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image:reverse.thrust.klm.fokker70.arp.jpg
Fokker 70 with reverse thrust applied. The two surfaces behind the engine can be seen in the deployed position, diverting the engine exhaust gases forward
Boeing 777 with thrust reversers deployed
Thrust reversal, also called
reverse thrust, is the temporary diversion of an aircraft engine's output so that the thrust produced is directed forward, rather than aft. This acts against the forward travel of the aircraft, providing deceleration. Thrust reversers are used by many
jet aircraft to help slow down just after touch-down, reducing wear on the brakes and enabling shorter landing distances. It is also available on many
Propeller through reversing the
controllable pitch propellers to a negative angle.
Operation
Reverse thrust is typically applied immediately after touchdown, often along with Spoiler (aeronautics)s, to improve deceleration early in the landing roll when residual aerodynamic lift and high speed limit the effectiveness of the friction
brakes located on the landing gear. Reverse thrust is always selected manually, either using levers attached to the thrust levers, or by moving the thrust levers into a reverse thrust 'gate'. When thrust is reversed, passengers will hear a sudden increase in engine noise, particularly those seated just forward of the engines.
The early deceleration reverse thrust provides can reduce landing roll by a third or more. Regulations dictate, however, that a plane must be able to land on a runway without the use of thrust reversers in order to be certified to land there as part of airline service.
Once the aircraft's speed has slowed, thrust reverse is deselected to prevent the reversed airflow from raising debris in front of the engine intakes where it can be ingested, causing
foreign object damage. Thrust reverse is effective at any speed, and, in unusual circumstances, can be used all the way to a stop, or even to provide thrust to push the aircraft backward, though Pushbacks or
towbars are more commonly used for that purpose.
If the full power of reverse thrust is not desirable, thrust reverse can be operated with the throttles set at less than full power, even down to idle power, which reduces stress and wear on engine components. Reverse thrust is sometimes selected on idling engines to eliminate residual thrust, particularly in icy or slippery conditions, or where the engines' blast could do damage.
In-flight operation
Some aircraft are able to safely use reverse thrust in flight, though the majority of these are propeller-driven. In-flight use of reverse thrust has several advantages: It allows for rapid deceleration, enabling quick changes of speed; It also prevents the speed buildup normally associated with steep dives, allowing for rapid loss of altitude, which can be especially useful in hostile environments such as combat zones, and when making steep approaches to land.
For example, the ATR 72 turboprop can reverse thrust in flight, should the appropriate control lock be withdrawn. The
Hawker Siddeley Trident, a 120-180 seat airliner, was capable of descending at up to 10,000 ft/min (3,048 m/min) by use of the thrust reversers, though this capability was rarely used. The
US Air Force C-17 Globemaster III is one of the only modern aircraft that uses reverse thrust in flight. The Boeing-manufactured aircraft is capable of in-flight deployment of reverse thrust on all four engines to facilitate steep tactical descents up to 15,000 ft/min (4,600 m/min) into combat environments. The Saab 37 Viggen (retired in November 2005) also had the ability to use reverse thrust before landing, enabling the use of many roads constructed in Sweden to double as wartime runways.
The
Shuttle Training Aircraft, a highly modified
Grumman Gulfstream II, uses reverse thrust in flight to help simulate the
Space Shuttle aerodynamics so astronauts can practice landings.
Turbojet aircraft
On aircraft using
turbojet engines, thrust reversal is accomplished by causing the jet blast to flow forward rather than aft. As the engine is not configured to run (and rotate) in reverse, the thrust reversers block the exhaust flow and redirect it forward. Two methods are commonly used: In the target type of thrust reverser, the reverser blades angle outward, giving the general appearance of flower petals. In the clamshell type (top right), two reverser buckets are hinged so that when they deploy, they intrude into the exhaust of the engine, capturing and reorienting the jet blast. This type of reverser is usually clearly visible at the rear of the engine during use.In addition to the two already mentioned, a third type of thrust reverser is found on some high-bypass turbofan engines. Doors in the bypass duct are used to redirect the air that has been accelerated by the engine's fan section but has not passed through the combustion chamber (called bypass air) so that it provides reverse thrust.The Boeing C-17 has a rare form of the above type in which even the exhaust from the core is redirected along with the main fan's air. This gives the C-17 unrivaled stopping ability among large jet powered aircraft.
