A-91-077
NTSB Safety Recommendation — Aviation
Recommendation text
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: ISSUE AN AIRWORTHINESS DIRECTIVE REQUIRING A CHECK ON ALL BOEING 737 AND 727 MODEL AIRPLANES WITH THE P/N 1087-23 INPUT SHAFT IN THE RUDDER AUXILIARY ACTUATOR UNIT FOR THE FORCE NEEDED TO ROTATE THE INPUT SHAFT LEVER RELATIVE TO THE P/N 1087-22 BEARING OF THE AUXILIARY ACTUATOR UNIT. DURING THIS CHECK, THE BEARING SHOULD BE INSPECTED TO DETERMINE IF IT ROTATES RELATIVE TO THE HOUSING. ALL SHAFT ASSEMBLIES IN WHICH ROTATION OF THE BEARING OCCURS, OR IN WHICH EXCESSIVE FORCE IS NEEDED TO MOVE THE INPUT LEVER, SHOULD BE REMOVED FROM SERVICE ON AN EXPEDITED BASIS AND THE ASSEMBLIES SHOULD BE REPLACED WITH A P/N 1087-21 SHAFT ASSEMBLY THAT HAS A REDUCED DIAMETER ON THE UNLUBRICATED PORTION OF THE SHAFT IN ACCORDANCE WITH REVISION G OF THE P/N 1087-23 ENGINEERING DRAWING. ALL ASSEMBLIES MEETING THE FORCE REQUIREMENT SHOULD BE RECHECKED AT APPROPRIATE INTERVALS UNTIL REPLACED WITH A P/N 1087-21 SHAFT ASSEMBLY CONTAINING A P/N 1087-23 SHAFT THAT HAS A REDUCED DIAMETER ON THE UNLUBRICATED PORTION OF THE SHAFT.
In plain language (FlightFinder summary)
The NTSB asks the FAA to issue an airworthiness directive that requires a check on Boeing 737 and 727 airplanes equipped with a specific input shaft (P/N 1087-23) in the rudder auxiliary actuator unit. The check must measure the force needed to rotate the input shaft lever relative to the bearing (P/N 1087-22) and inspect whether the bearing rotates within its housing. Any assembly where the bearing rotates or requires excessive force must be removed from service promptly and replaced with a P/N 1087-21 shaft assembly that has a reduced diameter on the unlubricated shaft portion. Assemblies that pass the force check must be rechecked at regular intervals until they are replaced with the updated shaft assembly.
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 Alternate Action |
|---|---|
| Mode | Aviation |
| Closed | Nov 15, 1993 |
| NTSB number | DCA91MA023 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).