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P-51 High Speed Elevator Response Incorrectly Modeled


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VBF-12_KW

My assertion here is that the P-51's elevator response at high speed is incorrect.  I've posted about this before but since the devs are now working on the P-51B which will likely have these identical issues due to the similarity of the planes, its a good time to bring this up again.

 

Currently in game, as airspeed increases past around 485mph in a dive, the aircraft becomes unrecoverable with elevator alone, and significant elevator trim (sometimes full nose up) is required to recover the aircraft.  This is incorrect, as shown by the following sources:

 

RAF dive test of the Mustang IV : "Recovery Technique.- Recovery in any case must be gradual and executed with extreme caution since relatively light elevator stick forces or rapid application of trim may very easily result in the application of excessive load factors. As acceleration is applied at the beginning of the pull-out some increase in vibration may occur. This will gradually decrease as the recovery is completed. In no case is elevator trim necessary to aid recovery."

 

P-51 Pilots Operating Instructions from 1944 : "The use of elevator tabs is not required for dive recovery because of the low elevator control forces."  (from page 24, section 21 - Diving)

 

From the 1954 F-51D Flight Handbook: "Reduce power and pull up very gradually, taking care not to exceed 4G except in emergencies.  If a pull-out above 4G is necessary, as G increases, relax pull force on stick.  The elevator trim tab is not normally required to aid recovery.  In the event it is necessary, use with extreme care and feed in gradually.  WARNING  Care should be taken in pull-outs above 4G, as the stick forces are relatively light, and an abrupt pull-out may cause rapid uncontrolled increase in G."

 

As seen from these reports and manuals, in the real aircraft the danger in dive recovery was too much elevator authority, rather then the complete lack of it that we have in game.

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LColony_Red_Comet

You beat me to it. 

 

I totally agree that this is completely modeled wrong. The in game behavior isnt just wrong, its practically the opposite of what all the manuals state. As you pointed out, the real concern in the P-51 should be that you have "too much" control authority available. 

Edited by [TLC]MasterPooner
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Gavrick

Firstly, when you diving at high speed, you should not forget about the effect of compressibility. In this case, it is not speed that matters, but the Mach number. On the left side of cockpit there is a plackard with a speed limit depending on the height. You say that the 485 mph plane is poorly controlled. So, but above 5000 feet it is forbidden speed. One of the effects of compressibility is a drop of aerodynamic control surfaces efficiency. That is why they write that it is useless to use a trimmer - with a large M number, the elevator or aileron itself loses effectiveness.
Further. Suppose we have a speed of 485 miles per hour near the ground. At the same time, when 50% of fuel, we can make about 4g, and this is a lot, considering the speed, and the fact that there is no getting away from the “stiffing” of the control - for example, in the same dive report it is stated that the stick force is “relatively” light in dive. And if you reset the trimmer to neutral, it will be 5g near ground at 485 mph. And at 400 miles per hour, we have 8g on the ground level with a trimmer in neutral, and we can get even more if we help with a trimmer - 10+ g. And 400 miles per hour is also pretty much speed...
And finally. It should be noted that in the 44th year there was a modification of the control system. A "bobweight" was mounted on the stick. Without its installation, indeed the stick was too light, and at the same time there was a danger of easily exceeding the overload restrictions.

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VBF-12_KW

Thanks for taking the time to read my post and discuss this!

 

485mph at 5000ft on a standard day (I was just playing around with this on Kuban autumn) is about Mach .69 - pretty low for compressibility.

 

They are clearly not writing about a loss of trim or elevator effectiveness:

 

"rapid application of trim may very easily result in the application of excessive load factors"

 

"The elevator trim tab is not normally required to aid recovery.  In the event it is necessary, use with extreme care and feed in gradually.  WARNING  Care should be taken in pull-outs above 4G, as the stick forces are relatively light, and an abrupt pull-out may cause rapid uncontrolled increase in G."

 

While I understand that the controls of any aircraft using rods or cables without hydraulic boost will stiffen as speed increases, all the sources are very clear that the pilot needs to be very cautious pulling out of dives to not over G the aircraft and pilot.  In game this is almost never a problem - only when you get to near full trim and full stick as the speed falls off can you start to black out.  The issue is always that you need to apply full back elevator and start dialing in trim aggressively to make a recovery - exactly what the manuals tell you NOT to do!

