Thoughts on the Current Flight Model

[Widewing]

I've dabbled with many WWII sims and games, and I am fully convinced that the flight modeling in Aces High is the closest to reality of any of the others.

Nonetheless, there are some issues that may deserve review as time and priorities permit.

1. Our current F6F-5 is too slow (at least 20 mph) above 18,000 feet when compared to flight test data of the era. It also has flaps with multiple position settings. In reality, the F6Fs had no intermediate flaps positions. They were either up or full down. In addition, the F6F-5 suffers from an odd dynamic instability in its roll axis when slow with flaps deployed. This is exactly opposite of the F6F's excellent roll stability when near stall and dirtied up for landing.

2. The AH2 P-40E is equipped with WEP. Real P-40Es were not so equipped. Our P-40E is far more like the later P-40K, fitted with the V-1710-73/FR4 engine.

3. In-game testing of the AH2 P-40B reveals that it performs like the much heavier P-40C. The C model was fitted with shackles and plumbing for and external drop tank. In addition, the C model carried more armor. A real P-40B was just as fast as the P-40E, but was lighter and more agile. Due to having internally sealed fuel tanks, the P-40C had less internal fuel capacity than the P-40B.

4. When the last change was made to the drag model, some aircraft suffered a loss of handling and maneuvering performance. Chief among that group was the P-51s. For example, at 25% fuel, without flaps, a P-51B has a lower wing loading than the P-47D-11. It also has a very similar coefficient of lift. It should out-turn the Jug. Yet, it does not. Once flaps are deployed it gets worse for the Mustang. I have detailed the issue in this thread.

5. Flap effect on turn performance and drag is somewhat odd and inconsistant throughout the plane set. I will be testing this thoroughly in the near future, comparing results from older versions of the software to the current version.

6. Some aircraft demonstrate unusual stall behavior when flown into a power-off nose-high stall.

7. While Aces High limits WEP to five or ten minutes depending upon type. there is no accounting for comsuming the various types of water/ADI. WEP use is based upon engine temperature, which allows for recovery of full WEP duration. There is no option to exceed recommended WEP duration, even though there is plenty of test data where WEP was used for as much as 15 minutes during max power climb testing. Perhaps a variable could be introduced that would induce an engine failure randomly if WEP were used beyond the recommended maximum.

8. P-factor does not appear to be modeled.

9. Of all American Naval aircraft, only the F4Us should have tail hook use tied to landing gear position. Grumman aircraft and the SBD should be able to lower their tail hooks independently of landing gear position.

10. Machine gun ammunition load-outs could be varied in the F6F and F4U.

11. The A6M2 dives far too fast, greatly exceeding the speed at which it should suffer damage. Its dive behavior is vastly different (read that as superior) than that of the strengthened A6M5.

12. Both Yaks can dive at extremely high speeds, but can do so with very good control and with virtually no compressibility effects.

Please feel free to add to this list, but please make sure you can back up your points with primary source data or other credible sources (for example, the History Channel isn't a good source).

My regards,

Widewing

[Benny Moore]

Originally posted by Widewing
The AH2 P-40E is equipped with WEP. Real P-40Es were not so equipped. Our P-40E is far more like the later P-40K, fitted with the V-1710-73/FR4 engine.

But is the actual power rating higher than it should be?  American fighters did not have a special War Emergency Power control.  It was activated simply by firewalling the throttle (usually breaking through a wire so that the ground crew could immediately tell whether or not you used War Emergency Power).  So really all American airplanes should not have a War Emergency Power toggle, but instead should simply be able to get the same amount of power by simply pushing the throttle wide open.

I'd like to add that the P-38, while being very close to reality in stalling characteristics, still has some tendency to drop off on a wing even when there is no slip or skid.

[mussie]

My source of information involves animal entrails and three naked virgins...

Is that OK...?

J/K

[Saxman]

I don't have the data myself, but F4UDOA has posted it in the past: The F4U-1D could also carry ordinance on the center pylon. There are loads of 3xbombs, or 2xbombs + 1xDT on DOA's charts.

