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.

5Y-JLD, the CRJ100 involved in the accident. (Bureau of Aircraft Accidents Archives)
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.

Planned route of RwandAir flight 205. (Google + Own work)
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.

A view over Kigali International Airport as it appears today. (Volcanoes National Park Rwanda)
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.

A General Electric CF34 engine similar to the one on the accident airplane. The door support strut is highlighted. (Gleb Osokin)
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.

The location of the unsecured support strut, and a diagram of its stowage mechanism, as seen on the accident airplane. (RCAA)
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.

Visualization of the CRJ’s main landing gear wheels and brakes. Note that the airplane in the image is a CRJ200. (Eric Salard)
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.

The path taken by the airplane, with ground markings, reconstructed by the RCAA. (RCAA)
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.

The aircraft, in the side of a building. (Bureau of Aircraft Accidents Archives)
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 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, particula