Why did the Skunk Gang make the U-2 so finicky to land?

[XBe02Drvr]

Saw the video of the Dragon Lady doing carrier quals. That high L/D airframe cries out for a lift dump spoiler. Flaps alone on a high L/D wing deep in ground effect are a guarantee that you're going to just float right on past any normal runway. Especially if you have to keep your jet spooled up for a go-around. I've flown several different antique sailplanes that were design contemporaries of the U-2, and they had spoilers that were simple, robust, and effective. Made spot landings a piece of cake! One even had flaps AND spoilers. A flaps-only landing in that was a U-2 like affair. We must have some "skunkofiles" on board who can shed some light on this.

 

[swampyankee]

I don't think it was deliberate; I think it's a very common problem on lightly loaded, low-drag aircraft with large wing spans, the related tendency to "float" from ground effect, and jet engines, with their typically high residual thrust. While I am do not have the sort of worshipful awe of Kelly Johnson and the Skunk Works* some people show, I think it's not likely any design group could have greatly improved the landing characteristics of a U-2 type of aircraft, although I am quite astounded that they didn't include lift-dumping spoilers, as are common to sail planes.



* Kelly Johnson was the chief of design quite a few aircraft, starting with, I believe, the first Lockheed Electra.

 

[tyrodtom]

In the U-2 everything, everything, was sacrificed for two things, endurance and altitude.

The aircraft wasn't easy to fly at any part of it's flight envelope, takeoff, climb, level flight, descending. Why should landing itself be any different ?

Early in it's development 3 pilots were killed in takeoff/ and climbing incidents.

When the camera that was to be used on the U-2 was being developed , the designer needed 6 more inches of space for his camera. 6 more inches couldn't be found in the fuselage. He had to redesign his camera.
Spoilers would have added weight that they didn't want to add, the controls would have took a little room in the wing that they didn't want to provide for.

3 U-2Gs were built, they had a reinforced landing gear, arresting hook, and spoilers. Plus the U-2H is called carrier capable.

 

[FLYBOYJ]

I worked in the Skunk Works during the early 1980s - echo Tom, "In the U-2 everything, everything, was sacrificed for two things, endurance and altitude." Same holds true for the SR-71 with speed added to the equation.

 

[XBe02Drvr]

Thanks guys. Mystery resolved. Seems to this old sailpane pilot like a foolish trade-off, but I wasn't there. Discretionary drag management seems to be a weak point in quite a few pre-century series jets.
Moderator, I think this thread has served its purpose.

 

[soulezoo]

Many don't realize that part of the landing problem has to do with pilot visibility as well. They require a "chase car" running out far enough so the pilot can have a point of reference to land and the chase car is on radio giving instruction as to how far he is from pavement and etc. There is also the pick up with the "wing wheels", if you will.

I recall a time in the middle east at a host air base where a U2 took off, the pick up got the wing wheels and threw them in the truck. The officers in the truck were, shall we say, "less than professional" in their egress of the runway and one of the wing wheels fell out of the truck and was left in the runway where it was struck by a Mirage that was taking off. The base commander got him some that day and it wasn't pleasant. That was the second incident that day. Earlier, a crew chief left the aircraft forms in the wheel well in a tanker and the crew never noticed they were not in the flight station and took off! Well that binder and contents blew all over the runway when the plane took off.

There was a whole lot of "get some" on that.

 

[XBe02Drvr]

Many don't realize that part of the landing problem has to do with pilot visibility as well. They require a "chase car" running out far enough so the pilot can have a point of reference to land and the chase car is on radio giving instruction as to how far he is from pavement and etc.

Back to the thesis of the original post. With fully modulatable sailplane style spoilers that whole precarious chase car circus would have been unnecessary. With flaps and spoilers your flaps bleed the energy and the spoilers allow you to modulate your sink rate with no change in pitch attitude. With a little practice you can grease it on every time without a precise altitude reference. If you do happen to touch down with a higher than desired sink rate, you can kill the bounce by pinning it with full spoiler. So much simpler and safer than the chase car routine. (But of course chase cars are more macho and smack of test pilots and "The Right Stuff"!)
Cheers
Wes

 

[tyrodtom]

The U-2 was designed to perform a mission, everything else was secondary.
It wasn't safe to fly in any part of it's flight envelope.
Pilots died before they even got this thing to altitude.
Look at the very narrow airspeed band it had to stay in at altitude. A lot of people can't even drive a car with that narrow a restriction.

Spoilers would no doubt make it easier to land, but their added weight, no doubt, would have also reduced performance, which wasn't good enough as it was, events proved.

Anything that wasn't absolutely essential for flight that could be provided external of the of the aircraft was done, such as wing wheels dropped and left behind, landing assistance provided by chase cars, etc.

I find it interesting that some vehicle makers brag about the fact that their car is fast enough to be used as the chase car for the U-2, they seem to forget the aircraft has been operating almost 60 years. In the late 50's they had no trouble finding cars that could do it just as well .

 

[Zipper730]

Saw the video of the Dragon Lady doing carrier quals.

They operated a U-2 off the carrier?

Back to the thesis of the original post. With fully modulatable sailplane style spoilers that whole precarious chase car circus would have been unnecessary. With flaps and spoilers your flaps bleed the energy and the spoilers allow you to modulate your sink rate with no change in pitch attitude. With a little practice you can grease it on every time without a precise altitude reference. If you do happen to touch down with a higher than desired sink rate, you can kill the bounce by pinning it with full spoiler.

Makes sense to me.

 

[swampyankee]

A couple U-2s were built or modified for carrier ops. It probably came in slower than half the last generation of piston-engined aircraft. I don't know if they ever operated off carriers except for that testing.

 

[Zipper730]

It probably came in slower than half the last generation of piston-engined aircraft. I don't know if they ever operated off carriers except for that testing.

How much strengthening was needed for the role?

 

[XBe02Drvr]

With flaps and spoilers your flaps bleed the energy and the spoilers allow you to modulate your sink rate with no change in pitch attitude. With a little practice you can grease it on every time without a precise altitude reference. If you do happen to touch down with a higher than desired sink rate, you can kill the bounce by pinning it with full spoiler.

The problem with a flap-equipped spoiler-less sailplane like the U-2 with its bicycle landing gear and the main wheel forward of the CG is that if you touch down with any appreciable sink rate, inertia drives the tail down until the after mainwheel hits, pitching the nose up a couple degrees, increasing AOA and lift and causing a crow-hop. Crow hops tend to turn into PIOs, tend to turn into disasters.
Now let's rerun that scenario with spoilers 1/3 to 1/2 deployed at the moment of impact. As soon as the pilot realizes what's about to happen, he applies full spoiler, killing that increment of lift caused by the pitch up. His bird is all done flying, just rolling docilely down the runway.
Cheers,
Wes