#4 ADP Inop

[Roboman1]

Good Day All.
I'm looking for advice on how a pilot in line ops could best apply the following MEL procedure for the #4 ADP Inop.


SPECIAL PERFORMANCE NOTES (Demand Hydraulic Pump 1 or 4 Inoperative):
1. Use "Landing Gear Extended" Appendix performance from Flight Crew Operations Manual.
2. The takeoff weight limitation in FCOM need not be applied as the intent is to retract the landing gear
and continue the flight as normal. However, at takeoff weights greater than 720,000 lb (326,600 kg),
flaps up maneuver speed (VREF + 100 kts) may exceed VLO (270 kts). Therefore, ensure gear is
retracted prior to selecting Flaps UP.
Time required for retraction of the trailing edge flaps after takeoff will be much longer due to the slower
operation of the electric drive (36 seconds for hydraulic operation vs. 275 seconds for electrical
operation). Consequently, the Flight Crew Operations Manual charts 'Maximum Level Off Height' and
'Third Segment Distance' may not be valid for this situation. It must be assumed, for performance
calculations, that flap retraction is accomplished at Maximum Continuous Thrust.

3. Since Flight Manual performance data is not available to predict the airplane flight path with flaps down
at the end of the Certified Takeoff Thrust Limitation, the following is suggested:
A. Determine normal performance limited gross weight.
B. Determine maximum allowable weight for 'Extended Second Segment and MCT Cleanup', as
defined on the obstacle clearance chart in the Flight Crew Operations Manual.
C. If obstacles are present, ensure that they are cleared, either within the extended second segment
or in level flight beyond the second segment, reducing weight if necessary.
D. Use the smallest of A, B, or C.

The above method will usually penalize allowable takeoff weight significantly. However, it will ensure that all
obstacles are cleared and that engine out performance with flaps extended is sufficient to meet FAR
requirements at Maximum Continuous Thrust.

So the following questions come to mind:

1. Takeoff performance including obstacle clearance is obviously based on Gear and Flaps extended. Using the Landing gear extended Appendix in the FCOM under the following conditions Sea Level, 0 deg C, gives a climb limit of 363t (less the increments for anti ice/packs). Note 2 says the take off weight limitation need not be applied - since the intent is to retract the gear. Can this statement be explained to me please.

2. Note 3 B refers to "Extended second segment and MCT" clean up as defined on the obstacle clearance chart. Can I be directed to this note/chart - I presume in the FPPM but I cannot locate it.

3.Note 3 C - How should one comply with this requirement?

4. Is there a resource that could give me an example of how a flight crew should attack the requirements of these operational procedures?

Thanks
Rob

[Avi]

Something isn't clear here.
All of this just because the ADP (demand) pump doesn't run?

If the EDP runs, what is the problem to retract the gear and why should the flaps switch to secondary (electrical) mode (it may take longer a little bit because the system fluid supply is lower but the system does operative).

If both pumps don't run, it is a new ball game.

Cheers,

[Roboman1]

The take off performance of every take off is predicated on the loss of a critical powerplant. #4 ADP Inop and then losing the #4 engine at takeoff means the loss of the hydraulic system. Excellent chance the L/G will not completely retract and certainly not within the confines of the second segment (it may take a long time to get to 400' with gear and flap hanging out on 3 engines and you are required to be able to maintain 3.0% so weight reduction is required) obstacle clearance criteria.

[John H Watson]

If both pumps don't run, it is a new ball game.

The above method will usually penalize allowable takeoff weight significantly. However, it will ensure that all obstacles are cleared and that engine out performance with flaps extended is sufficient to meet FAR
requirements at Maximum Continuous Thrust.

I guess it assumes a worst case scenario... i.e. that the failed engine is the same engine that had a failed ADP.

(EDIT:  Sorry.. cross-posted)

[Britjet]

Exactly right. Hardy adjusted the windmilling EDP pressure recently with exactly this scenario in mind. Works very well!
Peter.