Aircraft Systems, Structures, and Aerodynamics Review

Comprehensive vocabulary flashcards covering flight control systems, hydraulics, landing gear, airframe structures, fuel systems, aerodynamics, and weight and balance principles.

Torque tube

A control system component installed where an angular or twisting motion is required to be transmitted.

Bell crank

A device used extensively in push/pull rod systems to change the direction of travel and to increase or decrease mechanical advantage (leverage).

Quadrant

A device used to allow tensioned control cables to provide fore and aft linear movement about a common rotational axis.

Gust lock

A device that mechanically locks aircraft flight control surfaces to prevent damage while parked.

Nicopress process

A method of cable termination utilizing compressed copper sleeves.

Fairlead

A cable guide that prevents cable chafing and is permitted to deflect a control cable by a maximum angle of $3^\circ$.

Teleflex

A mechanical remote control system capable of transmitting both push and pull movements, distinguishing it from the Bowden system.

Cable tension regulator

A unit used in flight control cable systems to provide automatic tension adjustment to compensate for temperature variations.

Bi-planar block

A mechanical coupling component used to rotate the operating plane of a control chain through $90^\circ$.

Dynamic balance (control surfaces)

The condition of maintaining control surface balance during flight motion, practically achieved by placing weights forward of the hinge line along the surface span.

Prevailing torque

The driving torque required to overcome friction in a threaded fastening application that produces no clamp load or bolt stretch.

Aileron droop

A rigging condition found on slower STOL aircraft where maximum lift is required at slower speeds and the resulting extra drag is acceptable.

Differential control

An aileron control system design in which each aileron has a greater up travel from the streamlined position than down travel.

Crossfeed valve

A fuel valve that allows multiengine aircraft to feed any engine from any fuel tank, enabling the crew to maintain a balanced fuel load.

Fuel boost pump

A submerged pump used to provide a positive flow of fuel to the engine and prevent vapor lock and bubbles at altitude.

Integral fuel tank

A fuel tank design where the aircraft structure itself forms the tank, using sealed rivet joints (wet wing) to reduce weight.

Punkah Louvre

An adjustable cabin air vent that allows control over airflow direction and volume.

Open centre selector valve

A hydraulic selector valve designed such that fluid freely circulates through the valve back to the reservoir when placed in the OFF position.

Skydrol (MIL-H-8446)

A light purple, fire-resistant, phosphate ester-base synthetic hydraulic fluid used with butyl rubber seals.

MIL-H-5606

A red-colored, flammable petroleum-base mineral hydraulic fluid used with synthetic and neoprene rubber packings.

Shuttle valve

A hydraulic valve that automatically directs fluid from either the normal system or an emergency power source to an actuating cylinder.

Flap overload valve

A valve that prevents aircraft wing flaps from being lowered at airspeeds that would impose excessive structural loads.

Sequence valve

A hydraulic valve that causes one operational event to follow another in a definite, predetermined order.

Hydraulic fuse

A safety device that allows normal fluid flow but automatically shuts off flow if the flow rate exceeds an established threshold.

Standpipe

A vertical inlet pipe fitted inside a hydraulic reservoir to supply the main engine pump while reserving a lower volume of fluid for emergency pump operation.

Debooster cylinder

A component installed between the brake control valve and actuating cylinder to reduce hydraulic pressure and increase fluid volume delivered to the brakes.

Chines

Specially molded ridges on aircraft nose wheel tires designed to deflect water spray away from the aircraft fuselage and engines.

Doubler

An additional structural strengthening plate installed over localized areas subjected to high loads or surrounding cutouts and penetrations.

Safe life

The operational life limit of an aircraft structure, expressed in flight hours or flight cycles, after which it must be permanently removed from service or replaced.

Stress riser

A structural location where a sudden change in cross-sectional area concentrates mechanical stress and increases the likelihood of failure.

Semi-monocoque

A structural airframe configuration where the skin carries substantial load while being reinforced and shaped by internal formers, longerons, and stringers.

Fail-safe design

A multi-load path structural design philosophy that permits an airframe to retain required residual strength following the partial or complete failure of a principal member.

Decalage

The difference in the angle of incidence between the upper wing and the lower wing of a biplane.

Canard

A horizontal aerodynamic surface mounted on the fuselage forward of the main wing to provide longitudinal stability and control.

Stall strip

A device mounted on the leading edge of a wing to initiate early airflow separation and stall at a specific location during high angle-of-attack flight.

False spar

A structural wing member that does not span the entire length of the wing, commonly used as an attachment and hinge point for control surfaces.

Boundary Layer

The thin layer of fluid in the immediate vicinity of a bounding surface where viscous forces are significant.

Stagnation point

The precise point on the leading edge of an airfoil where the oncoming airstream flow velocity is reduced to zero.

Angle of Attack (AoA)

The acute angle formed between the relative wind and the chord line of an airfoil.

Angle of incidence

The fixed angle formed between the chord line of the wing at its fuselage attachment and the longitudinal reference axis of the aircraft.

Mean Aerodynamic Chord (MAC)

The chord of an imaginary rectangular wing that possesses identical aerodynamic characteristics to the actual wing.

Wash-out

A wing design feature that deliberately twists the wing tip downward to decrease lift outboard and ensure root stall before tip stall.

Load factor

The ratio of the total aerodynamic lift acting on an aircraft to the gross weight of the aircraft.

Anti-servo tab

A tab installed on an all-moving stabilator that deflects in the same direction as the surface to decrease control sensitivity and increase stick feel.

Useful load

The remaining allowable weight calculated by subtracting the basic empty weight from the maximum allowable gross weight of the aircraft.

Moment arm

The horizontal distance measured in inches from the reference datum line to the center of gravity (CG) of an item.

Reference datum

An imaginary vertical reference plane from which all horizontal arm and station measurements are taken for weight and balance calculations.

METO

An acronym standing for Maximum Except Take-Off horsepower.

Dutch Roll

An oscillatory aerodynamic instability common to swept-wing aircraft characterized by combined rolling and yawing motions.