Re: Wing "flaps" that raise on landing

From:         rdd@cactus.org (Robert Dorsett)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date:         10 Feb 93 13:55:33 PST
References:   1 2 3
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In article <airliners.1993.155@ohare.Chicago.COM> watson@win.tue.nl (Bruce Watson) writes:
>In article <airliners.1993.120@ohare.Chicago.COM> rdd@cactus.org (Robert Dorsett) writes:
>>Flaps are *not* normally raised during the landing roll.  [...]
>
>   I have flown aircraft (eg. DH Buffalo) in which the standard procedure was:
>1. max flaps during approach
>2. after TD, retract flaps to the go around position
>   (done by the pilot-not-flying)
>3. if landing okay, throttles to max. reverse pitch.
>4. else, throttles to max. for the go around.
>
>At any rate, flaps were always retracted to the go around position. On most
>real HEAVYs this would all be done for you: on the 747-400, go around is
>okay (runway length permitting) anytime before going to reverse thrust; I
>suspect that in this case, double clicking the -400's go around throttle
>buttons on the ground will also retract spoilers, flaps to 20, and rotate
>for you as well as flying the MAP.

Go-around modes are explicitly autoflight modes.  They are limited to 
commanding automatic go-around thrust (assuming autothrottle installed) and 
appropriate go-around attitude.  Spoilers, flaps, and gear functions are
all independent systems, and must be selected separately.

The 747-400 landing roll procedure is (PF = pilot flying; PNF = pilot not
flying, all this from ops manual):

PF: 
 - Monitor rollout progress and proper autobrake operation.
 - Verify thrust levers closed and speedbrake lever UP.  Without delay,
   raise reverse thrust levers to the idle detent, hold light pressure until
   release, and then apply reverse thrust as required.
 - By 60 knots, initiate movement of thrust levers to reach reverse idle
   detent prior to taxi speed.  Position levers full down (forward thrust)
   when engines have decelerated to reverse idle.

PNF: 
 - Call "60 knots."

PF: 
  - Prior to taxi speed, disarm the autobrakes and continue manual braking
    as required.
  - Disengage autopilot prior to runway turnoff.

A warning is noted: "after reverse thrust is initiated, a full stop landing
must be made."  I would point out at this point that once the airplane is
on the runway, even before reverse thrust, the "commit" is made--only in very 
unusual circumstances would a crew decide to go around (actually, take off
again, since, technically, this wouldn't be a go-around) at this point, and 
that includes for reasons of avoiding aircraft that suddenly pop out of the 
fog, still on the runway.  Cf. the USAir LAX collision a couple of years 
ago.  Pilots tend to be very modal creatures, beyond certain points.


Taxi-in and park:

  Strobe lights: off.
  Inboard landing lights: off.
  APU selector: start, rlease to on.
  Weather radar: off.
  Speedbrake lever: down.
  Flap lever: up.
  Stabilizer trim: 6 units.
  Autobrakes selector: off.


The go-around procedure is:

PF: 
 - Push TOGA switch.  Call for "Flaps 20."

PNF: 
 - Position flap lever to 20.

PF/PNF: Verify rotation to go-around attitude and thrust increase.

PNF: 
 - Verify thrust adequate for go-around; adjust if necessary.

PF:
 - After positive rate of climb established, call for "Gear up."

PNF: 
 - Verify positive rate of climb then position landing gear lever UP.

Etc.

Therefore, I stand by my contention that flaps are not intended to be
used during the landing roll.  I suspect that what may be happening is that 
crews are raising flaps *after* the roll-out is "made," i.e., by 60 knots, 
rather than the prescribed procedure of after leaving the active runway--
perhaps with the intent of reducing surface contamination from sludge or 
water off the runway.  In this context, I would note that (a) the airspeed 
indicator is inaccurate under 60 knots, and (b) aircrews are notorious for 
underestimating their taxi speeds, which could cause them to start after-
takeoff procedures while their airspeed is still relatively high.  The vantage 
from the lower deck of the 747 probably gives the passenger a feeling of a 
greater ground speed than one would get from the upper deck, with an eye 
level nearly 35 feet off the ground.

I maintain, however, that the workload characteristics and hydraulic
system interactions are such that flap-manipulation during roll-out is
not indicated.
 
The procedure for the 757 is much the same; the procedure for the A320
seems to be the same, as well--autoflight restricted to thrust and 
attitude; all other systems "manual."  There are often independent special
systems, such as speed-brake arming modes, which will deploy when the
air/ground switch is closed; or auto-braking; but gear, flaps, spoilers,
and these systems are independent of the autoflight system.  One does not
*want* these systems completely automated, since hydraulic demands may be
out of proportion to the situation at hand, reducing the crew's effectiveness
in safely landing the airplane or executing a go-around.

But all this is just the recommended procedure, derived from the airplane
flight manual, which is the basis for certification.  Airlines may adapt these
and make up their own procedures.  If the chief pilot is an old bush pilot, 
he might advocate bush-pilot techniques.  I have an old SAS cockpit poster, 
for instance, of a 747-200 or -100, with some eight or nine HSI's and CDI's 
on the dash--apparently *their* chief pilot didn't like getting lost. :-)
Personalities still make an important impact on training and operations 
policies.




---
Robert Dorsett
rdd@cactus.org
...cs.utexas.edu!cactus.org!rdd