The F4U-1 (birdcage) should not have WEP (also per previous threads). In honesty, IIRC the birdcage also didn't carry ordinance standard, but that this was rather a field modification.

An option to fly as a land-based F4U-1A without the arrestor gear (and associated weight) and the weight of wing fold mechanisms would be nice. Many 1As were built that way out of the factory, (especially the Goodyear builds) and quite a few more were field-modified to remove them.

Also, while not a FLIGHT issue, I've shown in this thread  that the gunsight for the bubble-top Hogs should be doubled in size, and that of the FM-2 and F6F need to be very slightly enlarged (see my posts using the Fw-190D to scale the sight). I haven't tested the historical sights of other aircraft, but it's reasonable to assume that some others might be incorrectly sized if one wanted to use the historical sights as well.

[Bronk]

Originally posted by Benny Moore
But is the actual power rating higher than it should be?  American fighters did not have a special War Emergency Power control.  It was activated simply by firewalling the throttle (usually breaking through a wire so that the ground crew could immediately tell whether or not you used War Emergency Power).  So really all American airplanes should not have a War Emergency Power toggle, but instead should simply be able to get the same amount of power by simply pushing the throttle wide open.

I'd like to add that the P-38, while being very close to reality in stalling characteristics, still has some tendency to drop off on a wing even when there is no slip or skid.

Benny not all have a throttle. So to simulate pushing past the wire is the p key.

Bronk

Edit : Some throttles do not have a detent to simulate the wire either.

[Widewing]

Originally posted by Saxman
I don't have the data myself, but F4UDOA has posted it in the past: The F4U-1D could also carry ordinance on the center pylon. There are loads of 3xbombs, or 2xbombs + 1xDT on DOA's charts.

The F4U-1 (birdcage) should not have WEP (also per previous threads). In honesty, IIRC the birdcage also didn't carry ordinance standard, but that this was rather a field modification.

This reminds me.... The F6F-5 should be able to carry bombs on both pylons AND a belly tank. In AH2 it's either bombs OR a belly tank.

My regards,

Widewing

[Benny Moore]

Originally posted by Bronk
Benny not all have a throttle. So to simulate pushing past the wire is the p key.

Bronk

Edit : Some throttles do not have a detent to simulate the wire either.

I am aware of this.  My own throttle is merely a slider.  However, the wire was not really a physical obstruction; real pilots usually use the manifold pressure guage to determine power, not the actual throttle.

But my main point is that what the War Emergency Power key does in game was done in real life by simply giving full throttle.  Thus, saying "the P-40 should not be able to use the War Emergency Power key" doesn't really make sense, as that just simulates firewalling the throttle.

So my question for Widewing is, is the highest power rating available to the P-40E in Aces High II correct, or not?  If it is, then it doesn't make sense to take away the ability to use the War Emergency Power key unless you raise the military power rating to the same rating.  But if it isn't, then I agree that there's a problem.

[Widewing]

Originally posted by Benny Moore
So my question for Widewing is, is the highest power rating available to the P-40E in Aces High II correct, or not?  If it is, then it doesn't make sense to take away the ability to use the War Emergency Power key unless you raise the military power rating to the same rating.  But if it isn't, then I agree that there's a problem.

In the game, MIL power MAP rating is about 46 in/hg. Increasing to WEP boosts MAP to about 53 in/hg. All data that I have for the V-1710-39 in the P-40E indicates 46.2 in/hg MIL power (no WEP rating).

My regards,

Widewing

[dtango]

Originally posted by Widewing

4. When the last change was made to the drag model, some aircraft suffered a loss of handling and maneuvering performance. Chief among that group was the P-51s. For example, at 25% fuel, without flaps, a P-51B has a lower wing loading than the P-47D-11. It also has a very similar coefficient of lift. It should out-turn the Jug. Yet, it does not. Once flaps are deployed it gets worse for the Mustang. I have detailed the issue in this thread.

