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If Concorde was travelling at mach 2 and FL 600 then pulled up, it would enter a trajectory that went above its normal flight altitude before diving back down. I assume that it couldn't pull up to full control surface deflection in those conditions without the wings folding, so without damaging anything, how how high could Concorde go using this method? Is there a way to calculate/estimate this, or is it only provable by testing? I've searched google for answers but I can't find anything on this subject.

(An unrelated question that I couldn't find an answer to: what was the structural G limit of Concorde at cruising speed)

GdD
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ThatCoolCoder
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    Testing was done 4 this sort of thing in the 50s by Chuck Yeager using an F-104 with a booster rocket under the tail. It would do ballistic arcs from its service ceiling up to about 100000 ft+, helped along by the rocket. It needed nose attitude thrusters to control pitch attitude above about 90000 ft because the flight controls had insufficient dynamic pressure to work normally. In The Right Stuff, the bit with him spinning out and ejecting near the end of the movie was about that last one of those tests where it almost killed him when it stalled and spun on "reentry" because the att was off. – John K Aug 06 '20 at 12:10
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    The part about structural limit can form an entire question by itself and could be asked separately. – Manu H Aug 06 '20 at 14:32
  • you may be interested by the part about energy convertion of how it flies. You are looking for zoom climb and transformation of kinetic energy to potential energy – Manu H Aug 06 '20 at 14:36

3 Answers3

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There are a couple of ways to look at this question. The easiest is using first principles.

Therefore imagine that Concorde (flying at Mach 2 at FL 600) can, suddenly and without energy loss, pull up, such that it flies for example 10 degrees upwards. Also we assume the following:

  • The engine flames out immediately, therefore no engine thrust
  • We neglect air resistance

How much higher would it go? The formula to calculate this is surprisingly simple: $$ \Delta x = 1/2 \cdot \frac{(V_I \cdot sin(\gamma))^2}{g} $$ with $V_I$ being the inital velocity (590 m/s which is Mach 2), $\gamma$ being the climb angle and $g$ being the gravity of $9.81 \frac{m}{s^2}$.

I have calculated it for a couple of angles:

  • $\gamma = 10°$: 535m
  • $\gamma = 30°$: 4436m
  • $\gamma = 45°$: 8871m
  • $\gamma = 60°$: 13307m
  • $\gamma = 90°$: 17742m

That gives us a first guess, but the question remains: Could it pull up at this high altitude? The answer is: Yes. Consider the formula to compute the dynamic pressure: $$ q = 1/2 \cdot \rho \cdot V^2 $$ Concorde takes off at around $113 \frac{m}{s}$ at an air density of around $1.225 \frac{kg}{m^3}$. The air density at FL 600 is around 1/10th of the air density at sea level. However the cruising speed is roughly 5.2 times faster, which yields 2.7 times higher dynamic pressure at that altitude. Thus, the rudders definitely work at that altitude.

The real limiting factor here is the structural limits when you try to pull up at Mach 2. For example if you try to pull up your aircraft at Mach 2 with a constant acceleration of 1 G, you will follow an circle with a radius of ~50km. Even with 3 G acceleration, you will still follow an (upward) circle with a radius of roughly 16km. My guess is that Concord can safely handle around 3 G (for example, to be able to handle gusts at altitude). Additionally, you will lose a lot of your energy while pulling up, due to additional drag (remember, because of the increase angle of attack, the aircraft has more drag) and of course you are getting slower as you trade velocity versus height. Thus at some point you will not be able to pull up any further because you lost too much speed. I tried to estimate how much higher you would have to fly in order to go down to stall speed¹, and my result is 11.2 km of additional height. That would mean that you could reach a $~70°$ climb. However I neglected air-drag etc. and the fact that you will definitely not pull 3Gs at stall speed.

To get a definite answer, one would have to perform some computer simulations. Perhaps one of the popular flight simulations can help. But I would guesstimate, that at FL 600 going at Mach 2, you can probably (safely) pull the airplane up into a climb of around $\gamma = 30°$, which would yield around ~4.4km of additional height.

P.S: However the assumption that the engine will flame out at higher altitudes is probably true. My guess would be that the engine was designed such that it can not substantially exceed FL 600. But that is speculation.

¹ I simply assumed that the stall speed is at the same dynamic pressure as at take-off condition. This yields a stall speed of $357 \frac{m}{s}$.

Steve Pemberton
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U_flow
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    In a 3g pull-p the induced drag during the maneuver will be about 9 times higher than in straight flight. Even with engines running, the Concorde will drop to subsonic speed quickly. Also, as far as I remember, the g limit in cruise was lower than 3g. – Peter Kämpf Aug 06 '20 at 20:22
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    Ah cool, how did you compute that? Perhaps We can calculate a more accurate answer? – U_flow Aug 06 '20 at 21:58
  • Well, you could take into account that $g=9.75$ at $17742 m$ :-) – Déjà vu Aug 07 '20 at 18:47
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Let's have a look.