 

I think this may all be related to the bulging observed in the fabric elevators at high speeds changing the shape of the control surface.  When they switched to a metal elevator in the very late aircraft they had to change the angle of incidence of the horizontal stabilizer to compensate. 

 

From America's Hundred Thousand by Francis Dean: "On the P-51D-30 airplane, and as a modification to other P-51D aircraft metal covered elevators were installed to improve high speed flying qualities.  Since the metal covered elevators did not bulge, the normal tendency was for the aircraft to become increasingly nose heavy at very high speeds, and to compensate for this undesirable characteristic, most noticeable at high altitudes, the incidence setting of the horizontal stabilizer was decreased from the one and a half degrees nose up to only on half degree nose up, done at the same time as the change to metal covered elevators.  Without the incidence change of the stabilizer the pilot would have observed a sharp pitch forward of the airplane, and a sharp reversal of control forces from push to pull as the high speed placard limits were reached."

 

Anyway, thanks again for your time!  We all really appreciate the work you guys put in.

 

 

 

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LColony_Red_Comet
12 hours ago, Gavrick said:

Firstly, when you diving at high speed, you should not forget about the effect of compressibility. In this case, it is not speed that matters, but the Mach number. On the left side of cockpit there is a plackard with a speed limit depending on the height. You say that the 485 mph plane is poorly controlled. So, but above 5000 feet it is forbidden speed. One of the effects of compressibility is a drop of aerodynamic control surfaces efficiency. That is why they write that it is useless to use a trimmer - with a large M number, the elevator or aileron itself loses effectiveness.
Further. Suppose we have a speed of 485 miles per hour near the ground. At the same time, when 50% of fuel, we can make about 4g, and this is a lot, considering the speed, and the fact that there is no getting away from the “stiffing” of the control - for example, in the same dive report it is stated that the stick force is “relatively” light in dive. And if you reset the trimmer to neutral, it will be 5g near ground at 485 mph. And at 400 miles per hour, we have 8g on the ground level with a trimmer in neutral, and we can get even more if we help with a trimmer - 10+ g. And 400 miles per hour is also pretty much speed...
And finally. It should be noted that in the 44th year there was a modification of the control system. A "bobweight" was mounted on the stick. Without its installation, indeed the stick was too light, and at the same time there was a danger of easily exceeding the overload restrictions.

So I appear to wrong on the high alt speeds. The plane does not seem to compress until 0.80 mach. However the real problem is at low altitudes and this is probably why people are noticing it. 

 

The results indicate that the airplane should be restricted to a Mach number of 0.80 due to compressibility difficulties which become increasingly dangerous beyond that point.

 

 

Vibration.- At a Mach number of 0.76 a true effect of compressibility becomes evident in the form of a complete vibration of the airplane. This vibration is caused by a combination of compressibility effects on the wing and the horizontal stabilizer. The condition becomes increasingly severe as the Mach number increases and could eventually cause a primary structural failure.

            7.   Maximum Limit of Combat.- The airplane has been dived to a maximum Mach number of 0.85 and on several occasions to 0.84. In each case the pilots reported that the vibration became extremely heavy beyond 0.80. In each dive to 0.84 or above the vibration became so severe that the airplane was damaged. The leading edge skin of the wing flap was buckled between rivets, a coolant radiator cracked and hydraulic line broken due to vibration on various dives to 0.84 and above. In extreme war emergency the airplane can be dived to a Mach number of 0.83 (400 m.p.h. Indicated Airspeed at 25,000 ft.), if a very gradual pull-out is made.

 

Recovery Technique.- Recovery in any case must be gradual and executed with extreme caution since relatively light elevator stick forces or rapid application of trim may very easily result in the application of excessive load factors. As acceleration is applied at the beginning of the pull-out some increase in vibration may occur. This will gradually decrease as the recovery is completed. In no case is elevator trim necessary to aid recovery. The normal pull-out distance stated in Pilot’s Information File apply. The pull-out distances stated in Sec.II, Para.21, page 26 of Pilot’s Operating Instructions AN-01-60JE-1, are not correct.

 

This should be a cut and dry issue. The manuals and tests are explicit and in the game behavior is more or less the opposite of reality. It should also be noted the main issue is below 5000ft where the placarded limit of 505 is a structural number and not a compression limit. This is why in some manuals it does not change as it lowers in height. As the game already reflects, the structural number has a safety margin and is not the real structural limit (as the dive tests also show.) The problem is that the game treats 505mph at 5000ft (and probably between 10 and 5000), as a compression onset not a structural only number. 505 mph at 5000ft would be 0.72 mach, not 0.8 which all the other speeds correspond to. The plane should not compress at low altitudes until 0.8 mach or 560mph IAS. 