6. Some aircraft demonstrate unusual stall behavior when flown into a power-off nose-high stall.

8. P-factor does not appear to be modeled.

Widewing- a few comments regarding #4,#6, & #8:

#4 - I didn't post this in the other thread but something to consider is the difference that power-loading has on turn performance between the P-47D-11 and P-51B.  The D-11 given the weights you listed has a better power-loading compared to that the P-51B.  It's conceivable that in a sustained turn the P-47D-11 has an advantage in turn radius and rate vs. the P-51B even though this isn't true from an instantaneous turn perspective.

#6 - we discussed this in the spit death stall thread but I actually brokedown your spit stall film into frames for analysis.  I'll post this sometime.  It's pretty interesting to consider the physics at work to figure out what makes sense vs. not in cases where the aircraft is in very high angles of attack at very low airspeeds.

#8 - P-factor is modeled.  If you look at this pic from Pyro from the stall speed thread you'll see it.



Notice the assymetric thrust of the prop: right, top, & left and notice how they are different and how the downward side (right) of the prop has a higher thrust than the upward side (left) of the prop.

Always appreciative of your well-reasoned posts.

Tango, XO
412th FS Braunco Mustangs

[Widewing]

Originally posted by dtango
Widewing- a few comments regarding #4,#6, & #8:

#4 - I didn't post this in the other thread but something to consider is the difference that power-loading has on turn performance between the P-47D-11 and P-51B.  The D-11 given the weights you listed has a better power-loading compared to that the P-51B.  It's conceivable that in a sustained turn the P-47D-11 has an advantage in turn radius and rate vs. the P-51B even though this isn't true from an instantaneous turn perspective.

#6 - we discussed this in the spit death stall thread but I actually brokedown your spit stall film into frames for analysis.  I'll post this sometime.  It's pretty interesting to consider the physics at work to figure out what makes sense vs. not in cases where the aircraft is in very high angles of attack at very low airspeeds.

#8 - P-factor is modeled.  If you look at this pic from Pyro from the stall speed thread you'll see it.



Notice the assymetric thrust of the prop: right, top, & left and notice how they are different and how the downward side (right) of the prop has a higher thrust than the upward side (left) of the prop.

Always appreciative of your well-reasoned posts.

Tango, XO
412th FS Braunco Mustangs

My issues related to the P-51B vs P-47 are also supported by Brit data that shows the Mustang III (P-51B) turns much smaller circles than the P-47. There is also testing at Eglin Field that supports the argument.

From http://www.wwiiaircraftperformance.org:

PROOF DEPARTMENT
TACTICAL COMBAT SECTION
ARMY AIR FORCES PROVING GROUND COMMAND, EGLIN FIELD, FLORIDA
FINAL REPORT ON TACTICAL SUITABILITY OF THE P-47C-1 TYPE AIRCRAFT
18 December 1942

1. OBJECT:

To determine the relative tactical value of the P-47C-1 type aircraft for combat service.

(snip)

3) Maneuverability -- The P-47C-1 was flown in mock combat against the P-38F, P-39D1, P-40F, and the P-51.  
   
 (a) It had superior rate of aileron roll at all speeds, and especially at high speed to all American fighter contemporary types, none could follow it in a fast reverse turn.  
   
 (b) The turning circle of this aircraft was larger than any of the other types engaged in combat. The high wing loading makes the plane mush in all maneuvers controlled by the elevators, and this also causes high speed stall in tight turns.  
   
 (c) It was slightly slower in acceleration from level flight at fifteen-thousand (15,000) than all types except the P-40F, which was decidedly slower, however, the distance gained in the initial acceleration was never greater than fifty (50) yards and the P-47C-1 rapidly overhauled and passed the other types. This test was with closed shutters and the liquid cooled engines rapidly overheated, the shutters had to be opened and the planes decreased a good deal in speed allowing P-47C-1 to run away rapidly. In push-overs with maximum manifold pressure the P-47 accelerated faster and drew away from all other types.  
   
