NTSB Factual Report

HISTORY OF FLIGHT

On July 28, 2006, about 1125 central daylight time, FedEx Express (FedEx) flight 630, a Boeing MD-10-10F (MD-10), N391FE, experienced a left main landing gear failure immediately after landing at Memphis International Airport (MEM), Memphis, Tennessee. The left main landing gear (LMLG) collapsed after touchdown on runway 18R, and the airplane came to rest on the left side of the runway. After the gear collapsed, a fire developed on the left side of the airplane. The two flight crewmembers received minor injuries during the evacuation, and one nonrevenue FedEx pilot was not injured. The postcrash fire substantially damaged the airplane’s left wing and portions of the left side of the fuselage. Flight 630 departed from Seattle-Tacoma International Airport (SEA), Seattle, Washington, and was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 121 on an instrument flight rules flight plan.

The crew stated that the takeoff and departure from SEA were normal with very little traffic that day, there were no issues with the airplane en route from SEA to MEM and there were no weather deviations. Approaching MEM, air traffic control (ATC) vectored the flight onto the runway 18R final approach course. The flight was then cleared for a visual approach to runway 18R. The visual approach was initially flown with the autopilot engaged and coupled to the instrument landing system (ILS). The airplane was established on the final approach course about 9 miles north of the airport. About 1,600 feet altitude, the airplane was configured for a flaps 35 landing and the approach was stable passing through 1,000 feet. The crew reported that gusty winds at altitude reduced to near calm, or a light tailwind, by this point.

The crew reported the final approach segment was smooth, and the first officer disengaged the autopilot at approximately 400 feet and manually flew the airplane appropriate to conditions. He noted that some crosswind correction was still required at approximately 50 feet, when the electronic altitude callout cadence began. He stated that the flare and touchdown were normal, with crosswind correction. The airplane landed with 122 knots airspeed and a descent rate of approximately 2 to 3 feet per second (fps). A Safety Board performance study concluded that the touchdown was within design limits for the main landing gear (see Tests and Research).

Approximately seven seconds after touchdown, FDR data and performance calculations indicated that the LMLG began to fail (collapse), which was coincident with the location of the ground scar marks on the runway. The first officer reported that while actuating the thrust reversers, he started to apply brakes and immediately experienced "a severe and violent shudder" much more violent than he had ever experienced. He released the brakes, and the shuddering continued, but less violently, and he then reapplied brakes and the shuddering increased again. At that time, the airplane rolled and yawed to the left. The first officer held full right yoke and full right rudder in an effort to counter the turning and listing. The captain tried to assist by using the tiller to keep the airplane on the runway. The airplane continued yawing and sliding to the left and came to rest close to taxiway M4.

Prior to the airplane stopping, a fire ignited beneath the left engine nacelle and spread to the inner portion of the left wing. The captain activated the left engine fire extinguisher and began shutting down the airplane. Airport fire crews responded almost immediately, and the fire was extinguished prior to spreading further.

The crew and nonrevenue pilot evacuated the airplane via the R1 door and slide. The crew reported that due to the leftward list of the airplane, the slide was at a steeper angle than normal.

INJURIES TO PERSONS

The crew reported minor abrasions and sprains from the evacuation. No serious injuries were reported.

DAMAGE TO AIRPLANE

The airplane came to rest on the left side of Runway 18R at the M4 taxiway, about 6,050 feet from the approach end of the runway. The LMLG collapsed during the accident sequence and was folded aft with the strut in a horizontal position and the truck beam in a vertical position. The truck beam positioning actuator was fractured at the truck beam and the axles were in the normal positions. The aft tires of the LMLG impacted the left inboard flap, damaging it and deforming it upwards. The left side of the airplane was resting on the left nacelle, the left wing outboard flap hinge fittings, and the left wingtip while the right side was resting on the right main landing gear (RMLG) inboard tires. The left engine aft mount was fractured and the left engine was canted upwards about the forward mounts. The nose landing gear (NLG) was intact and turned to the right about 20 degrees and was resting on only the left tire. No tread remained on the left NLG tire, some of the reinforcing plies were showing, and there was cross-wise scuffing. The right NLG tire appeared essentially normal. The RMLG was intact with the two inboard tires contacting the ground. The RMLG forward, inboard tire tread was considerably worn while the other three appeared essentially normal. The rest of the airplane was undamaged. The flaps and slats were in the deployed position and the left engine thrust reverser was in the deployed position. The right engine thrust reverser was in the stowed position.