Propeller aircraft
Propeller aircraft generate reverse thrust by changing the angle of their controllable pitch propellers so that the propellers direct their thrust forward, instead of aft as normal. Reverse thrust has been available on propeller aircraft dating back to the 1930s. Reverse thrust became available due to the development of controllable-pitch propellers, which change the angle of the propeller blades to make efficient use of engine power over a wide range of conditions.
Small aircraft typically do not feature reverse thrust, except in specialized applications. Similarly, large aircraft (weighing more than 12,500 lb) almost always have the ability to reverse thrust. Both
reciprocating engine and turboprop aircraft can have reverse thrust, and almost all propeller aircraft with reverse thrust have the ability to set the propeller angle to flat pitch (called Beta range) which generates no forward or reverse thrust, but provides large amounts of drag. This is especially useful in aircraft with complex reciprocating or turbine engines, as it enables engine speed to be kept high as the aircraft descends, avoiding doing damage to the engines by shock cooling them.
Multiengine
Early multiengine aircraft such as the Boeing 247 and
Douglas DC-2 were among the first to feature reverse thrust. As piston aircraft became heavier and more complex, reverse thrust became more important to allow them to operate from airports originally configured to handle the smaller planes of previous years. Additionally, the higher performance and greater altitude attainable by post World War II piston aircraft like the Lockheed Constellation made the ability to use flat pitch, or, in extreme cases, reverse thrust, in order to descend and slow for landing without overcooling the engines or approaching the runway with excessive speed. Finally, the advent of turboprops like the Vickers Viscount and Lockheed Electra brought even higher speeds and cruising altitudes to the fleet, as well as increased power that could be used both for improved performance and to provide reverse thrust.
One special application of reverse thrust comes in its use on seaplanes and
flying boats. These aircraft, when landing on water, have no conventional braking method and must rely on slaloming and reverse thrust to slow or stop. Additionally, reverse thrust is necessary for maneuvering on the water, where it is used to make tight turns or even back the aircraft, such as when leaving a dock or beach.
Single-engine
Single-engine aircraft tend to be of such limited size that the weight and complexity of reverse thrust is unwarranted. However, large single-engine aircraft like the
Cessna Caravan do have reverse thrust available, and single-engine seaplanes and flying boats tend to have reverse thrust as well. In other respects, reverse thrust on single-engine aircraft works much like that on other propeller aircraft.
Thrust-reverse related crashes
On most modern jet aircraft, thrust reversers are not intended for deployment in-flight. However, in-flight deployment has directly contributed to the crashes of several transport-type aircraft:
- On 9 February, 1982, Japan Airlines Flight 350 crashed short of the runway at Tokyo International Airport following the intentional deployment of reverse thrust on two of the DC-8's four engines in an apparent suicide attempt, resulting in 24 passenger deaths.
- On August 29, 1990, a Lockheed C-5A crashed shortly after take-off from Ramstein Air Base in Germany. As the aircraft started to climb off the runway, one of the thrust reversers suddenly deployed. This resulted in loss of control of the aircraft and the subsequent crash. Of the 17 people on board, only 4 survived the crash.
- On 26 May, 1991, Lauda Air Flight 004. The Boeing 767 aircraft suffered an uncommanded deployment of the No. 1 thrust reverser, which caused the airliner to stall and crash. {{cite web
| title = 26 May 1991 - Lauda 004
| publisher = Tailstrike.com: [Cockpit Voice Recorder Database
| url = http://www.tailstrike.com/260591.htm
| date = 2004-09-23
| accessdate = 2006-12-14-->
- On October 31, 1996, TAM Linhas Aéreas Flight 402. The Fokker 100 crashed shortly after take-off from Congonhas-São Paulo International Airport, São Paulo, Brazil, striking an apartment building and several houses. All 90 passengers and 6 crew members on board died. Three people were killed on the ground. The crash was attributed to the uncommanded deployment of a faulty thrust-reverser in the right engine shortly after take-off.
