Assembly & Rigging – Fixed- and Rotary-Wing Fundamentals

83 question-and-answer flashcards reviewing key aerodynamic principles, control systems, stability concepts, rigging procedures, and helicopter fundamentals discussed in the Assembly & Rigging lecture notes. Use them to quiz yourself for the upcoming exam.

What are the five main objectives of aircraft rigging covered in this lecture?

Rig fixed-wing aircraft, assemble aircraft components, check alignment of structures, balance flight-control surfaces, and rig rotary-wing aircraft.

Name the six principal external parts of a conventional fixed-wing airplane.

Wing, fuselage, horizontal stabilizer/elevator, vertical stabilizer/rudder, ailerons, propeller (plus flaps as secondary controls).

What are the two basic types of lift?

Aerostatic lift (lighter-than-air) and aerodynamic lift (produced by airflow over a surface).

Give the ICAO standard-day sea-level values for pressure and temperature.

29.92 in. Hg (14.69 psi, 1013.2 mb) and 59 °F (15 °C).

List the four primary forces acting on an airplane in flight.

Lift, weight, thrust, and drag.

State Bernoulli’s principle as it applies to subsonic airflow.

As the speed of a fluid increases through a constriction, its static pressure decreases.

How does camber on an airfoil create lift according to Bernoulli’s principle?

The curved upper surface accelerates airflow, lowering static pressure above the wing and producing an upward pressure differential (lift).

Define an airfoil.

Any surface specifically designed to obtain lift when moving relative to the air; e.g., wing, propeller blade, stabilizer.

What is the fineness ratio of an airfoil?

The ratio of the chord length to the maximum thickness of the airfoil.

How does fineness ratio affect drag?

High fineness ratio increases skin-friction drag; low fineness ratio increases pressure (form) drag due to turbulence.

What aerodynamic parameter is used to measure wing efficiency?

The lift-to-drag ratio (L/D).

How does increasing wing camber affect lift?

Increased camber increases lift at a given angle of attack.

Define aspect ratio.

The ratio of wingspan to average chord; a higher aspect ratio generally yields greater lift and lower induced drag.

What is the chord line of a wing?

A straight line connecting the leading and trailing edges of an airfoil section.

Define angle of attack (AOA).

The acute angle between the chord line and the relative wind.

What is the angle of incidence, and how does it behave in flight?

The fixed angle between the wing chord line and the aircraft longitudinal axis; it does not change during flight.

Describe the aerodynamic stall on a wing.

A stall occurs when the airflow separates from the upper surface because the critical angle of attack is exceeded, causing lift to decrease sharply.

How do flaps affect the wing’s angle of attack and lift?

Extending flaps effectively increases camber and the wing’s AOA for a given aircraft attitude, producing more lift and drag.

Explain dihedral and its measurement method.

Dihedral is the upward angle of the wings relative to the lateral axis; it is measured with a dihedral board and bubble level placed on the front spar.

What are buttock lines (buttlines) on an aircraft drawing?

Longitudinal vertical reference planes measured left or right from the aircraft centerline, used for locating structure points.

Name the two broad categories of drag.

Induced drag and parasite drag.

What flight condition causes induced drag to increase?

Increased angle of attack (especially at low airspeeds/high lift conditions).

List the three sub-types of parasite drag.

Form (pressure) drag, profile (skin-friction) drag, and interference drag.

How does parasite drag vary with airspeed?

Parasite drag increases with the square of airspeed.

Which axis does an airplane roll about, and which control surface provides roll?

Roll occurs about the longitudinal axis and is controlled by the ailerons.

What is adverse yaw and how is it minimized?

Tendency to yaw opposite the roll direction due to differential drag; minimized by differential ailerons or rudder coordination.

Describe differential aileron movement.

The upward-moving aileron deflects more than the downward-moving one, adding drag to the rising wing to counteract adverse yaw.

Which axis is associated with pitch, and which control surface controls it?

Pitch occurs about the lateral axis and is controlled by the elevator (or stabilator).

Which axis concerns yaw, and what surface controls it?

Yaw occurs about the vertical axis and is controlled by the rudder.

Define static stability.

The initial tendency of an aircraft to return to equilibrium after a disturbance without pilot input.

Define dynamic stability.

The time history of a returning motion—how quickly and smoothly the aircraft returns to equilibrium after being disturbed.

List the three possible states of static (or dynamic) stability.

Positive, neutral, or negative stability.

Where is the center of lift (pressure) normally located relative to the center of gravity, and why?

Slightly aft of the center of gravity to provide inherent longitudinal (nose-down) stability.

Which control surfaces and design features contribute to longitudinal stability?

Horizontal stabilizer/elevator positioning, CG location, and wing/in-stabilizer incidences.

