Ki-43 Hayabusa Performance

[CORSNING]

Ivan

I do not have all the facts at this time but I am guessing you are pretty
close my friend.

I believe Biff15 could enlighten us all in this particular instance.

 

[CORSNING]

Ivan,
I agree that stall speed is a very important in turning time, but unless
you are flying a later model P-38, stall and cut is not your best option.

 

[Ivan1GFP]

Ivan,
I agree that stall speed is a very important in turning time, but unless
you are flying a later model P-38, stall and cut is not your best option.

Hello Corsning,

I am not really sure what you mean by "stall and cut". Does that have something to do with using engine torque to improve your turn rate?

What I was really getting at was that with aircraft of this era, the Thrust to Weight ratios were down in the 0.1 to 0.2 range and none of these aircraft could sustain a turn at maximum G for very long and 15-20 seconds pulling G is a fairly long time. They needed to start a turn with enough speed so that even when the speed bled off during the turn, they would still turn at a reasonable angular rate limited by stall speed at the end. They also needed to start at a low enough speed so that the initial turn Rate which was limited by airframe and pilot load wasn't too poor either.

It is a pretty good assumption that just about everyone is limited by a G load of around 6 G but there are a lot more details I have never tried to collect data for that would be necessary for accurate calculations.

These days with Thrust to Weight easily exceeding 1.0, I am not really sure all the same rules apply to the same degree.

- Ivan.

 

[Laurelix]

Hello Laurelix,

I believe I found your error.
See the Bold Underline above.

Stall speed in INDICATED Air Speed does not change with altitude.
Stall speed in TRUE Air Speed increases.
Do you remember I asked earlier about entry and exit speeds from the turns?
At higher altitude, a turn can be entered at higher true airspeed and I believe that although the radius is larger, the turn may end up quicker. I have seen photographs of this with F-16 versus F-4, in which the F-16 made a larger radius turn but turned at a faster rate in degrees per second, but to be sure in this case requires a few calculations.
Intuitively it seems like it should work.

Hello Corsning,

Stall speed actually does need to be considered for minimum turn times.
The reason is that you want to have enough speed to be able to sustain a turn without encountering an accelerated stall (perhaps at 6G) but don't want to be going so fast that the turn has too great a circumference and increases time.
Centripetal force increases as speed increases according to M*V^2/R, so going a little faster also makes numbers worse if the load limit on the pilot is limited.
....And then the turn needs to finish with enough speed to still be abl to pull some reasonable G which is probably a lot less than the peak acceleration.
It is a pretty fine balancing act as I see it and probably why different pilots sometimes get different results if they started at different speeds.

- Ivan.

Yes same IAS, but the TAS is different. My bad.
Because you need to retain higher SPD, your turn radius increases and with less power at 4000m, the power to weight ratio also gets worse. This is why planes turn better at 1000m than they do at 4000m.

 

[Ivan1GFP]

Yes same IAS, but the TAS is different. My bad.
Because you need to retain higher SPD, your turn radius increases and with less power at 4000m, the power to weight ratio also gets worse. This is why planes turn better at 1000m than they do at 4000m.

Hello Laurelix,
Where did you get the idea that engine power is lower at 4000 meters than at 1000 meters?
The Ki 61-I with Ha-40 is a perfect example of just the opposite.
1040 HP @ SL
1100 HP @ 4200 meters.

I believe that would vary depending on the aircraft being discussed and also depends quite a bit on the Propeller.
Is the propeller optimal for the altitude? With comparable engines, the bigger propeller will work better at higher altitudes though 4000 meters isn't particularly high.
Parasitic drag and bleed of airspeed should also be lower.
As I see it, there are enough factors here that we are not likely to find accurate information for that it doesn't make sense to try to calculate using average values or assumptions, especially when experimental / observed data is available.

FWIW, I do a lot of these kinds of calculations for comparisons also, but I take the results as MY estimates and not as factual data.

- Ivan.

 

[CORSNING]

Hello Corsning,

I am not really sure what you mean by "stall and cut". Does that have something to do with using engine torque to improve your turn rate?


Hi Ivan, perhaps stall and cut are not the appropriate words to use. The following
is the only quote I could find from the mock combat between a P-38H and Spitfire
XIV. I do not remember the P-38 dominating. I remember it as the two were turning
at a stalemate. All the rest of the story seem accurate though. It went like this:

" During the late winter of 1944 occurred the famous dual between a Griffon-engine
Spitfire XIV and a P-38H of the 364th FG. Col. Lowell flew the P-38, engaging the
Spitfire at 5,000 ft. in a head-on pass. Lowell was able to get on the Spitfire's tail
and stayed there no matter what the Spitfire pilot did. Although the Spitfire could
execute a tighter turning circle than the P-38, Lowell was able to use the P-38's
excellent stall Characteristics to repeatedly pull inside the Spit's turn radius and
rid the stall, then back off outside the Spit's turn, pick up speed and cut back in
again in what he called a 'cloverleaf' maneuver. After 20 minutes of this at 1,000 ft.
altitude, the Spit tried a Split-S (at a 30-degree angle, not vertically down), Lowell
stayed with the Spit through the maneuver, although his P-38 almost hit the
ground. After the Spitfire pilot brock off the engagement and flew home. this
contest was witnessed by 75 pilots on the ground."

