RHS Maneuverability Review: Data [ALL Data Done] (Full Version)

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el cid again -> RHS Maneuverability Review: Data [ALL Data Done] (8/12/2006 11:24:30 PM)

Based on a specific private request for review of the P-38 in particular

and general discussion of maneuverability ratings

I am attempting to review the Maneuverability rating system used by RHS
for a new RHS series (which will be numbered 5.xx for clarity that there is a difference).

This is a low intensity (not time intensive) review - and it may take a long time to execute if we find a better system - because I fear vast amounts of data research (and no little calculation) may be required.

The best I can say about the RHS system is that it is openly defined, and it is subject to immediate change if a simple improvement is found, and subject to long term change if a difficult improvement is found. It at least has the virtue of consistency - given the data available it is possible to say "that is the right value".

And the formula is

[ (speed / 20) + (rate of climb / 500)] / Number of Engines.

I wish to have proposals for changes - not in abstract form - and not because "P-38 is not high enough" - but in specific form -
that is in the form of formulas that can be used with data we can actually
obtain to CHS/RHS standards in less than a lifetime of research.

Such proposals may take two forms:

Immediate: using data PRESENTLY in the data set (or clearly universally available, such as aircraft weight)

Distand: using data NOT in the data set (but which can be obtained)
and this ONLY is germane if you have specific sources for the data (including wierd types like J7W1) - if you cannot point to sources I cannot use the formula.



Nemo121 -> RE: RHS Maneuverability Review (8/13/2006 12:03:25 AM)

Could you list what the current formula is so we could see where the weightings have been changed and so what is now accorded greater importance than previously?



el cid again -> RE: RHS Maneuverability Review (8/13/2006 1:20:59 AM)

quote:

ORIGINAL: Nemo121

Could you list what the current formula is so we could see where the weightings have been changed and so what is now accorded greater importance than previously?


The formula is in the middle of the above post.

There is one qualifier (never used yet): a plane with multiple engines on the same axis does not count these as multiple - but as one.

I am thinking of using "square root of the number of engines" vice "number of engines" - which works well for the two engine case -
but not for the four engine case.

I am thinking of changing the algorithm from 80% speed in the upper body of the formula to 60% - that is to double the non-speed factor again (it was originally 10% and now is 20% in my view of things). Further, we could make the 40 % be more than just ROC. Instead, divide it something like this:

10% for ROC
10% for power loading
10% for wing loading
10% for something else (ideally roll rate - but I have no way to get the data for that on a comprehensive, consistent and authoratative basis)
If we cannot get roll rate, maybe we use another factor - or maybe we make wing loading matter 20%?

All these proposals would then be subject to "calibration" - comparing the result with what we have and with other data - over a large number - to see if it is closer - and closer by type?

Note I am not proposing a special rule for P-38 - I want a general rule for everything that happens to rate P-38 better in relative terms. Also note that P-38 must be better in durability vs any single engine plane with otherwise equal statistics - so it will be a better plane overall due to its second engine (sometimes it can go home with one engine turning). No one factor tells the whole story for an aircraft.



el cid again -> RE: RHS Maneuverability Review (8/13/2006 1:24:13 AM)

I think that the present algorithm says:

Speed is decisive 80% of the time in determining the tactical advantage a plane will have on a statistical average basis. Other things are decisive 20% of the time - and they are crudely represented by ROC.

I think we might prefer doubling that ratio - and making the non- speed component include things different than at present. The math is not important in that we can do it quickly. But the data is a problem - saying you want roll rate for example is lovely in theory and possibly impossible in practice. But roll rate is related to things we can know - so maybe using loadings etc will get us close enough?



