Event Details

Title:Uncommanded roll to the right on takeoff, Boeing 737-300, January 23, 1995
Micro summary:This Boeing 737-300 experienced an uncommanded roll to the right.
Event Time:1995-01-23 at 2115 MST
File Name:1995-01-23-US.pdf
Publishing Agency:National Transportation Safety Board (NTSB)
Publishing Country:USA
Report number:LAX95IA086
Site of event:Albuquerque, NM
Departure:Albuquerque International Sunport, Albuquerque, New Mexico, USA
Destination:McCarran International Airport, Las Vegas, Nevada, USA
Airplane Type(s):Boeing 737-300
Flight Phase:Takeoff
Operator(s):America West Airlines
Type of flight:Revenue
Serious Injuries:0
Other Injuries:0
Executive Summary:

NTSB short summary:

maintenance personnel inadvertently overservicing the left main landing gear strut with nitrogen that, during rotation with the aircraft weight on the strut reduced, gave the pilots a rolling sensation to the right.

NTSB synopsis:

This aircraft was involved in four momentary uncommanded rolls to the right during rotation. In each instance, the pilot was able to quickly correct the situation and continue the flight without further problems. Numerous attempts by maintenance personnel to identify the problem and to resolve the issue were unsuccessful. After the fourth incident, the left main landing gear strut was found to have been overserviced with nitrogen. This additional pressure to the strut would suddenly lift the left wing during rotation when the weight of the aircraft on the landing gear is reduced, thus giving the pilots a rolling sensation to the right. The strut was reserviced with oil and nitrogen and the aircraft has been returned to service with no more occurrences. The upper wing surface panel support rod broke due to high-cycle fatigue and was not considered a factor in these instances.

NTSB factual narrative text:

On January 23, 1995, at 2115 mountain standard time, the pilot of a Boeing 737-300, N155AW, experienced an uncommanded roll to the right during takeoff from runway 26 from Albuquerque(ABQ), New Mexico. The aircraft, owned by America West Airlines, Inc., and operated under 14 CFR Part 121 as flight 959, was not damaged, nor were there any injuries to the crew or passengers. Visual meteorological conditions existed at the time.

After this incident, this aircraft was involved in three other separate uncommanded momentary rolls to the right during rotation at Las Vegas, Nevada; Boston, Massachusetts; and Columbus, Ohio. For each occurrence, the pilots were able to correct the situation and continue with the respective flights.

After the initial notification from America West Airlines on the first two incidents, the flight data recorder and a broken upper wing surface support rod from the fixed panel inboard of the No. 6 spoiler, were removed and sent to the National Transportation Safety Board Metallurgical Laboratory for analysis. Maintenance personnel adjusted the spoilers and ailerons. The aircraft was test flown and returned to service.

The third incident occurred two days later during rotation at Boston. The aircraft continued to Columbus, where it was grounded. The aircraft was returned to Phoenix, Arizona, on a ferry flight for further examination. During the departure from Columbus, the fourth incident occurred.

A verbal report from the America West 737 fleet manager on March 2, 1995, indicated that the left main landing gear strut had been overserviced with nitrogen gas over a period of time. According to the fleet manager, when the aircraft weight on the main landing gear is reduced during rotation, the overpressurized left strut lifts the left wing into the air, giving the pilots a rolling sensation to the right. The left main landing gear strut was reserviced with oil and nitrogen, multiple test flights were flown with no repeat of the problem, and the aircraft has since been returned to service.


The aircraft had 19,943 cycles as of January 26, 1995. A "C" check was done on August 25, 1994, and an "A-9" check was completed on January 13, 1995.

The metallurgical examination showed that the support rod fractured at an attachment to one of the clevis fittings. The separation occurred in line with the furthest inboard rivet. Fracture matching disclosed that a portion of the rod shaft separation did not mate with the shaft fracture that was attached to the clevis fitting. Scanning electron microscopic (SEM) viewing of the cleaned fracture disclosed evidence of striations indicative of high-cycle fatigue cracking over most of the fracture surface. The metallurgist report is attached for more information.
Learning Keywords:Operations - Maintenance
Operations - Upset - Uncommanded or excessive Roll
Systems - Flight Controls - Wing Panel Separation


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