Me 163 tailless design

[Val. Pylypenko]

I'm reseaching the Me 163 for a talk I'm giving shortly and am attempting to ascertain the advantages of the tailless Lippisch configuration over the more conventional designs and why the RLM decreed that this radical new design be mated with the Walter rocket motor to produce the Me 163. A Google search for 'tailless aircraft' has found only complex aeronautical articles which are far beyond a non-technical person such as myself!

Any assistance would be most appreciated.

Regards to all on the Forum

Val. Pylypenko

[Grzesio]

Basically - shorter fuselage gives less drag and a lighter airframe (no need for carrying weight of a long fuselage needed for supporting the tailplane), it may be also necessary due to certain design features (e.g. necessity of placing an engine close to the centre of gravity).

These advantages are however partially neutralized by additional means of stabilizing a tailless a/c in flight. In the pre-fly-by-wire era this could be achieved by using a selfstabilizing wing profile (with a trailing edge bent upwards), which could stabilize even a straight winged tailless a/c, or a sweptback wings with twisted wingtips (with negative angle of attack, what was far more popular than selfstabilizing profile and actually used in Me 163 - what is easily seen in side views of the Komet) - such a wing has naturally more drag than an usual wing. There's also a problem with stabilizing momentum, as it varies with varying speed - basically a tailles aircraft is stable only in particular speed, when it is flying faster, it tends to lift its nose up (i.e. to climb), when it is flying slower, it tends to dive - this has to be constantly controlled by a pilot with an elevator or special trim flaps (in case of Komet these trim flaps were really big - what you can see on the inner trailing edges are trim not landing flaps). There can be also a problem with poor directional stability due to small momentum produced by the fin, placed on a short fuselage.
But generally a well designed tailless aircraft (such as the Komet) are light, powerful and stable in flight. For example the Me 163 diving with no power (after burning all the fuel) was faster than any Allied fighter trying to chase it.

Regards

Grzesiu

[Val. Pylypenko]

Dear Grzesio,

Thanks very much for your rapid and comprehensive reply to my question which I am (due to my embarrassing ignorance of aeronautical terminology) still attempting to digest - perhaps I should'nt have selected this particular topic for my talk, although now I'm committed!

I'll understand fully if you decline to assist me any further given your lengthy initial response but I am hoping you could possibly clarify a few things for me:

1. Most texts I've read simply refer to the 163 design as "taillesss", i.e. no horizontal elevators. How does this single feature (assuming the term doesn't include other features) improve performance? Was the weight saving c.f. a traditional tail such as to allow a significantly lighter airframe (and thus shorter fuselage)?
2. Am I correct in understanding that the swept-wing was the option selected to stabilize the tailless a/c in flight?
3. Finally, re your final comment "generally a well designed tailless aircraft (such as the Komet) are light, powerful and stable in flight", in relation to "powerful", I assume that as we are discussing airframe alone, you are referring to the tailless a/c tendency to climb when flying at high speed? If I'm wrong, beside the lighter airframe, why is this design generally more powerful than traditional designs?

Hope you can assist......and will understand if you choose otherwise

Regards

Val. Pylypenko (non-technical Luftwaffe buff)

[Grzesio]

Hi,

1. Lack of a tailplane gives a couple of advantages:
- the fuselage can be shorter, what gives less drag from the fuselage and less weight;
- the fuselage can be lighter even more, as it doesn't bear any loadings from the tailplane - so its construction can be more fragile; the tailplane itself is a little bit troublesome at high speeds, as e.g. it often tends to vibrate, it can also cause problems in certains angles of attack;
- there's no drag from the tailplane; these drag problems are even more important in high speed flight (OK, 'high speed' in 2nd WW standards, i.e. around 800 km/h and faster ) where drag is rapidly increasing.
2. Yes, you are right. Swept wing has of course another advantages in high speeds (lower local speed of air flow), but this knowledge was barely being born in the final stages of the 2nd WW; but swept wings were commonly used in tailless designs from the early 20th century.
3. Not exactly; let's imagine two aircraft, a conventional one and a tailless one, both with the same engine, fuel load, armament, purpose, etc. Generally the tailless one will be lighter, with better power-to-weight ratio (that's what I meant 'powerful'), faster (due to smaller drag and less problems at high speed) and probaly also more maneuverable. Not accidentally the Komet had such excellent glide characteristics, that people observing it in glide couldn't believe it flew with no power. Lippisch strongly opposed to an idea to equip the Komet with a tailplane (born at some moment due to certain problems experienced), what - according to his point of view - would ruin Komet's aerodynamical quality.
But we have to remember one more thing - the Komet was an early trial to built a high speed aircraft, when high speed flight was still a pretty mysterious area. The relatively simple shape of the Komet simply caused less problems at high speeds. The 'improved Komet', Me 263 with its longer fuselage and a teardrop canopy (but the same wings and fin) had actually lower allowed Mach number - 0.8 as opposed to Komet's 0,82 (and was generally heavier and slower, even with a more powerful engine), what means that the aircraft showed undesirable signs of nearing to the speed of sound at lower speed of flight.
Tailless aircraft hasn't become popular as they are really hard to design well, while almost the same quality can be achieved in more conventional way.
Tendency to climb is a fault rather than an advantage of a tailless design. As everyone who built a flying aircraft models knows , a conventional aircraft has its centre of gravity in approx. 1/4-1/3 of the wing chord. The tailplane simply counters any pitch deviations in the same fashion as a tail of a kite - the tailplane has basically no other influence on aircraft's behaviour in flight (save for steering of course ).
Canards and tailless aircraft (including flying wings) are nose heavy, i.e. their COG is placed more forward than in a conventional aircraft, what would cause it to dive instead of glide. This 'diving' momentum is balanced by opposing ('climbing') momentum produced by a canard (i.e. forward mounted horizontal stabilizer) in case of a canard aircraft, or selfstabilizing wing profile or twisted sweptback wings in case of a tailless aircraft. As the 'climbing' momentum is produced by airflow, it varies with varying speed and needs to be countered every time a canard or tailless aircraft changes its speed but has to stay at the same pitch. Simply - a tailless aircraft strongly rises its nose when accelerating, while decelerating makes it to dive.

Kind regards

Grzesio

[Val. Pylypenko]

Dear Grzesio,

Thanks very much for another very detailed response. Your assistance is much appreciated.

Regards,

Val. Pylypenko