He 100 in service, but with caveats

[Shortround6]

Trying to stuff a BMW 801 into the He 100 would be quite a trick.
It is a small (tiny?) aircraft and you are trying to swap a 1300lb engine for 1900-2000lb engine?
And taking out all the cooling crap that is behind the CG?

Granted with coolant systems out of the wing you get room for more guns to make up for the fact you don't have the hub mounted cannon anymore.

 

[GTX]

It would be somewhat akin to the Ki-61 to Ki-100 path one suspects, especially when one considers the engines involved.

 

[Shortround6]

It would be somewhat akin to the Ki-61 to Ki-100 path one suspects, especially when one considers the engines involved.

Yes but the Ki 100 lost about 19mph in speed compared to the HA-140 engine. They did very well but it was also 1944-45 and not 1938-40.
The Ki-100 did a very good job with the exhaust pipes/thrust. Are you going to get the same type of installation in 1939-41.

Everything on the HE 100 was about cutting drag, Once you start changing things the drag starts coming back.

 

[GTX]

I'm not arguing from the POV that such a BMW powered He-100 would necessarily be better. Rather, what would take in order to get the He-100 into operational service.

 

[tomo pauk]

It would be somewhat akin to the Ki-61 to Ki-100 path one suspects, especially when one considers the engines involved.

BMW 801C/D were at 1055 kg dry, the late Kinseis were at 610 kg. Our overseas friends will call it 1000 lb difference
Late Kinseis were still lighter than the Ha 40 (= copy of DB 601A) by 76 kg - 160-170 lbs lighter.

Bottom line was that people at Kawasaki were at an much easier job to do the engine swap they did, than what awaits the people at Heinkel to make the DB-601 to BMW 801 swap.

 

[Shortround6]

What it takes is to be better than the competition in 1938-40. Not what could be done in 1944.

The He 100 was using the best engine the Germans had at the time, in a smaller airframe than the Bf 109, using a trick cooling system.
Using a 2nd rate engine (Hispano) or anything else that compromises it drops it much closer to the 109 and it looses it's appeal.
Using a radial means no engine mounted cannon which means jumping through hoops to get the firepower back up.
even with the cooling system taking out you only have a 156sq ft wing to put the landing gear, fuel and guns into. About 90% of the wing of the 109 and they weren't trying to put fuel in wing.

Edit, the He 100 used the wing root guns because they didn't have room in the fuselage for the pair of 7.9mm machine guns to fire over the top of the DB601 engine. they were using a shallower fuselage than a 109 (and that was pretty shallow to begin with).

 

[GrauGeist]

I'm not arguing from the POV that such a BMW powered He-100 would necessarily be better. Rather, what would take in order to get the He-100 into operational service.

It would take considerable rework to fit an 801 onto the He100's frame.

Two radial engines were trialled in a Bf109 - the first was a Bf109 prototype (V21) with a P&W R-1830 in 1938. Aparently, it was not a big success as little was recorded about it's testing or results.
The second, was a BMW801A fitted onto a Bf109F (often referred to as a Bf109X) in 1940 and the resulting performance was problematic and testing was discontinued after two years.

With the He100 being smaller than the Bf109, I can imagine that a swap to an 801 would not have any better results.

 

[tomo pauk]

What it takes is to be better than the competition in 1938-40. Not what could be done in 1944.

Agreed.

Using a radial means no engine mounted cannon which means jumping through hoops to get the firepower back up.
even with the cooling system taking out you only have a 156sq ft wing to put the landing gear, fuel and guns into. About 90% of the wing of the 109 and they weren't trying to put fuel in wing.

He 100 was already with fuel tanks in the wing.
Japanese, as well as people where the R-1830 was available, will probably go with HMGs in the wings. Possibly the Type 99-1 might fit for the IJN needs, to fire outside of prop disc, IJA might find the Ho-5 attractive (can be synchronized).