 (d) In testing the zoom ability of the P-47C-1 it was found that from level flight and dives, the zoom was comparable with the P-40F. The P-39D1, P-38F, and P-51 have greater zooming ability.  
   
 (e) In close fighting the P-47C-1, due to its faster aileron roll, can quickly reverse turn and break off the combat almost at will. However, due to the large turning circle and low rate of climb, it is deemed inadvisable to attempt to dog fight with any type of enemy fighter now used in the combat area.

In short, the P-51B should run circles around the P-47D-11.



As to the stall behavior, I can stall an aircraft and it drops straight down without a hint of rotation. In the case of the Mosquito, it has 8,000 lb of thrust and the corresponding torque. Both are ignored and the aircraft has zero forward motion, while wings are level and without any rotation whatsoever. I have a real problem accepting that this is normal behavior, especially since this behavior was introduced with an update to the software and had not existed prior.

If P-factor is modeled correctly, I would think that there should be some slipstream impingement on the rudder. I don't see any. Which is why it is impossible to perform a true hammerhead stall.

My regards,

Widewing

[Ball]

Widewing, when doing your testing please can you take a look at the torque effects on (especially late war) aircraft?

Some late war rides seem to suffer very little whilst others seem harshly penalised.

I fly both LA7 and N1K a fair bit and neither of them seem to suffer ANY adverse effects of torque.

Thanks.

[Krusty]

WEP in AH is a very generic term. P40Es didn't have it, nor did birdcage F4us, but they DID have a "max power" that usually was limited to 5-10 minutes before the engine overheated.

When you hit P you're not injecting go-juice, you're just saying "Enable the highest settings that can only be used temporarily.

As for the go-juice not being modeled: I think they did that on purpose. Just my intuition. I think they wanted to simplify engines to a big degree.

EDIT: Oh, the newer models (f4us) might have their FMs re-done every time they're upgraded. The Mossie might get fixed, but only when they redo the entire plane. There's some other planes with unusual flight characteristics, as well. Most of them are generation 1 planes.

[1K3]

The Mosquito model needs to be checked too.  Pull the stick had and it will enter the comical spin:rofl

[1K3]

And what is up with Ki-84 breaking up at 450mph in dive.  I need to see report of 84's breaking up @ 450mph dive in real life (if it even exists...lol)

[dtango]

Widewing:

I've looked over the Brit report.  Thanks for providing the data from the USAAF Eglin report.  You probably have the AHT turn performance comparison data from the Joint Fighter Conference as well.

Not sure about the Brit report but the Eglin and the AHT performance numbers appears to be derived from instantaneous turn performance.  I absolutely concur that the P-47D-11 has a higher wing loading vs. the P-51B and therefore should be worse in instantaneous turn performance.  One way we could check this is checking the 1-g level stall speeds of the both aircraft.  Maybe someone has the time to use Brooke's method to test the AH models to verify which one has the higher wing loading by checking 1-g stall speeds.

Sustained turn performance however is something else altogether.  Just like wing-loading is a rough measure of instantaneous turn performance, power-loading gives us some insight into possible differences in sustained turn performance.  From the figures you quoted in the other P-51 thread the P-47D-11 has a better power-loading compared to that the P-51.

On the Mossie, I didn't realize it didn't have counter-rotating props and haven't thought through the dynamics of that situation.  Post stall characteristics especially at extremely high angles of attack can be really tricky to analyze.

Just a note on p-factor - p-factor and corkscrewing propwash (propwash impingement on the rudder) are two different things.  P-factor is basically the prop-disc producing assymetric thrust due to the down-going blade having a higher velocity therefore producing more lift/thrust vs. the upgoing blade when the prop is at some angle to the relative to freestream air.  Your point is taken however regarding yawing moment due to propwash but I think after we breakdown the AH "deep stall" a bit you'll see what's going on.  When I get a chance I'll organize and post the frame by frame analysis.

Tango, XO
412th FS Braunco Mustangs