Edited by [TLC]MasterPooner
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P-47 has the same issue. The new Razorback is going to suffer from the same thing. 
 

Greg’s videos have tons of data on its elevator effectiveness, as does America’s Hundred Thousand (talking about the Thunderbolt here). It’s simply wrong in this game, as is the Mustangs. There’s no evidence as to why the Tempest is the only plane with incredible elevator authority at speed, while others lack it. 

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LColony_Red_Comet
12 hours ago, Gavrick said:

Firstly, when you diving at high speed, you should not forget about the effect of compressibility. In this case, it is not speed that matters, but the Mach number. On the left side of cockpit there is a plackard with a speed limit depending on the height. You say that the 485 mph plane is poorly controlled. So, but above 5000 feet it is forbidden speed. One of the effects of compressibility is a drop of aerodynamic control surfaces efficiency. That is why they write that it is useless to use a trimmer - with a large M number, the elevator or aileron itself loses effectiveness.
Further. Suppose we have a speed of 485 miles per hour near the ground. At the same time, when 50% of fuel, we can make about 4g, and this is a lot, considering the speed, and the fact that there is no getting away from the “stiffing” of the control - for example, in the same dive report it is stated that the stick force is “relatively” light in dive. And if you reset the trimmer to neutral, it will be 5g near ground at 485 mph. And at 400 miles per hour, we have 8g on the ground level with a trimmer in neutral, and we can get even more if we help with a trimmer - 10+ g. And 400 miles per hour is also pretty much speed...
And finally. It should be noted that in the 44th year there was a modification of the control system. A "bobweight" was mounted on the stick. Without its installation, indeed the stick was too light, and at the same time there was a danger of easily exceeding the overload restrictions.

You appear to be correct on all altitudes except somewhere between 10-5000ft and below. Please reference my updated post. Or this:  It should also be noted the main issue is below 5000ft where the placarded limit of 505 is a structural number and not a compression limit. This is why in some manuals it does not change as it lowers in height. As the game already reflects, the structural number has a safety margin and is not the real structural limit (as the dive tests also show.) The problem is that the game treats 505mph at 5000ft (and probably between 10 and 5000), as a compression onset not a structural only number. 505 mph at 5000ft would be 0.72 mach, not 0.8 which all the other speeds correspond to. The plane should not compress at low altitudes until 0.8 mach or 560mph IAS. 

 

I think people are noticing it because the plane suddenly starts to seize at low altitudes where it shouldnt because the final numbers are not compression numbers in the manual. We are also losing landing gear doors barely above the 505mph limit which cannot be right because structural damage was not taken until 0.84 mach. 

Edited by [TLC]MasterPooner
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sierrabob

https://www.flyingmag.com/aircrafts/pistons/jet-jockey-flies-p-51-mustang/   In this article the pilot talks about the force required to do a 4g and 5g turn and yet I see in the discussion here that the P-51 stick force is light. I know he is not talking about a dive, but the airspeed is a lot lower in his example. So is he wrong or how much stick force is needed to do a 4g turn? I've wondered about this for the purpose of building my on flight stick.

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LColony_Red_Comet
28 minutes ago, sierrabob said:

https://www.flyingmag.com/aircrafts/pistons/jet-jockey-flies-p-51-mustang/   In this article the pilot talks about the force required to do a 4g and 5g turn and yet I see in the discussion here that the P-51 stick force is light. I know he is not talking about a dive, but the airspeed is a lot lower in his example. So is he wrong or how much stick force is needed to do a 4g turn? I've wondered about this for the purpose of building my on flight stick.

He is quoting a rather well known "test" that was done in the 80s. Have a look through it, practically nothing in it is accurate. I consider everything in that document suspect because it contradicts virtually every other report. It is far more likely their test methods sucked. The pilot in that article even quotes a completely contradictory statement from another pilot saying he could fly the mustang one handed. 

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sierrabob

Compared to everything else I've read it does seem his methods must be screwed up. The flight manuals even talk about light stick pressure with the P-51. I thank you for your reply. I think you're right. I still wonder if there how much difference in stick force through different speeds. I wonder if there is a chart of this info. Any ideas? In my ultralight I could tell the airspeed by the stick resistance and I was wondering if it was the same in the P-51.