 

[Shortround6]

He 100 was already with fuel tanks in the wing.

yes and the existing fuel tanks are right where you want the gun breeches to go.
We have problem with the whole tight design pre armor, protected tanks thing.
Japanese may not care but they didn't thing much of the high wing loading to begin with.
If you do want protection for the fuel tanks flat skinny tanks are heavy for the amount of fuel carried.
The further out you carry the fuel worse it gets.
moving the fuel outboard may affect roll response, depending on how much fuel is left.

Japanese, as well as people where the R-1830 was available, will probably go with HMGs in the wings. Possibly the Type 99-1 might fit for the IJN needs, to fire outside of prop disc, IJA might find the Ho-5 attractive (can be synchronized).

Japanese and who ever had access to the R-1830 before the middle of 1940, are dealing with single speed superchargers. R-1830 customers in 1939-40 may have a fuel problem. Do they have 100 octane or not?
He 100 in Japan with a Kinsei 40 series engine in 1940-41?

 

[tomo pauk]

yes and the existing fuel tanks are right where you want the gun breeches to go.

Yes and no, the outboard fuel tank (4 tanks were total) can be shorter so the breech can fit. Ammo can go in front of the main spar. The extra fuel tankage must go behind the pilot.

Japanese and who ever had access to the R-1830 before the middle of 1940, are dealing with single speed superchargers. R-1830 customers in 1939-40 may have a fuel problem. Do they have 100 octane or not?

1-speed S/Cs certainly. Availability of the 100 oct fuel was not guaranteed, though, especially for the Axis. 91-92 oct for the Japanese.

He 100 in Japan with a Kinsei 40 series engine in 1940-41?

Much better performance than what IJN, let alone IJA was flying back then.

 

[Shortround6]

1-speed S/Cs certainly. Availability of the 100 oct fuel was not guaranteed, though, especially for the Axis. 91-92 oct for the Japanese.

Problem with the single speed superchargers on the radials is that peak power was between around 8,000ft and 12,000ft.
Depends on engine and gear ratios. With the 91-92octane fuel (P & W was selling a lot engines set up for 91 octane, not 87) the power may be lower on the P & Ws.
The DB 601 has got a bit more power a bit higher up and with anything close to a decent cooling system a lower drag engine installation than the radials of the time.

 

[tomo pauk]

The DB 601 has got a bit more power a bit higher up and with anything close to a decent cooling system a lower drag engine installation than the radials of the time.

Look at that from non-German standpoint in 1940-41: a good, if a bit draggy radial they actually have is a darn sight better than a modern V12 they don't have.

 

[SaparotRob]

That's kind of hard to argue with.

 

[tomo pauk]

Ernst Heinkel didn't received the news of defeat of the He 112 vs. Bf 109 with joy, to say at least
We can see at least two things here: he had the 109 in his sights (figuratively speaking, ofc) and he distributed tasks to his 'deputies' to find the way of making the 'Super fighter' lighter and much more aerodynamic than the 109. He was also keen to have the DB 601 powering his fighter, even if the 601 still had some time ahead itself before the series production.
Ad-hoc translation by yours truly:

 

[Engineman]

Ernst Heinkel didn't received the news of defeat of the He 112 vs. Bf 109 with joy, to say at least
We can see at least two things here: he had the 109 in his sights (figuratively speaking, ofc) and he distributed tasks to his 'deputies' to find the way of making the 'Super fighter' lighter and much more aerodynamic than the 109. He was also keen to have the DB 601 powering his fighter, even if the 601 still had some time ahead itself before the series production.
Ad-hoc translation by yours truly:

View attachment 701593

Great Document.
It is interesting that the majority of later Western WW2 fighters got larger than the early 109. Of course, they generally had more power than the DB 601 A.
In Germany, they did get more power from the 601, up to 1475 PS from the DB 605 A in service by early Summer '42 but, very quickly limited to the previous power of the DB 601 E due to materials weaknesses and tech problems. At the same time, other tech problems had crippled the 601 E itself and, the uprated 601 N previous to that!
E. Heinkel would have shown genius if he had opted for a slightly larger fighter, with great aerodynamics and the DB603. Could have worked-out if the 603 development had been pushed.

