INSPECTION OF AIRPLANES
Mechanics in charge of airplanes, who are primarily responsible for
their safety while in their care, should constantly think of new
methods for insuring greater safety and reliability. They should
invariably bring any fresh points they think of to the attention
of their Flight Commander, in order that the rest of the Corps may
benefit by them. They should always try to find out the _cause_ of
anything wrong, and inform the officer in charge of the machine of
their opinion. They should bear in mind any particular incidents which
may have happened to their machine while under their charge during
each flight, and be on the lookout for signs of stresses that may have
occurred to the machine in consequence of these incidents. For example,
a steep spiral may cause side strains on the engine bearers; a flight
in bad weather may cause bending stresses on the longitudinal members
of the body, besides stretching the landing and flying wires. No part
of a machine can be safely overlooked, and good mechanics will always
be seeking for the possible cause of accidents and bringing them to the
notice of the officer in charge of the machines.
During all inspections the following matters of detail deserve
particular attention:
Look out for dirt, dust, rust, mud, oil on fabric. Cleanliness is the
very first consideration.
Give the control cables particular attention. These should not be too
tight, otherwise they will rub stiffly in the guides. The hand should
be passed over them to detect kinks and broken strands. They should be
especially well examined where they run over pulley. Don’t forget the
aileron balance wire on the top plane.
See that all wires are well greased and oiled, and that they are all
in the same tension. When examining wires, be sure to have machine
on level ground as otherwise it may get twisted, throwing some wires
into undue tension and slackening others. The best way, if time is
available, is to jack the airplane up into “flying position.” If a
slack wire is found, do not jump to the conclusion that it must be
tensioned. Perhaps its opposite wire is too tight, in which case it
should be slackened.
Carefully examine all wires and their connections near the propeller,
and be sure that they are snaked around with safety wire, so that the
latter may keep them out of the way of the propeller if they come
adrift.
Carefully examine all surfaces, including the controlling surfaces,
to see whether any distortions have occurred. If distortions can be
corrected by adjustment of wires, well and good, but if not, matter
should be reported.
Verify the angles of incidence, the dihedral angle, the stagger,
and the overall measurements as often as possible (at least once a
week) and correct as outlined in notes on assembly and adjustment of
airplanes.
Constantly examine the alignment and fittings of the undercarriage, the
condition of tires, shock absorbers and the skids. Verify the rigging
position of the ailerons and elevators.
Constantly inspect the locking arrangements of the turnbuckles, bolts,
etc.
Learn to become an expert at vetting, which means the ability to judge
the alignment of the airplane and its parts by eye. Whenever you have
the opportunity practice sighting one strut against another to see that
they are parallel. Standing in front of the machine, which in such a
case should be on level ground, sight the center section plane against
the tail plane and see that the latter is in line. Sight the leading
edge against the main spars, the rear spars, and the trailing edges,
taking into consideration the “washin” and “washout.” You will be able
to see the shadow of the spars through the fabric. By practising this
sort of thing you will, after a time, become quite expert, and will be
able to diagnose by eye faults in efficiency, stability and control.
The following order should be observed in the daily and weekly
inspections:
=Daily Inspection.=—All struts and their sockets, longerons, skids,
etc.
All outside wires and their attachments.
All control levers or wheels, control wires and cable and their
attachments.
All splices for any signs of their drawing.
Lift and landing gear cables or wires for any signs of stretching.
All fabrics, whether on wings or other parts of the machine, for
holes, cuts, weak or badly doped places, or signs of being soaked with
gasoline, and to see if properly fastened to wings, etc.
All outside turnbuckles, to see that they have sufficient threads
engaged, and that they are properly locked.
Axles, wheels, shock absorbers, and tires, pumping the latter up to the
correct pressure.
The seats, both for passenger and pilot, seeing that they are fastened
correctly.
Safety belts and their fastenings.
This examination should be carried out systematically in the following
order:
(_a_) Lower wings, landing gear complete, tail planes with all wires
attached to these tail skids and all attachments and rudder.
(_b_) Nacelle or fuselage, bolts of lower plane, all control levers and
wires.
(_c_) Top wings, wing flaps or ailerons and wires.
_Inspection after Each Flight._—The landing gear, tail skid and
attachments and lift and drag wires for tautness.
The wheels, after a rough landing, for bent spokes, uncovering them if
necessary.
After flying is finished for the day, wipe all oil off the planes as
far as possible with a cloth or cotton waste.
_Weekly Inspection._—Check over all dimensions, span, chord, gap,
stagger of wings, angles of incidence or set angle of wings and tail,
dihedral angle, alignment of fuselage, rudder, elevators, and the
general truth of the machine.
Examine the points of crossing of all wires to see that there are no
signs of wear, and that each wire is properly bound with insulating
tape to prevent rubbing.
Examine all places where wires cross the strut to see if the plates
require renewal.
Examine any control wires which are bound together, and see that they
are correct. (Insulating tape should be used for this in preference to
wires which are bound to slip and cause slack.)
Examine the wheels for bent or loose spokes, uncovering if necessary.
Examine all nuts and bolts of cotter-pin applications, lock washers,
etc.
The following directions for inspection are given to the U. S.
Inspectors of Airplanes:
_Inspection of Cables._
Are there any kinks in the cable?
Are loops properly made?
Are thimbles used in eyes?
Are ends wrapped properly (when wrapped splice is used, wrap must be at
least fifteen times the diameter of wire).
No splicing of the cable itself is permitted.
Has acid struck cable during soldering?
Are any of the strands broken?
Are unwrapped ends stream-lined and show the result of skilled
workmanship?
_For Roebling Hard Wire._
Are there any file cuts or flaws to weaken it?
Is loop well made?
Is ferrule put on correctly?
Are there any sharp bends or kinks?
Are wires too loose or tight in machine?
_Fittings._
Is workmanship good?
Is material good?
Are holes drilled correctly to develop proper strength?
Are there any deep file cuts or flaws to weaken it?
Is rivet or fastening wire put in properly?
Are thimbles of large enough diameter?
_Turnbuckles._
Any file cuts, tool marks, or flaws in shank or barrel?
Are there too many threads exposed?
Is turnbuckle of right strength and size to develop full strength of
wire?
Are shanks bent?
Are threads on shank or in barrel well made?
Is barrel cracked?
Is turnbuckle properly wired?
_Inspection of Linen._
All linen used in airplane construction should be of the following
specifications:
Free from all knots or kinks.
Without sizing or filling.
As near white as possible.
Weight, between 3.5 and 4.5 oz. per square yard.
Strength as per Government Specifications.
_Inspection of Wood._
All wood should be inspected before varnish is applied.
Is grain satisfactory?
Are there any sap or worm holes?
Are there any knots that look as if they would weaken the member?
Any brashiness?
Any holes drilled for bolts or screws that would weaken the member?
Any splits or checks?
Are laminations glued properly?
Are there any plugged holes?
Any signs of dry rot?
_Inspection of Metal Fittings._
When fittings are copper plated and japanned the inspection should take
place after the copper plating.
Have fittings been bent in assembling?
Does fitting show any defects that lessen its strength?
Are holes drilled properly. Do fittings fit?
Sheet aluminum should be inspected for defects such as cracks, bad
dents, etc. Where openings occur in sheet aluminum the corners should
be rounded, allowing a good-sized radius.
_Directions for Work._
Before you start work on rigging you are advised as follows:
1. Do not hurry about the work. No rush jobs can be done in airplane
rigging.
2. You are cautioned against leaving tools of any kind in any part of
the airplane.
3. The bolts and their threads must not be burred in any way; for this
reason, the use of pliers or pipe wrenches on bolts is very bad form.
4. Start all turnbuckles from both ends every time they are connected
up.
5. Full threads must be had in every case to develop the full strength
of a bolt and nut, with turnbuckles at least turn on for a distance
equal to three times the thickness of the shank.
6. Lock with safety wires all turnbuckles and pins, and cotter-pin
every nut.
7. Watch for kinking of wires and their rubbing around controls and
wherever they may vibrate against one another.
8. All bolts and pins must have an easy tapping fit only; do not pound
them into position.
Transcriber’s Notes
pg 22 Changed: funished with dual control
to: furnished with dual control
pg 83 Changed: rather than flying off in a straight ine
to: rather than flying off in a straight line
pg 86 Changed: to get out of an immanent pancake
to: to get out of an imminent pancake