Correct use of the Flight Director
Thread Starter
Correct use of the Flight Director
I am interested in hearing other people's flying techniques, particularly in regards to the flight director.
Are you just supposed to "blindly" follow the Flight Director and do whatever it says (place aircraft symbol in the middle of the cross hairs)
or
Do you set and adjust the aircraft attitude (pitch and bank) by reference to the raw data, using the Flight Director as a guide only ?
Are you just supposed to "blindly" follow the Flight Director and do whatever it says (place aircraft symbol in the middle of the cross hairs)
or
Do you set and adjust the aircraft attitude (pitch and bank) by reference to the raw data, using the Flight Director as a guide only ?
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During takeoff and initial climb I find myself often flying my known pitch values and planning ahead with regard to acceleration, climb rate aso. The FDs are naturally only reactionary, they cannot 'look ahead', often they react too slowly and then guide you to overreact to a deviation. On an FD approach though I was tought to fly the FD to the pixel (on our LCDs) while maintaining situational awareness of LOC, GS and speed deviations... Interested to hear more opinions 
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In that case I would suggest that you first confirm that your PFD is displaying the appropriate FD mode you wish to fly (HDG, ALT, APP etc), and then follow the bars, while at the same time monitoring the raw data.
Per Ardua ad Astraeus
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Most Ops Manuals I have seen say follow the FD if correctly programmed. Turn it off if you do not follow it or it is presenting incorrect information. There are some situations (take-off rotation, Windshear escape and a few others) where as STBYRUD says the FD will take a finite time to react.
Have you asked your Training Department? They will tell you what to do.
Have you asked your Training Department? They will tell you what to do.
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The flight director is a useful tool, but know when to follow it, and when to "fly through" it. Remember that the airplane is not the master and you the slave; it's the other way around.
Have you ever had a bad command from the flight director? Ever had one give you a sudden fly-down indication during an approach, or something else that you knew wasn't right, given the data you had before you and your own situational awareness?
The first rule always applies: fly the airplane. Use the flight director, but don't let it think for you. Remember that it's supposed to enhance your awareness, not be your brain. It's there to help you, not control you.
Have you ever had a bad command from the flight director? Ever had one give you a sudden fly-down indication during an approach, or something else that you knew wasn't right, given the data you had before you and your own situational awareness?
The first rule always applies: fly the airplane. Use the flight director, but don't let it think for you. Remember that it's supposed to enhance your awareness, not be your brain. It's there to help you, not control you.
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fly the airplane. Use the flight director, but don't let it think for you.
I recall flying a 737 to Guam in the Western Pacific and were radar vectored for an ILS as this was normal procedure for the military ATC. Weather was good with cloud patches on final. The first officer was flying and we had a new to our company but very experienced, former B747 Singapore Airlines captain on the jump seat. The aircraft was the 737-200 with FD 108 FD system. Not a bad FD for straight and level but in those days choice of FD use was left to the pilots. Mostly we never used it for an ILS.
The jump seat chappie was aghast when he realised the F/O was hand flying the raw data ILS and kept on muttering this was bloody dangerous. His whole life seemed to orbit around flight directors and he was genuinely concerned that the company he had just joined didn't use FD's or left it to the captain to decide.
That was over 25 years ago now and his obvious apprehension still stays with me. Having also in a past life conducted a fair bit of simulator training, I see similar scenes where even for visual circuits in the 737 Classic simulator, pilots use the flight director even though on many occasions they don't keep it programmed and one sees needles wandering aimlessly while the pilot rarely looks outside at the runway to check spacing. Others insist on leaving the FD with split cues using the pitch bar to maintain selected circuit altitude.
Raw data flying skills are soon eroded when pilots rely so heavily on FD usage. But that doesn't seem to worry some pilots who seem out of their depth without the FD as a crutch. Sad, really.
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By flying through, I don't think that people here mean doing something different, but not, for example, slavishly pitching up to +20 deg and then having to pitch down to +10 due to the sudden speed drop off, usually then commanding another pitch up as the speed rockets away. One would sensibly see that the FDs are overreacting and maintain smooth inputs to keep the speed stable. Another example would be executing a direct to in a turn with LNAV. One wouldn't just follow the inevitable FD zigzag, but point the aircraft for a sensible intercept and wait for the FD to come in.
