Do not override autobrake to shorten the landing distance??
Joined: Dec 2002
Posts: 2,776
Likes: 350
From: UK
SGC, in your scenario (#21) the wheels would not lock as the antiskid system will reduce the brake pressure to maintain wheel rotation whilst still attempting to achieve the ‘maximum’ retardation in the poor conditions. Hence some systems may be described as ‘cycling’ the brakes on-and-off on a low friction runway.
Retardation may not be as expected, but often crews are unaware of this at higher speeds particularly if thrust reverse is contributing a significant proportion of the retardation. However, after cancelling reverse, the relative ineffectiveness of the brakes may be sensed and could be interpreted as a brake failure due to the low level of deceleration.
For those who wish to know the Brake Pedal Force required to disengage autobrake (page 16).
Retardation may not be as expected, but often crews are unaware of this at higher speeds particularly if thrust reverse is contributing a significant proportion of the retardation. However, after cancelling reverse, the relative ineffectiveness of the brakes may be sensed and could be interpreted as a brake failure due to the low level of deceleration.
For those who wish to know the Brake Pedal Force required to disengage autobrake (page 16).
Thread Starter
Joined: Aug 2009
Posts: 6
Likes: 0
From: Sountern Sea
Override the autobrake to shorten the runway .. for me, is just apply the more force contunuously on the pedal until the aircraft in the taxi speed..
Seems like the reason not to do that as Airbus said is just to balance the brake temp and wear. isn't it?
Seems like the reason not to do that as Airbus said is just to balance the brake temp and wear. isn't it?
Joined: Oct 2005
Posts: 54
Likes: 0
From: USA
Next time you are out flying the 'Bus, simply print out the landing data. There, in black and white, from the aircraft itself, you will see that MANUAL BRAKING stops SIGNIFICANTLY shorter than either LOW or MED autobrakes.
That said, VERY FEW PILOTS would EVER think of standing on the brakes at touchdown and thus ANY runway shorter than MED brakes but longer than MAX MANUAL brakes should be viewed with significant skepticism as to landing performance (i.e. stopping on the hard surface), due to unknowns and unknowables.
There are certain runways we use that REQUIRE a go-around if the aircraft is not on the ground within the first 2000' because there is, IMHO, a rather large "fudge factor" that one must apply to any landing, due to the myriad conditions that can affect performance that may not be fully known or understood during the landing planning phase.
Happy Landings!
That said, VERY FEW PILOTS would EVER think of standing on the brakes at touchdown and thus ANY runway shorter than MED brakes but longer than MAX MANUAL brakes should be viewed with significant skepticism as to landing performance (i.e. stopping on the hard surface), due to unknowns and unknowables.
There are certain runways we use that REQUIRE a go-around if the aircraft is not on the ground within the first 2000' because there is, IMHO, a rather large "fudge factor" that one must apply to any landing, due to the myriad conditions that can affect performance that may not be fully known or understood during the landing planning phase.
Happy Landings!
