|Title:||Retraction of gear on ground, Boeing 747-121|
|Micro summary:||Following heavy maintenance and a return to service, a miscommunication results in a partial gear retraction and the airplane settling on its tail.|
|Event Time:||1996-06-15 at 1744 UTC|
|Publishing Agency:||Aircraft Accident Investigation Board (AAIB)|
|Publishing Country:||United Kingdom|
|Diversion Airport:||Cardiff International Airport, Cardiff, Wales|
|Site of event:||Cardiff-Wales Airport|
|Departure:||Cardiff International Airport, Cardiff, Wales|
|Airplane Type(s):||Boeing 747-121|
|Type of flight:||Engineering Test Flight|
|Diverted to:||Cardiff International Airport, Cardiff, Wales|
|Executive Summary:||The aircraft had been on a 'C' check and the Estimated Time to Service (ETS) had been delayed from the previous day, due to the workload on the aircraft. It was rescheduled for 1800 hrs local time (L) on the 15th. The task continued to run late, however the day shift fully expected to deliver the aircraft for service as scheduled, just before the end of their shift at 1800 hrs L, and so no 'handover' had been prepared. During this period the aircraft was under the control of the day shift aircraft controller. At about 1730 hrs L the nightshift began to arrive and having arrived early, began to assist the dayshift. |
Prior to the arrival of the night shift, there had been some discussion concerning the landing gear pins. The pins, which had been removed prior to the pushback from the hangar, were re-fitted as required for some work card items which were still outstanding. The workcard items outstanding were, in particular, a function check of the landing gear module and nose gear alternate extension checks. In addition, the tug driver was unwilling to push back unless the nose gear pins were in place. At about 1810 hrs L the aircraft was pushed back from the hangar to the apron outside. As the aircraft was being pushed back, an engineer on the night shift team saw the pins in place and queried with two of the day shift controllers whether the pins were the property of the operator or the maintenance organisation. He was advised that they did not belong to the operator, and understood the reply to mean that they could be removed after the aircraft was parked. It is not clear how this understanding arose, however the night shift were generally unaware of the outstanding work card
To expedite matters, the loading of freight began and the three members of the operator's flight crew boarded the aircraft in readiness for it to be handed over to them. Although the flightcrew were on board, the Certificate of Release to Service (CRS) had not been signed and the flight crew were not in command of the aircraft. They were, however, on board with the intention of flight as it was understood that, once the CRS was signed the engineers would leave the aircraft and the flight crew would take command. The day shift team leader was seated in the left handseat and was in contact with an engineer on the ground by headset. A number of other engineering personnel were around the aircraft, including several night shift personnel Prior to carrying out the landing gear functions, the team leader asked the engineer on the headset to confirm that all the landing gear pins were in place. The engineer on the headset visually checked that all the landing gear pins were in place and advised the team leader on the flight deck accordingly.
During this time two engineers on the night shift were proceeding with the removal of the pins from the main and body landing gears. They then attempted to remove the nose gear pins, but could not reach them unaided. The removed main gear pins were deposited on the ground by the nose gear while an engineer went to obtain a tool to reach the nose gear pins. Even though some discussion with the engineer on the headset occurred concerning the landing gear doors, there was no effective communication between the two groups concerning the landing gear pins.
The team leader, on the flight deck, then selected the landing gear to UP. At this point a 'shudder' was felt and some discussion ensued as to the cause, which was initially attributed to the freight being loaded. However the team leader was not satisfied with this explanation and he then selected the landing gear lever to DOWN. Further inspection showed that both body gears were out of downlock and that there were no pins in the wing or body gears. The pins were then seen lying by the nosewheel. From the associated statements it was clear that the engineer on the headset was surprised (and "horrified") to see that the pins had been removed, and the engineers who had removed the pins were equally surprised that landing gear functions were being performed. The aircraft was shut down and the situation assessed;several attempts were made to put the body gears into downlock. The wing gear pins were re-fitted, however the body gear pins could not be fitted with the gears out of lock.
|Learning Keywords:||Operations - Loading|
|Operations - Maintenance|
|Operations - Upset - Uncommanded or excessive Pitch|
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