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VC10 project under way - any interest?

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Re: VC10 project under way - any interest?

Postby zakalawe » Sun Jan 24, 2021 4:31 pm

Alant wrote in Sat Jan 23, 2021 7:05 pm:Thanks for the comments. I will make a post when I make the next FDM update.


It sounds like you've got things in hand, I shall look forward to an update but no pressure, I have enough other things to keep me occupied.
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Re: VC10 project under way - any interest?

Postby Honzaku » Tue Jan 26, 2021 12:58 am

Alant wrote in Sat Jan 23, 2021 7:05 pm:Yes, I saw similar things. Yuk . I think what you were seeing was a spiral mode instability which built up to a level that the aileron could not control. Also the spoilers are not yet simulated. They add about 50% to the aileron roll power.

The present Datcom version (not pushed to git yet) also has a mildly divergent dutch roll. As with most swept wing airliners the VC10 has a full time yaw damper, which is not yet simulated. Without the yaw damper the pilot needs to be practiced in controlling dutch rolls with the rudder pedals. This is OK for a test pilot but not for the average airline piilot. The passengers would probably complain and/or be airsick also.

I spent most of my time last week making reset-in-air work without the engines cutting out. That done
I can now launch at any flight condition.

This bought up the pitch trim startup problem that I mentioned in the previous post as there is insufficient pitch trim authority at speeds over 250 kt, and the JSBSim trim algorithm gives up .

As Datcom does not allow me to simulate the effect of the 4 rear mounted engines in their nacelles this may be a contributary factor. These engines will act like a second horizontal tailplane, adding to the pitch stability.

The basic VSPAero VC10 setup is now complete, so I will soon have an alternate set of aero data to compare against. VSPAero also allows me to add the engine nacelles and the bullet fairing at the top of the T tail, but for now I will be comparing against my Datcom model.

Thanks for the comments. I will make a post when I make the next FDM update.

Alan

Hi Alan,
Maybe it is silly idea, but how about to try contact some company archives and kindly ask them to see at least basic lift and drag curves to have some starting point rather then reinventing wheel. They probably say "No", but asking worth nothing. On the other hand VC-10 is dead at all in real life - all airplanes are retired, has no simmilar succesors, nearly 60 years old design is outdated, so from comercial and military point of view these data is worthless. So, unless there is some legal problem like all military crafts must be keep secret at least 50 years after its retirement or so, there is no real reason to keep this data anxiously secret anymore, I think...
Best regards and good luck with your great project!
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Re: VC10 project under way - any interest?

Postby Alant » Tue Jan 26, 2021 11:50 am

Honza, thanks.
In normal times I would have good access to the company archives. Last time I went into them (for TSR2 data) the former VC10 Chief Aerodynamicist helped me find my way around the filing cabinets. It helped that I knew him, as, although I was in a different Department, I worked on or two of his projects back in the day. However I am now retired and living in Portugal, and I would not dream of asking him to go into the archives with the present situation., especially as he is a few years older than I am.
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Re: VC10 project under way - any interest?

Postby Honzaku » Tue Jan 26, 2021 6:45 pm

Ah, I see. Yes, it is wise decision to stay at home as much as possible and play with DATCOM in these days. We have to hope it will be better soon and we will be able to come back to our normal lives...but it is getting to be a bit too long for now. Anyway it is great that it is kind of possible to get original data, so you can eventually improve your model anytime in future if situation let you do it.
Take care.
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Re: VC10 project under way - any interest?

Postby Alant » Tue Feb 02, 2021 11:42 pm

I have pushed an update which improves the pitch trim.
Here is a summary of my experiments.
The first attempt was involved setting up an aero model using OpenVSP. The result similar to that produced by Datcom, which although not solving the problem was a good cross-check.
Next I added engine nacelles to the OpenVSP model. There was a small improvement. Replacing the nacelles by an equivalent tailplane produced a larger effect, but still not enough.
Today I tried a different approach which was to change the airfoil section. First in OpenVSP and then in Datcom. The VC10 was a pioneer in using super critical airfoil sections. These aim to control the airflow at high subsonic Mach numbers. For a short explanation and some pictures see https://www.vc10.net/Technical/wing_shapes.html.
My first attempt produced the desired effect so I have pushed it to GitHub. With this airfoil at the c.g. that I am using for test flights, the tail trim is 2.5 deg nose up, instead of -2 deg nose down, which is very close to the limit of tailplane movement.
I want to get about 6 degrees nose up tail trim with this c.g., so next I will experiment with some airfoils with different camber.
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Re: VC10 project under way - any interest?

Postby zakalawe » Wed Feb 03, 2021 12:21 pm

Alant wrote in Tue Feb 02, 2021 11:42 pm:My first attempt produced the desired effect so I have pushed it to GitHub. With this airfoil at the c.g. that I am using for test flights, the tail trim is 2.5 deg nose up, instead of -2 deg nose down, which is very close to the limit of tailplane movement.
I want to get about 6 degrees nose up tail trim with this c.g., so next I will experiment with some airfoils with different camber.


