Collision with the Terminal: The crash of RwandAir flight 205
On the 12th of November 2009, a bizarre incident unfolded in Kigali, Rwanda. Shortly after departure, the crew of a CRJ-100 regional jet realized that their left engine was jammed at high power and wouldn’t slow down. The pilots successfully returned to the airport for an emergency landing, and despite being unable to reduce thrust on the left engine, they managed to taxi off the runway and into the parking area. But before the passengers could disembark, the aircraft — powered by the still-running engine — lurched forward, swerved wildly across the parking apron, and plowed into the side of a building, pushing the plane through the wall of the VIP lounge. The unexpected accident killed one passenger and seriously injured several others, including both pilots, who had to be extracted from the wreckage using specialized equipment. The head-scratching incident was almost unique in the history of commercial aviation. So how did it happen? Investigators would reveal a chain of both mechanical and human failures that led the jet to collide with a building after everyone on board thought the flight was over.
Nearly 27 years after it ended, most people still associate Rwanda with the bloody genocide that rocked the country in 1994. But since the end of the war Rwanda has quietly undergone a steady rise in prosperity that is making it into one of the better places in Africa to live. Its state-owned flag carrier, RwandAir, reflects that transformation: it operates a relatively modern fleet at a standard of safety high enough to allow it to conduct flights to Europe, a privilege which relatively few African airlines are afforded.
In 2009, RwandAir did not own enough airplanes to carry out all its scheduled services, so it often acquired planes from other airlines through wet leases. In a wet lease, the lessor provided an aircraft and flight crew to RwandAir while RwandAir provided the flight attendants and paid for fees, fuel, and marketing. Among the aircraft under wet lease to RwandAir at the time was a Bombardier CRJ100 regional jet belonging to Kenyan carrier Jetlink Express. The CRJ100, the oldest iteration of the series of small twin-engine jets by Bombardier, was by that time falling out of use in the West but had found a second life in Africa, where many still fly to this day.
The leased CRJ100 also came with a crew of two pilots, both of whom were from Kenya. Jetlink also provided a maintenance engineer who flew around on the plane to troubleshoot mechanical problems and perform on-the-spot maintenance. At 37, the captain had already accumulated a very respectable 11,500 flying hours (perhaps in no small part due to his brutal work schedule, which often saw both him and his first officer exceeding Rwanda’s 12-hour duty day limit). The 27-year-old first officer had finished training in Australia in 2005, and she had since accumulated about 1,500 hours. By November 2009, these same two pilots and the engineer had been flying together for an entire year with no changes to the roster.
On the 12th of November that year, this crew met again to conduct RwandAir flight 205, a short hop from Rwanda’s main airport in Kigali, the capital, to Entebbe International Airport, the largest airport in neighboring Uganda. Although the plane could hold 50 passengers, only ten boarded flight 205. After adding the two pilots, two flight attendants, and the engineer, there were only 15 people on board, leaving the plane almost totally empty. This was not unusual at RwandAir: the airline was operated as a public service and a national brand, and it has never turned a profit since its founding in 2002.
At 12:54 p.m. local time, RwandAir flight 205 lined up with the runway at Kigali International Airport and began its takeoff roll. The crew accelerated both engines to takeoff thrust, and the CRJ100 rolled off down the runway. However, it was not long before they noticed a problem: upon setting the left engine to high power, its associated thrust lever had jammed and could not be moved. Perhaps believing that they could unjam it with some vigorous wiggling, they elected to continue the takeoff.
After climbing at high power to a height of about 4,000 feet above ground level, the first officer attempted to reduce thrust for the next phase of the climb, but was still unable to move the left thrust lever. The left engine was stuck at 94% power, while the right engine successfully reduced to 69%. The captain couldn’t move the lever either. To get more advice on possible solutions, the pilots called the on-board engineer up to the cockpit, and he arrived about 30 seconds later. It didn’t take long for him to confirm what they already knew: the thrust lever had jammed and there was no way to move it. The captain decided to return to the airport for an emergency landing, informing air traffic control and the passengers that they were turning back.
Although nobody on board knew it, the cause of the jammed thrust lever was shockingly simple. It all began when mechanics at Jetlink in Kenya worked on the left engine during a biannual maintenance session on November 10th. In order to access the core of the engine, they used a maintenance door in the core cowling, which had to be propped open with a folding metal strut, much like the rod you can shift into place to prop up the hood of your car. After use, the strut had to be stowed by clicking it into a spring clip and then inserting a locking pin through the strut and the clip. But when the cowl door was closed for the last time, the mechanic made a crucial error: they didn’t insert the locking pin. Exactly how this happened could not be determined with any certainty, but the consequences are well-established: when not locked in place, the strut will work its way out of the spring clip due to engine vibrations after just a few hours or days. The strut will then quite often fall down between the throttle gearbox and the fuel control unit, where it blocks the movement of the fuel control actuating arm, thus jamming the entire throttle control system. When this occurred on flight 205, it became geometrically impossible for the fuel control actuating arm to move into any position commanding a fuel flow rate resulting in less than 93% power, because the support strut was in the way.
A jammed thrust lever is not a major flight safety hazard: in fact, it’s not even considered an emergency. The procedure for dealing with a thrust lever jam, as laid out in the pilots’ quick reference handbook (QRH) and in the flight manual, was simply to press the engine fire push button, which cuts fuel flow to the engine and forces it to shut down. In most previous cases of jammed thrust levers on the CRJ, this is exactly what the pilots did. But on flight 205, at no point did either pilot mention or attempt to follow the official procedures. Instead, they kept the left engine running at high power and turned around for an emergency landing.
While the captain flew a circle to lose altitude, the first officer and the engineer continued trying to move the thrust lever, without success. Nevertheless, the captain was able to bring the plane down despite the high power setting on the left engine, and flight 205 touched down on the runway at 1:06 p.m., after 11 minutes in the air. He had to use considerably more braking power than usual to slow the plane, and both tires on the left main landing gear burst, but the rollout was otherwise uneventful. Following the landing, procedures called for them to evacuate on the runway due to their overheated brakes. But the pilots didn’t seem to feel any great sense of urgency, and the captain instead taxied the aircraft off the runway and into parking bay #4, whereupon he brought the plane to a stop and engaged the parking brake.
Now the pilots needed to figure out what to do about the still-running left engine.
“How will we stop the engine then?” the first officer asked.
“We’ll just think it over, it’s a problem,” the captain replied.
At that moment a warning informed the crew that their brakes were overheating. Indeed, the landing had required so much braking power that parts of the left side main landing gear were melting. “Brake overheat,” the first officer called out.
In an attempt to reduce stress on the brakes, the crew shut off the right engine, but they still couldn’t get the left engine to spool down. The engine fire button, which would have solved all their problems, remained unpressed.
In fact, shutting off the right engine made the problem considerably worse. The CRJ100’s wheel brakes are powered by the #2 and #3 hydraulic systems, which in turn receive electrical power from two different sources. The #2 hydraulic system, which provides pressure to the brakes on the outboard wheel on each set of landing gear, draws power from the electrical generator in the #2 (right) engine. If necessary, the crew can switch the #2 AC Motor Pump switch to “on,” in which case a backup pump will come online to keep pressure in the system. Otherwise, residual pressure will allow the parking brake to remain engaged for a long period of time, but only under normal circumstances, which these were not. Normally a parked airplane requires relatively little braking power to prevent it from moving, and the residual hydraulic pressure is easily enough to accomplish this. But when actively trying to slow the airplane, the residual pressure is only good enough for about six brake applications. On flight 205, continuous high pressure to the parking brake was needed in order to overcome the high thrust from the left engine, so when the crew shut off the right engine, this constant demand quickly drew down the remaining hydraulic pressure to the brakes on the outboard wheels. Now only the brakes on the two inboard wheels were holding the aircraft in place.
Simultaneously, the deflation of the tires on the left main landing gear led to a loss of brake effectiveness in both wheels on that side. When an aircraft tire deflates, the mode of least resistance becomes sliding rather than rolling, in which case the brakes — designed to prevent a wheel from turning — are rendered completely irrelevant. Nobody on board was aware of it, but within a minute, flight 205 would be left with active braking pressure on only one of its four main landing gear wheels.
