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P-51D stall and spin: make it milder at takeoff and landing  Topic is solved

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Re: P-51D stall and spin: make it milder at takeoff and land

Postby OK-F » Tue Apr 10, 2018 10:35 pm

True is the FG P 51 is more wild and difficult then the real beast at take off. But still you can learn it and it's possible to make a nice take off. I don't see any problem in the air and landing is no problemo after a few attempts. So the question is do we want to make it closer to the real plane and therefore easier at take off? For me it would probably no because I now have a great fun with the plane and learn how to take off right was rewarding for me.

I would probably stick to the TODO list and finish the other things.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby swampthing » Tue Apr 10, 2018 11:06 pm

I would say yes. I don't have a problem landing its the problems it gives at take off. I think its worth the time to fix this instead of trying to figure out a way to make it take off and then post that. I haven't tried what Dany93 posted yet so maybe there has been a fix.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby OK-F » Wed Apr 11, 2018 1:32 am

Sure important is what most people think about it. And if it helps the plane so that people will fly it again then 100%
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Wed Apr 11, 2018 8:46 am

swampthing wrote in Tue Apr 10, 2018 11:06 pm:I haven't tried what Dany93 posted yet so maybe there has been a fix.

It is not truly a fix, the roll tendency due to propeller torque is still there, you still have to be careful at throttle increasing. But I think it improves the controllability for when the beast tends to flip you if you are too quick at pushing the handle.

I think that the critical step is when the aircraft starts flying, the weight moment becomes not enough for holding both wheels on the ground, and at the same time the ailerons are not yet efficient enough to counteract the roll tendency. Between about 100 and 130 MPH.
On this Kermie Cam video, by observing the stick movements, you can see a small and temporary rightwards correction at 0:31". At 90 - 100 MPH speed, just before pulling the yoke for taking off. Noticeable coincidence...

This change in the file is very simple, with no degradation at my current knowledge. IMHO, justified with no doubtful compromise.

If you find a better way (still with no degradation, justified by realistic arguments, as much as possible not a cheating).... :D
Last edited by dany93 on Wed Apr 11, 2018 10:30 pm, edited 3 times in total.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Wed Apr 11, 2018 10:34 am

In DCS: P-51D Mustang Flight Manual (English) p. 132 / 188 PDF, I read:
it is recommended that 61 in.Hg and 3000 RPM be used for takeoffs and that this power setting is reached as quickly as possible after the takeoff run is started.
However, advance the throttle smoothly and never jam it forward. Torque effects appearing from a sudden onset of power can lead to a loss of directional control of the aircraft

'61 in.Hg and 3000 RPM be used for takeoffs and that this power setting is reached as quickly as possible after the takeoff run is started',
like we can read elsewhere...
but
'However, advance the throttle smoothly and never jam it forward. Torque effects appearing from a sudden onset of power can lead to a loss of directional control of the aircraf'

This is a simulator site, for what it's worth, however (p. 2),
The contents of this manual are based largely on actual vintage P-51D manuals of the aircraft’s service era.

Our FG P51D is probably a bit hard at takeoff, but these precautions against the torque effect seem recommended in the real one too.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby wkitty42 » Wed Apr 11, 2018 3:07 pm

OK-F wrote in Tue Apr 10, 2018 10:35 pm:So the question is do we want to make it closer to the real plane and therefore easier at take off?

of course it should be made closer to the real craft... FG is a simulator of real life aircraft physics...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby OK-F » Thu Apr 12, 2018 12:09 am

wkitty42 wrote in Wed Apr 11, 2018 3:07 pm:
OK-F wrote in Tue Apr 10, 2018 10:35 pm:So the question is do we want to make it closer to the real plane and therefore easier at take off?

of course it should be made closer to the real craft... FG is a simulator of real life aircraft physics...


I admit it was not the best submission. I got little winded off.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby wkitty42 » Thu Apr 12, 2018 12:13 pm

hehehehe, it is ok, OK ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby LesterBoffo » Fri Apr 13, 2018 4:31 am

My Dad was a chemist and construction engineer with Allied Petroleum in El Segundo, CA during WWII. They were neighbors with North American Aircraft during the time the XP51 and first P-51A's were being flight tested, before being sent off to the UK.

