Light fighters alternatives, 1935-1945 (2 Viewers)

[don4331]

I am crunching your numbers here. A 3.5 litre engine putting out 650hp at 13,000rpm works out to a BMEP of 1280kPa, or around 185lb/in^2. This is consistent with 87 octane fuel. 13,000rpm is remarkable for an engine on a van. How long is this engine going to last?

The Cosworth-Ford HB V8 was expected to last just over 21 km (3 laps of Spa-Francorchamps which is 7.004 km/lap). 68% of time at full throttle, considerable less at full power as the car was going up through the gears. Out lap at ~80% power, qualifying lap at full beans (~100 seconds) and a cool down lap at ~80% again. After qualifying, the engine was replaced with a de-tuned engine expected to make the ~300 km (less than 2 hours) of the race.

Fuel at the time was limited to 104 octane.

 

[don4331]

Here is 675 hp aviation engine:

ASE-650 SAGA - Aerosport Engineering

That is not an aviation engine: It is a BMW M73 V-12 with low compression (8:1) pistons <and better rods>, a supercharger <for almost 25 psi> and a speed reducer.

Note: BMW will persecute anyone putting their engine in an airplane with the full might of an OEM automotive manufacturer (they did so against the team running BMW V-12s in their Vimy replica before their attempt to replicate Alcock and Brown's flight <resulting in replacing engines with Orenda V-8s>).

 

[topspeed]

That is not an aviation engine: It is a BMW M73 V-12 with low compression (8:1) pistons <and better rods>, a supercharger <for almost 25 psi> and a speed reducer.

Note: BMW will persecute anyone putting their engine in an airplane with the full might of an OEM automotive manufacturer (they did so against the team running BMW V-12s in their Vimy replica before their attempt to replicate Alcock and Brown's flight <resulting in replacing engines with Orenda V-8s>).

Ok it is converted into an aircraft engine...there is only a block from BMW.

 

[topspeed]

I just asked my cat (she's not retired) and she informed me that a propeller driven aircraft is unlikely to be capable of supersonic flight due to the propeller tips going supersonic while the base of the propeller is below transition.
The shockwaves created by the tips creates drag and spoils the airflow as well as buffeting the airframe.

She also suspects your retired Colonel may have meant the F-88 Voodoo, which did reach Mach 1.0 but was jet powered and only used the prop to reach altitude for testing.

She is fairly well informed about these things.

Well he did not reply when I asked was the propeller running and was the plane in a dive.

Calling a USAF colonel a cat is a sign of bad taste.

But you could be right....as:

Only two civilian test pilots ever flew the Republic XF-84H "Thunderscreech". No military (USAF or U.S. Navy) pilots ever flew the prototypes, as testing never progressed past the manufacturer's Phase I flight tests at Edwards Air Force Base. [1, 2, 3]

• Henry G. "Hank" Beaird Jr.: A Republic Aviation test pilot who flew the vast majority of the program's testing—logging 11 test flights in the first prototype (FS-059), most of which ended in emergency or forced landings. [1, 2, 3]
  • Lindell C. "Lin" Hendrix: A Republic Aviation test pilot who flew just a single flight in the second prototype (FS-060). After experiencing severe longitudinal instability ("snaking") above 450 knots, he refused to ever fly the aircraft again, famously telling the project engineer: "You aren't big enough and there aren't enough of you to get me in that thing again." [1, 2, 3, 4]

Flying fast supersonic in thick air with a propeller driven craft is a no brainer.

 

[GrauGeist]

Calling a USAF colonel a cat is a sign of bad taste.

No one called your Colonel a cat.

I said that I consulted MY cat and being a cat, also out-ranks a Colonel (cat owners can easily attest to this).

 

[Shortround6]

Light fighters tend to be on a sliding scale, they got heavier as time went on.
Trying to use technology from later that WW II really changes things. Technology changed a lot during WW II depending on country. Some changed more/faster than others.
Also using modern engines that only need to operate at 12-14,000ft as justification for performance estimates for WW II fighters that had to operate at higher altitudes (15-25,000ft) has some differences aside from better materials, better manufacturing, better design.

For "light" fighters to really work they need engines that offer higher power to weight ratios than 'standard' engines. Using 2nd rate engines to be cheap means fighters that are not as effective. Question becomes are more numerous cheap fighters are better than fewer higher performing fighters?

