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X-wind take-off technique in A models

lr172

Well Known Member
I fly from an airport with an E-W strip. Most strong wind is usually from the south and we have buildings and tall trees just south of the field. It makes for challenging landings due to the rotors, turbulence and variable gusting. It's not uncommon to see all three wind socks pointing in different directions. However, we never see really strong sustained cross wind at the runway level, only 30' above it.

I have mastered landing and taking off in these conditions, but don't get to do many x-wind landings or take-offs with more traditional cross wind conditions. Today I did some T&G's at a nearby airport with a 90* x-wind 15G20 (pretty sure most wind was 20). The landings were no issue, but I had an issue with the take-offs.

I have been carefull to do all of my take-offs with the nose wheel a few inches off the ground. I was taught to let the cross wind aileron out as the take off progresses, however, I rarely need much aileron in the situations that I fly and therefore don't get much practice. Today, I kept skipping sideways during the take-off roll and was subconsciously keeping the aileron full in too long to keep from skipping. On my final take-off, the gusts were strong and I must have had most of the aileron in to track down the center line. As I lifted off, the wing went down quickly and scraped. The damage is only the size of a quarter on the wingtip and an easy repair.

In thinking through what I did wrong, I realized the error of full aileron at lift-off, but it raised the issue of how else do I keep from skipping sideways. I had remembered reading that you need to keep some down elevator to keep the wheels planted and use tire friction to avoid sideways movement. I had become so afraid of going easy on my nose wheel that it seemed unnatural.

I was wondering how others manage this type of situation in their A model RVs.

Larry
 
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Rudder as well.

An RV has a lot of good rudder force available and you may want to start practicing using it along with you stick inputs. You may want to practice full slip landings and change from side to side during your practice. I would start you off at 3,000 AGL to be safe. Just a suggestion, Yours, R.E.A. III #80888
 
An RV has a lot of good rudder force available and you may want to start practicing using it along with you stick inputs. You may want to practice full slip landings and change from side to side during your practice. I would start you off at 3,000 AGL to be safe. Just a suggestion, Yours, R.E.A. III #80888

My question was about the take off roll. I am struggling to understand how a full slip would help. I know how to slip and routinely use slips to lose altitude on final and also kick out a crab to a slip over the numbers when necessary

I actively use my rudder on landing and take off (all phase of flight actually) and have no problems tracking down the centerline with the nose parallel in landing or take off. My question was about rotation/lift off. Are you suggesting to put in heavy rudder opposite the aileron at lift off? I had been holding just enough rudder to keep my fuse parallel with the centerline as I roll. If I had used anymore prior to lift off, I would also have been skidding as well or heading off the runway. A slip at lift off seems counter-intuitive due to it's increase in drag as well as a crab is fine once off the runway.

Larry
 
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Larry:

What would be your control inputs just as you touch down in a crosswind?

Logically, they should be the about the same in a take off in similar conditions.

True, in the former situation, you're decelerating while in the latter, you're accelerating; however, the theory should hold true.

John

PS No refunds... :)
 
for takeoff, when the wind is from the left it is more difficult than when it is from the right. when it's strong from the left I have needed to ride the right brake slightly until speed increases. I keep all three wheels on the ground until lift off.
 
Larry:

What would be your control inputs just as you touch down in a crosswind?

Logically, they should be the about the same in a take off in similar conditions.

True, in the former situation, you're decelerating while in the latter, you're accelerating; however, the theory should hold true.

John

PS No refunds... :)

I typically take out my crab over the numbers and then apply aileron into the wind and rudder in the opposite direction. I apply enough aileron to hold the centerline and apply whatever rudder is required to keep my longitudinal axis aligned with the the centerline. On takeoff, I am doing the same thing, the difference is that the plane is being forced level due to the wheels on the ground. It doesn't need the opposite rudder, as it is forced level by the wheels. The ailerons can't create a banking motion as they do on landing/flare.