Terminus -> RE: RHS Maneuverability Review (8/13/2006 1:25:50 AM)

The formula has been proved to be correct, I presume?



el cid again -> RE: RHS Maneuverability Review (8/13/2006 1:35:48 AM)

Regretfully, no. It is better to say we are engaged in a process of calibration. It appears the formula we now use is better than the data set used in other mods - I am not sure it is even right to say any of them have a consistent formula at all? But that is a very iffy statement
because:

a) It takes a LOT of data to validate - and we need a lot more to be confident this is true over time - particularly later in the war with higher performing aircraft;

b) There are still problems between plane types - in my view the 2 E fighter/night fighter case is a problem in ALL mods - RHS has reversed the problem but it is STILL a problem (stock and CHS and Nik Mod all give 2E fighters too high a performance, RHS too little). The ONLY point ALL mods seem to have right (a reference point?) is 4E types - and that is common in a wierd sense - they almost always are the same value!

c) Even if RHS is better than others in relative terms, it is NOT right.
That is, I am sure maneuverability can be better - if only we can figure out how to get there? This is a "quick and dirty" mod - anything better is used - but it is not theoretically going to fit all things to use such a simple algorithm.

It is in recognition of the latter point I am asking for input - I LIKE the criticism that the algorithm used is not ideal - I AGREE with it and ALWAYS agreed with that - and am attempting the tiny little detail of figureing out "what is actually better in a sense we can use it?" - something easy to say but not so easy to do.

EDIT: It appears that RHS is closer to NikMod values than to others. Nik used a result driven model while RHS uses a theory driven model corrected to result ranges. There are advantages to both models and I wish to say that NikMod air combat results are quite good and far better than what came before.



Terminus -> RE: RHS Maneuverability Review (8/13/2006 1:51:00 AM)

You call this "quick and dirty"? You should see the aircraft I put in my mod; there you can talk about quick and dirty...[:D]



Herrbear -> RE: RHS Maneuverability Review (8/13/2006 4:41:43 AM)

What is the rationale for dividing by the number of engines. You may have stated this before in other posts, but I don't remember it at the moment.

Thanks



el cid again -> RE: RHS Maneuverability Review (8/13/2006 6:50:19 AM)

It appears that this may be similar to the original formula used by Matrix. Actually, they seem to have divided by the number of engines for 1E and 2E planes UNLESS the plane was a 2E fighter - when they ignored the 2 - and it appears they multiplied by 2 again for 4E planes. Since RHS values are much lower, our 4E planes could have similar values if we just divided by 4 (vice 8) - and since I like consistency - I made all 2E planes the same. That resulted in a single denominator for all planes - which is good practice in equation building. The previous system has serious anomolies if you compare IDENTICAL planes used as bombers and fighters/night fighters. Either they have to be inconsistent, or one has to be out of sync with other 2E bombers or 2E fighters. On the other hand, fans of 2E fighters (P-38 in particular) don't like the impact of this consistent principle.

The idea is simple: multiple engines are always an advantage in terms of survivability (that is, durability rating) but always a disadvantage in terms of maneuverability rating. Wether or not it is directly proportional to number of engines is open to debate - and I am willing to (say) make it square root of number of engines (for example) - and then measure the impact and compare it with actual. Right now it appears that 2E fighters are relatively too effective in other mods but not effective enough in RHS - although I believe their overall value is well modeled in RHS (due to the increase in durability and also their long range - which is related to engine count).

Anyway - the compromise is not a happy one - and I want a better one - if it can be found.



Nemo121 -> RE: RHS Maneuverability Review (8/13/2006 12:51:32 PM)

Hmm, dividing by the square root of the number of engines will certainly help twin-engined fighters and bombers BUT if applied to four-engined bombers it is going to result in some four-engined bombers having quite reasonable manoeuverabilities which would fly in the face of their use en masse in formation flying. Still, if that's the way to get the P38 to be "more reasonable" in the opinions of various users then I say go for it. Mark my words though, it won't increase the P38s effectiveness enough for most and you'll find crys for the modelling of other issues as 2nd tier efforts to "improve" the P38s.

Also don't forget that what works for the P38 will also effect the Betty and make that a bit more survivable too. I think this is reasonable from reading some accounts from F4F4 attacks on Bettys and Nells during the Guadalcanal campaign but prep yourself for howls of outrage the first time someone gets a message that a Betty evades attack from some Allied plane.



el cid again -> RE: RHS Maneuverability Review (8/13/2006 1:26:40 PM)

The nice thing about these equations is that a bomber usually is lacking in speed and particularly lacking in ROC - so a 2E fighter may do better because of its high values in that regard. Then too, the night fighters (which typically ARE bombers) are sort of modest in these figures - placing them between high performance fighters and true bombers.
This is actually pretty good modeling.

