NOTE: Avoid adding the Lubrizol directly. We recommend thoroughly pre-mixing the Lubrizol with 10 parts shock strut fluid before pouring the additive into the strut.
b) Replace air valve. 5) Connect an overflow hose to air valve on top of shock strut and check that air valve is fully opened. Place other end of hose to drain into container. 6) Pump fluid into shock strut from servicing cart until fluid overflows into container.
(5)
Slowly lower axle jack until shock strut is extended. Remove axle jack.
CAUTION: TO PREVENT THE OVERFLOW FLUID FROM BEING DRAWN BACK INTO SHOCK STRUT, DO NOT ALLOW HOSE TO BECOME SUBMERGED BELOW SURFACE OF FLUID IN CONTAINER WHEN SHOCK STRUT IS EXTENDING.
(6)
Lower airplane to fully compress shock strut.
(7)
Remove all jacks.
(8)
Disconnect service cart and remove hose from top of shock strut.
(9)
Inflate shock strut with dry air or nitrogen to conform to the servicing chart (Fig. 202).
(10)
Close air valve at top of shock strut.
(11)
Install dust cap and lockwire air valve.
(12)
Return airplane to service and, after several landings do the following steps:
(a)
Check shock strut pressure and X dimension. If necessary, re-inflate shock strut.
(b)
Re-service the shock strut with air or nitrogen (Fig. 202).
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12-15-31 Page 206 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 01/99
NOTE: The wide tolerance "Operation Band" does not eliminate the requirement for two separate charging operations to the "Servicing Band".
4. Check Fluid Level by Pressure/Extension Method
NOTE: Shock strut fluid level may be checked by measuring shock strut pressure and extension at two different airplane weights and comparing measurements with shock strut servicing band (curve).
A. With airplane unloaded (at typical landing weight) measure strut pressure and extension and compare with strut servicing chart band. Inflate or deflate strut as required to shift point into chart band.
B. With airplane loaded and fueled (typical dispatch weight) measure strut pressure and extension. For best accuracy airplane weight should differ from that in previous step by a minimum of 30,000 pounds and ambient temperatures at time of measurements are taken should be within 20oF.
C. Compare point measured in previous step with servicing chart.
(1)
If point falls within servicing band, fluid level is in proper operating range.
(2)
If point falls to left of band, fluid level is low. Add fluid per par. 2 or 3. If strut requires one quart or more fluid to fill, find leakage source and repair.
(3)
If point falls to right of band, fluid level is high. Remove fluid per par. 2 or 3. Excess (high) fluid level is caused by a prior incorrect servicing procedure.
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12-15-31 Page 207
NOSE LANDING GEAR SHOCK STRUT – SERVICING
1. General
A. This procedure is used to add fluid to a shock strut that has either been in normal operation or requires initial filling after disassembly and repair.
B. There is no simple method for checking the fluid level within a depressurized strut after any pressurization such as raising the airplane by pressurizing the strut with air or nitrogen. Gas entering into solution with the fluid changes the effective volume of the fluid. The complete servicing procedure must be performed to properly fill the shock strut.
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