Playing Devils Advocate - Why was the M262 so "advanced"?

[drgondog]

Just some info I have found.

Although it is often stated the Me 262 is a "swept wing" Designthe production Me 262 had a leading edge sweep of only 18.5°. This was done primarily to properly position the center of lift relative to the centre of mass and not for the aerodynamic benefit of increasing the critical Mach number of the wing. The sweep was too slight to achieve any significant advantage. This happened after the initial design of the aircraft, when the engines proved to be heavier than originally expected. On 1 March 1940, instead of moving the wing forward on its mount, the outer wing was positioned slightly backwards to the same end. The middle section of the wing remained unswept.. Based on data from the AVA Göttingen and windtunnel results, the middle section was later swept.
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While 18 degrees is not awesome the resultant normal velocity over the wing cross section is Vwing = Vfreestream x Cos alpha

where alpha = 18 and cos 18 = .95

A 5% change to Mcr over the wing is not awesom, but also not trivial. It represents the approximate speed difference between the Me 262 and P-80

This isn't entirely precise for a tapered wing and the formula should be applied to the sweep at the 1/4 chord line.

CORRECTION - There is a 5% reduction in relative velocity over the design airfoil - the resultant aero forces due to the difference in velocity reduction (in the specific case of Lift, Drag Rise and resultant Mcr) may not be precisely 5% due to other factors as Red Admiral pointed out..

 

[davebender]

No aircraft of that time could have withstood that concentration of firepower.

No aircraft of any time can withstand that sort of firepower. I am confident that a B2 bomber or F22 fighter hit with 4 x 30mm shells will be in serious trouble.

 

[Daviducus2]

Are you implying that a B2 bomber or F22 could withstand more damage than a B-17?

If so, I'm not so sure.

 

[Clay_Allison]

No aircraft of any time can withstand that sort of firepower. I am confident that a B2 bomber or F22 fighter hit with 4 x 30mm shells will be in serious trouble.

If I have to get sprayed with that, Gimme the A-10.

 

[Waynos]

I should have been more precise. The original swept wing outboard of engine nacelles was a direct result of having to make a late prototype development design change due to the unanticipated increased weight of the engines. Later, due to results obtained at Gottingen wind tunnel, the production design include sweep on the inboard wing also. The Advanced design versions Me 262 HG I used the improved high speed 'racing' canopy to reduce drag and the unbuilt HGII version incorporated both the canopy and a 35 degree sweep wing. IIRC the HGII would have next imbedded the engines next to the fuselage to further reduce drag (a la F-89) with the same 35 degree sweep.

What I should have been clearer about, is that expensive or not, the swept wing could have reverted back to original planform had the German aeros not validated the benefit to the 'accidental' sweep design', and further faound the benefits of sweeping the inboard section also.

Another design feature, not necessarily unique, was the low wing combined with triangular fuselage cross section was a nice low drag configuration with the added benifit of integrating the fuselage with the lower wing surface between the engine nacelles

So, planned or not, the resulting sweep did delay drag rise, and the overall parasite drag - despite two large engine nacelles - resulted in slightly better drag characteristics than either the Mustang or the P-80.

Thanks, yes. That is how I understand it, but thank you for the excellent summarisation. Perhaps I am being harsh but I discounted as being an example of advanced design purely because it was accidental while the theoretical benefits were already known at least in Germany and the USA, if not the UK too.

Parsifal - Granted with the weaponry. A good point, but one I think the Germans would have adopted whatever fighter was put into service. Unless there were technical reasons this could not be done?

As fighter speed went up, aspect ratio went down. The Meteor wing is fairly normal, thinner than contemporary piston engined aircraft to allow for higher speed flight. Most of the drag increase that led to a low Mcrit was from the nacelles, which where then lengthened to raise this. The wing itself is fairly normal. The later projects with swept and delta wings look pretty good.

