Question about lift
Posted by 2LeapingLizards@reddit | aviation | View on Reddit | 8 comments
Hello!
I would imagine this is a fighter jet question (I would hope commercial flights aren’t doing this).
At completely level flight, the lift is mainly generated from the wings (yes?). When the aircraft rolls 90° in either direction, the wings would now not be producing lift because they’re parallel to gravitational force. Would that mean the vertical stabilizer is the thing generating lift? If so, how does it do so when the vertical stabilizer’s surface area is so much less in comparison? They can seemingly continue straight ahead at the 90° for as long as they want (though I’m sure there is some limitation).
Thank you!
22Planeguy@reddit
The real oversimplified answer here is that the aircraft does not produce enough vertical lift at 90° of bank to maintain altitude. The vertical stabilizer is a symmetrical air foil so at 0° aoa from the relative wind, it does not produce lift.
The aircraft is either not actually maintaining 90° aob, has a slight nose up attitude, or is losing altitude.
West-Organization450@reddit
Beretta has it right…the fuselage becomes the primary lifting surface once an airplane gets to true 90deg. ‘knife edge’ flight. In most planes it’s just a terribly inefficient lifting surface that requires lots of thrust and angle of attack to maintain altitude. Jet fighters rely mostly on thrust and speed to make a knife edge pass down a runway. The airplanes in my experience that excel at actually maintaining knife edge for quite a ways are the different Pitts Special aerobatic biplanes. They have a fuselage shape that actually provides a little lift and with enough horsepower and some speed going in they’ll maintain a pretty nice knife edge for quite a while! It’s just a combination of rudder to hold the nose up (AOA), aileron to keep the roll-coupling from the rudder at bay and elevator to keep direction where you want it. Pretty fun!
anactualspacecadet@reddit
They are still producing lift, the lift is simply no longer countering gravity. If you ever learn to fly fighters there a fun little chart that tell you how many Gs you need to maintain level flight and at 90° of bank its the little infinity symbol lol
massunderestmated@reddit
Isn't it just 1/cos(bank angle)?
anactualspacecadet@reddit
Idk i dont do math i just fly the plane
Thomas71999@reddit
Great question. I learned something new today from the helpful folks in the comments
cross_hyparu@reddit
To oversimplify it, planes that can fly maneuvers like that use thrust to offset the loss of lift and will use the rudder to keep the plane at 90 degrees. The plane will start to pull in the direction of the turn without any rudder input. That kind of maneuver isn't really sustainable for any length of time.
beretta01@reddit
The fuselage can generate lift too….look up “beta” angle. But yeah, generally speaking….90° banks might be 85° banks and when you’re pulling 8 G’s, it doesn’t take a lot of vertical component of that horizontal “lift” generated to maintain altitude.