NOAR L410 near Recife on Jul 13th 2011, lost height
Last Update: July 28, 2013 / 19:21:59 GMT/Zulu time
Incident Facts
Date of incident
Jul 13, 2011
Classification
Crash
Aircraft Registration
PR-NOB
Aircraft Type
Let L-410 Turbolet
ICAO Type Designator
L410
Human Factors
Medical Aspect
- Anxiety
The perception of danger especially by the first officer affected the communication between the pilots and may have inhibited a more assertive attitude, which could have led to an emergency landing on the beach, minimizing the consequences of the accident.
Psychological Aspect
- Attitude
Operational decisions during the emergency may have resulted from the high confidence level, that the captain had acquired in years of flying and experience in aviation, as well as the captain's resistance to accept opinions different to his own.
- Emotional state
According to CVR recordings there was a high level of anxiety and tension even before the abnormal situation. These components may have influenced the judgment of conditions affecting the operation of the aircraft.
- Decision making
The persistence to land on runway 36 during the emergency, even though the first officer recognized the conditions no longer permitted to reach the airport, reflects misjudgment of operational information present at the time.
- Signs of stress
The unexpected emergency at takeoff and the lack of preparation for dealing with it may have invoked a level of stress with the crew, that negatively affected the operational response.
Psychosocial Information
- Interpersonal relations
The historical differences between the two pilots possibly hindered the exchange of information and created a barrier to deal with the adverse situation.
- Dynamic team
The present diverging intentions of how to proceed clearly show cooperation and management issues in the cockpit. This prevented the choice of best alternative to achieve a safe emergency landing when there were no options left to reach the airport.
- Company Culture
The company was informally divided into two groups, whose interaction was impaired. It is possible that this problem of interaction continued into the cockpit management during the in flight emergency, with one pilot belonging to one and the other to the other group.
Organizational Information
- Education and Training
Deficiencies of training provided by the operator affected the performance of the crew, who had not been sufficiently prepared for the safe conduct of flight in case of emergency.
- Organizational culture
The actions taken by the company indicate informality, which resulted in incomplete operational training and attitudes that endangered the safety.
Operational Aspects
According to data from the flight recorder the rudder pedal inputs were inadequate to provide sufficient rudder deflection in order to compensate for asymmetric engine power.
The values of side slip reached as result of inadequate rudder pedal inputs penalized the performance of the aircraft preventing further climb or even maintaining altitude.
In the final phase of the flight, despite the airspeed decaying below Vmca, despite continuous stall warnings and despite calls by the first officer to not hold the nose up in order to not stall the captain continued pitch up control inputs until the aircraft reached 18 degrees nose up attitude and entered stall.
- Crew Coordination
The delay in retracting the landing gear after the first instruction by the captaint, the instruction of the captain to feather the propeller when the propeller had already been feathered as well as the first officer's request the captain should initiate the turn back when the aircraft was already turning are indicative that the crew tasks and actions were not coordinated.
Emergency procedures provided in checklists were not executed and there was no consensus in the final moments of the flight, whether the best choice (least critical option) was to return to the runway or land on the beach.
- Oblivion
It is possible in response to the emergency and influenced by anxiety, that the crew may have forgotten to continue into the 3rd segment of the procedure provided for engine failure on takeoff at or above V1 while trying to return to the airfield shortly after completion of the 2nd segment while at 400ft.
- Pilot training
The lack of training of engine failures on takeoff at or above V1, similar as is recommended in the training programme, led to an inadequate pilot response to the emergency. The pilots did not follow the recommended flight profile and did execute the checklist items to be carried out above 400 feet.
- Pilot decisions
The pilots assessed that the priority was to return to land in opposite direction of departure and began the turn back at 400ft, which added to the difficulty of flying the aircraft. At 400 feet the aircraft maintained straight flight and a positive rate of climb requiring minor flight control inputs only, which would have favoured the completion of the emergency check list items in accordance with recommendations by the training programme.
After starting the turn the crew would needed to adjust all flight controls to maintain intended flight trajectory in addition to working the checklists, the turn thus increased workload. It is noteworthy that the remaining engine developed sufficient power to sustain flight.
- Supervision by Management
The supervision by management did not identify that the training program provided to pilots failed to address engine failure above V1 while still on the ground and airborne.
It was not identified that the software adopted by the company to dispatch aircraft used the maximum structural weight (6,600kg) as maximum takeoff weight for departures from Recife.
On the day of the accident the aircraft was limited in takeoff weight due to ambient temperature. Due to the software error the aircraft took off with more than the maximum allowable takeoff weight degradating climb performance.