Eng

 

[Shortround6]

Ernest may have been a bit too obsessed with speed.

He was aiming at the near target and not the future. Current thinking (early 1937)for the 109 was two mgs and single motor cannon. They could not get the motor cannon to work and there is no mention if Heinkel and the boys did either. Turns out the 109 had a bit (not much) more room for extra guns or locations.
No mention is made of range but less drag does mean more range for same fuel.
Reducing drag from smaller tail surfaces is commendable

Granted the later He 112s did get smaller tails.

Ernest bet on the wrong horse with cooling system.
Everybody was using plain water with Glycol being hyped. Glycol had problems of it's own. The evaporative cooling (steam) looked good in theory.
Glycol was one part of high temperature cooling. The other was using pressurized water in a sealed system but not turning to steam (at leas not more than few percent).
All three have less drag than plain water with evaporative cooling (steam) having the lowest drag but at the cost of the whole being a flying radiator that is exposed to gun fire.
Pressurized water and Glycol (or mixture) will be somewhere in-between and and may flip flop depending on exact temperature level used and mixture of the coolant.

 

[GrauGeist]

The He100 was simply too small (if there is such a thing) and was a dead-end for any upgrades like engines (as happened) or different weapon arrangements.

At least the Bf109 proved to be adaptable in the long run and the He112 did have room for changes, upgrades and what-not.

The He112B may have had performance comparable to that of the Bf109, causing the RLM dismiss it, but with it's heavier firepower and longer range, would have been an asset in the Battle of Britain.

 

[tomo pauk]

Ernest may have been a bit too obsessed with speed.

His fast aircraft of note (He 280, 100, 162, 219) were with pretty small wings/wing areas - probably he over-compensatsed after the He 112 ... debacle (wrt. lucrative military contact)? Even the He 112B was given a pretty small wing after the two earlier big wing sets were used on previous versions/prototypes.

He was aiming at the near target and not the future. Current thinking (early 1937)for the 109 was two mgs and single motor cannon. They could not get the motor cannon to work and there is no mention if Heinkel and the boys did either.

FWIW:

The He100 was simply too small (if there is such a thing) and was a dead-end for any upgrades like engines (as happened) or different weapon arrangements.

Keep it with DB 601/605 and it is okay.
Weapon set-up will need more thinking to be done, max might be probably three MG FFMs before we start hanging the gondolas under the wings.
Yak-3 was with even smaller wing than the He 100.

 

[Engineman]

The cooling system/cooling drag issues are quite involved. The concept of high temperature cooling seems to have been in the background for quite a few years before WW2 but, the resolution was slow to resolve. This stems back to air racing, where the simple lowest drag was very important and surface cooling of water coolant was possibly king. However, the simple unworkability of that in a fighter was unaccountably ignored.
Steam cooling, with the boiling and condensation of water was another blind-alley. The tightrope between superheated water and steam with large pressure variation appears to never have been mastered in an efficient aircraft application.
So, Glycol based high temp cooling came along. Engine companies seem to have ignored the fire risk, even though Rolls-Royce record the "spectacular" fires caused by glycol leaks in engine testing in the mid '30's. Additionally, the heat capacity of the Glycol was lower than water. Rolls-Royce report that changing from Glycol to 70/30 Water/Glycol mixture (with the Glycol as anti-freeze) gave cylinderhead metal temperatures considerably lower than with 100% Glycol, and removed the fire risk.
Taking the Water/Glycol mix with some higher pressures, allowed high temperature cooling, with good thermal properties. Amazes me that this took so long to sort!

Eng

 

[GrauGeist]

His fast aircraft of note (He 280, 100, 162, 219) were with pretty small wings/wing areas

The He280's wingspan was just two feet shy of the Me262's with a comparable wing area.