Here's something mildly interesting

Discussion in 'Aviation' started by Elvis, Nov 30, 2008.

  1. Elvis

    Elvis Member

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    I was thinking about climb rates of some of the better known WWII fighters the other day and noticing how "spectacular" they seem (within the context of what they are/were), wondered what those rates were in MPH.

    So, I broke out my trusty calculator and started doing some figuring.
    No real "rocket science" here, just the realization of some facts.

    There's 5280 feet in one mile and 60 minutes in every hour.

    That's about all you need to know to figure this out.

    Man, was I surprised!
    Using the climb rates supplied by an article written by Chuck Hawks, I chose four aircraft:
    The BF-109E, The P-51D, The Mitsubishi A6M5 mod. 52, and the Supermarine Spitfire Mark IIA.

    Hawks lists their rates of climb as such:
    BF-109E - 2990 ft./min. @ 13,150 ft.
    Spit IIA - 3025 ft./min. @ 12,800 ft.
    P-51D - 3320 ft./min. @ 5,000 ft.
    A6M5-m.52 - 3340 ft./min. @ 8,000 ft.

    Starting with the slowest plane, the 109E, 2990 ft./min. is equal to 179,400 ft./hr (multiplied by 60).
    Since there's 5,280 ft in every mile, hitting the "divide" button, entering "5280", then hitting "=", results in the figure "33.977272".

    ...that's just under 34 MPH, folks.

    Doing the same for the rest, here's how they stack up...

    Spitfire IIA - 34.375 MPH
    P-51D - 37.727272 MPH
    A6M5 - 37.954545 MPH

    Hawk's section on the 109 goes on to mention that the "K" model featured the 1800 HP DB605D engine and had a "sensational" climb rate of 4820 ft./min., or...54.772727 MPH.


    To some of the more savvy members here, my realization may not seem like much, but I was really floored at how those figures, which sound rather breathtaking, convert to a rate of speed almost all of us can relate to.
    Maybe something to remember, the next time you read about Piper Cubs and Aeronca C-2's flying at a "pedestrian" 50 MPH. ;)





    Elvis
     
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    You need to consider that there is a horizontal plane in which the aircraft is moving to deal with as well. I bet if you took your numbers attained from your formula and subtracted from the aircraft's top speed, you'll probably come close to the best climb (Vx) speed

    Something else - a Cub could climb at 600' per minute at sea level (maybe even more depending on model and load). Do the math based on your formula!
     
  3. Njaco

    Njaco The Pop-Tart Whisperer
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    Not an aviation whizz here but from my construction days, I would say you're not taking into account that the plane is climbing and therefore on a straight line the speed may not be as fast as actual speed. Think of a pitched roof. Going straight across the building you would have a straight speed, whereas climbing up the roof, you're still covering that straight line but at a slower speed, although the object itself is maintaining speed.

    I think. :)
     
  4. Marcel

    Marcel Well-Known Member

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    You mean groundspeed is less in a climb. That's correct.
     
  5. Elvis

    Elvis Member

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    No real "formula" here, but since you asked, I'll show you exactly how I came to those conclusions I made in my opening post.

    Piper Cub = 600' / min.

    That means, every minute, it climbs 600 feet (I know, not really, but just go with me on this).

    There are 60 minutes in 1 hour.

    ...SO...

    600 x 60 = 36000 - This is the number of feet that Cub would travel (if it could) in one hour, based on that 600' / min. rate of speed.

    There's 5,280 feet in every mile.

    Since I've already determined the number of feet that rate of speed (climb) covers in one hour, all I have to do is divide....

    36000 / 5280 = 6.8181818

    This is the equivelent to the rate of climb you quoted, in Miles/Hour (MPH).....almost SEVEN. :shock:

    Its that easy.


    I do get what you guys are saying and you all have valid points, however, my point was simply the comparison of the numbers.
    A certain rate in FPM, compared to the same rate, only stated in MPH.
    The amount of difference is what surprised me.
    Frankly, I had always thought they were travelling much faster.




    Elvis
     
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