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  #1  
Old 09-12-2016, 06:37 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,593
Default Strong Crosswind, not a great outcome

Well, its confession time. After 400+ hrs in the RV-8, and over 500 hrs of total tailwheel time, I just groundlooped the RV-8. Fortunately nothing damaged but my ego and confidence. But...

Usually when something doesn't turn out so well, I can play back in my head and think through what I did, what I should have done differently, etc. Learn from it.

In this case, I'm not sure I could have done anything differently.

Before the story, you probably need to know I have a rocket-style steering link, which I really like. It has a nice amount of spring give but is very responsive at low speeds.

In the pattern, the ATIS reported 16 kts at 260 degrees. Runway heading 190 degrees, paved, 75 ft wide. I'll do the math for you, that's 70 degrees off runway heading. The wind turned out to be a bit stronger than 16 kts though.

On final, I transitioned from coordinated flight to a stabilized slip. (I've always used a stabilized slip on final -- you just use your feet to keep the airplane aligned with the runway, and the stick to control the lateral drift. ) Over the numbers, wow it took a LOT of slip, but speed good, right on centerline, aligned with centerline. As I floated a bit, some of the slip naturally comes out since the wind is not as strong right near the ground. Still a lot of slip. One main wheel down, then the other. Still good alignment, right on centerline. Here is one thing I **might** have done differently: I did not make much effort to hold the tail up high. It was taking a lot of rudder pressure (left rudder) to keep aligned, and I just let the tail drop slowly as I slowed down. I felt the tail wheel hit, still good alignment, still on centerline, rolling out....still taking a lot of left rudder, but all good. Stick well right of center and a bit aft of center. **another thing I might have done differently: I could have had the stick full back to really firmly plant the tail wheel. Not sure it would have mattered**

Rolling out nicely when IN AN INSTANT, I was sideways, because the swiveling tail wheel had come unlocked and just swiveled. When I processed that and made the intentional command to go full hard left rudder and left brake, my foot was already there, way ahead of my brain. All I could do was just hold that and wait, pretty much a passenger at this point. The airplane slid in a gradual arc slowly diverging more in heading and scrubbing speed until it left the pavement, then it pretty much finished the groundloop. All the corners of the airplane stayed level thank goodness. I had to get out to turn the airplane more to get the tailwheel out of the soft stuff and up onto the prepared gravel alongside the runway so I could proceed to the apron with my tail between my legs. While I was out, I assessed the actual wind. It was at least 18-20 kts (being an old sailor I'm a pretty good judge of wind speed) at pretty close to perpendicular to the runway-at least 70 degrees, maybe a bit more.

Thinking back through it, I am not sure if the tailwheel unlocked because of more sideload than the latch pin could hold (might be worn, will inspect tomorrow) or if it unlocked because I reached full left rudder while steering on the roll out and the cam-action unlocked it at full rudder. I do remember that I was steering pretty smoothly, no weaving back and forth, and I was not being buffetted by gusts. It all seemed pretty smooth to the instant the tailwheel swiveled. Given that my foot was already full left rudder at the instant I thought about it, I'm kinda thinking it got to full travel from steering on roll-out.
If that's the case, it suggests that during roll-out, one must guard against getting to full rudder travel, and instead feed in more left brake with partial rudder.
One reason I am skeptical that it unlocked because of full rudder command is that the spring in the steering link would have been stretched to its stop and so even if the rudder did get to full travel, the tail wheel would not have.

It is also possible, I suppose, that the tailwheel didn't actually swivel, but rather broke traction and skidded because of insufficient downforce. I really kind of doubt that. Although I didn't have the stick hard back, it was certainly most of the way back, which is kind of a reflex to me as soon as the tail wheel touches. It might have been instructive to walk the runway and look at the skid marks (if there were any). Presence or absence of skid mark for the tailwheel would have answered this question definitively. Unfortunately, its a tower controlled airport, with big jets and stuff, so I can't imagine being allowed to go look at the runway after I taxied to the apron.

So, at this point, I'm kind of feeling like I did the best I could and not clear I could have done better. But ...

Had I held the tail off much longer with strong forward stick pressure, I would have had perhaps better rudder control, but perhaps not ENOUGH rudder control with the whole fin sticking up in that wind. I might have ended up with the rudder on the stop and still turning right. Now what?

With the tail wheel on the ground, it should be much more willing to go straight. Had I sucked the stick back hard, maybe the added downforce would have helped the tail wheel track the airplane straight....unless the swivel unlocked.