Delayed deployment of the thrust reversers may have also contributed to crashes while landing:
- On August 2, 2005, Air France Flight 358 overran the runway at Toronto Pearson International Airport. Although the plane burst into flames and was completely destroyed, there were no fatalities. It was not confirmed nor denied in the official crash report if thrust reverser deployment was delayed or if this played a role.
- On 8 December, 2005, Southwest Airlines Flight 1248 overran the runway at Chicago Midway Airport, killing a 6-year old boy in a car. It was confirmed in the official crash report that delayed thrust reversers played a role.
- On July 17, 2007, TAM Linhas Aéreas Flight 3054 overran the runway at Congonhas Airport. Reasons are yet to be confirmed, but early speculation is that a combination of deactivated thrust-reversers and a resurfaced but ungrooved runway in wet conditions may have played a role. Approximately 205 people were killed.
References
External links
- Reducing Landing Distance
image:reverse.thrust.klm.fokker70.arp.jpg Fokker 70 with reverse thrust applied. The two surfaces behind the engine can be seen in the deployed position, diverting the engine exhaust gases forward
Boeing 777 with thrust reversers deployed
Thrust reversal, also called
reverse thrust, is the temporary diversion of an
aircraft engine's output so that the thrust produced is directed forward, rather than aft. This acts against the forward travel of the aircraft, providing deceleration. Thrust reversers are used by many jet aircraft to help slow down just after touch-down, reducing wear on the brakes and enabling shorter landing distances. It is also available on many
Propeller through reversing the
controllable pitch propellers to a negative angle.
Operation
Reverse thrust is typically applied immediately after touchdown, often along with Spoiler (aeronautics)s, to improve deceleration early in the landing roll when residual
aerodynamic lift and high speed limit the effectiveness of the friction brakes located on the landing gear. Reverse thrust is always selected manually, either using levers attached to the thrust levers, or by moving the thrust levers into a reverse thrust 'gate'. When thrust is reversed, passengers will hear a sudden increase in engine noise, particularly those seated just forward of the engines.
The early deceleration reverse thrust provides can reduce landing roll by a third or more. Regulations dictate, however, that a plane must be able to land on a runway without the use of thrust reversers in order to be certified to land there as part of
airline service.
Once the aircraft's speed has slowed, thrust reverse is deselected to prevent the reversed airflow from raising debris in front of the engine intakes where it can be ingested, causing foreign object damage. Thrust reverse is effective at any speed, and, in unusual circumstances, can be used all the way to a stop, or even to provide thrust to push the aircraft backward, though
Pushbacks or towbars are more commonly used for that purpose.
If the full power of reverse thrust is not desirable, thrust reverse can be operated with the throttles set at less than full power, even down to idle power, which reduces stress and wear on engine components. Reverse thrust is sometimes selected on idling engines to eliminate residual thrust, particularly in icy or slippery conditions, or where the engines' blast could do damage.
In-flight operation
Some aircraft are able to safely use reverse thrust in flight, though the majority of these are propeller-driven. In-flight use of reverse thrust has several advantages: It allows for rapid deceleration, enabling quick changes of speed; It also prevents the speed buildup normally associated with steep dives, allowing for rapid loss of altitude, which can be especially useful in hostile environments such as combat zones, and when making steep approaches to land.
For example, the ATR 72 turboprop can reverse thrust in flight, should the appropriate control lock be withdrawn. The
Hawker Siddeley Trident, a 120-180 seat airliner, was capable of descending at up to 10,000 ft/min (3,048 m/min) by use of the thrust reversers, though this capability was rarely used. The US Air Force C-17 Globemaster III is one of the only modern aircraft that uses reverse thrust in flight. The
Boeing-manufactured aircraft is capable of in-flight deployment of reverse thrust on all four engines to facilitate steep tactical descents up to 15,000 ft/min (4,600 m/min) into combat environments. The Saab 37 Viggen (retired in November 2005) also had the ability to use reverse thrust before landing, enabling the use of many roads constructed in Sweden to double as wartime runways.
