He 100 in service, but with caveats

[tomo pauk]

Lets say that RLM greenlits the He 100 fighters for production in April 1939, with caveats/requirements:
- since the DB 601s are in short supply, Heinkel needs to find the alternative for the next 18 months of production (RLM is open for suggestions wrt. these alternatives)
- no evaporative cooling system(s)
- speed and endurance in ballpark with Bf 109E for starters
- guns' armament: at least one cannon + 4 MGs, or two cannons + 2 MGs

Heinkel has 3 months to have the prototype flying, and another month for another prototype.

Since I love the zero-sum game, feel free to alter the RLM purchases accordingly. Granted, 1-engined fighters are probably the cheapest and easiest to produce of all 1st line combat aircraft back then, so this will not hugely tax the German resources in the 1st place.

 

[GrauGeist]

The airframe of the He100 was designed exclusively for the DB601.

Using a Jumo211 would require quite a bit of rework, perhaps even a clean sheet design.

 

[GTX]

What if Heinkel followed the Focke-Wulf example and offered a version with a air-cooled radial instead thus avoiding the whole DB 601 supply and evaporative cooling issues:

 

[tomo pauk]

The airframe of the He100 was designed exclusively for the DB601.

Airframe does not have a vote here

Using a Jumo211 would require quite a bit of rework, perhaps even a clean sheet design.

No time for that. Better start thinkering about the installation of the Jumo 211, perhaps with the radiators of (obviously of the greater size) roughly in the place of where the pop-out auxiliary radiator was on the He 100s. Hopefully we'd get the German equivalent of the MC.202, speed-wise.
An easier to install engine should be the Avia-produced HS 12Y. This combo equals the VG-33 speed bracket, perhaps a bit better since the -31 on the VG-33 was a meh engine even among the HS 12Ys.

 

[Shortround6]

Just send somebody out with a pistol and shoot the H-S powered planes through the cylinder heads before you send any pilots up in them. Save the pilots.

Unless you can get your hands on the Szydlowsky-Planiol (SP) supercharger your ability to make power with the H-S engines is limited. Perhaps you can adapt/design a new supercharger. But that takes time.

 

[Shortround6]

Airframe does not have a vote here

It sort of does. If you change the type of V-12 engine you do have to change the everything from the firewall forward including the firewall.

There was no engine mount to unbolt from the firewall like on just about every other plane/engine. The engine was fastened through the cowl using 4 large bolts/pins (two on each side) and the cowl carried the loads back to the firewall/front of fuselage structure.
The cowl sides were a tall but thin double wall box beam on each side. The cowl not only covered the engine, it was the structural support for the engine.
You can keep the wing and landing gear, and the fuselage from about the front of the cockpit back but any engine change is going to need more work than a normal engine change.

Firewall/bulkhead and structure right aft of the Firewall have to transmit all the loads to the rest of the airframe.

This is for a P-40 (easier to find)

The gray tubes/structure is the engine mount. Includes a rear sway brace that connects the side mounts around the rear of the engine to the middle of the firewall.
You may be able to adapt a Jumo 211 mount but your firewall needs to be able to transmit the load from the mount to the longerons and/or fuselage structure, may need local reinforcement. The Cowl now has to cover the mount.

Jumo 211 mount

You can design a beam mount to go down rather than up but like the DB 601 they used four large fasteners per engine, just not in the same place as the DB 601 engines.
Ok, here is a DB601 engine mount.

The cowl on the He 100 replaced the big beams and the lower brace. You may be able to change engines but it needs a lot more work than swapping engines on normal plane.
You may also wind up with a few extra inches of width. Or...................................you may wind up with a nose like this

 

[tomo pauk]

The cowl on the He 100 replaced the big beams and the lower brace. You may be able to change engines but it needs a lot more work than swapping engines on normal plane.

Agreed pretty much.
OTOH - a swap from DB 601 to the Jumo 211 will be far easier to do than what was required when the Italians went from radials to the DB 601 (whether as one-off job, like with CR.42 and G.50, or as a true conversions, like with Regianne and M-C).

You may also wind up with a few extra inches of width. Or...................................you may wind up with a nose like this

Yes, minus the guns opening, channels and bulges.

 

[GrauGeist]

There was also (going by memory) an issue with the Jumo's semi-cowled supercharger versus the DB601's shrouded supercharger.

 

[Shortround6]

OTOH - a swap from DB 601 to the Jumo 211 will be far easier to do than what was required when the Italians went from radials to the DB 601 (whether as one-off job, like with CR.42 and G.50, or as a true conversions, like with Regianne and M-C).

True, it did take Macchi 7 months to build the 1st prototype and another 9 months to get the first production models.
Granted there was not a lot of production tooling that had to be redone for the He 100 but you do need production tooling for more than small batches.

You do have the advantage of having extra space in the wings for fuel after you take the cooling system out of the wing.
Now you just have to figure out how to cool the Jumo 211.

 

[tomo pauk]

You do have the advantage of having extra space in the wings for fuel after you take the cooling system out of the wing.

Agreed. There is also more usable volume to gain just behind the pilot, where the oil/alcohol heat exchanger was located.
Translation by yours truly:

Now you just have to figure out how to cool the Jumo 211.

