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TPI settings

Posted: Mon Apr 27, 2015 10:57 am
by vololiberista
Does anyone have a table or an extract, or a calculation method to determine the TPI setting?
Many thanks

Re: TPI settings

Posted: Fri May 01, 2015 9:50 am
by Jelle Hieminga
I'll have a look, it may be in one of the performance manuals. I'll see what I can do.

Re: TPI settings

Posted: Fri May 01, 2015 11:55 am
by vololiberista
Thanks Jelle

Re: TPI settings

Posted: Sat May 02, 2015 8:31 pm
by Jelle Hieminga
I found this in the old RAF Flight Reference Cards:
Image

Re: TPI settings

Posted: Sat May 02, 2015 8:44 pm
by Jelle Hieminga
And this one is from the W&B manual:
Image

Re: TPI settings

Posted: Sat May 02, 2015 10:04 pm
by vololiberista
Many Thanks Jelle,
The diagrams are extremely useful.
:P

Re: TPI settings

Posted: Thu May 07, 2015 1:51 pm
by vololiberista
Jelle,
I have another couple of questions relating to the diagrams (which have proved very useful, thanks). Are they for the Standard or Super? In the case of the Super one would assume that the tail fin tank would contribute to weight and balance. I'm looking for the moment arm for the fin tank in the Super variant.

Re: TPI settings

Posted: Thu May 07, 2015 4:28 pm
by Tonkenna
When I get a chance I will have a look in the Pilot/Nav Handbook and the Flt Eng Handbook for the ones we used day-to-day...

Andy

Re: TPI settings

Posted: Thu May 07, 2015 8:48 pm
by vololiberista
Thanks Tonks

Re: TPI settings

Posted: Thu May 07, 2015 8:57 pm
by Jelle Hieminga
vololiberista wrote:Are they for the Standard or Super? In the case of the Super one would assume that the tail fin tank would contribute to weight and balance. I'm looking for the moment arm for the fin tank in the Super variant.
These are both for the C Mk.1, so there is a fin tank in there... I'll have a look for a moment arm for you, but that will be for the same variant I'm afraid.

Edit: A full fin tank (4971 kg) has a lever arm of +548 inches (aft of trim datum). This moves to +494 inches with 800 kg of fuel in it and then moves back again to +518 inches when empty. This is based on the W&B manual from XV107 as I happen to have that lying about... I guess that you should be able to add the fuselage length increase (aft of the wing) for the Super to get the figures you need. I can scan the full graph if you want but it will have to wait a few days.

Re: TPI settings

Posted: Fri May 08, 2015 4:07 pm
by vololiberista
Thanks Jelle,
That's enough info to work on.
The only thing though is that the lever arm itself wouldn't change. The normal calculation would be lever arm x weight to give a moment. Do this for every station and then add them up dividing total moment by total weight giving the the lever arm from datum which would be CoG position.

Re: TPI settings

Posted: Sat May 09, 2015 5:57 pm
by Jelle Hieminga
Agree, but as the figures above are for a short body VC10 the lever arms would be longer in a Super fuselage. The same fuel loading in the fin tank of a Super would give you a larger moment when compared to the C Mk1 calculation.

Re: TPI settings

Posted: Sat May 09, 2015 7:52 pm
by vololiberista
Jelle Hieminga wrote:Agree, but as the figures above are for a short body VC10 the lever arms would be longer in a Super fuselage. The same fuel loading in the fin tank of a Super would give you a larger moment when compared to the C Mk1 calculation.
I've been playing with all the numbers using your Super VC10 loadsheet image and got exactly the same take-off TPI setting of 3.8 :o
But getting the equation for the slope was the difficult part so that + / - inches from datum converted from %MAC would give the right take-off setting.

Re: TPI settings

Posted: Sat May 09, 2015 9:47 pm
by Jelle Hieminga
Good to hear that you got it sorted! I did expect that a correction would be needed but if it works this way then I guess I was wrong.