NTSB Identification: DEN90IA012.
The docket is stored on NTSB microfiche number 39110.
Scheduled 14 CFR NORTHWEST AIRLINES
Incident occurred Wednesday, October 18, 1989 in MONTE VISTA, CO
Probable Cause Approval Date: 01/08/1991
Aircraft: MCDONNELL DOUGLAS DC-9, registration: N922RW
Injuries: 1 Minor,102 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.

WHILE IN CRUISE AT FL350 THE NO. 2 GENERATOR CONSTANT SPEED DRIVE (CSD) FAILED AND THE CREW INADVERTENTLY DISCONNECTED THE NO. 1 GENERATOR CSD. ATTEMPTS TO START THE APU ABOVE THE START ENVELOPE WERE MADE BUT ABORTED DUE TO A HOT START. A DESCENT WAS MADE ON EMERG ELECTRICAL POWER AND A LANDING WAS MADE AT AN ARPT WHICH WAS INADEQUATE FOR THE ACFT. THE CREW CHOSE TO MAKE A NO FLAP APCH AND TO LOWER LANDING GEAR BY EMERG METHOD WHEN BOTH SYSTEMS WERE OPERABLE BY NORMAL MEANS. THIS DECISION WAS INFLUENCED BY THE LACK OF LANDING GEAR AND FLAP POSITION INDICATORS WHEN THE ACFT IS OPERATED ON BATTERY POWER. THE LANDING SPEED WAS FAST AND THE ACFT DEPARTED THE END OF THE RWY DAMAGING THE LANDING GEAR AND THE NO. 1 ENGINE. THE CREW FAILED TO MANUALLY DEPRESSURIZE THE ACFT AND THE EVACUATION WAS DELAYED UNTIL A KNOWLEDGEABLE PASSENGER WENT TO THE COCKPIT AND DEPRESSURIZED THE ACFT. THE OPERATORS ACFT OPERATING MANUAL DID CONTAIN APU STARTING PROCEDURES BUT NOT AN APU START ENVELOPE CHART.

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

THE POOR INFLIGHT PLANNING AND DECISIONS MADE BY THE FLIGHT CREW FOLLOWING THE FAILURE OF THE NUMBER TWO GENERATOR CONSTANT SPEED DRIVE UNIT. CONTRIBUTING FACTORS TO THE ACCIDENT WERE THE FAILURE OF THE NO. 2 GENERATOR CONSTANT SPEED DRIVE UNIT AND THE CREW'S INADVERTENT SHUT DOWN OF THE WRONG GENERATOR WHICH RESULTED IN A COMPLETE LOSS OF ELECTRICAL POWER.

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