Tricycle gear is a type ofaircraftundercarriage (i.e.landing gear) that is arranged in the fashion of atricycle, with a single one/two-wheeled front undercarriage (i.e. thenose gear) under thecockpit and two multi-wheeled main gears slightly aft of thecenter of gravity, usually just behind thewings. This is in contrast to theconventional landing gear (a.k.a. "taildragger") that is arranged with two front gears and one tail gear, more commonly seen in early aircraft but rare nowadays except amongpropeller-poweredlight aircraft and someamphibious aircraft.
Tricycle gears are the most ubiquitousundercarriage arrangements for modern aircraft due to the convenience oftakeoff,landing andtaxiing, especially among the heavierjet aircraft where theengines and wings (and thus the aircraft'scenter of mass) tend to be more rearwards than conventional gear aircraft and a tail-downflare is typically performed when landing.[1][2]
Several early aircraft had primitive tricycle gear, notably very earlyAntoinette planes and theCurtiss Pushers of the pre-World War IPioneer Era of aviation.Waldo Waterman's 1929taillessWhatsit was one of the first to have a steerable nose wheel.[3]
In 1956,Cessna introduced sprung-steel tricycle landing gear on theCessna 172. Their marketing department described this as "Land-O-Matic" to imply that these aircraft were much easier to land than tailwheel aircraft.[4]
Tricycle gear is essentially the reverse ofconventional landing gear ortaildragger. On the ground, tricycle aircraft have a visibility advantage for the pilot as the nose of the aircraft is level, whereas the high nose of the taildragger can block the view ahead. Tricycle gear aircraft are much less liable to 'nose over' as can happen if a taildragger hits a bump or has the brakes heavily applied. In a nose-over, the aircraft's tail rises and thepropeller strikes the ground, causing damage. The tricycle layout reduces the possibility of aground loop, because the main gear lies behind the center of mass. However, tricycle aircraft can be susceptible towheel-barrowing. The nosewheel equipped aircraft also is easier to handle on the ground in high winds due to its wing negativeangle of attack. Student pilots are able to safely master nosewheel equipped aircraft more quickly.[2]
Tricycle gear aircraft are easier toland because theattitude required to land on the main gear is the same as that required in theflare, and they are less vulnerable tocrosswinds. As a result, the majority of modern aircraft are fitted with tricycle gear. Almost all jet-powered aircraft have been fitted with tricycle landing gear to prevent the blast of hot, high-speed gases from causing damage to the ground surface, in particularrunways andtaxiways. The few exceptions have included theYakovlev Yak-15, theSupermarine Attacker, and prototypes such as theHeinkel He 178 thatpioneered jet flight, the first four prototypes (V1 through V4) of theMesserschmitt Me 262, and theNene powered version of theVickers VC.1 Viking. Outside of the United States – where the tricycle undercarriage had solidly begun to take root with its aircraft firms before that nation's World War II involvementat the end of 1941 – theHeinkel firm in World War II Germany began building airframe designs meant to use tricycle undercarriage systems from their beginnings, as early as late 1939 with theHeinkel He 280 pioneering jet fighter demonstrator series, and the unexpectedly successfulHeinkel He 219 twin-engined night fighter of 1942 origin.[5]
The taildragger configuration has its own advantages, and is arguably more suited to rougher landing strips. The tailwheel makes the plane sit naturally in a nose-up attitude when on the ground, which is useful for operations on unpaved gravel surfaces where debris could damage the propeller. The tailwheel also transmits loads to the airframe in a way much less likely to cause airframe damage when operating on rough fields. The small tailwheel is much lighter and much less vulnerable than a nosewheel. Also, a fixed-gear taildragger exhibits lessinterference drag andform drag in flight than a fixed-gear tricycle aircraft whose nosewheel may sit directly in the propeller's slipstream. Tailwheels are smaller and cheaper to buy and to maintain. Most tailwheel aircraft are lower in overall height and thus may fit in lowerhangars. Tailwheel aircraft are also more suitable for fitting withskis in wintertime.[2]
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