In yesterday's case, the ailerons were opposing the x wind during the roll and the wheels on the ground were opposing any banking. As soon as the tires broke free, it banked. It seems to me as I think more about this that I just needed to hold it on the ground until ready and then simultaneously pitch up and take out the aileron. This would have prevented the skipping and avoided the wing drop at rotation. I suppose I subcounciously do this most times, but was overreacting to the excess wind. I also feel that I should have had the nose wheel planted in that situation and should not have followed my SOP of keeping it off the ground.

Maybe there is a technique where you bank it hard enough to get on one wheel and then use opposite rudder like a slip. I have heard of this, but was never taught it and never tried it.

Larry
 
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for takeoff, when the wind is from the left it is more difficult than when it is from the right. when it's strong from the left I have needed to ride the right brake slightly until speed increases. I keep all three wheels on the ground until lift off.

Thanks Steve. I am thinking that my issue here was not keeping all three wheels on the ground and using that friction/stabilizing force. Keeping the nose wheel up was likely keeping me light on the mains, as well, due to the extra AOA. The extra force would have likely prevented the side skipping and I wouldn't have had the urge to put in all of that aileron to oppose it.

Larry
 
On a crosswind takeoff, until the airplane leaves the ground the only thing that is capable of keeping you from being blown to the downswing side of the runway is friction from the tires.

If you can remain in place while not moving on the taxiway, then there's enough friction available to keep you straight on the runway, as long as you keep weight on the tires.. Use the wing to keep weight on the tires by using neutral or a small touch of forward stick until rotation. Use ailerons into the wind-fully deflected at the start, relaxing as you accelerate and the downwind wing starts to feel light.

Accelerate to a little faster than your normal liftoff speed and rotate positively so that the airplane leaves the ground cleanly. Typically the downwind wing will liftoff first, you need to be ready to relax the crosswind correction, which means to level the wings and relax the rudder correction to allow the airplane to weathervane into the wind.

Climb out with the airplane coordinated, in whatever crab angle relative to the ground that it takes to track the centerline. Strong crosswinds ar often gusty, so you might want to climb at a slightly higher airspeed than normal for better control authority.

If you use the "hold the nose wheel off and it will fly when it's ready" technique on a blustery day, there will be a brief period where you don't have the control authority to be much more than a passenger. Fortunately even the lowliest RV is well powered enough that this is a pretty narrow window and you'll usually get away with even sloppy technique.
 
The purpose of aileron input during a cross wind take-off is to counter any rolling tendency the wind is inducing. At low airspeed, the ailerons are not very effective so a lot of input is need, but as you gain speed the effectiveness is increasing so you keep reducing the input as needed.
If you are doing it properly so that you are correctly countering the rolling influence of the cross wind, the airplane should lift off exactly wings level.
If you are rolling suddenly as you lift off it is an indicator that you are inducing way more roll force (way to much aileron input) than the cross wind is influencing in the opposite direction.
RV's have very powerful ailerons. If you are using anything more than a small amount of aileron input at the moment of lift off, you are likely using to much, regardless how strong the cross-wind is.
 
On a crosswind takeoff, until the airplane leaves the ground the only thing that is capable of keeping you from being blown to the downswing side of the runway is friction from the tires.

If you can remain in place while not moving on the taxiway, then there's enough friction available to keep you straight on the runway, as long as you keep weight on the tires.. Use the wing to keep weight on the tires by using neutral or a small touch of forward stick until rotation. Use ailerons into the wind-fully deflected at the start, relaxing as you accelerate and the downwind wing starts to feel light.

Accelerate to a little faster than your normal liftoff speed and rotate positively so that the airplane leaves the ground cleanly. Typically the downwind wing will liftoff first, you need to be ready to relax the crosswind correction, which means to level the wings and relax the rudder correction to allow the airplane to weathervane into the wind.

Climb out with the airplane coordinated, in whatever crab angle relative to the ground that it takes to track the centerline. Strong crosswinds ar often gusty, so you might want to climb at a slightly higher airspeed than normal for better control authority.

