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Old 08-03-2018, 07:16 PM   #11
BlacleyCole
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AreoGimp maybe take some videos using hero type cameras showing everything in real life hyena do the same virtually to show the differences
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Old 08-03-2018, 07:25 PM   #12
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Quote:
Originally Posted by Yo-Yo View Post
Henderson elevation is 760 m ASL, San-Diego - ?

So, we need to have all input parameters equal to have correct results.
With respect to manifold pressure I am not talking about on the ground, I am looking at airborne - 1,000M - 1,500M and Max Cont Power (82% RPM) which is my typical altitude and power setting for a formation sortie - my tired 1400 hour engine produces about 75 mmHg more MP than the DCS module, I need to bump the DCS Yak up to 90% RPM to get close.

The power issue is, IMO, a minor issue, the speed/yaw behavior is completely inaccurate, literally the opposite of reality.

I may not be able to login (mobile won't recognize my password) but if I can I'll continue while Wifey drives us to Big Bear and I 'work' on the laptop.

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Last edited by AcroGimp; 08-03-2018 at 09:05 PM.
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Old 08-03-2018, 07:33 PM   #13
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AcroGimp:

I've never flown a real Yak-52, but what surprises me is how much setting the prop pitch to fine decelerates the aircraft. Does it seem correct to you? Also, when I lower the flaps the plane pitches up, and I need to apply constant forward pressure on the stick, and I need a lot of power to maintain 160 kph even in a steep descent. Is that so in the real one too?

Finally, what trim settings do you use for takeoff/ landing?

Thanks a lot for sharing your experience, it's all very valuable info!
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Last edited by Reflected; 08-03-2018 at 08:20 PM.
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Old 08-03-2018, 08:07 PM   #14
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Quote:
Originally Posted by AcroGimp View Post
With respect to manifold pressure I am not talking about on the ground, I am looking at airborne - 1,000M - 1,500M and Max Cont Power (82% RPM) which is my typical altitude and power setting for a formation sortie - my tired 1400 hour engine produces about 75 mmHg more MP than the DCS module, I need to bump the DCS Yak up to 90% RPM to get close.

The power issue is, IMO, a minor issue, the speed/yaw behavior is completely inaccurate, literally the opposite of reality.

I may not be able to login (mobile won't recognize my password) but if I can I'll continue while Wifey drives us to Big Bear and I 'work' on the laptop.

'Gimp (DISCO vVMA-122)
It can not be opposite. If you take a look at the rudder trim position at these screenshots you can see that trim position goes right as the speed increases. Your plane is trimmed for the certain speed by adjustment of a trim tab on the rudder. Say, for 150 kp. So, take a look at the screenshots. You can see that you apply left rudder pressure then right rudder pressure. The problem is that in DCS Yak the trim tab on its rudder IS NOT DEFLECTED at all. Yak has no asymmetrical fin like the Mustang or Bf-109, so, geometrically it always has rudder deflected left, but as the trim tab trims the rudder for zero pedal force at the certain LEFT deflection you can say that you push left or right rudder depending on speed.
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Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів
There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.
Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me
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Old 08-03-2018, 08:28 PM   #15
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One thing that i feel is strange is the oil temp, from cold start it will never go into the yellow even but around 30-35c is max with full closed oil shutters? Cyl temp in the green.
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Old 08-03-2018, 08:36 PM   #16
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First off, there is no in-flight trimmable rudder on the Yak-52, it is a fixed tab so it is only ever truly 'in trim' at one speed. For most Yak's in the US this is set at 110 kts (~202 kph) because that is our typical formation sortie speed that gives us plenty of performance margin. The movement of the nose as speed/power change is caused by P-Factor and the slipstream effect.

As speed increases that fixed tab becomes less and less effective until such time as it is nowhere near enough and opposite rudder is required to remain coordinated - in EVERY Yak I have ever flown, significant RIGHT rudder is required to remain in/near coordinated flight above 250 kph, ALL of them, no exceptions - it is just like, but opposite, for EVERY Western aerobatic aircraft I have EVER flown (Citabria, Christen Eagle II, Glasiar I, RV-4, RV-6, RV-7, RV-8, Great Lakes, Extra 300L), which ALL require right rudder on takeoff but left rudder as speed exceeds that neutral rudder trim speed.

If DCS is not modelling P-Factor and Slipstream effects then that would explain it, but if it is modeling P-Factor and Slipstream effect then it is doing it wrong at-speed for this module, it is currently correct on the ground and during takeoff.slow speed flight based on observations so far.

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Old 08-03-2018, 09:06 PM   #17
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@Reflected, trim for takeoff with two aboard sees the trim tab on the left sidewall pointing down about 45 degrees as I recall.

The flaps are split flaps so pure drag, no lift, it requires a push on initial deployment but settles down pretty quick.

