Flight Director

[chrisbonfield]

Hi,

Just wondering what exactly the Flight Director does. Is it in any way similar to the autopilot??

Thanks,

Chris

[Lump Jockey]

I asked the same question a few weeks/months ago. So, try doing a search and hopefully you'll come up trumps. I got some good answers too!

[PifPaf]

Chris and Lump,

A Flight Director is a device that shows in your ADI (Attitude Director Indicator, or "artificial horizon") which attitude & heading you should follow.
In an ILS procedure, for instance, it will show how do you need to fly in order to stay on localizer and on glide slope. So, in a few words, the Flight Director directs your flight (simple this way!).
Roughly, in modern acft the FD replicates what the autopilot is doing. In older ones (like the 737-200, Sperry SP-77 autopilot), the FD and the AP are completely separate systems - and you need to place the same command twice: one for the autopilot, another for the Flight Director in order to check in your ADI if the acft is following what you intended to do.
I hope this simple, not very accurate explanation helps you.

Best regards,

Pif Paf

[john_tullamarine]

My comments only apply to the aircraft I have flown and/or their various simulator boxes (737-2/3/4 and 727-1/2). However I would suspect that the tale is similar for other equipment.

One of the problems I see often with newchums on an aircraft/simulator is that which follows on from slavishly trying to follow the FD "commands".

The FD computer is going to recognise a developing situation earlier than the pilot as it is monitoring voltages or whatever while the pilot has to see an instrument "error" after the event .. I don't think that anyone will dispute that position.

In turn, the FD computer provides a suggested course of action to correct the error and return the aircraft to the programmed state, whatever that might be.

If the pilot's basic I/F raw data skill level is high, then the ball will be somewhere reasonably close to the ideal and the FD will provide an early, SMALL correction suggestion which, if used by the pilot as no more than an extra bit of information in his scan, will permit an earlier correction to be made than would be the case flying only raw data. The overall result is to make an already smooth pilot even smoother.

The pilot who has little idea where either he or the ball should be and tries to follow the FD needles/bird ... ends up in all sorts of strife ...

Hence my emphasis on lots of raw data stick and rudder I/F during the early stages of endorsement training ... this is the only way to get the picture into the mind of the student ....

Just one chap's view of things ...

[411A]

In the earlier days when flight directors were rather new, watched in amasement as the v-bars on a Collins F/D commanded one way, while the ILS course was to the opposite.
Learned early on that sometimes....the flight director lies.

Found that the Sperry F/D display (crosspointers) was far less prone to errors than the Collins v-bar display....and not surprising, Sperry developed the first practical F/D, the zero reader. Nifty device, came standard on the DC6 with some airlines.