The
Shuttle Training Aircraft, a highly modified
Grumman Gulfstream II, uses reverse thrust in flight to help simulate the
Space Shuttle aerodynamics so astronauts can practice landings.
Turbojet aircraft
On aircraft using turbojet engines, thrust reversal is accomplished by causing the
jet blast to flow forward rather than aft. As the engine is not configured to run (and rotate) in reverse, the thrust reversers block the exhaust flow and redirect it forward. Two methods are commonly used: In the target type of thrust reverser, the reverser blades angle outward, giving the general appearance of flower petals. In the clamshell type (top right), two reverser buckets are hinged so that when they deploy, they intrude into the exhaust of the engine, capturing and reorienting the jet blast. This type of reverser is usually clearly visible at the rear of the engine during use.In addition to the two already mentioned, a third type of thrust reverser is found on some high-bypass turbofan engines. Doors in the
bypass duct are used to redirect the air that has been accelerated by the engine's fan section but has not passed through the combustion chamber (called bypass air) so that it provides reverse thrust.The
Boeing C-17 has a rare form of the above type in which even the exhaust from the core is redirected along with the main fan's air. This gives the C-17 unrivaled stopping ability among large jet powered aircraft.
Propeller aircraft
Propeller aircraft generate reverse thrust by changing the angle of their
controllable pitch propellers so that the propellers direct their thrust forward, instead of aft as normal. Reverse thrust has been available on propeller aircraft dating back to the 1930s. Reverse thrust became available due to the development of controllable-pitch propellers, which change the angle of the propeller blades to make efficient use of engine power over a wide range of conditions.
Small aircraft typically do not feature reverse thrust, except in specialized applications. Similarly, large aircraft (weighing more than 12,500 lb) almost always have the ability to reverse thrust. Both reciprocating engine and turboprop aircraft can have reverse thrust, and almost all propeller aircraft with reverse thrust have the ability to set the propeller angle to flat pitch (called Beta range) which generates no forward or reverse thrust, but provides large amounts of drag. This is especially useful in aircraft with complex reciprocating or turbine engines, as it enables engine speed to be kept high as the aircraft descends, avoiding doing damage to the engines by shock cooling them.
Multiengine
Early multiengine aircraft such as the Boeing 247 and
Douglas DC-2 were among the first to feature reverse thrust. As piston aircraft became heavier and more complex, reverse thrust became more important to allow them to operate from airports originally configured to handle the smaller planes of previous years. Additionally, the higher performance and greater altitude attainable by post
World War II piston aircraft like the Lockheed Constellation made the ability to use flat pitch, or, in extreme cases, reverse thrust, in order to descend and slow for landing without overcooling the engines or approaching the runway with excessive speed. Finally, the advent of turboprops like the
Vickers Viscount and Lockheed Electra brought even higher speeds and cruising altitudes to the fleet, as well as increased power that could be used both for improved performance and to provide reverse thrust.
One special application of reverse thrust comes in its use on seaplanes and flying boats. These aircraft, when landing on water, have no conventional braking method and must rely on
slaloming and reverse thrust to slow or stop. Additionally, reverse thrust is necessary for maneuvering on the water, where it is used to make tight turns or even back the aircraft, such as when leaving a dock or beach.
Single-engine
Single-engine aircraft tend to be of such limited size that the weight and complexity of reverse thrust is unwarranted. However, large single-engine aircraft like the Cessna Caravan do have reverse thrust available, and single-engine seaplanes and flying boats tend to have reverse thrust as well. In other respects, reverse thrust on single-engine aircraft works much like that on other propeller aircraft.
Thrust-reverse related crashes
On most modern jet aircraft, thrust reversers are not intended for deployment in-flight. However, in-flight deployment has directly contributed to the crashes of several transport-type aircraft:
- On 9 February, 1982, Japan Airlines Flight 350 crashed short of the runway at Tokyo International Airport following the intentional deployment of reverse thrust on two of the DC-8's four engines in an apparent suicide attempt, resulting in 24 passenger deaths.
