Autobrakes
Join Date: Jul 2000
Location: West
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Depends on operator, acft, pilot.
There is nothing in your profile that indicates how deep into aviation you are. My apologies if the following is over-simplified.
Not all airliners are outfitted with autobrakes. Some that are do not normally use them except for specific conditions (runway contamination, strong winds requiring high approach speed, shorter runway, or any combination). For the aircraft I currently fly, our company specifies the use of autobrakes on level two as a minimum. There are other conditions in which higher levels are used, such as a landing in Mumbai (Bombay) during rain, or landing on JFK's shorter runway with gusty winds and wet conditions, or Category III approaches (very low visibility).
Not all airliners are outfitted with autobrakes. Some that are do not normally use them except for specific conditions (runway contamination, strong winds requiring high approach speed, shorter runway, or any combination). For the aircraft I currently fly, our company specifies the use of autobrakes on level two as a minimum. There are other conditions in which higher levels are used, such as a landing in Mumbai (Bombay) during rain, or landing on JFK's shorter runway with gusty winds and wet conditions, or Category III approaches (very low visibility).
Join Date: May 2000
Location: New York
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I fly the 747-200 freighter. Landings are typically close to max landing weight - 630k lbs.
Generally speaking it is up to the captain what setting to use. In some circumstances (automatic approaches, slippery rwy, etc), the company will dictate use of autobrakes, and that make good sense, and something a prudent crew would do anyway.
Generally, though, on a dry long runway (10,000 feet), I'll use manual braking and let the reverse thrust slow the aircraft to 80k or so before manually braking. That will keep the brakes as cool as practical if the aircraft is turning quickly. Keep in mind that on minimum autobrakes, the system will try and maintain a 4'/sec/sec decel rate. Coincidentally, full reverse thrust will decel you about the same rate, so with min autobrakes they are hardly applied, except for the initial braking after wheel spin up after landing and before the reverse thrust is effective.
Generally speaking it is up to the captain what setting to use. In some circumstances (automatic approaches, slippery rwy, etc), the company will dictate use of autobrakes, and that make good sense, and something a prudent crew would do anyway.
Generally, though, on a dry long runway (10,000 feet), I'll use manual braking and let the reverse thrust slow the aircraft to 80k or so before manually braking. That will keep the brakes as cool as practical if the aircraft is turning quickly. Keep in mind that on minimum autobrakes, the system will try and maintain a 4'/sec/sec decel rate. Coincidentally, full reverse thrust will decel you about the same rate, so with min autobrakes they are hardly applied, except for the initial braking after wheel spin up after landing and before the reverse thrust is effective.
Our company sop for 74 classic freighters states min for dry rwy '9000 or longer otherwise medium. Will disconnect by applying manual brakes to let reversers do their work. As stated above brake cooling can be an issue on the shorter turns.
