Aircraft Evolutionary cul-de-sac’s

Scratch said:

That's a really nice topic, Miragedriver, I like it.

There's 3 aircraft on top of my head that I would like to present here. I really like designes pushing the limits of aviation, if only just for the technical aspect. And most of times those planes are also just cool.
Here, it is the desire for speed and altitude.

First, then, is the XB-70 Valkyrie. Unfortunately, it became obsolete even before production started, due to the appearance of high altitude SAMs and ICBMs, wich could do the job better. Stealth tech wasn't far enough at the time to hide the plane long enough. On the contrary, I think the big cornered intakes were rather massive radar reflectors.
But the idea of a supersonic wave-rider is absolutely inspiring.

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XB-70 is a beatiful jet for the 1960s

Other failed projects might have progeny much later, as the XV-3 of the '50's is the forefather of the V-22 half a century later. But tail sitter fighters we'll never see again.
The oldest, and never actually build, was a project of 1944, the Focke-Wulf Triebfluegel. This is to me the most beautiful of the lot:
.
Then came two USN prototypes ship-based convoy protecting fighters with contra-rotating propellers, The Lockheed XFV and the Convair XFY


And there were a pair of jet powered ones, the Ryan X-13 and the French SNECMA Coléoptère:



We will not see their likes again, although NASA is experimenting with an electric personal tail sitter aircraft called Puffin:

why can't tailsitter fighters be constructed as unmanned aircrafts with some booster rockets?

Kurt said:

why can't tailsitter fighters be constructed as unmanned aircrafts with some booster rockets?

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That too was done. The Bachem Natter was launched vertically, but at the end of the mission the cockpit split from the remainder of the aircraft and both parts were to land by parachute: .
Because it wasn't to land on its tail it is not included among the tail sitters. And that landing on the tail was the main weakness of the concept.

delft said:

We will not see their likes again, although NASA is experimenting with an electric personal tail sitter aircraft called Puffin:

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Man! I would love to have a Puffin!!!!!!!

---------- Post added at 03:39 AM ---------- Previous post was at 03:24 AM ----------

It’s interesting to see how the evolution of aircraft causes a dead end for some designs and a projection to a final design in others. An example of that is the titrotor aircraft.
In this example the X-22 evolves into the XC-142 and then into the V-22

The X-22


The XC-142


The V-22

In this example the X-22 evolves into the XC-142 and then into the V-22

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This is not a question of evolution of one these aircraft to another. They belong to three of several separate evolutionary threads, respectively tandem wing ducted fan, tilt wing and single wing tilt rotor. There were also
the tandem wing tilt rotor, for example Curtiss-Wright X-19 ( )
the rotor in wing, for example the Ryan XV-5 Vertifan ( )
the augmented thrust concept, for example Lockheed XV-4 ( )
the lift jet aircraft, for example the Dornier Do-31 ( ).
the gyroplane, for example the Fairey Rotodyne ( )

There were also concepts for stopping and even stowing lifting rotors. And there were surely experiments in directions I didn't read about.

This is really a whole zoo of dead ends. But some show signs of revival. The gyroplane is being build in some numbers but only for a single pilot or with at most a few passengers.

delft said:

This is not a question of evolution of one these aircraft to another. They belong to three of several separate evolutionary threads, respectively tandem wing ducted fan, tilt wing and single wing tilt rotor.

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Thank you for the clarification. I tell you this whole series of dead ends and experimental aircraft is loaded with interesting and weird designs. It would make a great coffee table book. It’s interesting how swing wing aircraft where the latest advancement and now they’ve gone into the evolutionary garbage heep.
There is something about that Lockheed XV-4 that reminds me of the Yak-36. Great stuff delft!

