Landing gear is the undercarriage of an aircraft or spacecraft and may be used for either takeoff or landing. For aircraft it is both, it was formerly called alighting gear by some manufacturers, such as the Glenn L. Martin Company. For aircraft, the landing gear supports the craft when it is not flying, allowing it to take off and taxi without damage. Wheels are used but skids, floats or a combination of these and other elements can be deployed depending both on the surface and on whether the craft only operates vertically or is able to taxi along the surface. Faster aircraft have retractable undercarriages, which fold away during flight to reduce air resistance or drag. For launch vehicles and spacecraft landers, the landing gear is designed to support the vehicle only post-flight, are not used for takeoff or surface movement. Aircraft landing gear includes wheels equipped with simple shock absorbers, or more advanced air/oil oleo struts, for runway and rough terrain landing; some aircraft floats for water, and/or skids or pontoons.
It represents 2.5 to 5% of the MTOW and 1.5 to 1.75% of the aircraft cost but 20% of the airframe direct maintenance cost. The undercarriage is 4–5% of the takeoff mass and can reach 7%. Wheeled undercarriages come in two types: conventional or "taildragger" undercarriage, where there are two main wheels towards the front of the aircraft and a single, much smaller, wheel or skid at the rear; the taildragger arrangement was common during the early propeller era, as it allows more room for propeller clearance. Most modern aircraft have tricycle undercarriages. Taildraggers are considered harder to land and take off, require special pilot training. Sometimes a small tail wheel or skid is added to aircraft with tricycle undercarriage, in case of tail strikes during take-off; the Concorde, for instance, had a retractable tail "bumper" wheel, as delta winged aircraft need a high angle when taking off. Both Boeing's largest WWII bomber, the B-29 Superfortress, the 1960s-introduced Boeing 727 trijet airliner each have a retractable tail bumper.
Some aircraft with retractable conventional landing gear have a fixed tailwheel, which generates minimal drag and improves yaw stability in some cases. Another arrangement sometimes used is central nose gear with outriggers on the wings; this may be done where there is no convenient location on either side to attach the main undercarriage or to store it when retracted. Examples include the Harrier Jump Jet; the B-52 bomber uses a similar arrangement, except that each end of the fuselage has two sets of wheels side by side. To decrease drag in flight some undercarriages retract into the wings and/or fuselage with wheels flush against the surface or concealed behind doors. If the wheels rest protruding and exposed to the airstream after being retracted, the system is called semi-retractable. Most retraction systems are hydraulically operated, though some are electrically operated or manually operated; this adds complexity to the design. In retractable gear systems, the compartment where the wheels are stowed are called wheel wells, which may diminish valuable cargo or fuel space.
] Pilots confirming that their landing gear is down and locked refer to "three greens" or "three in the green.", a reference to the electrical indicator lights from the nosewheel/tailwheel and the two main gears. Blinking green lights or red lights indicate the gear is in transit and neither up and locked or down and locked; when the gear is stowed up with the up-locks secure, the lights extinguish to follow the dark cockpit philosophy. Multiple redundancies are provided to prevent a single failure from failing the entire landing gear extension process. Whether electrically or hydraulically operated, the landing gear can be powered from multiple sources. In case the power system fails, an emergency extension system is always available; this may take the form of a manually operated crank or pump, or a mechanical free-fall mechanism which disengages the uplocks and allows the landing gear to fall due to gravity. Some high-performance aircraft may feature a pressurized-nitrogen back-up system; as aircraft grow larger, they employ more wheels to cope with the increasing weights.