If you use the "hold the nose wheel off and it will fly when it's ready" technique on a blustery day, there will be a brief period where you don't have the control authority to be much more than a passenger. Fortunately even the lowliest RV is well powered enough that this is a pretty narrow window and you'll usually get away with even sloppy technique.

Thanks for the detailed response. After thinking through this more it seems apparent that my efforts to protect the nosewheel were causing problems and your explanation supports that. It seems clear now that a positive force on the wheels will keep me planted and eliminate the need for aileron to keep me from going sideways. Just enough aileron to keep from allowing a rolling motion on the longitudinal axis.

Thanks for the replies.

Larry
 
The purpose of aileron input during a cross wind take-off is to counter any rolling tendency the wind is inducing. At low airspeed, the ailerons are not very effective so a lot of input is need, but as you gain speed the effectiveness is increasing so you keep reducing the input as needed.
If you are doing it properly so that you are correctly countering the rolling influence of the cross wind, the airplane should lift off exactly wings level.
If you are rolling suddenly as you lift off it is an indicator that you are inducing way more roll force (way to much aileron input) than the cross wind is influencing in the opposite direction.
RV's have very powerful ailerons. If you are using anything more than a small amount of aileron input at the moment of lift off, you are likely using to much, regardless how strong the cross-wind is.

Thanks for the explanation. Very helpfull.

Larry
 
The purpose of aileron input during a cross wind take-off is to counter any rolling tendency the wind is inducing. At low airspeed, the ailerons are not very effective so a lot of input is need, but as you gain speed the effectiveness is increasing so you keep reducing the input as needed.
If you are doing it properly so that you are correctly countering the rolling influence of the cross wind, the airplane should lift off exactly wings level.
If you are rolling suddenly as you lift off it is an indicator that you are inducing way more roll force (way to much aileron input) than the cross wind is influencing in the opposite direction.
RV's have very powerful ailerons. If you are using anything more than a small amount of aileron input at the moment of lift off, you are likely using to much, regardless how strong the cross-wind is.

I don't know about trike RVs, but many light, long wing tailwheel airplanes are well-served by using enough aileron to lift one wheel slightly in strong x-winds in order to prevent side load or scrubbing before lift off. Like a x-wind landing in reverse. I did that in my old RV-4 in strong x-winds. I never rolled suddenly at lift off. I used the amount of aileron required for the x-wind. In less x-wind, I might lift off wings level. In more x-wind, I might lift off a little on one wheel. It's a controlled roll allowance, not a sudden unexpected roll response due to excessive aileron input.
 
The purpose of aileron input during a cross wind take-off is to counter any rolling tendency the wind is inducing. At low airspeed, the ailerons are not very effective so a lot of input is need, but as you gain speed the effectiveness is increasing so you keep reducing the input as needed.
If you are doing it properly so that you are correctly countering the rolling influence of the cross wind, the airplane should lift off exactly wings level.
If you are rolling suddenly as you lift off it is an indicator that you are inducing way more roll force (way to much aileron input) than the cross wind is influencing in the opposite direction.
RV's have very powerful ailerons. If you are using anything more than a small amount of aileron input at the moment of lift off, you are likely using to much, regardless how strong the cross-wind is.

Scott, I certainly respect your experience in RVs, which is much greater than mine, and I agree with everything you wrote except for one minor quibble which can cause issues if somebody is trying to follow it exactly.

I don't have nearly your RV experience, but I have a fair amount of time in a trike airplane with a castering nosewheel.

At liftoff, you really should raise the downwind wing first, but only by the amount necessary to counter the effect of the crosswind. You're exactly right that RVs have very powerful ailerons and it's easy to overdo it.

If you lift off wings level and straight on the centerline, the wind is immediately pushing you downwind. You either have to bank into the wind (slip) or crab into the wind to maintain your ground track. At rotation, it makes more sense to raise the wing while maintaining the opposite rudder you've needed to offset the weathervaning tendency. It's much more natural and lower workload.

