S 866-548
(5)
Make sure the four FLT CONTROL HYD POWER - TAIL switches, on the P5 Pilots' Overhead Panel, are in the NORM position.
S 866-549
(6)
Make sure the selector handle for the landing gear, on the P2 First Officer's Panel, is in the OFF position.
S 216-550
(7)
Make sure there is sufficient fuel in the applicable tank for the operation of the hydraulic heat exchanger as follows:
NOTE: The values given below are found on the specified fuel
____ density of 6.7 pounds for a gallon (3.1 Kg for a liter).
(a)
For system No. 1, there must be 2000 pounds (900 KG) of fuel in the No. 1 main tank.
(b)
For system No. 2, there must be 5400 pounds (2450 KG) of fuel in the No. 2 main tank.
(c)
For system No. 4, there must be 2000 pounds (900 KG) of fuel in the No. 4 main tank.
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747-400 MAINTENANCE MANUAL
(d) For system No. 3, there must be 5400 pounds (2450 KG) of fuel in the No. 3 main tank.
S 866-551
(8)
Put the STAB TRIM 2 and 3 switches to the NORMAL Postion.
S 866-552
(9)
Put the LOWER and UPPER YAW DAMPER switches to the OFF position.
S 866-553
(10)
Make sure the HYD PUMPS DEMAND switches for all four hydraulic systems are in the OFF position.
S 866-554
(11)
Make sure the HYD PUMPS ENGINE switch, for the system on which you will do the check, is in the ON position.
E.
Hydraulic Systems No. 1 thru 4 Leakage Check
S 866-555
(1) Motor the engine at 12.2% N2 rpm to supply a flow from the
engine-driven pump (EDP) of 4.5 gpm (AMM 71-00-00/201).
NOTE: Do not operate the starter more than its limits
____
(AMM 71-00-00/201).
You can operate the ADPs of the systems that are not in this check and the air conditioning packs to decrease the pneumatic duct pressure to approximately 15 psi (which will give an N2 speed of 12.2%).
This N2 speed of 12.2% is equivalent to 468 rpm of the EDP drive shaft. At a drive shaft speed of 468 rpm, the pump will supply a flow of 4.5 gpm at outlet pressures of less than 2900 psi. At outlet pressures less than 2900 psi, the pump is at its full displacement. At outlet pressures between 2900 and 3000 psi, the pump displacement decreases as the outlet pressure increases.
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747-400 MAINTENANCE MANUAL
S 216-559
(2)
Read the HYD PRESS indication on the EICAS display.
(a)
If the pressure in the hydraulic system is more than 2500 psi, no correction is necessary.
(b)
If the pressure in the hydraulic system is less than 2500 psi, you must do the Hydraulic System No. 1, 2, 3, or 4 Internal Leakage Check procedure. That procedure will find the cause of the low pressure.
NOTE: You can use Figure 611 to find the leakage rate which is
____ equivalent to the hydraulic pressure indication. If the system pressure is low, it is recommended that you do an internal leakage check. However, if you isolate parts of the hydraulic system and monitor the pressure, you can find the location and the rate of the leakage. Use Figure 611 to make an estimate of the leakage related to a pressure increase. In some conditions, you can isolate a component which has too much leakage with this procedure.
An outboard control valve for the TE flaps in the hydraulic system No. 4 is an example. High leakage in this component, while the remaining part of the system has low leakage, will show the pressure indication which follows:
-
The system pressure is less than 2500 psi with the airplane in the cruise configuration.
-
The system pressure increases to 3000 psi when you do not go through the control valve for the TE flaps and you move the flap handle.
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