I think the tail wheel swivel unlocked. I think at that instant, I was doomed.

thoughts?
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 420 in 7 years
also LS-6-15/18 sailplane

Last edited by scsmith : 09-12-2016 at 07:14 PM.
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  #2  
Old 09-12-2016, 06:50 PM
Mike S's Avatar
Mike S Mike S is online now
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Location: Cameron Park Ca "o61"
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Default

Quote:
Originally Posted by scsmith View Post
Well, its confession time. After 400+ hrs in the RV-8, and over 500 hrs of total tailwheel time, I just groundlooped the RV-8. Fortunately nothing damaged but my ego and confidence. But...


thoughts?
My thoughts----------glad you and the plane are still in flyable condition.
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Rv-10, N210LM.
VAF 909
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Flying as of 12/4/2010

Phase 1 done, 2/4/2011

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  #3  
Old 09-12-2016, 06:52 PM
Chkaharyer99 Chkaharyer99 is offline
 
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Location: Pilot Hill, CA
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Default

Great description of what took place.

I'm too inexperienced to comment any further other than to say, I'm glad you and your plane are both Okay.
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  #4  
Old 09-12-2016, 07:11 PM
scsmith scsmith is offline
 
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Location: Ashland, OR
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Thanks for the kind thoughts.

One bit of humor to add...while I was sliding and diverging toward the edge of the runway, but not to the edge yet, I heard the guy in the tower say, "wow, look at that" or something to that effect, and I heard in the background the alarm sound that sent a fire truck out to me. Afterward, I wondered what made him key the mic to say that, rather than just say it. Probably second nature to him to key a mic when he talks.

I'm hoping Paul Dye and a few others that I think have described landing in stronger cross winds than this will share some insights.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 420 in 7 years
also LS-6-15/18 sailplane
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  #5  
Old 09-12-2016, 07:28 PM
springer springer is offline
 
Join Date: May 2012
Location: AZ/MN
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Steve, on my 8 I cannot apply immediate differential braking with my heals on the floor and to raise them to apply the brake I had to release rudder input for a split second. I now land with my heals off the floor in x-wind conditions. Differential braking combined with rudder input is very effective.

I had the same issue when I flew the Airbus.
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  #6  
Old 09-12-2016, 07:40 PM
scsmith scsmith is offline
 
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Location: Ashland, OR
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Quote:
Originally Posted by springer View Post
Steve, on my 8 I cannot apply immediate differential braking with my heals on the floor and to raise them to apply the brake I had to release rudder input for a split second. I now land with my heals off the floor in x-wind conditions. Differential braking combined with rudder input is very effective.

I had the same issue when I flew the Airbus.
Yes for sure. I promise if my airplane is still on the runway, my heals are off the floor and my toes are on the brakes. I have nice pedal extensions below the stock pedals that allow rudder use without brakes if desired, and with brakes if desired.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 420 in 7 years
also LS-6-15/18 sailplane
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  #7  
Old 09-12-2016, 07:51 PM
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Danny King Danny King is offline
 
Join Date: Dec 2004
Location: Southlake, Texas
Posts: 520
Default Two cents

I'm so glad this event ended without damage. You can simply add this to your piloting experience.

Based on your description of the sequence of events, holding the stick full back as soon as the tailwheel reached the ground is required!
The only other thing I'll offer is not to delay the application of brakes as the rudder reaches the full rudder stop.

I have passionately argued for builders not to modify the brakes on their RV-8 to prevent dragging. Pads are cheap ($40) to reline. It is very important that the brakes be "Right There" when needed in a situation like this.

Returning from Sun-N-Fun several years ago, I landed the Doll in a gusting 30K direct crosswind. The tires were chirping repeatedly during the rollout with heavy braking, but the aircraft stayed on the centerline. With crosswinds that strong, you cannot allow the aircraft to get too far into a swerve or the crosswind will start the win the battle for control.
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  #8  
Old 09-12-2016, 07:58 PM
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RV8iator RV8iator is offline
 
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Sounds to me like you did almost everything right. I've landed my 8 in 30kt direct crosswind and it's a workout alright. In this one, Monday morning qurterbacking, I would say it's extremely important to get the stick FULL back to get maximum down force on the tail wheel. Even at 15-20 knots it exerts quite a bit of downward pressure and will help keep the little wheel from sliding.

Glad you didn't bruise any more than your ego and thanks for reminding us all how quickly thongs can go south.
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RV 8, N8JL, 2600+ hours

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  #9  
Old 09-12-2016, 07:58 PM
oaklandaviator oaklandaviator is offline
 
Join Date: Dec 2014
Location: Somerville, Tn and Little Rock, Ar
Posts: 34
Default Chains

I have loose chains on my 8 and a friend has the Rocket link. He has told me about his breaking lose in a strong crosswind, but the loose chains on mine allow full deflection without that happening. I'd suggest changing back to springs and chains and running them loose. Seems to work much better and not as twitchy. Glad nothing was hurt!
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  #10  
Old 09-12-2016, 08:01 PM
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RV8JD RV8JD is offline
 
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Randy Lervold recounts the ground loop in his RV-8 on page 2 of this newsletter. His RV-8 had a steering link instead of chains. Unfortunately, the outcome wasn't as good as yours.

http://www.eaa326.org/Newsletters/eaa326-2-2004.pdf
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