Target-type thrust reversal

Last updated
Video of a target-type thrust reverser in operation

Target-type thrust reversal (also called bucket thrust reversal or clamshell thrust reversal [1] ) is a deceleration method when an aircraft lands. Like other types of thrust reversals, it temporarily diverts the engine exhaust (thrust) forward to provide deceleration. This type of thrust-reverser is suitable for engines of 3,000 lbf (13 kN) or greater thrust. [2]

Contents

A Target-type Thrust Reverser in Deployed Location on a Fokker 70 Thrust.reverser.fokker70.arp.jpg
A Target-type Thrust Reverser in Deployed Location on a Fokker 70

Mechanism

The part that provides reverse thrust for thrust reversal is the deflector doors ("bucket") with aerodynamic contour on both inner and outer surface at the tailpipe of a jet engine. The doors are in a deployed location when thrust reversal takes effect and at stowed location when otherwise. When deployed, the doors block the airflow in the end of the engine. In this case airflow passes through the inner surface and travels frontward to provide force opposite to the heading of the aircraft. When stowed, the doors seamlessly connect to the rest parts of the engine to provide a streamlined outer surface.

A pair of beams are located in the left and right of the engines with a sled in each of them. The two doors are connected to both sleds by two rods each. A hydraulic actuator connected to each sled is placed in each beam. The actuator extends to deploy the thrust reversal and retracts to stow the thrust reversal in a way that the rods push the doors to rotate about a point at the end of the tailpipe. [2] The actuator may be connected hydraulically, mechanically or electrically to the control system of the aircraft.

In operation, thrust reversers on all engines typically work together, although they can be activated separately by pilots or aircraft operators.

History

Target-type thrust reversal, particularly this design, was invented in 1968. This invention is stated to be an improvement to previous design. [2] As early as 1963, an invention called "two part thrust reversal" appeared with a similar deflector door design. However, in two part thrust reverser, the mechanism for door deployment and location of deflector doors are significantly different from those of target-type thrust reverser. The inventors (one also as inventor of target-type) states that the design can increase the reverse thrust to 50% of the original thrust. [3] In an earlier development in 1954 called "locks for jet thrust reversers", the design for thrust reversal also contain a flap device to help decelerate and the main purpose of the thrust reverser was to block airflow rather than provide reverse thrust. [4] Dated back to 1945, the first invented thrust reversal device intended to "provide a deflecting device", [5] which can be identified as the first concept for target-type thrust reverser.

Performance

The reverse-thrust ratio (ratio of backward engine thrust to forward reverse thrust) can be as high as 84%. [6] However, this result is obtained with a cowl to attach air flow in a 7° angle and a large enough "target" (deflector door) installed. A reverse-thrust ratio of 55% can be reached on a simple target without the cowl. [7] A width to height ratio of 1.6 can provide the maximum performance for cylindrical deflector doors. [6]

Advantage

Unlike other types of thrust reversals, especially cascade type thrust reversal, which typically require major redesigns when applied to different models of engines, target-type thrust reversal has a much simpler mechanism and involves lesser installation inside the engine body. Also due to the simple design, the maintenance cost can be much lower than other designs. [6]

In-flight deployment

In most occasions, thrust reversers are deployed after the aircraft touches down. However, some engines with target-type thrust reversers allow in-flight deployment, which means the thrust reversers being deployed when the aircraft is still in air. A considerable proportion of Russia-made aircraft like the Tupolev Tu-154 and Ilyushin Il-62 have this feature. Their thrust reversers can be deployed when the landing gears are still a few meters from the ground. [8] The Douglas DC-8, on the other hand, is qualified to use thrust reversal anytime in flight for speed adjustment. [9]

Application

Target-type thrust reversal is commonly applied to low bypass turbofan engines or turbojet engines. In this kind of engine with low bypass ratio, the core part of the engine produces a significantly larger part of the thrust. Therefore, the airflow from the core part must be blocked in order to produce sufficient reverse thrust. [10]

Variations

There are two major variations for this type of thrust reversal.[ citation needed ]

Screw jack mechanism

This design changes the hydraulic actuator to a mechanic actuator, specifically, screw jacks operated by motors. The inventors state that this design can reduce the weight of the engine and the maintenance cost since the system is more simplified. [11]

Pivot fairing thrust reverser

This design makes modification on the aerodynamic performance when the thrust reverser is at stowed location. It optimizes the shape of outlet nozzle from fishmouth shape to round shape. It also compresses the deployment system to reduce weight and complexity. In particular, this design moves the deflector doors from very end of the engine to a front position where it has no contact with the aerodynamic design of the outlet nozzle. [12]

Accidents

Related Research Articles

<span class="mw-page-title-main">Aircraft</span> Vehicle or machine that is able to fly by gaining support from the air

An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.

