifying authorities to mandate inspections, and various techniques have been devised to assess integrity both in service and during design to ensure safe operational life.
Did You Know?
- The aft pressure bulkhead helps protect the aircraft from bursting due to higher internal pressure when stratocruising.
- British European Airways Flight 706 crashed in 1971 due to corrosion from fluid contamination undetectable by inspection techniques at the time.
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