The Su-9/MiG I-260 designs actually were technically influenced by the Me 262, not a simple "looks sort of like that" but the design itself was influenced. End product looked different after their own designers had played with it.

Doesn't look much like the Me-262. I wish I had some performance figures for the Meteor with F.2 engines to compare to the Mk III but haven't found any yet.

Sukhoi certainly adopted the general arrangement used by the 262 (because it worked) but no part of the design was copied from it, much less being tinkered with, it was completely new. Which I guess is just a different way of saying the same thing you did, except that to suggest that Sukhoi 'tinkered' with the 262 to get their own design would be wrong.

The photo of the Meteor you chose is actually a good one, and I was thinking of posting a similar one myself, because although axials are involved, it does not look anything like a 262. This is not only due to the design actually being very different, but also because the nacelles are also quite different to those on the 262. On the Su 9 the nacelles were not only like those of the 262, they were the same nacelles. This 3 view shows how different the Su 9 was, even to the extent that fuselage extends below the wing join as can be seen on the frontal view. The only image in which the Su-9 really looks like a 262 is a photograph of the prototype taken directly from the side.

Sorry if I haven't replied to your own post yet, The wife is nagging for her tea and its my turn to cook, sorry chaps

 

[red admiral]

A 5% change to Mcr over the wing is not awesom, but also not trivial.

It represents the wing presenting 5% less thickness to the oncoming flow, not a 5% reduction in drag or a 5% increase in Mcrit. Might possibly gain a bit in Mcrit but its more dependent on other airframe factors rather than just the wings. How control and stability are affected by increased Mach number etc.

 

[drgondog]

It represents the wing presenting 5% less thickness to the oncoming flow, not a 5% reduction in drag or a 5% increase in Mcrit. Might possibly gain a bit in Mcrit but its more dependent on other airframe factors rather than just the wings. How control and stability are affected by increased Mach number etc.

It [Cos (Sweep Angle)] IS the relative velocity to the representative aerodynamic shape of the wing - chord wise- as a function of the sweep angle and the free stream velocity... the reason I introduced the 1/4 chord reference is that swept wing design of tapered, trapezoidal wing is classically referenced to the 1/4 chord.

The aerodynamic flow properties (CL and CD) would be analyzed over the projected airfoil with a cross sectional cut perpendicular to the 1/4 chord point - not the wing section parallel to the free stream.

This is also the 'lines' that the aero's and the manufacturing engineers agree for tooling and rib design etc... the resultant 'contour' of the wing as the ribs are installed perpendicular to the spar and sheeted over.

So, if you meant to say that the 5% 'less thickness' is derived by obtaining a new airfoil with a resultant 'longer chord' cut parallel to the aircraft centerline , rather than perpendicular to 1/4 chord - that would not be correct.

You are right about other factors influencing Mcr, but the wings/nacelle bodies in this case are the key factors in Parasite drag for the Me 262.

Having said this - 1. Mcr reduction is not precisely 5%.- .you are correct about this - 2.) the key change introduced by the sweep is the reduction by 5% of relative chord wise velocity reduction over the wing; 3.AR is an important factor and thickness ratio is an important factor - all important during Preliminary design tradeoffs.

For this case thickness ratio is the same, AR is the same and sweep angle is changed from original design.

While the increase in Mcr for the Me 262 is not precisely 1/Cos 18 degrees I stand by this as the primary performance difference between the Me 262 and the P-80 relative to top speed...

 

[DerAdlerIstGelandet]

I always liked the meteor better, probably because it looks so much better.

Good thing most of us have better taste!

 

[Messy1]

Wow, getting nasty in here!

 

[Marcel]

ME262 advanced? Well it combined most of the newest trend in aviation, each in itself not unique, but the combination was. 1. Jet engines (the first operational a/c to have these) 2. Tricycle gear 3. Swept wings (whatever the reason was they used this_) and a few more. The Jet engines itself made it advanced already, together with the Meteor of course.

 

[davebender]

If I have to get sprayed with that, Gimme the A-10.