A post crash fire ensued on the left side of the airplane consuming the number 3 slat, the inboard end of the number 4 slat, the left and upper portions of the left nacelle, and the left side of the engine case. The remainder of the left wing and nacelle sustained moderate to heavy fire damage. There was some minor sooting to the left fuselage in the vicinity of the wing attach area. Memphis Airport Rescue and Firefighting responded to the accident within four minutes. Fire did not spread into the interior portions of the airplane.

The outer cylinder of the LMLG was fractured through the air filler valve boss on the aft side of the outer cylinder. The fracture continued around the circumference of the outer cylinder at the same level for about 240 degrees. The fracture then turned upwards and continued around the remaining circumference about 5 inches above the level of the filler valve on the forward side of the outer cylinder. A piece of the outer cylinder about 5 inches high by 8 inches wide was recovered on the runway. The LMLG lower side brace remained attached to the lower outer cylinder and the upper side brace was twisted about 90° along its length. The LMLG retract actuator was in the extended position and the rod end was fractured. The LMLG lock links were fractured.

OTHER DAMAGE

None

PERSONNEL INFORMATION

The two crewmembers had never flown together before this flight pairing, which began on July 26, 2006. On the first day, they flew MEM-SEA, followed by a layover at SEA. On the second day, July 27, 2006, they went SEA-Oakland, California-SEA, followed by another layover. The first flight on the third day, July 28, 2006, SEA-MEM, was the accident flight.

The Captain, age 57, held airline transport, flight instructor, and commercial pilot certificates, with multi-engine land and single-engine land ratings. She was type rated in the Falcon 20, Boeing 727, DC-10 and MD-10/11. The MD-10/11 type rating was issued in November 1993. She was hired by FedEx in February, 1979. Her total flight time was approximately 16,000 hours with 4,223 hours as pilot-in-command in the MD-10/11. She had flown 116 hours, 31 hours, and 6 hours in the last 90 days, 30 days, and 24 hours, respectively prior to the accident flight. Her last line check was in the MD-11 on July 19, 2006. The captain reported that she had served as a check airman on the MD-10/11 between 1997 and 2002. She held a first class medical certificate with a limitation for glasses for intermediate and near vision, and her last medical examination was on July 19, 2006.

A review of FAA records indicated no history of failures or re-tests for FAA airman certificates and ratings. A search of FAA and company records revealed no FAA enforcement actions, incidents, accidents, or company disciplinary actions for the captain.

The First Officer, age 38 held an airline transport certificate, with a multi-engine land rating. He was type rated in the MD-10/11. The MD-10/11 type rating was issued in December, 2005. He was hired by FedEx in April 2004. His total flight time was approximately 5,000 hours with 300-350 second-in-command hours in the MD-10/11. He had flown 90 hours, 38 hours, and 6 hours in the last 90 days, 30 days, and 24 hours, respectively prior to the accident flight. His last line check was in the MD-11 on April 23, 2006. He held a first class medical certificate with no limitations, and his last medical examination was on March 2, 2006. The First Officer reported that he flew the C-17 for 4,000 hours while on US Air Force active duty for 13 years and was currently flying the C-17 in the USAF Reserves.

A review of FAA records indicated that a Notice of Disapproval of Application was issued on December 3, 2005, for an MD-10/11 Type Rating. He subsequently passed the test and was issued a Temporary Airman Certificate on December 8, 2005. A search of FAA and company records revealed no FAA enforcement actions, incidents, accidents, or company disciplinary actions for the first officer.

AIRPLANE INFORMATION

The accident airplane, N391FE, S/N 46625, an MD-10-10F series airplane, was equipped with three General Electric CF6-6D engines, and had been converted from a DC-10-10F to an MD-10-10F in May 2002. According to FedEx records, the accident airplane had 73,283 total hours and 27,002 cycles at the time of the accident. According to the dispatch documents for the accident flight, the airplane’s takeoff weight was 341,069 pounds. The airplane’s estimated landing weight was 284,069 pounds, with a center of gravity (CG) of 18.8% mean aerodynamic chord, including about 43,595 pounds of cargo and about 25,300 pounds of fuel. FedEx documents indicated that the airplane’s maximum landing weight was 374,500 pounds. According to the documents and post accident examination, no hazardous cargo was on board the airplane.

The flight manual indicated that for this weight, and a flaps 35 landing configuration, Vref speed should be 126 knots indicated airspeed.

Main Landing Gear Outer Cylinder

According to the FedEx airplane status report, the LMLG outer cylinder had accumulated 33,148 cycles since new at the time of the accident. However, numerous discrepancies were found between various LMLG records. Further examination of the records revealed that this number was higher than the true number of cycles on the outer cylinder but no accurate number of cycles could be established. The records for all work performed during the July, 2005 overhaul were recovered, and of note was the application of nickel plating to the inner diameter of the cylinder (see Airworthiness Group Factual Report Addendum 3 for the detailed work orders.)