That sounds excellent, and a much more comfortable amount of trim than before. I'll give the current state a play tonight, but I doubt my limited aeronautical skills can inform anything you aren't well aware of :)
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Re: VC10 project under way - any interest?

Postby Ysop » Sun Feb 07, 2021 4:07 pm

Any interest? - definitely yes!
Flightgear is just not complete without an aircraft from the era, when jets dared to look different.
And excellent read, how the prototype has been improved.

You will not need any help for the FDM, so there is not much, what I can do. But definitely thumbs up for this project!

What was your approach for an "equivalent tailplane" for the nacelles?
The Citation has a somewhat similar layout and in the OpenVSP-model the nacelles are open tubes. As there are some assumptions taken for the inside walls and also the pylons, apart from the problem of the airflow being entirely different due to engine running, this approach might not perfect.
Viewed from above similar projected area and axis along thrust axis?
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Re: VC10 project under way - any interest?

Postby Alant » Sun Feb 07, 2021 11:17 pm

The equivalent tailplane is just a tailplane of similar area to the nacelles. It has no camber and is set at 3 deg incidence to match the engines. I tried using OpenVSP nacelles, but they produced little effect. I don´t think that OpenVSP can do much with the flow through the nacelles . Perhaps we should ask on their forum -https://groups.google.com/g/openvsp. They usually respond very quickly.
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Re: VC10 project under way - any interest?

Postby Ysop » Mon Feb 08, 2021 8:13 pm

Definitely very friendly replies in that forum. (Well, just like here.)

Found two relevant posts:
https://groups.google.com/forum/embed/? ... nUuPM-BwAJ

https://groups.google.com/forum/embed/? ... o92IzXEgAJ

Looks like creating a "tube" is already the way to go without worrying too much about real airflow. There is also a chapter "adding nacelles" in ground school.

Maybe It is worth trying just for comparison both vertical and horizontal equivalent plane. At least in my case there must be quite an effect on yaw axis.
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Re: VC10 project under way - any interest?

Postby Alant » Tue Feb 09, 2021 9:08 pm

Thanks to Warty and N-SCOT we now have a BOAC livery. I have got rid of the 707 thumbnail that was displayed in the launcher, and in it´s place we now have the VC10 flying low over Brooklands where she was built.
That done it s back to the FDM work.
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Re: VC10 project under way - any interest?

Postby zakalawe » Sun Feb 21, 2021 3:22 pm

The new updates look nice indeed, especially the BOAC livery.

I managed more of a circuit in a recent test flight. My perception is that when I lowered the flaps, the roll instability became a problem: I did a very generous-sized pattern, and managed two 180-degree turns with flaps up. (Being gentle with my aileron inputs) When I dropped first notch of flaps, and then tried to align with the runway heading, I ended up at extreme / uncontrollable bank angles within fifteen seconds. Apologies as usual if this is already known and understood.
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Re: VC10 project under way - any interest?

Postby Alant » Sun Feb 21, 2021 11:33 pm

Thanks for the report. Don´t worry about reporting problems. Ask James on the devel list - he puts up with a lot, as I sure you know. ;)

Yes, unfortunately the handling has major problems at the moment.

With limited resources I am currently working on the autopilot controllers to enable autopilot work to progress more easily.
I have a flexible reset-in-air working which is needed for repeatable flight tests. This facility is often spoken about here, but hardly ever implemented. The "can´t be done" school is currently winning the discussion. ;) It does require attention to aircraft system initiation. Also the fuel and loading dialog now shows c.g. position as well as weight, which is needed for the same reason.

I clocked up many hours flying VC10 back in the day whilst running the simulator at Weybridge. Most of this was on flying instrument approaches, so I am also working on the cockpit instruments.

The aim is to get this simulation as docile as the ones I made and checked out in the 1970´s. The big difference is that then I had the aero department behind me providing data as required, and I had to make the results acceptable by the company test pilots, who were flying the production aircraft daily.

Keep safe

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Re: VC10 project under way - any interest?

Postby AN 225-100 » Tue Feb 06, 2024 4:28 pm

How do you start the VC10? But what to press? When the car starts, a seemingly endless startup process begins, but the engines still don't
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Re: VC10 project under way - any interest?

Postby Alant » Tue Feb 06, 2024 4:34 pm

Select the menu "Vickers VC10" , and then "Autostart/shutdown". The engines start in sequence after a minute or 2. There are other checks that have to be done first. Wait until all 4 are started. ;)
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Re: VC10 project under way - any interest?

Postby AN 225-100 » Tue Feb 06, 2024 5:11 pm

I did it, but they still don't start even after 4 minutes
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