What I have seen which I don't agree with, is the PF asking for VNAV an then upon seeing a TCU ahead holding the aircraft at Vx whilst the FD pitch bar descends way down there somewhere. Then I would agree, either select best angle, another mode or switch it off.
What I have seen which I don't agree with, is the PF asking for VNAV an then upon seeing a TCU ahead holding the aircraft at Vx whilst the FD pitch bar descends way down there somewhere. Then I would agree, either select best angle, another mode or switch it off.
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Use your instruments -- that's a PLURAL!
Scan the FD. Scan the other instruments. If they're all OK, then fly the FD. Scan again. If they're still OK, fly the FD; if not, adjust controls and power as needed.
REPEAT CONTINUOUSLY.
Scan the FD. Scan the other instruments. If they're all OK, then fly the FD. Scan again. If they're still OK, fly the FD; if not, adjust controls and power as needed.
REPEAT CONTINUOUSLY.
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An F/D is nice thing to have, but certainly not a required device in my book...if your leaning on the F/D for all things situational and navigational then it's best you make sure it's on and set up right...or off when not needed so it doesn't confuse you with an erroneous indication.
Psychophysiological entity
I used to dream of flight systems.
We were expected to follow the Zero Reader into a hole in the ground if it told us to. Worked with valves/tubes. As an ex telecoms tekki on valve equipment, nothing would make me follow that primitive pile of rotting rubber and glass anywhere. There just seemed more time to be aware of the total picture with basic ILS.
When finally I flew the Collins FD 108, I really thought it was quite good, but out of workness caused me to finally have the Smiths System catch up with me. Oh, my. I needed a brain transplant to cope with that.
We were expected to follow the Zero Reader into a hole in the ground if it told us to. Worked with valves/tubes. As an ex telecoms tekki on valve equipment, nothing would make me follow that primitive pile of rotting rubber and glass anywhere. There just seemed more time to be aware of the total picture with basic ILS.
When finally I flew the Collins FD 108, I really thought it was quite good, but out of workness caused me to finally have the Smiths System catch up with me. Oh, my. I needed a brain transplant to cope with that.
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The FD has to be understood as a pitch and bank target indicator.
It tells us which is the pitch and bank that should give us the desired performance.
Then we can achieve those targets either abruptly or smoothly.
FD do not give rate commands, only targets. The rate at which you reach them is yours to decide (within reason). Sometimes, a given target "expires" within seconds and is substituted by another, and you know it in advance so, you wait for the bar to come to you, instead of blindly following it.
Many "fresh" airline pilots tend to rotate too quicky in take off as an instinctive reaction to the pitch bar suddely going up to 15º. Or to bank at too high a rate because the roll bar went fully right after selecting a heading.
When the roll bar "goes" away, I then roll gently until the roll bar comes to me. The thing is more complex when reaching the target heading, though. Then it has some algorithm to resemble a rate command, I deem. If you follow quickly the bar, maybe you undershoot so the bar gives you a small bank for a while. If you are too slow, you will overshoot and the bar will go to the other side. In my airplane, I usually try to use always the same roll rate. Sometimes I note the degrees I turn from the begining till the end of the roll. Then I use that as the lead to go out of the turn and it works very well.
If you look at APs, they take their time to reach FD targets. Sometimes too much!
It tells us which is the pitch and bank that should give us the desired performance.
Then we can achieve those targets either abruptly or smoothly.
FD do not give rate commands, only targets. The rate at which you reach them is yours to decide (within reason). Sometimes, a given target "expires" within seconds and is substituted by another, and you know it in advance so, you wait for the bar to come to you, instead of blindly following it.
Many "fresh" airline pilots tend to rotate too quicky in take off as an instinctive reaction to the pitch bar suddely going up to 15º. Or to bank at too high a rate because the roll bar went fully right after selecting a heading.
When the roll bar "goes" away, I then roll gently until the roll bar comes to me. The thing is more complex when reaching the target heading, though. Then it has some algorithm to resemble a rate command, I deem. If you follow quickly the bar, maybe you undershoot so the bar gives you a small bank for a while. If you are too slow, you will overshoot and the bar will go to the other side. In my airplane, I usually try to use always the same roll rate. Sometimes I note the degrees I turn from the begining till the end of the roll. Then I use that as the lead to go out of the turn and it works very well.
If you look at APs, they take their time to reach FD targets. Sometimes too much!