Landing Questions

[avialuver33]

1. Are there ever times when a jetliner can land on a long enough runway so that reverse thrust does not have to be used?

2. On jetliners equipped with auto braking---does this mean the brakes are applied at a certain pressure, until a certain speed is reached? If so, do the pedals move in unison with the breaking action?

3. Does the nose wheel have to touch down before reverse thrust and brakes can be applied?

[dolly737]

1. On a dry runway the use of reversers is optional, although we usually always apply them to minimize wheel-brake wear ($$$). Just for info: Only about 20% of the total braking force is produced by reversers (they are ineffective at speeds below 60 kts)

2. Autobrakes normally decelearate the airplane on a pre-set RATE. It can be adjusted incrementally (A/B-Switch 1, 2, 3, MAX) and used until full-stop, but usually is switched off on discretion of the pilot-flying (rwy-vacation issue) at low speeds. The pedals (on Boeings) don’t move.

3. Nose-wheel touchdown is not necessary for wheelbrakes and reversers, but it is good practice to wait for it before using reversers because of better directional control in case of asymmetrical spoolup.

[start sequence 312]

1. Are there ever times when a jetliner can land on a long enough runway so that reverse thrust does not have to be used?
Yes. For example, when the runway is long enough and the taxiway to the terminal is located at the runway end. During a situation like that, it is usual to set the reverse thrust at idle only, with small brake application during the final landing roll.


2. On jetliners equipped with auto braking---does this mean the brakes are applied at a certain pressure, until a certain speed is reached? If so, do the pedals move in unison with the breaking action?
Yes and no. ABS regulates brake application based on selected deceleration rate. Some airplanes adjust brake pressure when reverse thrust is applied to keep deceleration level as required. For instance, if ‘Medium’ is selected, the ABS will keep at maximum rate for that level when reverse is not used, but regulates proportionally depending on how much reverse thrust is applied to bring the airplane to a complete stop within the deceleration rate selected. However brake pedals don’t move, unless during manual intervention.


3. Does the nose wheel have to touch down before reverse thrust and brakes can be applied?
It depends. On B737-200 nose wheel must be on the ground prior to using reverse thrust to avoid reverser doors ground contact during their movement from the stowed position to the deployed position. But B737 Classic and NGs don’t require it because they have a different reverse thrust system. The MD-11 has a protection to prevent thrust increase on engine number 2 (tail engine) beyond idle power until the nose wheel ground sensing switch has closed and the reverser is more than 90 percent deployed. Manual brakes can be applied even with the nose gear off the ground. There are some differences among airplanes but the ABS landing mode is activated when the spoilers are deployed, throttles retarded to idle position and brake pedals released.

[mutt]

1. Are there ever times when a jetliner can land on a long enough runway so that reverse thrust does not have to be used?

ALMOST ALWAYS! Dispatch requirements state that you must be able to land within 60% of the runway length WITHOUT REVERSERS!

Mutt.