Originally Posted by megan
The Bangkok QF brought to light the airline was using a procedure as SOP that the manufacturer counselled against. Once again, where does it leave the poor sod in seat 0A.
In QF1's case, if there had been fatalities, the sod in seat 0A would have been legally required to carry the can, CAR 224 notwithstanding.
Regarding flaps 25 vice flaps 30, Boeing said;
Regarding the 747-400, Boeing recommends Flaps 30 be used to minimise landing distance and landing speed. Flaps 25 will provide better noise abatement and reduce flap wear. Therefore, flaps 25 is an acceptable flaps setting as long as the crew is satisfied that there is ample runway available for the given conditions.
while the Qantas Manual said;
PREFERRED LANDING FLAP IS 25. This will normally be used. The wear characteristics of the B747-400 carbon brakes are such that maximum life is obtained by maximising energy absorption and minimising the number of applications. This leads to the choice of Flap 25 with its higher landing speeds as the preferred landing flap setting. Use of Flap 25 also reduces fuel, time, and noise.
Flaps 30 gives lower landing speeds and hence the shortest landing distances. This setting should be used when:
• landing field length requirements are critical (for e.g. when you land too long, too fast, and too gently on a wet/patches runway and one engine at TOGA);
• landing at HGK [Hong Kong] R/W [runway] 13;
• landing on a contaminated runway; and
• landing in LOW VIS [visibility] conditions.
In regards to idle reverse thrust, Boeing said,
Boeing does not consider the standard practice of going to reverse idle (idle detent) only to be patently unsafe, but does think that it reduces the existing performance margins. It is acceptable pilot technique to do this (using good judgement) as an exception to the normal procedures when landing on a long, dry runway. We perceive, however, that there is a human factors issue of developing a habit pattern of not using reverse thrust beyond the idle detent. The pilot may then fail to respond quickly when such reverse thrust is needed during an RTO [rejected takeoff] or landing in some type of performance-critical situation. We therefore do not provide a “No Technical Objection” for this as the standard operating policy.
while the Qantas Manuals said;
At times and locations as specified in Company manuals, reverse thrust may be left at the reverse thrust idle position after touchdown. Sufficient runway must be available to provide the required Performance Manual landing field length increment. The Pilot-In-Command shall also consider runway surface conditions and be satisfied that a safe operation is assured.
IDLE REVERSE THRUST Idle Reverse Thrust should normally be used for all landings provided at least 300 metres of surplus runway is available. Use of idle reverse maximises carbon brake life by putting more energy into the brakes, reduces noise and reduces reverser maintenance costs.
This does not preclude the use of full reverse thrust should abnormal conditions exist.
the autobrake system on the B747-400 aircraft sets a particular deceleration rate and modulates the brake pressure to provide that programmed rate. If the thrust reverser is achieving a higher deceleration rate than required by the autobrake setting, the autobrake system will then reduce the pressure to the brakes. Therefore, to maintain a relatively high brake pressure, a comparatively lower r everse thrust setting is now desirable.
Initiation of idle reverse thrust after main gear touchdown will nullify all forward thrust from the engines, and permit the carbon brakes to operate at their peak efficiency.
In cases where landing field length is limited, or if any other operational considerations are likely to affect the landing roll or procedures, the Captain should elect to use full reverse thrust during the landing roll.
The Qantas procedure policies, especially in respect to idle reverse thrust, places the onus squarely on the PIC to determine whether or not the application of 'standard procedure/s' is appropriate, from a safety perspective, given the conditions. Regardless of the manufacturers 'opinion', legally, that's pretty much all they need to do.