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I admire anyone who flies the U-2. As the article says, it is extremely easy to get yourself killed. The flight envelope of the U-2 was so narrow that the diffe
by areoform 6y ago
I admire anyone who flies the U-2. As the article says, it is extremely easy to get yourself killed. The flight envelope of the U-2 was so narrow that the difference between flow separation from the wing (called a buffeting) and stalling is around 20 to 30 knots. It is, as far as I know, the place from where the term "Coffin Corner" came.
https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)#/media/File:CoffinCornerU2.png https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)#/...
From NASA's book on the U-2,
> The U-2 has always been a difficult airplane to fly, challenging even the best pilots. Lightweight construction and long, thin wings give it terrific soaring ability but also make it hard to land. As the airplane approaches the ground, it floats on a cushion of air—known as ground effect—that causes the U-2 to remain airborne even at idle. The pilot almost has to force it down using spoilers to extinguish any remaining lift. A safe touchdown is further complicated by the unusual landing gear configuration. Near or on the ground, the U-2 appears to be a clumsy beast. The mysterious Dragon Lady seems at ease only when soaring to altitude or cruising through the stratosphere. Even there, danger lurks within the thin margin between Mach buffet and stall speed, the dreaded “coffin corner” of the flight envelope. Technological improvements have eased such problems as high-altitude engine flameouts and balky autopilots, but only a select few can hope to admire Earth’s curvature from more than 12 miles above the surface in what has been dubbed the Near-Space Plane.
- https://www.nasa.gov/sites/default/files/atoms/files/unlimited-horizons.pdf https://www.nasa.gov/sites/default/files/atoms/files/unlimit...
It is an extreme craft made for an extreme time.
- chiph 6y agoThe AF uses muscle cars to chase it down the runway as it lands to give the pilot feedback on their height above the concrete. They have to stall it from 2 feet up (61cm) to have a successful landing. If they do it from 4 feet up (1.2m), they'll probably damage something. They used to use Pontiac GTOs (aka Holdens), then switched to Camaros. Not sure what they're using now. https://www.youtube.com/watch?v=BIrZCymyjNY https://www.youtube.com/watch?v=BIrZCymyjNY
- garmaine 6y agoSome airman has the most awesome job ever.
- whoisthemachine 6y agoElectric vehicles would be perfect for this job.
- numpad0 6y agoThey tested Tesla in 2017 and Camaro don’t seem replaced. Perhaps those were too slow at high speeds.
- sargun 6y agoOne of the problem with Tesla’s is they cannot have long periods of sustained acceleration due to the way battery cooling works. They could probably rig up something fancy, but at least none of the models right now do this easily.
- numpad0 6y agoBoth the cooling and how electric motor works. They lose out power after 60mph or 1/4-mile distance whichever comes first.
- gambiting 6y agoThe Porsche Taycan has been specifically engineered to do that sort of thing over and over.The issue there is that I really don't see a reason to get a taycan over some american muscle, a 500hp mustang is like 1/3rd of the price of a base spec Taycan and will do the exact same job. It's not like army bases are short on fuel either.
- mlindner 6y agoThis is largely a myth and was only true of early Tesla vehicles. Also you're not going "long periods of sustained acceleration" here. The real issue would be Tesla's slow acceleration at high speeds. It has a very very good 0-60 mph, but it's 0-100 mph is more average.
- tolien 6y agoDifficult to get it back on the ground without killing yourself too - to the point that the backup pilot drives behind at ~140mph, calling out helpful information [1]. Saw a U-2 at an airshow and somehow I expected more. It had really badly damaged paint and just looked like some neglected museum exhibit that had been left outside too long. 1: https://jalopnik.com/the-140-mph-chase-cars-of-the-u-s-air-force-5537629 https://jalopnik.com/the-140-mph-chase-cars-of-the-u-s-air-f...
- meowster 6y agoI've seen a U-2 up-close in-person (it was actually one of NASA's versions). It looked pretty decent. It's pretty basic and bare-bones though: every pound saved off of it equals one foot higher that it can climb.
- blackrock 6y agoThey should get a lighter pilot.
