VTOL tail sitters, can they work now?

The big problem with ACs like the Ryan Verti-jet and the French Coleoptere was the difficulty with landing / hovering. The pilot sitting atop the craft couldn’t easily see the ground he was trying to land on.

BUT, today with computer controls, compact radars and tiny cameras, wouldn’t they be practical? Wouldn’t it be better than the complex mechanical systems used in the F-35 and Harrier?

I agree entirely plus I'd add that with UAVs, the practicality is even greater. The real problem with this, and any other VTOL design, is that it needs more thrust than weight.

A tailsitting UAV, Aurora flight Science's GoldernEye 100:


[edit on 7-6-2006 by planeman]

Quick sketch of a conceptual tail-sitting manned fighter:


the obvious advantage is that the landing gear is much more compact and probably lighter. This frees up a lot of fuselage volume which could be replaced by internal weapons bays or more fuel, or simply a smaller fuselage.

Even if they were technically feasible they wouldn’t be practical. A jet powered, combat tail sitter would have several key disadvantages compared to “conventional” STOVL aircraft. The fact that they could only take off and land vertically is a major disadvantage given that this would require a huge amount of internal space to be given over in order to properly cool the engine, the aircraft would need a lower max take off weight, it would not have as good bring back capabilities since it can’t perform a rolling landing, it couldn’t really perform an emergency landing, moving the aircraft around on the ground would be a bit of a bugger, small hangers might have trouble, plus many other little issues here and there. They just aren’t as good as more conventional STOVL aircraft in my opinion.

That doesn’t of course apply to vehicles like Goldeneye since they’re ducted fan powered ISTAR systems.

Mike, you can land tail-sitting as well as take-off that way.

Yeah that's my point, you have to take off and you have land vertically, you can't perform rolling take offs and landings. Purely VTOL operation is not practical and why it isn't practiced much, if at all.

I'm sure there are benfits...

^^^^

That’s exactly my idea. Imagine how many more tail sitters a Nimitz could carry than conventional aircraft. It could even incorporate launch tubes like on SSNs, so as to increase take off weight. Tail sitters wouldn’t require risky high speed carrier trap recoveries either.

Originally posted by Number23
^^^^

That’s exactly my idea. Imagine how many more tail sitters a Nimitz could carry than conventional aircraft. It could even incorporate launch tubes like on SSNs, so as to increase take off weight. Tail sitters wouldn’t require risky high speed carrier trap recoveries either.

Sorry, couldn't resist www.youtube.com...

You blokes might find this of interest then, its the cover art for the latest edition of the 'Secret Projects' series, this one covering Soviet fighters, obviously.



The project is the Sukhoi Shkval, an Interceptor design from 1963.

I think perhaps the main limitation of the tail-sitters is the amount of time it could take to lift off the ground. And then you have to factor in the additional time taken to level off safely without crashing oneself into the ground. During this time the aircraft would be a sitting duck for missiles or even guns. Cluster bombs would also create problems.

The comment has already been made that a UAV would be perfect for such a role, and with this I agree wholeheartedly. It would make a takeoff much easier and less preparation would be necessary. Click button, launch thing.

An interesting though had occured to me before about an interesting tail-sitter-related design. Instead of having the aircraft sit on the ground, what about launching it out of something, like maybe a submarine? It would be an excellent UAV-launching idea, particularly since it could beam important information about troop movements to submarines stationed nearby.

The picture of the tail-sitter on the flight deck of the destroyer looks neat, but I think a little impractical. I doubt you could land a tail-sitting jet on that spot in anything above a flat calm sea.

The advantages of a Harrier-type VTOL landing are the relative position of the C of G, the spread of the contact points and the ability of the landing gear to absorb the shock of landing. And it's still pretty hairy landing a Harrier on an Invincible-class carrier in rough seas.

So imagine trying to land a tail-sitter on a ship one-fifth the size, judging the smaller contact perimeter, with the risk that a misjudged roll of the ship could swat the tailplane and bring the plane down in short order, or simply topple it once it's down.

The Goldeneye has a much better balance of the CofG and the landing gear, but you'd find it hard to design a useful manned platform around those parameters.

As for the"Sea Eagle", go look at the Skydiver from the Gerry Anderson TV series "UFO", or the flying sub from "Voyage to the Bottom of the Sea", both of which look funkier (but sooooo dated :lol

G

I love tail-sitters theres lots they could do and about landing howed they
land on the moon not on runways and the tech is beter now. You could always
put them in somthing like an ICBM tube theyed be out of fire and could launch
quicky.

[edit on 7-6-2006 by cylon555]

wrt the amount of fuel used on take off - how about a separate tank that it just big enough to hold the amount of fuel required to lift off and transition, it could then be droppped (by parachute?) to be reused (it is still over freindly territory after all) and the plane flies on with full tanks.


Rip away

VTOL Tailsitter UAV would probably be a lot better performance vice than Firescout type rotary UAVs for ASW and Ship protection. They could prbably do limited A2A duties as well. and the droptank idea sounds good for me.

How about the use of a discardable rocket booster for take off assistance?

The drop-off fuel tank isn't a bad idea but I think I can see a pitfall. The fuel and the assembly will add more weight to a UAV that will most likely be designed to be as light as possible. And fuel can weigh a LOT.

I don't know the formula of the jet fuel used, but think of it this way. Get a couple litres of water and feel how heavy that is. Water is 18.02 grams per mol (If you don't know what this means, the units don't matter-the comparison between the numbers does). Octane (gasoline) has a molecular formula of C8H18. That means it is 114.26 grams per mol. So with equal amounts of Octane and water the Octane will be about 6.3 times heavier than the water. And you were probably complaining about how heavy the water was . I'm not saying octane is jet fuel, but it is simply for comparison. I am fairly sure that the Jet Fuel will be a hydrocarbon of some sort. Unfortunately the sheer variety of Jet Fuels has rendered me unable to find what actually goes into those things, even after several googles.

Originally posted by waynos
wrt the amount of fuel used on take off - how about a separate tank that it just big enough to hold the amount of fuel required to lift off and transition, it could then be droppped (by parachute?) to be reused (it is still over freindly territory after all) and the plane flies on with full tanks.


Rip away

Or even better a RATO.

[edit on 8-6-2006 by Number23]

I know the US Air Force has portable arresting gear for use on runways so that wouldn't be a problem. I'd like to see the developement of a portable catapult system like the Navy uses on its carriers. This would resolve the whole STOL issue. It would also allow for the usage of common aircaft between the Air Force and Navy.

For a UAV, I think the tail sitter concept would be ideal in some ways. As other have mentioned they would be perfect for the Navy, where space on the flight deck is at a preamium. The biggest obsticals for the navy have always been space and weight. This could to some degree solve both. The main reason weight is such a big issue for carriers is because of the safety limits of the Arresting gear, and the catapult. If you can bypass these issues, you can expand on the capibilities of carrirer-based aircraft.

Now the big question: What are the current practical weight limits for a VTOL aircraft?

If we know/knew this, we might be able to make some realistic guesses about where this technology is headed.

Tim

I don't think that a Tail sitter VTOL would be of much use to the Navy due to a lack of stability in rough seas. The size if the tail to prevent the aircraft from tipping over, combined with the wingspan and increased height would cause more storage problems than aircraft in a conventional configuration.