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 flameout is believed to be 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 were prone to flameout due to disturbances of inlet air, casused from gas ingestion. Fast acceleration or inappropriate throttle settings could also impoverish the fuel/air mixture causing a flameout or an excessive JPT (Gage failure). However, if the throttle movements are made smoothly and not to rapidly, there was little or no risk of flame extinction. 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 to practice flameout 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 flameouts at 37,000 ft^[5]). When an appropriate initial altitude and forward speed are available, the mass airflow through the compressor blades can maintain sufficient rotational velocity for enough time to permit restart. 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

Engine flameout due to inclement weather and volcanic activity

• 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 rural highway and crashed into a gas station, killing 72 people.
• On 24 June 1982, British Airways Flight 9 suffered a quadruple engine flameout after flying through a cloud of pyroclastic material thrown up by the eruption of Mount Galunggung. The pilots were eventually able to restart all four engines and execute a safe landing. There were no fatalities.
• On May 24, 1988, TACA Flight 110, a Boeing 737-300, operating from Belize to New Orleans, suffered a dual engine flameout while flying through heavy rain, hail and turbulence. The plane glided and landed on a narrow grass levee at NASA's Michoud Assembly Facility in the Michoud area of eastern New Orleans. All 45 people on board survived.

Engine flameout due to fuel starvation

• On July 23, 1983, Air Canada Flight 143, a Boeing 767, ran out of fuel, causing both of its engines to flameout. The pilot was able to glide the plane to safety, landing it on an auto racing track which was previously the RCAF Station Gimli. Hence the aircraft involved is known as the Gimli Glider.
• On August 24, 2001, Air Transat Flight 236, operated by an Airbus A330, experienced a flameout on both of its engines due to fuel starvation. The plane continued to glide until it landed safely in Azores. All 306 passengers and crew on board the plane were unharmed.
• On 29 November 2013, a Police Scotland Eurocopter EC135-T2+ experienced a double engine flameout 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. Both engines flamed out about 32 seconds apart due to fuel starvation.^[7]

Engine flameout due to mechanical problems

• On 19 February 1985, China Airlines Flight 006, a Boeing 747SP, operating from Taipei to Los Angeles plunged 30,000 ft (9,100m) after the plane's fourth engine flamed out. The pilots managed to recover the plane in the nick of time and the flight was diverted to San Francisco International Airport without further incident. Two passengers were seriously injured as a result of the plunge. The airplane was significantly damaged after the incident, including the loss of parts of its horizontal stabilizers.
• On 4 February 2015, TransAsia Flight 235, operated by an ATR 72-600, crashed soon after takeoff in Taipei. Approximately one minute before the crash the pilot reported an engine flameout which had been caused by an engine failure. Combined with the mistaken shut down of the working engine this caused the aircraft to strike a viaduct and crash into a river, killing 43 out of the 58 people on board.

Other examples

• 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. By that time no less than eight YP-80s and P-80A/(F-80A) had been destroyed in crashes, seven of which of had been severely damaged, and six pilots killed. The day after Richard Bong's fatal crash the USAAF ordered the "Shooting Star" grounded until these problems could be corrected.

• On 6 September 1946, the first prototype of the Avia S-92, reverse engineered from Messerschmitt Me 262A-1a, crash landed on its sixth test flight after suffered a flameout. Pilot Antonin Kraus was uninjured.

• On 22 November 1949, the first prototype Gloster E.1/44, on test flight out of the Royal Aircraft Establishment (RAE), Farnborough, suffers engine flameout and crash landed. The pilot escaped uninjured.

• On 21 June 1972, Jean Boulet piloted an Aérospatiale Lama helicopter to an absolute altitude record of 12,442 meters (40,814 ft).^[8] At the extreme altitude the engine flamed out. The helicopter landed safely after the longest ever autorotation in history.

References

1. "''Turbo Jet Flame Out'' by Ask a Scientist". Newton.dep.anl.gov. Retrieved 2012-03-25.
2. "''Flameout - Why the fire in a perfectly healthy jet engine can die.'' by Peter Garrison, Air & Space Magazine, September 01, 2006". Airspacemag.com. Retrieved 2012-03-25.
3. "''Airplane Turbofan Engine Operation and Malfunctions'', FAA Manual". Webcache.googleusercontent.com. Retrieved 2012-03-25.
5. Flightglobal archive flight International 10 July 1982 p59
6. "Gas Turbine Performance" 2nd edition P.P.Walsh P. Fletcher ISBN 0-632-06434-X p484
7. "AAIB Bulletin 12/2015" (PDF). Air Accidents Investigation Branch, Department for Transport. Retrieved 10/12/2015. Check date values in: |access-date= (help)