DSB Final Report
Accident: Royal Air Maroc B734 at Amsterdam on Jun 6th 2010, flock of birds, engine fire
The Dutch Onderzoeksraad (Dutch Safety Board DSB) released their final report in Dutch (the English version estimated to be released in the first week of December 2011) concluding the probable causes of the accident were:
1. Shortly after takeoff a collision with a bird caused damage to the left hand engine which reduced the available thrust from that engine by about 45%. The crew decided correctly to return to Amsterdam's Schiphol Airport.
2. The implementation of the return however were not in line with standard operating procedures, the deviations were:
- the execution of a right hand turn at 260 feet AGL with a bank angle of 37.5 degrees instead of continuing straight until minimum safe altitude has been reached and the gear has been retracted
- after the gear had retracted it was extended again at very low altitude
- the undamaged right hand engine was reduced from 94% to 83% N1 instead of utilising its maximum thrust available
These deviations from standard operating procedures meant the aircraft was not able to climb to minimum safe altitude, the crew had difficulty controlling the aircraft and was distracted by a number of audio and visual warnings that resulted from unfinished cockpit procedures.
3. Communication and interaction between the two pilots was not according to international standards established for airline pilots. The immediate right turn led to a marginal remaining flight performance, more difficult tasks and complications, so that both pilots did not execute their duties like handling procedures and checklists in the prescribed manner. This introduced new complications like unnecessary warnings and unstable flight.
4. Training of Royal Air Maroc and Atlas Blue did not prepare flight crew for multiple failures in flight.
- Prior to any refresher training the crew was told which failures were to expect. While this is not unusual, the training could not cater for surprise effects.
- Dealing with multiple faults was included only in the initial training for captains.
- Although the flight crew training manual as well as flight crew operations manual contained procedures and checklists to appropriately address the faults, that occurred during this flight, the managers at Royal Air Maroc and Atlas Blue considered this occurrence a unique event that can not be trained for.
5. There was insufficient account of aircraft in distress below minimum vector altitude taken in studies of necessary actions following the recommendations of the Parliamentary Inquiry Commission investigating the Bijlmer plane crash (editorial note: the crash of El Al's Boeing 747-200 4X-AXG into an apartment block at Bijlmermeer on Oct 4th 1992). Those aircraft will be in the local control zone of Schiphol, the controllers however are without information of high obstacles in the control zone creating an unnecessarily increased risk of collision. This is especially true if flown outside visual meteorologic conditions.
- Research of Dutch Traffic Control following the recommendations of the Parliamentary Inquiry Commission into the Bijlmer crash led to a framework of policies to guide aircraft in distress while flying above the town. The policies establish that the aircraft commander is responsible for flight while air traffic control is responsible to grant all available assistance to the commander, while air traffic control should keep the aircraft as much as possible within the established departure and arrival routes into the runways to limit overflying built up areas. Although the Directorate General for Aviation and Marimite Affairs agreed with these policies, the radar screens of air traffic controller do not depict built up areas.
- Around Schiphol Airport high buildings are virtually everywhere in populated areas. It is therefore not feasable to maneouver in those areas avoiding the obstacles considering the speed and turn radii of aircraft. The aircraft reached a maximum altitude of 730 feet well below the minimum vectoring altitude of 1200 feet. Only two obstacles were depicted on the controller's radar screen, however, there is a high number of obstacles in the control zone that pose a risk to aircraft flying below minimum vectoring altitude, which is especially true if flown outside visual meteorological conditions.
6. The presence of one or more birds with a large mass in the flight trajectory of an aircraft pose a safety risk, especially true for geese because of their high mass and because of them flying in flocks. Most bird strikes occur during takeoff and landing.
7. Research has shown that the responsible parties to control wild life at Schiphol Airport have exhausted their options. Besides frequently closing runways it is necessary to further reduce the risk of bird strikes in the area of responsibilities of other parties.
8. All relevant aviation, agricultural, bird and nature parties recognize the risk of bird strikes and the need to reduce that risk. Despite the concensus on these necessities there is no concensus on the impact of those necessities resulting in different views on the (cost) effective implementation of these measures.
