Jetlink Air CRJ1 at Kigali on Nov 12th 2009, throttle jam, impacted terminal after return

Last Update: April 19, 2017 / 16:34:54 GMT/Zulu time

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Incident Facts

Date of incident
Nov 12, 2009

Classification
Accident

Flight number
WB-205

Destination
Entebbe, Uganda

Aircraft Registration
5Y-JLD

ICAO Type Designator
CRJ1

Airport ICAO Code
HRYR

VIP Terminal (Photo: Steve Rwanda) A Jetlink Air Canadair CRJ-100 on behalf of Rwandair Express, registration 5Y-JLD performing flight WB-205 from Kigali (Rwanda) to Entebbe (Uganda) with 10 passengers and 5 crew (one flight mechanics), turned around shortly after takeoff with the crew reporting a jam of their throttle levers. The airplane landed safely, but subsequently impacted the VIP terminal of Kigali Airport at around 13:00 local (11:00Z). A fire broke out.

Emergency services were able to quickly contain the fire. Several injuries occured, especially with the flight crew, who were trapped in the cockpit and needed to be freed. One flight crew was freed about three hours after the accident. Emergency services at the airport report no fatalities. Injuries also occured to people in the VIP terminal. A total of 10 injured have been taken to local hospitals.

Jetlink reported, that the airplane was taxiing in, when the aircraft impacted the pavillon of the VIP lounge nose-first with engines at high power. All passengers could leave the airplane on their own, the airline however believed that one female passenger passed away in hospital.

Rwandair Express said in a detailed statement of Nov 13th, that the airplane had taken off at 12:40L, two minutes later the captain requested to return due to a technical problem. The airplane landed safely and taxied to the gate. When the ground crew was just about to put wheel chocks on, the airplane suddenly accelerated, turned right and hit the eastern wall of the VIP terminal building about 500 meters away. 8 passengers were brought to the hospital, one female passenger died, one passenger received two broken ribs and a punctured lung, 6 of them were released after evaluation. Both cabin crew were also delivered to hospital and discharged after evaluation. The captain received a broken leg, the first officer a broken ankle, the flight mechanics received bruises and was kept in hospital for observation.

Rwanda's Information minister reported, that one passenger died in hospital, four more passengers and one crew member received injuries.

Passengers reported, that the crew told them about technical problems about 15 minutes into the flight and returned to Kigali. The airplane touched down, but then it appeared the pilots were unable to slow/stop the airplane before it impacted the building.


Rwanda's Air Accident Investigation Department (RAAID) released their final report concluding the probable causes of the accident were:

The flight crew’s failure to identify corrective action and their lack of knowledge of applicable airplane and engine systems in response to a jammed thrust lever, which resulted in the number 1 engine operating at high power and the airplane configured in an unsafe condition that led to the need to apply heavy braking during landing. Also causal was the flightcrew failure to recognize the safety hazard that existed from overheated brakes and the potential consequence on the braking action needed to park the airplane. Contributing factors included the possible failure by maintenance crew to correctly stow the upper core cowl support strut after maintenance, Flightcrew’s failure to follow standard operating procedures, the company’s failure to be availed to manufacturer safety literature on the subject, and the susceptibility of the cowl core support shaft to interfere with the throttle control mechanism when the core strut is not in its stowed position.

The RAAID summarized the captain's (37, ATPL, 11,478 hours total, 1,110 hours on type) testimony: "after getting airborne, I asked my copilot to conduct the climb and after takeoff checks. She had a problem with retarding the left thrust lever. I called the engineer to help the copilot retard the left throttle, but it was not possible. I asked the tower controller for permission to land. I landed with one engine on maximum power and landed normally though heavy braking, the tires deflated and parked the aircraft and shortly the plane started rolling downwards toward the barrier and Air Traffic Control Tower building. I had no control over the plane as I even tried to steer it clear of the building."

The RAAID summarized the first officer's (27, CPL, 1,558 hours total, 533 hours on type) testimony: "after takeoff, I tried to set climb thrust and noticed the left thrust lever could not adjust. I then informed the captain that the throttle was stuck. He tried to adjust it too but it was stuck. We then called for the engineer, we coordinated together and the captain focused on flying the plane safely while I communicated with ATC, did the checklists and we combined efforts with the engineer to try and adjust the left thrust lever. We landed safely and parked but the left trust lever could not be adjusted still. As we were trying to retard it and shut it down while holding on brakes, the plane started rolling again. Efforts to stop it from rolling failed but the captain managed to control it away from the other traffic. We then hit a wall as the plane could not stop and the thrust lever was still stuck forward."