Rapid moves of the prop or throttle lever result in very noticeable changes for acceleration/deceleration - the blades are almost a foot wide and basically 8 feet from tip to tip, it is a giant speedbrake.

At mid-speed going from coarse to fine can actually result in acceleration depending on manifold pressure.

I don't use a lot of trim since most of my flying is all around the same speeds, I set takeoff trim, set once for a slight nose down condition when in formation or aerobatics since it lets me be more precise with my pitch inputs, and I don't re-trim after the break on the overhead, just make it do what I want down to the ground.

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Last edited by AcroGimp; 08-04-2018 at 12:59 AM.
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Old 08-03-2018, 09:15 PM   #18
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Quote:
Originally Posted by AcroGimp View Post
First off, there is no in-flight trimmable rudder on the Yak-52, it is a fixed tab so it is only ever truly 'in trim' at one speed. For most Yak's in the US this is set at 110 kts (~202 kph) because that is our typical formation sortie speed that gives us plenty of performance margin. The movement of the nose as speed/power change is caused by P-Factor and the slipstream effect.

As speed increases that fixed tab becomes less and less effective until such time as it is nowhere near enough and opposite rudder is required to remain coordinated - in EVERY Yak I have ever flown, significant RIGHT rudder is required to remain in/near coordinated flight above 250 kph, ALL of them, no exceptions - it is just like, but opposite, for EVERY Western aerobatic aircraft I have EVER flown (Citabria, Christen Eagle II, Glasiar I, RV-4, RV-6, RV-7, RV-8, Great Lakes, Extra 300L), which ALL require right rudder on takeoff but left rudder as speed exceeds that neutral rudder trim speed.

If DCS is not modelling P-Factor and Slipstream effects then that would explain it, but if it is modeling P-Factor and Slipstream effect then it is doing it wrong at-speed for this module, it is currently correct on the ground and during takeoff.slow speed flight based on observations so far.

'Gimp (DISCO vVMFA-122)
I have explained it above. The fixed trim tab in DCS Yak IS DEADLY NEUTRAL and can not be adjusted because of the bug. If it was adjusted for 200 kph you would apply RIGHT rudder at higher IAS.
I showed a tendency at the screenshots - less leftt rudder (POSITION!) as the IAS increases. If you apply a bias fixed trim tab gives you - you will apply RIGHT rudder as neutral point is passed.

Yellow arrow on the screenshots shows the possible NEUTRAL FORCE point. As the red tick showing rudder POSITION is at right from the arrow you would apply RIGHT RUDDER.
As the bug is fixed the aircraft will be factory trimmed at 200 kph, so you wil apply left or right rudder depending on speed.
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Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів
There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.
Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

Last edited by Yo-Yo; 08-03-2018 at 09:19 PM.
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Old 08-03-2018, 09:28 PM   #19
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I'll accept the terminology confusion on what you meant about 'trim position' and I see a slight reduction with respect to required rudder input in your screengrabs but if that is the case then the module does not require enough left rudder for slow speed because without the trim tab influence MORE left rudder would be required in real life. It felt close to right to me on takeoff/climbout but during a figure with big speed changes like a quarter-clover, loop, cuban-eight, etc., there is a massive change in rudder input throughout the figure in the real plane and that is not currently modelled correctly.

If you think the tab effect will correct that behavior then I am happy to wait for it to be implemented and revisit the issue.

I did note that during loops and quarter-clovers the speed bleeds off a little faster than real plane and I felt that the required left rudder during those phases was unrealistically low - so I suggest there may be more going on than just the tab not being effective, since that should have resulted in more left rudder being required, not less.

Thanks for replying.

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Old 08-03-2018, 09:34 PM   #20
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Edit: late post, I'll leave it anyway. Sorry for the redundancy.

Gimp - By way of attempting to help ease the language barrier, Yo-Yo is not disagreeing with the real-world effect you're referring to. It's true, as air load increases, level flight coordinated rudder direction usually reverses. However this is due to the fixed rudder trim tab (or other airframe design choices like canted thrust-line.) You probably already know this, but to alleviate any confusion, the fixed rudder trim tab is set to reduce left/right-turning tendencies of the airplane at cruise (or most commonly flown) airspeeds. This means the pilot needs less rudder inputs at speeds he usually flies. Of course, as airspeed increases beyond the set point, dynamic pressure on the trim tab increases, and it becomes too effective, resulting in the reversal of required rudder input.

What Yo-Yo is saying is that the DCS:Yak-52 currently does not implement the fixed trim tab in its early access state. Once that is implemented and adjusted for neutral rudder at 200kph, I think you'll find that the airplane will exhibit that reversal.

Great thread though, thank you for providing some Yak user insights. I hope threads like this can result in productive changes to the DCS Yak!
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