Kawasaki Ki 61 with Merlin or other engine?

[eagledad]

Hi Greg
As I wrote, the data is For what it is worth. It says in the introduction in the TAIC Manual no 1 introduction, that when it came to performance calculations "it is the policy of TAIC to give the Japanese Aircraft Performance every benefit of the doubt within reasonable limits." I guess I am not surprised that the calculations would be off by some amount.

I thought the data might be of use in helping to draw conclusions on an alternatively powered Ki-61. If it is not of use, so be it.

Cheers Greg!

Eagledad.

 

[Admiral Beez]

You could fit it with a Merlin, and it would have been a decent airplane. But that would require some serious design and modification that would not pay any dividends because the neither the U.S.A. nor any other country was going to adopt the Ki-61 for their Air Force after the war. So, the main questions for such modification would be…

Good info and points. What of the other inline engines available, to the Axis? There's the Hispano-Suiza 12Y that was licensed in Czechoslovakia (for the Avia B-534) and in the USSR as the successful Klimov M-105. There's the Junkers Jumo 211 and later 213 from the Fw 190D.

 

[GregP]

Not putting down your post though, on second reading, it sort of sounds like it. Unintentional, if so.

I have a TAIC book of Japanese planes. Most of the TAIC data do not agree with the "accepted" performance numbers that would later become widely accepted. They aren't too far off, and I assume having some estimated data when you went into combat was MUCH better than having no data.

 

[eagledad]

No offense taken Greg!

Cheers

Eagledad

 

[MiTasol]

That would entail a full engine mount, fitting, connection, wiring and cowling re-design. Seems REALLY unlikely just for curiosity.
But damn, if that isn't a good-lookin' machine

AND the thrust line would be way higher which would entail a string of consequential modifications to correct that (or a deep chin if the engine mounted low enough for the same thrust line)

 

[wuzak]

AND the thrust line would be way higher which would entail a string of consequential modifications to correct that (or a deep chin if the engine mounted low enough for the same thrust line)

I assume that the Ha 40/Ha 140 engine rotated the same direction as the DB 601 they were based on, so torque reactions may be an issue for the airframe in the same way it was for the Hispano HA-1112, the Merlin rotating in the opposite direction.

 

[MiTasol]

I assume that the Ha 40/Ha 140 engine rotated the same direction as the DB 601 they were based on, so torque reactions may be an issue for the airframe in the same way it was for the Hispano HA-1112, the Merlin rotating in the opposite direction.

Possibly though there were Merlins that rotated in each direction. Why the Spanish chose the particular model they did always confused me. Maybe they had a Brit on the design team who was either welded to Brit standards or who followed the first law of Brit aircraft design (why make it easy when you can make it bloody near impossible).

 

[SaparotRob]

Possibly though there were Merlins that rotated in each direction. Why the Spanish chose the particular model they did always confused me. Maybe they had a Brit on the design team who was either welded to Brit standards or who followed the first law of Brit aircraft design (why make it easy when you can make it bloody near impossible).

...and weird.

 

[Shortround6]

Possibly though there were Merlins that rotated in each direction. Why the Spanish chose the particular model they did always confused me. Maybe they had a Brit on the design team who was either welded to Brit standards or who followed the first law of Brit aircraft design (why make it easy when you can make it bloody near impossible).

They may not have had a lot of choice.

from wiki;

The final variant was the HA-1112-M1L Buchón (Pouter), which is a male dove in Spanish. It first flew on 29 March 1954 with a 1,600 hp Rolls-Royce Merlin 500-45[4]​ engine and Rotol propeller, both purchased as surplus from the UK.

What Merlins were available in 1953-54 surplus (cheap) in the quantity needed?

 

[wuzak]

What Merlins were available in 1953-54 surplus (cheap) in the quantity needed?

Apart from engines and spares for the Hornet, almost all engines would be RH rotation. And only half those for the Hornet would be LH rotation.

There were also contra props for the Sturgeon, but only 28 of that aircraft were built.

 

[Ivan1GFP]

Gentlemen

We have the calculated TAIC data for the Tony 2. That shows potentially what the airframe could do with a more powerful engine. The calculations are based on the use of the Ha-140 which I believe is based on the DB-605. Perhaps one could guess from that what type of performance a Merlin powered Ki-61 would have.

I agree with all that has been said before, with jets on the horizon, and shrinking military budgets, any research on an uprated Tony would be way down the list of military research priorities.

I have attached TAIC data for the Tony 2 (and a few other Japanese Aircraft)

FWIW

Eagledad
Eagledad

Hello Eagledad,

I believe the problem with this estimate of performance for Ki 61-II is due to TAIC lack of information at the time about the Ha-140 engine. They made the assumption that the engine was comparable in performance to the German versions of the DB 605 which it was not. Its altitude performance was quite inferior.

