Could aircraft have switchable wings to increase roles?

Discussion in 'Aviation' started by DerGiLLster, May 24, 2015.

  1. DerGiLLster

    DerGiLLster Member

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    Okay so this come into my mind as I was thinking of ways to increase the roles of a plane without having to resort to multiple planes in the role. What if they made a plane with specially detachable wings? There would be two versions of the wings, swept and straight. Imagine swept being used to decrease drag and give promising performance in the fighter or interceptor role. The straight wings would be intended for the ground attack or the dive bomber role.

    Would such an idea be possible to implement? Giving the aircraft wings for the appropriate roles? Or I am just thinking too much, with it being good to stop there and make the planes separate in their roles?
     
  2. GregP

    GregP Well-Known Member

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    Possible buy wildly improbable.

    All aircraft are compromises. Any aircraft that was deisgned as a fighter would be very difficult to adapt for ground attack with just a wing change. There would be basic fuselage and engine and engine intake differences together with completely different requirements for landing gear and the electronics fitted.
     
  3. GrauGeist

    GrauGeist Well-Known Member

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    The Me P.1101 V3 had variable pitch wings.
     
  4. GregP

    GregP Well-Known Member

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    I figured "switchable wings" meant a wing change. A variable sweep units would have benefits, but would not ne optimal for fighters and then ground attack, That wasn't really possible until the F-14D and that was well more than 30 years after WWII. I can't think of another swing-wing wih the prowess at bith air-to-air and air-to-ground that the F-14D had. Most were one or the other primarily, but the "Bombcat" could do either quite effectively.

    Swing wings would help a fighter, assuming they had the metalurgy and design skill to pull it off in mass production during WWII. I doubt that greatly, but I suppose stranger thangs might have happened.
     
  5. GrauGeist

    GrauGeist Well-Known Member

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    The B-1, F-14 and F-111 were able to adjust the sweep angle of the wings in flight, the P.1101 was manually adjusted prior to flight.

    Still, it was a huge step foreward for it's time, all things considered.
     
  6. fastmongrel

    fastmongrel Well-Known Member

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    Only aircraft I have ever heard of that could have its wings swapped quickly and easily at squadron level was the Hawker Hurricane. Apparently the wing could be switched in about 2 hours but needed a crane and a good sized crew. Doubt it was ever done for operational reasons though I dont think there would be any need.
     
  7. tyrodtom

    tyrodtom Well-Known Member

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    If the wings used the same mounting points, wouldn't swept wings introduce problems with a difference in center of lift from the center of gravity, verses the straight wings.
    I heard of a few aircraft that had different sets of wings with different spans.
     
  8. drgondog

    drgondog Well-Known Member

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    A P-51 could have benefitted. A wing switch would not have been extremely labor intensive. I could have had an Interceptor wing for example with two 50 gallon wing fuel tanks, an increased area wing to boost the turn rate, probably by increasing the chord rather than the span so as not to decrease or limit the roll rate. The decrease in the fuel weight of 770+ pounds GW puts a P-51B in a Spitfire class for both climb and turn and roll with a Spit XIV.

    It would be slightly slower with greater Profile drag due to extra friction of the wing increased surface. The Induced Drag of the new wing has offsetting factors. 1.) the CL for a level flight condition will be lower because the GW is 700 pounds lower while the wing area increases also -----> so Induced drag, while impacted slightly by reduced aspect ration of a deeper chord wing, will have a lesser CL^^2 in the numerator.

    An added benefit to the greater chord length is increased space for 20 mm Hispano's with only short extension for barrels - making this combination very effective as a longer range point interceptor. It should easily approach the lower dash number P-47D's in Combat radius ~ 250-300 miles.

    Last benefit is that it would easily carry 2x1000 pound external loads for CAS with safer GWmax takeoff margins..

    At a minimum it would require a field capable modification of lower radiator cowl, built in fuselage attach structure in place to remove the lower cowl and plumbing, detach the wing at CL and longeron attach, replace the new wing, plumbing and new lower cowl (similar to P-51H).

    The MAC increases about 8" for an increase of wing area from 233 sq ft to 257sq feet with same span.

