Turbocharging of V-1710 a failure?

[gjs238]

In response to Circular Proposals X-608 X-609, US aircraft designers responded with what became known as the P-38, P-39 and P-40.

The first two were originally designed with turbochargers to satisfy high altitude requirements.
The turbocharger was deleted from the production version of the P-39.
The P-38 kept the turbos, but exhibited unacceptable reliability in the European theatre at high altitudes.

However, turbochargers were employed successfully (and reliably) on radial engine powered aircraft like the B-17, B-24, P-47, etc.

In summary it appears that the radial engines of the time lent themselves to turbocharging far more successfully than the V-1710 - so much so that it may be fair to say that the V-1710 turbocharging projects were a failure, and that more effective supercharger development would have been the better path to follow.

 

[davebender]

The successful American turbocharger installations were all on large aircraft. Getting a turbo to work reliably on a normal size fighter (i.e. Spitfire, Me-109, Dw-520, A6M etc.) is an entirely different matter.

 

[Colin1]

The P-38 kept the turbos, but exhibited unacceptable reliability in the European theatre at high altitudes

They didn't do well
but it's a little unfair to isolate the V-1710 as the sole reason, it is also remarkable in just how long it took Langford Lodge to get off their asses and correct the various problems with the implementation of field mods.

The altitude that the P-38s were being called upon to operate at were unprecedented to date, they seldom fought above 30,000ft and had not been forced to fly for long hours at those altitudes, this exacerbated several issues:

1. Windscreen defrosting
2. Adequate cockpit heating

these two issues combined to create the single biggest factor that diminished the effectiveness of the P-38 in the ETO. As for the engine problems:

3. Automated engine controls didn't appear until the H model; in the hands of an inexperienced pilot it was easy to overboost the engines on the throttle.
4. Supercharger intercooling design caused a number of engine failures, a simple redesign for the J model negated the reliability issues whilst producing more power from the same engines.

5. Being driven by all of this was the morale issue during the winter of 1943-44. Col George Doherty, CO of the 50th FS was apalled by the attitude of most P-38 flyers that they expected every mission to be their last.

When asked, a 20th FG pilot conceded "Well, those Allison 'time-bombs' didn't help any. That's the term we commonly used when referring to our engines. And there were many cases of frostbite. The lack of adequate cockpit heating went far beyond simple discomfort at those altitudes; it was enervating in the extreme".

 

[davebender]

The lack of adequate cockpit heating went far beyond simple discomfort at those altitudes; it was enervating in the extreme

The same can be said for gunners on B-17s and B-24s. I've read plenty of first hand accounts of defective heaters in aircrew flight suits. No wonder the B-29 went to remote controlled gun turrets.

 

[Shortround6]

Please note that there were two rather different turbo installations on the P-38 and several minor variations.

The Early installation used the leading edge of the wing as an inter-cooler. This inter-cooler set up limited the airflow and total HP and was not suitable for the higher HP versions of the V-1710 but it didn't seem to have the problems at high altitude/cold weather that the later versions did.

The later versions, with the "chin" inter-cooler set up allowed for the higher horsepower but were a little too efficient in cruising mode. the intake charge temperature fell to a point where raw fuel condensed out of the mixture in the intake manifolds in Europe in time period in question. This was NOT helped by the technique of cruising at high rpm and low boost which was taught to the pilots stateside and was against the recommendations of both Lockheed and Allison who recommended low rpm and high boost which would have raised the charge temperature AND caused less wear on the engines.

Please also note that Rolls-Royce fitted an intake charge heater to some versions of the 2 stage Merlins fitted to commercial aircraft to solve a similar problem in cruising flight.