Can a plane still climb even if it has exceeded the critical AoA?

Question

According to this answer here, an airplane requires less lift for a climb than horizontal flight because the thrust of the engines will point up.

Now if the wing was in a stall condition, could the engine's thrust just 'power out' the stall, so that the airplane could climb or at least maintain level flight (assuming max thrust is applied)? In this case, the engine's thrust is supporting the entire weight of the aircraft. Is this possible? Can this be the solution to low altitude stall recovery?

EDIT:Could this also work on deep stalls?

Answer 1

Yes, it regularly done by aerobatics airplanes.

Also at 2010 Zhuhai Airshow a Chengdu J-10 demonstrated a 160kph low speed level flight. The weight of the aircraft is indeed supported by the engine. As the wing stalls deeper, the pilot turned on the afterburner to compensate.

With thrust vectoring this is even easier and more gracefully executed as shown by Su-57 at MAKS 2021

Can this be the solution to low altitude stall recovery?

Not really.

The thrust to weight ratio of the airplane in question isn't likely to be high enough. For the few jet fighters whose TWR is marginally greater than 1, you would need almost all of the thrust to be able to support the aircraft, meaning your pitch angle has to be almost vertical. Remember the elevator would also stall soon after (or soon before) the wing stalls, with reduced pitch authority I doubt you could pitch up so high and quickly enough.

Moreover, due to the very high pitch angle, by entering this maneuver you lead the aircraft into a even deeper stall, i.e. all your control surfaces are likely to stall as well, then the aircraft could become unstable and uncontrollable, which makes it very difficult to exit this maneuver gracefully. In the absence of thrust vectoring, I don't think any pilot would consider this maneuver as an improvement to the existing stall.

Finally, the reason why you run into low attitude stall is very often due to malfunctioning instrument, compromised pitch authority, or mishandling by the pilot, which are all the opposite of what's necessary for a safe execution of this maneuver. The feasibility of this maneuver is in doubt.

Answer 2

By definition, an aircraft that exceeds its critical angle of attack is stalled (i.e., the wings cannot generate enough lift to overcome weight). A stall can occur in any attitude or at any airspeed -- it just needs to exceed critical AoA. Examples of this are pilots trying to hold altitude or climb in steep banks, or doing a sharp pullup from a high speed pass down a runway.

An airplane will not recover from the stall until the AoA is reduced to less than the critical AoA. There are likely a few planes (mostly military) with enough thrust to accelerate the airplane enough to change the relative wind aspect of AoA enough to reduce AoA, but they could probably be thought of more as rockets than airplanes. For nearly all airplanes, there is nowhere near enough thrust to do that. Trying to "power out" of a stall is a recipe for disaster.

The most effective and immediate way to recover from a stall is to release back pressure. In most cases, that will result in a loss of altitude. Adding power can help reduce the amount of altitude loss in the recovery, but will not be sufficient to recover from the stall by itself. Airplanes vary in the amount of altitude they require for recovery, from less than 100 feet to hundreds of feet. Available thrust is only one factor in altitude loss in recovery.

Your concern about low-altitude stalls is valid. They are the primary cause of a large portion of fatal aircraft accidents. The best way to avoid such accidents is for pilots to recognize approaching stalls and execute a recovery before the complete stall. Until the stall, the aircraft can be recovered without loss of altitude. Once the airplane stalls, at least some loss of altitude is inevitable, even with an immediate and correct recovery. In reality, most pilots who are taken by surprise by a stall at low altitude will be unlikely to quickly lower the nose because the ground is so near, and will therefore keep the airplane in the stall instead. That is why the idea of "powering out" of a stall is so dangerous. A pilot who has stalled close to the ground would love to think he or she could just add power to fix the situation rather than lowering the nose. It won't.

Answer 3

Yes, a plane can continue climbing even when it exceeds the critical AoA, as long as it has enough thrust and sufficient pitch for that thrust to have a large enough vertical component to maintain the climb. Actually, for a moment after passing critical AoA it will keep climbing due to inertia, but to keep it going, it will need, as us scientists call it, "stupid amounts of thrust".

The equations of lift, thrust, weight and drag during climb are nicely displayed on NASA website: The steeper the climb, the more thrust is needed to maintain climb. Also, the less lift is available, as in the case of flying at higher that critical AoA would be, the more vertical thrust component is needed to compensate for the lack of aerodynamic lift.

This is why for example fighter jets that may have thrust to weight ratios larger that 1 (engine has more thrust than the weight of the plane in its current configuration) have to fly at very high angles of attack to maintain or gain altitude when they are going slowly, near or beyond critical angle of attack: the engine needs to be pointed downwards enough to keep the thrust vector high enough to keep the aircraft flying, as the lift from the wings is weak.

Answer 4

One more try here. We have a 100m race. Average high school track athlete vs an Olympic gold medalist.

The Olympic gold medalist has to run through waist deep water. The high school athlete runs downhill through air.

Who do you bet on?

Now, if both were smart enough to stay out of the water, a more interesting race would be the Olympic runner uphill vs the high school runner downhill.

It would look pretty stupid to hold the race in water, up or down hill.

The difference with aircraft is that sink from loss of lift causes the relative wind to create an even higher AoA. This is why it is imperative to drop the nose faster than sink increases AoA, preferably at the pre-stall warning.

Some simple math can show an airliner falling at 200 knots can "power" up to 500 knots and still be stalled. From 30,000 feet that's around 100 seconds to impact. Making matters worse, now you risk V never exceed as you finally come to your senses and pitch down to unstall.

the physics of turning favor lower speed. Unstall first, then add power.

Essentially, it becomes a question of knowing the performance limits of the aircraft. As engines are generally at or near full power in a climb, the risks of continuing to climb in a stalled condition become obvious.

Can it be done? With hovering capacity, yes. Sustained climb while stalled? Slowly, yes. Economicly? No.

Most aircraft will lose significant airspeed well before 45 degrees climb angle. Even the Olympic runner cannot maintain speed on a steep grade. To get a better feel for this, draw some closed vector diagrams for various climb angles. The gap between winged flight power requirement and hovering flight power requirement is simply too great for most aircraft to simply "gun it" while ignoring aerodynamics.