The minimum altitude is actually part of even the amateur pilot license rules: at least 500 feet at all times except during takeoff and landing, plus single-engine planes are suppose to, when above an inhabited area, be high enough to be able to glide out of it before reaching the ground (which is why, for example, in cities you see helicopters following rivers and large avenues).
Further, something like a Cessna 150 is pretty light and designed to go slow (cruise speed is something like 90 knots - so a bit over 100km/h) and thus has a low stall speed and can glide quite well (remember that the air drag force is proportional to the square of speed, so a plane whose stall speed is low doesn’t need to trade as much potential energy - i.e. height - to offset the loss of speed from drag and stay above that stall speed).
It’s the stuff designed to go really fast - like jet fighters - that pretty much can’t glide because aerodynamic designs that optimizes for speed (and agility) actually reduce lift (and thus increase stall speed).
Yeah, modern jet fighters have horrible glide ratios. They are completely reliant on the engine to provide the brute force to push it through the air. Which is also why the F-35 and similar are so reliant on computers; they’re constantly correcting to actually stay flying.
But, if they do go down, usually it’s not toward a populated area, and the crew can eject.
The minimum altitude is actually part of even the amateur pilot license rules: at least 500 feet at all times except during takeoff and landing, plus single-engine planes are suppose to, when above an inhabited area, be high enough to be able to glide out of it before reaching the ground (which is why, for example, in cities you see helicopters following rivers and large avenues).
Further, something like a Cessna 150 is pretty light and designed to go slow (cruise speed is something like 90 knots - so a bit over 100km/h) and thus has a low stall speed and can glide quite well (remember that the air drag force is proportional to the square of speed, so a plane whose stall speed is low doesn’t need to trade as much potential energy - i.e. height - to offset the loss of speed from drag and stay above that stall speed).
It’s the stuff designed to go really fast - like jet fighters - that pretty much can’t glide because aerodynamic designs that optimizes for speed (and agility) actually reduce lift (and thus increase stall speed).
Yeah, modern jet fighters have horrible glide ratios. They are completely reliant on the engine to provide the brute force to push it through the air. Which is also why the F-35 and similar are so reliant on computers; they’re constantly correcting to actually stay flying.
But, if they do go down, usually it’s not toward a populated area, and the crew can eject.