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Flight Dynamic problem

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jimos87 View Drop Down
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    Posted: 30 Nov 2017 at 10:56am
Is anyone else expeireinng issues with autopilot alt hold moving up /down by 2000  fpm when its supposed to be level flight. This is the 2nd time ive reinstalled now and the issue is still there on P3 V4.  I had to give up on my inaugral flight today because of this issue. Also the AT does not engage when i turn on AT power.
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Martyn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martyn Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 11:31am
Are you trimming out the aircraft before engaging altitude hold mode? In the real aircraft the altitude hold mode is designed to be engaged once the desired altitude has been reached and the aircraft trimmed out for level flight, however we've included a vertical speed mode for convenience.

Have you engaged airspeed hold mode using the IAS switch after switching on the autothrottle power and selecting the desired airspeed?

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Martyn
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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:07pm
Further to Martyn's comment, initial rate of climb is under 2,000fpm for the standard so you should definitely be climbing at or below that rate before engaging the AP. Lightly loaded, it will climb faster - I have just flown a light and steep climb-out at a touch under 4,000fpm and set the Alt hold to 5,000ft. At that rate of climb, it did take a couple of cycles but captured the altitude. I then set it to a 2,000fpm climb and it captured 8,000ft perfectly.

At higher altitudes, your RoC will be lower and there should be no issues capturing an altitude.

Cheers,
Paul.
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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:07pm
Airspeed was engaged as per the tutorial flight, The Alt hold system set the V/S  to 0 but the pitch trim automatically moves by itself. I tried to centre it manually and turn Alt hold back on but it just did the same thing. on the very first flight I did it was fine there was just the speed dial bug which I also reported. 
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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:08pm
My rate of climb is default at 1800 fpm thats set by the AC config 
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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:13pm
The pitch trim needle moving is a side-effect of the default FSX / P3D AP system, which uses trim rather than elevator to control pitch. With most aircraft it's not seen, but with the VC10 you have a great big instrument there to show you! Don't try fighting it, unfortunately it is doing what FS needs it to do.
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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:19pm
Thats irelevent becuase it is literally doing what its showing me its doing which is not right
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Martyn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martyn Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:25pm
This is something which is probably best discussed directly with our support team as the autopilot/autothrottle is working fine here, so this will require some investigation. If you haven't done so already, please submit a support ticket via the website and our support team will look into this.

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Martyn
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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:26pm
https://www.dropbox.com/s/b2qdvj0t5jjv98y/Video%2030-11-2017%2010-17-56.avi?dl=0

Watch here you can see it going up and down. IDK why the sound is doing that i think i had the recorder on the wrong setting
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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:26pm
I have they told me to come and read my own post.
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Martyn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martyn Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:27pm
OK. They will be in touch again shortly. Apologies for the confusion.

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jimos87 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jimos87 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:39pm
I will record a video of the issue from start to finish to assist
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Martyn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martyn Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 12:56pm
Thanks. Please send that to Craig so he can continue his investigation.

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petesmiffy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote petesmiffy Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 7:41pm
I have had no problem withe A/P in climb or altitude hold after the initial climb.
However, if I change altitude and try to re-engage altitude hold the aircraft begins to wobble about 150 - 200 feet either side of the selected altitude. Enough to have the passenger reaching in the seat pocket for the paper bags.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Debowing Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2017 at 7:48pm
I think that the AP needs a bit of getting used to, I had similar issues but I believe these are due to my poor VC 10 piloting skills.
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Lord Nibbo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lord Nibbo Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2017 at 10:51am

I think the flight model needs a lot of attention.

Try flying at FL 10000 on auto pilot with auto throttle on doing 250 knots now do a 90deg turn and then tell me what happens to you?  I suggest this should not happen.

Try an ILS approach  starting at about 160 knots and about 30 deg  off the ILS feather. Slow aircraft before glide slope is attained to approximately 135/140 knots now try adding flaps ( suggest only 19  deg)  I’ll bet your airplane is nose down too high  too fast and no way will you land on your back wheels before the front wheels. 

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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2017 at 11:58am
Originally posted by Lord Nibbo Lord Nibbo wrote:

I think the flight model needs a lot of attention.



Some specifics - the flaps create large pitching moments which need to be trimmed out: from up to T/O creates a nose-up pitch initially, which you start to trim out but then (combined with the drag and speed reduction) towards the end of the movement it becomes nose down, so you have to reverse the trimming. That's over a time period of roughly 15 seconds. Moving from T/O to Approach or Land is similar to many other heavy jets and gives a strong nose-down pitch, again exacerbated by the deceleration, which you need to trim out. That is straight from a VC10 pilot who is on the testing team and is happy with the reaction of the aircraft.

The problem you are seeing is not a flight model problem, but specifically an Autopilot problem: The AP (default FS) uses pitch trim to control pitch, rather than the elevator. Hopefully you can see the start of the problem - if the AP has taken over the pitch trim, how can you trim out the significant pitching motion caused by flap deployment?

Then you move forwards to the speed of capture of certain elements - altitudes, glide slopes etc. Because the VC10 has an all-moving tailplane for trim and seperate elevators for pitch control, the trim in terms of degrees moved is less than you may expect. It is also slower in its reaction, hence the roughly 30 ft either side of selected altitude during the turn and then the overshoot by a couple of hundred feet on wings-level at the end of the turn.

The 'simple' answer is to build a completely custom autopilot (that would be a few weeks' worth of work for whoever gets to code it!) which uses the elevator rather than trim to control pitch. Meantime, I'll keep plugging away to get more acceptable results from the default system which only really works with aircraft that run on rails and have no significant 'quirks'LOL

I don't think full autoland is implimented in this version, either - if you set up to capture the glideslope correctly (from below, 'sensible' angle off) and are in the correct configuration already, it will fly you down the glideslope and put the mains on the ground first. A heavy landing as there is no flare, but it will put you there!

Cheers,
Paul.
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Martyn View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martyn Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2017 at 12:44pm
Flare mode is partially simulated but not fully and it is largely reliant on the standard ILS approach mode. With FLARE selected on the autopilot mode selector, the aircraft will pitch up and the throttle will move to idle as you approach the runway.

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Lord Nibbo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lord Nibbo Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2017 at 2:43pm
Originally posted by Martyn Martyn wrote:

Flare mode is partially simulated but not fully and it is largely reliant on the standard ILS approach mode. With FLARE selected on the autopilot mode selector, the aircraft will pitch up and the throttle will move to idle as you approach the runway.

Thanks
MArtyn
Ah! that will help a lot, thanks for the tip.

edited..... Yes with the Flare mode selected it is much more realistic, thanks again Martyn
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hriches2 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 2017 at 6:55pm
And for anyone new do I set the trim to 0 at climb and how would you trim the aircaft for landing without overdoing the trim. New to the trim situation and sorry for the begginers comment. Great if you could explain trimming the VC-10 in more detail for all starters.

Thanks
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