For our purposes in this discussion, it is useful because I believe it gives a pretty good idea of how the Ki 61 might have performed with a DB 605 engine swap.

- Ivan.

 

[GregP]

The Ki-61-I-KAIc had an Ha-40 engine of 1,159 hp and had a top speed of 366 mph (590 km/h) at 16,000 feet (5,000 m). It came in at 7,650 pounds gross weight and had a climb rate of 2,990 feet per minute (15.2 m/s). The Ki-61-II had an Ha-140 engine which was expected to have 1,500 hp. The wing had 10% more area as well. Only eight prototypes were fitted with Ha-140 engines.

There are well-understood formulas for predicting the speed of an airframe with no changes other than more power added. If we plug in the 1,500 hp to the Ki-61-I-KAIc airframe, we'd expect 399 mph as the new top speed. But, the Ki-61-II had 10% more wing area, so the actual top speed would be slightly less. Let's estimate 75% of the predicted change, for a speed of 391 mph if the Ha-140 was working well.

If we keep the weight at 7,650 pounds (3,470 kg) and go from 1,159 hp to 1,500 hp, we'd expect the rate of climb to go up to 4,460 feet per minute. Since the wing had 10% more area, I'd assume the weight went up. For an initial assumption, say the weight went up by 50 pounds. We'd still expect the rate of climb to go up, but only to 4,432 feet per minute or so from the formula.

These are useful performance changes in speed and rate of climb. The fact that they didn't pursue this indicates to me that the Ha-140 engine was not going to be easily debugged to become a reliable powerplant. Instead, they modified the Ki-61 airframe to accept a 1,500 hp radial engine in what can only be described as a great engineering feat. The drag went up, but it STILL made 360 mph and the climb rate was materially increased from the Ki-61-I.

I'd bet that if they had access to real DB 605 engines, they would have stuck with the inline and would have had a better airplane than the already-formidable Ki-100. It was not to be, but the potential was there. Making copies of a machine is fraught with difficulties. The Italian DB copies were pretty good, but not quite as powerful as factory DB engines, too. At least they were reliable. But, then again, the Italians had MUCH better access to the DB factory, personnel and plans than the Japanese did.

 

[Thumpalumpacus]

...and weird.

At least they didn't stick a turret on it.

 

[Ivan1GFP]

Hello GregP,

There are actually a LOT of problems with the data that you are using in your calculations.
First of all, the aircraft that you are describing as the Ki 61-I-KAIc didn't really exist as such or if it did, it didn't exist as that for long.
That designation was mostly a post-war assumption of how the designation should have been. The actual designation was Ki 61-Id.
The -I-KAIc is more consistent, but that isn't how it actually worked out.

The Ki 61-II initially had a wing that was redesigned but after only a couple prototypes reverted back to the same wing as the Ki 61-I, so there was no actual increase in wing area for the majority of the airframes produced. The reversion was a change in airframe and thus the designation is Ki 61-II-KAIa for most of the actual aircraft produced.

As for speed estimates, the engine power numbers you are using are for Take-Off power or Sea Level performance.
As you know, the power at altitude is actually what is important for maximum speed and this is where the Ha-140 was a bit worse than expected.

Here are some numbers for comparison purposes: (Some are as you have already quoted.)
Ki 61-Id
7650 pounds loaded weight
1160 HP @ 2500 RPM Take-Off +330 mm Boost. Maybe this can be considered WEP as TAIC did.
1040 HP @ 2400 RPM Maximum @ SL +240 mm Boost.

1100 HP @ 2400 RPM Maximum +240 mm Boost @ 4200 meters. This is critical altitude.
Note how this altitude compares with the German DB 601 versions.

Ki 61-II-KAIa
8433 pounds loaded weight.
1500 HP @ 2750 RPM Take-Off +480 mm Boost. Maybe this is WEP.
1350 HP @ 2650 RPM Maximum @ SL +380 mm Boost.

1250 HP @2650 RPM Maximum +380 mm Boost @ 5700 meters. This is critical altitude.

As you can see, power at altitude isn't really all that good.

- Ivan.

 

[SaparotRob]

At least they didn't stick a turret on it.

I'll bet they thought about it.

 

[GregP]

Actually, Ivan, there aren't a lot of problems with my data. I made a first order estimation, and it is pretty good for a first order calculation. To make it better, I'd need the power curves for the Ha-40, Ha-140, and the Kasei radial. Then I could input the Ha-40 hp at the altitude where the top speed was actually realized and then put in the Ha-140 hp at the same altitude, and deduct for fuel burn for weight .... and come up with a better estimate.