The RAAID reported that the #1 engine was running at 95% according to flight data recorder while the right hand engine varied between 28 and 88%. The aircraft began the descent back to Kigali at about 9200 feet MSL, setup for a circling descent and configured the aircraft for landing while the first officer and an engineer on board of the aircraft, who had come to the cockpit to assist the flight crew, continued to attempt to retard the thrust lever. The RAAID wrote: "The flightcrew made no discussion at any time about referencing the quick reference handbook, flight crew operating manual, or airplane flight manual."

The aircraft landed on runway 28 with engine #1 at 95% N1 and #2 at 27% N1. Heavy braking ensued to stop the aircraft. The aircraft came to a stop at the apron before the VIP building, the #1 engine continued to run at high power while the crew discussed the engine problem and how to shut it down. The crew received a brakes overheat warning and shut the #2 engine down, however, the #1 engine was still running at high speed. About 76 seconds after the aircraft came to a stop at the apron the aircraft began to move again. At this time the captain was briefing the purser that they were unable to shut the left hand engine down and the passengers should disembark through the right hand door and galley. Only then the crew noticed the aircraft was moving again at 23 knots, the crew started screaming for chocks, the screams continued until impact with the terminal building.

A ground witness reported the aircraft had been choked in parking bay #4 however started to move again. The nose of the aircraft went through the terminal and tower building, the engines continued to run.

The RAAID described the damage: "The aircraft was substantially damaged. Wings detached from the front attachment points. The aircraft nose section and the cockpit area were damaged."

The RAAID reported that on Nov 10th 2009 the left hand engine needed maintainance requiring to open the core cowl. The RAAID wrote: "The engineer, who last closed the core cowl before the day of the accident, was familiar with stowing and securing the cowl strut. Investigation did not positively determined if the engineer had correctly stowed the cowl strut soon after maintenance."

The RAAID also mentioned another occurrence where the left hand engine had gone out of control: "On a separate occasion during ground test of the left engine after maintenance work was conducted on the fuel control Unit (FCU), a rod of the FCU came loose and the engine became uncontrollable. The engineer (mentioned above), who had not secured the rod prior to ground tests, managed to shut down the engine using fuel shut off valve."

A post accident investigation revealed that the core cowl support strut was not in its stowed position blocking the fuel control unit actuating arm to retard below 93%.

The RAAID wrote: "Examination of the left engine revealed the throttle mechanism was in the idle position, the upper core cowl support strut not its stowed position and the safety pin hanging from its lanyard as indicated in number 3 photo below. The strut was in a position to prevent movement of the fuel control unit actuating arm less than the 93% N1. The components of the strut stow assembly, consisting of the locking collar, spring clip, and lock pin were inspected and no evidence of mechanical malfunction was revealed. Continuity was established between the left engine thrust lever and fuel control unit."

The RAAID commended the crew for landing the aircraft in the most abnormal conditions, however condemned the crew for lack of discipline working the checklists, consulting with company maintenance, lack of system knowledge and overall poor judgement.

The RAAID analysed:

The TLJ condition was noticed by the flightcrew early in the takeoff phase and the PIC decided to discontinue the flight to the destination, to take steps to resolve the problem and the consequential abnormal flight performance. However, flightcrew ’s lack of discipline to complying with standard procedures under the conditions, lack of understanding of the engine systems, failure to consult with company operational and maintenance personal, and overall poor judgment resulted in their not being able to identify the appropriate action. Consequently, the aircraft performance remained in an undesired state with the number 1 engine at an improper power setting for landing and during ground operations. The inadequate flightcrew actions resulted in an escalation of a single abnormal condition to a cascading of non-normal conditions together with an increase in workload and task saturation.

Despite the flightcrew mishandling of the TLJ, they commendably were able to land the airplane under a most abnormal condition.

The increased power setting on the number 1 engine during the landing required extra braking resulting in hot brakes. The flightcrew was aware of the problem, but did not fully recognize the consequences of the conditions if not remedied. As was the case in the air, the flightcrew deviated from procedures when a non-normal condition was encountered, together with the false sense that the level of threat to safety had been significantly reduced, resulted in the brake operation continuing. The application of brakes during taxi only aggravated the hot brakes of which apparently the flightcrew did not fully realize the degree of safety hazard that existed.

Under normal circumstances, the captain should have reported the situation to ATC and follow airplane flight manual and airport procedures for hot brakes which would have involved firefighting personnel at the time. However, the no 1 engine power setting made avoidance of the use of the brakes impracticable. Therefore Flightcrew’s failure to shut down the number 1 engine and continuing inability to allow a correctable condition to persist were the sources of the succeeding hazards.
Although the PIC succeeded with bringing the airplane to a stop, he understandably became focused on the evacuation of the airplane and shutting down the number 1 engine. Consequently, his lack of understanding of the brake system and the associated non-normal condition resulted in a degradation of the braking capabilities. The captain’s lack of comprehension of the deterioration and his concern about the number 1 engine resulted in communication with the cabin attendant that invariably resulted in instructions to the passengers to unfasten their seatbelt, placing them in a hazardous condition, which in the case was probably not foreseeable. The crew was concerned with the safety of the passengers by their quick exiting of the airplane and the decision to release the seatbelts was not unreasonable.

