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Center landing gear failure on landing, McDonnell Douglas MD-11,
October 5, 1999
Micro-summary: This McDonnell Douglas MD-11's center landing gear failed on
landing.
Event Date: 1999-10-05 at 0540 EDT
Investigative Body: National Transportation Safety Board (NTSB), USA
Investigative Body's Web Site: http://www.ntsb.gov/
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National Transportation Safety Board
FACTUAL REPORT
AVIATION
NTSB ID: NYC00LA005
Aircraft Registration Number: N606FE
Occurrence Date: 10/05/1999
Most Critical Injury: None
Occurrence Type: Accident
Investigated By: NTSB
Location/Time
Nearest City/Place
NEWARK
Airport Proximity: On Airport
State
NJ
Zip Code
Local Time
Time Zone
07114
0540
EDT
Distance From Landing Facility:
Direction From Airport:
Aircraft Information Summary
Aircraft Manufacturer
Model/Series
Type of Aircraft
McDonnell Douglas
MD-11F
Airplane
Sightseeing Flight: No
Air Medical Transport Flight: No
Narrative
Brief narrative statement of facts, conditions and circumstances pertinent to the accident/incident:
On October 5, 1999, at 0540 Eastern Daylight Time, a McDonnell Douglas MD-11F, N606FE, operated by
Federal Express (FedEx) as flight 1700, was substantially damaged while landing at Newark
International Airport (EWR), Newark, New Jersey. There were no injuries to the two certificated
pilots.
Visual meteorological conditions prevailed for the cargo flight, which had originated from
Indianapolis, Indiana. Flight 1700 was operated on an instrument flight rules flight plan under 14
CFR Part 121.
In interviews, the flight crew reported that the en route phase of flight, and the approach to
Runway 04R occurred without incident. For landing, the airplane was configured with the wing flaps
at 50 degrees, and the auto-brakes were selected to the maximum setting. The captain described the
touch down as "firm" but not hard. He said he wanted to touch down in the first 1,500 feet of the
runway.
As the nose wheel was lowered to the runway, the pilots felt a vibration. They reported that it
felt similar to a deflated tire.
One of the pilots thought he felt the vibration along the
longitudinal axis of the airplane.
During the landing rollout, the center landing gear unsafe
light illuminated.
As the airplane was clearing the runway, the central aural warning system
(CAWS) generated a voice warning about unsafe landing gear.
After the airplane exited the runway, it crossed Runway 04L, and was stopped on a parallel taxiway.
The master caution light was illuminated, and the reservoir for hydraulic system # 3 was empty.
After referencing with the checklist, the captain elected to taxi the airplane straight ahead at a
slow speed, toward the FedEx ramp area. The airplane was stopped after it entered the ramp area,
and the airplane was towed to the gate.
Examination of the airplane revealed that the center landing gear, which normally was angled 15
degrees forward of vertical, was angled about 45 degrees aft of vertical. The upper lugs of the
lower drag brace were fractured, and the cap on the center landing gear retraction cylinder had
been pulled out.
Tire marks were found on the aft fuselage above the tires of the center landing
gear.
The aft side of the landing gear strut was pushed against the aft bulkhead of the center
landing gear well.
The metal was deformed and torn in the area that had contact with the center
landing gear strut.
To ferry the airplane for repairs, the center landing gear strut was depressurized and compressed
to rotate the strut into the center landing gear wheel well. The center landing gear strut
servicing was not recorded prior to depressurization and compression of the strut.
A check with Boeing Commercial Airplanes (BCA) - Long Beach Division (formerly the
McDonnell-Douglas Aircraft Corp.), revealed five previous events where the center landing gear had
entered a divergent oscillation along the longitudinal axis of the airplane, the lower drag brace
FACTUAL REPORT - AVIATION
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National Transportation Safety Board
FACTUAL REPORT
AVIATION
Narrative
NTSB ID: NYC00LA005
Occurrence Date: 10/05/1999
Occurrence Type: Accident
(Continued)
had failed at the
subsequent loss of
last two occurred
upon the findings
landing gear wheel
the anti-skid cycle
the center landing
the suggested fixes.
upper attach lugs, and the retraction cylinder had been pulled apart with the
the number 3 hydraulic system. The first three were in-service events. The
in instrumented airplanes that were exploring the first three events.
Based
from these events, the anti-skid control box was modified to prevent center
brake application until the nose landing gear was on the ground. In addition,
rate was modified to avoid the cyclic range related to the natural frequency of
gear. McDonnell-Douglas issued all operators letters describing the events and
The accident airplane was delivered to FedEx in 1993. The airplane and center landing gear had
accumulated 22,055:59 hours, and 5,120 cycles.
In addition, the airplane carried the modified
anti-skid control box.
The failed lower drag brace, P/N AYG 7229-1, S/N AP 181, was forwarded to the Safety Board
Materials Laboratory for examination.
According to the metallurgists factual report, "...all
portions of the fracture surface, including the portions on the reverse slat planes, consisted of
elongated ductile dimples, typical of overstress separation...."
