Elevator problem, Need help!
05-20-2003, 09:17 PM
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Elevator problem, Need help!
I own a vmar cap 232. the one you see in my avatar. 
i have flown it many times successfully, but as i get more demanding, and the plane hs less to offer, i notice that on the manufacturer's high rates, when i pull back on the leevator really sharply, it rolls incredibly fast to the right, with the plane moving away from you. that is against the torque, so i can't really figure it out. :disappoin it is only when i pull back abruptly. if i give it a bit of time, it just does a really tight loop. anyone got any ideas?
i have flown it many times successfully, but as i get more demanding, and the plane hs less to offer, i notice that on the manufacturer's high rates, when i pull back on the leevator really sharply, it rolls incredibly fast to the right, with the plane moving away from you. that is against the torque, so i can't really figure it out. :disappoin it is only when i pull back abruptly. if i give it a bit of time, it just does a really tight loop. anyone got any ideas?
05-20-2003, 09:23 PM
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Elevator problem, Need help!
I am going to throw a "guess" out there......
Could the horizontal stab not be lined up parallel with the wing??
I only ask cause thats my biggest problem assembling kits, I have a hell of a time building straight tail feathers..........I always get in a hurry and dont double check them until its to late.
Anyway, thats my guess.
Could the horizontal stab not be lined up parallel with the wing??
I only ask cause thats my biggest problem assembling kits, I have a hell of a time building straight tail feathers..........I always get in a hurry and dont double check them until its to late.
Anyway, thats my guess.
05-20-2003, 10:12 PM
#3
It's called an Accelerated Stall...
and the right wing is experiencing it.
When you pull hard and fast on the elevator, the angle of attack reaches the stall angle, and for whatever reason, the right wing is stalling before the left wing. Since the Left wing is still flying but the right is not, the airplane rolls to the right. Essentially a snap roll.
It could be caused by any number of things:
Angle of incidence may be a fraction of a degree higher on the right wing than the left
Subtle difference of the shape of the Leading Edge of the wing between the Left and Right sides induces the stall on the right wing before the Left side stalls
Rudder may be out of trim.
There's probably a few more possibillities, but these are the first three that came to mind.
My Super Sportster 20 and 40 both exhibited the same behavior, especially the SS20. I just learned not to pull hard and fast unless I wanted to snap roll. A smooth but hard pull would keep the airplane flying on both sides, but a quick, hard pull would get the accelerated stall every time.
When you pull hard and fast on the elevator, the angle of attack reaches the stall angle, and for whatever reason, the right wing is stalling before the left wing. Since the Left wing is still flying but the right is not, the airplane rolls to the right. Essentially a snap roll.
It could be caused by any number of things:
Angle of incidence may be a fraction of a degree higher on the right wing than the left
Subtle difference of the shape of the Leading Edge of the wing between the Left and Right sides induces the stall on the right wing before the Left side stalls
Rudder may be out of trim.
There's probably a few more possibillities, but these are the first three that came to mind.
My Super Sportster 20 and 40 both exhibited the same behavior, especially the SS20. I just learned not to pull hard and fast unless I wanted to snap roll. A smooth but hard pull would keep the airplane flying on both sides, but a quick, hard pull would get the accelerated stall every time.
05-20-2003, 10:19 PM
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Elevator problem, Need help!
besides rebuilding or un-covering, are there any ways to get rid of this? my rudder needed no trim, heck, it required 5 clicks for the whole plane.
05-21-2003, 03:17 AM
#5
Elevator problem, Need help!
Spaceclam,
I'm going to take the safe road and say, "No." This is just one of the aircraft's peculiarities. Part of its "personality", if you will. It is how the aircraft responds when being asked to perform outside its flight envelope.
In order to change something to fix this trait, you have to know exactly what is causing it. If you can figure out what is causing the right wing to stall before the left, then by all means you can do something about it... but without knowing exactly what is causing the behavior, and throwing "fixes" at the symptom, you risk ruining the otherwise good flying characteristics of the aircraft. Throwing "fixes" at an unknown problem is risky at best.
My advice would be to leave the airplane as is... and know that if the airplane is going to snap out on you if you make a hard fast pull.
Also, I would try playing with the rudder trim... put in 1 or 2 or a few clicks of left rudder trim and see if the airplane still snaps. It really could be as simple as that.
I'm going to take the safe road and say, "No." This is just one of the aircraft's peculiarities. Part of its "personality", if you will. It is how the aircraft responds when being asked to perform outside its flight envelope.
In order to change something to fix this trait, you have to know exactly what is causing it. If you can figure out what is causing the right wing to stall before the left, then by all means you can do something about it... but without knowing exactly what is causing the behavior, and throwing "fixes" at the symptom, you risk ruining the otherwise good flying characteristics of the aircraft. Throwing "fixes" at an unknown problem is risky at best.
My advice would be to leave the airplane as is... and know that if the airplane is going to snap out on you if you make a hard fast pull.
Also, I would try playing with the rudder trim... put in 1 or 2 or a few clicks of left rudder trim and see if the airplane still snaps. It really could be as simple as that.