As soon as you're definitely airborne and climbing, relaxing the rudder input (enough to center the ball) and simultaneously relaxing the aileron inout will let the airplane weathervane into a wings level, coordinated crab and you can just track the centerline.

A lot of this is arguing about angels on the head of a pin, since this all evolves so quickly in an RV, but the essentials are the same in any trike airplane. It's just more obvious in a 150
 
On a crosswind takeoff, until the airplane leaves the ground the only thing that is capable of keeping you from being blown to the downswing side of the runway is friction from the tires.

If you can remain in place while not moving on the taxiway, then there's enough friction available to keep you straight on the runway, as long as you keep weight on the tires.. SNIP

Rolling tires will skid sideways (slip angle) long before a tire at rest will, even with equal weight on them. Next time you drive a car in a strong crosswind note the angle of the steering wheel. Obviously, this is more noticeable on a higher profile vehicle.

Back to the airplane, your first sentence is correct, which is why in order to keep the aircraft on the runway center line, the nose will have to be angled slightly into the wind during the takeoff roll. The mains will have some slip angle. In the 6A, even with all 3 wheels on the ground, the aircraft will become lighter on the gear as it accelerates, so it will necessarily cause main gear slip briefly before takeoff. I don't know about the other trikes, as their angles of attack are much lower when on all three gear.

The extreme example of this was when I landed and took off, with a 10 knot direct crosswind, from a runway which was completely coated with ice. The only possible way to maintain center line was with about a 10 degree angle between the fuselage and the runway.
 
Maybe there is a technique where you bank it hard enough to get on one wheel and then use opposite rudder like a slip.
You can do that in a floatplane, but then their wings are on top :eek: Another floatplane liftoff technique is to get up to almost liftoff speed and then add flaps momentarily to bump you off. I wonder if something like that would work for us on crosswind takeoffs. We could leave the flaps in trail to keep the weight on the wheels, then add flaps to lift off at the appropriate speed. I'm going to try that sometime.

My plane has a castering nose wheel, too, and I have the same problem with crosswind takeoffs and landings. Here's a short cringeworthy video of a recent crosswind landing I did at KGMU. Wind was 45 deg left of the nose at 12 G 20. The gusts kept me from settling down on the runway and the crosswind kept weathervaning me. I eventually saved my tires by raising the flaps. I should have totally stayed off the brakes but I was nervous because I had an RV-4 on my tail ;)

https://www.dropbox.com/s/6kcqnf3mlo8q55c/2017-06-18 GMU approach-landing.mp4?dl=0
 
Rolling tires will skid sideways (slip angle) long before a tire at rest will, even with equal weight on them. Next time you drive a car in a strong crosswind note the angle of the steering wheel. Obviously, this is more noticeable on a higher profile vehicle.

Back to the airplane, your first sentence is correct, which is why in order to keep the aircraft on the runway center line, the nose will have to be angled slightly into the wind during the takeoff roll. The mains will have some slip angle. In the 6A, even with all 3 wheels on the ground, the aircraft will become lighter on the gear as it accelerates, so it will necessarily cause main gear slip briefly before takeoff. I don't know about the other trikes, as their angles of attack are much lower when on all three gear.

The extreme example of this was when I landed and took off, with a 10 knot direct crosswind, from a runway which was completely coated with ice. The only possible way to maintain center line was with about a 10 degree angle between the fuselage and the runway.

Thanks for posting Alex. So, if you feel some slippage downwind, you'll correct by angling slightly into the wind? I suspect this would be short-lived, as it doesn't seem to get light on the gear until well into the roll. I realize that the advise from the RV-7's may be limited, as they sit much more level on the gear and therefore get more traction later in the roll than the 6A/4A. I assume the 8's and 9's are the same.