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Floppy_Sock

Do we know what the configuration of the 80s 51 was. I remember reading that as well and being surprised the stick forces were so heavy.

 

 Maybe CG related? A fully loaded 51 with guns, radio, etc probably has a lower stability margin and therefore lighter stick forces? 

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LColony_Red_Comet
2 hours ago, =362nd_FS=RoflSeal said:

If I am reading this right is barely ever breaks double digits even with the bobweight, thanks for the post

 

TO DEVS:

 

Is this being looked at for 5000 feet and below? Because it seems fairly obvious that the plane is compressing based on the structural number and not the mach number.

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Floppy_Sock

While we're talking about compression, why is the nose heavy pitching moment near and above the critical mach number not present?(mach tuck) 

 

You can take the 51 in a full power dive from 30k feet, at 20k you're well above critical mach number and there's no noticeable change in pitch behavior. 

 

Edit: This is at odds with the me262 for example which seems to have the tuck behavior included, though it seems to be quite scripted. 

 

Edit 2: the p38 exhibits this behavior as well but it's not as intense as in the 262.

 

 

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LColony_Red_Comet
59 minutes ago, Floppy_Sock said:

 

 

You can take the 51 in a full power dive from 30k feet, at 20k you're well above critical mach number and there's no noticeable change in pitch behavior. 

 

 

 

 

What are you talking about. If you dive to any of the dive speeds in game with the P-51 you get massive buffeting and the elevator controls seize up dramatically. The only exception to this is at low altitudes where the critical mach number is being substituted by the structural number and you actually compress sooner than you should.

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Floppy_Sock

@[TLC]MasterPooner

Another - arguably more dangerous consequence of compression is colloquially referred to as a mach tuck.

 

1280px-Transonic_flow_patterns.svg.png

 

Even at aircraft speeds well below the mach 1, the air above the airfoil can approach and exceed the mach 1 and a standing normal shock forms. This is what causes the terrible buffeting and control surface flutter.  

 

This pushes the center of pressure rearward. It also effects the downwash over the elevator - both of which contribute to a nose down moment. In combination with the less effective control surface, this can turn into an unrecoverable dive. 

 

This was why the p38 had dive brakes - it had a critical mach number of 0.65 which was easy to achieve. 

 

My point above is that the only aircraft that does this correctly is the me262. 

 

Edit: I was wrong - the p38 does have increasing nose down behavior at high speed modeled. 

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VBF-12_KW

In the actual dive testing of the Mustang performed back then, they exceeded Mach .8 on a number of dives and even reached .85 in one case.  They never reported any Mach tuck or nose over tendency.  The big problems were vibration which started causing airframe damage at .84.  Just like in the various P-51 manuals they emphasized that great care was needed in recovery due to low stick forces and the potential to over stress the airframe. 

 

http://www.wwiiaircraftperformance.org/mustang/mustangIV-divetest.html

http://www.wwiiaircraftperformance.org/mustang/p-51d-dive-27-feb-45.pdf

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=362nd_FS=RoflSeal

The P-51 dive test and manuals also mention the high speed behaviour of porpoising with fabric elevators. The later Mustangs with metal elevators and a modified stabilizer incidence angle have a more controlled behaviour
image.png.39c69b8648537357067173dc06d1c2c7.pngimage.png.95539b5d4f30db02f47c9c4d4688c3ba.png
 

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Bremspropeller

The metal-elevator P-51 is very similar to the Fw 190A in regard to forces at given Mach. The stick-forces of the 190 are between 25 and 28kg at given stabilizer setting for Mach numbers between 0.75 and 0.79.

 

Check this document (original document and graphs are linked):

http://www.wwiiaircraftperformance.org/fw190/fw190-0022-dive.html

 

It would be interesting to know which amount of movement can be undertaken by the trim-jack of the Fw 190 at high q and high Mach.

The dive-test linked above was undertaken at a constant stabilizer setting.

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sierrabob

https://crgis.ndc.nasa.gov/historic/P-51_"Mustang"_Archives_Collection

Dive.thumb.jpg.9921b0b13bf79f32f389217e8f28db62.jpgThere is some good info at this site. There is info on stick forces for dives, rolls and rudder forces.

