Jetstream 4100, G-MAJJ, 28 May 2012

17� Crown copyright 2013 AAIB Bulletin: 3/2013 G-MAJJ EW/C2012/05/04 ACCIDENT Aircraft Type and Registration: Jetstream 4100, G-MAJJ No & Type of Engines: 2 Garrett Airesearch TPE331-14GR-807H turboprop engines Year of Manufacture: 1993 (Serial no: 41024) Date & Time (UTC): 28 May 2012 at 1456 hrs Location: Brussels National Airport, Belgium Type of Flight: Commercial Air Transport (Passenger) Persons on Board: Crew - 3 Passengers - 1 Injuries: Crew - None Passengers - None Nature of Damage: Rear pressure bulkhead of nose landing gear bay, lower fuselage skin and keel plate aft of nose landing gear bay Commander’s Licence: Air Transport Pilot’s Licence Commander’s Age: 40 years Commander’s Flying Experience: 5,638 hours (of which 1,700 were on type) Last 90 days - 70 hours Last 28 days - 15 hours Information Source: AAIB Field Investigation Synopsis During pushback, the aircraft came to an abrupt halt and the shear pin on the towbar broke. Subsequently damage to the keel area of the aircraft and to the pressure bulkhead at the rear of the nose landing gear bay was discovered. The aircraft had operated for eight sectors since the pushback. History of the flights At approximately 1455 hrs on 28 May 2012 G-MAJJ was pushed back from Stand 209 on Apron 2 South at Brussels National Airport. The pushback proceeded normally until the aircraft came to an abrupt halt and the shear pin on the towbar broke. The captain asked the ground agent to look to see if there were any signs of damage and, when the agent said that he could see none, the captain decided to continue with the flight. The aircraft flew uneventfully to Southampton Airport and later operated to Aberdeen Airport, its last sector of the day. During the climb out of Southampton Airport, the crew experienced a “low, steady thumping” below the cockpit after the landing gear was raised, which continued until the aircraft climbed through approximately FL70. After landing at Aberdeen Airport, the captain reported to the engineer “a clunking sound from the nosewheel after take off.” The engineer 18� Crown copyright 2013 AAIB Bulletin: 3/2013 G-MAJJ EW/C2012/05/04 recorded this defect in the aircraft’s Technical Log and on investigation found the nosewheel misaligned, which he corrected in accordance with the maintenance manual 1 . A 5-Day Service Check was completed during the evening of 28 May 2012. On 29 May 2012, G-MAJJ operated five sectors. On the second and third sectors, the crew noticed a “clunk” in the climb between FL50 and FL100 that sounded like “metal stretching” beneath their feet or “crushing a beer can”. On the fourth sector of the day, a new crew felt a clunk through their feet as the aircraft climbed between FL50 and FL60 although they did not hear anything. On landing at Aberdeen Airport, the captain carried out a visual inspection to look for obvious signs of damage but saw none. On the return leg to Southampton Airport, the crew heard a clunking sound as the nose landing gear lowered. The captain reported this to Line Maintenance Control (LMC) after landing. No defects were reported in the Technical Log following any of the flights on 29 May 2012. The aircraft’s next flight was from Southampton Airport to Aberdeen Airport on 30 May 2012. At approximately 5,000 feet during the climb, a clunking noise was heard by the crew. As with all the preceding sectors flown since the pushback at Brussels, there were no other indications or handling difficulties and the aircraft continued and landed normally at Aberdeen. After landing it was discovered that the aircraft had suffered damage to its forward keel and to the pressure bulkhead at the rear of the nose landing gear bay. Footnote 1 The nosewheels rotate together with the axle and any misalignment of the wheels can cause a strong vibration when the wheels lift off the ground during takeoff. Information from witnesses Pilot of the aircraft during the pushback The captain of the aircraft during the pushback at Brussels reported that he and his co-pilot were running through the after-start checks during the pushback. The pushback was normal until the aircraft came to a halt “almost as if we had pushed back onto chocks.” He spoke to the ground agent on the headset and asked him to look for any signs of damage but the ground agent said he could not see any. The pilot decided to continue with the flight because the event did not feel serious at the time. He reported that there were no steering problems during the taxi out to the runway and no other symptoms during the flight to Southampton Airport. He believed that neither he nor his co-pilot had applied the brakes. A video of the event, obtained from a CCTV camera at the airport, showed no evidence of an external cause for the abrupt stop. The driver of the tug The driver of the tug was a qualified pushback operator but was working on this type of aircraft for the first time. He did not notice any defects with the towbar while coupling it to the aircraft nose gear. He stated that he kept the aircraft in a substantially straight line, with only minor corrections, while pushing it backwards at slow speed. After about 100 m, he saw the nosewheel of the aircraft lift up and almost immediately drop back downwards with the nose towards the right. The shear pin on the towbar head had broken leaving the towbar head to pivot freely horizontally. The nosewheel was turned completely to one side as were the towbar and the towbar head. There were no obstacles in the path of the aircraft and the driver had no idea why it had come to such an abrupt halt. 19� Crown copyright 2013 AAIB Bulletin: 3/2013 G-MAJJ EW/C2012/05/04 The ground agent on the headset During the pushback, the ground agent was in contact with the pilot through his headset. One engine was started with the aircraft on the stand and the other was started during the pushback. He reported that he was watching the engine start when suddenly the nose of the aircraft moved to his right, the nosewheel turned and the towbar was no longer aligned with the aircraft. The shear pin on the towbar had broken and the towbar head had pivoted. The ground agent told the pilot what had happened and had a look at the nose gear himself but did not notice any damage. The pilot decided that it would not be necessary to return to stand for further investigation. Pushback equipment The pushback tractor was a Schopf Maschinenbau GmbH F100 Tug, which has an empty weight of 14,000 kg. The towbar was of a type approved for this aircraft and was fitted with the appropriate connecting head. The towbar incorporated a shear pin to protect the aircraft from excessive loads. The shear pin is designed to transmit normal loads but will break if a pre-determined load value is exceeded (Figure 1). If the shear pin breaks due to an excessive load in line with the towbar, the load will initially be removed but it will be reapplied as soon as the pivot bolt reaches the end of its slot in the towbar head. Spare shear pin for reference Shear pin Tow bar Connection to aircraft Tow bar head Pivot boltSlot in head Figure 1 Detail of towbar head, shear pin and head attachment to towbar 20� Crown copyright 2013 AAIB Bulletin: 3/2013 G-MAJJ EW/C2012/05/04 The aircraft manufacturer’s Aircraft Maintenance Manual (AMM), Towing and Taxiing, 09-10-00 page 209 states: ‘The tractor used should weigh between 5000 lb and 10000 lb’ (approximately 2,300 kg and 4,500 kg). The ground handling agent did not have access to the AMM but followed the instructions laid down in the operator’s Ground Operations Manual (GOM) and Ground Handling Instructions which, at the time of this event, did not refer to the type of tractor to be used. Pushback procedures The operator’s GOM contains pushback procedures for ground handlers. It states: ‘If a shear pin breaks on pushback and the towbar remains attached, the tug should be slowed and stopped, and the flight deck infor

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Jetstream 4100, G-MAJJ, 28 May 2012

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