What structural feature provides lateral stability without pilot input?

Wing dihedral.

For directional stability, which component is most critical?

Vertical stabilizer (fin) and rudder alignment.

Why is proper cable tension critical in control systems?

Incorrect tension can cause sluggish controls, surface flutter, or binding, compromising safety and responsiveness.

Describe the construction of a 7×19 aircraft control cable.

Seven strands, each containing nineteen wires, yielding an extra-flexible cable.

What tool measures cable tension, and how is it used?

A tensiometer; select the correct riser for cable size, read the scale, and use the conversion chart for pounds of tension.

How are Nicopress thimble-eye splices rated for strength?

Properly made Nicopress splices develop 100 % of the cable’s rated strength.

Name three common swaged cable terminal types.

Fork-end, eye-end, and threaded-end terminals.

Explain the purpose of a fairlead.

A guide that supports and aligns a control cable where it passes through structure, preventing chafing and maintaining routing.

How is a turnbuckle safetied?

Using safety wire or locking clips so neither threaded end can rotate relative to the barrel (minimum four turns of wire).

What is the function of a balance tab?

Deflects opposite the control surface to aerodynamically assist the pilot in moving the surface; may also serve as a trim tab.

Describe an antiservo tab and where it is commonly found.

Moves in the same direction as a stabilator to add control feel and prevent over-control; used on stabilators and some flaperons.

Why must control surfaces sometimes be mass-balanced?

To move their center of gravity forward of the hinge line, preventing flutter at high speeds.

What instrument measures control surface travel?

A control-surface protractor or universal propeller protractor positioned against the hinge line.

List the basic steps for jacking an aircraft.

Consult MM, clear area, inspect jacks, place at correct jack points, raise slowly and evenly, secure gear extension, lower evenly, remove jacks, detach tail weight if used.

Why must control surfaces be rigged to manufacturer specifications before balancing?

Rigging affects hinge moments; incorrect rigging causes inaccurate balance and potential flutter.

What is a push-pull rod, and how is its length adjusted?

A tubular control linkage with threaded rod-ends; length is set by turning rod ends and securing with check-nuts.

Why is it important to inspect pulley wear patterns?

Abnormal wear indicates misalignment, incorrect cable size, or seized bearings that could lead to control failure.

What is interference drag and give one example.

Drag caused by junction of two surfaces where airflow patterns meet; e.g., wing to fuselage fillet area.

When lift increases on an airfoil, what happens to drag?

Drag also increases.

What is the purpose of vortex generators on high-speed wings?

Create controlled vortices to energize boundary layer, delaying shock-induced separation and reducing drag.

How does adding dihedral at wing tips influence wing-tip vortices?

Moves vortex influence away from primary lifting surfaces, reducing induced drag and improving efficiency.

What maintenance document dictates specific rigging values for a given aircraft?

The aircraft maintenance manual (MM) or Type Certificate Data Sheet (TCDS).

Explain the procedure for holding a control yoke centered during rigging.

Insert a manufacturer-provided rigging pin through aligned holes in the yoke and column to lock it.

What is a jig used for when balancing a control surface?

Supports the surface at hinge line reference points so weights can be moved/added until proper balance is achieved.

Why are eccentric bushings used on some rear wing spars?

Allow fine adjustment of wing angle of incidence during rigging.

Define buttline 0 (BL 0).

The vertical plane coinciding with the aircraft longitudinal centerline; reference for lateral measurements.

Why should aircraft jacks be inspected before use?

To ensure structural integrity, correct hydraulic fluid level, and proper operation preventing accidents.

What is the main hazard of lowering jacks too quickly?

The aircraft may fall off remaining jacks, causing damage to the aircraft and potential injury to personnel.

How is aircraft symmetry checked?

Cross-measure known reference points with a steel tape; distances should be equal left and right of centerline.

In a canard configuration, why is the canard given a greater angle of incidence than the main wing?

So the canard stalls first, lowering the nose to recover airspeed and preventing main-wing stall.

What effect does a high aspect ratio have on lift and induced drag?

Increases lift and reduces induced drag for a given wing area.

Which drag component is directly caused by friction of air over skin surfaces?

Profile (skin-friction) drag.

What is the primary benefit of using Fowler flaps?

They increase wing area and camber, giving a large lift increase with minimal additional drag at extension.

How are cable sizes specified in aviation?

By diameter (fraction of an inch) and construction (e.g., 7×19, 7×7) indicating strands and wires per strand.

What does a balance panel on an aileron do?

Uses low-pressure area over the wing to provide aerodynamic assistance holding the aileron deflected.

Describe control cable inspection technique.

Slack cable slightly, run cloth or glove along length feeling for broken wires, corrosion, or kinks; inspect pulleys, fairleads, and terminals.