<span class="mw-page-title-main">Thrust</span> Reaction force

Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that system. The force applied on a surface in a direction perpendicular or normal to the surface is also called thrust. Force, and thus thrust, is measured using the International System of Units (SI) in newtons, and represents the amount needed to accelerate 1 kilogram of mass at the rate of 1 meter per second per second. In mechanical engineering, force orthogonal to the main load is referred to as static thrust.

<span class="mw-page-title-main">Pulsejet</span> Engine where combustion is pulsed instead of continuous

A pulsejet engine is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically. The best known example is the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.

<span class="mw-page-title-main">Turbofan</span> Airbreathing jet engine designed to provide thrust by driving a fan

A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a combination of the preceding generation engine technology of the turbojet, and a reference to the additional fan stage added. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust.

<span class="mw-page-title-main">Flight</span> Process by which an object moves, through an atmosphere or beyond it

Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere or through the vacuum of outer space. This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement.

<span class="mw-page-title-main">Ducted fan</span> Air moving arrangement

In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing (VTOL) applications it is also known as a shrouded rotor.

<span class="mw-page-title-main">Thrust vectoring</span> Facet of ballistics and aeronautics

Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the vehicle.

<span class="mw-page-title-main">Blown flap</span> High-lift device on some aircraft wings

Blown flaps or jet flaps are powered aerodynamic high-lift devices used on the wings of certain aircraft to improve their low-speed flight characteristics. They use air blown through nozzles to shape the airflow over the rear edge of the wing, directing the flow downward to increase the lift coefficient. There are a variety of methods to achieve this airflow, most of which use jet exhaust or high-pressure air bled off of a jet engine's compressor and then redirected to follow the line of trailing-edge flaps.

<span class="mw-page-title-main">Thrust reversal</span> Temporary diversion of an aircraft engines thrust

Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to help slow down just after touch-down, reducing wear on the brakes and enabling shorter landing distances. Such devices affect the aircraft significantly and are considered important for safe operations by airlines. There have been accidents involving thrust reversal systems, including fatal ones.

<span class="mw-page-title-main">Aircraft flight control system</span> How aircraft are controlled

A conventional fixed-wing aircraft flight control system (AFCS) consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered flight controls as they change speed.

<span class="mw-page-title-main">Spoiler (aeronautics)</span> Device for reducing lift and increasing drag on aircraft wings

In aeronautics, a spoiler is a device which intentionally reduces the lift component of an airfoil in a controlled way. Most often, spoilers are plates on the top surface of a wing that can be extended upward into the airflow to spoil the streamline flow. By so doing, the spoiler creates a controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag without disrupting the lift distribution across the wing span, while spoilers disrupt the lift distribution as well as increasing drag.

A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, or gas generator, from a jet engine.

<span class="mw-page-title-main">Airplane</span> Powered, flying vehicle with wings

An airplane or aeroplane, informally plane, is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for airplanes includes recreation, transportation of goods and people, military, and research. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion tonne-kilometers of cargo annually, which is less than 1% of the world's cargo movement. Most airplanes are flown by a pilot on board the aircraft, but some are designed to be remotely or computer-controlled such as drones.

<span class="mw-page-title-main">Compressor stall</span> Gas turbine phenomenon

A compressor stall is a local disruption of the airflow in the compressor of a gas turbine or turbocharger. A stall that results in the complete disruption of the airflow through the compressor is referred to as a compressor surge. The severity of the phenomenon ranges from a momentary power drop barely registered by the engine instruments to a complete loss of compression in case of a surge, requiring adjustments in the fuel flow to recover normal operation.