For the crew, their primary concern was getting the engine shut down. With the left engine still running at full blast, it was unsafe for ground personnel to approach the airplane, so no one had put in the chocks. Unsure how to resolve this condition, the pilots decided that the passengers should be evacuated immediately, before things got any worse. The captain called the lead flight attendant up to the cockpit and told him that because the left engine could not be shut down, they would evacuate all the passengers through the right side of the airplane as soon as he gave the order. The flight attendant then announced that the passengers should unfasten their seat belts and prepare to evacuate. The ten passengers, scattered throughout the airplane, began to stand up and gather their bags.
Suddenly, the falling hydraulic pressure in the #2 system along with the deflated left main landing gear tires caused the total braking force to decrease below the amount needed to prevent the plane from moving. Powered by the left engine, and with only the right inboard wheel experiencing significant braking, the plane lurched forward and began a wide, accelerating turn to the right. The captain yelled out the window for the ground crew to get the chocks in place, but it was already too late; the plane was out of control, and everyone on board was along for the ride. The CRJ100 accelerated to 42 kilometers per hour as it tore across the ramp, sending ground personnel fleeing for their lives. Jet blasts swept the apron, throwing a ramp worker to the ground. As the passengers held on for dear life, the plane plowed through a row of heavy jet blast barriers before slamming headlong into the cinderblock wall of the control tower building, where it erupted into the first floor VIP lounge.
Inside the airplane, the impact severely damaged everything from the nose backward to the main entry doors. In the cockpit, the instrument panel collapsed forward, trapping and seriously injuring the pilots. The engineer and the lead flight attendant took cover at the moment of impact and also escaped with their lives, albeit not without injury. Farther back, the galley structure collapsed backwards onto the first row of seats, crushing a passenger who had been standing in the wrong place at the wrong time. Several other passengers also received varying degrees of injury during the crash, particularly those who had responded to the flight attendant’s announcement by undoing their seat belts and standing up.
As soon as the plane came to rest, fire trucks rushed to the scene and began spraying down the wings, which were leaking fuel, while another truck tried unsuccessfully to drown the left engine with water. Eventually an airport worker managed to pry his way into the cockpit, where he found that the captain had freed himself, but the first officer was still trapped. He attempted to find the engine fire handles, but gave up and tried the throttle lever instead. Most likely the impact had dislodged the troublesome strut, because when he did so the engine spooled down normally.
In total, seven passengers were injured in the crash, as well as both pilots and the engineer. Rescuers only discovered the tenth passenger under the collapsed galley after a head count revealed she was missing; she was pulled from the wreckage with a severe head wound and a weak pulse but died within the hour. The first officer’s legs were so badly trapped by the instrument panel that it took three hours for rescuers to extract her using specialized equipment, making her the last to leave the airplane. The tragedy, however, wasn’t limited to the crash site: in a freak twist of fate just minutes after the rescue, the ambulance carrying the captain, the engineer, and two passengers struck and killed a pedestrian while on the way to the hospital.
The investigation into the accident was led by the Rwanda Civil Aviation Authority, with help from Kenya and the United States. Two main areas of inquiry emerged: the initial engine failure and the crew’s handling of it, and the failure of the plane to remain parked after it came to a stop.
Regarding the engine failure, it was obvious what had happened as soon as investigators opened up the left engine cowl door: the door support strut wasn’t in its clip and had slipped down between the throttle gearbox and the fuel control unit, blocking the actuating arm from adjusting the fuel flow. This was not by any means the first time this had happened. In fact, the manufacturer provided documentation of eight other incidents between 2000 and 2009 in which this exact same sequence of events had occurred. In each case the pilots shut off the affected engine using the fire push button either in the air or after landing, and no one was hurt. Nevertheless, the manufacturer had issued a series of eight service bulletins to CRJ100 operators recommending various changes to the mechanism to make it less likely for the strut to come loose. Jetlink had complied with all of these except for the latest one, which regarded the possibility of vibration-related wear on the spring clip leading it its failure. But in this case the spring clip was not abnormally worn, so the relevance of this service bulletin was doubtful. Rather, it appeared that whoever last stowed the door had simply forgotten to insert the locking pin to keep the strut in place.
