Scale ME-262

Discussion in 'Warbirds / Warbird Replicas' started by Saville, Oct 5, 2019.

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  1. Oct 14, 2019 #101

    Urquiola

    Urquiola

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    Please watch an image from above, a drawing of a Me-262 wing plan form, and that of a Lockheed 1011 TriStar, or DC-10.
    Almost identical! (For sure not in size)
    I never said today's Airliners are copies of Me-262, just that Me-262 wing plan form is found in many airliners, but not in others.
    Wing plan form is the result of aerodynamics research, and allied seized lots of it when entered Germany after may 1945, as an example: Theodore von Kármán, who was for a while attributed wrongly the 'JATO' invention, see images of Arado AR 234 jet bomber, when visiting a German facility, made an urgent call to the USA, indicating to discontinue the desing of a bomber they were involved with, to apply the swept back desings he watched in Germany.
    Please don't make me be misunderstood. Thanks. Regards. Salut +
     
  2. Oct 14, 2019 #102

    Aerowerx

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    IMHO the ME-262 is the only ww2 plane that's prettier than the P-51D.:)
     
    Battler Britton and pictsidhe like this.
  3. Oct 14, 2019 #103

    Aerowerx

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    It was Speedboat100 that said they were copies of the ME262, not you. That is entirely different from designing to the same principles. Two people, designing to the same "rules" will often come up with quite similar designs.
     
  4. Oct 14, 2019 #104

    pictsidhe

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    I dunno about the p-51 being pretty, but the 262 looked good to me.

    When I was young, I grafted Airfix 262 engines onto an Airfix Spitfire. It was utterly wrong. Willy and Mitchell should not be mixed!
     
  5. Oct 14, 2019 #105

    vhhjr

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    I have a decent collection of ME-262 literature and one is: "A Pictorial and Design Study Including the Pilot Handbook," published by Aviation Publications in 1972. It contains the POH written by the USAF for a flight test program conducted at Wright Patterson AFB in 1946. They had at least one of each version, single seat and two seat. The books preface states the engine life to be 25 hours max with a full overhaul every 8 hours. The book also details Hans Fay, a German pilot who landed his 262 at an allied base in 1945 giving an intact version for study.

    I loaded the three view drawing into the CAD program I use and looked at the canopy problem. The single place appears to be very difficult to scale down without upsizing the canopy. The two place version is a little better , but the same problem of narrow sill width. I would consider running the canopy sills a little lower on the fuselage making the opening wider. A skilled eye would notice, but that's a very small group. The ideal scale size appeared to me to be in the 66% range.

    Not that I am considering a 262 build, but I had a couple thoughts. The cost of two jet engines, such as in the Subsonex, would drive this project out of almost everyone's budget. We are currently doing some work with ducted fans and there are some very large ones available in the 200 mm+ range. The thrust is less than a jet and the cost a tenth. Built as a hybred with the engine/generator in the fuselage and electric motor fan drive might be a way to go. This avoids the need for a jet endorsement, would reduce the power plant cost and would almost eliminate the single engine performance problem. The original had considerable armament weight in the nose and a small battery pack could be located aft of the cockpit to keep the CG in place.

    Vince Homer
     
  6. Oct 14, 2019 #106

    Toobuilder

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    Not sure a flight report on the 262 is going to help here as even a "perfectly" scaled replica is going to have vastly different MMoI and Re. IMHO, a properly designed replica will address the "mission" of a sport airplane, not combat. That means new airfoil and control surface hinging moments, etc. If you're lucky, it will fly just like an RV.
     
  7. Oct 14, 2019 #107

    BBerson

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    Was it controllable with a loss of one engine from asymmetry? Did it have an ejection seat, or was the pilot considered expendable?
     
    Last edited: Oct 14, 2019
  8. Oct 14, 2019 #108

    nicknack

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    Hi I really like the idea of a hybrid ducted fan and did some basic maths early on and found that it has short comings
    Batteries are at the moment at best 1MJ/kg
    Engines are mostly 0.77hp/lb weight and only 25 to 30% efficient
    Ducted fan cannot put out more thrust than an optimized propeller.(for example a Cessna 172 150hp will have full throttle 465lb thrust). If this is taken as the limit then it is 3.1lb/hp thrust

    A lycoming O320 is abt 0.61hp/lb

    Electric motors at their best have between 5to10 kw/kg ie 3.04 to 6.08hp/lb (the Siemens 260kw=350hp weighs 50kg)

    So for a hybrid system that puts the same amount of thrust as a O320

    We need a electric engine weighing
    (465/3.1)/6.08=24.67lb
    Need 2 1 for propulsion and other for generating electricity.