The hardness of material was checked and found to average HRC 53.9.
should be between HRC 53 and HRC 55.
According to BCA, the hardness
The Digital Flight Data Recorder (DFDR) was examined by the Safety Board Vehicle Recorder Division.
According to the specialist's factual report, the initial touchdown produced a g-load of +1.39g's,
which then reduced to +0.6g's, and then increased again to +1.59g's. The two peaks were separated
by about 1.6 seconds.
The DFDR also revealed that spoiler extension was initiated, and brake
pressure to the left and right main landing gears had increased prior to nose wheel touchdown. No
information was available about the application of brake pressure to the center landing gear
brakes, as that information was not recorded.
Further, the DFDR report revealed that main landing gear brake pressure started to increase about
2.5 seconds after main landing gear touchdown. At 3.5 seconds after main landing gear touchdown,
the nose wheel strut was compressed. At 5.75 seconds after main landing gear touchdown, a vertical
oscillation of four cycles, with a duration of 1.25 seconds was recorded. During the last cycle,
the vertical acceleration momentarily decreased to 0.48gs, and then returned to 1.03g's. The
longitudinal acceleration, which had decreased to a -0.3 to -0.4g's momentarily further decreased
to -0.874g's at the same time as the vertical acceleration peak of 0.48g's, and then returned to
-0.4g's.
After the peaks on the vertical and longitudinal accelerations, the g-readings returned
to their previous readings as the airplane continued to decelerate.
The wheel speed sensors and hydraulic brake manifolds were removed from the two wheels of the
center landing gear for further examination. The testing was conducted under the supervision of
the Federal Aviation Administration (FAA). According to the report of the testing:
"...All units passed the functional test. The Wheel Speed Sensors and Valve Modules functioned as
intended on the Aircraft. Although the fluid showed significant signs of contamination it did not
appear to have impacted the performance of the units....."
The electronic anti-skid control unit was also examined and passed a functional test.
Following the October 5, 1999, event, FedEx initiated a test program. The test program included
the installation of a high-speed recorder onboard the airplane. In addition, the lower drag brace
on the center landing gear was instrumented to record strain, both compression and tension, during
landing.
The test loads were measured on an airplane with a high time center landing gear, which
was approaching its scheduled gear removal period. Then the tests were repeated on an airplane
with a freshly overhauled center landing gear.
FACTUAL REPORT - AVIATION
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National Transportation Safety Board
FACTUAL REPORT
AVIATION
Narrative
NTSB ID: NYC00LA005
Occurrence Date: 10/05/1999
Occurrence Type: Accident
(Continued)
According to a memo from the person at FedEx who supervised the testing:
"...The maximum load measured on the CLG [center landing gear] was well below the strength of the
Lower Drag Brace.
Even though the data was not as reliable after the gear change, there does not
appear to be any differences in the loads measured on a new gear and the loads on a high-time
gear...There were a few recorded landings where the CLG exhibited an oscillation after touchdown
that appears to be unrelated to the brake application. Due to inoperative data parameters, the
cause of this oscillation is unknown...The data did not exhibit any high loads that approached the
limit load of the drag brace....."
According to a representative from Boeing who reviewed the FedEx report:
"The brake control system performed as expected.
In response to brake applications, and tire
skids, the center landing gear showed normal periods of fore-aft motion at its natural frequency,
with no tendency to diverge as a result of anti-skid brake control inputs."
Further, the report from FedEx stated that in October and November 1999, during the overhaul of two
other MD-11 center landing gears, the vendor reported that the lower drag brace from both landing
gears had elongated lug holes.
However, there was no supporting data to confirm how the lugs
became elongated.
According to a representative of Boeing, elongation of the lugs on the lower drag brace could occur
for reasons other than the divergent longitudinal cyclic oscillation. Due to the forward slope of
the center landing gear, any ground event that applied a fore or aft force to the center landing
gear would apply either compression or tension loads respectively to the lower drag brace.
FACTUAL REPORT - AVIATION
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NTSB ID: NYC00LA005
National Transportation Safety Board
FACTUAL REPORT
AVIATION
Occurrence Date: 10/05/1999
Occurrence Type: Accident
Landing Facility/Approach Information
Airport Name
Airport ID:
NEWARK INTERNATIONAL
EWR
Runway Used
Airport Elevation
11 Ft. MSL
4R
Runway Length
Runway Width
9980
150
Runway Surface Type: Asphalt
Runway Surface Condition: Dry
Type Instrument Approach: ILS-complete
VFR Approach/Landing: None
Aircraft Information
Aircraft Manufacturer
Model/Series
McDonnell Douglas
MD-11F
Serial Number
48602
Airworthiness Certificate(s): Transport
Landing Gear Type: Retractable - Tricycle
Homebuilt Aircraft? No
Number of Seats: 5
Engine Type:
Certified Max Gross Wt.