The loss of capability of the airplane to remain parked can be attributed to either one or a combination of the following events: deflation of the tire due to rupture/ melting of the wheel fuses and the loss of adequate hydraulic pressure to provide sufficient parking braking. The rupture of the tire and the melting of the wheel fuse plug would have been a direct result of the hot brakes as the over-temperatures exceeded the limits to maintain the mechanical integrity of the components causing the loss of sufficient ground traction. The loss of hydraulic pressure as a result of the shutdown of the number 2 engine, which occurred before the airplane was parked, resulted in the loss of brake pressure to the outboard brakes. The airplane swerved to the right during its uncommanded movement before it struck the building. The action is consistent with the loss of ground traction, and the absence of skid marks, from the left inside tire, as evident by the deflated left inside tire, and the application of brakes on the right tire due the availability of only hydraulic system number 1 as exhibited by the associated skid marks.

The passengers were unrestrained when the airplane abruptly traveled across the ramp from the park position. The announcement to the passengers to unfasten the seat belts would have given the passengers that it was safe to become unseated in anticipation of exiting the airplane. Therefore many of the passengers were probably standing at the outset of the sudden movement of the airplane from being parked. The passengers, especially those who were standing would have been displaced by forces associated with the acceleration and deceleration with the respective movement across the ramp and the collision with the barriers and building, and its probable the foregoing sequence attributed directly to the injuries that were sustained by the occupants in the cabin. Consistent with the surgeon’s forensic determination of the fatal injuries to the passenger, rescuers statements, the collapsed structure of which she was subject increased the severity of the incurred injuries.

The RAAID analysed with respect to the engine cowl support strut:

The aircraft had been operated for 4.6 hours, and completed 6 flight segments since it had undergone scheduled maintenance. The number 1 engine core cowl door had not been opened since the maintenance. There were no deficiencies reported involving the operation of the thrust lever for the number 1 engine. It is suspected maintenance crew did not correctly stow the cowl strut after performing maintenance and due to engine vibrations, could have moved and interfered with engine throttle mechanism. Therefore, the cowl strut interference probably occurred during the takeoff phase of the accident flight, most likely shortly before the TLJ was noticed by the flightcrew.

The company operational personnel were not familiar with the service bulletin or history of in-flight incidents involving the cowl core door support shaft mechanism. The maintenance personnel, including those who were last involved with the closing the cowl door, were knowledgeable of the correct latching procedure. There was no indication that the procedure was not followed when the cowl door was last used.

The support shaft stow mechanism had been the subject of several service bulletins requiring its modification. The aircraft manufacture considers the jam of one engine throttle during flight a low risk as the manufacturer has provided a mitigating procedure in both the Aircraft Flight Manual and FCOM. The service bulletins were specified as discretionary for compliance except one recommended service bulletin number 601R-71-026. Although there were indications of compliance to the earlier service bulletins, the one in effect at the time of the accident had not been complied with. Further, several incidents had occurred before this accident were attributed to the core cowl door support strut interfering with left engine throttle mechanism. Given the possible failure by maintenance crew to stow the core cowl support strut correctly and mechanism susceptibility to interfere with throttle mechanism in its unstowed position, it is most probable that the incorrectly stowed core cowl support strut interfered with the throttle mechanism above 93% NI speed during takeoff resulting in the engine number 1 throttle jam.
The company lack of familiarity with the history of the cowl door support shaft stow mechanism was a combination of its maintenance program that did not require mandatory compliance of all service bulletins, not availing itself to safety literature that would have alerted of the problem, and the manufacturer’s classification of the service bulletin as low risk that resulted in undervaluing the level of risk associated with the condition.

Metars:
HRYR 121230Z 00000KT 9999 SCT030 SCT100 26/16 Q1015 NOSIG
HRYR 121200Z VRB03KT 9999 BKN030 26/17 Q1016 NOSIG
HRYR 121130Z VRB03KT 9999 BKN030 26/13 Q1016 NOSIG
HRYR 121100Z VRB03KT 9999 BKN030 26/17 Q1017 NOSIG
HRYR 121030Z VRB03KT 9999 BKN030 24/18 Q1018 NOSIG
HRYR 121000Z 00000KT 9999 SCT030 SCT100 24/17 Q1018 NOSIG
Incident Facts

Date of incident
Nov 12, 2009

Classification
Accident

Flight number
WB-205

Destination
Entebbe, Uganda

Aircraft Registration
5Y-JLD

ICAO Type Designator
CRJ1

Airport ICAO Code
HRYR

This article is published under license from Avherald.com. © of text by Avherald.com.
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