B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 180; Flight Crew Total 20000; Flight Crew Type 9000
Confusion; Human-Machine Interface
No Specific Anomaly Occurred All Types
General None Reported / Taken
Aircraft; Manuals; Human Factors; Company Policy
New computer performance data system is either flawed or being misapplied by our flight operations group. For example: for today's takeoff from Munich Runway 26R; the old system (FMS provided) would have been V1; VR and V2 speeds of 151; 154 and 158 KTS. The sys provided speeds are 164; 166 and 169 KTS. Thus; with the old system; you continue the takeoff with speed once at or above 151 KTS but; with the new system; you continue the takeoff with speed at or above 164 KTS. Thus; B777 pilots may ABORT their takeoff at HIGHER speeds (164 KTS vs 151 KTS) with this new system; which is closer to the Vmbe [Maximum Brake Energy] speed as well as closer to the far end of the runway. However; sufficient runway remains to successfully abort. Conclusion - Our Carrier prefers to have the aircraft ON THE GROUND. Since all the Emergency Vehicles are on the GROUND; that makes sense. With the imprecisely defined wet runway data; the crew is directed to CONTINUE the takeoff when V1 is the equivalent of Vmcg [Minimum Control speed Ground]. This is reportedly due to controllability concerns with an engine loss. Conclusion - our Carrier prefers that an aircraft be AIRBORNE; committing to taking off at the LOWEST possible V1 speed IF there is a chance of a slippery runway. However; an ABORT would be highly desirable for any number of serious mechanical problems; even with an engine loss. Even an engine FIRE does not necessarily mean a loss of thrust on the engine. In any emergency near Vmcg; reducing the thrust to idle eliminates directional control concerns anyway if they were to exist at all. That is why the Captain's hand is ON the THROTTLES until committed to taking off. Under normal conditions; the new system produces a HIGHER V1 speed while the ill-defined wet runway rule produces a LESS SAFE operation with a MINIMUM V1 speed. The risk exposure is indefensible. The wet runway procedure eliminates; actually prohibits; an ABORT at the speeds just above Vmcg. Instead; an extended takeoff roll is required unnecessarily; with or without asymmetric thrust concerns. A takeoff can be in doubt for many reasons besides an engine loss. Continuing the takeoff requires any number of additional procedures related to the malfunction; as well as dumping fuel; navigating; conducting an approach in a degraded condition. The training center's analysis; defending their position; stated that it gave the pilot 'more time to practice' a long takeoff run with asymmetric thrust. Continuing the takeoff [for steering practice] is the equivalent of choosing the furthest exit in a burning building to get practice dodging falling debris. That does not justify this solution for a once in a lifetime emergency. The FAA's own Takeoff Safety pamphlet states a widebody crew could expect one of these events every 30 years. Our own airline has a much better batting average. The fact that the new program can assign a wide range of speeds for V1; from Vmcg to Vmbe; means that our own organization has set this illogical policy. If you cannot trust a crew to abort a takeoff just above Vmcg; why would you have confidence in them completing a series of far more difficult procedures and checklists which result in greater safety risks; greater fuel costs; and greater demands on maintenance? Changing the slippery runway low V1 speed policy should be closely examined by pilots other than the pilots who made that determination.
A B777 Captain believes his airline is improperly utilizing aircraft takeoff performance data particularly with respect to takeoffs from a slippery runway.