Exactly how do you use reverse thrust technique on the 737
The FCTM states:
Maintain reverse thrust as required, up to maximum, until the airspeed approaches 60 knots. At this point start reducing the reverse thrust so that the reverse thrust levers are moving down at a rate commensurate with the deceleration rate of the airplane. The thrust levers should be positioned to reverse idle by taxi speed, then full down after the engines have decelerated to idle....
A. Does that mean you very slowly move the reverse thrust levers down to the reverse idle detent watching the rate of airspeed decay as the aircraft itself is slowing down?
OR
B. Do you move the reverse thrust levers directly to idle reverse detent quickly so that by the time the N1 has rolled back from say 88 percent N1 (full reverse in some variants of 737) to idle reverse of 23 percent N1, the aircraft would have reached taxi speed.
Reason for the question is that some pilots move the reverse levers down so slowly after 60 knots that they are then forced to cancel reverse altogether as N1 passes say 50 percent when either the autobrakes or manual braking has reduced the airspeed so rapidly they are in danger of having significant high N1 as the aircraft stops.
It takes around 12 seconds for the engines to run down from 88 percent N1 in reverse to 23 percent N1 in reverse if the reverse levers are moved promptly (two seconds) to the reverse idle detent.