Some questions

Discussion in 'Aviation' started by mole, Nov 25, 2005.

  1. mole

    mole New Member

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    1. Bearcat is lighter than f4u. Why is the bearcat slower than the f4u?

    2. were the American and japanese radial engine fighters less aero dynamic than the germans, russian and british raidal fighers (fw190, la series and tempest II)?

    3. Can guns fire through 4 or more blade propellers?

    4. how is Gyro gunsight work?

    Thanks in Advance
     
  2. evangilder

    evangilder "Shooter"
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    Depends of the model of F8F and F4U. The F4U-1A and F8F-1B were about the same top speed. Weight is not the only factor that makes for a faster or slower airplane. Now when it come to climbing, the F8F was the hands-down winner in that contest. The F8F could go from a full brake stop on the deck to 10,000 feet in 96 seconds! You haven't seen anything until you've watched a Bearcat climb.

    Question 2, I don't know.

    3. Probably, the synchronization for firing between prop blades was just a gear or belt. Interrupting the fire while the blade was in from of the barrel shoud not have been difficult.

    4. Do a google search. I am sure that there are a number of sites on the web that can do a great job going into how they work. Ditto on the other items above.
     
  3. the lancaster kicks ass

    the lancaster kicks ass Active Member

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    i believe evan answered your first question, however with regards to the second it depends on the size of the engine, the british were not fans of radials, we didn't really like them however the Tempest II for example had a very close coweled engine, as did the russian La-5 for example, as did the corsair though, the jap engines were not that powerful so they did have air resistance problems, however the american radials were so powerful that they overcame the drag from big radials anyway.........

    question 3, yes, it could, however there would be little point as the volume of fire it could put out would be minimal...........
     
  4. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    As for question 2. Not really. A Fw-190A and a P-47 for example were both just as aerodynamical as the other.
     
  5. NiallC

    NiallC New Member

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    In answer to your questions
    1. I'm not at all sure that the F8F is slower than the Corsair, but, in any event, weight is not of great importance in maximum speed. A Tiger Moth is rather lighter than either the F8F or an F4U, but also somewhat slower. Power(and the efficiency of converting that power into propulsive energy) and the aircrafts drag largely determine max speed. And, of course, whether the aircraft has been optimised for max speed or for some other parameter - such as climb.
    2. The Fw 190 set the standard in terms of efficient packaging of radial engines. Typical early American and English radial installations were somewhat crude by comparison (which is odd considering the American NACA cowling and British Townend ring were early steps in getting this right). The F8F and Tempest II/ Sea Fury both show signs of lessons learned from the 190. The British in any event did not, for much of the war, have radials that were particularly suitable for fighter use, since the whole British radial programme hinged around Bristol sleeve valve engines which matched extraordinary sophistication in their valve drive arrangements with superchargers that were straight from the Stone Age - and accordingly poor performance at altitude. The Japanese were also early adopters of well designed, closely cowled radials (occasionally with fan cooling) with individual, rear swept exhaust stacks to maximise residual thrust.
    3. Theoretically there is no limit to the number of prop blades through which a synchronised gun installtion can fire, but, the more blades there are, the more the rate of fire of the gun is reduced. There were several Japanese fighters with 4-blade props and syncrohronised guns (Ki 84 and the NIKI- J Shiden come to mind as mass-produced examples. I'm sure there were more.)
    4. Gyro Gunsights: I'm assuming that your question relates to WW2 Gyro gunsights - before transistors, integrated circuits or digital computers were invented. The basic principle is to use a gyroscope (which resists movement) to hold back the aiming point seen by the pilot in his gunsight so that, if the pilot aims directly at the target then the mean point of impact of the bullets will be ahead of that point. The challenge is to engineer it so that it can cater for different rates of turn, dirrecnt speeds, different ranges etc. In the early Gyro sights this was achieved by using an electrically driven gyro - spinning at around 4000 rpm - to which was attached a mirror that was used to project the graticule that the pilot saw in his sight. The pilot had to set the sight to the wingspan of the target, his speed and the altitude (since bullet drop is strongly affected by air density) and then, using a control on the throttle lever (which his hand would be on anyway) activate the sight as he turned with the enemy aircraft. As he turned with the enemy, within a second or so, the gyro and some very simple electronics would hold back his line of sight to the correct degree. This, the Mark II GGS, was also produced under license in the US as the K-14(USAAF) and Mk18 (USN).

    Hope this helps.
    NiallC
     
  6. GregP

    GregP Well-Known Member

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    As to power versus speed, the R-2800 was not a particularly good high-altitude engine. The supercharger gears were optimized for medium altutide.

    A change to a high-altitude supercharger would have made the Bearcat much faster at altitude, but it wasn't meant for high-altitude work.

    As for a comparison between the Corsair and the Bearcat, the Corsair's airspeed sensing unit was highly suspect. The Corsair had the same engine and propeller as the Hellcat and , if flown side by side, were VERY close to one another in the high and low boost areas, but not in the specs. In the main stage (unsuperchargerd), the Corsair was a bit faster because Grumman did not use ram air due to potential problems with carb icing, but Vought did.

    Ram air equals more airflow through the engine, and that equals more power. In the high and low boost stages, the gears were the same, and so was the prop. Since the form drag was the same, the performance was equal as far as speed goes.

    The Hellcat was far and away better at sustained turn rate due to wing area and wing loading. The Corsair went higher due to better span loading, and it rolled better due to excessive dihedral in the Hellcat (which could have been cured, but that would have meant interrupting the production line for a few weeks ... a BIG no-no in the eyes of WWII's procurement gurus).

    I'd look for the Bearcat to beat the Corsair one on one in maneuverability, speed, AND climb, despite the specs. But, I'd look for the Corsair to take more punishment than the Bearcat and still keep flying.

    All in all, the Bearcat was later design and SHOULD have been better using the same engine.
     
  7. mole

    mole New Member

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    Thanks for those answers

    Goodyear's F2G had a bubble canopy and a lot of horsepower, like 3000hp, some how it is slower than some early models?

    The japanese Ki-84 had greater hp than russian La-series. Ki-84 never reached 400mph?
     
  8. evangilder

    evangilder "Shooter"
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    Good analysis there Greg and I totally agree on the statement above.
     
  9. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    That was because of the low quality of the fuel that the Japanese were using. A captured Ki-84 "Frank" wastested by the United States with a higher octane better quality fuel and it reached the speed of 689 kmh or 428 mph. The Ki-84 was considered one of the best performing aircraft of the war. She just lacked well trained experienced pilots and good fuel.
     
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