The earliest "giant" aircraft placed in quantity production, the Zeppelin-Staaken R. VI German World War I long-range bomber of 1916, used a total of eighteen wheels for its undercarriage, split between two wheels on its nose gear struts, a total of sixteen wheels on its main gear units — split into four side-by-side quartets each, two quartets of wheels per side — under each tandem engine nacelle, to support its loaded weight of 12 metric tons. Multiple "tandem wheels" on an aircraft — for cargo aircraft, mounted to the fuselage lower sides as retractable main gear units on modern designs — were first seen during World War II, on the experimental German Arado Ar 232 cargo aircraft, which used a row of elev
Elevators are flight control surfaces at the rear of an aircraft, which control the aircraft's pitch, therefore the angle of attack and the lift of the wing. The elevators are hinged to the tailplane or horizontal stabilizer, they may be the only pitch control surface present, sometimes located at the front of the aircraft or integrated into a rear "all-moving tailplane" called a slab elevator or stabilator. The horizontal stabilizer creates a downward force which balances the nose down moment created by the wing lift force, which applies at a point situated aft of the airplane's center of gravity; the effects of drag and changing the engine thrust may result in pitch moments that need to be compensated with the horizontal stabilizer. Both the horizontal stabilizer and the elevator contribute to pitch stability, but only the elevators provide pitch control, they do so by decreasing or increasing the downward force created by the stabilizer: an increased downward force, produced by up elevator, forces the tail down and the nose up.
At constant speed, the wing's increased angle of attack causes a greater lift to be produced by the wing, accelerating the aircraft upwards. The drag and power demand increase. At constant speed, the decrease in angle of attack reduces the lift, accelerating the aircraft downwards. On many low-speed aircraft, a trim tab is present at the rear of the elevator, which the pilot can adjust to eliminate forces on the control column at the desired attitude and airspeed. Supersonic aircraft have all-moving tailplanes, because shock waves generated on the horizontal stabilizer reduce the effectiveness of hinged elevators during supersonic flight. Delta winged aircraft combine ailerons and elevators –and their respective control inputs– into one control surface called an elevon. Elevators are part of the tail, at the rear of an aircraft. In some aircraft, pitch-control surfaces are in the front, ahead of the wing. In a two-surface aircraft this type of configuration is called a tandem wing; the Wright Brothers' early aircraft were of the canard type.
Some early three surface aircraft had front elevators. Several technology research and development efforts exist to integrate the functions of aircraft flight control systems such as ailerons, elevons and flaperons into wings to perform the aerodynamic purpose with the advantages of less: mass, drag, inertia and radar cross section for stealth; these may be used in 6th generation fighter aircraft. Two promising approaches are flexible wings, fluidics. In flexible wings, much or all of a wing surface can change shape in flight to deflect air flow; the X-53 Active Aeroelastic Wing is a NASA effort. The Adaptive Compliant Wing is a commercial effort. In fluidics, forces in vehicles occur via circulation control, in which larger more complex mechanical parts are replaced by smaller simpler fluidic systems where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. In this use, fluidics promises lower mass and low inertia and response times, simplicity.
Rudder Aileron Aircraft Pitch Motion
Salmson water-cooled aero-engines
The Salmson water-cooled aero-engines, produced in France by Société des Moteurs Salmson from 1908 until 1920, were a series of pioneering aero-engines: unusually combining water-cooling with the radial arrangement of their cylinders. Henri Salmson, a manufacturer of water pumps, was engaged by Georges Marius Henri-Georges Canton and Pierre Unné, a pair of Swiss engineers, to produce engines to their design, their initial efforts were on barrel engines, but these failed to meet expectations due to low reliability and high fuel consumption caused by internal friction. A new 7-cylinder water-cooled radial design was developed by Canton and Unné; the range was expanded to produce 9-cylinder models, two-row 14-cylinder and 18-cylinder engines. By 1912 the Salmson A9 was producing around 120 brake horsepower; the engines were produced at Salmson's factory at Billancourt, expanded during the First World War, a second factory was opened at Villeurbanne. The Salmson- series of water-cooled engines were built by licensees in Russia and in Great Britain at the Dudbridge Iron Works Limited at Stroud in Gloucestershire between 1914 and 1918.