But it may be that we should go back to the Matrix concept of doubling the value used for 4E bombers (and I assume any 3E plane that ocmes along). [Transports are the same as bombers]. And we might rationalize it as a formation flying factor - although clearly a 4E plane might not fly in a gigantic box formation. If we did that, RHS 4E values would not change at all - neither would any 1E plane - and only 2E planes would change. This change would benefit those with high performance most of all - and might be a happier compromise in terms of relative ratings. Wish I had thought of it before now.

Even so, I am proposing to go one step farther, by increasing the proportion of the upper section of the equation devoted to non-speed functions. Since power and weight are known in all cases, we can easily include wing loading and power loading - and these will help separate dogs from acrobats. Perhaps we might give 60% to speed (vice 80%), 20% to ROC (as now) and 10% each to Wing Loading and 10% to Power Loading - for the quick and dirty fix.

Longer term I would like to give 10% to roll rate - if it can be determined what that is to a proper standard for all planes - and reduce ROC to 10%.

And I STILL want any better ideas out there.

Whatever we try we will compare to what we have and to history - in general and in relative plane type senses.



Terminus -> RE: RHS Maneuverability Review (8/13/2006 1:49:44 PM)

2nd generation night-fighters (Beaufighter and Black Widow) shouldn't get Maneuverability ratings like bombers, though I agree with you on 1st generation (Blenheim, Havoc and Ventura).



el cid again -> RE: RHS Maneuverability Review (8/13/2006 2:04:27 PM)

I also agree with you - I think. I have tried to say that higher performance (speed and ROC now, and other things if we add them) mean the better 2E planes end up looking a lot more like fighters than bombers - and the low performance "fighters" look a lot like 2E bombers - particularly when it is the same plane (= same specs). I think a good formula will give us our cake and eat it to - rating both high and low performnce planes more or less properly.



Mifune -> RE: RHS Maneuverability Review (8/13/2006 4:55:05 PM)

Cid, just so I can understand. On your current proposal, how would your formula look?



spence -> RE: RHS Maneuverability Review (8/13/2006 5:42:08 PM)

quote:

though I agree with you on 1st generation (Blenheim, Havoc and Ventura


Can't help myself when it comes to this plane which Matrix completely messed up with its take on its capabilities.  This "first generation" twin engine bomber successfully ATTACKED and shot down Japanese "second generation" single engine fighters on several occasions (Oscar IIs, Tojos), even when operating at relatively long range (like in the Kuriles after flying from Attu).  It also attacked and shot down a variety of multiengine Japanese aircraft in one on one type confrontations while on patrol.  Admittedly the number of air to air kills by PVs is relatively small but there were no confirmed losses of PVs (1 or 2) in air-to-air combat with IJ forces.

Every source I've found that is actually describing the right airplane puts its top speed over 300 and range in the 1600 mile range (because of is airliner origins and the airliner origins of its predecessor and the similarity in sillouette [though not size] I kinda think a lot of casual "authorities" got them mixed up.



Terminus -> RE: RHS Maneuverability Review (8/13/2006 6:06:12 PM)

Yes, yes... We know you're partial to the Ventura, spence, and nobody's blaming you. It was messed up by Matrix, but can we please let this go now? It's been fixed in CHS, hasn't it?

Besides, we're talking about the night fighter Ventura here.



herwin -> RE: RHS Maneuverability Review (8/13/2006 9:48:45 PM)


quote:

ORIGINAL: Terminus

2nd generation night-fighters (Beaufighter and Black Widow) shouldn't get Maneuverability ratings like bombers, though I agree with you on 1st generation (Blenheim, Havoc and Ventura).


The effect of having two engines rather than one is to decrease the maximum roll rate and (usually) to increase weight (relatively speaking). You end up with decreased roll rate (due to the weight of the engines out on the wings), decreased sustained climb and operating altitude (from the reduced power to weight ratio), increased dive speed (because your CD was reduced), decreased maximum speed (more parasitic drag and less power to weight), decreased power to weight (meaning you couldn't accelerate as fast), and reduced turn rate (due to increased wing loading). The only one of these that you can't estimate from the published parameters is roll rate, which you can guestimate.

4E bombers were limited to about 3 Gs rather than 6 (as in fighters), so the maximum and sustained turn rates were halved.

