FlarePath

What happened

NTSB summary, verbatim

A Delta Air Lines Boeing 757-2Q8 airplane, N704X, experienced a tailpipe fire in the No.2 (right) engine, a Pratt & Whitney (P&W) PW2037, during engine start at the Minneapolis-St. Paul International Airport, Minneapolis, Minnesota. The main and aft inboard flaps and inboard flap track fairing on the right wing were blistered, charred, and delaminated, and the right main landing gear fairing was blistered. During engine start, the pilots stated that the No. 2 engine lit off immediately. The pilots stated that immediately after the engine lit off, they were distracted by a yellow glow on the right side of the airplane that grew in intensity; the captain initially thought it was an airport vehicle approaching the airplane. The pilots then heard a low frequency rumbling sound; and also heard people talking on the ground control frequency about an airplane on fire. The captain stated that when he looked back at the engine indications, the No. 2 engine fuel flow was 8,300 pounds per hour (pph); the normal is 1,000 pph. The captain then called for the engine to be shut down. The interrogation of the engine indicating and crew alerting system electronic propulsion control system page revealed several fault codes indicating that the fuel control unit (FCU) fuel metering valve (FMV) did not move to the position commanded by the electronic engine control. The disassembly of the FCU revealed corrosion on the FMV sleeve and slide. According to the FCU manufacturer, when the PW2037 engine is shut down, the FCU FMV is in the full open position. The airplane had been parked outside on the ramp in subzero temperatures for about 36 hours before the incident occurred. Naturally present water in the fuel nucleated on the corrosion on the FMV sleeve and slide, freezing it in position, which prevented it from during before engine start. The manufacturer also stated that at the time of the event, when the high pressure rotor speed was about 40 percent, the fuel flow with the FCU FMV in the full open position would be in the 8,000 pph range.

Photographs

20the aircraft, and what the investigators found

The aircraft before the accident

Wreckage and site documentation · 19 photographs from the docket

Photographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.

Probable cause

the Board's determination

the failure of the right engine's fuel control unit to operate correctly when the fuel metering valve became frozen in the full open position because of corrosion on the fuel metering valve slide and sleeve, which caused the engine to be overfueled during engine start and resulted in a tailpipe fire.

Occurrence sequence

1 stepsNTSB coding · CICTT taxonomy

1 · Standing-engine(s) start-up
Fire/smoke (non-impact)
defining event

Findings

1 causal · 0 contributing

CAUSE
Aircraft › Aircraft power plant › Engine fuel and control › Fuel control electronic — Malfunction

Sequence of events

6 timed eventsfrom the FDR factual report · claude-sonnet-5

0631 CSTEngine startp.2
Data began recording with the left engine beginning to power up
0632:50 CSTEngine startp.2
Right engine N2 began increasing
approximately 0633:11 CSTEngine startp.2
Fuel cutoff parameter changed from cutoff to not cutoff (about 21 seconds after N2 began increasing)
0633:27 CSTEngine startp.2
Fuel flow for the right engine measured 8096 pph
0634:06 CSTEngine startp.2
Fuel cutoff parameter for the right engine indicated cutoff and the N2 values decreased
approximately 0656 CSTPost-eventp.2
FDR stopped recording about 22 minutes later

NTSB analysis

from the final report

A Delta Air Lines Boeing 757-2Q8 airplane, N704X, experienced a tailpipe fire in the No.2 (right) engine, a Pratt & Whitney (P&W) PW2037, during engine start at the Minneapolis-St. Paul International Airport, Minneapolis, Minnesota. The main and aft inboard flaps and inboard flap track fairing on the right wing were blistered, charred, and delaminated, and the right main landing gear fairing was blistered. During engine start, the pilots stated that the No. 2 engine lit off immediately. The pilots stated that immediately after the engine lit off, they were distracted by a yellow glow on the right side of the airplane that grew in intensity; the captain initially thought it was an airport vehicle approaching the airplane. The pilots then heard a low frequency rumbling sound; and also heard people talking on the ground control frequency about an airplane on fire. The captain stated that when he looked back at the engine indications, the No. 2 engine fuel flow was 8,300 pounds per hour (pph); the normal is 1,000 pph. The captain then called for the engine to be shut down. The interrogation of the engine indicating and crew alerting system electronic propulsion control system page revealed several fault codes indicating that the fuel control unit (FCU) fuel metering valve (FMV) did not move to the position commanded by the electronic engine control. The disassembly of the FCU revealed corrosion on the FMV sleeve and slide. According to the FCU manufacturer, when the PW2037 engine is shut down, the FCU FMV is in the full open position. The airplane had been parked outside on the ramp in subzero temperatures for about 36 hours before the incident occurred. Naturally present water in the fuel nucleated on the corrosion on the FMV sleeve and slide, freezing it in position, which prevented it from during before engine start. The manufacturer also stated that at the time of the event, when the high pressure rotor speed was about 40 percent, the fuel flow with the FCU FMV in the full open position would be in the 8,000 pph range.

BOEING 757-2Q8DELTA AIR LINES INC