This is one page of one of the docs. Not sure it will be readable here.  It mentions 30 lbs. of stick force to pull out of a dive at 5 G's

 

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VBF-12_KW

Now that we have the G meter in the aircraft, I decided to revisit this.  Kuban Autumn, P-51D clean with 50% fuel I started my pull outs under 5,000ft at around 485mph indicated.  Using 0% (neutral) trim setting produced about 2-2.5G initially with FULL aft stick.  Running the same dive profile but with 20% nose up trim dialed in ahead of time, the same full aft stick resulted in  4.5-5G initially on the pull-out.  Clearly there is plenty of elevator effectiveness, but the stick forces are too high for the pilot to achieve them without dialing in a bunch of trim (exactly the opposite of what all the manuals state).  485mph in a standard atmosphere at around 5,000ft is mach .65 or so, so there should be absolutely no compressibility effects with a P-51 in this speed range.

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Bremspropeller

Doesn't the Mustang have three different bobweights or bungee-setups available?

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Ace_Pilto

Is it modelled incorrectly or is it modelled the way it is to prevent people repeatedly ripping their wings off and coming here to complain? 

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LColony_Red_Comet

I believe I know what the problem here is regarding the elevator response is. The critical mach number is not correct in game. @Gavrick

 

Please reference this chart:

 

image.png.87b1f5d4a9ec78eda1a7887ddd150889.png

This is from the aircraft manual as was already referenced from the OP. Note that all of the air speeds given here are for 0.75 mach. However the dive tests show that the plane was taken to 0.84 mach and that they placarded it at 0.8 as the functional limit. I have tested in game and the plane follows the above chart.

 

"The results indicate that the airplane should be restricted to a Mach number of 0.80 due to compressability difficulties which become increasingly dangerous beyond that point. It is recommended that the airplane be placarded with the following limit diving speeds:-

 

Pressure Altitude (Ft.) Pilot’s IAS (m.p.h.)
40,000 275
35,000 310
30,000 345
25,000 385
20,000 425
15,000 470
10,000 505
  5,000 505

 

So what is obviously going on here is that the game is based strictly on the manual limits, and not on the tests that show the plane could dive to 0.8 mach. Really the plane could dive beyond 0.8 mach, but was placarded there as a practical limit. The manual appears to have been even more conservative. And additional problem is that the game appears to take the 505 IAS at 5000ft to be the mach limit as well as the structural limit. If you carry forward the same 0.75 mach limit to 5000ft and sea  level, you get 526mph IAS and 576mph respectively. With the correct 0.8 mach limits, you would get 561mph and 608mph. While the 0.8 mach figures would probably not be practical due to the structural limitations that would be incurred by greatly exceeding the 505 notional limit, having the mach effects being dictated by this number causes the plane to lose control authority far too early and causes the curve of the compression zone to spike dramatically in dives below 5000ft.

 

My request would be that the plane should have is high speed dive characteristics changed to model the 0.8 mach number as the onset of severe compression, not 0.75 mach. And the compression effects should be disentangled from the structural number below 5000ft.

 

 

 

Edited by [TLC]MasterPooner
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Gavrick
On 7/14/2020 at 12:34 PM, [TLC]MasterPooner said:

The critical mach number is not correct in game.

Sorry, but you are wrong.

First, there is no "magic mach number" ingame, after that airpalne become "unrecoverable". And at M = 0.75, effects of compressibility begin to be noticeable, and with an increase in M they intensify. But this does not mean that after 0.75 the plane cannot be recover from dive, because this is limit and what the manual says.

Further. I checked right now. I tried to recover from steep dive (dive angles 50 ... 80) at mach numbers 0.8, 0.82, 0.84 (altitudes and indicated speeds, respectively ([m] / [kph]) - 3600 / 780, 5900 / 690, 5700 / 715). Fuel - 50%, trim in neutral, throttle closed. In all cases, the aircraft exits from dive with a loss of altitude of about 2-3 kilometers. It should be noted that the loss of altitude is less than what is written in the manual. This is by the way that the leadership is "taken literally."

And finally, I hope that in the future the model of the influence of compressibility on the controllability of the aircraft will be fine-tuned.
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LColony_Red_Comet
3 hours ago, Gavrick said:

Sorry, but you are wrong.

First, there is no "magic mach number" ingame, after that airpalne become "unrecoverable". And at M = 0.75, effects of compressibility begin to be noticeable, and with an increase in M they intensify. But this does not mean that after 0.75 the plane cannot be recover from dive, because this is limit and what the manual says.

