Flight Directors off for stall practice in the simulator.

[Judd]

It is well known there are operators who mandate that the flight directors must be on and programmed for all phases of flight. There may well be technical reasons for this depending on aircraft design. That said, it would be no surprise to some, that automation dependency also plays a significant part with those sort of company directives.

During type rating training in simulators the approach to stall and stall recovery is usually practiced. This includes during on final approach in the landing configuration where ground contact is a factor. The pre-flight briefing may include FCTM advice such as "Ensure the proper flight director modes are selected for the desired manoeuvre. If the FD commands are not to be followed the FD should be turned off. Do not use the FD commands during stall recovery. FD commands are not designed to provide guidance to a recovery or approach to stall or stall."
The QRH also states under Approach to Stall or Stall recovery, a Note which says "Do not use flight director commands during recovery."

Having now set the scene, the decision has to be made by the instructor whether or not to turn off the FD for the exercise. On the other hand, as it is likely that in real life the FD will already be on during the instrument approach during which a stall or approach to stall has occurred, maybe the FD should be turned off for the recovery? After all, Boeing advice is: "If the FD commands are not to be followed the FD should be turned off."

Some may argue that because a go-around will take place once the aircraft has recovered from the stall, the FD should remain on during the manoeuvre to provide pitch guidance for levelling out at the missed approach altitude, if the stall occurred in IMC. Their argument being that the pilot should avoid being distracted by un-programmed FD indications and that he should be able "look through" the FD needles to see the nose attitudes during stall recovery. While some pilots claim that they can "look through" the FD indications to see what is behind them, others claim they are seriously distracted trying to see behind the needles and prefer to turn off the FD as part of the recovery.

The catalyst for this post was a colleague who was given a "Fail" mark for requesting his PM to immediately switch off both FD's as part of the recovery from the approach to stall. The instructor was of the view the FD should be left on during the whole exercise since the pitch bar indication would serve as a reminder of the missed approach altitude. While that may be true, nevertheless the priority in such a situation is a proper appreciation of nose attitude during the recovery; particularly as GA thrust used where ground contact is a factor, would cause a strong pitch up change of trim and may even lead to a delayed stall recovery. This is where raw data instrument flying skills become paramount. As Boeing reiterates: "Do not use FD commands during recovery." This would suggest that in event of an inadvertent stall the FD should be switched off so that pilots are not seduced into following erroneous or inappropriate FD commands .
Comments appreciated.