Area51 Sim U-2S Altitude problem?

R

razor61

Guest
Although a superb looking aircraft for FSX i am having serious problems getting any higher than 60,000ft with this aircraft.

U-2S Dragons transit at FL660 (66,000ft) and conduct missions between 70,000-80,000ft when in theatre.
How would i tweak the aircraft to enable it to fly higher than 60,000ft without stalling?
As soon as it goes above 55,000ft it becomes extremely difficult to control and even climb.

I know that from real footage of inside the U-2S the pilot shows that when at 70,000ft the U-2S Indicated Airspeed is around 120kts which in true airspeed is a lot higher and so the pilots do not go by the IAS when that high as its not the true ground speed. But it seems in FSX the aircraft seems to think that 120KIAS is Ground Speed and so the U2 is close to stalling.
 
I don't know anything about this model, and maybe even less about the real U-2, but I did read someplace that at these altitudes, the U-2 was in a tiny “window” of airspeed, of about three knots, between stalling, and max speed. So in that sense, your description is consistent with what I've read about that plane. Don't know what special techniques were used at high altitudes, but stall speed is stall speed, in KIAS terms, no matter how high you are. For a given ground speed (assuming no wind), the indicated airspeed will be slower the higher you go, which is why the U-2's (and all planes, for that matter) max speed gets closer and closer to it's stall speed as it gets higher.
 
Hi
Thanks for the reply.
However as i stated, the KIAS is around 120kts for the U2 at 70,000ft but this is not the true airspeed, its really cruising at around 0.65 to 0.70 mach which is not anywhere near the stall speed.
The KIAS is showing such a small speed number due to the air pressure being so low and so the real ground speed (TAS) is much higher, so it would not stall like it does in the simulator.

When James May went up in a two seat U2 a few years ago from Beale AFB he commented that seeing 120kts on the gauge was worrying but the pilot reassured him that the actual air speed they were travelling at was much higher (the mach number was shown to be normal cruise speed).

It seems though the simulator is acting on the KIAS near to 120kts and not enabling the U2 to climb much higher than 60,000ft without stalling when in fact the real U2 can still climb without a problem and cruise at a reasonable mach number.

It seems to be something that most of the aircraft models have trouble with, apart from the SR-71 from Alphasim but even then with that model you need afterburner on to achieve the Mach 3 cruise at 80,000ft which is again unrealistic.

There must be some way of tweaking the .air file or .cfg to achieve the real cruise characteristics of the U2S at altitudes above 70,000ft or so but its knowing what strings to tweak.
 
I'm not saying there isn't a problem with this particular U-2 model. I don't have it, so I can't say one way or another.

But...

If the stall speed for the U-2 is 120 knots, that is 120 knots indicated. If you're traveling at Mach 0.7 at 60,000 feet, and, due to the thin air, your airspeed indicator reads 119 knots, your plane will stall, even though you're traveling across the ground at 400 knots. Stall occurs at a particular indicated airspeed, not any particular true airspeed. It is certainly possible to stall at 0.7 mach, if your up high enough...
 
The U2 does operate in a very narrow window, sometimes called Coffin Corner. The lower limit is of course the stall and the upper the mach limit. 120 knots would indeed be close to the stall value, and for a straight winged airplane, near the mach limit. Addtionally the plane really needs to be flown at or near the L/D max and certainly at the thrust/drag max for that altitude. The real plane must be flown on autopilot as hand flying would not be able to maintain the required precision at high altitude.

It might be helpful to asjust the 430 and 433 tables in thr.air file. It may be the mach drag onset needs to revised a little bit. A utility such as AFSD will show the mach drag values you are generating in it's aerodynamics tab.

Cheers: T
 
I can confirm what Wilycoyote said. The update causes the issue. I've swapped to the old "aircraft" and "air" files and can easily exceed 70K feet.

Hopefully, Area51 will update, as the older files are a little over-powered at low altitudes if anything. Maybe they could see fit to add a "conventional" U-2S w/o the sat-link too!

