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Flight Directors off for stall practice in the simulator.

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Flight Directors off for stall practice in the simulator.

Old 18th Jun 2018, 07:25
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FDs are great tools for guidance but pilots should know when it's time to ignore them even in normal daily operations: For example a very bumpy approach couple with a potentially unstable glideslope guidance ( Eg Beijing ILS 36L) trying to chase the FD bars accurately when the aircraft is tossing around is almost impossible and certainly not recommended. Knowing the pitch and power of your aircraft is a must.
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Old 18th Jun 2018, 08:28
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FDs must be switched off if you get into stall for more focused recovery
Interesting observation. Hand flying while following FD commands normally requires full concentration on keeping the FD needles centred in the tiny square. The theory being if the needles are exactly centred then eye scanning of other pertinent instruments are of secondary importance. Pundits will claim that despite FD's being prominently displayed, the pilot should still use the six pack scan in the PFD. Ideally yes - but that rarely occurs. With many pilots, Situational Awareness can go out the window the moment they are locked on to the FD.

With engine failure at V1 and continue, some pilots have trouble following FD commands and often overcorrect. The result is they start to chase the needles which only makes things worse. One temporary solution is to switch off the FD. This clears the PFD so the pilot can concentrate on the "little aeroplane" nose attitude and bank indications. Others simply switch their scan to the standby ADI and fly on that, which is devoid of distracting needles. When introducing engine failures on take off for the first time, it can be helpful for the candidate to practice these with FD's off so that a clearer picture of the artificial horizon is seen without the distraction of wavering FD needles . Once the candidate is competent at flying this raw data display, FD use can be introduced.

Last edited by Centaurus; 18th Jun 2018 at 08:39.
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Old 18th Jun 2018, 11:57
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The FD isn't a no-go item. With the exception of a handful of procedures, its use is at the discretion of the PF. If the PF says FD off, then FD off. Particularly in a stall, where the FD will be commanding the exact opposite of what needs to be done (se AF447) it's a useless instrment. Why expend the extra brain power to look behind the FD when you can just turn it off?
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Old 18th Jun 2018, 12:43
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W Knight, et al, the original question is at the heart of many safety issues; it’s not just the FD, but human - system interaction and the wider issues of system design, training, checking, procedure advice / mandate, etc.

It’s difficult to ignore salient guidance cues overlaying the primary reference instrument - fundamental aspect of human performance - a similar cognitive feature as with illusion, how do you ignore an illusion (only after you realise that you have been mislead? ).

For those who wish to switch the FD off, another SOP, more paper work, memory item, and another opportunity to ‘fail’; how often do SOP writers ‘fail’.

It is impossible to expect every pilot to remember to take the correct action in every situation, particularly with the surprise of stall warning or stick push. Evidence from many accidents suggest that humans forget when surprised, cross crew monitoring and communication break down. ‘Pilot did not follow SOPs’, ‘did not recover from the stall using the correct procedure’, weak CRM, etc.

Many of modern day safety issues challenge the concept and limits of human performance; we cannot know and recall the ‘right’ thing to do in every situation.
The industry requires a different approach for these issues, but change is far from easy.

For those who favour automation, when do you remove the FD. Most aircraft use the FD for Windshear recovery which might infringe stick shake and then you inhibit valuable guidance.
Alternatively it should be possible to provide FD guidance for stall recovery, but would the effort of design, test, certification, not for all stall / upset scenarios, be cost effective if compared with efforts to avoid stall situations.

And as much as I favour spreading problem to a wider audience - management, regulator, manufacturer; action depends on their perception of the issue (or willingness to ‘see’), their view of safety priorities, or if there is a viable cost effective solution; so nothing happens.
On the other hand there may be great satisfaction in passing the problem on, being able to ‘blame’ someone else, “oh I told you so” after an event. cf 777 Asiana autothrust, 737 THY Rad Alt/autothrust, and as many examples as you wish to find or refute depending on your viewpoint.

“Wicked” problems can't be solved, but they can be tamed; how, recognise that there is a problem and be prepared to talk about it.



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Old 19th Jun 2018, 01:17
  #25 (permalink)  
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Originally Posted by vilas
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.
Manufacturer keep revising abnormal procedures in the light of new information. Even memory items have been revised time and again. Having conflicting information display is not good airmanship. If not PF, it may confuse the PM and trigger wrong callouts. We also have danger of mode reversion if we don't follow the FDs.
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Old 19th Jun 2018, 03:24
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Indigo
Does Airbus permits the operator to modify abnormal / emergency procedures?
you yourself just started and ended this thread. So what happened to your opinion now? Stall recovery is a memory item more serious than that. Nobody follows FDs in stall recovery but when exactly you switch them off? What is the priority. Why not check with the manufacturer first and let us know?