Larry
 
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If you are doing it properly so that you are correctly countering the rolling influence of the cross wind, the airplane should lift off exactly wings level.
If you are rolling suddenly as you lift off it is an indicator that you are inducing way more roll force (way to much aileron input) than the cross wind is influencing in the opposite direction.

A quick follow up. How do you know you are using just the right amount of aileron if the wheels are helping to resist the rolling moment as well? Is it just a matter of feel, whereby each lift off tells you whether you had it right and it ultimately becomes learned?
 
At liftoff, you really should raise the downwind wing first, but only by the amount necessary to counter the effect of the crosswind. You're exactly right that RVs have very powerful ailerons and it's easy to overdo it.

I don't disagree.
I didn't take the time to write an in depth explanation.... just being literal regarding how I fly RV's....
My goal is that the instant the wheels leave the ground the ailerons will hold the wings level. Immediately after leaving the ground I use roll input to stop lateral drift until transitioning to a crab into the wind.
Enough aileron to cause a strong roll as the wings are leaving the ground seems a recipe for disaster for many pilots. Is this what CFI's teach now a days?

A quick follow up. How do you know you are using just the right amount of aileron if the wheels are helping to resist the rolling moment as well? Is it just a matter of feel, whereby each lift off tells you whether you had it right and it ultimately becomes learned?

I am not good enough to judge it perfectly very often, but being close will mean only a very small roll occurs which can be compensated for very easily as the wheels leave the ground. Yes, it is something you learn with experience.
 
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....

Maybe there is a technique where you bank it hard enough to get on one wheel and then use opposite rudder like a slip. I have heard of this, but was never taught it and never tried it.

Larry

Ummm...that is how I was taught to takeoff in a crosswind and it was reinforced when I got my tailwheel endorsement.
 
Ummm...that is how I was taught to takeoff in a crosswind and it was reinforced when I got my tailwheel endorsement.

It makes sense. I land that way all the time. I wonder why with all of the aileron that I put in the other day that my downwind wing didn't lift. I suppose it was because I was light on the mains and it side stepped instead.

Larry
 
It makes sense. I land that way all the time. I wonder why with all of the aileron that I put in the other day that my downwind wing didn't lift. I suppose it was because I was light on the mains and it side stepped instead.

Larry

Did you get hit with a gust of wind at a bad time?
 
Wings on top?? Not on Piper Apache, Aztec, Cherokee, Beech 18 DC3 etc.

When I transitioned to low wings, we discussed the same technique. However, I was warned that some planes, like Pipers have the nose wheel connected to the rudders and you need to be careful when it touches down because the plane may dart.

If you land a taildragger, any taildragger, even a Breech 18 or DC3 and it touches down in a crab, you are in for a fun ride! The only way to keep then straight is with the rudder. Opposite aileron is then used to keep the airplane on the centerline.

The dihedral of the wing should keep it out of the dirt.
 
Lots of Interesting Answers

It might be best to do a cross wind refresher with a CFI.

That way you can pick their brain and go practice with someone with lots of experience.

Pranging your airplane is not the cheapest and best way to get the cross-wind techniques down.

It sounds like you are a good pilot, wanting to increase your skills, I've found it best to find a good CFI that you relate to, understand his approach to teaching etc., and go fly with their knowledge to help get your skills to the level you're aspiring too!

I'm going to call an exceptional CFI that helped me with my tail wheel endorsement, to help fine tune my RV-6 crosswind skills.

Found myself all over the runway a couple of days ago with 12ktsG18kts about 35-40 degrees from the left. Woke me up!

Best regards,
Mike Bauer
 
Did you get hit with a gust of wind at a bad time?

I don't think so. I was landing on 20 and the sock was straight out at 290. I think the winds were more sustained than gusting (~20 kts) when I landed/took off. The excess aileron clearly stopped me from skipping sideways, but it did not lift up on one wheel. There was some type of slip activity, as my rudder pedals were about neutral (x wind from the right).