Mechanical Aspects
- Aircraft
Following the hypothesis that the fatigue process had already started when the turbine blade was still attached to the Russia made engine, the method used by the engine manufacturer for assessment to continue use of turbine blades was not able to ensure sufficient quality of the blade, that had been mounted into position 27 of the left hand engine's Gas Generator Turbine's disk.
- Aircraft Documentation
The documentation of the aircraft by the aircraft manufacturer translated into the English language did not support proper operation by having confusing texts with different content for the same items in separate documents as well as translation errors. This makes the documentation difficult to understand, which may have contributed to the failure to properly implement the engine failure checklists on takeoff after V1.
An especially concerning item is the "shutdown ABC (Auto Bank Control)", to be held at 200ft height, the difference between handling instructed by the checklist and provided by the flight crew manual may have contributed to the non-performance by the pilots, aggravating performance of the aircraft.
CENIPA reported the captain (ATPL, 15,457 hours total, 957 hours on type) was pilot flying, the first officer (CPL, 2,404 hours total, 404 hours on type) was pilot monitoring. The aircraft had accumulated 2,126 flight hours in 3,033 flight cycles and was not yet due for first P4 overhaul at 2400 flight hours. The left hand engine (M601E) had accumulated 2,126 flight hours and had flown 21 hours since last check. The right hand engine had accumulated 6,154 flight hours and was 539 hours past last overhaul and 21 hours since last P2 inspection.
The captain briefed before engine start, that in case they had an engine failure above V1 and the landing gear not yet retracted, considering the length of the runway of 3100 meters, they might still abort takeoff and put the aircraft down onto the runway again.
The aircraft was accelerating for takeoff from Recife's runway 18 when the left hand engine failed and lost power just at rotation. The first officer called to reject takeoff three times, the commander responded there was insufficient room to stop the aircraft and instructed to retract the gear. The first officer complied with that instruction only 50 seconds later after the captain had repeated the instruction for the 4th time. The captain instructed the first officer to request a return to runway 30 three times without realizing the runway layout of Recife had runways 18 and 36. The first officer advised ATC they would return to runway 36. The captain instructed the first officer to feather the left hand propeller, the propeller had already feathered however.
Automatic warnings "Do not sink!" and "Too low, Terrain" sounded. The captain again requested the left hand propeller to be feathered, the first officer responded the propeller was already feathered. The first officer requested to return to the aerodrome, the commander responded he was already turning.
The stall warning activated, the first officer requested to lower the nose, GPWS sounded "Do not sink!" and "Too low! Terrain". The first officer called "120 feet", the stall warning activated again. The first officer again requested to lower the nose and asked whether the captain wanted to land on the beach which met a categoric no. The first officer radioed they would land on the beach, the captain again denied, the first officer argued they would hit the top of the buildings, the stall warning activated continuously for 19 seconds, "Too Low! Terrain" and "Do not Sink!" sounded and the aircraft impacted the beach.
Visual inspection of the wreckage confirmed the left hand engine was not operating at the time of impact, the left hand propeller was feathered. The right hand engine was operating at high power. Flaps were still set at 18 degrees.
A closer inspection of the left hand engine showed the turbine blade number 27 had fractured as result of fatigue causing substantial internal engine damage downstream.
The investigation found, that the English checklists accurately provided for an engine failure on takeoff, the translated flight crew manual in Portugese however incorrectly called that scenario engine failure in flight. The operator's speed parameters for one engine out operation was found not in agreement with the manufacturer's documentation. A Portugese checklist was found on sister aircraft PR-NOA. A test conducted with that checklist, failing an engine on takeoff, could not be completed within 2 minutes and was not satisfactory with many discrepancies identified. It was found, that the checklist produced for certification was the English one provided by the manufacturer, not the company checklist. The investigation could not determine which checklists were on board of the accident aircraft however as all documents had burned down.
According to aircraft performance charts the aircraft was limited to a maximum takeoff weight of 6,430kg for the accident departure due to temperature, rather than 6,600kg. The manifest for the flight however showed a maximum takeoff weight possible of 6,600 kg. The actual takeoff weight was computed at 6,561kg, still 131kg above maximum permitted takeoff weight.
The left hand engine of the L410 is the critical engine, it's failure requires a more pronounced rudder pedal input than with the right hand engine failed. According to certification criteria the aircraft must maintain straight and level flight at minimum control speed Vmca (84 knots for the accident flight) even at a side slip angle of 5 degrees, the incident aircraft however reached side slip angles of up to 20 degrees until the speed decayed below 75 knots (stall).
Incident Facts
Date of incident
Jul 13, 2011
Classification
Crash
Aircraft Registration
PR-NOB
Aircraft Type
Let L-410 Turbolet
ICAO Type Designator
L410
This article is published under license from Avherald.com. © of text by Avherald.com.
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