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Recycling The Flight Director  
User currently offlineLMML 14/32 From Malta, joined Jan 2001, 2565 posts, RR: 6
Posted (12 years 2 months 3 weeks 6 days 2 hours ago) and read 2556 times:

Why and when is it necessary to periodically recycle the flight director?

8 replies: All unread, jump to last
 
User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 2 months 3 weeks 6 days 2 hours ago) and read 2548 times:

Huh???

Sounds like an avionics problem to me.



User currently offlineLMML 14/32 From Malta, joined Jan 2001, 2565 posts, RR: 6
Reply 2, posted (12 years 2 months 3 weeks 6 days 2 hours ago) and read 2545 times:

To tell you the truth I have only seen this happen once in recent years. I was in the cockpit of a B733, glass cockpit, and one of the pilots decided to recycle both FD's as we were turning base (the pilot toggled the small switch on the MCP). I remember with the old B720's pilots used to do this quite often. Even several times in one flight. But I have never seen this happen on modern aircraft. I am now more curious than before.


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User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 2 months 3 weeks 6 days 1 hour ago) and read 2537 times:

I've been flying F/D equipped aircraft for nearly 25 years and EFIS equipped aircraft for 15 years and I'm not sure what you're talking about. (Obviously, I never had to do it.) We do have a button which we can press it clear the V-Bars from the display when they aren't wanted, but its use is purely a pilot preference issue. Is this what you're talking about?


User currently offlineLMML 14/32 From Malta, joined Jan 2001, 2565 posts, RR: 6
Reply 4, posted (12 years 2 months 3 weeks 6 days ago) and read 2526 times:

In the case of the B733 it is not a V-bar. There are cross hairs. But it's the same thing.

User currently offlineRick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 51
Reply 5, posted (12 years 2 months 3 weeks 6 days ago) and read 2524 times:

Sometimes the thing just goes wonky. Flippin the switch resets the flight director system and will do the trick 99% of the time.

Both switches must be switched off at the same time to re-cycle the system.

One thing that I just thought of is taxying out to the runway sometimes the F/D pitch command bar decides to stop indicating 8 degrees nose up, as it should in "TO" mode. The only way to clear the problem is switch both F/D switches OFF then return to ON again. This is for the 757/767 and is a known problem (documented procedure).

It's still quite rare though.



I used to love the smell of Jet-A in the morning...
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 6, posted (12 years 2 months 3 weeks 6 days ago) and read 2522 times:

I've heard of recycling a transponder (pull 1 CB) or an AHRS system (pull 2 CBs) but not a Flight Director. Not to say it can't be done though....

I wonder if you are talking about the vertical sync. Many flight director systems have a button that allows you to "reset" the vertical command to center.

Other than that the only thing I can think of is that the software in newer "digital" systems have the tendency to "go off into the weeds". The only way to get things straight again in these systems is to recycle the power or "re-rack" the black box.

Software in flight control systems including the flight director computer is typically very robust as compared to other less critical systems. The need for resetting is minimal.


User currently offlineLMML 14/32 From Malta, joined Jan 2001, 2565 posts, RR: 6
Reply 7, posted (12 years 2 months 3 weeks 5 days 23 hours ago) and read 2522 times:

Both FD switches where recycled, like Rick767 said. The funny thing is that the pilots had planned for this recycling during descent. It could therefore be a known fault on that particular aircraft.



User currently offlineRick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 51
Reply 8, posted (12 years 2 months 3 weeks 5 days 23 hours ago) and read 2520 times:

LMML,

This is not a 733 procedure that I am aware of, so yes it sounds like a known fault on that aircraft.



I used to love the smell of Jet-A in the morning...
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