A-10 Thunderbolt II - Wikipedia, the free encyclopedia

The cockpit and parts of the flight-control system are protected by 900 pounds (408 kg) of titanium armor, referred to as a titanium "bathtub". The tub has been tested to withstand strikes from 23 mm cannon fire and some strikes from 57 mm rounds.

I agree. The pilot is likely to survive and eject after 30mm shells turn the wings and fuselage into swiss cheese. Now where is that rescue helicopter?

 

[Clay_Allison]

A-10 Thunderbolt II - Wikipedia, the free encyclopedia


I agree. The pilot is likely to survive and eject after 30mm shells turn the wings and fuselage into swiss cheese. Now where is that rescue helicopter?

I'm a big fan of surviving. Also the A-10 has been known to lose a surprising amount of itself and fly home so you had better hit it good. If I was the pilot I'd hope to see you or be notified of you a long way off so I can turn my plane and come at you with a burst of my own 30mm. It would be a long shot, but the Gatling has good range.

 

[drgondog]

I'm a big fan of surviving. Also the A-10 has been known to lose a surprising amount of itself and fly home so you had better hit it good. If I was the pilot I'd hope to see you or be notified of you a long way off so I can turn my plane and come at you with a burst of my own 30mm. It would be a long shot, but the Gatling has good range.

The 'smart' ammo allegedly now has an effective (accurate) range of 5 miles... AFAIK no A-10 has been shot down in Afghanistan (or Iraq) although two were badly damaged but RTB. I am not completely sure of my facts however.

BTW - the Taliban do have the latest Russian portable surface to air missles.

 

[vikingBerserker]

Honestly, I really do think it was incredibly advanced. I think it's biggest contribution IIRC was in being the first production jet fighter.

 

[Waynos]

When you look at it compared to the allied fighters it was facing then that view is quite clearly correct. I was thinking nore in terms of what it had that nobody else was doing. That may be harsh, but with some of the glowing terms that advanced German tech is discussed in you would expect nothing less. The truth is that it was clearly the best of the initial generation but, if you are looking for something unique there isn't anything. Unlike something like the Me163 which had no equivalent anywhere.

 

[The Basket]

Not true....The Me 163 was not unique if you do a quick search on the BOLKHOLVITINOV BI then you will learn of the Soviet rocket fighter.

It could do a supposed 560mph! in 1941!

Frenchman Roland Payen was designing little delta aircraft in the 1930s.

Germans put advanced aircraft into production which other countries did not.

 

[parsifal]

Japanese also built a rocket powered aircraft, broadly based on the Me 163, but still a different design

 

[vikingBerserker]

I believe the Me 163 flew and was put into production before the Berea-Isa B1 (05/15/42) flew - which was never put into production.

 

[Waynos]

Ooh, you bloody nitpickers OK I picked the wrong example (in reality I was thinking only about the Western allies so shouldn't have said 'anywhere', but you understand what I mean, yes?
AFAIK types like the P.1101, Ta183 and Miles M.52 did not have a direct equivalent in other countrues but did have features that became common on future types. Although maybe an oversimplification, that was how I was viewing 'advanced' when I started the thread.

In terms of operational aircraft I readily recognize the Me 262 was the most advanced of those.

 

[Butters]

The first liquid-fuelled rocket-propelled a/c was a He 112-b prototype modified to accomodate a rocket system designed by Werner von Braun in April, '37. The pilot was Erich Warsitz.

The He 176 was the first pure rocket a/c. Its first flight was on June 20,'39. Again, the pilot was Warsitz.

The Soviet B1 first flew on May 15, '42. The predecessor of the Me 163 was the Lippisch-designed DSF 194, which first flew in the spring of 1940. The Me 163A's first powered flights were in July, '41.

There were earlier flights made by powder-fuel rocket a/c, notably the Opel-Sander Rak.1.

The info is from William Green's, 'Rocket Fighter', Random House, '71.

JL