Further. I checked right now. I tried to recover from steep dive (dive angles 50 ... 80) at mach numbers 0.8, 0.82, 0.84 (altitudes and indicated speeds, respectively ([m] / [kph]) - 3600 / 780, 5900 / 690, 5700 / 715). Fuel - 50%, trim in neutral, throttle closed. In all cases, the aircraft exits from dive with a loss of altitude of about 2-3 kilometers. It should be noted that the loss of altitude is less than what is written in the manual. This is by the way that the leadership is "taken literally."

And finally, I hope that in the future the model of the influence of compressibility on the controllability of the aircraft will be fine-tuned.

 

@Gavrick, I did not say that over 0.75 mach in game that the plane could not be recovered. I also did not say that It could not be recovered over 0.8. Where exactly did you get that from? Nowhere in my last post do I state that 0.75 mach is a magic number beyond which the plane cannot be recovered.  In game, as you just said, the plane starts to feel compression at 0.75 mach and it increases above this. The problem is that over 0.75 mach the plane loses considerable control authority in a manner that contradicts the manuals and the tests. The Manuals and the tests state quite explicitly that the plane does not lose control authority or require trim to exit a dive. Whatever mach number would have seen the onset of significant elevator stiffness, it was beyond 0.8 mach, since in the manuals and tests it makes it quite clear that at these speeds there is no significant loss in elevator authority. So my point still stands. What is seems that you have done is implement significant control stiffness above 0.75 mach, more than seem actually since you yourself made that quite explicit in your last post. The suggestion is to shift the onset of control loss to 0.8 mach instead of 0.75. As was clearly stated in my last post.

 

And you did not even address the point about confusing the mach number with the structural numbers. 

 

 

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VBF-12_KW
On 6/22/2020 at 1:18 PM, =362nd_FS=RoflSeal said:

 

After digging into this source a bit more, I found some other interesting bits.  TO-01-60J-25 Dive Speed Limitations states that in their testing they exceeded the aircraft's dive speed limits by about 20-30mph "without any unusual characteristics" other than the longitudinal porpoising effect.  It gives the following guidance on recovery:  "If through necessity or inadvertance the above speeds are exceeded and pronounced compressibility in one or more of the above described forms are experienced, recovery should be effected by gradual reduction in power and gradual pull-up.  CARE MUST BE EXERCISED IN PULL-OUTS, SINCE THE STICK FORCES ARE RELATIVELY LIGHT AND ABRUPT PULL-OUT MAY CAUSE STRUCTURAL FAILURE.  THE ELEVATOR TRIM TAB WILL NORMALLY NOT BE REQUIRED TO AID RECOVERY.  HOWEVER, IF FOUND NECESSARY IT SHOULD BE USED WITH CARE AND IN SMALL INCREMENTS."

In this case they are clearly talking about recovering from speeds in excess of the dive speed limits, and once again, the big danger stated is over stressing the aircraft, not failing to recover from the dive.

 

TO-01-60-126 is a revision of TO-01-60j-28 that @=362nd_FS=RoflSeal posted above.  It replaces the earlier Tech Order and the first few paragraphs are the same but it adds a fourth section which states that in addition to CG, the shape of the P-51s elevator contributes to potentially instability under G load and then follows with some pretty eye opening stick force/G curves.  The numbers from the earlier TO are the same, at the same CG loading, but only for the first G (i.e. from 1g to 2g).  Stick forces immediately start getting lighter.  In the first graph showing a loading of fuel internal fuel and ammo, but with no fuselage fuel peak stick force is 20lbs (not per G - total) for just over 5Gs and the stick forces decrease as you pull further!  The low stick forces and instability at increased G is even more pronounced with an aft CG and these graphs make it easy to see why ALL the manuals warn to be careful in high speed pull outs - minimal inputs could quickly turn into blackout and structural failure level G forces. 

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  • 4 weeks later...
VBF-12_KW

@Gavrick Here's some additional information on this topic coming from AAF-51-127-5 Pilot Training Manual for the P-51 Mustang from August of 1945.  If you aren't a member you can't see the full document, but a free membership makes the whole thing visible.

 

Page 65 under Flight Characteristics: "It is very light on all controls ... If you've trimmed for normal cruising speed, the airplane will become nose heavy when you raise the nose and decrease airspeed.  Under the same normal cruise conditions, when you lower the nose and increase speed, the airplane becomes tail heavy in direct proportion to airspeed."

