|Title:||Gear failure on landing, Douglas DC-9-32, February 1, 1996|
|Micro summary:||This Douglas DC-9-32 experienced a failure of the right main landing gear while landing.|
|Event Time:||1996-02-01 at 1505 CST|
|Publishing Agency:||National Transportation Safety Board (NTSB)|
|Site of event:||Nashville, TN|
|Departure:||Hartsfield-Jackson Atlanta International Airport, Atlanta, Georgia, USA|
|Destination:||Nashville International Airport, Nashville, Tennessee, USA|
|Airplane Type(s):||Douglas DC-9-32|
|Type of flight:||Revenue|
NTSB short summary:
the failure of the right main landing gear shock strut cylinder due to preexisting fractures. Contributing to the accident was: the failure of the operator to inspect the shock strut cylinder for fractures following a previous failure of the torque links, and the absence of specific directives and procedures from the aircraft manufacturer to inspect or replace the shock strut cylinder following torque link failure.
During landing, the right main landing gear shock strut cylinder and piston failed which caused the axle, wheels, and tires to separate. Metallurgical examination showed that the fracture surfaces had been damaged after separation. Two areas on the cylinder fracture face were not at an angle to suggest overstress separation, and ratchet marks were present which usually separate initiation sights on offset fracture planes. The piston fracture surfaces had features typical of overstress separation. The right main landing torque links had failed during landing 312 flight hours before this accident. The torque links, shimmy damper, and piston were replaced at that time; the cylinder was not replaced.
NTSB factual narrative text:
HISTORY OF THE FLIGHT
On February 1, 1996, at 1505 central standard time, a Douglas DC-9-32, N903VJ, registered to and operated by ValuJet Airlines, Inc., as a Title 14 CFR Part 121 scheduled domestic passenger flight, had the right main landing gear fail during landing at Nashville International Airport, Nashville, Tennessee. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The aircraft received substantial damage. The airline transport-rated captain, first officer, 3 flight attendants, and 75 passengers were not injured. The flight originated from Atlanta, Georgia, the same day, about 1430.
The flightcrew stated this was their third flight leg of the day, all of which were flown in this aircraft. The flight from Atlanta to Nashville was uneventful. The first officer was performing flying duties. On approach to Nashville they decided the captain would deploy the ground spoilers after landing because the automatic ground spoiler system was inoperative. The touchdown was normal in the touchdown area of the runway. As the captain deployed the ground spoilers they began to feel vibration and what appeared to be gyration and skipping of the right main gear as if the brakes were on. The vibration got worse as they slowed and the aircraft veered to the right. The first officer used aileron to keep the right wing up and rudder and brakes to maintain directional control. The aircraft came to a stop with the right wing down and the captain directed that all passengers exit via the left front door slide. Rescue personnel arrived and requested that the over wing exits be opened and that passengers exit over the wing.
Information on the captain and first officer is contained in this report in first pilot information and supplement E to this report.
On December 24, 1995, 312 flight hours before the accident, the right main landing gear torque links on N903VJ failed during landing roll at Raleigh, North Carolina. The gear strut piston and axle rotated within the shock strut cylinder. The flightcrew was able to taxi off the runway, and the aircraft was towed to the gate. The right torque links, shimmy damper, and wheel assemblies were changed and the aircraft was ferried to Miami, Florida for further repairs. In Miami, the right gear strut piston was replaced and all lines and wires, including the anti-skid brake system wiring, were repaired. The gear strut cylinder was not changed. The aircraft was returned to service.
Metallurgical examination of the failed torque link and the removed shimmy damper was performed by McDonnell Douglas Aircraft, Materials Process and Engineering Laboratory. The lower torque link arm had failed at the apex bolt/shimmy damper as a result of fatigue cracking. The shimmy damper was found sealed, but almost empty of fluid. (See the attached McDonnell Douglas report)
Flight log discrepancy records obtained from ValuJet Airlines showed that from July 1, 1995 until the Raleigh incident there were numerous occurrences of the right main gear tires being changed and discrepancies with the anti-skid brake system. These occurrences stopped after the repairs following the Raleigh incident. (See the attached records)
Additional aircraft information is contained in this report under aircraft information and in attachments to this report.
Visual meteorological conditions prevailed at the time of the accident. Additional meteorological information is contained in this report under weather information.
The cockpit voice recorder and the digital flight data recorder were removed from the aircraft and forwarded to the NTSB Flight Recorder Laboratory, Washington, D. C., for readout. The cockpit voice recorder was not readout.
The readout indicated that at the moment of apparent touchdown the maximum recorded vertical acceleration value was 1.448 G's, at an airspeed of 134.43 knots. The vertical acceleration data from the twelve previous landings showed that the highest recorded value during the landing sequences was 1.448 G's. (See the attached Factual Report-Digital Flight Data Recorder)
WRECKAGE AND IMPACT INFORMATION
Examination of the runway by FAA, ValuJet, and McDonnell Douglas personnel showed the aircraft touched down at about the 1,500 foot point on the runway. The aircraft traveled about 500 to 1,000 feet before debris separated from the failed right main landing gear. The aircraft stopped on the runway center line at about the 6,500 foot point.
Examination of the separated portion of the right main landing gear showed the gear strut cylinder and piston had failed causing the separation of the axle, wheels, and tires.
Metallurgical examination of the failed right main landing gear cylinder and piston was performed by James F. Wildey II, National Resource Specialist, Metallurgy, NTSB, Washington, D.C. The landing gear cylinder fracture surface had a large majority of the fracture at a 45 degree shear plane, indicative of an overstress separation. No evidence of preexisting fracture areas was found on either of the mating fracture faces. However, two areas of the fracture, located on diametrically opposite sides of the cylinder, were not entirely on a 45 degree plane. The fracture faces had sustained damage as a result of the accident and contained ratchet marks that usually separate initiation sites on slightly offset planes. The landing gear piston fracture faces showed no evidence of preexisting fracture areas. The fracture around the entire circumference of the break was on a 45 degree plane typical of an overstress separation. (See the attached Metallurgist's Factual Report)
The aircraft was released to David L. Gentry, Vice President Maintenance, ValuJet Airlines, on February 6, 1996. Components retained by NTSB for further examination were released to Mr. Gentry on December 18, 1996.
|Learning Keywords:||Operations - Maintenance|
|Systems - Landing Gear|
|Systems - Landing Gear - MLG Collapse|
|Other - Manufacturing Issues|
|Close match:||Main landing gear collapse on landing, Douglas Aircraft Company MD-83, G-DEVR|
|Main landing gear collapse during taxi, Douglas DC-9-32, September 22, 2002|
|Main landing gear failure on landing, Boeing 727-247, July 6, 1997|
|Landing gear collapse, Aircraft Accident Report, New York Airways, Inc. Sikorsky S-61L, N619PA, Pan Am Building Heliport, New York, New York, May 16, 1977|
Accident Reports on DVD, Copyright © 2006 by Flight Simulation Systems, LLC. All Rights Reserved. All referenced trademarks are the property of their respective owners.www.fss.aero