- On August 29, 1990, a Lockheed C-5A crashed shortly after take-off from Ramstein Air Base in Germany. As the aircraft started to climb off the runway, one of the thrust reversers suddenly deployed. This resulted in loss of control of the aircraft and the subsequent crash. Of the 17 people on board, only 4 survived the crash.
- On 26 May, 1991, Lauda Air Flight 004. The Boeing 767 aircraft suffered an uncommanded deployment of the No. 1 thrust reverser, which caused the airliner to stall and crash. {{cite web
| title = 26 May 1991 - Lauda 004
| publisher = Tailstrike.com: [Cockpit Voice Recorder Database
| url = http://www.tailstrike.com/260591.htm
| date = 2004-09-23
| accessdate = 2006-12-14-->
- On October 31, 1996, TAM Linhas Aéreas Flight 402. The Fokker 100 crashed shortly after take-off from Congonhas-São Paulo International Airport, São Paulo, Brazil, striking an apartment building and several houses. All 90 passengers and 6 crew members on board died. Three people were killed on the ground. The crash was attributed to the uncommanded deployment of a faulty thrust-reverser in the right engine shortly after take-off.
Delayed deployment of the thrust reversers may have also contributed to crashes while landing:
- On August 2, 2005, Air France Flight 358 overran the runway at Toronto Pearson International Airport. Although the plane burst into flames and was completely destroyed, there were no fatalities. It was not confirmed nor denied in the official crash report if thrust reverser deployment was delayed or if this played a role.
- On 8 December, 2005, Southwest Airlines Flight 1248 overran the runway at Chicago Midway Airport, killing a 6-year old boy in a car. It was confirmed in the official crash report that delayed thrust reversers played a role.
- On July 17, 2007, TAM Linhas Aéreas Flight 3054 overran the runway at Congonhas Airport. Reasons are yet to be confirmed, but early speculation is that a combination of deactivated thrust-reversers and a resurfaced but ungrooved runway in wet conditions may have played a role. Approximately 205 people were killed.
References
External links
- Reducing Landing Distance
Thrust reversal - Wikipedia, the free encyclopedia
Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine 's exhaust or changing of propeller pitch so that the thrust produced is directed ...
BBC NEWS | Americas | Brazil jet thrust reverser 'off'
A jet which crashed killing some 200 people had only one thrust reverser working, Brazilian officials say.
Thrust Reverser falls off 747 in Frankfurt - PPRuNe Forums
Frankfurt - A thrust reverser broke off a jumbo jet while it was landing Sunday at Frankfurt international airport in Germany, but the plane came to a
Category:Thrust reverser - Wikimedia Commons
Pages in category "Thrust reverser" This category contains only the following page. R. Reverse thrust
BBC NEWS | World | Americas | Brazil jet thrust reverser 'off'
A jet which crashed killing some 200 people had only one thrust reverser working, Brazilian officials say.
Lauda Air Flight 004 - Wikipedia, the free encyclopedia
Lauda Air Flight 004 was an international passenger flight that crashed due to a thrust reverser deployment of the number 1 engine, in flight. On May 26, 1991, about 23:10 local ...
The Handling of Thrust Levers During Landing with a Deactivated Thrust ...
The Handling of Thrust Levers During Landing with a Deactivated Thrust Reverser for Airbus A318/319/320/321 Aeroplanes
Smiths provides Thrust Reverser Actuation System for B747-8
Smiths Group is a world leader in the practical application of advanced technologies. Our products and services make the world safer, healthier and more productive.
Core Thrust Reverser - What does CTR stand for? Acronyms and ...
Acronym Definition; CTR: Center: CTR: Centre: CTR: Contractor: CTR: Click Through Rate: CTR: Cooperative Threat Reduction: CTR: Cooperative Threat Reduction (Counter-Strike gaming ...
Thrust reverser - What does TR stand for? Acronyms and abbreviations ...
Boeing Commercial Aviation Services and Goodrich Aerostructures Service Center Europe reached an agreement to perform thrust reverser component MRO on 737NGs and 777s.
