Investigation brief · generated 2026-10-09 · source: NTSB public docket and accident database
BOEING MD-10-10F — Memphis, TN, USA, 2006-07-28
NTSB number
DCA06FA058
Operator
FEDERAL EXPRESS CORP
Registration
N391FE
Highest injury
No injury
Regulation
Part 121
Damage
Substantial
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
The approach and landing were stabilized and within specified limits. Recorded data indicates that the loads experienced by the landing gear at touchdown were within the certification limits for an intact landing gear without any pre-existing cracks or flaws. The weather and runway conditions did not affect the landing. The application of braking by the accident crew, and the overall effect of the carbon brake modification did not initiate or contribute to the landing gear fracture. Post-accident modifications to the MD-10 carbon brake system were implemented due to investigative findings for the purposes of braking effectiveness and reliability. Post accident emergency response by the flight crew and ARFF was timely and correct.
The left main landing gear (LMLG) outer cylinder on the accident airplane had been operated about 8 ½ years since its last overhaul where stray nickel plating likely was introduced in the air filler valve hole. Nickel plating is a permissible procedure for maintaining the tolerances of the inner diameter of the outer gear cylinder, however the plating is not allowed in the air filler valve bore hole. Literature and test research revealed that a nickel plating thickness of 0.008" results in a stress factor increase of 35%. At some point in the life of the LMLG, there was a load event that compressively yielded the material in the vicinity of the air filler valve hole causing a residual tension stress. During normal operations the stress levels in the air filler valve hole were likely within the design envelope, but the addition of the residual stress and the stress intensity factor due to the nickel increased these to a level high enough to initiate and grow a fatigue crack on each side of the air filler valve hole. The stresses at the air filler valve hole were examined via development of a Finite Element Model (FEM) which was validated with data gathered from an instrumented in-service Fedex MD-10 airplane. The in-service data and FEM showed that for all of the conditions, the stress in the air filler valve hole was much higher than anticipated in the design of the outer cylinder. Fatigue analysis of the in-service findings and using the nickel plating factor resulted in a significantly reduced fatigue life of the gear cylinder compared with the certification limits. During the accident landing the spring back loads on the LMLG were sufficient to produce a stress level in the air filler valve hole that exceeded the residual strength of the material with the fatigue cracks present.
the failure of the left main landing gear due to fatigue cracking in the air filler valve hole on the aft side of the landing gear. The fatigue cracking occurred due to the presence of stray nickel plating in the air filler valve hole. Contributing to this was the inadequate maintenance procedures to prevent nickel plating from entering the air filler valve hole during overhaul.
Verbatim, NTSB determination.
Flight data recorder
— 55,965 samples, 75 parameters, 11:16:10.0 to 11:26:06.9.
Parameter
Max
at
Min
at
Final
at
Pressure altitude ft
7,028.0
11:16:10.0
0.0
11:26:06.0
0.0
11:26:06.0
Computed airspeed kts
248.5
11:17:28.3
0.0
11:24:52.3
0.0
11:26:06.3
Pitch attitude deg
7.4
11:24:17.8
-0.9
11:18:22.8
0.0
11:26:06.8
Roll attitude deg
28.5
11:20:35.6
-12.3
11:24:43.4
0.0
11:26:06.9
Vertical acceleration g
1.5
11:24:30.2
-3.4
11:26:06.1
-3.4
11:26:06.8
Engine 1 N1 %RPM
74.1
11:23:02.0
0.0
11:24:42.0
5.6
11:26:06.0
Engine 2 N1 %RPM
72.0
11:23:01.4
0.0
11:26:06.4
0.0
11:26:06.4
Computed from the docket's tabular attachment; times as recorded (local or SRN as published).
Sequence of events (FDR factual report)
Time
Event
Page
last 10 minutes of flight, from about 7,000 ft pressure altitude
Approach overview plotted (plot 2): accelerations, wind, heading, pressure altitude, roll, pitch and computed airspeed; wind data invalid once on the ground (clipped above 50 kts)
5
60 s before to 40 s after touchdown
Detail plots 3-7 of the landing: radio altitudes 1-3, elevators and control column with AOA 1/2 and pitch; ailerons and control wheels with roll; upper/lower rudder, rudder pedal and drift angle; autopilot 1/2, radio keying and engine 1-3 N1
5
landing roll
Plot 8: spoiler positions L3/R3/L5/R5 and armed status, nose gear WOW, gear lever, gear unsafe and down-and-locked indications, engine 1-3 thrust reverser status, left and right brake pedal positions
6
Extracted by claude-fable-5-1 (in-session); 3 of 3 stated events verified against the raw recorder data.
Cockpit voice recorder
302 transcribed utterances from 09:24:57.3 to 11:26:09.7, 13 sources. Final entries:
11:26:03.9
HOT-2
we gotta get off the airplane now.
11:26:04.1
HOT-1
thanks.
11:26:04.9
HOT-1
all right yep.
11:26:07.0
HOT-2
now.
11:26:09.7
HOT-1
leave every-.
The NTSB cautions that a CVR transcript is not a precise science and should not be used as the sole source of information.