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"It was a very special airplane, let's say, with the engine in the back, then those Italian maniacs always wanted do aerobatics, when they looped they came in this position and then had to continue, but it was too slow and instead of lowering the head, which it did not have ( for the position of the engine) they went in a flat spin and so they were screwed so a very good Genoese Pilot, Moresi left his skin, another Sergeant left his skin, even though they were saying, ehhhh, do you know what I say, if you loop, do it fast, but for me it was a fabulous plane because it had a tricycle undercarriage, on the ground it was driven like a car, apart from this tricycle undercarriage it had in the axis of the propeller a cannon of 37 and four machine guns on the wings the engine was a 1200 hp Allison a beautiful engine it was a very pretty airplane…"
I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?
The Merlin system worked but it was also a bit on the crude side (at first look) and many engineers were trying to go one better. The Merlin ALWAYS both impellers spinning at the same time and spinning at the same speed. Effective but not very flexible with a two speed drive. P & W's two stage (first flown in 1939 so two stage superchargers aren't unknown in the US) had a single speed supercharger on the engine and a two speed drive with neutral on the auxiliary supercharger drive given three possible combinations. Allison stuck a hydraulic coupling in the drive the auxiliary supercharger giving an infinite number of combinations between a high and low limit. More elegant from an engineering point of view but you had to pay for it somehow.
The air to air intercooler is more resistant to battle damage. A liquid intercooler suffers just alike a liquid radiator from one or two minor hits. A couple pencil size holes in the airducts of an air to air intercooler isn't going to affect things that much. However keeping all those airducts air tight in day to day operation was more maintenance intensive. You pay your money and take your chances.
Just my opinion, but what the Allison needed was not a two speed supercharger but a (mechanical, not turbo) two stage supercharger.
We've had the two speed argument here before, and I still maintain that low gear's purpose is just to keep the pilot from overboosting the engine at takeoff and low altitude. The P-39 had plenty of performance at low altitude with their single speed unit regulated by the pilot in early models and the automatic boost control after mid '42. The Allison's single speed was in effect "high" gear, and the need for low gear was eliminated by the autoboost control. The whole two speed vs one speed argument is moot in my opinion.
The two STAGE engine was needed to keep up with the two STAGE Merlin 61 and the two stage R-2800s. The two stage engine provided more power at higher altitudes because the first (or auxiliary stage whether it be mechanical or turbo) stage boosted the thin air at high altitude up to sea level thickness and discharged it into the second (internal) stage which boosted it even further to get those fantastic speeds at high altitude. In effect, the first stage fooled the second stage into thinking it had sea level (high density) air at 25000' boosting power tremendously.
whats surging? I have an idea, but not certain really.
On the very early P-38's they had to change the supercharger gear in the V-1710 to increase the boost from the mechanical supercharger so they could reduce the boost required from the turbo at high altitudes. Early on they had a problem with the turbos coming apart at high boost. Those "fins" on the side of the booms between the cockpit and the turbos were shields to protect the pilot from disintegrating turbochargers.
The fuselage was indeed lengthened by 1.75' but that was their solution to the extra 200# from the auxiliary stage supercharger. Adding 200# aft of the CG necessitated moving the wing back a little for balance, then the tail had to be moved back to preserve the distance from the CG to the tail for the same leverage. That is why the front cockpit door edge is before the wing leading edge (same as the P-63) while the normal P-39 front door edge is right about even with the wing leading edge. They moved the wing back.
Now is where I differ from what you have read. The engine compartment for the P-39E and the P-63 was still exactly the same size as the P-39. The distance from the front edge of the engine compartment (right before the exhaust stacks at the cockpit turnover structure) and the back bulkhead (almost to the back edge of the carb inlet scoop, you can see the panel edges) is EXACTLY the same.
My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?
Packard had to a lot of work on the Merlin because they could not use the RR approach of experienced craftsmen, who hand-selected each part. Packard wanted to put Merlins together like an American automobile engine, and to do that they had to make the parts to tighter tolerances than did RR.
I believe the Mosquito had a bigger cannon but size doesn't matter DaaaahlingIt was far superior in the size and uselessness of its main cannon.
I believe the Mosquito had a bigger cannon but size doesn't matter Daaaahling
I was of course (in that post) joking, but in principle I cannot see any advantage the P 39 had over any other allied fighter, bearing in mind the Allies as a group had to defend daylight bomber boxes, defend the UK from any attack by any type of aircraft S/E T/E or buzz bomb and achieve air supremacy over Italy, Normandy and the Pas de Calais ...That is just European requirements.The Mosquito wasn't in the list.
Besides, the Mosquito wasn't a fighter, but a fighter bomber, and its cannon was useful!
Packard had to a lot of work on the Merlin because they could not use the RR approach of experienced craftsmen, who hand-selected each part. Packard wanted to put Merlins together like an American automobile engine, and to do that they had to make the parts to tighter tolerances than did RR.
My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?
I'm pretty sure it means they were scared shitless, not that they did.
The big advantage of the Allison mechanical two stage over the turbo is it takes up much less internal volume. In addition to the actual turbo there was the associated internal ducting (14' per engine in the P-38). The exhaust had to be ducted back to the turbo, the compressed turbo air had to be ducted back up to the intercooler (in the wing on F,G and H) then that air had to be ducted to the carburetor. All this ducting had to be properly aligned and sealed for the whole thing to work right.I would note that the main difference between a good mechanical two stage system and a good turbocharger tow stage system is that in the turbo system the auxiliary supercharger is driven by an exhaust gas powered turbine and not a driveshaft from the engine.
You still need the auxiliary impeller and casing and you still need the intercooler and ducting (or intercooler radiator).
Anybody who thinks you can have a significantly smaller mechanically driven two stage system is either settling for less performance or fooling themselves.
We must be reading the same book. The -93 was in production in May and the model tests were not yet completed but the Army had sufficient confidence in the engine to start putting it in airplanes prior to test completion. After a short rework of the jackshaft these engines were considered very reliable. The development of the piston rings etc. benefited all Allison engines, not just this one.Not only lacking wing gun drag, lacking around 1000lbs of weight compared to a service P-63.
The graphs give no description of the aircraft involved.
I also love the part in an earlier post about the V-1793 being in full production in May of 1943.
May of 1943 saw the engine fully prepared for the model test, which was not actually fully completed until Nov 27th 1943. Yes engines had been built, delivered and were flying in P-63s before Nov 27th but after that date the engines were released for unrestricted use. Except the WER rating test was done in Dec of 1943 so any fantasies of P-63s or Super Allison Mustangs flying around with 1800hp at sea level engines need a reality check. Especially considering that the long development time included modified pistons and piston rings to stand up to the water injection and extra power.