Naaaaa ... too much work unless I am trying to be super accurate, as in am I actually interested in predicting the exact performance? I'm not, what I did was to apply a standard formula to decide whether the gains might seem reasonable as something to pursue. Seem to me like they were. But the 1,500 hp wasn't available at all altitudes, so the actual rate of climb would be less. Offhand, I'd guess it would be on the order of 3,600 fpm for the Ha-140, assuming it was running reliably. That would be a desirable increase from the standpoint of the pilots.

But that airplane is a "what if." That is, it never went into service. They only made 8 or so Ki-61-II prototypes and only 99 Ki-61-II Kai production airplanes, not enough to get excited over even if they were being sent against your unit. So, I was really just trying to decide whether or not it might have been worth trying to "fix" the Ha-140. I think it was, but the war situation and the resources available to Kawasaki at the time might make the decision to proceed not a practical one. It seems that way in real life in the actual war.

As it turned out, the Ki-100 was what they considered a better option and the real life Ki-100 was a good airplane.

 

[Ivan1GFP]

Helllo GregP,

How did the Kasei come into the discussion?

The basic point I was trying to make was that although the Ha-40 was making similar power at altitude as it was at sea level, the Ha-140 was not. I am not sure as to why but the effect was an aeroplane that wasn't significantly faster but weighed a lot more and was flying around with the same wing.

I have also wondered what would happen if the TAIC were correct and the Japanese really did use Take-Off settings for WEP. They may not have been able to get the additional boost at altitude, but the additional RPM might have made a difference.

The Japanese didn't CHOOSE to stop manufacturing the Ki 61-II-KAI. The US bombing took out the plant that was making the Ha-140 engines, so they didn't really have the choice....
They still had headless airframes but no more Ha-140 engines were going to be delivered without the factory, so they had to do something. The Japanese production runs tended to be pretty small for many aircraft, so 99-100 nice running Ki 61-II would have been a significant addition. If they had engines for all the airframes initially produced, it would have been about the same production numbers as the J2M3 series.
As for the actual speed of the Ki 100 Type 5 fighter, there is evidence that it was considerably faster than the 360 MPH normally claimed for it. The results were good, but that has more to do with the quality of the airframe and reliability of the engine rather than any spectacular feat of engineering in my opinion. It was an aircraft with the poorer aerodynamics than the Ki61-II but the same level of power and a couple hundred kilos less weight. As an example to illustrate, the example in a British museum never even had the coolant radiator controls removed even though the coolant radiator obviously isn't there any more.

- Ivan.

 

[GregP]

Well, the Kasei came into the discussion because of poor toilet training a as kid. I SHOULD have said Kinsei, but typed Kasei instead. Mea culpa.

I was really talking about the Ha-140 versus the Ha-40. The Ha-140 was never a reliable engine, and the Ha-40 was not really very powerful. It made something like 1,020 hp at about 12,000 feet. The Ha-140 was so unreliable that about half were returned to the factory for rebuild after being flown for the first time. Not an auspicious beginning, to be sure.

Add lack of Ha-140 reliability to the bombing damage and you come up with a lot of Ki-61 airframes with no engines. I consider the adaption of the Kinsei to be one of the better Japanese aeronautical engineering feats of the war. They didn't have something simple, like adapting a Ryan ST to a small Kiner radial; the Kinsei was much bigger and the mating of it to the Ki-61 airframe was quite well done.

Let's say you and I disagree on the cleverness of the Kinsei being fitted to the Tony airframe and let it go at that. In the relative scheme of WWII things, it isn't all that important. If we're going to have a back and forth discussion of differing opinions, I'd choose something with more import than the Ki-61 / Ki-100. They only made about 2,803 Ki-61's and about 395 Ki-100s, so it isn't as if these were heavily encountered. The Japanese likely wished they had more Ki-100s.

Cheers, Ivan.

 

[nuuumannn]

A coupla things, the Ki-61 was probably not a good candidate for re-engining unless major modification was done to the front end. Unlike in other fighters, the engine mounts were a part of the forward fuselage, which means a Merlin is out, unless it works upside down.

DSC_6614

In saying that, the Ki-61 was re-engined.

Ki-100

The first 200 or so Ki-100s were Ki-61s with a new front end.

 

[Mike Williams]

A coupla things, the Ki-61 was probably not a good candidate for re-engining unless major modification was done to the front end. Unlike in other fighters, the engine mounts were a part of the forward fuselage, which means a Merlin is out, unless it works upside down.

View attachment 629860DSC_6614

Interesting photo. Do you have any further info on those airframes?