A-91-045
NTSB Safety Recommendation — Aviation
Recommendation text
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: CONDUCT A CERTIFICATION REVIEW OF THE PW4000 ENGINE-EQUIPPED BOEING 767 AIRPLANE THRUST REVERSER SYSTEMS TO EVALUATE ELECTRICAL AND MECHANICAL ANOMALIES AND FAILURE MODES THAT CAN ALLOW DIRECTIONAL CONTROL VALVE PRESSURE TO BE APPLIED TO THE REVERSER EXTEND PORT. THE CERTIFICATION REVIEW SHOULD INCLUDE SUBJECTING THE VALVE TO THE ENGINE'S VIBRATION SPECTRUM CONCURRENT WITH INTRODUCTION OF INTERMITTENT PRESSURE SPIKES TO THE VALVE PRESSURE PORT. THE CERTIFICATION REVIEW SHOULD ALSO DETERMINE THE ADEQUACY OF THE THRUST REVERSER SYSTEM SAFEGUARDS WHEN THE HYDRAULIC ISOLATION VALVE IS OPEN TO PREVENT UNCOMMANDED THRUST REVERSER EXTENSIONS. (URGENT)
In plain language (FlightFinder summary)
The FAA is asked to conduct a certification review of the PW4000 engine-equipped Boeing 767 thrust reverser systems, focusing on electrical and mechanical anomalies that could allow pressure to the reverser extend port. The review must test the directional control valve under engine vibration with intermittent pressure spikes, and assess whether safeguards prevent uncommanded reverser extensions when the hydraulic isolation valve is open. The recommendation is marked as urgent.
This plain-language summary is written by FlightFinder to explain the recommendation above. It is not the official wording — the verbatim NTSB text is quoted above.
Details
| Status | Closed - Acceptable Action |
|---|---|
| Mode | Aviation |
| Closed | May 5, 1992 |
| NTSB number | DCA91RA037 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).