French were pretty good at building fast light fighters, problems included they didn't climb well, had high wing loading (poor turn?), acceleration was suspect and armament was often light. Italian SAI. 207 carried two 12.7mm guns which was OK in 1940, it was not OK in 1942/43.

Do these "modern" low production high-performance engines have to pass a standard 100-150hr type test? Or are they "experimental"?

 

[don4331]

Ok it is converted into an aircraft engine...there is only a block from BMW.

Block, heads, crank, cams & their drive, oil & water pumps, valves, etc, etc are all BMW.

Yes, it is converted to drive a propeller, but no track record of successfully being an aircraft engine.

 

[topspeed]

Block, heads, crank, cams & their drive, oil & water pumps, valves, etc, etc are all BMW.

Yes, it is converted to drive a propeller, but no track record of successfully being an aircraft engine.

Yes that is true....but a lot of LS engines are converted for aviation too.

 

[Shortround6]

Yes that is true....but a lot of LS engines are converted for aviation too.

Define "a lot".

Porshe tried to break into the aircraft engine market twice. Once in the 50s with their flat 4 and then in 1960s with their flat 6 911 engine. Engines were substantially down rated.
Corvair engines used to fairly popular with homebuilders but good converter shops generally held the power down to about 80ph for reliabilty.

This engine seems like a real boutique engine. Special purpose (fits in scaled down Mustang or Spitfire cowl) with few or no bulges or bumps and offers much more power than any "certified" engine using a bunch of higher quality parts than the stock engine and at the cost of factory BMW parts that is going some.
Number of hours flown per year is what?
Cost of overhaul is what?
At the end of the 1950s/beginning of 1960s both Lycoming and Continental were offering some "advanced" flat 6 air cooled engines. Lycoming was offering a fuel injected, supercharged, geared 340hp 7.3 liter engine. That 340hp was good for 11,000ft courtesy of the supercharger. They also used a reduction gear to allow for 3400rpm for the engine.
By the early 60s Lycoming was changing over to an 8.9 liter engine that could do away with the supercharger (unless in the mountains) of 350hp.
At lower power levels the larger engine could also do away with the reduction gear and run at lower RPM. Overhauling the supercharger and reduction gear cost almost as overhauling the basic engine itself.

Race engines are all about high power and overhaul life is very far down the list. For an air force they need to find a sweet spot, lots of power but they can't be changing the engines every 20-30 hours.

 

[topspeed]

Define "a lot".

Porshe tried to break into the aircraft engine market twice. Once in the 50s with their flat 4 and then in 1960s with their flat 6 911 engine. Engines were substantially down rated.
Corvair engines used to fairly popular with homebuilders but good converter shops generally held the power down to about 80ph for reliabilty.

This engine seems like a real boutique engine. Special purpose (fits in scaled down Mustang or Spitfire cowl) with few or no bulges or bumps and offers much more power than any "certified" engine using a bunch of higher quality parts than the stock engine and at the cost of factory BMW parts that is going some.
Number of hours flown per year is what?
Cost of overhaul is what?
At the end of the 1950s/beginning of 1960s both Lycoming and Continental were offering some "advanced" flat 6 air cooled engines. Lycoming was offering a fuel injected, supercharged, geared 340hp 7.3 liter engine. That 340hp was good for 11,000ft courtesy of the supercharger. They also used a reduction gear to allow for 3400rpm for the engine.
By the early 60s Lycoming was changing over to an 8.9 liter engine that could do away with the supercharger (unless in the mountains) of 350hp.
At lower power levels the larger engine could also do away with the reduction gear and run at lower RPM. Overhauling the supercharger and reduction gear cost almost as overhauling the basic engine itself.

Race engines are all about high power and overhaul life is very far down the list. For an air force they need to find a sweet spot, lots of power but they can't be changing the engines every 20-30 hours.

Didn't germans actualluy change the engines very quickly on Me-109s for instance ?

 

[GrauGeist]

Didn't germans actualluy change the engines very quickly on Me-109s for instance ?

The DB601 was good for about 100 hours between overhauls.

The BMW801 was good for about the same, until they introduced MW50, which reduced the TBO to about 25+ hours.

 

[tomo pauk]

The BMW801 was good for about the same, until they introduced MW50, which reduced the TBO to about 25+ hours.

Perhaps during the testing?
The BMW 801 with MW50 probably saw no service. By mid 1943, LW preferred to use the excess fuel to cool the charge so the overboost is safe(r), and later just to open up the throttles as the C3 fuel gotten better in rich rating, and the engine itself was sorted out.