I was thinking of tackling swing wing aircraft next, but I really know little more than is told by Wikipedia - - so lets look at fighters using lift jet engines. Those too form quite a zoo.
First there were, beside the two tail sitter jets already mentioned, the flying jet engines - the Rolls Royce Flying Bedstead with two horizontally mounted Derwent engines and the Soviet Turbolot with one engine mounted vertically.
Real VTOL aircraft with vertically mounted engines were the Short SC-1 with four lift engines and a propulsion engine, the Lockheed XV-4B, also with four lift engines where the earlier XV-4 had the thrust augmentation box, and with two propulsion engines, and the French Balzac V and Mirage IIIV each with eight Rolls Royce lift engines and a single propulsion engine. The weight penalty for separate take off engines is of course horrendous. A strange bird in this aviary is the MiG-23PD, a STOL aircraft developed parallel to the ordinary MiG-23 with a delta wing and a pair of lift engines behind the cockpit.
Real experimental aircraft with horizontal engines begin with the Bell X-14, the Hawker P.1127 Kestrel and the Yak-36 Freehand. The X-14 let nowhere, the Kestrel let to the well known Harrier and the Yak-36 let to the Yak-38. X-14 and Yak-36 had a pair of engines in the forward fuselage from which the efflux could be directed down.
The Harrier and its developments use a single engine with four jet pipes that can be directed down.
The Yak-38 used a single cruise engine with a pair of jet pipes and directly behind the cockpit a pair of lift engines. It's intended successor Yak-141 had a single cruise engine from which the exhaust can be directed down and again a pair of lift engines behind the cockpit.
The last of the line is the LM F-35B similar to and partly based on the experience with the Yak-141, but with a cruise engine that drives in vertical flight mode a fan behind the cockpit by way of a shaft.
The odd man out among these families of VTOL/STOVL fighters is the German VJ-101C with a pair of engines swiveling on each wing tip and a pair of the same type of engines build in behind the cockpit as lift engines. The only one of the lot that I have seen.

Now what about them?
The main problem with them is the ingestion of engine exhaust gas. When that happens thrust decreases greatly and you are in extreme danger.
The second problem is the interaction with the ground:
* the engine efflux might generate low pressure on the bottom of the fuselage or even the wing so the aircraft is sucked to the ground instead of lifted away
* a different matter is the swirling up of sand or concrete or asphalt from the surface the aircraft tries to land on or takes off from. On a ship you don't want to burn off the anti-skid layer or even burn pits in the steel deck.
The aircraft were originally thought of as operating from a short distance behind a front line. In a world where MRLS have ranges up to 400 km that is not a healthy concept. For use from aircraft carriers you prefer to build the STOL characteristics into the ship not the aircraft because of the huge penalty in weight and maintenance.
So in short this is a cul-de-sac and the F-35B will be its very last manifestation.

Interesting that we are thinking along the same lines. I’ve always had a fascination with the swing-wing design ever since I first saw that Su-22 and then the Mig-23. The continual push for a STOL aircraft during the 70’s was in full force with the VTOL and STOL competing for funds. The most successful of the VTOL, in my humble opinion, is the Harrier. I believe that a version of the Harrier (AV-8) is still in use with the American Marines. This is truly an amazing aircraft, capable of close air support and point air defense.

It is interesting that the solution to the VTOL concept utilizing the swing wing method was solved with the use of canards, as exemplified by the Israeli modification of the Mirage III/V into the Kfir C2. Now we see Canards on many fighter aircraft to reduce take-off (and to a certain extent landing) runs. Such as the JAS-37, JAS-39, Rafale, Typhoon, SU-35/37 etc…

Just out of curiosity I would like to see what a Mig-23 with out swing wings would have looked like and performed. With a wing configuration similar to the F-15 or the Mig-29. Something to think about.

PS the Mig-23PD looks like the love child of the Mig-23 and the French Balzac V

Hey delft, any thoughts on the Lavi? Even though it is smaller than the F-16, one can only imagine what a great combat aircraft this would have been. In reading some articles regarding Lavi, the design engineers mentioned that they purposely designed the aircraft to be a fully combat capable as an OCU aircraft first, thereby allowing for more fuel and avionics in the single seat version. They also mentioned that this was also done to allow more room for growth in the platform.

[video=youtube;zWVxFZp-ZLc]http://www.youtube.com/watch?v=zWVxFZp-ZLc[/video]