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At the loss of its acrobatic ability, could an airfoil similar to the 747 be downsized to allow a small jet to climb higher and extend its range?

This plane with its wing profile is highly acrobatic, but has a range of only 400 statute miles compared to the 900+ miles that its propeller counterparts gets. I believe it has much to do with the type of airfoil. Jim Bede, the designer of the plane, originally used a propeller version meant for travel, not acrobatics. As time progressed the profile of the wing evolved for more stability and acrobatic performance instead of stability and range.

Here I have a BD-5J Micro Jet with a wing span of 13.5 ft. enter image description here

and another version I call the BD-5HC High Cruise where I pasted on some 747 wings. Is it plausible to fly it in the same method as a 747 using lower altitude speed limits and increasing speed in higher altitudes?

enter image description here

I have another question related but with forward swept wings here, Are Foward Swept Wings for a Rear Propeller Airplane Feasible?

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  • $\begingroup$ I’m not an authority on aerofoils but a reliable way to increase the efficiency and therefore the range would be to use a larger aspect ratio wing. The aerofoil will typically be chosen to be optimal for the altitude, loading, speed etc rather than the other way round. As far as scaling goes, yes this does work reasonably well of the scaling factor isn’t too big; even model aircraft can use sections that are similar to big jets. $\endgroup$
    – Frog
    Commented Jan 1, 2023 at 19:53
  • $\begingroup$ Jetliner's airfoils are optimised to travel at some 900 kmh at 10'000 m altitude, I don't think that that airplane can reach such speeds and altitudes. Sweeping the wing back alters CG and aerodynamic center position i.e. longitudinal stability; plus wing becomes structurally heavier and more difficult to build; plus it brings some positive effect only at high subsonic speed. To get a better answer it should be made clearer the mission of the airplane: flying fast, far, agile, high, ... ? $\endgroup$
    – sophit
    Commented Jan 1, 2023 at 20:28
  • $\begingroup$ Re "As time progressed the profile of the wing evolved for more stability and acrobatic performance instead of stability and range." -- this is confusing. Maybe delete one of the "stability"s? $\endgroup$
    – quiet flyer
    Commented Jan 2, 2023 at 22:19
  • $\begingroup$ My thought is that in engineering, things are intertwined in a way that leads us to oversimplify cause and effect. Does the 747 perform the way it does because of the wing? Or was that wing design required by the performance characteristics of the plane? Advances in power plants tends to be the driving/limiting factor in airliner design, which in turn enables flight regimes that require a rethinking about wings. The question is “can I make a BD5 perform in a way that will benefit from that wing?” and not “will that wing improve the performance of the BD5”. $\endgroup$
    – Max R
    Commented Jan 2, 2023 at 22:56
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    $\begingroup$ There is a general, and fundamental reason why this won't work as you expect. You can scale the aerofoil, but you can't scale the air. (At this point I recall that all the aerodynamics I learnt was 40+ years ago). To get similar behaviour at different scales you need to fiddle with the Reynolds number. This is why wind tunnel testing is sometimes done at low (perhaps cryogenic) temperatures, amongst other things. $\endgroup$
    – CatchAsCatchCan
    Commented Jan 3, 2023 at 3:15

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The propeller version BD5 flys up to 230 mph and the jet version up to 320 mph, cruising at 270 mph. The wing for the the jet version is said to be "between the A and B versions" of the propeller craft.

First, the wing shape is more like a P51 Mustang for good reason. Those planes had to be built strong for military duty and also had to be low in drag to fly a long way. These so called "laminar wings" had nasty stall characteristics reminiscent of the shorter BD5 A wing. The 21 foot B wing was brought into the design after some crashes. Interestingly, a sailplane version was also planned.

cruising and top speeds for propeller and jet versions are too low to benefit from a high subsonic swept wing design$^1$.

The main reason for loss of cruising range when converting to the jet is that the tiny turbine engine simply did not have the fuel efficiency of the propeller engine it replaced, especially at the higher cruising speeds.

Adding a larger wing only helps up to the point where the added weight is compensated by less drag at the design cruise speed from a lower AoA.

Going higher could be done with a straight wing provided thrust was available at those altitudes and sufficient oxygen was carried for the pilot. The design should look more like a B-29 than a 747, or, perhaps more like this one, or, maybe this one.

The company that designed and produced the BD5 aircraft went bankrupt. Buyer beware.

$^1$ the jet version, at 30000 feet, would exceed 500 mph TAS if thrust was sufficient

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  • $\begingroup$ And quite importantly, that 747 is landing at about 150 kts. That P-51 wing isn’t just strong, it also reduces landing/takeoff speeds which opens up considerable flexibility in where I can deploy ground-based interceptors in a dynamic war front. And smaller brakes, smaller lift-spoiling requirements, non-reverser engines, all mean more fuel for range, more ammo. Swept wings change where planes can land, which militarily is then tied into strategic decisions about aircraft carriers and aerial refueling capability. Military deployment capability is itself a huge engineering variable. $\endgroup$
    – Max R
    Commented Jan 2, 2023 at 23:08
  • $\begingroup$ Nice answer. Today, small jet engines have came a long ways in efficiency. Yes, an Oxygen supply maybe needed. Just like their is a perfect wing length for efficiency, I imagine their is an optimal jet engine size. $\endgroup$
    – Justintimeforfun
    Commented Jan 3, 2023 at 19:23

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