I hope that helps.



Nicholas Bell -> RE: RHS Maneuverability Review (8/13/2006 9:59:23 PM)

    El Cid-

Don't forget to run the tests for yourself if you don't beleive me.  Bomber manueverability has no impact on combat resolution.  Cruise speed does.  Just set the the values to zero in a test run and you'll see.



el cid again -> RE: RHS Maneuverability Review (8/14/2006 2:29:48 AM)

quote:

ORIGINAL: Mifune

Cid, just so I can understand. On your current proposal, how would your formula look?




[ (Speed / 20) + (ROC/250) + (Wing Loading/x) + (Power Loading/y)]

all divided by Square Root (Number of Engines)

Exception 1: Two engines on the same axis count as one.
Exception 2: 3 + engine planes double the denominator.

Where x and y are values not yet determined so that the loadings will end up in the indicated range.



el cid again -> RE: RHS Maneuverability Review (8/14/2006 2:35:37 AM)

Spence: Black Mamba first brought the Ventura and specs in the game to my attention. We have since modified its range - and now also an up engined variant with even more range. We gave the initial version its ability to carry torpedoes and depth charges on appropriate missions as well. I don't remember what happened to speed and ROC - but it was checked - and so hopefully is also right. I saw a photograph somewhere of a plane attacking a Japanese aircraft - albiet a 2E one - with notes similar to your remarks. I think the plane may be better modeled now (in no less than 3 variants - one of them a night fighter if I remember right) - but under this proposal all versions will end up with a higher maneuverability rating relative to 1E and 4E aircraft.



el cid again -> RE: RHS Maneuverability Review (8/14/2006 2:38:12 AM)

Herwin: You may be helping. You may, for example, have come up with a justification for doubling the 4 engine divide by factor.

How can roll rate be "gestimated" in any consistent and relatively accurate sense?



el cid again -> RE: RHS Maneuverability Review (8/14/2006 2:45:54 AM)


quote:

ORIGINAL: Nicholas Bell

    El Cid-

Don't forget to run the tests for yourself if you don't beleive me.  Bomber manueverability has no impact on combat resolution.  Cruise speed does.  Just set the the values to zero in a test run and you'll see.



This does not appear to be correct. First of all, we have an official Matrix statement that maneuverability is the primary factor in air combat. Second, we have two different test beds (at least) using stock, CHS and RHS data, that seem to indicate otherwise.

Note, however, that test results are very hard to interpret without vast numbers of test runs, UNLESS you have the ability to control the "seed."
Matrix code does NOT duplicate the "identical" run each time - but generates a completely different random number each pass - even from the same starting point. ONLY a very unusual editor PLUS knowledge of where the seed it, used on each pass, permits accurate testing. This long confused me - until someone who does run such "fixed" tests - advised me. I do not doubt that everyone suffers from test result confusion as much as I did if they are not addressing this factor. There are likely other factors equally as obscure.



Mike Scholl -> RE: RHS Maneuverability Review (8/14/2006 2:47:39 AM)


quote:

ORIGINAL: herwin


quote:

ORIGINAL: Terminus
The effect of having two engines rather than one is to decrease the maximum roll rate and (usually) to increase weight (relatively speaking). You end up with decreased roll rate (due to the weight of the engines out on the wings), decreased sustained climb and operating altitude (from the reduced power to weight ratio), increased dive speed (because your CD was reduced), decreased maximum speed (more parasitic drag and less power to weight), decreased power to weight (meaning you couldn't accelerate as fast), and reduced turn rate (due to increased wing loading). The only one of these that you can't estimate from the published parameters is roll rate, which you can guestimate.


