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Safety Recommendation Details

Safety Recommendation A-67-035
Details
Synopsis: ON OCTOBER 17, 1967, A NORTHWEST AIRLINES B-727, N466US, NO. 3 ENGINE, PRATT & WHITNEY JT8D-1, SHORTLY AFTER TAKEOFF FROM MILWAUKEE, WISCONSIN, EXPERIENCED A POWER LOSS ACCOMPANIED BY A SUDDEN DROP IN OIL QUANTITY AND INCREASE IN OIL PRESSURE. THE FLIGHT RETURNED TO MILWAUKEE TWELVE MINUTES AFTER TAKEOFF WITHOUT INCIDENT OR INJURY TO PERSONNEL.
Recommendation: 1. THAT COMPLIANCE WITH PRATT & WHITNEY TURBOJET SERVICE BULLETIN NO. 1158 BE MADE MANDATORY AT THE EARLIEST DATE PRACTICAL ON JT8D ENGINES NOT SO MODIFIED AT MANUFACTURE. 2. THAT THE ADEQUACY OF THE POWERPLANT FIRE WARNING SYSTEM BE REEVALUATED RELATIVE TO THE PROBLEMS ASSOCIATED WITH FAN DUCT FIRES.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: Milwaukee, WI, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: 79526
Accident Reports: North Central Airlines, Inc., Convair 580, N46345, Home Airmotive, Inc., Cessna 150, N8742S, Midair Collision
Report #: None
Accident Date: 10/17/1967
Issue Date: 12/29/1967
Date Closed: 1/1/1975
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s): Fire,

Safety Recommendation History
From: FAA
To: NTSB
Date: 1/15/1968
Response: SINCE THE ENGINE MANUFACTURER HAS BEEN CAMPAIGNING THE MODIFICATION, AND SINCE THE MODIFICATION CAN BE ACCOMPLISHED AT HOT-SECTION INSPECTION PERIODS IN ADDITION TO OVERHAUL, THE REMAINING 25 PERCENT WILL ALSO BE MODIFIED. WE HAVE REAPPRAISED THE NEED FOR MANDATORY ACTION TO REQUIRE COMPLIANCE WITH P&WA SERVICE BULLETIN 1158 AND, IN VIEW OF THE ACTION ALREADY TAKEN AND CONTEMPLATED BY THE COOPERATIVE EFFORTS OF THE ENGINE MANUFACTURER AND AIRLINES INVOLVED, WE BELIEVE THE DIFFICULTY IS BEING ADEQUATELY CORRECTED. WITH RESPECT TO THE RECOMMENDATION THAT THE POWERPLANT FIRE WARNING SYSTEM BE REEVALUATED RELATIVE TO THE PROBLEMS ASSOCIATED WITH FAN DUCT FIRES, THIS QUESTION WAS ORIGINALLY CONSIDERED DURING THE ENGINEERING INVESTIGATION PRECEDING TYPE CERTIFICATION. AT THAT TIME, IT WAS CONCLUDED THAT SUCH FIRES THAT COULD EXIST WITHIN THE FAN DUCT WOULD NOT BE HAZARDOUS AND, THEREFORE, WOULD NOT REQUIRE DETECTION. IT WAS CONCLUDED THAT THE ENGINE INDICATORS WOULD PROVIDE AMPLE WARNING OF ENGINE FAN DUCT FIRES SHOULD THEY OCCUR. EARLY DEVELOPMENT TESTS BY THE ENGINE MANUFACTURER AND SUBSEQUENT EXPERIENCE HAVE CONFIRMED THE VALIDITY OF THIS CONCLUSION. IN REEVALUATING THIS SPECIFIC INCIDENT, IT WAS NOTED THAT THE FIRE BURNING IN THE FAN DUCT DID NOT PRODUCE ANY EVIDENCE OF HEAT ON THE ENGINE OUTER CASE AND THE FIRE WAS WHOLLY CONTAINED WITHIN THE ENGINE ITSELF. SUCH A FIRE WOULD NOT REQUIRE DIRECT DETECTION BUT WAS DETECTED BY A LOSS OF POWER, A DROP IN OIL QUANTITY, AND A RISE IN OIL PRESSURE PRIOR TO SHUTDOWN OF THE ENGINE. IN SUMMARY, YOUR RECOMMENDATION PERTAINING TO THE ACCOMPLISHMENT OF P&WA SERVICE BULLETIN 1158 IS BEING IMPLEMENTED WITHOUT THE NEED FOR MANDATORY ACTION. ALSO, YOUR SUGGESTED REAPPRAISAL OF THE POWERPLANT FIRE WARNING SYSTEM HAS SHOWN THAT ADEQUATE FIRE PRECAUTIONS ARE PRESENT IN THE BOEING 727 POWERPLANT INSTALLATION.