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  #1  
Old 03-30-2011, 07:18 PM
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Pmerems Pmerems is offline
 
Join Date: Jan 2006
Location: Tucson, AZ
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Default Takeoff Drift RV-7A

Gents,

Being a new RV-7A driver (23 hrs) I need some advice.

During my takeoff roll I do my best to track the centerline of the runway. I am not the best rudder man but I am learning. My problem is just as I start to rotate my RV-7A drifts quickly to the left about a few feet. Seems to shift more with left minor crosswinds.

I have been using a MD80 micro cameras taped to my canopy frame (tip-up) and I capture my takeoff and landings on video so I can critique my flight Works great, I get 50 minutes of video from the camera and it only costs about $20.

What am I doing wrong? Am I not using enough rudder? I am concerned if I use more rudder on takeoff roll I will drift to the right side before becoming airborne.

Any Advise? I am still learning.

Thanks,
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Paul Merems (EAA Tech Counselor, EAA Sheetmetal Workshop Instructor/Volunteer 12 yrs)
ExperimentalAero-HANGAR BANNERS
www.experimentalaero.com
RV-7A (Flying since 2010)/RV-4 (sold 1990)
Tucson, Arizona 85749
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  #2  
Old 03-30-2011, 07:23 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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It isn't like rudder is an on/off control. Use however much rudder you need to maintain centerline through the takeoff roll. Also, add in some right aileron. That'll help too.
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  #3  
Old 03-30-2011, 07:28 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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Default

It takes right rudder to counter the engine and prop torque, so train your feet to add rudder with throttle application on take-off. It might help to start with the right rudder applied and then add throttle.

In general,, and you already know this, use enough rudder to keep the nose straight.

Incidentally, since some right rudder is necessary with no crosswind, think of that as the neutral rudder position for take-off. Then you can see how you have less total rudder available in a left crosswind than you would in a right crosswind.

That means that you can handle more right crosswind than left - something to consider when choosing which runway to use.

Dave
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  #4  
Old 03-30-2011, 07:33 PM
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Jamie Jamie is offline
 
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Location: Atlanta, GA
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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 -- it's because I don't rotate the airplane off the ground.

When I go full throttle I have the stick about 1/2 to 3/4 back and left or right aileron as cross wind conditions necessitate (and of course rudder to track straight down the runway). As I accelerate and the nosewheel starts to lift (<30kts) I take out some of the elevator and accelerate with the nosewheel only slightly off the ground. I then let the airplane fly itself off the ground. I will typically hold the airplane in ground effect until 80kts IAS. That's just my personal preference as I like to use that airspeed for climb on cool days. On warm days I'll quickly establish climb at 100kts for cooling.

I would encourage ever RV-XA driver to go out and do touch and gos with the nosewheel never touching the ground.
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  #5  
Old 03-30-2011, 07:59 PM
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Pmerems Pmerems is offline
 
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Location: Tucson, AZ
Posts: 818
Default Back pressure

Gents,

I don't believe I am getting the nose off the ground soon enough. I start my roll with neutral stick position. Once rolling I begin to pull back but the nose doesn't come up for a while. When the nose comes up it is only another second or so before the plane is off the ground. I keep worrying about pulling too hard on the roll and getting airborne too early.

Here is a video one of my recent takeoffs. Slight cross wind from the left (5 kt). Notice the drift after lifting off.

www.experimentalaero.com/Videos/takeoff1.wmv

Any advice?

Paul
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Paul Merems (EAA Tech Counselor, EAA Sheetmetal Workshop Instructor/Volunteer 12 yrs)
ExperimentalAero-HANGAR BANNERS
www.experimentalaero.com
RV-7A (Flying since 2010)/RV-4 (sold 1990)
Tucson, Arizona 85749
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  #6  
Old 03-30-2011, 08:13 PM
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mosquito mosquito is offline
 
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Location: Hendersonville, NC
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Default Right rudder!

Hi Paul,

Watching that video, I can actually hear the Voice of Greg (my Instructor) saying 'right rudder!'. There's a moment of transition when the wheels leave the ground that the balance of the aircraft immediately changes... just have to learn when to kick that rudder in. In my very limited experience, that skill comes naturally (but at a time of it's own choosing!).

Have you done any tailwheel training? I think the TW configuration amplifies the dynamics at play... but they are still there with a nose wheel.

Pretty reasonable video quaility for the money...

-jon
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Last edited by mosquito : 03-30-2011 at 08:16 PM.
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  #7  
Old 03-30-2011, 08:32 PM
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Av8torTom Av8torTom is offline
 
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Location: Yardley, PA
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Default Ball?

Paul,

What's the ball saying? Is it centered? That's the first objective. But, coordinated flight isn't going to keep the airplane from drifting if there is a cross wind. You need to counter act that with rudder AND stick so that the airplane is crabbing down the length of the runway as needed in order to track the center line. If you use the rudder alone to do this you'll find yourself cross controlled.

Tom
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  #8  
Old 03-30-2011, 09:35 PM
DENMACRES DENMACRES is offline
 
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Default drift

NOSE WHEELS ARE ONLY FOR TAXI.
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  #9  
Old 03-30-2011, 09:47 PM
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Toobuilder Toobuilder is offline
 
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The airplane is having it's way with you and you're letting it! Time to become the pilot in "command" and use the rudder! Those pedals on the floor are not just for taxi...

How much rudder?

...as much as it takes!

Watching the video, my right foot pressed the floor under my desk as you were trying aileron. I'd say you should go get a tailwheel checkout - that will quickly cure you of your paralyzed legs.
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Last edited by Toobuilder : 03-30-2011 at 09:52 PM.
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  #10  
Old 03-30-2011, 09:56 PM
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sbarger24 sbarger24 is offline
 
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Location: Grand Island, NE
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Hi Paul

I don't have a lot of hours on my RV 7A either only 60 hours in fact. I did take several hours of transition training and was taught just like Jamie's discription. Holding the stick back during initial take off until the nose comes off the ground then pushing the stick forward keeping the nose wheel just off the runway until the plane flys off. I will add that how you have the airplane trimmed makes a difference. I like to trim the plane so that the control force is light bringing the nose off the runway. I have manual trim and basically a couple turns from neutral position for a pitch up attitude. Anyways hopefully that makes since and helps.
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