Brake System

The dual redundant brake system is similar in arrangement and function on all DC-10, MD-10, and MD-11 airplanes. The major components of the system are the brake pedals (left and right) coincident with the rudder pedals at the captain’s and first officer’s positions in the cockpit, the two dual brake control valves (DBCV), installed in the left and right main landing gear (MLG) wheel wells, the four anti-skid manifolds (ASM), two each on the left and right MLG’s, and the eight brake assemblies, one on each MLG wheel. Each brake is actuated by 8 brake pistons connected to two independent hydraulic systems, 4 pistons on each system. The brakes are activated by depressing the upper portion of the rudder pedals from either pilot position. The left brake pedals and right brake pedals are mechanically connected together beneath the cockpit floor. Two separate left pedal cable loops and two separate right pedal cable loops each mechanically operate the input lever of one side of one DBCV. Each DBCV receives 3000 psi hydraulic fluid from two separate aircraft hydraulic systems. In response to input lever movement, the applicable side of each DBCV meters the 3000 psi hydraulic fluid to the output port, regulating the line pressure ("metered pressure") in proportion to brake pedal travel. Each metered pressure fluid output is connected to one of the four ASM’s. Inside each ASM are four antiskid valves, each ported/connected to 4 pistons of one brake. Each antiskid valve is independently and electrically controlled by the Antiskid Control Unit, which when commanded, reduces the DBCV metered pressure ported to the 4 pistons of the applicable brake. The ASCU takes information from the wheel speed transducers and automatically reduces the pressure applied to the brakes to prevent a skid.

FedEx worked with Boeing to develop a modified brake system for their MD-10 airplanes that would utilize the same wheels, brakes, and tires used on their fleet of MD-11 airplanes. The MD-11 brake has carbon rotating (rotors) and stationary (stators) disks as opposed to the DC/MD-10 brake, which has steel rotors and stators. The brake system modification installed new antiskid components, MD-11 wheels, tires, and brakes, and modified MLG doors on the MD-10 airplanes under a FAA-approved Boeing Service Bulletins. The accident airplane, N391FE, was one of 15 MD-10-10F and MD-10-30F airplanes converted to the carbon brake system. The carbon brake system was installed on N391FE in July 2005. The carbon brake system did not change the basic operation of the system described above. The airplane (and LMLG) had accumulated 868 cycles since the modification at the time of the accident.

METEOROLOGICAL INFORMATION

The Memphis Surface Observation nearest to the approximate time of the accident (1625 UTC) was as follows:

Memphis special report at 1630 UTC, wind from 270 degrees true at 14 knots gusting to 18 knots, visibility unrestricted at 10 statute miles, a few clouds at 7,500 feet, scattered clouds at 10,000 feet, overcast at 15,000 feet, temperature 26 degrees Celsius (C) (79 degrees F), dew point 18 degrees C (64 degrees F), altimeter 30.15 inches of mercury (Hg). Remarks: automated observation system.

Between 0945 UTC and 1529 UTC rain was reported at the airport, with approximately 0.05 inches reported.

AIRPORT INFORMATION

Memphis International Airport is located about three miles south of Memphis, Tennessee. The airport has three parallel north/south runways and one east/west runway. The parallel runways are numbered 36L-18R, 36C-18C, and runway 36R-18L. The non-parallel runway is numbered 9-27. The airport elevation is 341 feet above mean sea level (MSL).

Runway 36L-18R is constructed of grooved concrete and is 9,320 feet long, and 150 feet wide. The 18R touchdown zone is at 293 feet MSL. It is equipped with an instrument landing system approach, medium intensity approach lighting system with runway alignment indicator (MALSR), and there is no visual approach slope indicator. The ILS glideslope is unusable below 500 feet (200 feet above the runway) due to the bending in the glideslope electronic beam.

FLIGHT RECORDERS

The accident airplane was equipped with a Honeywell 6022 SSCVR 120 Cockpit Voice Recorder, Serial Number 04845. This is a solid-state CVR that records two hours of digital cockpit audio. Upon arrival at the NTSB audio laboratory, it was evident that the CVR had not sustained any heat or structural damage and good-to-excellent quality audio information was extracted from the recorder normally, without difficulty. A cockpit voice recorder group was convened at the NTSB audio laboratory and a partial transcript was produced.

The accident airplane was equipped with a Honeywell Model 980-4700, 256 Word Solid State Flight Data Recorder, Serial Number 5326. The recorder was in good condition and the data were extracted normally. The Honeywell Solid State Flight Data Recorder (SSFDR) records airplane flight information in a digital form

NTSB Probable Cause

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.