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Fighter engines

Discussion in 'Aircraft' started by GunSlinger86, Sep 18, 2016.

  1. GunSlinger86

    GunSlinger86 Well-Known Member

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    I've posted similar threads on different areas of this topic, but I guess the evolution of my questioning and what it comes down to is this: Why did the US not employ a second stage supercharger in the P-39 and P-40 engines for higher altitude performance when its British and German competition had them in their system, which in turn made them better fighters at higher altitudes? The P-39 and P-40 held their own and could be superior is some aspects at lower to medium altitudes, but lost any edge the higher it went. Later upgrades improved these flaws but still didn't totally solve the problem. Was it economics, in terms of cost of the engine system that prevented them from adding it? Did Army Air planners believe the planes would have competed at the same level without the second stage supercharger? I believe the P-38 also had issues when it came to a second stage supercharger as well?
     
  2. GunSlinger86

    GunSlinger86 Well-Known Member

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    On historyofwar.org, I found somewhat of an answer. I'm going to paraphrase: The Army Air Corps basically viewed the P-39 as a pursuit aircraft operating as a low-level cooperation aircraft, and because of this and because the second-stage turbo-supercharger caused some aerodynamic problems, it could be removed safely. The heavily-armed high altitude bombers could defend themselves against enemy fighters.

    That way of thinking seems flawed because if its a pursuit aircraft, wouldn't enemy fighters that wreak havoc on ground forces and bomber formations have to be pursued at higher altitudes if they choose to fly higher?
     
  3. Poppy

    Poppy grasshopper

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    Trying to remember a thread here...
    Wasn't it that there was a limited number of that tech, it was expensive and difficult to produce.
    Also, recalling a memo from (?) saying that superchargers were not needed on the P39?
    The 39 was a bit of an odd duck anyway, could it have been an effective higher altitude fighter?
     
  4. GunSlinger86

    GunSlinger86 Well-Known Member

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    I paraphrased what that website stated. Basically the turbo-supercharger interfered with the aerodynamics of the plane, and they thought the bombers could defend themselves so it was seen more as a ground support, low-altitude plane.

    Does anyone know why the P-38 wasn't given an adequate turbo-supercharger?
     
  5. phylo_roadking

    phylo_roadking Member

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    Choosing to climb to avoid an attacking fighter wasn't a common manouver - as you were fighting gravity as well as the enemy ;) Climbing was relatively slow and took time. What was far more common was starting with altitude and diving on enemy fighters, as it gave you a speed advantage courtesy of Isaac Newton ;)

    In other words - in several theatres of WW2, including the Eastern Front, and over South-East Asia, air combat that started at low altitudes remained at low altitudes for the duration of the encounter, as attempting to climb for height and room in effect slowed you down. And if the aircraft attacking you had a higher accumulated speed because THEY had dived on you first from above - they'd momentarily STILL have the speed advantage if they chose to follow you up. Wouldn't last long....but just long enough ;)
     
  6. GunSlinger86

    GunSlinger86 Well-Known Member

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    The P-39 and P-40 were solid, fast-divers, and could out-fight the other fighters at lower altitudes. I guess they were never intended as high-altitude flyers.
     
  7. phylo_roadking

    phylo_roadking Member

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    I.E. heavy ;) They could take lighter and more manouverable fighters with fast diving "boom'n'zoom" attacks - drop down on a target from above and behind with accumulated speed from the dive, make a fast pass...but immediately continue the dive away, leaving any surviving enemy in their wake as they first had to accelerate from best economy cruise to full war power THEN follow them down. If the P40 pilot made the mistake of getting into a furball they were dead.

    A look at the design process and original specifications for the type might be interesting I.E. did the designers know about the problems in the Pacific that the RAAF discovered in early '42 over Darwin...that there was a greater heat drop-off with altitude over the Pacific - from tropical heat down on the deck to subzero in a few thousand feet, far more pronounced than over land. It gave major problems for the oils used in their Spitfire VB constant pitch units and governors leading to racing engines and engine failure...

    The P40, being designed for the U.S.'....um.."colonial" use had to thrive in that environment - heavy airframes, longer ranges, better undercarriages (wider spaced struts to prevent or at least minimise ground looping) for rougher or dirt flightlines...and the different atmospheric conditions. I wonder to what extent those atmospheric conditions - temperature and air pressure - factored into the design process...
     
  8. GunSlinger86

    GunSlinger86 Well-Known Member

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    The P-40 had a better roll-rate than many of the other fighters of the war as well.
     

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