Larry
 
Larry, when landing in a crosswind, regardless of where the little wheel or wings are, you should always use the rudder to keep the fuselage lined up with the runway. The ailerons are then used to move the plane left and right on landing. As the speed bleeds off, you slowly increase the control deflection until you have stopped moving, at which time you should have full deflection in, including up elevator.

Takeoffs are the opposite. Start with full deflection and take out your control input as needed.

I have rotated while rolling on one wheel because that is what is required to keep the plane tracking the centerline in a crosswind.

If you are uncomfortable doing this, it might be time to go up with a CFI and practice crosswind takeoffs and landings. Better yet, go get your tailwheel endorsement, that will be a BIG help.
 
RV's have very powerful ailerons. If you are using anything more than a small amount of aileron input at the moment of lift off, you are likely using too much, regardless how strong the cross-wind is.

Thanks for this insight, and to the OP for raising this issue. I hadn't thought of it previously, but it makes perfect sense.

I remember overcontrolling a bit in pitch on my first RV takeoff during transition training. Same sort of thing perhaps. The RV elevator seemed much more powerful and "crisp" compared to my Cherokee's.
 
Larry, when landing in a crosswind, regardless of where the little wheel or wings are, you should always use the rudder to keep the fuselage lined up with the runway. The ailerons are then used to move the plane left and right on landing. As the speed bleeds off, you slowly increase the control deflection until you have stopped moving, at which time you should have full deflection in, including up elevator.

Takeoffs are the opposite. Start with full deflection and take out your control input as needed.

I have rotated while rolling on one wheel because that is what is required to keep the plane tracking the centerline in a crosswind.

If you are uncomfortable doing this, it might be time to go up with a CFI and practice crosswind takeoffs and landings. Better yet, go get your tailwheel endorsement, that will be a BIG help.

Thanks Bill. I always use the rudder to keep my longitudinal access aligned with the runway in T/O and landing. I was saying that I thought there was a slipping type activity going on because it required about neutral rudder to maintain alignment during that take off. It usually requires healthy right rudder. It could also be that was what was required to resist the weather vaining.


Larry
 
Snopercod mentioned flap application as experienced from float planes. I did a few years in Alaska on floats and it was common in the C185 to pop flaps to break free from the surface. BUT, they were mechanical flaps. They were quick to deploy and quick to retract. I am not sure I would try it in my RV with a slow electric motor.
I read the entirety of the posts on this takeoff topic. Seems like a simple case of over control. The RV is sensitive and has good authority. All of the details brought up in the responses seem valid for use. Just don't over use them.
Best of luck in your training!
 
Snopercod mentioned flap application as experienced from float planes. I did a few years in Alaska on floats and it was common in the C185 to pop flaps to break free from the surface. BUT, they were mechanical flaps. They were quick to deploy and quick to retract. I am not sure I would try it in my RV with a slow electric motor.

I was thinking the same thing. Flying the LS-3(glider) I owned a couple of years ago it was standard practice to start the ground role with negative flaps and take off by moving the flaps positive. That gave you maximum control. However, the flaps were manual so you could quickly apply them. You really didn't move them back. You "pulled" them back quickly. I think the flap motor on my RV-8 is way to slow to be effective in that situation.

Oliver
 
I have used half flap when there is a strong crosswind to get off sooner. Set it before adding power.
 
Deploy Flaps When Reaching Takeoff Speed

Today I started my takeoff roll with flaps in trail, and deployed them when reaching my normal takeoff speed. It lifted me right off! I tried to export the video, but the latest Garmin Virb Edit update really messed up the program. I'll post it later if I can get the program working. Edit: It started working:

Deploy flaps reaching takeoff speed: https://www.dropbox.com/s/kxi2i3tufh0p13o/2017-06-26 Flaps on Takeoff.mp4?dl=0

Retract flaps when touching down: https://www.dropbox.com/s/ychsk27ccuxi5ad/2017-06-26 Crosswind Slip.mp4?dl=0
 
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