General/Airframe Problem Oral Questions Flashcards
What is a balance trim tab?
It is an auxiliary control designed to create aerodynamic forces to assist in moving a control surface. When the primary control surface is moved in any direction, the tab automatically moves in the opposite direction, helping pilot move the control surface
What is a servo trim tab?
It is an auxiliary control, positioned by the movement of a cockpit control and designed to create aerodynamic forces to assist in moving a control surface.
What is a spring tab?
It is an auxiliary control designed to aid the movement of a primary control at high speeds when control forces become too high
What are the two reasons for installing a lightening hole in a sheet metal wing rib?
Lightening holes reduce the weight and increase stiffness
Describe the markings found on the heads of A, B, D, AD, and DD rivets
A rivets are plain, B rivets have a cross, D rivets have a raised dot, AD rivets have a dimple, and DD rivets have a double dash
How can a mechanic determine whether the countersink for a flush rivet should be dimpled or drilled?
By the thickness of the top sheet- thin sheets are dimpled while thick sheets may be countersunk
Name several methods for forming sheet metal.
Bending or folding ,
stretching,
shrinking,
bumping, and
crimping
If a 2024 rivet must be replaced with a 2117 rivet, how do you determine the size to be used?
For 5/32” or smaller diameter, use the next larger size, as long as edge distance and spacing meet minimums
What are the dimensions of a properly formed rivet head?
The head should be 1.5 times the shank diameter in width and 1/2 the shank diameter in height
What minimum edge distance and spacing should be used for a single row of protruding head rivets?
At least two rivet diameters from the edge and not less than three rivet diameters apart.
Describe the process for determining the total length of a solid rivet for a particular installation.
1.5 times the rivet diameter plus the grip length
What two calculations must be made when bending sheet metal?
Setback and bend allowance
Setback (SB)—the distance the jaws of a brake must be
setback from the mold line to form a bend. In a 90° bend,
SB = R + T (radius of the bend plus thickness of the metal). The K-factor must be used for all bends that are smaller or larger than 90°. SB = K(R+T)
Bend allowance (BA)—refers to the curved section of
metal within the bend (the portion of metal that is curved in
bending).
What factors must be considered to determine setback?
Bend radius and material thickness
The distance the jaws of a brake must be set back
from the mold line to form a bend. Setback for a 90° bend
is equal to the inside radius of the bend plus the thickness of the metal being bent. For a bend other than 90°, a K-factor must be used. See also K-factor.
SB=(R+T)K
Name several facings and core materials used in bonded honeycomb structures intended for special applications
Stainless steel, titanium, magnesium, plywood, glass, nylon, cotton cloth
What are the two primary uses for plywood in aircraft construction?
Gusset (reinforcing) plates, and aircraft skin
Give three examples of plywood skin repairs
Splayed patches,
surface patches,
plug patches,
scarfed patches
Is compression wood acceptable for structural repairs?
no
What type of patch should be used to repair small holes in thin plywood skin if the skin is less than 1/10th inch thick?
A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thicknesses of the skin
Describe the construction of a bonded honeycomb structure
It is a laminated structure that has a solid facing bonded to either side of a core made of open six sided cells.
A drill bit used for drilling composites should have an included angle of how many degrees?
135
What are the most common causes for delamination of a composite structure?
Sonic vibration,
expansion of internal moisture,
liquid leakage,
and a manufacturing error
What type of defect in or damage to a bonded honeycomb structure can be repaired using the potted repair method?
Filling a hole
What minimum curing temperature should be observed when joining wood with various adhesives?
70 degrees F or as specified by the manufacturer
Why must the beveled cut be accurate on both pieces of wood with a scarf joint?
They must match exactly for a tight glue joint
Where are splices to a wood spar prohibited?
Under an attachment fitting for the wing root,
landing gear,
engine mount, lift,
or inter plane strut
What are the three types of glues used in modern aircraft construction and repair?
Resorcinol glue
phenol-formaldehyde glue
epoxy resin glue
What is the max number of splices for a single spar?
2
Describe the characteristics of a scarf joint
The pieces are tapered or beveled on a slope of 1 to 10 or 1 to 12
