In aeronautics, a spoiler (sometimes called a lift spoiler or lift dumper) 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.
Spoilers fall into two categories: those that are deployed at controlled angles during flight to increase descent rate or control roll, and those that are fully deployed immediately on landing to greatly reduce lift ("lift dumpers") and increase drag. In modern fly-by-wire aircraft, the same set of control surfaces serve both functions.
Spoilers were used by most gliders (sailplanes) until the 1960s to control their rate of descent and thus achieve a controlled landing. Since then, spoilers on gliders have almost entirely been replaced by airbrakes, usually of the Schempp-Hirth type. Spoilers and airbrakes enable the glide angle to be altered during the approach while leaving the speed unchanged.
Airliners are almost always fitted with spoilers. Spoilers are used to increase descent rate without increasing speed. Their use is often limited, however, as the turbulent airflow that develops behind them causes noise and vibration, which may cause discomfort to passengers. Spoilers may also be differentially operated for roll control instead of ailerons; Martin Aircraft was the first company to develop such spoilers in 1948. [1] On landing, however, the spoilers are nearly always fully deployed to help slow the aircraft. The increase in form drag created by the spoilers directly assists the braking effect. However, the most gain comes as the spoilers cause a dramatic loss of lift and hence the weight of the aircraft is transferred from the wings to the undercarriage, allowing the wheels to be mechanically braked with less tendency to skid.
In air-cooled piston engine aircraft, spoilers may be needed to avoid shock cooling the engines. In a descent without spoilers, air speed is increased and the engine will be at low power, producing less heat than normal. The engine may cool too rapidly, resulting in stuck valves, cracked cylinders or other problems. Spoilers alleviate the situation by allowing the aircraft to descend at a desired rate while letting the engine run at a power setting that keeps it from cooling too quickly (especially true for turbocharged piston engines, which generate higher temperatures than normally aspirated engines).
Spoiler controls can be used for roll control (outboard or mid-span spoilers) or descent control (inboard spoilers).
Some aircraft use spoilers in combination with or in lieu of ailerons for roll control, primarily to reduce adverse yaw when rudder input is limited by higher speeds. For such spoilers the term spoileron has been coined. In the case of a spoileron, in order for it to be used as a control surface, it is raised on one wing only, thus decreasing lift and increasing drag, causing roll and yaw. Eliminating dedicated ailerons also avoids the problem of control reversal and allows flaps to occupy a greater portion of the wing trailing edge.
Almost all modern jet airliners are fitted with inboard lift spoilers which are used together during descent to increase the rate of descent and control speed. Some aircraft use lift spoilers on landing approach to control descent without changing the aircraft's attitude.
One jet airliner not fitted with lift spoilers was the Douglas DC-8 which used reverse thrust in flight on the two inboard engines to control descent speed (however the aircraft was fitted with lift dumpers). The Lockheed Tristar was fitted with a system called Direct Lift Control that used the spoilers on landing approach to control descent.
Airbus aircraft with fly-by-wire control utilise wide-span spoilers for descent control, spoilerons, gust alleviation, and lift dumpers. Especially on landing approach, the full width of spoilers can be seen controlling the aircraft's descent rate and bank.
Lift dumpers are a special type of spoiler extending along much of the wing's length and designed to dump as much lift as possible on landing. Lift dumpers have only two positions, deployed and retracted. Lift dumpers have three main functions: putting most of the weight of the aircraft on the wheels for maximum braking effect, increasing form drag, and preventing aircraft 'bounce' on landing.
Lift dumpers are almost always deployed automatically on touch down. The flight deck control has three positions: off, automatic ('armed'), and manual (rarely used). On landing approach 'automatic' is selected and, on touchdown, a sensor called a weight-on-wheels switch signals the lift dumpers to be raised. The flight control spoilers are also raised as additional lift dumpers.
Virtually all modern jet aircraft are fitted with lift dumpers. The British Aerospace 146 is fitted with particularly wide-span spoilers to generate additional drag and make reverse thrust unnecessary.
A number of accidents have been caused either by inadvertently deploying lift dumpers on landing approach, or forgetting to set them to 'automatic'.
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil, and Reynolds number.
A short takeoff and landing (STOL) aircraft is a conventional fixed-wing aircraft that has short runway requirements for takeoff and landing. Many STOL-designed aircraft also feature various arrangements for use on airstrips with harsh conditions. STOL aircraft, including those used in scheduled passenger airline operations, have also been operated from STOLport airfields which feature short runways.
Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or "splashdown" as well. A normal aircraft flight would include several parts of flight including taxi, takeoff, climb, cruise, descent and landing.
