Flameout

In aviation a flameout refers to the run-down of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel starvation, compressor stall, insufficient oxygen (at high altitudes), foreign object damage (such as caused by birds, hail or volcanic ash), severe inclement weather, mechanical failure and very cold ambient temperatures.^[1][2]

Description

A flame-out is most likely to occur when flying through certain weather conditions at a low power setting such as flight idle (e.g. during the descent). These conditions include flight through moderate to heavy turbulence, rain, hail or sleet. The potentially hazardous circumstances are highlighted in the flight manual with a requirement to select continuous ignition. Alternatively, the FADEC engine controller will select ignition automatically if it detects specific changes in engine parameters. It will also perform a relight if necessary. A manual re-light attempt is made by following the procedure in the Flight Operations Manual.^[3]

Early jet engines, such as Junkers Jumo 004 used in early German jets, including the Messerschmitt Me 262, were at relatively high risk of flameout. Fast acceleration or inappropriate throttle settings could impoverish the fuel/air mixture causing a flameout. If this happened at low altitude, it would often lead to the total loss of the aircraft. However, jet engines were developed to be controlled with a governor, a centrifugal feedback valve for controlling the speed of the engine - sometimes referred to as FCU (Fuel Control Unit) or HMU (Hydro-Mechanical Unit) - allowing controlled fuel metering proportional to the engine's rotational speed. Current modern engines are engineered to a higher degree of technical quality controlled by digital electronic systems (FADEC) that constantly fine-tune their performance; thus such flameouts are not as common as they were in the early days of jet-powered aviation.

It is common practice for pilots to be taught, and practice, flame-out landings.^[4]

Windmill restart

In-flight restarts are designated as either windmill or starter-assisted, depending where in the flight envelope the restart is attempted. The re-light envelope occupies the lower part of the flight envelope below about 30,000 ft (28,000 ft in the case of a Boeing 747, which experienced flame-outs at 37,000 ft^[5]). When an appropriate initial altitude and forward speed are available, the mass airflow through the compressor turbine blades can maintain sufficient rotational velocity for enough time to permit re-start. If the aircraft's operating conditions are not sufficient for a windmill start, the engine's starter motor must be operated to increase the turbine velocity to the minimum required speed.^[6]

Notable incidents of flameout

• On 6 August 1945, the top USAAF fighter ace Richard Bong died in a flight accident as his Lockheed P-80 Shooting Star fighter suffered a flameout and dived to the ground.
• On 21 June 1972, Jean Boulet piloted an Aérospatiale Lama helicopter to an absolute altitude record of 12,442 meters (40,814 ft).^[7] At the extreme altitude the engine flamed out. The helicopter landed safely after the longest ever autorotation in history.
• In a severe hailstorm on 4 April 1977, Southern Airways Flight 242, a DC-9-31 owned by Southern Airways, lost both engines due to the hail. The plane landed on a highway and crashed into a gas station, killing 72.
• On 24 June 1982, British Airways Flight 9 suffered flameouts in all four of its engines after flying through a cloud of pyroclastic material thrown up by the eruption of Mount Galunggung. The pilots were eventually able to restart three of the engines and make a safe landing.
• On 19 February 1985, China Airlines Flight 006, a Boeing 747SP, operating from Taipei to Los Angeles lost engine #4 and plunged 9,100m before the crew were able to recover the aircraft. The flight was diverted to San Francisco International Airport without further incident.
• On 15 December 1989, KLM Flight 867, a Boeing 747-400 Combi, operating from Amsterdam to Tokyo lost power to all four engines after flying through an ash plume from Mount Redoubt, a volcano in Alaska. The pilots were eventually able to restart the engines after losing 14,000 feet (4,300 m) of altitude, and to land the plane at Anchorage, Alaska, with no casualties.
• On 16 January 2002, Garuda Indonesia Flight 421 crashed into a river after suffering a flameout while flying though a heavy rain and hail storm.
• On 21 November 2002, during a routine test flight the Eurofighter DA6, a Spanish development prototype, crashed following an irrecoverable ‘double engine flame-out’ in flight; both crew members escaped unharmed.^[8]
• On 14 October 2004, Pinnacle Airlines Flight 3701 suffered flameouts in both of its engines. The aircraft crashed near Jefferson City, Missouri, after being unable to restart the engines. The pilot and co-pilot were both killed.
• In September 2007, while engaged in separation tests of the GBU-39 Small Diameter Bomb, an F-22 Raptor suffered a brief dual-engine flameout while performing a negative-g, 360 degree roll with eight SDBs loaded in the weapons bay. The flameout occurred because the aircraft entered the maneuver with an incorrect trim setting. The engines were restarted almost immediately, allowing the pilot to remain in control of the aircraft and land at Edwards AFB, California, without further incident.^[9]
• In 2010, Qantas Flight 32 experienced problems with an engine after it landed; it could not shut down and hence the emergency services had to conduct a flameout.
• On 29 November 2013, a Police Scotland Eurocopter EC135-T2+ experienced a double engine flame-out and crashed into a Glasgow pub, the Clutha Vaults. Three persons in the aircraft and seven on the ground were killed; an additional 32 were injured. According to a 14 February 2014 Special Bulletin from the Air Accidents Investigation Branch, the reason for the flame-out had not been determined.
• On 4 February 2015, TransAsia Flight 235, operated by an ATR 72-600, crashed soon after takeoff in Taipei, with the pilot reporting an engine flameout approximately one minute before the crash. The incident is currently under investigation.

References