  • If its normal supercruise was M 2.04 at 60,000'

  • And it had excess power available (it did-dry and in addition had reheat available)

  • And its aerodynamic capability was quite a bit higher than its normal service Mach number (it was – Concorde 101 flew at M 2.23 or 1,450mph)

One could easily posit a test scenario in which a gentle climb was initiated just by selecting an altitude on the autopilot.

The autothrottles would do the rest in terms of power. Climbing at a steady Mach 2.0, Concorde could likely gain a significant amount of altitude. Perhaps 5-10,000' very quickly.

But before we go any further, we need to clear up some definitions to address some of the other comments.

The term 'ceiling' or ‘service ceiling’ in a normal aircraft refers to: The density altitude at which flying in a clean configuration, at the best rate of climb airspeed for that altitude and with all engines operating and producing maximum continuous power, will produce a given rate of climb. A typical value might be 100 ft/min (0.51 m/s) climb, or on the order of 500 ft/min (2.5 m/s) climb for jet aircraft.

Normal airliners don't operate at their service ceiling, as this requires max continuous power and that is just a no-no for fuel burn. Also, you can get very dead, as the Pinnacle Airways CRJ-200 crew did by playing at the aircraft's service ceiling. You are at the edge of the aircraft's aerodynamic performance.

The service ceiling of 60,000’ commonly listed for Concorde, does not meet the normal definition as 60,000’ was its normal planned cruise altitude.

It is more than likely that its actual service ceiling 'hard limit' was quite a bit higher than 60,000' as Concorde cruised at 60,000' every day for 27 years.

I know, I flew on her in 1999 JFK-LHR.

The 60,000' certification service limit was (I believe) derived from a window loss scenario. If one window was lost the ECS could maintain cabin pressure until the aircraft descended to 10,000'.

Remember at 60,000' the TUC is a couple of seconds, and you require positive pressure breathing.

As to speed, the service speed limit for Concorde was a heat limited-127C. On my flight we reached 1,350mph and the nose probe read 126C (Yes, I spent about half an hour in the flight deck talking shop with the pilots and the very busy Flight Engineer) As mentioned, in testing Concorde ran out past M 2.23 but for service life reasons, its service limit was 2.04.

With the available excess power, a climb could be made while maintaining M 2.0-2.04. No sudden pull up required. At that speed, your climb rate at even a shallow angle is going to be impressive.

completeaerogeek
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  • Might be better worded as, "Concorde routinely cruised at 60,000'" which is probably what you meant. I have read various accounts that it cruised between 55,000 and 60,000, for example in this answer. Not doubting that you were on a flight that cruised at 60,000, but I wonder what percentage of the time that occurred and what were the reasons that determined the altitude, although presumably it was for many of the same reasons as subsonic aircraft such as winds aloft. – Steve Pemberton Feb 03 '24 at 21:24
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At 60,0000’, I would expect the Concorde might be cruising at the edge of its performance limit.

If you try a "zoom climb" with any aircraft at the edge of its performance limit, the aircraft might be dangerously close to the stall speed.

Toby Speight
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Mike Sowsun
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    At 60,000 ft in standard atmosphere, Mach 2 is about 1147 KTAS and about 353 KIAS, which is lower than one might think, but not near stall speed yet. In fact, Concorde first slowed down at 60,000 ft (I forgot to what speed exactly) before actually starting to descent. – Bianfable Aug 06 '20 at 13:01
  • To really answer the question, you should provide figures. Otherwise, I fear this is more a comment than an answer. E.g. you can add energy consideration (how much kinetic energy when cruising at 60000ft, and therefore how much height gained when transforming the kinetic energy to potential energy while slowing down to stall speed neglecting losses due to drag and gains due to thrust, therefore giving only a first approximation) – Manu H Aug 06 '20 at 14:31
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    One would have to look at thrust available at 60,000 feet. At supersonic speeds, any maneuvering may produce huge amounts of drag, – Robert DiGiovanni Aug 06 '20 at 15:01
  • This is called Coffin Corner, and doesn't sound very fun https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics) – Stuart Buckingham Aug 06 '20 at 17:51
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    @StuartBuckingham "Coffin corner" does not apply to supersonic aircraft. There are analogous limitations, but they aren't the same. – pericynthion Aug 07 '20 at 01:03
  • @pericynthion good point! I guess there is no critical Mach# when you're supersonic. What is the analogous "line" that forms the corner? Is it just available thrust? – Stuart Buckingham Aug 07 '20 at 13:45
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    Typically engine temperature limits – pericynthion Aug 07 '20 at 22:44