Conventional landing gear, ortailwheel-type landing gear, is anaircraftundercarriage consisting of two main wheels forward of thecenter of gravity and a small wheel or skid to support the tail.[1][2] The termtaildragger is also used.[2]
The term "conventional" persists for historical reasons, but all modernjet aircraft and most modern propeller aircraft usetricycle gear.
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In early aircraft, a tailskid made of metal or wood was used to support the tail on the ground. In most modern aircraft with conventional landing gear, a small articulated wheel assembly is attached to the rearmost part of theairframe in place of the skid. This wheel may be steered by the pilot through a connection to the rudder pedals, allowing the rudder and tailwheel to move together.[2][3]
Before aircraft commonly used tailwheels, many aircraft (like a number of First World WarSopwith aircraft, such as theCamel fighter) were equipped with steerable tailskids, which operate similarly to a tailwheel. When the pilot pressed the right rudder pedal—or the right footrest of a "rudder bar" in World War I—the skid pivoted to the right, creating more drag on that side of the plane and causing it to turn to the right. While less effective than a steerable wheel, it gave the pilot some control of the direction the craft was moving while taxiing or beginning the takeoff run, before there was enough airflow over the rudder for it to become effective.
Another form of control, which is less common now than it once was, is to steer using "differential braking", in which the tailwheel is a simple, freelycastering mechanism, and the aircraft is steered by applying brakes to one of the mainwheels in order to turn in that direction. This is also used on some tricycle gear aircraft, with the nosewheel being the freely castering wheel instead. Like the steerable tailwheel/skid, it is usually integrated with the rudder pedals on the craft to allow an easy transition between wheeled and aerodynamic control.[citation needed]
The tailwheel configuration offers several advantages over thetricycle landing gear arrangement, which make tailwheel aircraft less expensive to manufacture and maintain.[2]
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The conventional landing gear arrangement has disadvantages compared to nosewheel aircraft.[2]
Jet aircraft generally cannot use conventional landing gear, as this orients the engines at a high angle, causing theirjet blast to bounce off the ground and back into the air, preventing theelevators from functioning properly. This problem occurred with the third, or "V3" prototype of the GermanMesserschmitt Me 262 jet fighter.[5] After the first four prototype Me 262 V-series airframes were built with retracting tailwheel gear, the fifth prototype was fitted with fixed tricycle landing gear for trials, with the sixth prototype onwards getting fully retracting tricycle gear. A number of other experimental and prototype jet aircraft had conventional landing gear, including the first successful jet, theHeinkel He 178, theBall-Bartoe Jetwing research aircraft, and a singleVickers VC.1 Viking, which was modified withRolls-Royce Nene engines to become the world's first jet airliner.
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Rare examples of jet-powered tailwheel aircraft that went into production and saw service include the BritishSupermarine Attacker naval fighter and the SovietYakovlev Yak-15. Both first flew in 1946 and owed their configurations to being developments of earlier propeller powered aircraft. The Attacker's tailwheel configuration was a result of it using theSupermarine Spiteful's wing, avoiding expensive design modification or retooling. The engine exhaust was behind the elevator and tailwheel, reducing problems. The Yak-15 was based on theYakovlev Yak-3 propeller fighter. Its engine was mounted under the forward fuselage. Despite its unusual configuration, the Yak-15 was easy to fly. Although a fighter, it was mainly used as atrainer aircraft to prepare Soviet pilots for flying more advanced jet fighters.
A variation of the taildragger layout is themonowheel landing gear.
To minimize drag, many moderngliders have a single wheel, retractable or fixed, centered under the fuselage, which is referred to asmonowheel gear ormonowheel landing gear. Monowheel gear is also used on some powered aircraft, where drag reduction is a priority, such as theEuropa XS. Monowheel power aircraft use retractable wingtip legs (with small castor wheels attached) to prevent the wingtips from striking the ground. A monowheel aircraft may have a tailwheel (like the Europa) or a nosewheel (like theSchleicher ASK 23 glider).
Taildragger aircraft require more training time for student pilots to master. This was a large factor in the 1950s switch by most manufacturers to nosewheel-equipped trainers, and for many years nosewheel aircraft have been more popular than taildraggers. As a result, mostPrivate Pilot Licence (PPL) pilots now learn to fly in tricycle gear aircraft (e.g.Cessna 172 orPiper Cherokee) and only later transition to taildraggers.[2]
Landing a conventional geared aircraft can be accomplished in two ways.[6]
Normal landings are done by touching all three wheels down at the same time in athree-point landing. This method does allow the shortest landing distance but can be difficult to carry out in crosswinds,[6] as rudder control may be reduced severely before the tailwheel can become effective.[citation needed]
The alternative is thewheel landing. This requires the pilot to land the aircraft on the mainwheels while maintaining the tailwheel in the air withelevator to keep theangle of attack low. Once the aircraft has slowed to a speed that can ensure control will not be lost, but above the speed at whichrudder effectiveness is lost, then the tailwheel is lowered to the ground.[6]
Examples of tailwheel aircraft include:
Several aftermarket modification companies offer kits to convert many popularnose-wheel equipped aircraft to conventional landing gear. Aircraft for which kits are available include: