CIVIL AERONAUTICS ADMINISTRATION
General Inspection Division
District Office 3 - 16
UNIVERSAL MOULDED PRODUCTS CORPORATION
Monocoupe Airplane Division
ASSEMBLY AND MAINTENANCE
(A) Attaching wing to fuselage. If both wing and tail planes are to be
assembled, do tail planes first.
The Monocoupe wing is built in one piece, continuous from wing tip
to wing tip. It is attached to the fuselage at four points on the top
longerons and is braced to it by the wing struts.
To attach wing to fuselage:
(1) Raise fuselage to flying position. Level it by placing a level on upper
longeron over door or window (between front and rear center
section wing attaching fittings).
(2) Raise wing above and slightly to rear of its position on the
fuselage. Tilt wing so leading edge is down and nose it gently into
place in curve of windshield. This should bring the four wing
center section fittings directly above their mating parts on the
fuselage. As these parts fit very closely it will probably be
necessary to use a screwdriver to help the wing fittings to slide
over the fuselage. The wing will not drop into place because of the
close fit, but can be pulled down by inserting a punch or similar
tool through the hole in each wing fitting and its mating hole in the
fuselage, and pulling down. Insert bolts with the heads outside.
(3) Attach wing struts to fitting at bottom of fuselage just forward of
door. Note that wing struts are left and right. Assemble so fitting
for jury strut (about midway of strut length) will be up or toward
(4) Into the outer ends of the wing struts are threaded forked end bolts
be which the length of the strut can be adjusted. A universal link is
placed between this bolt and the wing fitting and this link must be
bolted to the strut (with the head of the bolt uppermost) before
attaching to the wing. Care should be taken to see that the bolts of
this universal link are not drawn up too tightly (so as to destroy the
desirable universal joint action) but are just snug. Vibration is then not
localized which might cause failure of the forked fitting. The right length
for the struts is such that when they are attached the wing is not
distorted. After attaching struts check incidence by placing a straight
edge on the lower of several surface of several ribs between fuselage and
wing tip using a level to see that there is no incidence at any point. Since
the struts must be unbolted from the wing before they can be adjusted,
several trials may be necessary before the right length is achieved.
Whenever the strut length is altered, make sure that the head of the bolt
through the universal link is on top.
(5) One degree of dihedral is built into the wing at the factory and if
the struts are attached so as not to put any strain in the structure,
no further rigging for dihedral is necessary. The dihedral angle
can be checked by stretching a string tightly over each spar from
wing tip to wing tip. Small blocks of exactly the same thickness
should be placed between the string and the wing at the first rib
inboard of the tip. Measure the distance from the string to the
wing at the four corners of the wing pyralin in the center section.
This distance should be 1-7/8” greater than the height of the blocks
on the ribs. If this distance is not the same at all four corners of
the window, either the wing has been rigged with too much
dihedral on one side (if both corners (left) are higher than the right)
or with greater incidence in one wing then the other (if diagonally
opposite corners give different measurements). Any errors should
be corrected by adjusting the length of the wing struts.
(6) When the wing is correctly rigged as above, it is desirable to
“wash out” the right wing tip slightly to compensate for the torque.
This is done by decreasing the length of the right front wing strut.
Usually one of two complete turns of the adjusting bolt are sufficient.
The torque adjustment can also be made by offsetting the rudder to the
right or by a combination of rudder and wing adjustment, the rudder
adjustment being made by means of the two springs attached to the front
of the rudder pedals -- adjusting so that a little right rudder is carried.
NOTE: It is always advisable to correct for wing heaviness by
decreasing the angle of incidence on the opposite wing tip rather
than increasing the angle of heavy wing. (Do this by extending or
lengthening the rear strut on the side to be “washed out”.
(7) Put auxiliary or jury struts in place with adjusting bolt down.
These should be of such a length that they leave the wing struts
(8) Connect aileron push rod in cabin to aileron bell crank mounted
on left side of front spar. When ailerons are in neutral position, control
stick should also be in neutral position and long arm of aileron bell crank
should be vertical. If stick is not in neutral, adjust aileron push rod. If
bell crank is not vertical, adjust aileron control cables, being careful to
get approximately the same tension in the cables to the left of the bell
crank as in those to the right.
(9) Connect gas tanks to gas lines. Install wing to fuselage and strut
fitting fairing cups.
(10) Inspect all work done in assembly of wing for loose nuts, missing
cotter pins, etc.
(B) Assembling tail planes. If both wing and tail planes are to be
assembled it simplifies the tail assembly to do this first.
(1) On the Model 90A Deluxe, the stabilizer and fin are built in one
piece and no adjustment is provided for either. Set on fuselage
with block under rear stabilizer spar and install lower streamline
wires, the block permitting these wires to be started without
bending them excessively.
(2) Remove block and fasten stabilizer to fuselage with two hold-down
bolts on front spar and one bolt on rear spar.
(3) Push fin slightly to the left and install the right upper streamline
wire. Push fin to right and install left wire. Avoid bending wires
(4) Line up stabilizer. If wing is off, this can be done by laying a
straight edge across fuselage at rear wing center section attachment
fittings and sighting over it at rear stabilizer spar. Adjust wires until spar
is in line with straight edge. If wing is on, measure from top of rear
stabilizer spar to bottom longeron at tail post and adjust until this
distance is same for both sides of stabilizer and rear spar is straight as
determined by sighting along it.
