A-70-049
NTSB Safety Recommendation — Aviation
Recommendation text
1. INITIATE APPROPRIATE ACTION TOWARD THE OPERATORS' MAINTAINING A PROGRAM OF CURRENT ENGINE CONDITION MONITORING. 2. REVIEW ENGINE INSTRUMENTATION CALIBRATION AND EXISTING INSTRUMENT TOLERANCES TO ASSURE THE MOST PRECISE ENGINE OPERATING PARAMETER INDICATIONS. 3. IMPROVE THE RELIABILITY OF AUXILIARY POWER UNITS IN ORDER TO REDUCE THE PROBABILITY OF HIGH THERMAL TRANSIENTS WHILE STARTING ENGINES WITH MARGINAL AIR SUPPLY. 4. ENSURE THAT FLIGHTCREWS MAINTAIN ADEQUATE PNEUMATIC AIR DUCT PRESSURE DURING ENGINE STARTS. 5. RECORD ANY ABNORMAL STARTS WHEN AN APPROACH TO A "RECOVERABLE STALL" IS EXPERIENCED. 6. ESTABLISH PRECISE LIMITATIONS REGARDING THE NUMBER OF "APPROACHES TO RECOVERABLE STALL" CONDITIONS WHICH MAY BE TOLERATED WITHOUT CUMULATIVE ADVERSE EFFECTS UPON TURBINE BLADE DURABILITY. 7. INCORPORATION OF THE "VENTED" FIRST-STAGE TURBINE BLADE IN ALL JT9D SERIES ENGINES BE THE SUBJECT OF REGULATORY ACTION AS SOON AS SUFFICIENT PRODUCTION IS ASSURED AND SERVICE BULLETINS AND ENGINEERING ORDERS ARE FORMULATED BY THE MANUFACTURER. 8. CONSIDERATION SHOULD BE GIVEN TO REQUIRE THE USE OF WATER INJECTION FOR ALL TAKEOFFS REGARDLESS OF TAKEOFF THRUST REQUIREMENTS. 9. UPON INSTALLATION OF THE IMPROVED, "VENTED" TURBINE BLADES IN ALL ENGINES, THE MANDATORY USE OF WATER INJECTION COULD BE RESCINDED.
In plain language (FlightFinder summary)
The FAA is asked to enforce stricter maintenance standards for engine health monitoring and instrument accuracy while improving auxiliary power unit reliability to prevent overheating during engine starts. The recommendation also requires tracking abnormal start events and setting clear limits on turbine blade stress to ensure long-term durability. Finally, the agency should mandate a specific turbine blade design for all relevant engines and consider requiring water injection during takeoffs until that upgrade is fully implemented.
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 | Jun 5, 1973 |
| NTSB number | DCA71IZ002 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).