The P51A had a one gear stage driven supercharger equipped Allison V-1710 aero engine of about 1170 h.p. and a slightly smaller 3 blade Hamilton constant speed propeller. My Dad and a lot of his co-workers got to watch the first flights of the XP-51 and P51A, and his impression was it seemed to have an issue with the transition from the tail gear being down, to up nearly level AoA on the mains and gaining enough speed to take off. There was a particularly nasty nose over with one during taxi testing that nearly grounded the whole testing group, until it was discovered that the brakes were really sensitive and one of their test-pilots had inadvertently activated the foot brakes ( on the rudder pedals, rotating the pedals forward activated the brakes...) while still taxiing fast enough to flip it onto the nose. The P51A despite being lighter than the later B, C, and D models, still had a relatively high wing loading, and consequently a higher takeoff and landing speed than any previous US pursuit plane. The wing also tended to blank some of the airflow over the elevator until it was rolling fast enough while taking off. Which made elevator control sort of 'notchy' while gaining speed above 50 knots. Keeping the stick back was twofold, you locked the tail wheel with the stick fully back, and kept the tailwheel on the ground until there was sufficient airflow to help fight the P-effect which wasn't as bad on the Allison with it's 3 bladed propeller. Dad had a friend who was working at NAA, who was pretty excited about what they had achieved with the Mustang, but it still had a lot of teething issues and the really demanding takeoff and landing skillsets didn't help.

Did you know that the P-51A and Mark1's were the longest serving RAF fighters of WWII? They had such a huge speed advantage at low altitudes, that they were faster up to 9000' than the Merlin equipped Mustangs and the later Hawker Typhoon and Tempest. And were used from their first deployment for a lot of cross channel, low altitude ground attacks, observation runs, and general low altitude escort fighter roles right up the the end of the European WWII theatre operations. That was from summer1942 to nearly spring of 1945.

The other interesting note from the XP51 project was that the first North American Jet prototype, the FJ-1 Fury used the same laminar flow airfoil and similar wing outline (strengthened of course) as the P51.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Fri Apr 13, 2018 10:18 am

Thank you, LesterBoffo for these extra informations. The kind of descriptions that you don't encounter easily at random search.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Sat Apr 14, 2018 3:09 pm

The parking brake has a sophisticated logic, not straightforward. (thumbs up to onox for having coded it!)
To understand it, read the "PARKING BRAKE INSTRUCTIONS" placard just above the parking brake handle.
Also, the on-screen indications are here to help.

An issue is when we use the "Autostart". The parking brake is armed (handle is pulled), but not active.
To make it active:
- fully depress the (pedal) brakes (or b key).
To release it:
- release the parking brake handle (or shift-B),
- depress the (pedal) brakes (or b key).
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby swampthing » Sun Apr 15, 2018 3:32 am

Key bound to my stick. Keeps me out of it.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Sun Apr 15, 2018 12:38 pm

Are you sure?
If your JS sends the same command lines as the keyboard "b" and "Shift-B" do in FG (which is what your JS should do, to work on every aircraft) there should be no difference. Or am I missing something?
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby swampthing » Mon Apr 16, 2018 8:03 am

No I have b bound to my stick and when I press it the parking brake turns on, so it makes it kind of of a struggle when I get ready to taxi or take off because I hit the button on my stick it pops up on my screen that I've turned the parking brake on as if i actually did hit shift B. It doesn't happen on any other plane. Its left me confused as to why it does but I haven't looked at the set file either. I haven't manually started it yet to see if it does the same thing but I don't see why it wouldn't. Even if you click magic start you would think it would start with the parking brake on anyway so people don't get the surprise of there plane rolling away. ;) I'll have to talk to onox more about it to see why its doing this.
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Re: P-51D stall and spin: make it milder at takeoff and land

Postby dany93 » Mon Apr 16, 2018 8:56 am

Your JS has its button (like the "b" key) bound for normal (temporary when depressed) brakes, do I understand well? This is the common setting.

Can you try this:
1- Autostart the engine,
2- On your keyboard (b) or by your JS button depress the (normal) brakes (for a not too short time, and release it),
==> The parking brake should be ON.
3- On your keyboard (Shift-B) or by clicking on the dashboard handle, release the parking brake handle.
==> The parking brake should still be ON.
4- On your keyboard (b) or by your JS button depress the (normal) brakes (then release it).
==> The parking brake should be OFF and brake controls (b or JS button) should work as normal brakes.

This procedure fits the real one (dashboard indications).
The only thing with the parking brake is if one uses Autostart to restart the engine in flight. If the parking brake setting is "Armed" (pulled) and waiting for brakes depress as currently, or "ON", pressing the brakes activates it. Unless a "condition" would be added. Like for every aircraft with Autostart and parking brake ON.

With manual start, the parking brake should be OFF at launching, and remain OFF.
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