Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Flight Directors off for stall practice in the simulator.

Tech Log The very best in practical technical discussion on the web

Flight Directors off for stall practice in the simulator.

Old 17th Jun 2018, 06:02
  #1 (permalink)  
Thread Starter
 
Join Date: Oct 2007
Location: Here and there
Posts: 386
Flight Directors off for stall practice in the simulator.

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.

Last edited by Judd; 17th Jun 2018 at 06:13.
Judd is offline  
Old 17th Jun 2018, 06:45
  #2 (permalink)  
 
Join Date: Sep 1999
Location: Middle England
Posts: 606
The instructor involved sounds like one of those nit picking idiots we all encounter from time to time. What really matters is how the manoeuvre is flown and how controlled flight is restored without exceeding limitations.

Whether the flight director is ignored or switched off is really secondary and at best a discussion item. If it happened for real I suspect it would be at the bottom of the list of priorities.

I'm a TRE and would not award a fail simply because somebody chose to turn the flight director off.



Last edited by 763 jock; 17th Jun 2018 at 08:06.
763 jock is offline  
Old 17th Jun 2018, 07:42
  #3 (permalink)  
 
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
In defence, m'lud:

The exercise was stall recovery. Did I achieve that satisfactorily? Yes. Is there a company SOP about FD's ON/OFF? No. Therefore should that have any effect on the assessment of the manoeuvre? No. IMHO. (TRE). Sounds like personal opinion, and failing on that basis for a specified manoeuvre seems overly harsh.
Should PF, during the startle factor of a stall recovery, be giving priority to FD's ON/OFF? Debatable. Should a current pilot be able to control attitude without an FD? Yes. FD is OFF, stall is recovered, TOGA is pushed with MAA set, would not the FD reappear until ALT AQ? Should that cue be enough for the level off? Probably.
Surely a fail for such an item has an appeal to HOT?
RAT 5 is offline  
Old 17th Jun 2018, 08:40
  #4 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,702
The instructor involved sounds like one of those nit picking idiots we all encounter from time to time. What really matters is how the manoeuvre is flown and how controlled flight is restored without exceeding limitations.

Whether the flight director is ignored or switched off is really secondary and at best a discussion item. If it happened for real I suspect it would be at the bottom of the list of priorities.
Couldn’t agree more. Time-critical event training is all about reinforcement of technique for dealing effectively with something that would likely lead to a crash in short order if uncorrected. Stall, hard GPWS, windshear, airspeed unreliable, etc. The last thing you should be thinking of while flying these manoeuvres is artificial altitude constraints. It’s an emergency: the sky is yours.

Yes, when back in a normal flight regime you can start paying more attention to clearances, altitudes and the like but that’s sugar frosting compared with handling the escape correctly.
FullWings is offline  
Old 17th Jun 2018, 13:10
  #5 (permalink)  
 
Join Date: Jun 2006
Location: Australia
Posts: 1,186
Is there a company SOP about FD's ON/OFF? No. Therefore should that have any effect on the assessment of the manoeuvre? No.
That being so, why not leave the FD on while conducting steep turns as part of an IPC? After all, the pitch bar may help you to maintain altitude and the roll bar reminds you when to straighten up on the original start heading.. .
Tee Emm is offline  
Old 17th Jun 2018, 15:01
  #6 (permalink)  
 
Join Date: Dec 2002
Location: UK
Posts: 2,276
Catch 22, a wicked problem, depends on viewpoint, on which window we look through; there are rarely answers. e.g. is your glass half empty or half full?

A quibble with language (my window) is that the good advice to ‘look through’ the FD is a normal function implying a combination of attitude and FD, whereas in a stall we would wish pilots to ‘ignore’ the FD - focus on attitude, probably an even more difficult task than combination. How do you mentally reject an information display which in normal circumstances could be the dominant reference, but where with the effect of surprise and startle in an emergency the mind reverts to first learnt, most used, information.

This debatable point offers a potential alleviation for all parties to understand the issue and to debate the relative safety merits of situations. Thus a learning view, vice an examining pass/fail position, would highlight the importance of understanding the situation, particularly the precursors, what is important, and how to avoid the situation; and if unable, how to recover.

We are told with these types of problems to look at the bigger picture. So my half-full glass, emptied into a larger glass could be judged near empty - best bitter please. And if you are having this discussion in a bar you are clearly drinking with the wrong people.

Thus this ‘technical problem’ (actually philosophical and human) should be posed to management - the bigger picture; as a safety report, to the manufacturer and regulator for a wider view of policies, design, training, examining, mandates, and choice and use of procedures.
safetypee is online now  
Old 17th Jun 2018, 17:49
  #7 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,160
FDs should be switched off if they are not to be followed is a general suggestions. It is applicable for any planned situation like visual approach. Steep turns are not done in commercial aircraft. Stall is not a planned manoeuvre. Once the aircraft has stalled at lower altitude immediate memory items for recovery should be applied i.e. lowering the nose, application of required thrust etc. Pilot who is doing the recovery should have the knowledge that FDs don't provide unstall guidance and ignore and just fly the attitude. If it's not in the procedure why waste time switching off FDs? It's a serious event and should have a standard procedure.
vilas is online now  
Old 17th Jun 2018, 18:01
  #8 (permalink)  
 
Join Date: Dec 2006
Location: The No Transgression Zone
Posts: 2,471
In the US on the ATPL practical test and initial type training a 45 degree bank angle steep turn must be completed
Pugilistic Animus is offline  
Old 17th Jun 2018, 19:03
  #9 (permalink)  
 