(5) Put in front stabilizer struts so front spar is in line with rear spar.
(6) Adjust upper streamline wires so fin is square with stabilizer.
NOTE: Wire should have just enough tension to take up snugly.
(7) Mount elevator on hinges, horn down. See that it turns freely. If it
binds, stabilizer spar is bowed, correct by adjusting wires.
(8) Install elevator horn housing between sternpost and rudder.
(9) Mount rudder on hinges. See that is turns freely. If it binds fin is
not in upright position and should be shifted in the proper direction by
adjusting the wires.
(10) Connect rudder control cables. Adjust length so that rudder does
not strike elevator when at extreme limit of motion in either direction.
(11) Install tail surface streamlines.
(12) Inspect all bolts and test action of stick and rudder pedals.
(13) Inspect turnbuckles for safety wires. NOTE: For convenience in
reaching parts, it is well to raise tail a couple of feet when assembling.
(C) Maintenance. The airplane should be carefully inspected at periodic
intervals with particular attention to these points.
(1) All control system bearings and control surface hinges should be
kept well lubricated, and all excessive “play” eliminated.
Aileron cable pulleys can be reached through the cover plates at
the wing strut attaching fittings.
Aileron bell crank is located on front spar in cabin.
Elevator bell crank bearings are mounted on lower longeron just
back of seat (see drawing FS 22000).
Elevator push rod bearings should have grease applied if elevator
seems to move hard. These are two wood blocks in rear of fuselage.
(See F S 22000).
Rudder and brake pedals have oil holes near top of upright member.
Tail surface hinges have oil holes bored in them.
Rudder cable pulleys located at bottom of fuselage in rear of seat
(see drawing FS 22000).
The Bungee trimming mechanism is reached be removing seat
cushions, and should only be used for trimming in level flight - always
release before taking off or landing - then no loads other than the air
load will be felt on the elevator control. The wheel hub bearings can
be reached by removing outside cover plate.
(2) Brakes can be adjusted when necessary at wheel.
(3) Tires should be inflated 11 to 13 lbs. for 6.50 x 10 tire and 12 1/2
lbs. for 18“ x 8” wheels.
(4) Bolts should always be inserted with head uppermost.
(5) Keep lock nuts on adjusting bolts drawn down snug.
(6) Keep a shoe on tail skid, as if spring is used without a shoe, it
will be damaged and require replacement. If tail wheel is installed,
(7) Take off wing fuselage streamline at least twice a year and inspect
fittings carefully as they are very important. Test bolt attaching wing
struts to fuselage for play, and if loose put in oversize bolt. If wing struts
seem to vibrate, check length of jury struts making sure they do not bow
(8) Check landing gear shock cord twice a year for chafing. The wide
gear should have 9 turns ¾” shock cord on each side. Considerable
tension should be put in the shock cord when wrapping.
(9) Often times the brakes will grab excessively, particularly in wet
weather. The remedy is to taxi the airplane slowly applying the brakes as
gently as is possible with increasing pedal pressures and throttle until
finally you are just dragging the ship against full brakes with full throttle.
Continue this until the glaze on the lining is burned off and the brake
action will be soft and smooth. While the above operation is being done,
the airplane can be turned slowly, applying full brake suddenly to the
outside of the turn -- the object of the whole procedure is to produce
extreme heat and friction at the brake hand.
UNIVERSAL MOULDED PRODUCTS CORPORATION
Monocoupe Airplane Division,
Date: Apr. 15, 1944
SERVICE BULLETIN NO. 15
Monocoupe Models Affected: 90, 90A, 90W, 90AF (Army Designation L-7A),
90J, 110, 110 Special, D-145.
Subject: It has come to our attention that in some cases the drain holes in
the wings and control surfaces are improperly located so that
moisture is trapped, causing glue joint failures and dry rotting
resulting in looseness of the structural components in general.
We therefore consider it imperative that the following instructions
be complied with immediately upon receipt of this bulletin.
1. Make a thorough inspection of the entire wing by removing the
inspection plates and checking the ribs for looseness, broken
glue joints, and dry rotting, checking false ribs for looseness.
If any defect of this nature is discovered, then the sections of
the wing which do not have inspection holes must be opened
and the entire structure inspected.
If any excessive amount of these defects is apparent, then the
wing should be reworked and recovered. If the structure is
found in good condition, special attention should be paid to
instruction No. 3 following, to prolong the airworthiness of the
2. Check the ailerons and flaps (if any) and if small wrinkles are
found in the fabric, a thorough check should be made for
condition of the structure.
Any fault found in the structure should be repaired immediately.
3. Check all drain holes, both on wings and control surfaces, for
proper location to allow maximum drainage and air circulation.
If a drain hole is found to be over any part of the structure due
either to tightening, shrinking, or improper location, then a new
drain hole should be placed where moisture can drain and air will
be able to circulate.
SERVICE BULLETIN NO. 15 - Page 2 Apr. 13, 1944
4. Instructions Nos. 1 and 2 should be complied with at the end
of every six months period following the original check made
upon receipt of this bulletin, and a pertinent entry made in the
aircraft log book to that effect.
Instruction No. 3 should be complied with at the end of every
ninety-day period following the original check made upon receipt
of this bulletin, and a pertinent entry made in the aircraft log book
to that effect.
If you have disposed of your Monocoupe, please send this bulletin on to the new owner.