Investigation brief · generated 2026-10-09 · source: NTSB public docket and accident database
ATR ATR72 — St. Croix, USA, 2010-01-12
NTSB number
ENG10IA010
Operator
American Airlines
Registration
N434AT
Highest injury
No injury
Regulation
Part 121
Damage
Minor
Cohort
Part 121 airline
Recorder data
Tier 1 — decoded recorder tables
Every sentence below is taken directly from NTSB records — the accident database, the docket's recorder reports and the Board's findings — with its source noted. Nothing is paraphrased or inferred.
NTSB summary
During takeoff the No. 1 (left) engine fire warning illuminated in the cockpit. The pilot declared an emergency, shut down the No. 1 engine and discharged one fire bottle. The fire warning continued and the pilot discharged the second bottle; but the fire warning did not extinguish. The pilot performed an air turnback and landed the airplane uneventfully approximately 11 minutes later.
Engine testing at the manufacturer’s facility revealed a large fuel leak emanating from the No. 2 fuel nozzle manifold adapter-to-transfer tube O-ring connection.
Examination revealed two manufacturing defects in the No. 2 fuel nozzle manifold adapter. The first defect, poor surface finish, caused damage to the transfer tube O-ring during the installation process, initiating an internal fuel leak. The second defect, blockage of the internal safety tell-tale drain due to an improper machining and subsequent cleaning procedure, prevented the leaking fuel from flowing into the tell-tale drain and being detected by maintenance personnel.
Examination of the transfer tubes revealed an undersized O-ring retention zone, which allowed the O-ring to fit loosely such that it was not capable of withstanding continuous maximum fuel pressure load. Eventually the O-ring failed to seal properly, fuel leaked and was ignited by the hot combustor case. The undersized O-ring retention zone was created during the cleaning and overhaul process of the transfer tube.
The sealing failure between the fuel nozzle adapter assembly and fuel transfer tubes that allowed fuel to leak into the nacelle fire zone where it was subsequently ignited by the hot combustor case. Contributing to the failure was a combination of manufacturing defects of the fuel nozzle adapter assembly by the manufacturer and incorrectly overhauled fuel transfer tubes by the engine manufacturer. Contributing to the incident was a second defect of the fuel nozzle adapter assembly by the manufacturer which prevented maintenance personnel from detecting the internal fuel leak.
Verbatim, NTSB determination.
Flight data recorder
FDR — 1,821 samples, 33 parameters, 19:24:19.0 to 19:54:39.0.
Parameter
Max
at
Min
at
Final
at
Pressure altitude ft
8,169.0
19:44:12.0
-4,095.0
19:47:19.0
-84.0
19:54:38.0
Pitch attitude deg
16.3
19:36:45.0
-11.4
19:45:47.0
-0.9
19:54:38.0
Roll attitude deg
11.9
19:43:36.0
-37.6
19:42:00.0
0.0
19:54:38.0
Vertical acceleration g
1.3
19:42:09.0
0.8
19:47:32.0
1.0
19:54:38.0
Computed from the docket's tabular attachment; times as recorded (local or SRN as published).
Sequence of events (FDR factual report)
Time
Event
Page
19:36:38
Aircraft took off
3
~19:39:38
Autopilot engaged about 3 minutes after takeoff
3
19:41:13
Left engine fire warning started on the FDR, continuing until just after touchdown; master warning also indicated at this time and remained on for 6 seconds
3
19:41:25
Autopilot disengaged
3
~19:41:27
Left engine power lever angle began to decrease, followed by left engine power decrease
3
~19:41:37
Left engine propeller RPM reading began registering invalid data about 10 seconds after PLA began decreasing
3
unspecified
Left engine torque reached 0% and remained at that value for the rest of the flight
3
19:47:31
Aircraft touched down
3
Extracted by claude-sonnet-5; 7 of 8 stated events verified against the raw recorder data.