Aerobatics question

[DoinTime]

Doin Time--top rudder will not maintain altitude in a 90 degree bank??? Have you ever seen anyone fly knife edge & maintain altitude & a steady heading? How do you think they maintain altitude? With smoke & mirrors? They do it with top rudder which creates a positive AOA on the bottom side of the fuselage. They are flying the airplane off the side of the fuselage with top rudder & just enough elevator to keep it from turning.

If you believe you can maintain altitude by flying the side of the fuselage I have some Arizona swamp land for sale. I've seen the airshow maneuver and it is essentially smoke and mirrors. You initiate the maneuver at low level at one end of the airport, just before you roll to the knife edge you pull hard on the elevator. This will give you adequate vertical kinetic energy to stay aloft without the use of your wings until you are on the other side of the airport and you can roll wings level again. A profile view of the maneuver will show a climb at one end of the maneuver and a descent at the other end. Because it is performed at such close quarters to the onlookers the altitude change is hard to pick up on.

Wings are installed on airplanes for reasons other than roll control.

 

[EagleRJ]

Dointime, the fuselage does produce some "barn door" lift (Newton's Third Law) during knife edge flight, but remember the engine too. Most of those planes have 300 horsepower pulling a 1500 pound airframe, so there's power to spare. Remember which force causes an aircraft to climb? The vertical componant of thrust. Same thing when the plane is knife edge. There's enough extra power to allow level flight even with an inefficient lifting surface like the fuselage.

I've seen planes not only maintain altitude, but climb in knife edge at airshows.

 

[ShawnC]

I've seen planes not only maintain altitude, but climb in knife edge at airshows.

While their crew chiefs grind their teeth and hope their watching cylinder head temps. No one that I know of has perfected a sump for the oil for knife edge flight.

 

[rfeathe1]

Doin Time--THERE ARE NON SO BLIND AS THOSE WHO WILL NOT SEE!!!!!!

 

[rfeathe1]

Eagle RJ--I used to do knife edge in a 150 HP Citabria the whole length of a 3000' runway holding altitude & heading. Airplanes with relatively flat sided fuselages do better than airplanes with rounded or skinny fuselages in this manuever.

 

[VMA214]

Getting back to the original question...
1 "G" flight is a "steady state" in the longitudinal axis. Maintaining the angle of attack that produced that 1 "G" flight while rolling about the longitudinal axis will begin to lessen the lift vector in the vertical. Since the weight vector will remain constant, the nose will begin to drop. When the airplane is upside down you will effectively have 2 "G" (combining both the angle of attack to produce the 1 "G" flight and the weight vector) and the nose will fall towards the ground even faster. As the roll is continued to the upright the nose will continue to head toward the ground but the rate at which it heads toward the ground will lessen. Your heading should be back to the original heading.

Recapping...unless you start this somewhere above 2500' and you bring the throttle back significantly toward idle...and assuming you are in a Citabria, of course with your parachute on...its going to get really loud (wind noise) and the dirt will be getting really CLOSE!