9. The urgency of a flight can not wait for the outcomes of studies of control measures that short term reduce populations of geese as most effective methode to reduce the risk of bird strikes and long term result in a habitat management, detection of birds and deterrence capabilities in view of structural reduction of bird strike risks.
10. Several Non-Government Organisations have joined in the "Geese-7" initiative to reduce and stabilize the populations of various types of geese at a certain size. The implementation of these recommendations is pending awaiting decision by the Ministry of Economy, Agriculture and Innovation.
11. The Ministry of Economy, Agriculture and Innovation, also responsible for flight safety, has not exercised adequate control of bird strike risks.
The Royal Air Maroc Boeing 737-400 CN-RMF with 156 passengers, 4 Royal Air Maroc cabin crew and 2 Atlas Blue pilots, the captain (36, ATPL, 7,540 hours total, 7,200 hours on type) being pilot flying and the first officer (28, ATPL, 2,730 hours total, 2,308 hours on type) being pilot monitoring, departed Schiphol Airport's runway 18L, flaps were set at 5 degrees, engines stabilized at 93.8 and 94.0% N1. The aircraft accelerated through 171 KIAS during rotation (nose up attitude of 6 degrees) and became airborne, at 16 feet AGL the gear was selected up at a speed of 175 KIAS. At that moment the aircraft collided with a flock of geese, which resulted in an immediate loss of all thrust from the left hand engine, the nose landing gear indicated unsafe because of the position of the nose gear did not agree with the selected position. 6 seconds later the aircraft climbed through 140 feet at engine thrust of 45.5% N1 and 93.8% N1, the left engine remained at 45% N1 for the next 4 minutes until shut down. The first officer called out engine #1 was damaged, the call was not responded to by the captain however. The captain remarked that the aircraft was shaking violently and was difficult to control. By himself, without sharing his thoughts with the first officer, he wondered whether both engines had been damaged so that insufficient thrust remained available to sustain flight, therefore he wanted to return immediately considering the decision to return was obvious. He instructed the first officer to select the landing gear down again and declare Mayday, the first officer selected the landing gear down without discussion, then declared emergency.
At a height of 280 feet the commander initiated a right hand turn. Despite the gear being selected down the nose gear continued to indicate unsafe. By the time the first officer completed the Mayday call the aircraft had already reached a bank angle of 21 degrees, the controller recognizing the right turn instructed the aircraft to roll out at 330 degrees and expect vectors for runway 18R. The aircraft reached a maximum bank angle of 37.5 degrees (according to flight data recorder) at an airspeed that reduced from 179 to 156 KIAS. The right hand engine's thrust lever was manually reduced to 83% N1 despite autothrottle being engaged, autothrottle was subsequently disengaged. The aircraft continued to climb slowly reaching 498 feet AGL before descending again at low rate, the GPWS sounded "Don't sink! Don't sink!", the airspeed continued to decrease through 145 KIAS. 60 seconds after initiating the turn the aircraft finally rolled wings level at a heading of 344 degrees.
The captain then requested the first officer to repeat the instructions received from air traffic control and noticed that the nose gear indicated unsafe, the discussion however got interrupted by the purser who called the cockpit reporting the left hand engine was on fire. The captain ignored that message and instead instructed the first officer to tell the cabin crew they were returning to Schiphol. During the next 23 seconds the air traffic controller inquired with the first officer whether the aircraft was able to maintain altitude and whether they could accept vectors, the captain talked to the purser who repeated the left engine was on fire, the GPWS activated a number of times prompting the right thrust lever to be pushed forward until the engine reached 101% N1 and the aircraft began to climb again. After the first officer had finished the transmissions with ATC the captain requested the information to be repeated. The aircraft reached 352 feet and began to descend again, the GPWS again activated "Don't sink!" and "Too Low, Terrain!".
The purser entered the cockpit, the first officer asked him to verify through the peep hole whether the nose gear was extended, then responded to a radio transmission by ATC, which transferred the aircraft onto a discrete frequency (a frequency with no other aircraft on). The purser confirmed the nose gear was down and locked.
