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Old 16th October 2004 | 04:30
  #7 (permalink)  
Old Smokey
 
Joined: Jun 2004
Posts: 1,843
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From: Australia
stuharri2002,

The question that you've posed requires a general response as opposed to the specific one that you seek. It will depend on the aircraft type, and much more so upon the operational circumstances facing the pilot.

The nature of the brakes and the reverse thrust system will have a large influence upon the pilot's choice of the Brake / Reverser mix. Most pilots will use a bit of both, depending on their aircraft.

Carbon brakes are more effective than steel brakes, and wear LESS at high settings and speeds. Steel brakes wear more at high settings and speeds. It follows from this that a 'Carbon brake pilot' will be much more inclined to use heavier braking and less Reverse than a 'Steel brake pilot'. It saves money on maintainance, fuel, and noise. The 'Steel brake pilot', on the other hand would be more inclined to use less brake and more reverse, again in the interests of economics.

The type of reverser fitted will affect the pilot's emphasis on it's use. Even on the same aircraft type, customers can opt for 'Full" reverse of both core and fan flow, or just fan. The latter is the more common, and somewhat less effective than reversing all engine gases. Not so bad in the era of carbon brakes.

Having said all of that, common operational procedure with my company (B777-200/300) is to always use at least Idle Reverse. This negates the negative effects to deceleration of forward idle thrust without significantly changeing noise and fuel useage. Higher reverse settings all the way up to maximum are commonly used in line with the operational scenario, particularly on wet runways, short runways, or where it is highly desirable to make turnoff at a specific point. Reverse thrust is applied immediately upon touchdown, and reduced to idle by 60 Kt, unless an urgent situation develops whereupon full reverse may be used all of the way to a stop.

Regarding spoilers, they deploy automatically upon touch-down, and stay deployed until retracted during taxy by pilot selection. They do automatically stow if an aborted landing is executed after thrust levers go to 'Go Around'.

Auto-Brake is always used, on the B777 there are 5 numbered settings. There's no standard setting, 2 and 3 are the day to day settings depending on stopping capability required, with 4 for wet / down-sloping / down-wind runways. There's one more for the really bad day. Company philosophy is leaning more and more towards more brake and less reverse. Manual braking is effected at about 50 Kt Ground Speed, so that you can moderate the stopping distance remaining in line with distance to the turn-off point, common sense.

It all depends upon many many things.
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