Don't quite understant the "power-to-weight" portion. A single engine has to power it's own weight and that of the entire airframe. Twin engines have to power their own weight, but only half that of the airframe. Power-to-weight would be particular to the individual design. The Mosquito had a quite high power-to-weight ratio (and speed), while the C-47's was fairly low (especially when you add in cargo). I don't see this portion of your data as being valid. Too much dependent on the individual design.



el cid again -> RE: RHS Maneuverability Review (8/14/2006 3:01:02 AM)

It does not matter - because power to weight is a strict function.
Mike is correct - a 2E plane may have a very low power to weight value - and transports in particular generally do. It may also be very high - and something like a P-38 must be in that range. But a function which divides weight by power is going to work out the actual value - regardless of what it is. I think the quoted comments were meant to refer to a restricted data set involving only fighter type planes. Even so, it would surely depend on the exact power and weight - any such generality even if true would have theoretical and probably actual exceptions. But since we are dealing with functions, they will produce values exactly proportional to the values we plug in - so each plane gets its due - as it were. What we are trying to do is figure out a better function - and the problem I think lies in the "divide by number of engines" part - in spite of the fact that probably is a valid factor. Ideally we would just look at pure performance statistics - speed - ROC - loading - name it - and ignore configuration altogether. But it does not appear that is quite valid; configuration seems to matter. P-38 is fabulous - but it is not as good as a single engine plane of the same statistics would be - in terms of maneuverability - while it is somewhat more likely to survive if it suffers fatal engine damage. A 4E plane that had the same statistics as a P-38 would still not be as manueverabilt - but it woul be even more survivable if an engine were hit. [I would prefer to be wrong about this too: just using performance data would be a cleaner function - if only it were also an accurate model]



herwin -> RE: RHS Maneuverability Review (8/14/2006 11:27:35 AM)

Remember this post? WWII Air Combat Model

That should give you some insight into your questions.



herwin -> RE: RHS Maneuverability Review (8/14/2006 12:11:15 PM)


quote:

ORIGINAL: el cid again

Herwin: You may be helping. You may, for example, have come up with a justification for doubling the 4 engine divide by factor.

How can roll rate be "gestimated" in any consistent and relatively accurate sense?


It gets rather complicated. Since turns and rolls involve the same forces, a plane that flips into a turn quickly does so because it rolls quickly. A roll is produced by deflecting the ailerons (involving muscle power in earlier and lighter aircraft), and adjusting the tail surfaces for control. You're generating angular motion around the forward axis of flight, so you have to overcome angular momentum. Two and four engined aircraft have much larger angular momenta, both due to sheer mass and the engines out on the wings, so roll acceleration is slower. In-line engines spin the crankshaft, while radial and rotary engines spin the engine, so they possess more angular momentum in a specific direction to start with--this is the reason your roll acceleration is different in the two directions of roll with radial/rotary engine fighters.

I had to model this stuff for my PhD thesis, but I was concerned with bat aerodynamics. Bats are not little aircraft--they can do impressive things with their wings that even birds can't.

I suspect you can find maximum roll rates and roll accelerations in the technical data for some typical WWII planes. Extrapolate from there.

One other thing--maximum sustained angular rate of turn takes place at a moderate speed. This is because it involves a combination of lift to remain airborne and lift to turn. The fast the aircraft flies, the more lift is available to turn, but the power requirements to maintain a given angular rate go up even faster. The Zero had muscle-powered control surfaces, so it became hard to control at high speed.



herwin -> RE: RHS Maneuverability Review (8/14/2006 12:13:21 PM)


quote:

ORIGINAL: Mike Scholl


quote:

ORIGINAL: herwin


quote:

ORIGINAL: Terminus
The effect of having two engines rather than one is to decrease the maximum roll rate and (usually) to increase weight (relatively speaking). You end up with decreased roll rate (due to the weight of the engines out on the wings), decreased sustained climb and operating altitude (from the reduced power to weight ratio), increased dive speed (because your CD was reduced), decreased maximum speed (more parasitic drag and less power to weight), decreased power to weight (meaning you couldn't accelerate as fast), and reduced turn rate (due to increased wing loading). The only one of these that you can't estimate from the published parameters is roll rate, which you can guestimate.


Don't quite understant the "power-to-weight" portion. A single engine has to power it's own weight and that of the entire airframe. Twin engines have to power their own weight, but only half that of the airframe. Power-to-weight would be particular to the individual design. The Mosquito had a quite high power-to-weight ratio (and speed), while the C-47's was fairly low (especially when you add in cargo). I don't see this portion of your data as being valid. Too much dependent on the individual design.