    For a P-51B the Gross weight fully loaded internally (no tanks) is 9332 pounds, 9842 with 85 gallons in fuse tank. W/L = 9842/233= 42.24

    P-51B+ GW is P-51B GW less 129 gallons of internal fuel = 9842 - (129x6) = 9068 fully loaded internal 150 gallons plus 4x50 cal and 1400 rounds of ammo. W/L = 35.3

    Additional factors. Rolling Moment of inertia after removing 300 pounds per wing of fuel decreases and the aileron authority should increase with same aileron area despite increase in wing area per side of 12 sq ft. I would estimate that a Conservative Parasite drag increase is linear with increase in wing area. The parasite/friction drag for the P-51 is about 30% of total Drag for zero lift at RN=9x10^^6 but as the RN is a factor of the new MAC the RN is higher for given velocity. Skin Friction coefficient is inversely proportional to Square Root of RN ----------> so the skin friction will be less than predicted for the increase in wing area. I would estimate that the CDo increases less than 3%.

    CDo = .0165*1.03 = .016995. The induced Drag CDi Decreases for given climb velocity as noted below is 65% of the Old P-51B for same altitude, Velocity and Thrust Horsepower

    But CLnew = .92*W/(q*1.1*S)*V^^2 = k*(.92)/(1.1)= .836 of CL for P-51B: where k=W/(rho*S*V^^2)of old P-51B

    Induced Drag = CL^^2/(pi*AR*e): AR is 5.32 or 10% less. So, Induced Drag Coefficient of new P-51B = K*(.836)^^2/.9 where k= 1/(Pi*e*AR) -----------> new induced drag = 65% of the old P-51B as a result of greater wing and lower weight.

    I don't have the time to run a parallel set of numbers to illustrate
    1.) Parasite Drag (actual) for both ships in climb but the new P-51 will be about 3% greater.
    2.) Induced Drag (actual) for both ships in climb but the new P-51B will be significantly less
    3.) the total Drag needs to have a Velocity and altitude picked
    4.) The Thrust HP Available can be closely calculated based on the charts from the 1650-7 with equal assumptions for efficiency at max power, Velocity more or less equal and Density the same.
    5.) Then solve each P-51B for Total Drag and Total Thrust based on different weights and wing area
    6.) Then solve for Required Power at that Velocity by setting T*V-D*V = 0; T=D

    The new P-51B will fly rings around the old B except in straight out speed.

    Induced drag dominates at max ROC for the piston engine fighter, as well as in non-asymmetric flight.
    The new P-51B will have a slightly lower CLmax due to lower AR.
    The new P-51B should have a greater ceiling as well as agility at high altitudes with greater wing area

    .
    .
     
  9. tomo pauk

    tomo pauk Creator of Interesting Threads

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    It would've been interesting to see the Corsair and Hellcat with a wing that is both of lower area and thickness - less 'carrier friendly' (say, for Marines and RAF/RAAF/RNZAF), but with greater level speed and range.
    A sidenote re. bigger wings is that G limit might go easily down. Eg. for the 'normal' Fw 190A-3, with take off weight of 3850 kg, the G limit was 6.93; for the tested lightweight version (no MGs their ammo, decreased protection etc; 3660 kg) the G limit was at 'circa 7.15'; for the lightweight but with longer wings (3700 kg) it was down to 6.0. The Ta 152C was at 5.5, the Ta 152H (long wing) was at 5 G, both already for light fuel load.
    The Hurricane with smaller and thinner wings would've also been interesting, hopefully with a better layout of coling system to help out with streamlining.
     
  10. Shortround6

    Shortround6 Well-Known Member

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    You don't need swept wings until you are way-way over 400mph so I don't know how much good this does for propeller driven aircraft.

    Now do you build your planes like a Bf 109 so you can change wings with the plane sitting on it's own landing gear or do you need a crane to hold the fuselage up while a "new" wing with it's own landing gear is wheeled underneath?

    Does each fuselage get two sets of armament if wing guns are used or do the armorers/mechanics have to swap the wing guns back and forth?

    And Murphy's law says "whatever wings are on the plane/s at the moment will be the wrong ones for the next mission..............especially if needed in a hurry."
     
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  11. pbehn

    pbehn Well-Known Member

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    Bearing in mind Nagumo's dilemma at Midway merely caught between torpedos and bombs imagine being caught switching wings on a squadron!
     
