Elevator Balancing Procedure; Elevator Control System Friction Measurement - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
1.
If the surface balances, it is within the balance limits and is satisfactory.
2.
If the surface is leading edge heavy, place the master test weight (0.0 to 0.5 lbs.) 6 inches behind
the hinge line. (Refer to Figure 4-16, Master Test Weight Arm "B.") If the surface balances or is trailing edge
heavy, it is satisfactory.
3.
If the surface is still leading edge heavy, remove material from the surface balance weight
until a balanced condition is obtained with master test weight in place.
4.
If the surface is trailing edge heavy, add trim weights (P/N 54395-2) to produce a balanced
condition. Do not use more than three (3) trim weight P/N 54395-2, and one (1) trim weight P/N 54395-3.
4-95. ELEVATOR BALANCING PROCEDURE.
(Refer to Figure 4-17.)
PPS-50022-1
a.
Remove the complete (both halves) elevator assembly from the airplane. (Refer to Paragraph 4-28.)
The complete assembly including trim tab and actuating rod must be assembled and placed on a balancing jig.
(Refer to Paragraphs 4-91 and 4-92.) Check the assembly part number to ascertain the particular specifications
required from Table IV-I are used when balancing the assembly.
b.
Fabricate a test weight in accordance with specifications in Table IV-I.
c.
With the elevators assembled and mounted in the jig, establish a horizontal reference mark which
aligns with the trailing edge of the elevator when held in a level position (chord line level). Ascertain that
the assembly rotates freely with no binding at knife edges.
d.
Hang the fabricated master test weight in the tool hole of the elevator counterbalance rib assembly
part number 43745. Check the master test weight arm location as shown on Figure 4-17 and defined in
Paragraph 4-93. and specified in Table IV-I.
e.
If the elevator is balanced (trailing edge aligns with reference mark) with just the master test
weight, the surface is at the minimum static limit per Table IV-I and is satisfactory.
f.
If the elevator is leading edge heavy, balance weight material must be removed to produce a
balanced condition with the master test weight in place. Remove trim weights part number 43332 first, if
installed then remove material from the main balance weight. Remove material or trim weights evenly from
both sides.
g.
If the elevator is trailing edge heavy with just the specified master test weight installed, then it
must be determined that elevator does not exceed the maximum static limits per Table IV-I.
h.
Add individual 0.1 pound test weights to master test weight until the elevator balances. If the
number of 0.1 pound test weights does not exceed the maximum allowed per Table IV-I, the elevator is
within the static balance limits.
i.
If the number of 0.1 pound test weights added to the master test weight exceeds the maximum
allowable, the elevator balance exceeds the maximum and trim weights must be added to the surface
balance weights, equally to each side, to produce a balanced condition. Ascertain that the number of trim
weights added does not exceed the maximum amount as stated in Table IV-I.
4-96. ELEVATOR CONTROL SYSTEM FRICTION MEASUREMENT. The complete control system
including Autopilot. if installed, must be checked to determine the total friction. The system must be
rigged to its proper travels and cable tensions prior to determining the total friction.
The total friction must not be in excess of six pounds with the bungee spring adjusted to 37 ± 1 pounds.
The following procedure will let you determine the actual frictional value of the system:
a. Attach a spring scale to the inboard trailing edge of the elevator as shown in Figure 4-18.
b.
With the spring scale attached, position the elevator trailing edge down approximately 2 inches
from the neutral position.
c.
Record the force (see Note 2) required to raise the elevator through the neutral position until the
trailing edge is approximately 2 inches above neutral.
d.
Record the restraining force lowering the elevator from the 2 inch up position through the
neutral position to the original 2 inch down position.
e.
Repeat above raising and lowering processes until average forces are obtained.
f.
The "Total Friction" is obtained by subtracting the two forces.
Revised: 3/11/81
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