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Vertical lift aircraft fuel longevity

  1. Oct 1, 2007 #1
    Anyone know how long a typical lets say news helicopter can last in the air given how much fuel it holds?

    I am not sure but I heard a news helicopter or a police helicopter probably wont last more than 3 hours in the air.

    Some military transport helicopters can only do about 2 and attack helicopters like the apache longbow attack helicopter probably wont last more than 30 minutes due to its weight from holding armaments.

    Some vertical takeoff aircrafts (harrier) probably can't last more than 2 minutes before using too much fuel to land safely.

    This is all what I have heard from other sources, I was wondering if anyone can shed some light on this subject.
     
  2. jcsd
  3. Oct 1, 2007 #2
    As for the Harrier, if we take internal fuel capacity [itex]m_{fint}[/itex] and normal takeoff weight [itex]m_{to}[/itex] from this page, and specific fuel consumption [itex]c_f[/itex] of its Pegasus engine from here, and equating thrust to weight during hover, the maximum hover time would be:

    [tex]
    T_{\rm{hover}} = \int_{0}^{m_{fint}}\frac{d m_f}{(m_{to} - m_f) c_f} = \frac{1}{c_f}\ln\frac{m_{to}}{m_{to} - m_{fint}} \gtrapprox 32~[\rm{min}]
    [/tex]

    although with an approximation that [itex]c_f[/itex] remains constant in the covered thrust range.

    Also, I can't say whether all the powerplant elements involved are rated to sustain such long hover, as it's pretty much useless (unlike for a helicopter).

    --
    Chusslove Illich (Часлав Илић)
     
  4. Oct 1, 2007 #3

    FredGarvin

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    Science Advisor

    It is going to be entirely dependent on a couple of factors:

    1) Flight location. You are not going to get the same performance out of the same aircraft you get a seal level at somewhere in the Rocky Mountains or a desert environment. As soon as you start adding one of the "three H's" (high, hot, humid) you pay a price in performance.

    2) Loading. Depending on the loads needed to carry, the fuel usage differs hugely.

    From my experience, 3 hours in the air is a pretty decent estimate for most civil applications. We (CH-47s) were along the lines of 4 hours, but again, that depended on what our mission was and what we were carrying. With just a crew of 4 and no real internal/external load, I think we could push 4 hours.

    The AH-64 and the like (AH-1) has to have more than a 30 minute useful fuel load. There's just no way an aircraft could get in, do it's job and get to a refuel point in that time. I can't give you a number, but I'll do some snooping around to see if I can find some performance numbers.
     
  5. Oct 1, 2007 #4

    DaveC426913

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    Gold Member

    According to the Bell site, their most common, most popular commercial copter can "loiter" for 4.5 hours.

    Also, max range is about 700km, while max speed is about 210km/h (though you may not be able to simply combine those two).

    There's some PDF tech specs that give details.
     
  6. Oct 1, 2007 #5
    Probably should have done this sooner, but wikipedia states the maximum range and max speed of each attack helicopter, most of them are around 200 mile range and 200 mph max, so the flight time is probably around the ballpark of 1 to 2 hours.

    Generally for air support, the helicopters must have a remote base within 20 miles of the battlefield, so you can have a quick air support response and so they can have enough fuel to go there stay a while and come back. Same reason why Iwo Jima was such an important strategic location for the US. From there bombers could reach all over Japan, because B52s can't take off from aircraft carriers.
     
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