Data from:LA SOCIETE DES MOTEURS SALMSON Aircraft powered by Salmson water-cooled engines included: Salmson 9A Salmson-Moineau S. M.1 Salmson-Moineau S. M.2Salmson 9B Short S.74 Short type 135 Short type 830Salmson 9CFarman 60Salmson 9MBlackburn type L Bréguet U2 Breguet 14 prototype Voisin LA 3Salmson 9P Farman HF.27 Voisin LA 5Salmson 9R Anatra DS Lebed 12Salmson 9Z Besson H-5 Caudron C.23 Farman HF.30 Farman 60 Hanriot HD.3 Hanriot H.26 Latécoère 3 Salmson 2 Berline Salmson 2A2 Vickers Vimy prototype Voisin TriplaneSalmson 2M7 Kennedy Giant Sopwith type C Sopwith Bat Boat II Short type 166 Sopwith type 860 Wight NavyplaneSalmson 18CmHanriot H.25 Some sources named the radial versions as Salmson which refers to the Swiss engineers which engaged Salmson to build engines to their designs. Data from Type: 9-cyl radial engine Bore: 125 mm Stroke: 170 mm Displacement: 18.7 l Designer: Georges Marius Henri-Georges Canton and Pierre Unné Cooling system: Water with radiators Power output: 186.4 kW at 1400rpm Salmson air-cooled aero-engines List of aircraft engines La société des moteurs Salmson at Hydro-Retro.
Net Salmson Z-9 at the Aircraft Engine Historical Society Angelucci, Enzo. The Rand McNally encyclopedia of military aircraft, 1914-1980; the Military Press. P. 103. ISBN 0-517-41021 4. Hirschauer, Louis. L'Année Aéronautique: 1920-1921. Paris: Dunod. P. 131
A tailplane known as a horizontal stabiliser, is a small lifting surface located on the tail behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabilizer and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout; the function of the tailplane is to provide control. In particular, the tailplane helps adjust for changes in position of the center of pressure or center of gravity caused by changes in speed and attitude, fuel consumption, or dropping cargo or payload; the tailplane comprises the tail-mounted fixed horizontal movable elevator. Besides its planform, it is characterised by: Number of tailplanes - from 0 to 3 Location of tailplane - mounted high, mid or low on the fuselage, fin or tail booms. Fixed movable elevator surfaces, or a single combined stabilator or flying tail.
Some locations have been given special names: Cruciform: mid-mounted on the fin T-tail: high-mounted on the fin A wing with a conventional aerofoil profile makes a negative contribution to longitudinal stability. This means that any disturbance which raises the nose produces a nose-up pitching moment which tends to raise the nose further. With the same disturbance, the presence of a tailplane produces a restoring nose-down pitching moment, which may counteract the natural instability of the wing and make the aircraft longitudinally stable; the longitudinal stability of an aircraft may change when it is flown "hands-off". In addition to giving a restoring force a tailplane gives damping; this is caused by the relative wind seen by the tail as the aircraft rotates around the center of gravity. For example, when the aircraft is oscillating, but is momentarily aligned with the overall vehicle's motion, the tailplane still sees a relative wind, opposing the oscillation. Depending on the aircraft design and flight regime, its tailplane may create positive lift or negative lift.
It is sometimes assumed that on a stable aircraft this will always be a net down force, but this is untrue. On some pioneer designs, such as the Bleriot XI, the center of gravity was between the neutral point and the tailplane, which provided positive lift; however this arrangement can be unstable and these designs had severe handling issues. The requirements for stability were not understood until shortly before World War I - the era within which the British Bristol Scout light biplane was designed for civilian use, with an airfoiled lifting tail throughout its production run into the early World War I years and British military service from 1914-1916 — when it was realised that moving the center of gravity further forwards allowed the use of a non-lifting tailplane in which the lift is nominally neither positive nor negative but zero, which leads to more stable behaviour. Examples of aircraft from World War I and onwards into the interwar years that had positive lift tailplanes include, the Sopwith Camel, Charles Lindbergh's Spirit of St. Louis, the Gee Bee Model R Racer - all aircraft with a reputation for being difficult to fly, the easier-to-fly Fleet Finch two-seat Canadian trainer biplane, itself possessing a flat-bottom airfoiled tailplane unit not unlike the earlier Bristol Scout.
But with care a lifting tailplane can be made stable. An example is provided by the Bachem Ba 349 Natter VTOL rocket-powered interceptor, which had a lifting tail and was both stable and controllable in flight. In many modern conventional aircraft, the center of gravity is placed ahead of the neutral point; the wing lift exerts a pitch-down moment around the centre of gravity, which must be balanced by a pitch-up moment from the tailplane. A disadvantage is. Using a computer to control the elevator allows aerodynamically unstable aircraft to be flown in the same manner. Aircraft such as the F-16 are flown with artificial stability; the advantage of this is a significant reduction in drag caused by the tailplane, improved maneuverability. At transonic speeds, an aircraft can experience a shift rearwards in the center of pressure due to the buildup and movement of shockwaves; this causes. Significant trim force may be needed to maintain equilibrium, this is most provided using the whole tailplane in the form of an all-flying tailplane or stabilator.
