Considering that 100 KIAS AT 70,000 feet is 440 Kts ground speed, I need not worry about my actual speed, right? I just have to get the speed bug at 100 KIAS the whole way up?And here's the section on climbing at high atltitude. Normal cruise for the U-2S is 0.72 Mach. This equates to an indicated airspeed of around 106 knots at 70,000 feet. The real U-2S utilizes what is known as a "cruise climb" to reach the higher altitudes. This is accomplished by setting the Mach hold at 0.72 Mach; the aircraft then controls the speed by adjusting the pitch while leaving the throttle setting unchanged. As the aircraft burns fuel, it will become lighter and will climb at approximately 100-200 fpm with the Mach hold enabled. In Flight Simulator 9, this kind of control is not possible with the usual autopilot configuration. It will be very difficult to launch a cruise from 70,000 feet. The best way to simulate the actual procedure is to begin a climb from 56,000 feet at a rate of climb of 100-200 fpm and reach cruising altitude. A normal cruising weight is around 25,000 pounds at 70,000 feet. So what would be a suggested altitude to turn the a/c over to the autopilot and Mach hold? FL180? FL260? FL700?

You need to read your instruments (steam gauge-style round ones or the PFD screen as in the video): Read the manual as to your appropriate take-off speed (or try 75 KIAS - Knots Indicated Airspeed). Set full throttle, accelerate to the proper take-off speed, and then gently rotate nose-up until 10º up is shown on your artificial horizon and wait for the VSI - Vertical Speed Indicator to show you are climbing.Once you're off the ground, retract the gear. Notice your speed will be increasing fairly dramatically, so continue firmly increasing your nose-up until 45º, monitoring you don't overspeed (reduce thrust somewhat in an emergency but promptly get back to full thrust.) Notice the trend in your airspeed (is it increasing or decreasing? How fast is it increasing or decreasing?) and adjust your climb angle (nose-up above the horizon on your artificial horizon or PFD screen.) If you are accelerating, increase your climb angle to make your climb steeper, and if you are slowing down, decrease your climb angle to make your climb shallower, all the while aiming to keep ypur airspeed constant at 100 KIAS.Note that as you climb your engine will lose thrust as the atmosphere thins and you will have to progressively lower the nose down to maintain speed. When you you can only climb at 100 FPM you will have reached your maximum altitude. Monitor your Mach speed as you climb and make sure you do not exceed your MMMO - Mach Maximum Operating Number (probably around .75M, this was a slow aircraft and the wings had little back-sweep) to avoid a high-speed stall. Not the difference between TAS -True Air Speed (or GS -Ground Speed if no wind) on your GPS vs. IAS on your PFD.On your way down, do the same thing: Cut your thrust to idle, lower your nose below the horizon and maintain 100 KIAS all the way down. Level out at 3000 ft AGL and reduce your speed further until you see 10º up on your artificial horizon, then fly exactly that speed down the approach until touch down. At 30 ft AGL cut your thrust to idle and rotate your nose up so you again are at 10º nose-up for landing.To be proficient you will have to develop a good "feel" for what your aircraft is doing so you have a smooth take-off, rotation to climb, climb and level-out at altitude. How you nail that 100 KIAS on your way up will be a good indication of your U-2 piloting skills!Cheers,- jahman.

So what would be a suggested altitude to turn the a/c over to the autopilot and Mach hold? FL180? FL260? FL700?

What is the indicated airspeed they tell you to climb at initially? I would say climb at that IAS until that airspeed and the mach speed coincide then switch over to Mach hold.

100 KIASWhat do you mean "until KIAS and Mach coincide?" You mean Coffin Corner?

What is the indicated airspeed they tell you to climb at initially? I would say climb at that IAS until that airspeed and the mach speed coincide then switch over to Mach hold.

...So what would be a suggested altitude to turn the a/c over to the autopilot and Mach hold? FL180? FL260? FL700?

After you're off the RWY, gear is raised, speed is 100 KIAS, Attitude is +45º and climb speed is +10,000 FPM. Then engage VS - Vertical Speed Hold mode on the AP - Autopilot. Make sure you dial +10.000 into the AP VS before take-off, or you will mess-up your climb profile while twiddling that knob! As IAS wnats to drop, reduce VS on the AP.Then once you reach your desired FL, engage the Mach Hold on the AT - Auto-Throttle.