 

[CORSNING]

TAIC 154a TONY I
Using 92 octane fuel.
1,160 hp./T.O.
1,100 hp./12,600 ft. (3,840 m.)


Rene J. Francillon:
1,175-1,180 hp./T.O.
1,100 hp./3,900 m. (12,795 ft.)

Keep in mind that these figures are if using 92 octane fuel. Late in the
war many of the Japanese fighter groups were using tree-sap fuel of the
the 85-87 octane range.

Jeff

 

[Ivan1GFP]

TAIC 154a TONY I
Using 92 octane fuel.
1,160 hp./T.O.
1,100 hp./12,600 ft. (3,840 m.)


Rene J. Francillon:
1,175-1,180 hp./T.O.
1,100 hp./3,900 m. (12,795 ft.)

Keep in mind that these figures are if using 92 octane fuel. Late in the
war many of the Japanese fighter groups were using tree-sap fuel of the
the 85-87 octane range.

Jeff

Hello Corsning,

Your numbers are correct, however you are comparing different ratings.
You are comparing a Take-Off / WEP Rating at Sea Level and a Military Rating at Altitude.
Here are the rest of the numbers to put it into context:

Sea Level:
1160 HP @ 2500 RPM @ +330 mm Boost for Take-Off and presumably War Emergency Power.
(This is also listed as 1175 PS)
1040 HP @ 2400 RPM @ +240 mm Boost for Military Rating.

Critical Altitude: 4200 Meters (13,780 feet)
1100 HP @ 2400 RPM @ +240 mm Boost for Military Rating

Also, not that it makes much difference, but it should be listed as 91 octane fuel. 92 octane was the Navy standard.
Regarding critical altitude: The original DB 601Aa from which the Ha-40 was derived had a rated altitude of about 3700 meters. If the TAIC critical altitude is correct, then it goes against other documentation that states that the Japanese managed to improve the supercharger on the Ha-40 to almost match that of the DB 601A-1 at 4500 meters.

-Ivan.

 

[Ivan1GFP]

Hello Corsning,

I almost missed the Spitfire XIV versus P-38H combat description.
I have a guess as to what was happening but it is just a guess: P-38 was using Flaps to assist the turn but was bleeding so much speed with flaps that he could not use them continuously.

As for the Spitfire, this seems like a pretty tight spot. The two advantages I can think of are a higher sustained climb rate and a much faster roll rate. Seems like the Spitfire pilot never took advantage of those factors. I don't think the climb rate difference is enough of an advantage but there is no way that a P-38 without boosted ailerons could follow a Spitfire XIV in a roll.

- Ivan.

 

[Shortround6]

My favorite chart/diagram for arguments like this one is.
http://www.spitfireperformance.com/spit109turn.gif

Please note on the chart (calculated) that the Spitfire could manage a 13 second turn (in theory) at either 6 gs at at an 800 ft radius or around 5.25 to 5.4 Gs (?) at a 680ft radius at a slower speed.
The real fly in the ointment however is that the plane has to be descending at at over a 20 degree angle in order to maintain speed. ( a few degrees higher angle of descent for the higher G/faster turn).

Note that the Spitfire is calculated to sustain only a 3 G turn at a 1200ft radius in about 23 seconds (at 220-225mph true?) without losing altitude. Either faster or slower and the plane cannot maintain height pulling 3 Gs. Note also that the calculations show that for the same 23 seconds the plane can pull a high speed 5 G turn with a 2000ft radius (while descending at 7-8 degrees or a a 2 g turn of 706 ft radius and climbing at 4-5 degrees at near stall.

To have any real meaning (at least to me) turn times need a lot more information than is usually given. ( or it is assumed that the reader knows some of the parameters of the test without them being spelled out.)

 

[Ivan1GFP]

.....
Please note on the chart (calculated) that the Spitfire could manage a 13 second turn (in theory) at either 6 gs at at an 800 ft radius or around 5.25 to 5.4 Gs (?) at a 680ft radius at a slower speed.
The real fly in the ointment however is that the plane has to be descending at at over a 20 degree angle in order to maintain speed. ( a few degrees higher angle of descent for the higher G/faster turn).

Gentlemen,
The example from Shortround6 illustrates the bleed off in airspeed that I have been trying to describe.
In the first example, if it were a Level turn after several seconds, the Spitfire would not have enough energy to keep pulling 6G and have to loosen up (in terms of G Load) the turn. This example is trading altitude to replace the speed that is being bled off by increased drag in the turn.

