Martin

It is not clear if you need to pass the current through PCB anyway for some reason or if you want to use PCB only for measurement purposes. If the second, why not use a "screw mounted" shunt resistor which can be attached directly to bars/structure? There are some down to 25 uOhm available. 1 % total accuracy can be quite a challenge (or expensive), but with callibration and low TCR maybe acceptable? (But note that paralleling 8 resistors, it will be almost impossible to get exactly even share of current, so you can not have easily <1% measuring only one of them ...)

Last comment :) It just occurred to me that thinking the transition into climb as part of circle is actually nice way to see it. The rate of pitch change (together with airspeed) gives radius and necessary additional lift for centrifugal force. Then look if wing at given airspeed can generate this extra lift before stalling. If yes, it will be smooth transition into climb. If not, then stall.

horizontal spin .. should be, sorry

In fact you could do something like snap roll even with common Cessna if you start really close to stall speed (then you do not need so much elevator input). But there is a real risk that it won't complete whole roll in one piece and if yes, than it won't be legally usable again without a through check as it definitively not an allowed stress on airframe.

Yep, that's what I have linked in initial post, snap roll. From level flight roughly 1.5 or 2 times stall speed (depends, but let's say) you will pull on stick to stall wings and then add rudder input to initiate roll. It is more-or-less vertical spin, but started well above 1g stall speed.

Another thing is that, at least subconsciously, people are flying based on feedback from felt acceleration. To stall wind in cruising speed, you need to pull maybe 4g or even more. Most likely you won't do this unintentionally. :)

Yes, definitively. As mentioned the authority of control surfaces decreases with airspeed too, so you have less "leverage", but normally design intention would be to have at least some authority remaining to make plane controllable. And with speed just above stallspeed, there control surfaces gain authority faster than main wing lift limit.

So as always, it depends. :)

But if there is some control authority remaining, rapid pitch-up input close to stall speed will probably lead to stall instead of climb.

OTOH with speed close to stall, there is really small reserve for wings to generate more lift. While you could have some significant elevator authority left (this really depends on particular airplane and center of gravity, there are airplanes which would fly at the edge of 1g stall speed with stick all the way back and you have no way to command further pitch-up :) ).

If you are flying above maneuvering speed limit, the vertical acceleration could actually break airplane instead of reaching a stall.

Probably, hard to make a generic statement, but with speed well above stallspeed, wings have a lot of capacity to generate vertical acceleration with increasing AoA, so it should be able to build up vertical speed quickly. Elevator will gain more available force with airspeed too, but I believe the effect will be smaller and most importantly a pilot will feel this as a large stick force and big g-force will prevent you from pulling too hard too most likely.

With an airplane with enough thrust (quite unrealistic, but well), you could even fly really big looping without much AoA. Exactly your "helicopter-like" question -- flying exactly vertically nose is pitching 90deg up, but AoA can be still small. But it applies in exactly same way for any intermediate angle as well.

Soft transition into climb means only minuscule increase of AoA (and felt acceleration), because pitch up is immediately compensated by increased climb rate.

If you command too rapid pitch up, vertical acceleration won't be enough to build up enough climb speed in time and instead AoA will increase.

If pitch change is "slow enough" (what is slow enough depends on many properties of the airplane etc.)

My point is that the excessive lift will lead to immediate acceleration upwards. So both happens simultaneously, pitching up nose and gaining vertical speed, exactly as you are saying about curved trajectory. When AoA is approaching 1g value vertical acceleration decreases, so whole system self-regulates to soft transition into 1g steady climb.

But normally you start with pitching up and increasing AoA without change in airspeed.

Actually it is possible. Just push gas to full power and keep nose attitude unchanged. :) Increased speed will cause increased lift (without need to change AoA initially), this will result in vertical acceleration until vertical component of velocity turns relative wind so that AoA decreases tovalue which gives 1g at increased airspeed.

But if you go along this curved path, it is already non-stalled transition into climb, I believe. The way to stall airplane by pulling hard is that pitch change will be much faster than speed change. Maybe you can think it as a really small loop. But I am not sure if it helps explaining what happens.

Anyway I am not sure how exactly is it related to original question. Maybe it is only a question of right terminology? You can break this curved path into small infinitesimal steps change in pitch-change in vertical speed (that's how I tried to explain it) or you can think it other way too, I suppose.

Yes, you can see it like this too. If you would want to do a loop, you try to keep excessive lift constant (plus/minus 1g changes because of change in attitude), but normally this curved trajectory is really small part of whole climb and most of the climb is straight line with 1g.

Actually, in the first approximation, for given airspeed, there is only one possible AoA (two if you count stalled region too) for steady balanced flight (straight, either horizontal or climbing/sinking, but not turn). Any different angle will result in excessive force in some direction (lift or gravity) resulting in imbalance. When the flight stabilizes again in new regime, the AoA has to be back at value for 1g-lift.

It is not a propeller what initiates climb, it is an excessive lift from main wing because of increased AoA. (the propeller is there only to prevent losing energy/speed; any glider can go from horizontal flight into the climb in exactly same way as a powered plane). And because excessive AoA means acceleration upwards, in steady climb forces needs to be in equilibrium and AoA at 1g level.

@EBV821 somewhat not somehow, of course, pardon my English. Anyway, yes, it is not purely vertical movement, but there is still non-zero vertical component and therefore relative wind has to be oriented partially from above too. If pitch with respect to ground/horizon/inertial reference does not increase further, an increase in vertical speed means lower AoA. I have tried to sketch some illustration, not sure if it helps. :)

@LorenPechtel that was my point. The Isp is not a hard limit, but energy/power per mass is. (Btw. even if you 'd scale up thrust somehow, solar panels would have orders of magnitude too low power-to-weight.)

Just build a small linear particle accelerator in space and you will a get ion drive with specific impulse to spare. Xenon ion accelerated by 50 kV (really little for particle accelerator scales) is flying faster than 10 000 km/s (Isp over 1e6). What will definitively kill the idea even hypothetically is energy, only accelerated ions would carry away orders of magnitude more than what you can produce in available mass with today technology. It is actually energy requirements which makes nuclear propulsion only one somewhat close to possible except for external propulsion and nanocraft.