A tailplane has some means allowing the pilot to control the amount of lift produced by the tailplane. This in turn causes a nose-up or nose-down pitching moment on the aircraft, used to control the aircraft in pitch. Elevator A conventional tailplane has a hinged aft surface called an elevator, Stabilator or all-moving tail In transonic flight shock waves generated by the front of the tailplane render any elevator unusable. An all-moving tail was developed by the British for the Miles M.52, but first saw actual transonic flight on the Bell X-1. This saved the program from a time-consuming rebuild of the aircraft. Transonic and supersonic aircraft now have all-moving tailplanes to counterac
Vélizy – Villacoublay Air Base
Vélizy – Villacoublay Air Base is a French Air Force (French: Armée de l'Air base. The base is located 2 miles southeast of Vélizy-Villacoublay; the base is the home station for the following units: Escadron de transport, d'entrainement et de calibration 00.065 Staffs of the northern area, the command of the air force of projection and of the command air of the monitoring systems, of information and communications. Helicopter Squadron 03/067 Commando Parachute Unit N20 Other non-French Air Force Units. Aircraft assigned to the base are: 1 Airbus A330-200 2 Airbus A319 3 Eurocopter AS332 Super Puma 1 Dassault Falcon 20 8 AS 555UN FENNEC 4 Dassault Falcon 50 2 Dassault Falcon 900 6 TBM700 Villacoublay Air Base was built prior to World War II as a French Air Force facility. Seized by the Germans in June 1940 during the Battle of France, Villacoublay was used as a Luftwaffe military airfield during the occupation. Known units assigned: Kampfgeschwader 55 21 June 1940 – 16 June 1941 Heinkel He 111P/H Kampfgeschwader 27 Jun-July 1940 Heinkel He 111P Aufklärungsgruppe 14 Nov 1940-May 1941 Junkers Ju 88 Jagdfliegerschule 5 Jun 1941-24 February 1943 Messerschmitt Bf 109 Jagdgeschwader 105 25 February-31 August 1943 Messerschmitt Bf 109 Jagdgeschwader 54 7 June-5 September 1944 Focke-Wulf Fw 190AKG 55 and KG 27 took part in the Battle of Britain.
It was attacked on several occasions by heavy bombers of both the United States Army Air Force Eighth and Fifteenth Air Forces during 1943 and early 1944. Due to its use as a base for Bf 109 and Fw 190 interceptors, Villacoublay was attacked by USAAF Ninth Air Force B-26 Marauder medium bombers and P-47 Thunderbolts with 500-pound General-Purpose bombs; the attacks were timed to have the maximum effect possible to keep the interceptors pinned down on the ground and be unable to attack the heavy bombers. The P-51 Mustang fighter-escort groups of Eighth Air Force would drop down on their return to England and attack the base with a fighter sweep and attack any target of opportunity to be found at the airfield, it was liberated by Allied ground forces about 27 August 1944 during the Northern France Campaign. The USAAF IX Engineer Command 818th Engineer Aviation Battalion began clearing the base of mines and destroyed Luftwaffe aircraft. Subsequently, Villacoublay became a USAAF Ninth Air Force combat airfield, designated as "A-42" about 30 August, only a few days after its capture from German forces.
The 48th Fighter Group moved into the repaired air base, flying P-47 Thunderbolts from 29 August until 15 September 1944. The combat unit moved east along with the advancing Allied forces and Villacoublay became a supply and maintenance base for combat aircraft, becoming the home of the 370th Air Service Group and several Air Materiel squadrons from Air Technical Service Command, it was given the designation of AAF-180. In addition, numerous C-47 Skytrain squadrons moved in and out, supporting airborne operations, including Operation Varsity, Allied airborne crossing of the Rhine in March 1945. Robert Zeller of Zeller-Hoff-Zeller was stationed there from 1945 to 1946 during World War 2. After the war ended, Villacoublay remained under American control, designated as AAF Station Villacoublay, it was assigned to the United States Air Forces in Europe as a transport base by the C-47 Skytrain-equipped 314th Troop Carrier Group. It remained under USAFE control until 31 August 1946; the base has been rebuilt since with war.
