John_Tullamarine,
We are basically a FAR-121 Flag carrier (non US based) and are usually considered conservative. The regulations permit us to reduce power by 25% of the rating in use. On Boeing aircraft we have the option of 3 takeoff ratings (Max, -10%, -20%), but we only use the 20% thrust reduction on the B747-400 to reduce VMCG on contaminated runways. We do not use it on other aircraft because neither the aircraft manufacturer or the engine manufacturer can quantify the benefits of doing so.
On the B777, Chapter 04 Performance was replaced by a computer program called AFM-DPI, there are no paper charts anymore. This program allows me to demonstrate how we use reduced thrust. (This isnt the format used by crews, they just see the normal Boeing multiple runway format, which are slightly more conservative that the AFM calculation)
Light Weight Actual Temperature.
Configuration
-------------
Model = 777-200 Brake Type = Cat A
Engine = GE90-90B Brake Config = All Operative
Thrust Derate = .0 Tire Speed = 235.00 MPH
Flaps = 5 Center of Gravity = Forward
Air Cond Bleed = On
Anti-ice Bleed = Off
Alternate Performance Level(s): Ten Minute Takeoff Thrust
Conditions
----------
Brake Release Gross Weight = 220000 KG
Certificate Limitations: Maximum Takeoff Weight = 286897 KG
Actual Temp = 15.0 DEG C
Assumed Temp = 15.0 DEG C
Pressure Altitude = 0 FEET
Runway Wind = 0 KNOTS
Runway Cond = Dry
TORA = 9000 FEET
TODA = 9000 FEET ASDA = 9000 FEET
Slope (Takeoff) = 1.00 PERCENT Slope (Accel-Stop) = 1.00 PERCENT
Takeoff Distances
-----------------
All Engine Takeoff Distance = 5569 FEET
All Engine Takeoff Run = 5084 FEET
One Engine Inoperative Takeoff Distance = 6112 FEET
One Engine Inoperative Takeoff Run = 5454 FEET
Accelerate-Stop Distance = 6112 FEET
Critical Distance(s) : One Engine Inop TO, Accel-Stop
The runway is 9000 feet long, so we convert that excess length into a power reduction, in this case using the 10% fixed derate and then finding the maximum assumed temperature.
Maximum Assumed Temperature Limit
---------------------------------
Field Length Limit 49.3 DEG C
Maximum Assumed Temperature Takeoff Distances
---------------------------------------------
All Engine Takeoff Distance = 8648 FEET
All Engine Takeoff Run = 8049 FEET
One Engine Inoperative Takeoff Distance = 8975 FEET
One Engine Inoperative Takeoff Run = 7935 FEET
Accelerate-Stop Distance = 8975 FEET
Critical Distance(s) : One Engine Inop TO, Accel-Stop
We are now using all the runway, as permitted by the FAR's and the AFM.
My understanding from Boeing Flight Ops Engineering people is that this is a common procedure amongst their operators, you obviously consider it dangerous, so please tell us what limit would you use?
If you dont agree with procedure, I guess that you dont agree with improved climb or the Airbus philosophy of optimized airspeeds either?
As for your intention of
studiously avoid flying with your company , if we are considered "unsafe", you better get used to walking........
Mutt