 

Page 66: "In designing the later models of the P-51and adding new equipment such as radio units and an additional gas tank, the center of gravity of the airplane has been moved back.  The effect is that the amount of back pressure necessary to move the stick has been reduced.  Instead of a force of 6 pounds per G of acceleration, you exert a force of only 1 1/2 pounds, the stick forces reversing as acceleration exceeds 4 g's.  This means you have to be careful in sharp pullouts and steep turns.  You can easily black out - and you can also put greater loads on the airplane than its structure was designed to withstand."  (my italics)

 

Page 67 goes into how filling the plane's fuselage tank makes it even more sensitive and prone to stick reversal.

 

Page 68 starts the High Speed Diving section.  From there: "It is capable of developing terrific speeds which make it no toy to be played with.  Yet its handling, even in high-speed dives, is not difficult if you know what you're doing.  In making a high speed dive the most important thing is to take it easy."

 

Page 70 Dive Recovery Procedures: "Ease the stick back.  Don't jerk the stick or otherwise overcontrol at this time.  Be sure you don't pull out abruptly.  Note that in this recommended dive recovery, you don't use the trim tabs.  It isn't necessary to use the tabs, and since they are extremely sensitive, it is recommended that you don't use them.  With the airplane trimmed for normal cruise, you can control the airplane in a high speed dive with only the stick and rudder pedals." (my italics)

 

Page 70: "In extremely high-speed dives, you can use the trim tabs intentionally, if you desire, but use them carefully.  If you use the tabs, the following procedure is recommended:

1. Trim the airplane for normal cruising.

2. About halfway through the dive, use slight elevator and rudder trim, but be careful not to trim the aircraft nose heavy.

3. As the airplane continues to accelerate, it again becomes tail heavy - increasingly heavy as speed increases.  However, make no further adjustments of the tabs.  After having made this one adjustment, you can control the airplane easily with stick and rudder.  The ailerons become increasingly heavy as the speed of the airplane increases." (my italics)

 

In game, the aircraft never becomes tail heavy as speed increases.  I conducted a series of test flights, diving from around 13,000ft on Kuban autumn with 68% fuel.  Trimmed for level flight (around 17-20% nose down) at cruise power, and pitching down into the dive the airplane happily continues diving with just the slightest touch of forward stick pressure while accelerating from 250mph IAS past 500mph IAS.  If I slam the stick back at 5,000ft and 500mph IAS in this trim condition (17-20% nose down, set for cruise) it generates about 2.5 - 2.8 G.  There is exactly 0 threat of blacking out or exceeding the structural limits of the aircraft.  If you start rolling in lots of nose up trim to make the aircraft tail heavy, you can start to generate more G's and eventually with enough trim you can black out or damage the aircraft.  Clearly the elevator has enough authority to do what it should, but the stick forces are much too high in game and so the pilot can't achieve them without mass trim input.  This becomes a pretty big deal when you are chasing someone in a dive, as the plane essentially locks up as you approach redline and you have to fly it with the trim - you have no chance of engaging a target, and all you can hope for is pulling out before the wheel doors rip off or you hit the ground.  This really eats away at what was one of the plane's big strengths in combat - its excellent dive characteristics.

 

 

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KW, while i admire your research and clear, historical documentation, i really don't think they care.

 

Remember when they put .50 API rounds in after redoing the damage model?

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2 hours ago, thatguy said:

Remember when they put .50 API rounds in after redoing the damage model?

 

API rounds are on the list of things planned to be implemented around the same time as better fuel tank modeling.

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@KW_1979 Ok. I am not going to agree or deny now that control should be "easier". I need to collect all the materials again and think about this problem. Perhaps during work on the future P-51. I think at least the efficiency of the trims should be tweaked. Perhaps this problem too. But I cannot promise that something will be changed, I will repeat - it will be necessary to evaluate all the data again. Perhaps several problems were mixed in this topic - an increase in stick  force, a loss of control due to the M number, as well as differences in aircraft with and without a "bobweight".
 

8 hours ago, thatguy said:

i really don't think they care.

Yes. Of course "they" don't care. It doesn't matter that they answer on the forum, they make corrections, as with the gear bay drag recently. Obviously "they" don't care.

