Servo tab

Servo tab

Servo tabs

Servo tabs move in the opposite direction of the control surface. The tab has a leverage advantage, being located well aft of the surface hinge line, and thus can use the relative airflow to deflect the control surface in the opposite direction. This has the effect of reducing the control force required by the pilot to move the controls.^[1]^[2]

In the case of some large aircraft the servo tab is the only control that is connected to the pilot's stick or wheel, as in the Bristol Britannia and its Canadian derivatives. The pilot moves the wheel which moves the servo tab and then the servo tab, using its mechanical advantage, moves the elevator or aileron, which is otherwise free-floating. With a servo-tab variant named "geared spring tab", a pilot is able "to maneuver a vehicle weighing as much as 300,000 pounds flying at an airspeed of 300 miles per hour or more".^[3]

Anti-servo tabs

An anti-servo tab on the elevator of an American Aviation AA-1 Yankee.

An anti-servo tab, or anti-balance tab, works in the opposite way to a servo tab. It deploys in the same direction as the control surface, making the movement of the control surface more difficult and requires more force applied to the controls by the pilot. This may seem counter-productive, but it is commonly used on aircraft where the controls are too light or the aircraft requires additional stability in that axis of movement. The anti-servo tab serves mainly to make the controls heavier in feel to the pilot^[4] and also to increase stability.^[5] An anti-servo tab also functions as a trim device to relieve control pressure and maintain the stabilator in the desired position.^[2]^[6]

References

↑ Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 456. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2
1 2 From the Ground Up, 27th Revised Edition, Aviation Publishers, Ottawa, Ontario, Canada, 1996, pg 14.
↑ W.H. Phillips, A Career at NASA Langley Research Center, Chapter 6, The Quest for Reduced Control Forces and Naca Rep. 794 (1944)
↑ Stick force per g
↑ Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 34. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2
↑ "Antiservo Tabs". Pilot's Handbook of Aeronautical Knowledge (FAA). AeroManual.com. Retrieved 2014-07-17.

External links

The Quest for Reduced Control Forces (NASA) — Monographs in Aerospace History: William Hewitt Phillips. A thorough dissertation on the reduction of control forces in high speed and large aircraft in the '40s, with excellent links to NACA reports of the time, holding present day validity

Aircraft components and systems

Airframe structure	Aft pressure bulkhead Cabane strut Canopy Cruciform tail Dope Empennage Fabric covering Fairing Flying wires Former Fuselage Hardpoint Interplane strut Jury strut Leading edge Lift strut Longeron Nacelle Rib Spar Stabilizer Stressed skin Strut T-tail Tailplane Trailing edge Twin tail Vertical stabilizer V-tail Wing root Wing tip Wingbox

Flight controls	Aileron Airbrake Artificial feel Autopilot Canard Centre stick Deceleron Dive brake Electro-hydraulic actuator Elevator Elevon Flaperon Flight control modes Fly-by-wire Gust lock Rudder Servo tab Side-stick Spoiler Spoileron Stabilator Stick pusher Stick shaker Trim tab Wing warping Yaw damper Yoke

Aerodynamic and high-lift devices	Active Aeroelastic Wing Adaptive compliant wing Blown flap Channel wing Dog-tooth Droop Flap Gouge flap Gurney flap Krueger flap Leading edge cuff LEX Slats Slot Stall strips Strake Variable-sweep wing Vortex generator Vortilon Wing fence Winglet

Avionic and flight instrument systems	ACAS Air data computer Airspeed indicator Altimeter Annunciator panel Attitude indicator Compass Course deviation indicator EFIS EICAS Flight data recorder Flight management system Glass cockpit GPS Heading indicator Horizontal situation indicator INS Pitot-static system Radar altimeter TCAS Transponder Turn and slip indicator Vertical Speed Indicator Yaw string

Propulsion controls, devices and fuel systems	Autothrottle Drop tank FADEC Fuel tank Gascolator Inlet cone Intake ramp NACA cowling Self-sealing fuel tank Splitter plate Throttle Thrust lever Thrust reversal Townend ring Wet wing

Landing and arresting gear	Arrestor hook Autobrake Conventional landing gear Drogue parachute Landing gear Landing gear extender Oleo strut Tricycle landing gear Tundra tire

Escape systems	Ejection seat Escape crew capsule

Other systems	Aircraft lavatory Auxiliary power unit Bleed air system Deicing boot Emergency oxygen system Entertainment system Environmental control system Hydraulic system Ice protection system Landing lights Navigation light Passenger service unit Ram air turbine Weeping wing

This article is issued from Wikipedia - version of the Friday, December 25, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.