thumb|right|[[Grumman F-14 Tomcat jet fighter during a takeoff, with stabilators deflected upwards]]

A stabilator is a fully movable aircraft horizontal stabilizer. It combines the functions of both the fixed stabilizer and the movable elevator, providing longitudinal stability, pitch control, and appropriate stick force. Apart from reduced drag, particularly at high Mach numbers, it is a useful device for changing the aircraft balance within wide limits, and for reducing stick forces.

The term "stabilator" is a portmanteau of stabilizer and elevator. It is also known as an all-moving tailplane (British English), all-movable tail(plane), all-moving stabilizer, all-flying tail (American English), all-flying horizontal tail, full-flying stabilizer, and slab tailplane. thus providing an aerodynamic force resisting the pilot's input. General aviation aircraft with stabilators include the Piper Cherokee The contemporary American supersonic project, the Bell X-1, used separately-adjustable horizontal stabilizer and elevators allowing movement as a single surface or elevator deflection at a fixed tailplane setting.

Entering service in 1951, the Boeing B-47 Stratojet was the world's first purposely built jet bomber to include one piece stabilator design. A stabilator was considered for the Boeing B-52 Stratofortress but rejected due to the unreliability of hydraulics at the time. can also be mounted in front of the main wing in a canard configuration (Curtiss-Wright XP-55 Ascender).

Stabilators on military aircraft have the same problem of too light control forces (inducing overcontrol) as general aviation aircraft. Unlike light aircraft, supersonic aircraft are not fitted with anti-servo tabs, which would add unacceptable drag. In older jet fighter aircraft, a resisting force was generated within the control system, either by springs or a resisting hydraulic force, rather than by an external anti-servo tab. For example, the North American F-100 Super Sabre, used gearing and a variable stiffness spring attached to the control stick to provide an acceptable resistance to pilot input. In modern fighters, control inputs are processed by computers ("fly by wire"), and there is no direct connection between the pilot's stick and the stabilator.

Airliners

thumb|Adjustable stabilizer on an [[Embraer E170, with markings showing the degree of nose-up and nose-down trim available]]

Most modern airliners use an adjustable horizontal stabilizer and a separate elevator control, rather than a stabilator. The movable horizontal stabilizer is adjusted to keep the pitch axis in trim during flight as the speed changes, or as fuel is burned and the center of gravity moves. These adjustments are commanded by the autopilot when it is engaged, or by the human pilot if the plane is being flown manually. Adjustable stabilizers are not the same as stabilators: a stabilator is controlled by the pilot's control yoke or stick, whereas an adjustable stabilizer is controlled by the trim system.

In the Boeing 737, the adjustable stabilizer trim system is powered by an electrically operated jackscrew.

One example of an airliner with a true stabilator used for flight control is the Lockheed L-1011.

See also

  • Canard
  • Index of aviation articles

References

  • Stabilators (NASA) – Includes Java applet

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