What do you mean "until KIAS and Mach coincide?" You mean Coffin Corner?

Yes. Do not exceed Mmo - Mach Mac Operating Number or you will enter a high-speed stall.Cheers,- jahman.

100 KIASWhat do you mean "until KIAS and Mach coincide?" You mean Coffin Corner?

No. Coffin Corner is when stall speed and Mach buffet coincide. What I am talking about is when you climb at a given IAS. As your altitude increases temperature usually decreases and then your mach speed rises at the same time. What happens is that sometimes you can climb at a recommended airspeed until IAS and mach are the same. As you climb higher you will need to reduce your IAS to hold a given mach speed.Try this in the sim. Take off and climb while holding a set airspeed say 200 knots. As you climb you will see that your mach number rises as your IAS stays the same. Eventually if possible these two numbers will meet and then you will slow your IAS down to have the same mach number.

Do not exceed Mmo - Mach Mac Operating Number or you will enter a high-speed stall.- jahman.

Why should a plane enter an 'high-speed' stall (I assume you mean accelerated stall) just because you are flying faster than Mmo ???Where's the angle of attack related part ?

Why should a plane enter an 'high-speed' stall (I assume you mean accelerated stall) just because you are flying faster than Mmo ???Where's the angle of attack related part ?

Accelerated stall is entered in higher G situations and isn't about speed.

Accelerated stall is entered in higher G situations and isn't about speed.

erm, that's what I wrote....looking foward to jahmans explanation...

erm, that's what I wrote....looking foward to jahmans explanation...

No what you wrote was purely about speed.

Why should a plane enter an 'high-speed' stall ... just because you are flying faster than Mmo ???

Where did it say anything about pulling G's?

Why should a plane enter an 'high-speed' stall (I assume you mean accelerated stall) just because you are flying faster than Mmo ???Where's the angle of attack related part ?

Instead of just condescendingly attacking other people around here, why not elaborate or add to an answer that doesn't meet your standards? How hard would it be to reply to jahman by saying that exceeding Mmo does not actually cause an accelerated stall, but a phenomena called Mach buffet which is entered into, appears to be, and recovered from, similarly to an accelerated stall? At high speed, an increase in the angle of attack accelerates the airflow above the wing, exacerbating the high speed shock wave, and causing a buffet similar to a high speed stall buffet. To recover from the Mach buffet, reduce angle of attack and/or airspeed.

Instead of just condescendingly attacking other people around here, why not elaborate or add to an answer that doesn't meet your standards?

??? I don't know why you think that it is ok to tell people looking for help wrong things. That's neither helpful nor informative.It would be better to write nothing instead of providing wrong info. Neither do I see an 'attack' nor does this have anything to do with someones 'standards'

No what you wrote was purely about speed.Where did it say anything about pulling G's?

Exactly. That's what I wrote. Again, just exceeding Mmo doesn't lead to a stall....Suggest to really read what I wrote before replying.