The 'power egg' configuration is the most elegant solution, the shortcoming is that it adds another 150+- kg of cooling system away from the CoG.
A big underbelly radiator, half of it being burried in the fuselage - like it was in vogue on many European V12-powered fighters in the late 1930s/early 1940s - is another possibility. Model by the most prolifix modeller - dizzyfugu.
The 'beard' position can also be donne, ungainly as it was on this MC.202 one-off. Not a deal breaker, as seen on P-40 or Typhoon, but also not as elegant as what MC.202, 205, D.520 or plenthora of Soviet fighters had.

 

[tomo pauk]

There was also (going by memory) an issue with the Jumo's semi-cowled supercharger versus the DB601's shrouded supercharger.

Jumo's impellers on the S/C were fully shrouded. These, as installed on the 211A/B/D/G/H were judged as not very efficient, and were replaced by the impellers designed by DVL; again fully shrouded, but more efficient.
Early impeller with the 2-speed drive; note the exit of the impeller that (among other finicky bits?) was changed by DVL:


Improved, as installed on 211F/J/N/P: picture NACA report on the unit: link
Similar impeller was used on the Jumo 213A-C, and as 2nd stage on 213E & F.

What was of the crucial interest for a fighter aircraft was the power vs. altitude. The 211A was good for about 920 PS at 5.2 km (5 min rating), the 211B and D were doing 900 PS at 5.2 km, but for 30 minutes. The 211F (from Spring of 1941) upped that to 1060 PS at the same 5.2 km, again the 30 min rating.

 

[tomo pauk]

Let's expand the what-if: other countries also get a stab on the topic, too. Like Japan and/or Soviet Union - countries that bought He 100s, or perhaps Italy, that might look favorable on a fighter that can be very fast despite the modest engine power. Or, perhaps te plans for the He 100 are leaked towards Allied countries by early 1939...

In the meantime, this is a He 100 with nose of Avia B.35, that Germans get to know in details by April of 1939 (LW will want to have the variable pass prop here, of course); Willy back at MTT does not like the contraption going as fast as the Bf 109E that has 20% more power:

 

[SaparotRob]

Cooling was its Achilles heal. An air cooled version has drawbacks of course but what if Daimler-Benz developed a twin row rotary engine for it?

 

[tomo pauk]

Cooling was its Achilles heal. An air cooled version has drawbacks of course but what if Daimler-Benz developed a twin row rotary engine for it?

DB was not that much in radial engines. They already have had enough of problems in troubleshooting their bread and butter V12s from 1941 on...
A reason why I've slapped the nose of the Czech fighter (including the coolant radiator) is because, for the purposes of this thread, He 100 looses it's surface cooling systems. Not perfect, but there is less of the plumbing to get pierced by bullets than what Bf 109 had.

 

[SaparotRob]

I forgot to add contra rotating rotary engines.

 

[GrauGeist]

I might point out that Rotary aircraft engines were phased out shortly after WWI.

Radial engines (while being round like Rotary engines) are different in the fact that the engine is stationary and the propeller is driven by the rotating crankshaft whereas a Rotary engine revolved around a stationary crankshaft with the propeller being attached to the engine's body.

 

[SaparotRob]

 

[Howard Gibson]

Lets say that RLM greenlits the He 100 fighters for production in April 1939, with caveats/requirements:
- since the DB 601s are in short supply, Heinkel needs to find the alternative for the next 18 months of production (RLM is open for suggestions wrt. these alternatives)
- no evaporative cooling system(s)
- speed and endurance in ballpark with Bf 109E for starters
- guns' armament: at least one cannon + 4 MGs, or two cannons + 2 MGs

Heinkel has 3 months to have the prototype flying, and another month for another prototype.

Since I love the zero-sum game, feel free to alter the RLM purchases accordingly. Granted, 1-engined fighters are probably the cheapest and easiest to produce of all 1st line combat aircraft back then, so this will not hugely tax the German resources in the 1st place.

Be careful when you list the performance of prototype aircraft. It takes years to go from flying prototype to production and lots of aircraft in service. The He100 was contemporary with the Lockheed P-38, the Vought F4U, and the Hawker Typhoon. Even the prototype Bell P-39 was up there. Were the He-100's performance figures done with full armament, a full load of ammunition and fuel, and contemporary armour? Ernst Heinkel was into high speed flights. The next time you see or read something about the Martin Baker MB5, look at the photos for the armour plate behind the pilot. It wasn't there. What else was not there when these aircraft did their high speed runs?

The He-100's armament was inadequate. How do you increase it? The He-100 was a tiny airplane. There was nowhere to stuff a pair of MG151/20s.

What happens if some other manufacturer develops a high performance aircraft that uses BMW801 radials instead of the DB601s reserved for Messerschmitt?

 

[Capt. Vick]

Are the engines shrunk to be able to fit somewhat smoothly to the airframe in the above two drawings? They seem it to, as the He 100 airframe was "small".

 

[GrauGeist]

The He-100's armament was inadequate. How do you increase it? The He-100 was a tiny airplane. There was nowhere to stuff a pair of MG151/

The He100's armament was in keeping with contemporary fighters of that point in time.

The initial Bf109 had only two cowl mounted MGs and a third mounted in the engine's centerline - comparable to the He100 (two wing mounted MGs and a motor centerline MG).

Given that the Bf109's wing was no larger than the He100's, it's entirely possible that the Heinkel could gave been modified for an Mg151/20 or two more MGs with an MG151/20 in the motor centerline.