FWIW (If my maths aren't too screwed up):
6 G Turn - 800 feet Radius - 13 Seconds - 264 MPH
5.25 G Turn - 680 feet Radius - 12.61 Seconds - 231 MPH
5.4 G Turn - 680 feet Radius - 12.43 Seconds - 234 MPH

- Ivan.

 

[CORSNING]

Hello Corsning,

Your numbers are correct, however you are comparing different ratings.
You are comparing a Take-Off / WEP Rating at Sea Level and a Military Rating at Altitude.
Here are the rest of the numbers to put it into context:

Sea Level:
1160 HP @ 2500 RPM @ +330 mm Boost for Take-Off and presumably War Emergency Power.
(This is also listed as 1175 PS)
1040 HP @ 2400 RPM @ +240 mm Boost for Military Rating.

Critical Altitude: 4200 Meters (13,780 feet)
1100 HP @ 2400 RPM @ +240 mm Boost for Military Rating

I pulled out my TAIC Manual No. 1. 154A-2 gives a war emergency rating off 1,100 hp.
at 12,600 ft. The engine rpm is not listed. It is the December 1944 report. Many aircraft
were updated in May of 1945.

Also, not that it makes much difference, but it should be listed as 91 octane fuel. 92 octane was the Navy standard.

TAIC says 92 octane. I am just saying...? I know that the IJNAF did have 100 octane fuel that
they used for experimental (testing?)work.

 

[CORSNING]

Gentlemen,

FWIW (If my maths aren't too screwed up):
6 G Turn - 800 feet Radius - 13 Seconds - 264 MPH
5.25 G Turn - 680 feet Radius - 12.61 Seconds - 231 MPH
5.4 G Turn - 680 feet Radius - 12.43 Seconds - 234 MPH

- Ivan.

The Ki.27-Ia/-Ib is the only WW2 monoplane front line fighter
that was capable of a 13 second 360 degree turn that I am
aware of. The next closest aircraft in that category would be
the A5M2/4 Claude somewhere in the 13+seconds category.

 

[Ivan1GFP]

Hello Corsning,

Regarding Ha-40:
First of all, I have no doubt that the 4200 meter critical altitude is correct.
I suspect this is another case of inconsistencies in TAIC data because I don't believe they conducted that many flights before engine failure grounded them. They also started with aircraft that were sidelined because they were unserviceable.

I am not so sure there actually was a WEP rating for the Ha-40 from what I can tell.
On the original DB 601Aa, the Take-Off rating at increased boost and RPM was for a duration of only 1 minute.
I don't know what the duration of the increased boost was longer for Ha-40 and whether it was long enough to be useful other than for Take-Off.
Also, if the engine is capable of 1100 HP at 4200 meters in Military Power, then it it should do better than that at a lower altitude and higher RPM and boost.
I have suspicions that TAIC assumed Ha-40 was a DB-601Aa equivalent just as they assumed the Ha-140 was a DB 605 equivalent.

Regarding 13 second turn times:
I am just using a simple physics formula here. I am pretty sure the numbers are correct.
This is NOT REALLY a 13 second 360 degree LEVEL turn because as Shortround6 described: The Spitfire is losing altitude at about a 20 degree angle in order to maintain airspeed. That was the point I was trying to get at: if Spitfire had to lost altitude to maintain airspeed, it obviously did not have the engine power to sustain this kind of turn rate and the level turn would not be as quick.

- Ivan.

 

[eagledad]

Gentlemen,

I found this document on J-Aircraft.com, as presented by the late Jim Long. About two-thirds down the document, there is a turn time of about 11 seconds at approximately 2000 feet.

FYI

Eagledad

 

[Ivan1GFP]

..... the military power for Sakae 21 is quite a bit closer, but please remember that for the Oscar, TAIC notes that the aircraft is capable of pretty high "Flash Performance" because the pilots apparently disregard the limits in the manual and get away with it.

Hello Eagledad,
Please note the comment by intelligence analyst at the bottom of the translation. It is probably where I saw the comment about Oscar's "Flash Performance".

- Ivan.

 

[CORSNING]

Eagledad,
I do not have office365 and am unable to see the document.
I do see that it would appear to be for the Ki.43-II which had
a better roll rate than the Ki.43-I but did not turn as tightly.

Ivan,
"Flash Performance"?

 

[fubar57]

Jeff, download the file and then convert to PDF....Convert DOC to PDF Online | Convert DOCX to PDF Online | Convert Word to PDF Online | Free online converter

 

[CORSNING]

Thanks for the Help George. I down loaded the site you posted.
I then tried again to view the document ED posted but I'm still
getting the message that I don't have Office.
Of course, I am not all that good with a computer yet.
It is just not letting me download.

 

[fubar57]

Give me a few minutes