Bill
 
U-2S air file

Hello,

I recently purchased the Area 51 dragon lady and have also experienced the same alt limitations and near stall speed issue. I purchased it from the Area 51 home page link to buy it.

I can't remember if the update was automatically installed or not, but FL80 is not reachable with my version.

Does anyone have the original air file, and if so is it possible to send it to me, with breaking any payware violations?

Thanks, Doug
 
Hi folks,

I’ve just purchased a copy of the A51 U-2 from PC Aviator. I’m also struggling with getting above 55-60k.

Any tips on how to modify the .air file? It seems A51 are a distant thing in the past now.

I’m actually writing an article on the U-2 for a UK aviation magazine and have recently met the 99th ERS and had a few rides in the chase cars. I decided to buy the A51 model to get some insight of what it feels like to fly!
 
razor61 said:
Hi
Thanks for the reply.
It seems to be something that most of the aircraft models have trouble with, apart from the SR-71 from Alphasim but even then with that model you need afterburner on to achieve the Mach 3 cruise at 80,000ft which is again unrealistic.
Click to expand...

There's nothing unrealistic about that (I know its 10 years ago, but...) SR-71 would light the burners at 30,000 ft do a descend and accelerate manoeuvre known as the dipsy doodle and then power climb at 430 KEAS to 70-80,000 ft in full afterburner and that's where it would stay, cruising in full afterburner at Mach 3 until it's time to come down again to refuel/land.

I don't own the U-2, but did it come with a manual that guides you in how to climb and cruise? I only have a U-2C flight manual, and that aircraft was smaller and lighter than the U-2S.
 
centuryseries said:
That manual is for very early U-2 with the smaller wing and overall size, when compared to the modernised, re-engined 30% larger U-2S. You won't find a U-2S manual online, or if you do, you'll get a knock on the door!!
Click to expand...


It would be nice, if the CIA would knock on my door - to hand over my personal copy of the actual U-2 manual :biggrin-new:.
 
captdoug said:
Hello,

I recently purchased the Area 51 dragon lady and have also experienced the same alt limitations and near stall speed issue. I purchased it from the Area 51 home page link to buy it.

I can't remember if the update was automatically installed or not, but FL80 is not reachable with my version.

Does anyone have the original air file, and if so is it possible to send it to me, with breaking any payware violations?

Thanks, Doug
Click to expand...

Hello Doug,

I can definitely help you with this AIR file issue.
I switched from the default one to a modified one (don’t know if that’s the updated one or not) a few year ago, and reaching the climb cruise altitude has been much much easier since then. Maybe even too easy.
I’ll check the files in the next few days.


I toi would love to read the current U-2S flight manual, but as long as the Dragonlady flies for the USAF, I doubt it is declassified. And all fancy systems and their operation manuals will remain secret for a loooooong time I am afraid.
 
Hello Sean,

I don't own P3D in neither 32bit or 64bit version, so I can not vouch that it works. BUT since all the gauges are simple XML ones, I am pretty confident the U-2S should work fine in P3Dv4.
Check your PM.
 
flyby94 : Your Inbox is full!

So here is the link to the .air file :

https://www.dropbox.com/s/3f4apjv4dm..._Lady.air?dl=0

To install it :
0) Browse to your FSX\SimObjects\Airplanes\U-2S folder and rename the U-2.air file to U-2_OLD.air
1) drop the downloaded file into your FSX\SimObjects\Airplanes\U-2S folder
2) Rename the Area51_U-2_Dragon_Lady.air file into U-2.air
You are done.

Happy flights!
 
Chase Car Radio Calls

Hi folks,After feeling that something was missing from the U-2 experience, I set out to add chase car (mobile) radio call-outs, through editing a GPWS add-on. It took me a couple of hours over some beer and wine one weekend, but it's made the Dragon Lady much easier, and more realistic to land! You can see it at the end of this video here: https://youtu.be/k-TPX_L7a7U Towline
 
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