P92-CF (EMDP) Transfer Bus 2 - 115v ac (EMDP)
P6-2B (EDP) DC Bus 1 Sect 22 - 28v dc (EDP)
System A Hydraulic Pressure near 0 PSI or
System A Hydraulic Quantity near 0 USG or
Both Hydraulic Pump LOW PRESSURE amber lights AND
System A Flight Control LOW PRESSURE amber light AND
FEEL DIFF amber light (when TE Flaps UP) AND
On GND
During the exterior inspection of the main wheel well, always take a look at the return filter, located on the forward bulkhead below the hydraulic reservoir. When the filter is clogged, a red differential pressure indicator appears on the top (if OAT above 2 degrees C / 36 F). A clogged filter may indicate fluid contamination due to wire-edge particles originating from aircraft systems powered by system A. Call maintenance if the indicator pin is visible.
In FLT
With hydraulic system quantity not zero, first verify the EDP! The EMDP is located in the E&E, so the pump cannot be reset in FLT.
If the hydraulic system is lost because of a dual pump failure, consider re-engaging an overheated EMDP (Abex type) after sufficient cooling time. Use the overheated pump during a short time to configure the airplane for landing. However, depending on the type of EMDP installed, this may not be possible. On Vickers type EMDP electric power is automatically removed during the overheat condition, causing the LOW PRESSURE amber light to illuminate together with the OVERHEAT amber light.
FLT CONTROL switch Confirm STBY RUD
When moving this switch to STBY RUD, closely observe that :
- The System A Flight Control LOW PRESSURE amber light extinguishes
- The STBY RUD ON amber light illuminates
- The Standby Hydraulic LOW QUANTITY amber light does not illuminate
- The Standby Hydraulic LOW PRESSURE amber light illuminates momentarily, then extinguishes (this confirms pump engagement) However, with a loss of system A or B on GND and wheel speed above 60 kts or airborne and flaps extended, the flaps extended, the Standby Hydraulic pump engages automatically, and consequently the LOW PRESSURE amber light will not momentarily illuminate anymore.
If the Standby Hydraulic LOW PRESSURE amber light remains illuminated.
the Standby Hydraulic System is not pressurized.
Refer to SUBSEQUENT FAILURE(S).
Automatic Flight Autopilot B is available
Engines, APU Engine No 1 Reverser has standby hydraulic system pressure. Expect a delayed and slower deployment.
Flight Controls Flaps extension, Electric Trim and Yaw Damper are available. Flight Spoilers 2+4 and 11+9 are inoperative. Roll rate in turns and speedbrake effectiveness in descent is reduced.
Landing Gear Manual gear extension. Once extended, the landing gear cannot be retracted. Delay gear extension until established on long final. Normal nose wheel steering inoperative. The Manual Extension Access Door must be closed for Altn Nose Wheel steering! If dispatched with Alternate Nose Wheel steering INOP, avoid wet runways with crosswind. Below 60 knots use differential braking. Normal brakes, autobrakes and antiskid remain available.
Approach Request radar vectors to long final for manual gear extension. If flaps are desired before manual gear extension, limit flaps to 10 to avoid an annoying configuration warning horn.
Landing Ground and Flight Spoilers - Refer to PI [Advisory Info - Non-Normal Configuration Landing Distance.] Use Flaps 40 and autobrakes to compensate for INOP Ground and Flight Spoilers. Avoid short and/or wet RWY. SOP Landing minima CAT 1 - Verify Lower Landing Minimum Requirements Table.
Go-Around Go-around with landing gear extended, verify obstacles
Diversion The FMC does not provide fuel progress data for operations with the landing gear down! Fuel penalty with landing gear extended is approximately 50%. Refer to PI [Gear Down - LRC Enroute Fuel and Time]
ATC Advise ATC that you are unable or have difficulty in vacating the runway after landing due to an inoperative nose wheel steering (except if alternate nose wheel steering is installed)
Cabin Crew SOP - Brief the CCM using company guidelines and call-outs. Advise the CCM to keep passengers seated after landing
Ground Handling If alternate nose wheel steering is dispatched inoperative, advise ground handling you need towing assistance after landing.
SUBSEQUENT FAILURE(S)
LOSS OF STANDBY HYDRAULIC SYSTEM
Perform the NNC [STANDBY HYDRAULIC LOW PRESSURE] when time available, but certainly before the Descent Checklist Deferred Items of the NNC [LOSS OF SYSTEM A]
- Rudder control is available through system B
- Reverser Engine No 1 is inoperative. Refer to PI [Advisory Info - Normal Configuration Landing Distance] and obtain the landing distance adjustment from the ONE REV column.