Last edited by vilas; 19th Jun 2018 at 05:14.
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Old 19th Jun 2018, 06:59
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INDIGO
We also have danger of mode reversion if we don't follow the FDs.
That is interesting. Since we are discussing stall we can only be in alternate law. So no hard protections which cannot be overridden and no auto pilot. ATHR may or not be there.Now let's see mode reversions. I assume you are referring to Speed protection when FD orders are not followed by the flight crew(AP NOT ENGAGED). In these protection there are two dimensions one is when the speed increases to VMAX+4 and the other is when speed decreases to VLS-2 or with speed brakes extended VLS-2 to VLS-19. Speed increase won't bother us because aircraft will not stall. If speed decreases below the value mentioned above then
FD bars disappear. If A/THR active, automatic engagement of SPEED mode on the A/THR. Thrust increases to recover the speed target.
So again no stall so where the danger that you see. Rather it is good. The very purpose of reversion is to prevent speed reduction below unsafe level.
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Old 19th Jun 2018, 13:55
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If you treat stall as an upset then in FCTM Upset Prevention and Recovery Nose High recovery it suggests disconnection of AP and ATHR.
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Old 19th Jun 2018, 14:26
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From a practical point of view, B737, the stall recovery manoeuvre would likely be prompted by the stick shaker. The response should be instinctive. The incipient stall would be broken PDQ. My concentration would be on that; i.e. attitude, speed then power. It would be pretty quick, even at altitude. I doubt I'd have the time to think about FD's or not.
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Old 21st Jun 2018, 03:07
  #30 (permalink)  
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Originally Posted by vilas
Indigo
you yourself just started and ended this thread. So what happened to your opinion now? Stall recovery is a memory item more serious than that. Nobody follows FDs in stall recovery but when exactly you switch them off? What is the priority. Why not check with the manufacturer first and let us know?
Stall recovery is a flying technique, not an ECAM drill or QRH/FCOM procedure.

Airbus golden rule says use appropriate level of automation and I consider FD as part of automation. In stall recovery, main action is lowering the nose. Afterward, it is about recovering the speed and flight path. At this time, if FDs give me conflicting information, I would ask for turning them off.
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Old 21st Jun 2018, 04:40
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Stall recovery is a flying technique, not an ECAM drill or QRH/FCOM procedure.
This can be a subject of a new thread. Stall is very much part of FCOM and QRH Abnormal Procedures. It is also a drill. Only difference is it is done by memory because life is too short. It is part of abnormal procedures in both the documents mentioned.

Last edited by vilas; 21st Jun 2018 at 07:51.
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Old 21st Jun 2018, 06:47
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Old 21st Jun 2018, 06:50
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This is from Flight Crew Techniqes Manual
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Old 21st Jun 2018, 10:39
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Good luck turning them of on the CSeries. They come on automatically at under-speed and you cant turn them off until you are recovered.
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Old 21st Jun 2018, 11:26
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Good luck turning them of on the CSeries. They come on automatically at under-speed and you cant turn them off until you are recovered.
And still the pilots fly without raising a hue and cry? Shall I call them brave?
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Old 21st Jun 2018, 11:37
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Originally Posted by FE Hoppy
Good luck turning them of on the CSeries. They come on automatically at under-speed and you cant turn them off until you are recovered.
So the only reason for that behaviour would be that the flight director actually gives useful cues to get back to speed. Sounds like a good feature for Airbus, kinda like a mental stick pusher for followers of the magenta line.
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Old 21st Jun 2018, 12:47
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Because pressing buttons on the FCU will save the day... xD. If you are stalling, first you would need new undearwear, then you better make sure the PF is reacting accordingly and as a PM, checking your FMA carefully and ready to take control as an incorrect corrective manoeuver will kill you. If you are worried about the FDs bar in a stall, it’s probably too late..Any onset of the stall in cruise shall be instintive and FDs ignored. Period.
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Old 21st Jun 2018, 21:07
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Personal take...

F/D's on/off during a stall recovery... In my book, whatever. As quoted above, you ignore them anyhow.

My issue is distracting the PM (essential part - right!) from the monitoring task during the recovery by asking for the FD's off. The PM simply isn't expecting it! Will take them by surprise and distract them from the key monitoring function.

Was it a fail though? Errrm, (IMHO) No way! Discussion item, but only if the examiner is feeling picky!
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Old 22nd Jun 2018, 01:37
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The PM simply isn't expecting it! Will take them by surprise and distract them from the key monitoring function.
Then he is going to get one hell of a surprise when something really serious happens on his watch if hasn't the cognitive capacity to switch off a FD switch in the one second it takes to do so. Jesus Wept. Has aviation got to the stage that we have to baby pilots that much, or are we so overwhelmed by the myriad of SOP's that are pushed down our throats in today's airline flying, that one slight item out of order is practically a Mayday situation?
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Old 22nd Jun 2018, 10:01
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Ok...Take this from the PF point of view...

Do you want them distracting themselves by looking at the FD, thinking of random rule number 17 and three quarters, thinking 'well I'm not following that so I must call for it to be turned off' (your myriad of SOP's...) or do you just want them to unload the wings using a simple tried and tested method and recover the aircraft.

ie. concentrating on the core task of recovering the aircraft in a time critical scenario.
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