<span class="mw-page-title-main">Podded engine</span> Externally mounted aircraft engine

A podded engine is a jet engine that has been built up and integrated in its nacelle. This may be done in a podding facility as part of an aircraft assembly process. The nacelle contains the engine, engine mounts and parts which are required to run the engine in the aircraft, known as the EBU. The nacelle consists of an inlet, an exhaust nozzle and a cowling which opens for access to the engine accessories and external tubing. The exhaust nozzle may include a thrust reverser. The podded engine is a complete powerplant, or propulsion system, and is usually attached below the wing on large aircraft like commercial airliners or to the rear fuselage on smaller aircraft such as business jets.

<span class="mw-page-title-main">Propeller (aeronautics)</span> Aircraft propulsion component

In aeronautics, an aircraft propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.

Supermaneuverability is the capability of fighter aircraft to execute tactical maneuvers that are not possible with purely aerodynamic techniques. Such maneuvers can involve controlled side-slipping or angles of attack beyond maximum lift.

<span class="mw-page-title-main">Rolls-Royce/Snecma Olympus 593</span> 1960s British/French turbojet aircraft engine

The Rolls-Royce/Snecma Olympus 593 was an Anglo-French turbojet with reheat, which powered the supersonic airliner Concorde. It was initially a joint project between Bristol Siddeley Engines Limited (BSEL) and Snecma, derived from the Bristol Siddeley Olympus 22R engine. Rolls-Royce Limited acquired BSEL in 1966 during development of the engine, making BSEL the Bristol Engine Division of Rolls-Royce.

<span class="mw-page-title-main">Aircraft systems</span> Overview article of aircraft systems

Aircraft systems are those required to operate an aircraft efficiently and safely. Their complexity varies with the type of aircraft.

<span class="mw-page-title-main">Components of jet engines</span> Brief description of components needed for jet engines

This article briefly describes the components and systems found in jet engines.

References

  1. Federal Aviation Administration (2011). Airplane Flying Handbook (FAA-H-8083-3A). Skyhorse Publishing. p. 15-14. ISBN   978-1-61608-338-0 . Retrieved May 4, 2022.
  2. 1 2 3 A, Buell Charles; H, Feld Sam; C, Isaacson Gary (Dec 29, 1970), Target-type thrust reverser , retrieved 2016-10-23
  3. W, Colebrook Ross; H, Feld Sam; F, Geotz Gerald (Jan 12, 1965), Two part thrust reverser , retrieved 2016-10-24
  4. Stavert, Harry (Feb 5, 1957), Locks for jet thrust reversers , retrieved 2016-10-24
  5. Oskar, Lundberg Bo Klas (Dec 9, 1952), Reverse thrust arrangement for braking jet-propelled aircraft , retrieved 2016-10-24
  6. 1 2 3 Steffen, Fred W.; McArdle, Jack G. (11 January 1956). "Performance characteristics of cylindrical target-type thrust reversers" (PDF). National Advisory Committee for Aeronautics.
  7. Povolny, John H.; Steffen, Fred W.; McArdle, Jack G. (February 1956). "Summary of scale-model thrust-reverser investigation" (PDF). National Advisory Committee for Aeronautics.
  8. "In-Flight Thrust Reverser Usage - Airliners.net". www.airliners.net. Retrieved 2016-10-31.
  9. Martinez-Guridi, G.; Hall, R. E.; Fullwood, R. R. (1997-05-14). "On the Safety of Aircraft Systems: A Case Study". Brookhaven National Lab., Upton, NY (United States). doi: 10.2172/567487 .{{cite journal}}: Cite journal requires |journal= (help)
  10. Hamid, Hedayat U.; Margason, Richard J.; Hardy, Gordon (June 1995). "Investigation of Wing Upper Surface Flow-Field Disturbance Due to NASA DC-8-72 In-flight Inboard Thrust Reverser Deployment" (PDF). National Aeronautics and Space Administration.
  11. Timms, Richard H. (May 28, 1985), Aircraft thrust reverser mechanism , retrieved 2016-10-24
  12. Modglin, Rodger L.; Peters, Frederick H. (Dec 3, 2002), Pivot fairing thrust reverser , retrieved 2016-10-24
  13. Administration, Federal Aviation. "Lessons Learned". lessonslearned.faa.gov. Retrieved 2016-11-06.