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator and the aileron, hence the name. They are frequently used on tailless aircraft such as flying wings. An elevon that is not part of the main wing, but instead is a separate tail surface, is a stabilator.
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.
A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to reduce the take-off distance and the landing distance. Flaps also cause an increase in drag so they are retracted when not needed.
In aeronautics, air brakes or speed brakes are a type of flight control surface used on an aircraft to increase the drag on the aircraft. Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed.
The de Havilland Canada DHC-7, popularly known as the Dash 7, is a turboprop-powered regional airliner with short take-off and landing (STOL) performance. It first flew in 1975 and remained in production until 1988 when the parent company, de Havilland Canada, was purchased by Boeing in 1986 and later sold to Bombardier. In 2006 Bombardier sold the type certificate for the aircraft design to Victoria-based manufacturer Viking Air.
Aircraft flight mechanics are relevant to fixed wing and rotary wing (helicopters) aircraft. An aeroplane, is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
The Learjet 25 is an American ten-seat, twin-engine, high-speed business jet aircraft manufactured by Learjet. It is a stretched version of the Learjet 24.
In aeronautics, spoilerons are spoilers that can be used asymmetrically as flight control surfaces to provide roll control.
On 22 November 2003, shortly after takeoff from Baghdad, Iraq, an Airbus A300B2-200F cargo plane, registered OO-DLL and owned by European Air Transport, was struck on the left wing by a surface-to-air missile while on a scheduled flight to Muharraq, Bahrain. Severe wing damage resulted in a fire and complete loss of hydraulic flight control systems. Because outboard left wing fuel tank 1A was full at takeoff, no fuel-air vapour explosion occurred. Liquid jet fuel dropped away as 1A disintegrated. Inboard fuel tank 1 was pierced and leaking.
Atlantic Airways Flight 670 was a crash following a runway overrun of a British Aerospace 146-200A at 07:32 on 10 October 2006 at Stord Airport, Sørstokken, Norway. The aircraft's spoilers failed to deploy, causing inefficient braking. The Atlantic Airways aircraft fell down the steep cliff at the end of the runway at slow speed and burst into flames, killing four of sixteen people on board.
A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding. This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailplanes are aerodynamically streamlined and so can fly a significant distance forward for a small decrease in altitude.
Several aviation incidents and accidents have occurred in which the control surfaces of an aircraft became disabled, often due to failure of hydraulic systems or the flight control system. Other incidents have occurred where controls were not functioning correctly prior to take-off, either due to maintenance or pilot error, and controls can become inoperative from extreme weather conditions. Aircraft are not designed to be flown in such circumstances; however, a small number of pilots have had some success in flying and landing aircraft with disabled controls.
On April 4, 1955, a United Airlines Douglas DC-6 named Mainliner Idaho crashed shortly after taking off from Long Island MacArthur Airport, in Ronkonkoma, Islip, New York, United States.
Red Wings Airlines Flight 9268 was a Tupolev Tu-204-100 passenger jet that on 29 December 2012 crashed on landing at Moscow Vnukovo Airport, Russia, following a repositioning flight from Pardubice Airport, Czech Republic. There were no passengers on board, but 5 of the 8 crew members were killed when the aircraft hit a ditch and highway structures after overrunning the runway.
The minimum control speed (VMC) of a multi-engine aircraft is a V-speed that specifies the calibrated airspeed below which directional or lateral control of the aircraft can no longer be maintained, after the failure of one or more engines. The VMC only applies if at least one engine is still operative, and will depend on the stage of flight. Indeed, multiple VMCs have to be calculated for landing, air travel, and ground travel, and there are more still for aircraft with four or more engines. These are all included in the aircraft flight manual of all multi-engine aircraft. When design engineers are sizing an airplane's vertical tail and flight control surfaces, they have to take into account the effect this will have on the airplane's minimum control speeds.
Propair Flight 420 (PRO420) was a scheduled domestic passenger flight from Montreal, Quebec to Peterborough, Ontario. The flight was carried out by Propair, a charter airline based in Rouyn-Noranda, Quebec, using a Fairchild Metroliner SA226. On 18 June 1998, the aircraft suffered an in-flight fire shortly after take-off from Dorval and the crew elected to conduct an emergency landing at Montréal–Mirabel International Airport. The intense heat of the fire caused a structural failure in the left wing during the landing and the aircraft crashed, resulting in the deaths of all 11 passengers and crew on board.
This article needs additional citations for verification .(January 2009) |
{{cite web}}
: CS1 maint: unfit URL (link)