- cornellwright 6y agoI saw a U-2 at an airshow (California Capitol Airshow at Mather) and it also looked beat up. I asked about it and they said that it's a working airplane, not some show piece. Basically it just had a lot of hours on it since it was last repainted.
- TigeriusKirk 6y agoThe trainer versions go in and out of Mather fairly often. I assume they're based at Beale AFB and just use Mather for short training hops.
- CalChris 6y agoMather AFB has been closed since 1993.
- 6y ago
- nyolfen 6y agomy grandfather flew one over southeast asia in the 50s, and later was in charge of a team that flew u-2's and a-12's (cia version of sr-71) over china. i transcribed a letter he wrote about it, mostly regarding the mechanical experience of piloting: https://hyperstition.al/u2-james-black/ https://hyperstition.al/u2-james-black/ he actually mentions a bit about the difficulty of landing: > The most difficult part of flying the U-2 was to make a good landing. It was a tail-dragger and in order to make a decent landing, you had to come across the threshold at three to five feet and ten knots above the stall speed. And the threshold speed was based on the amount of fuel on board. The aircraft attitude at the threshold had the tail higher than when parked. The residual (idle) RPM was 65% and during the check-outs, only 15% of flaps were used. The trick was to fly down the runway, holding the main wheel one-to-three feet off the runway, while the airspeed dissipated and the attitude of the aircraft rotated from that slightly-tail-high to the parked attitude, without letting the main gear touch the runway. For if the main gear touched too early, you got a bounce and that was a go-around. The same thing is true in a J-3 (40 HP) cub. In other words, you do not make “wheels” landings – placing the main gear on the ground first. It is said, that you can never recover from a bounce. For you will always be 180 degrees out of synchronization. Years later, as a reconnaissance staff officer at the 15th AF Headquarters, March AFB, Calif., I worked for a lieutenant colonel who had been in the RB-47 program at Farber AFB, Kansas for many years and the RB-47 was also a “tail-dragger” and the same was true about it and the bounce. (But it didn’t have a high-aspect wing, such as used on gliders, and the -47 had six engines, so when all six were in idle it settled down very smoothly.)
- leeoniya 6y agoyou might enjoy this story (many pages): https://www.otherhand.org/home-page/area-51-and-other-strange-places/bluefire-main/bluefire/the-hunt-for-928/ https://www.otherhand.org/home-page/area-51-and-other-strang... the whole site is fantastic, check out his other adventures.
- nyolfen 6y agoindeed, this is amazing
- 6y ago
- iambateman 6y agoQuestion on the stall issue: if a pilot starts to stall, wouldn’t they simply maneuver to get the nose down until they get enough speed to break out of the stall?
- upofadown 6y agoIt might be impossible to recover from the resulting dive without exceeding maximum speed in this particular case.
- sandworm101 6y agoCoffin corner is the speed between stall speed and overspeed, some number close to mach 1 that the airframe cannot handle. A stall-induced dive at that altitude risks hitting a speed that will damage the wings. The U2 is essentially a fighter jet with glider wings: two things that dont want to play well together. It is a frankenstien's monster of an aircraft.
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- t0mas88 6y agoCoffin corner isn't just a thing at 70,000ft in a U2, it applies to regular airliners at much lower altitudes as well. When heavy the maximum altitude for a normal passenger plane can be several thousand feet below it's certified maximum service ceiling. What helps is that due to procedures nobody flies manually at such altitudes. So it's up to the autopilot to maintain a specific airspeed. A similar effect exists at very heavy weight on takeoff, the gap between the stall speed and the maximum speed for the flaps can be as little as 20kt in a fully loaded 777. That requires good concentration and constant monitoring in the climb to not get a stall warning or a flap overspeed. This part is often flown manually.
- geokon 6y agoFrom the article the maximum speed seems to be limited by structural constraints. But surely a loaded 777 at lift off isn't on the verge of disintegrating bc it's going to fast. Maybe it's a different kind of speed limitation?
- cm2187 6y agoIsn’t Keeping the correct speed a good fit for an autopilot? Plus I would imagine there would be less turbulences and surprises at this altitude.
- mlindner 6y agoModern autopilots yes, old autopilots weren't nearly as good.