View Full Version : U-2S -max altitude

25th Nov 2008, 10:44
Many reports and specifications from variable sources claims t that the U-2S (with new F118 engine) could reach 95.000 ft. I don`t understand, because the same sources give about 70 kts stall speed at sea level and max speed about .76Mach at altitude.
At 92.000 ft 71 kias will be .80 Mach,
at 95.000 ft 70 or 75 kias will be much more than .80 Ma, speed that I believe must destroy fragile wings.
what you think?

Agaricus bisporus
25th Nov 2008, 11:03
I believe you will ask long and fruitlessly. Probably the figures are not entirely consistent or accurate.

Does that really surprise you?

25th Nov 2008, 11:05
The DFS (German Air Traffic Service) in its listing of military aircraft performance figures has the U-2R listed with a service ceiling of 90,000 feet. Its mention of the S version is limited to a comment: "re-engined"

25th Nov 2008, 11:32
quote>>The DFS (German Air Traffic Service) in its listing

heh-can civil ATC to see any aircraft at this altitude? I think for these guys 70000 or 90000 ft is no big different

at youtube.com is video from cockpit and plane is climbing thru FL600 at 135 kias, and red line is 140 kias.

25th Nov 2008, 13:11
The DFS publishes a guide for its staff of all types that may operate in its airspace with as many performance figures as are known and verifiable.

Why wouldn't they be able to radar identify a target at FL 900?

25th Nov 2008, 17:03
The difficulty with radar is that the equipment has what is known as a radar lobe - this is the coverage of the radar signal and can be thought of as a donut shape originating from the radar head. Not all radar lobes reach 90,000ft.

25th Nov 2008, 17:27
I'm well aware of the way radar can be, and is, set up and also of the linkage between the civil and military controllers in Germany.

As far as it goes, I was trying to answer your query about an aircraft which has most of its performance data witheld with the most accurate information from a dependable source I could find.

28th Nov 2008, 12:43
About 15 years ago almost daily I observed traffic routing south - north over the London area indicating FL660 on SSR (there was no primary return) and which I assumed at the time were TR1s/U2Rs bound for Alconbury or Mildenhall.
I read somewhere that the (early) version used by Gary Powers operated at about this level, but you only had about a 4kt boundary between stall speed and mach buffet when this high, and he was brought down not by a direct hit, but by a missile exploding near his aircraft causing it to exceed these parameters - not sure whether it said he stalled or whether it just broke up due to exceeding its mach limit.

30th Nov 2008, 18:02
After a long mission, fuel load and GW are down substantially, as is Vs; Thus the "coffin corner" has moved up several notches. I doubt he can reach 95K early in a mission.

1st Dec 2008, 21:10
I was chatting to a U2 pilot a few weeks ago, he only talked about cruising at 70,000 although i didn't ask him if it would go higher.

18th Jun 2009, 12:51
Yeah, I think U-2S pilots very rare go higher than 75.000 -80.000 ft. There is no need I believe.
On Barry Schiff web page is pilot`s report from training U-2ST flight and his pilot said thed above 70.000 ft climb is only result of decrease of weight and it is very slow drift.

ok, I got something: http://www.aerospaceweb.org/question/atmosphere/mach1/mach1-table-earth-e.gif
so, if above 70.000 ft speed of sound again INCREASE with altitude, the flight envelope for plane is open wier a bit and now I thing that 95.000 ft or even 98.000 is quite possible