  12. kool kitty89

    kool kitty89 Well-Known Member

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    Reducing wing area probably wouldn't be as important as airfoil profile. It might even be that decreasing thickness:chord ratio at the expense of increasing area could reduce transonic drag and increase critical mach. Even doing this only at the thickest portions of the wing (near the root) could have been significant. Adding leading-edge extensions (possibly using a sharper leading edge and different airfoil type as well) at the roots and extending the oil cooler intakes could be significant in this regard. (similar in shape to the P-51's roots or the Me 262 HG-I's wing root extension, or possibly extending both the leading and trailing edge similar to the P-80 or F9F)

    Wing extensions around the central pod may have helped the P-38's mach limiting problems as well given both the thick airfoil section and high speed flow inboard of the nacelles. (not sure if such would help the P-47 as much, short of a total wing redesign using thinner airfoil along the full span, or extending the chord along the full span to similar effect -that may have been more useful than the P-47N's extension, though probably a bigger production shift and more valuable had the P-47J's cowling been adopted)


    This is something I've wondered about early Jet aircraft as well, particularly cases where a modified straight wing might have been simpler to adapt to the existing airframe without more substantial redesigns like the F-84F and F9F Cougar. Extending the chord of the existing wings seems like a more straightforward structural redesign than making the existing wing thinner (more like the F-94C adopted) given internal stores capacity (which might be increased), mounting/spar arrangements, etc. Plus, some degree of leading edge sweep or low degree delta planform is possible (granted, that would be more incidental prior to formal swept wing research data). I do recall engineering drawings of Gloster Meteor derivatives with leading edge extensions making it more of a delta shape, including the P.262 also employing a slab tailplane.
    Plane Talking - HyperScale's Aircraft Scale Model Discussion Forum: Gloster Meteor question

    http://i729.photobucket.com/albums/ww291/joncarrfarrelly/GLOSTER_P262_P300_01.png



    Doesn't that depend somewhat on the airfoil thickness and profile used? Very thick wings could have sweepback much more useful at lower speeds, but I suppose the counter-argument would be towards how many of those aircraft would just be better off with larger area, broader chord wings with thinner profiles in the first place?

    You could also have wings swappable outboard of the roots/landing gear (more like the Hurricane) rather than just at the fuselage or avoid the use of a crane by including strong points under the fuselage to be supported by jacks or support struts, or dollies of some sort.



    That said, the whole idea of wings being (standard) swapped in the field seems a bit impractical. Having a fairly modular design with different variations assembled at the factory would make more sense, but even then having changes like wing chord extensions would be problematic in terms of matching wing-fuselage boundaries and proper wing fillets. (still potentially much greater parts commonality than completely different aircraft) And in the case of something like the Hurricane, it would be the outer wing portions that would be easier to replace, and the thick root section might be more practical to extend the chord of to make any new airfoil profile changes.

    It may also eventuate that one wing becomes clearly superior in nearly all applications and becomes the new standard.
     
  13. wuzak

    wuzak Well-Known Member

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    The Spitfire's wing tips could be changed in the field - from standard to extended wing tips for high altitude work, to the clipped wing tips used for low altitudes and to help increase roll rate.

    Changing the wing may only get you so far. You may also need to change the engine, or at least retune the engine, to make best advantage from the wing change.
     
  14. norab

    norab Well-Known Member

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    Howard Hughes record setting plane from the thirties did indeed have two sets of wings that could be swapped. A short span set for pylon racing and a long span set for setting distance speed records.
     
  15. The Basket

    The Basket Well-Known Member

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    In theory great idea.
    In practice no. As this was never done I would assume it was never a starter.
    You would have to change a squadrons worth of aircraft at the same time. The logistics of that especially off base would be horrific.
    Plus aircraft would have to be deliberately designed to make wing swap as easy as possible. Plus metal fatigue from constant changing. Also the aircraft would be totally new as the new wing would have different stall and handling so the pilot would need to know which wing he has on and its stall. Reminds me of a MiG-23 story as the Flogger would behave different at each wing sweep and the pilot had to know the sweep and the flight envelope of that sweep so he was flying 3 aircraft at the same time.
    Trying to swap a B-29 wings at night? In a hurry? Ohhh.
    I like the idea as an engineering concept but as a total FAFF then not close.
     
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