Examination of the Jetlink maintenance facility in Kenya revealed that the workshop had not made a habit of complying promptly with manufacturer service bulletins, as neither company procedures nor Kenyan law required them to do so. This lax policy had led to an unacceptably large number of mechanical problems across the Jetlink fleet, but it didn’t explain the accident. The uncompleted service bulletin wouldn’t have prevented the crash, and interviews with all the technicians who worked on the engine revealed that they knew how to stow the strut correctly. And yet, evidently they had forgotten a basic step. Rwandan investigators went home knowing that someone had stowed the strut improperly, but could not say with any certainty who did so, or why.
In any case, it was the crew’s reaction that turned this malfunction into a fatal accident. The official procedures, available right there in the cockpit, would have told them to shut down the engine by pressing the engine fire button. This would have prevented everything that followed. But at no point did either pilot consult any abnormal procedure. A look at Jetlink’s training program revealed a likely reason why. In contravention of basic good sense, Jetlink had a policy of releasing its pilots for line duty before they had finished training: after joining Jetlink, pilots would receive training on abnormal (non-emergency) procedures in small installments spread over two years following their date of hire. It turned out that both pilots of flight 205 were yet to conduct the training module on jammed thrust levers. Investigators felt that this policy was extremely irresponsible: sending pilots out to fly passengers without having trained for any of the abnormal procedures was just asking for them to make an error that would turn a routine mechanical problem into an emergency situation.
Even without this training, however, it wouldn’t have taken an expert to understand that the left engine could be shut off using the engine fire button (which cuts off fuel flow and shuts down the associated generator). Nor should a lack of training be used to explain away the fact that the pilots’ first instinct was somehow not to look for a procedure in the QRH. The Rwandan investigation did not look deeply into these factors, even though they were suggestive of a highly informal cockpit culture at Jetlink, where pilots worked based on intuition and first-hand knowledge rather than prescribed procedures. It is also possible to speculate that inadequate systems knowledge played a role. The engine fire push button simply cuts off fuel flow to the engine, but the pilots might have believed that it was only appropriate to use it if the engine was actually on fire. This is merely speculation, however, as it does not appear that Rwandan investigators ever asked the pilots why they didn’t push the button.
After successfully landing the airplane, this same lack of systems knowledge led to the sudden acceleration and collision with the terminal. The pilots did not understand that shutting off the right engine while the parking brake was actively working against the left engine would lead to a rapid loss of residual pressure in the #2 hydraulic system. They could have prevented this by leaving the right engine running, or by turning the AC Motor Pump switch to “on.” However, despite a brake overheat warning, the pilots seemed to be concerned mainly with their continued efforts to shut off the left engine, blissfully unaware of the fact that their brakes had become a ticking time bomb. In light of this fact their decision to begin evacuation proceedings was reasonable; they simply didn’t have the knowledge to predict what was about to happen. That so many passengers were standing up at the time of the crash undoubtedly worsened their injuries and perhaps led to the fatality as well, but it is difficult to blame this on the pilots, who could not have understood what was going on beneath their feet. That responsibility had to lie with the company, which had not furnished them with sufficient systems understanding to ensure the safety of their airplane at all times.
Following the accident, RwandAir terminated its lease agreements with Jetlink due to their subpar safety standards, and the airline went out of business a little over two years later. The crash of flight 205 is still the only fatal accident in RwandAir’s history, and hopefully will remain so for many years to come. Rwandan investigators also recommended that Kenya ban airlines from upgrading pilots to captain before they have finished training on abnormal procedures, and that Jetlink start paying attention to manufacturer service bulletins (although by then the airline was on its last legs anyway). In addition to these, Transport Canada, which is responsible for the CRJ100’s type certificate, issued an airworthiness directive in 2011 mandating that all operators install a new bracket which is designed to prevent the door strut from interfering with the engine controls even if it is stowed improperly.
The bizarre crash of RwandAir flight 205 belongs to a very rare category of accidents which occurred after the airplane had already parked. Just before the crash, the passengers, and indeed the pilots, clearly believed that the worst was over. So is it worth it to stay vigilant all the way until you step off the jet bridge? Perhaps, if you’re a nervous flyer. But at the end of the day you’re probably more likely to be murdered in the terminal than to find yourself in an emergency on board an airplane that is parked at the gate.
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