The prewar/wartime runway, 11/29 is now closed and a new east-west 6000' runway 09/27 laid down along with expanded aircraft parking areas and multiple hangars as part of an operational NATO air base. After 1964 for a period, the base was the home to the Military Air Transport Command, for a period, to the Air Force Training Command. Advanced Landing Ground This article incorporates public domain material from the Air Force Historical Research Agency website http://www.afhra.af.mil/. French Senate Document, LIST AIR BASES, AND THEIR MAIN ACTIVITIES Airport information for LFPV at Great Circle Mapper. Airport information for LFPV at World Aero Data. Data current as of October 2006
Angle of incidence (aerodynamics)
On fixed-wing aircraft, the angle of incidence is the angle between the chord line of the wing where the wing is mounted to the fuselage, a reference axis along the fuselage. The angle of incidence is fixed in the design of the aircraft, with rare exceptions, cannot be varied in flight; the term can be applied to horizontal surfaces in general for the angle they make relative the longitudinal axis of the fuselage. The figure to the right shows a side view of an airplane; the extended chord line of the wing root makes an angle with the longitudinal axis of the aircraft. Wings are mounted at a small positive angle of incidence, to allow the fuselage to have a low angle with the airflow in cruising flight. Angles of incidence of about 6° are common on most general aviation designs. Other terms for angle of incidence in this context are rigging angle and rigger's angle of incidence, it should not be confused with the angle of attack, the angle the wing chord presents to the airflow in flight. Note that some ambiguity in this terminology exists, as some engineering texts that focus on the study of airfoils and their medium may use either term when referring to angle of attack
The Ponnier D. III was a French monoplane racing aircraft, designed to compete in the 1913 Gordon Bennett Trophy race, it finished a close second. During 1911 René Hanriot hired Alfred Pagny at Nieuport, as a designer. After Hanriot military prototypes failed to win orders at the Concours Militaire in late 1911 he sold his aircraft interests to another of his designers, Louis Alfred Ponnier. Pagny designed two similar single seat monoplanes for Hanriot and Ponnier, the Hanriot D. I and the Ponnier D. III. III, his designs reflected Nieuport practice with the replacement of Hanriot's graceful boat-like shell fuselages with flat sided, deep chested ones. The Ponnier D. III was a single seat, mid wing monoplane designed to compete in the 1913 Gordon Bennett Trophy race. Pairs of landing wires on each side met over the fuselage at a pyramidal four strut pylon and parallel flying wires went to the lower fuselage. An oil deflecting cowling, open at the bottom, surrounded the powerful double row, fourteen cylinder Gnome Lambda-Lambda rotary engine, which delivered 160 hp to a 2 m diameter propeller.
The oval, open cockpit was placed at just aft of the pylon centre. It had a finless rudder at the extreme rear of the fuselage and a straight edged tailplane mounted on the upper fuselage ahead of it; the elevators were interconnected, controlled by central wires. The D. III had a fixed, conventional undercarriage with mainwheels on a single axle mounted to the fuselage by pairs of wire cross-braced V-struts, plus a simple elliptical leaf spring tailskid. Jane's All the World's Aircraft 1913 describes a longer Hanriot D. III with a 100 hp Gnome engine; the D. III participated in the Gordon-Bennett Trophy race piloted by Emile Védrines; the elimination race over 100 km left four aircraft in the final, flown over 200 km on Monday 29 September. After an hour's flight the Ponnier finished second, just 66 seconds behind Maurice Prévost in a Deperdussin Monocoque. Data from Flight 22 November 1913General characteristics Crew: One Length: 5.41 m Wingspan: 7.16 m Wing area: 8.7 m2 Gross weight: 500 kg Powerplant: 1 × Gnome Lambda-Lambda 14-cylinder, two row rotary engine, 120 kW Propellers: 2-bladed, 2.08 m diameterPerformance Maximum speed: 200 km/h