snap rolls?

[DigitalBurn]

Hi all. I have to ask what may seem like a silly question.

What is meant by SNAP roll? I can do aileron rolls, what is a snap roll? Or for that matter, what is a barrel roll?

[Dave Robelen]

Hello Digitalburn,
Taking things a little bit at a time, let me try to clear up the difference in the three types of rolls that you mentioned.
The "aileron roll" is also called an axial roll, because when it is done correctly the airplane appears to rotate about the centerline as it passes through the sky. You would normally use small amounts of up and down elevator to maintain a constant attitude.
The "Barrel roll" is a variation of the aileron roll where the airplane generally flies through an arc as it rotates, starting low, climbing asit rotates to the inverted, and dropping as it comes back upright to the original attitude. It will also appear that the fuselage centerline is rotating about some axis that is outside of the airplane. Done properly it is a really pretty manuever, and challenging to perform correctly.
The "Snap roll" is a manuever that involves stalling the wing and forcing it to rotate at the same time. The roll rate is generally much faster than what can be done with the ailerons alone. This is one of those "sticks to the corners" abrupt manuevers. That is say, full up, full left aileron, and full left rudder all at the same time. Many trainer models will not perform this because there is not enough elevator force to truly stall the wing.
The snap roll is also what you are seeing when an airplane that is slowed up too much suddenly drops a wing and rotates (usually into the ground). In aerobatics the snap roll may be performed with multiple rotations, or a fraction of a rotation as part of another manuever. The primary distinction between a snap roll and a tailspin is that the spin starts in level flight and drops into a vertical rotation of multiple turns, where the snap roll will maintain a line that is generally not straight down. The forces are exactly the same.
I hope I cleared uit up a bit, Dave

[DigitalBurn]

Yes, that clears things up. I understand exactly what you mean. Time to practice, practice, practice.