Takeoff Drift RV-7A

[pierre smith]

...than the two-seaters but I also fly a 700 HP Air Tractor and I often have to have FULL rudder and then limit my throttle advance to only what the rudder can handle, if there's a crosswind from the left.

P-51's and a lot of the high horsepower WWII fighters also had that characteristic....more yaw than the rudder can handle at high power settings too early in the takeoff roll!

The -10 has a huge amount of rudder authority and you can just go full out but you'd better be ready!

Best

[Mike S]

Originally Posted by pierre smith

The -10 has a huge amount of rudder authority and you can just go full out but you'd better be ready!

Best

Yep.

And one more point, it takes air flow over the rudder to have control------less throttle equals less air flow.

Vicious circle, for an old taildragger pilot.

[flyboy1963]

As a low-time guy I can say my maneuvering near the runway was similar to Paul's.
Something I don't think has been mentioned; the pitch 'picture' is one component, but I also found that when I thought I was looking 'straight' ahead, I was focused on the spinner/cowl bump in the middle! ...needless to say, I was always crabbed a bit left.
As there is no nice line of rivets or cowl hinge line in front of my nose, I laid a piece of felt with a single line of white stitching on my dash. This reflects into the windshield just a bit, giving me a nice HUD of my aircrafts true longitudinal centreline.

My other comment; early in my flight training 30 years ago, I flew off a 150' x 5000' runway, and used much of the width on landings. My instructor saw the problem, and took me to a field with a 33' x 2500' strip.
PRESTO! suddenly I could track right down the centre ( no line even!) Funny how not wanting to mow weeds with the prop spurs one's lazy feet into action! Try it!

[sandifer]

Originally Posted by Bill Wightman

As the nose is lifted during rotation, the propeller will pull the nose even further left due to gyroscopic precession. Therefore, there will be a need for more right rudder as the airplane is rotated. Its just due to the gyroscopic effect of all the spinning mass on the nose of the airplane, and is quite normal.

Originally Posted by jetjok

Exactly, Bill!!
Paul, it is a matter of simply becoming more is sync with your plane. Your rotation was fairly abrupt, which exacerbates the gyroscopic force from your propeller, hence the rapid deviation to the left.

You've got it backwards. If we're talking gyroscopics only, then pitching UP (with a Lycoming-turning engine) will cause a yaw to the RIGHT. This is why you need a little left rudder pulling to vertical doing acro. It's the pitch DOWN that produces left yaw, requiring right rudder - which is partially the reason you need extra right rudder when you raise the tail on a taildragger....or do a push humpty. If you were flying a CCW turning engine (Russian radial), the reverse would be true.

During take-off, the gyroscopics of the rotation itself will actually work against the other left-turning forces. It's just that the other left-turning forces - spiraling slipstream and propellor P-factor (two different things) have a greater effect. Plus, gyroscopics only exist for the brief moment you are raising the nose. By the time the wheels have left the ground, you've pretty much got your pitch set, so gyro effects are no longer at play.

Regarding the drift after takeoff, once you break ground, the wheels no longer control your drift, so any force you have not controlled will make itself known to a greater extent.

[John Collier]

hand eye coordination. You are probably just to old to be flying such a high performance airplane.

On another note...I'm back in Tucson...how about a ride!

[David-aviator]

Sometimes squirrelly directional control is caused by not being aware both feet are hard on the rudders. Add right rudder and nothing happens - the left foot is hard on the left pedal. This sometimes happens when things are a little tense.

A conscious thought to use one foot for rudder control helps - especially on take off where it usually is all right rudder anyhow.

[privatepilot]

Best thing you can do is put in 3-4 hours in a glider, then you learn to use rudder real quick, or come to NZL and get ready for regular crosswinds 15kts and above, actually you may be being a little too sensitive with pedals, remember crosswind technique is a learned art , get some dual from a high time RV driver, dual instruction never hurts anyone.

[David-aviator]

Originally Posted by pierre smith

...than the two-seaters but I also fly a 700 HP Air Tractor and I often have to have FULL rudder and then limit my throttle advance to only what the rudder can handle, if there's a crosswind from the left.

P-51's and a lot of the high horsepower WWII fighters also had that characteristic....more yaw than the rudder can handle at high power settings too early in the takeoff roll!

The -10 has a huge amount of rudder authority and you can just go full out but you'd better be ready!

Best

Pierre,

Do you have rudder trim with the Air Tractor or the 10?

I do wish I had it with the 7A. I think about it a lot and it is on the airplane bucket list along with a few other items. The airplane has plenty of rudder authority, its just a matter of getting it right especially for take off. Rapid acceleration changes that effectiveness dramatically.

Seems to me I read a long time ago the P-51 procedure was full right rudder trim cranked in for take off. The RV's do not need that but the airplanes do have a wide speed range and the inflight un-trimmable rudder is hard trimmed for one speed and thats it. Except at that speed, the ball is not centered.

[pierre smith]

....to build in an electric rudder trim tab, because my leg gets tired having to hold right rudder while I climb to 8,000-9000 feet!

No, the Air Tractor doesn't have cockpit adjustable rudder trim either....but I seldom get higher than 300-500 feet.

Best,

[dhall_polo]

Originally Posted by Jamie

Hi Paul:

An airplane at yawing at high thrust, low speed when chainging pitch is completely normal (for example, in a Cessna 140 you almost have to stomp the rudder when you bring the tailwheel up), but I'll tell you why I don't have this problem in my 7A

Jamie - I hate to tell you this now, but you're 7A tailwheel is up as you taxi onto the runway.