AD 78-08-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-300 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400 Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400D Series | BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-400F Series | BOEING Model 747 Series Airplanes |
Unsafe Condition
Delamination or cracks in the hinge-to-gate bonds of outflow valve assemblies could cause rapid loss of pressurization in flight.
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Required Actions
Inspect forward and aft gates of each outflow valve assembly per Boeing Service Bulletin 747-21-2139 or approved method. Replace gates with delamination or cracks. Modify outflow valve assemblies per Hamilton Standard Service Bulletin H.S. Code 747 AC-114 or approved method within 4000 hours time in service.
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Compliance Time
Within 350 hours time in service after May 10, 1978, and thereafter every 900 hours time in service until modified. Modify within 4000 hours time in service after May 10, 1978.
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Affected Aircraft
Boeing Model 747 series airplanes with outflow valve assemblies P/N 60B00025-3, -11, -12, -17 or Hamilton Standard P/N 719201-2 through -9.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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