Bigger airframe. The highest power to weight ratios were for small single-engined interceptor fighters.



el cid again -> RE: RHS Maneuverability Review (8/14/2006 7:17:19 PM)

Regretfully, finding roll data for a few planes, and "extrapolating from there" is not going to work. It violates CHS/RHS standards for data - and it is probably not going to be valid either. Different manufacturers don't do things the same way, and some radical planes (J7W comes to mind) probably are very different in how they behave than anything we would be looking at. [There is a tiny plane in Anchorage of similar configuration - and it is almost impossible to describe how it can fly - you have to fly it to begin to understand the impact of a canard]. If we cannot come up with a theoretically valid way to determine roll rate from data that is available, we cannot use it. I think arguments would be endless if we tried to estimate this value - and there would be no rational way to settle them either. People would be sure I was a JFB or an AFB if their pet plane was not better than others.



herwin -> RE: RHS Maneuverability Review (8/14/2006 10:32:38 PM)

quote:

ORIGINAL: el cid again

Regretfully, finding roll data for a few planes, and "extrapolating from there" is not going to work. It violates CHS/RHS standards for data - and it is probably not going to be valid either. Different manufacturers don't do things the same way, and some radical planes (J7W comes to mind) probably are very different in how they behave than anything we would be looking at. [There is a tiny plane in Anchorage of similar configuration - and it is almost impossible to describe how it can fly - you have to fly it to begin to understand the impact of a canard]. If we cannot come up with a theoretically valid way to determine roll rate from data that is available, we cannot use it. I think arguments would be endless if we tried to estimate this value - and there would be no rational way to settle them either. People would be sure I was a JFB or an AFB if their pet plane was not better than others.


Oh, God... All those books are in America. Roll rate involves angular momentum, so high aspect ratio wings are bad and engines on the wings are bad.

"At 160 mph (260 km/h), A6M2 had a roll rate of 56 degrees per second." (from Wikipedia)

Spitfire I roll rate was 140 deg/sec. (http://www.aviation-history.com/)

P47D: 85 degrees per second.

P47N: 100

P38--a slow roller until the L model.

See also Roll Rates

For interesting figures see some guesstimates, it appears.

The first six below are from Perkins and Hage and are reliable.

P-47: 71 at 250 knots (per guesstimates, F6F, F4F, SBD, P-39D, Ki84, A6M3, and A6M5 similar, FM2 about 90)
P-38: 78 at 257 knots
P-51B: 98 at 260 knots
P-40: 134 at 314 knots
Spitfire V: 150 at 176 knots
FW-190: 151 at 226 knots

More guesstimates.
TBF: about 40 at 250 knots
F4U about 120
A6M2 about 50
Ki43 about 55
Bf109 about 85-90
Bf110C about 45
Spitfire V and Hurricane about 85-90
I don't believe the early P38 figures as it was comparable with the Bf110.
D3A and B5N about 33
B25H about 36
B17G about 10

The helix angle (pb/2V) is a constant times the airspeed up to the point that the ailerons start to flex or are too stiff to move. (p is the roll rate in radians per second, is the airspeed in feet per second, and b is the wing span in feet) The minimum acceptable value for the helix angle was about 0.07 for bombardment and transport aircraft and 0.09 for fighters in WWII. Source. About 125 degrees per second at 250 knots corresponds to 0.09 for a 30 foot wingspan, which means most WWII fighters were deficient.

You might find the following interesting: NASA history of aircraft




Herrbear -> RE: RHS Maneuverability Review (8/15/2006 7:15:05 AM)

quote:

ORIGINAL: el cid again

quote:

ORIGINAL: Mifune

Cid, just so I can understand. On your current proposal, how would your formula look?




[ (Speed / 20) + (ROC/250) + (Wing Loading/x) + (Power Loading/y)]

all divided by Square Root (Number of Engines)

Exception 1: Two engines on the same axis count as one.
Exception 2: 3 + engine planes double the denominator.

Where x and y are values not yet determined so that the loadings will end up in the indicated range.


When determining the power load for a 2 engine plane would it be the weight/2xengine horsepower? For example, if a 2 engine plane had 2 1000hp engines and weighed 26000, would the power load be 26000/2000 = 13 lbs/hp?


Also, isn't the more manueverable plane the one with the lower power load figure? So if you were adding power load into the equation, how do you account for lower is better?

Thanks Sid.



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