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6./ZG26_Klaus_Mann
7 minutes ago, Gavrick said:

@KW_1979
 

Yes. Of course "they" don't care. It doesn't matter that they answer on the forum, they make corrections, as with the gear bay drag recently. Obviously "they" don't care.

Don't let the Naysayers discourage you Guys. Your Hard Work never goes unappreciated by a large but mostly silent Group (of which I am a quite Vocal Part).

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VBF-12_KW

Thanks for taking the time to discuss this @Gavrick.  I think the incredible attention to detail that goes into this product is a clear illustration of how much the whole dev team cares, and it’s why so many of us love the game.

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  • 2 months later...
On 8/14/2020 at 6:39 AM, Gavrick said:

@KW_1979 Ok. I am not going to agree or deny now that control should be "easier". I need to collect all the materials again and think about this problem. Perhaps during work on the future P-51. I think at least the efficiency of the trims should be tweaked. Perhaps this problem too. But I cannot promise that something will be changed, I will repeat - it will be necessary to evaluate all the data again. Perhaps several problems were mixed in this topic - an increase in stick  force, a loss of control due to the M number, as well as differences in aircraft with and without a "bobweight".
 

Yes. Of course "they" don't care. It doesn't matter that they answer on the forum, they make corrections, as with the gear bay drag recently. Obviously "they" don't care.

 

On 8/14/2020 at 6:47 AM, 6./ZG26_Klaus_Mann said:

Don't let the Naysayers discourage you Guys. Your Hard Work never goes unappreciated by a large but mostly silent Group (of which I am a quite Vocal Part).

 

Feel free to prove me wrong.  It's been 5 months and 4 patches :)

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Legioneod
20 minutes ago, thatguy said:

 

 

Feel free to prove me wrong.  It's been 5 months and 4 patches :)

Patience. Just because something doesn't get fixed (if it even needs to be fixed) when you expect/want doesn't mean they aren't looking into the problem. Cut them some slack, they have alot more to worry about than some small issues with the P-51 or .50s.

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SAS_Storebror
1 hour ago, Legioneod said:

they have alot more to worry about than some small issues with the P-51 or .50s.

...for instance?

If crippling the main allied weapon of late WW2 to complete uselessness and at the same time, making both main allied fighters of late WW2 underperform are small issues, which are the big ones? Getting the remaining parts of 109s to become indestructible too, like their tail?

 

:drinks:

Mike

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18 minutes ago, SAS_Storebror said:

...for instance?

 

Keeping the team functional while most of them are not working in the office, for instance?

 

 

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SAS_Storebror

I'd buy your argument @LukeFF if it wasn't about priorities too.

 

Believe it or not, but from a customer's point of view using Covid as an excuse for not having dealt with extremely serious issues reported for more than half a year, while at the same time rolling out something which... words fail me... you get the gist, you surely will.

 

:drinks:

Mike

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On 11/12/2020 at 7:45 PM, Legioneod said:

Patience. Just because something doesn't get fixed (if it even needs to be fixed) when you expect/want doesn't mean they aren't looking into the problem. Cut them some slack, they have alot more to worry about than some small issues with the P-51 or .50s.

 

They have released new planes built from scratch while ignoring adding an HE round into a belt that they just took it out of.  Random pilots have been able to mod this without any access to the dev team or code for offline comparison.  They can take all the time they want to model fuel lines, until then I want HE rounds back in the 50s.

 

Here's a great example of a potential dev response:

"Hey guys!  Our remodel of fuel systems has taken longer than we thought, so we have added HE round back into the 50 cal belt as a stopgap.  Sorry for the wait!"

 

That shit could get done on a Friday afternoon after a liquid lunch.  If they cared, they would have fixed it.  Likewise with the elevator response

 

On 11/12/2020 at 10:02 PM, LukeFF said:

 

Keeping the team functional while most of them are not working in the office, for instance?

 

 

Please see below

 

A programmer vs a programmer in quarantine same picture

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Mitthrawnuruodo
21 minutes ago, thatguy said:

They have released new planes built from scratch while ignoring adding an HE round into a belt that they just took it out of.  Random pilots have been able to mod this without any access to the dev team or code for offline comparison.  They can take all the time they want to model fuel lines, until then I want HE rounds back in the 50s.

 

What are you talking about? The M2 .50 did not fire HE rounds.

 

26 minutes ago, thatguy said:

Please see below

 

A single programmer is quite different from a team of developers used to meeting in a single office.

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