Join Date: Mar 2006
Location: USA
Posts: 2,265
"Ignore the FD"

Easier said than done sometimes. I'd agree with the pilot in question. Turn off the FD. Fly the plane. Then worry about what the FD thinks about the FCU selections.
Check Airman is offline  
Old 17th Jun 2018, 19:52
  #10 (permalink)  
 
Join Date: Aug 1999
Location: England
Posts: 1,046
We could always go a bit radical and fly the recovery as specified by the manufacturer.
Capt Pit Bull is offline  
Old 17th Jun 2018, 22:20
  #11 (permalink)  
 
Join Date: Sep 2016
Location: USA
Posts: 718
Originally Posted by Tee Emm View Post
That being so, why not leave the FD on while conducting steep turns as part of an IPC? After all, the pitch bar may help you to maintain altitude and the roll bar reminds you when to straighten up on the original start heading.. .
So that we don't remove the 5 minutes per year of practice of raw data flying that airline pilots get?
Vessbot is offline  
Old 17th Jun 2018, 22:21
  #12 (permalink)  
 
Join Date: Oct 2004
Location: Germany
Posts: 63
Do not use the FD commands during stall recovery.
Actually, you can use the FD; one useful information is the altitude selected (if it was). It is easy to climb back to cleared altitude while using the FD after recovering.
rak64 is offline  
Old 18th Jun 2018, 02:29
  #13 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,160
Ignore the FD"
Easier said than done sometimes.
Sure! But isn't this a simulator exercise? We practice in simulator many things that are not that easy to acquire competance to do them in real life when the need arises. In Airbus if stall happens when the bird is on hitting TOGA will bring FDs back. So good practice to fly ignoring FD. I think the important thing is to be able to apply immediate recovery actions with or without FD.
vilas is online now  
Old 18th Jun 2018, 02:40
  #14 (permalink)  
Beau_Peep
 
Join Date: Apr 2007
Location: India
Posts: 228
FD may confuse

just like in TCAS RA, stall recovery has nothing to do with FDs. FDs must be switched off if you get into stall for more focused recovery.
IFLY_INDIGO is offline  
Old 18th Jun 2018, 03:44
  #15 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,160
INDIGO
Surely FDs have nothing to do with recovery from stall and they can be confusing if one doesn't know that they are not to be followed. In TCAS immediate action is FDs off and it is mandatory for a different reason. In automatic TCAS you don't switchoff the FD. EGPWS is a memory item where you ignore FDs. Stall recovery also is a memory item and it doesn't contain action on FDs. In low level stall one doesn't know how much height will be lost. The immediate actions in a stall are reduction of a AoA, wing level, thrust as required, checking speed brakes in which the PF must do before doing anything else. Forgetting any of these can be fatal. Putting the nose below the horizon with FD on or off should not be a such big deal. You may be doing the approach with the bird and if switch off FD first it will reappear with TOGA then you again switch it off? Obsession with FD off which is not essential action can also become a distraction and make you forget something more critical to recovery.

Last edited by vilas; 18th Jun 2018 at 05:40.
vilas is online now  
Old 18th Jun 2018, 04:06
  #16 (permalink)  
 
Join Date: Jun 2006
Location: Australia
Posts: 1,186
So good practice to fly ignoring FD.
Easier said than done; like ignoring the guy coming your way at night and blinding you with his headlights on High beam
Tee Emm is offline  
Old 18th Jun 2018, 04:17
  #17 (permalink)  
 
Join Date: Jun 2000
Location: Australia
Posts: 4,180
Pilot who is doing the recovery should have the knowledge that FDs don't provide unstall guidance and ignore and just fly the attitude. If it's not in the procedure why waste time switching off FDs?
Airline pilots probably spend 95% of their flying hours following flight director commands. All the more reason for switching the FD off in a critical situation like a stall recovery where blindly reverting to habit and following FD needles could lead to a more serious problem.
Centaurus is offline  
Old 18th Jun 2018, 05:48
  #18 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,160
Then why it is not a memory item? All memory items are laid down procedures. Is it because the manufacturer is not capable of thinking like us? And about stall only the test pilot has actual experience. It may not be easy that is why we practice in the Sim. Switching off FD is helpful but not at the cost of mandatory actions. Flying accurately and not stalling in the first place appears simpler than recovery. Most stall incidents are because of poor flying.

Last edited by vilas; 18th Jun 2018 at 06:00.
vilas is online now  
Old 18th Jun 2018, 05:55
  #19 (permalink)  
 
Join Date: Jul 2000
Location: Dubai - sand land.
Age: 53
Posts: 2,828
Originally Posted by Capt Pit Bull
We could always go a bit radical and fly the recovery as specified by the manufacturer.
My thoughts exactly Fairly pointless discussion about the FDs.
White Knight is offline  
Old 18th Jun 2018, 07:09
  #20 (permalink)  
 
Join Date: Jun 2002
Location: Wor Yerm
Age: 66
Posts: 0
“Failing” someone during trading is a good measure of a company’s training standards and the trainers within. It happens, but normally this is for repetitive gross handling errors, diabolical CRM, dreadful preparation. But a “fail” for asking for the FD’s to be turned off? This speaks volumes. As has been pointed out already, the FD should not be followed for a recovery because it will not give any useful information. It would also be reasonable to question its validity following a stall recovery. The only issue I could see is do you actually need to turn the things off as it would be better to concentrate on the recovery rather than flick switches.

PM
Piltdown Man is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.