safetypee, bubbers44,
Autobrake MAX setting is different between Airbus and Boeing.
For Boeing it is the highest setting used for landing, and the setting used for takeoff is called "RTO", and is in a different position on the rotary switch (on the other side of "OFF"). That's how it is for the 737 classic and NG, and I assume it is similar on the 757.
On Airbus there are only 3 settings total, LO, MED and MAX. Approach SOPs say:
Originally Posted by A320 FCOM 3.03.18, SEQ 001, REV 36
[...]
AUTO BRK ..... AS RQRD
Use of autobrake is recommended.
Use of MAX mode is not recommended for landing.
On short or contaminated runways use MED mode
On long and dry runways, LO mode is recommended.
safetypee,
So I don't know about "poorly qualified", but I'd like to forward that compliment to the Airbus FCOM authors.
As bubbers44 has also pointed out, on a slippery runway, MAX autobrake will not produce harsh deceleration, the difference to MED perhaps (I could not find any information about this) being that MAX will commence braking at MLG touchdown, whereas MED has a 2 second delay. So, it may upset the cabin by quick derotation and possible hard NLG touchdown, even on contaminated runways. Manual braking at MLG touchdown, however, is permitted if deemed necessary.
On dry runways, at typical landing weights, although I agree that MAX autobrake would probably not damage the brakes and/or tyres, it would upset the cabin.
It still holds that I would not consider a landing "normal", if it is anticipated that dry patches (between wet/contaminated areas) capable of achieving in excess of 3m/s/s (~ 0.3 G) deceleration are
required. For any surface not capable of achieving more then .3 G of deceleration, MAX will make no difference.
Again, in extreme cirumstances, say, landing on a very short runway in strong crosswinds (making immediate full manual braking more difficult), autobrake MAX can be used.
bubbers44,
do you know if MAX autobrake on Boeing does in fact maximum possible braking, and that perhaps the difference between RTO and MAX autobrake settings is only a delay after MLG touchdown (or other conditions, such as Reverse thrust / Idle thrust plus tyre spin)?
I apologize for my ignorance on the matter of autobrake systems on Boeing aircraft.
Bernd