The captain increased the right hand thrust lever further to just below firewall, the aircraft began to climb again, the GPWS alerts ceased but nose landing gear warnings now sounded. While the two pilots discussed the new warning ATC issued a heading of 350 degrees to join the downwind for runway 18R and asked whether the aircraft was able to climb, which the crew replied in the negative to.
The gear warning ceased when the aircraft overflew the villages of Vijfhuizen and Haarlem at heights of 380 to 500 feet. When the aircraft was north of these villages ATC issued a new heading of 100 degrees and advised they were 4 miles from touchdown. The captain initiated the turn but rolled out at 065 degrees, the left hand engine was shut down following the memory checklist "Engine Fire or severe damage or separation", while the memory checklist was executed ATC issued heading 160, the instruction was not responded to and was not followed. ATC issued a heading of 210 degrees, the instruction was again not followed, only a minor right turn followed. By that time the crew had completed the memory checklist and found the aircraft north of the aerodrome passing through the extended centerline of runway 18L. ATC issued a heading of 270 to return the aircraft to runway 18R, the crew completed the rest of the checklists concerning the left engine and completed programming of the flight management computer, the aircraft turned through 110 degrees, the first officer inquired with ATC for vectors and was again instructed to turn onto a heading of 270. The crew inquired whether a landing on runway 18L was possible, the approach controller declined because of obstacle clearance (Sony Building) just north of runway 18L. The crew discussed the aircraft was difficult to control, although the engine thrust was constant the airspeed was fluctuating between 160 and 170 knots, the first officer called speed when the airspeed decrased to 156 KIAS. The captain attempted to adjust the right hand thrust lever but noticed it was already at maximum thrust and instructed to firewall the engine for 5 seconds (103.9% N1).
The crew, seeing runway 18C, inquired whether a landing on 18C was possible, which was approved, however, the crew reconsidered and decided to go ahead with the original plan to land on runway 18R, the aircraft was heading at 310 degrees. ATC issued a heading to 215 degrees, the first officer called the instruction out aloud and assisted the captain performing the turn with verbal callouts. The captain captured the localizer manually and flew the ILS with flaps still at 5 degrees. On final approach the captain instructed the first officer to advise cabin crew to not evacuate but prepare for a hard landing. The first officer did not pass that message because the aircraft was already on short final and the first officer called out speeds and sinkrates in order to assist the captain. After main wheel touch down at 175 KIAS the first officer announced the automatic wheel brakes did not engage, the captain instructed to turn the system off, the first officer suggested to keep those nose up as long as possible, followed by a safe touchdown of the nose gear. While the aircraft rolled out the captain again instructed that no evacuation would be done unless there was fire. The aircraft came to a stop on the runway, the right hand engine was shut down.
Emergency services reported no smoke or fire. The right main gear tyres deflated. The passenger disembarked via mobile stairs.
The remains of 24 geese were found in the left main landing gear, the nose landing gear and the electronic compartment.
Examination of the aircraft revealed:
- dents in the underside of the fuselage near the nose of the aircraft
- a dent in the leading edge of the vertical fin
- dents and cracks at the leading edge of the left hand engine's inlet and dents inside the engine
- three fanblades fractured at about midspan damaging all the rest of the fan blades
- the left engine's low and high pressure compressor, the combustion chamber, high pressure turbine guide vanes, high pressure turbine blades, low pressure turbine outlet guide vanes, and first to fourth low pressure turbine stages were all damaged
- on the left side of the left hand engine was soot and oil
- on the fuselage were traces of oil
- the right main gear brakes were jammed
Pollution with engine oil was reported from the village of Harleem, the investigation however could not establish the source of the oil spill stating that the aircraft did not overfly the specific area in question.
Immediately after departure of the Boeing Schiphol operations were advised of a possible bird strike on runway 18L and recovered the remains of 7 dead Canada Geese, weights between 3 and 5 kg (6.6 to 11 lbs) from runway 18L around about the extended centerline of runway 06/24.