Date: 202008
Location: ZZZ.Airport, US
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Confusion
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
Result: General None Reported / Taken
Contributing factors: Chart Or Publication; Procedure; Human Factors
Primary problem: Procedure

Narrative: Recently on a departure from ZZZ; a question came up regarding the Engine Out procedure for Runway XL. The Engine Failure on Takeoff Procedure for XL calls for tracking RCL and a non-standard acceleration of 1;300 feet MSL/1;000 feet AGL as identified from the ACARS performance data at the bottom.  The ACARS printout is attached. The FMC performance data uplink for this departure on this day; uplinked 896 ft. as the engine out acceleration height.So there was a difference for the engine out acceleration height on the two data sources; the ACARS printed data; 1300 MSL/1000 AGL; and the uplinked ACARS data in the FMC showing 896 feet. for the engine out acceleration height. This was discussed between some LCA's and XXXXX provided an answer from Performance Engineering highlighted the reason for the discrepancy; which is below:Some time ago I discussed this issue with flight standards and ask that there be an update to the FM to provide the background.  I think this was accomplished in the 737 FM but I am not sure about any of the other fleets.  Before I answer the question; I will state that either number may be used and both are valid. We still have some aircraft that do not uplink the engine out acceleration heights.  Because of this; whenever we review an airport we have a safety requirement to determine the engine out height for the aircraft with no uplink.  Since the procedure information is plain text; we have to determine the highest of the required altitudes for an array of input conditions.  In the case of this condition we computed and noted the 1;300 feet.  When computer software performed the actual computation; it used the specific conditions for the departure to determine the 896 feet altitude; which is uplinked to the 777.  I believe the Airbus is the only one that does not receive the uplink. So XXXXX has answered the discrepancy between the two values.  The reason for the report is that this is not readily apparent in the FM for the 777; and most likely pertains to all the Fleets that uplink data to the FMC; 787; 777; 757; and 737.  The B777 had a recent change on FM 3.80. 4 on [month/year]; which does address this; but it is not very clear that there may be two different values for engine out acceleration heights; but only highlights to use the uplinked data.  While both values are legal; the uplinked data is tailored to the conditions of the day; rather than the ACARS engine out data; which would be a worse case number. Could Standards identify the why behind the recent change on FM 3.80.4 to help pilots understand why two values may appear for the same data point?   XX_2 so could a Fleet Newsletter be drafted to explain in more detail; this issue and the Performance Engineering answer to this discrepancy?




Synopsis: Air carrier Captain reported concerns with the GUM Runway 6L engine out procedure.