Um, ah, in a high-speed stall a sonic shock-wave forms on the top surface of the wing as the air is accelerated beyond the free streaming velocity (TAS) as part of the airfoil lift-generating process. (Recall the purpose of an airfoil is to accelerate air to reduce its pressure -Bernoulli Effect- and so produce lift). Mmo is just the M number at which the shock wave has enough energy to detach the airflow. Non-swept wings can be affected as low as .5M (e.g. the venerable B-377/C-97), whle modern trans-sonic airfoils (Gulfstream G650) are shaped to delay shockwave formation, pushing the shock wave somewhat towards the trailing edge where less lift is generated anyway and stretching the area of onset of the shockwave to dull the onset and reduce the energy available to detach the airflow from the wing. The interesting thing is Mmo for these advanced airfoils is .925M which means airflow above certain areas can reach 1.05M or more.Thing is these shock waves detach the airflow from the upper surface of the wing thus causing loss of lift, hence the name "high-speed stall". Similarly, an excessive angle of attack (typically 14º, or 22º with slats) will also cause airflow to detach from the wing and cause loss of lift at *any* airspeed, but usually occur at lower speeds, so they are alled low-speed stalls.An accelerated stall technically does not exist: What you have is a situation where wing loading exceeds available lift, thus the aircraft moves "down" (if flying upright with wings level) and the air free stream now has a corresponding upwards component, thus increasing the wing's angle of attack (much as wind direction changes in a sailboat as you speed up) and causes a low-speed stall. Note that an accelerated stall can happen at any load factor, including less than 1G. If the load factor is 1G, then the accelerated stall is the regular low-speed stall. How can a wing stall at less than 1G? Just fly slow enough.High-Speed Stall DetourThe problem with wings designed for high TAS is that they are swept-back to increase Mmo, while for aerodynamic and mechanical efficieny (lower drag and weight, respectively) the wing is a *lot* thicker at the root than at center-span.Now if you remember the area rule: When reaching the trans-sonic flight regime at .75M and above, air starts to move so fast along the aircraft wing and fuselage (in reality it's the other way around!) that it doesn't have time to move out of the way of the aircraft (body plus wing cross-section), hence the shockwave and therefore the Area Rule: To reduce the "Wave Effect", reduce fuselage cross-section as wing cross-section thickens so that the sum of both remains constant and as small as possible. (The wave effect is pernicious because it takes energy away from the aircraft in the form of a pressure wave and thus increases drag and fuel burn, decreasing range.)But do you see airliners with coke bottle fuselages? No. So when a jetliner exceeds Mmo, the shockwave forms largest spanwise near the fuselage stalling the wing there first, because that's where the wing generates the most lift. Thus the wing's overall center of lift moves rearward behind the CG, causing the nose to move downward, thus increasing TAS. To make matters worse, most airfoils have a sub-sonic center of lift at 25% of chord, but the center of lift can move back to as much as 50% of chord for supersonic flight.Now couple the two effects together and you will easily exceed elevator authority (accelerated elevator stall), you will not be able to recover and the aircraft will be lost. This is exactly what happened with some russian airliner when a pilot let his kid man the controls and the kid unwittingly pushed the yoke far forward. "Standard Recovery" (quite the misnomer!) is to dirty-up the aircraft aerodynamically as much as possible (flaps, slats, spoilers (only of the non-lift-dumping kind) and gear) to keep speed from building up. Praying helps too (alas no survivors are available to confirm).Incidentally, ever wonder why the bottom of the airliner's fuselage is so "bulbous" and the under-wing flap tracks are so thick (especially in the B-747)? Well, they are used to increase Mmo by delaying shock-wave formation on the *top* of the wing! How can that be? Well, that's the wave effect so frontal cross-section *beneath* the wing is purposedly increased to increase pressure above the wing (counterintuitive!) just enough to delay shock-wave formation. A master case-in-point are the two below-wing fuel tanks of the U-2: Drop those mid-flight near Mmo and high-speed stall for you (because Mmo will be reduced)!Cheers,- jahman.

Well written and you brought up a good point about anti-shock bodies on the wings. I loved the ones the Convair 990 used.http://en.wikipedia.org/wiki/File:Antishock_Bodies_Visualization.jpgThis is a good example of showing where the separation occurs without and with anti-shock bodies.

Well written and you brought up a good point about anti-shock bodies on the wings. I loved the ones the Convair 990 used.http://en.wikipedia.org/wiki/File:Antishock_Bodies_Visualization.jpgThis is a good example of showing where the separation occurs without and with anti-shock bodies.

Thanks from the compliment, Chris!That's a great picture! Wing oiling is a great way to visualize airflow separation.Austral Líneas Aéreas Flight 2553 high-speed stall accident (frozen pitot in thunderstorm), and what the aircraft looked like after applying "standard recovery procedures" (actual photo, not me trying to be funny):Cheers,- jahman.

I don't think that the DC-9 crash was due to flow separation at high mach number.If one looses a complete slat assembly at very high speed it's most probably the resulting rolling moment that will lead to the extreme nose down attitude.In a DC-9 / MD80 it's not possible above approx M0.95 to achieve any intentional rolling motion even with full aileron deflection, so in this case it would not have been possible to roll the plane upright again.The highspeed stall you mention doesn't occur at Mmo. At that speed you might get a slightly turbulent boundary layer aft of the just forming shockwave.At Mmo you need a higher than normal AoA / G load to achive flow separation, that's why I mentioned the 'missing' AoA and hence 'accelerated' stall. Mdf is the lowest speed where serious flow separation occurs but that's almost impossible to reach at level flight for subsonic planes due to the extreme drag rise.'Highspeed stall' sounds IMHO a bit misleading as the flow separation at straight and level flight doesn't occur as rapidly and complete as during a 'normal' stall.