Push-pull configuration
Encyclopedia
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
constructed with a push-pull configuration has a mixture of forward-mounted (tractor
Tractor configuration
thumb|right|[[Evektor-Aerotechnik|Aerotechnik EV97A Eurostar]], a tractor configuration aircraft, being pulled into position by its pilot for refuelling....
) propeller
Propeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...
s and backward-mounted (pusher
Pusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
) propellers.
Historical
An early example of a "push-pull" aircraft was the Caproni Ca.1 which had two wing-mounted tractor propellers and one centre-mounted pusher propeller.Claudius Dornier
Claudius Dornier
Claude Honoré Desiré Dornier born in Kempten im Allgäu was a German airplane builder and founder of Dornier GmbH...
was the first aviation designer to heartily embrace the concept for production aircraft, as many of his flying boat
Flying boat
A flying boat is a fixed-winged seaplane with a hull, allowing it to land on water. It differs from a float plane as it uses a purpose-designed fuselage which can float, granting the aircraft buoyancy. Flying boats may be stabilized by under-wing floats or by wing-like projections from the fuselage...
s used variations of the tandem "push-pull" engine layout :
- Dornier WalDornier Do JThe Dornier Do J Wal was a twin-engine German flying boat of the 1920s designed by Dornier Flugzeugwerke. The Do J was designated the Do 16 by the Reich Air Ministry under its aircraft designation system of 1933....
(1922) - Dornier Do XDornier Do XThe Dornier Do X was the largest, heaviest, and most powerful flying boat in the world when it was produced by the Dornier company of Germany in 1929. First conceived by Dr. Claudius Dornier in 1924, planning started in late 1925 and after over 240,000 work hours it was completed in June 1929...
(1929) - Dornier Do 18Dornier Do 18The Dornier Do 18 was a development of the Do 16 flying boat. It was developed for the Luftwaffe, but Lufthansa got 5 aircraft and used these for tests between the Azores and the North American continent in 1936 and on their mail route over the South Atlantic from 1937 to 1939.27–29 March 1938 a...
(1935) - Dornier Do 26Dornier Do 26The Dornier Do 26 was an all-metal gull winged flying boat produced before and during World War II by Dornier Flugzeugwerke of Germany.It was operated by a crew of four and was intended to carry a payload of 500 kg or four passengers on the Lisbon to New York route.-Design and development:The...
(1938)
Configuration
Push-pull designs have the engines mounted above the wing as Dornier flying boats or more commonly on a shorter fuselageFuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
than conventionnal one, as for Rutan Defiant or Voyager
Rutan Defiant
|-References:*...
canard designs. Twin boomers such as the Cessna Skymaster
Cessna Skymaster
The Cessna Skymaster is a United States twin-engine civil utility aircraft built in a push-pull configuration. Its engines are mounted in the nose and rear of its pod-style fuselage. Twin booms extend aft of the wings to the vertical stabilizers, with the rear engine between them. The horizontal...
and Adam A500
Adam A500
The Adam A500 is a six-seat civil utility aircraft that was produced by Adam Aircraft Industries. The aircraft is of pod-and-boom, push-pull configuration with its two Continental TSIO-550-E piston engines mounted to provide centerline thrust....
have the aircraft's tail suspended via twin boom
Twin boom
Twin-boom aircraft have their tailplanes and vertical stabilizers mounted on the tail of either two fuselages or on two booms fixed to either both sides of the single fuselage, the wings or the engine nacelles.The reason for this design choice may be:...
s behind the pusher propeller. In contrast, both the World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
-era Dornier Do 335
Dornier Do 335
The Dornier Do 335 Pfeil was a World War II heavy fighter built by the Dornier company. The two-seater trainer version was also called Ameisenbär . The Pfeils performance was much better than other twin-engine designs due to its unique "push-pull" layout and the much lower drag of the in-line...
and the early 1960s-designed French Moynet M 360 Jupiter
Moynet Jupiter
The Moynet 360 Jupiter was a small executive transport built in France in the 1960s. It had an unusual twin push-pull configuration, single fuselage configuration...
experimental private plane had their pusher propeller behind the tail.
Design benefits
While pure pushers decreased in popularity during the First World WarWorld War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
, the push-pull configuration has continued to be used. The advantage it provides is the ability to mount two propellers on the aircraft's centreline, thereby avoiding the increased drag that comes with twin wing-mounted engines. It is also easier to fly if one of the two engines fails, as the thrust provided by the remaining engine stays in the centerline. In contrast, a conventional twin-engine aircraft will yaw in the direction of the failed engine and become uncontrollable below a certain airspeed, known as Vmc.
Piloting
PilotsAviator
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...
in the United States who obtain a multi-engine rating
Pilot certification in the United States
Pilot certification in the United States is required for an individual to act as a pilot of an aircraft. It is regulated by the Federal Aviation Administration , a branch of the Department of Transportation...
in an aircraft with this push-pull, or "centerline thrust," configuration are restricted to flying centerline-thrust aircraft; pilots who obtain a multi-engine rating in conventional twin-engine aircraft do not have a similar limitation with regard to centerline-thrust aircraft.
Military application
Despite its distinct advantages push-pull configurations are rare in military aircraft. This is mainly due to the increased risk to the pilot in the case of a crash-landing or the need to parachute from the plane. In a crash the rear engine threatens to kill the pilot by crushing him between itself and the forward engine; in the case of bailing-out the pilot is in danger of hitting the rear propeller. Examples of past military applications include the late WWII Dornier Do 335Dornier Do 335
The Dornier Do 335 Pfeil was a World War II heavy fighter built by the Dornier company. The two-seater trainer version was also called Ameisenbär . The Pfeils performance was much better than other twin-engine designs due to its unique "push-pull" layout and the much lower drag of the in-line...
heavy fighter, which included a jettisonable tail to facilitate bailing out, and the Cessna O-2, a militarised version of the Skymaster used for observation and forward air control during the Vietnam war.
External links
- Star Kraft SK-700 - 2 x 350hp 1000aircraftphotos.com