A-73-078
NTSB Safety Recommendation — Aviation
Recommendation text
REQUIRE CHANGES IN THE APPROVED MAINTENANCE MANUAL FOR ALL BOEING 707/720 AIRCRAFT TO: (A) SPECIFY A MORE PRECISE METHOD OF MEASURING THE NET ELEVATOR HINGE FRICTION THROUGHOUT THE ENTIRE RANGE OF CONTROL SURFACE TRAVEL; AND (B) SPECIFY A MORE DEFINITIVE METHOD FOR ADJUSTING THE BALANCE PANEL SEALS WITHIN THE DESIRABLE TOLERANCE. AT PRESENT, THE MANUAL SPECIFIES A 0-0.020-INCH FIT BETWEEN THE BALANCE PANEL SEAL AND THE STABILIZER STRUCTURE. A -0.020-INCH MEASUREMENT IMPLIES SEAL COMPRESSION WHICH IS EXTREMELY DIFFICULT TO MEASURE ACCURATELY.
In plain language (FlightFinder summary)
The FAA is asked to update maintenance manuals for Boeing 707 and 720 aircraft to include clearer instructions for checking elevator hinge friction and adjusting balance panel seals. The current guidelines allow for seal compression measurements that are too difficult to verify accurately, so the new rules must define more precise methods for these specific checks throughout the full range of control surface movement.
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 | Oct 2, 1974 |
| NTSB number | LAX74AL019 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).