NTSB Identification: CHI91IA078.
The docket is stored on NTSB microfiche number 44057.
Scheduled 14 CFR operation of NORTHWEST AIRLINES, INC.
Incident occurred Sunday, January 20, 1991 in ST. PAUL, MN
Probable Cause Approval Date: 09/28/1992
Aircraft: BOEING 727-251, registration: N295US
Injuries: 44 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

THE FLIGHT CREW WAS INFORMED BY THE TOWER OF A FIRE ON THE RIGHT SIDE OF THE AIRPLANE WHILE TAXIING FOR TAKEOFF. THE FIRE PRECEEDED BY UTILIZING THE AUXILARY POWER UNIT (APU) FOR A MAIN ENGINE START. THE MAIN ENGINE START WAS ABORTED WHEN THE APU FAILED TO DELIVER SUFFICIENT BLEED AIR PRESSURE. A POST INCIDENT INSPECTION OF THE APU DISCLOSED A LIBERATED TURBINE EXDUCER BLADE WHICH CAUSED AN IMBALANCE OF THE TURBINE WHEEL, ALLOWING SMOPKE AND FLAMES TO ESCAPE FROM THE APU EXHAUST ATOP THE RIGHT WING ROOT. THERE HAS BEEN 7 SERVICE DIFFICULTY REPORTS AND 4 ACCIDENTS/INCIDENTS ASSOCIATED WITH EXDUCER FAILURES IN THIS MODEL APU IN THE LAST FIVE YEARS.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

THE PARTIAL FAILURE OF THE AIRPLANE'S AUXILIARY POWER UNIT, AND THE INADEQUATE COMPONENT PRODUCED BY THE MANUFACTURER.

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