633000 LBS
Engine Manufacturer:
Turbo Fan
GE
Number of Engines: 3
Model/Series:
Rated Power:
CF6-80C2
60240 LBS
- Aircraft Inspection Information
Date of Last Inspection
Type of Last Inspection
Continuous Airworthiness
Time Since Last Inspection
Airframe Total Time
34 Hours
09/1999
22055 Hours
- Emergency Locator Transmitter (ELT) Information
ELT Installed? Yes
ELT Operated? No
ELT Aided in Locating Accident Site?
Owner/Operator Information
Street Address
Registered Aircraft Owner
1100 N MARKET ST.
WILMINGTON TRUST COMPANY
State
City
WILMINGTON
DE
Zip Code
19890
Street Address
Operator of Aircraft
3131 DEMOCRAT ROAD
State
City
FEDEX
MEMPHIS
TN
Zip Code
38118
Operator Designator Code: FDEA
Operator Does Business As:
- Type of U.S. Certificate(s) Held:
Air Carrier Operating Certificate(s): Supplemental
Operating Certificate:
Operator Certificate:
Regulation Flight Conducted Under: Part 121: Air Carrier
Type of Flight Operation Conducted: Non-scheduled; Domestic; Cargo
FACTUAL REPORT - AVIATION
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NTSB ID:
National Transportation Safety Board
FACTUAL REPORT
AVIATION
Occurrence Date: 10/05/1999
Occurrence Type: Accident
First Pilot Information
Name
On File
Sex: M
City
State
On File
On File
Principal Profession: Civilian Pilot
Seat Occupied: Left
Certificate(s):
Airline Transport; Commercial; Flight Engineer
Airplane Rating(s):
Multi-engine Land; Single-engine Land
Date of Birth
Age
53
Certificate Number:
Rotorcraft/Glider/LTA: None
Instrument Rating(s): Airplane
None
Instructor Rating(s):
Type Rating/Endorsement for Accident/Incident Aircraft? Yes
Medical Cert. Status:
Medical Cert.: Class 1
This Make
and Model
All A/C
- Flight Time Matrix
Current Biennial Flight Review?
12000
Total Time
Date of Last Medical Exam: 09/1999
Airplane
Airplane
Single Engine
Mult-Engine
Instrument
Night
Actual
Rotorcraft
Lighter
Glider
Than Air
Simulated
4621
2315
Pilot In Command(PIC)
Instructor
84
23
Last 90 Days
Last 30 Days
3
Last 24 Hours
Seatbelt Used? Yes
Shoulder Harness Used? Yes
Toxicology Performed? No
Second Pilot? Yes
Flight Plan/Itinerary
Type of Flight Plan Filed: IFR
Departure Point
State
Airport Identifier
Departure Time
Time Zone
INDIANAPOLIS
IN
IND
0424
EDT
Destination
State
Airport Identifier
EWR
Same as Accident/Incident Location
Type of Clearance: IFR
Type of Airspace:
Class B
Weather Information
Source of Briefing:
Company
Method of Briefing:
FACTUAL REPORT - AVIATION
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NTSB ID: NYC00LA005
National Transportation Safety Board
FACTUAL REPORT
AVIATION
Occurrence Date: 10/05/1999
Occurrence Type: Accident
Weather Information
WOF ID
Observation Time
Time Zone
EWR
0550
EDT
WOF Elevation
WOF Distance From Accident Site
0 NM
11 Ft. MSL
Sky/Lowest Cloud Condition: Unknown
0 Ft. AGL
Lowest Ceiling: Overcast
1500 Ft. AGL
9 °C
Temperature:
Wind Speed: 12
Visibility (RVR):
7 °C
Dew Point:
Ft.
10
Visibility:
0 Deg. Mag.
Condition of Light: Night/Dark
SM
Wind Direction: 10
Altimeter:
Density Altitude:
30.00
"Hg
0
Ft.
Weather Condtions at Accident Site: Visual Conditions
Gusts:
0
Direction From Accident Site
0
Visibility (RVV)
SM
Intensity of Precipitation: Unknown
Restrictions to Visibility: None
Type of Precipitation:
None
Accident Information
Aircraft Damage: Substantial
Aircraft Fire: None
Aircraft Explosion None
Classification: U.S. Registered/U.S. Soil
- Injury Summary Matrix
Fatal
Serious
None
Minor
TOTAL
First Pilot
1
1
Second Pilot
1
1
2
2
Student Pilot
Flight Instructor
Check Pilot
Flight Engineer
Cabin Attendants
Other Crew
Passengers
- TOTAL ABOARD Other Ground
- GRAND TOTAL -
0
0
0
0
0
0
0
2
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National Transportation Safety Board
FACTUAL REPORT
AVIATION
NTSB ID: NYC00LA005
Occurrence Date: 10/05/1999
Occurrence Type: Accident
Administrative Information
Investigator-In-Charge (IIC)
ROBERT L. HANCOCK
Additional Persons Participating in This Accident/Incident Investigation:
NATE GLINBIZZI
FAA FSDO
TETERBORO, NJ
ALAN W RAY
FEDEX
MEMPHIS, TN
FACTUAL REPORT - AVIATION
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