    So total electric motor = 49lbs

    Batteries assuming only able to cover 5 mins flight, afterall the gas engine will provide all the electricity via generator.
    (5/60)*(150hp*0.7457*3600)kJ=33.5MJ
    So a battery pack of 33.5/.454=74lbs needed.

    Total weight of electric motors and battery for 5mins flight at same static thrust of a lycoming o320 in 172 Cessna = 74+49=123lbs

    An O320 weighs abt 270lb wet

    So to have abt the same weight as an O320 we need an engine that can put out 150hp and weighs 270-123=147lbs

    So need an efficient engine having specific power better than 1.02hp/lb
     
    Last edited: Oct 14, 2019
  9. Oct 14, 2019 #109

    Victor Bravo

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    I believe the comparisons of the ME-262 and many other jet aircraft are rooted in the fact that Willy and his design team on the 262 was the first (or one of the first) to figure out the "sweet spot" of the 35 degree wing sweep angle. If I'm not mistaken, more than one entire generation of fast subsonic airplane was based on that 35 degree sweep.
     
  10. Oct 14, 2019 #110

    pictsidhe

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    One reason that I picked the Hurricane was its comparatively docile behaviour for a WWII aircraft. When I looked at the effect of a much lower Re on stall behaviour, it did not look good with the original airfoils at my Re. The tip section loses more lift with lower Re than the root does. Hello tip stalls! New airfoils were needed to get the OK stalling behaviour back. Anyone scaling something down should check for a change in stall behaviour.
    My controls need to be altered drastically to get good feel and roll rate.
     
  11. Oct 14, 2019 #111

    pictsidhe

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    The sweep was added to fix the cg after the engine weight was significantly increased from design values...
     
  12. Oct 14, 2019 #112

    vhhjr

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    The POH says the minimum single engine speed was 165 mph. It would definitely fly one one engine, just not very slow.

    Yes, any scaled replica would be a different aircraft and would have it's own flight characteristics that would depend on design decisions of the builder.

    Any hybrid system would be a whole new design effort since there's nothing available off-the-shelf in that area. It might be easier to use a water cooled engine and certainly one with more modern design than a Lycoming, etc. Since there would be a limited battery back-up one might consider a high output 2-cycle to keep the weight down. A simpler possibility would be to use direct drive air cooled engines like Hirths, one in each nacelle. The development effort and cost goes down as does the reliability with 2 cycle engines, but you would have two and the 262 will fly on one.

    Now, if only there was a way to fit this into the Light Sport category!!

    Vince Homer
     
  13. Oct 14, 2019 #113

    Speedboat100

    Speedboat100

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    BS !
     
  14. Oct 14, 2019 #114

    Speedboat100

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    I bet Messerschmitt copied some from Heinkel design...which flew first. But not the wing..nose wheel maybe...and engine position/location.
     
  15. Oct 14, 2019 #115

    Victor Bravo

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    Wikipedia, at least, says that the sweep was put in because of CG. The 35 degree sweep had been proposed but not used. So I stand corrected.
     
  16. Oct 14, 2019 #116

    Speedboat100

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    Wiki is wrong...german research institutes knew exactly the benefits of a sweep angle. Captain Brown has reported these very openly.

    They had Mach 4 capable windtunnels during the war time already.

     
    Last edited: Oct 14, 2019
  17. Oct 14, 2019 #117

    Saville

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    I don't think so......
     
  18. Oct 14, 2019 #118

    SVSUSteve

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    Don't hold me to this but I seem to recall comments by one of the Luftwaffe pilots that flew it (or maybe it was Eric Brown...) that described the single engine handling of the original 262 as dicey at best.
     
  19. Oct 14, 2019 #119

    Speedboat100

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    I can agree if you say they chose swept wing...as it enhanced the speed and also set the CG right.
     

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  20. Oct 14, 2019 #120

    SVSUSteve

    SVSUSteve

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    Saville, just a friendly heads up. "Speedboat100" is our resident forum troll.
     

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