Directional Control on Rollout

After seeing that another RV-8 ran off a runway last week I thought I’d share my experience with my own directional control on rollout issues.

I finished my RV-8 in 2014. It had a Bell tailwheel fork and a single steering arm on it. It looked dandy! I liked the way it handled while taxiing and I was happy. It wasn’t very long after my first flight that I noticed controllability during the landing rollout was not as good as I would have liked. I never left the runway or scratched anything but came way too close on more than one occasion. Sometimes the rollout was straight as an arrow, but the excitement started as soon as the SLIGHTEST correction was made to chance direction. Wind speed or direction did not matter. My RV grin turned to an RV grimace right before touchdown.

I talked to local experts and any RV guys I found at OSH, phoned distant experts and poured through VAF archives. I checked toe in/out several times and it was fine. I was SURE I must be dragging a brake since sometimes it would be turning opposite the rudder input. Usually turning right while applying full left rudder AND brake. I found Randy Leverold’s rudder pedal extension plans and modified my pedals. Initially I thought I had the problem solved but it was only about a dozen landings or so before the same symptoms popped up.

My attention turned to the tailwheel again. I propped the tail up on a saw horse, checked the adjustment again, checked the locking pin operation again and checked for freedom of movement again. I went back to VAF and read about what a docile pussy cat the RV-8 was to land. I could 3 point or wheel land on either or both mains with no problem, but just couldn’t seem to keep it going straight. Either my issue was unique, or everyone just figures it’s a problem with the pilot and they’re embarrassed to say anything. While the thought of selling it and buying a 150 flashed through my head, I got the idea to lift the tail by the bottom of the wheel. I interlaced my fingers and lifted the tailwheel while turning it left and right at the same time. The more weight I put on it, the harder it was to turn. By the time I had the tail totally lifted up I could barely turn it. Light bulb time! I greased it up really good and flew it again. It was magnificent! But in only 5 to 10 landings it started to get stiff again. I looked back and found there were 30 landings on the grease job prior to discovering the binding. I disassembled the tailwheel assembly and looked for burrs, or anything amiss and found nothing. I put a grease zerk in the tailwheel yoke and polished everything in there really well. I’d give it a little pump of grease every other time I went flying and flew it until the next winter.

My fix was to buy a tailwheel yoke with the ball bearing from JDair, keep my Bell fork, install the stock springs and make custom steering cables attached to new attach points on the rudder (copied from Dan Horton). Another thing I learned was that full rudder deflection should not unlock the tailwheel. I couldn’t achieve that without machining out a little of the key slot in the top of the yoke if I kept my single steering arm.




With 10,000 RVs flying and a bunch of them tail draggers I don’t think there’s anything wrong with the Van’s yoke, but the combination of MY stock yoke, and MY Bell fork and (maybe) MY steering link did not allow ME to steer.
I have been flying with this tailwheel set up for almost two years and it has transformed my tasmanian devil into the pussy cat I read about.

The lack of complaints about this prompted me to write about my experience. Maybe it’s unique, maybe not, but if it saves just one RV I’ll be happy.

I am curious if this has caused any loss of control accidents? You’ll never know unless you lift and turn.

I too have a Bell fork on my RV-7 but have the Tail-Lynx cable and spring set up. Never had the roll out directional problem you describe - but I can definitely tell when it is time to lube the fork! Mine gets difficult to steer when taxing - rudder pedal pressure just stretches the springs on the Tail-Lynx. When the wheel does move, it moves suddenly. I have described it as "notchy" steering. Cleaning and re-lubing the fork shaft fixes it for another bunch of hours.

Rocket single arm steering

NLPete said:

After seeing that another RV-8 ran off a runway last week I thought I?d share my experience with my own directional control on rollout issues.

I finished my RV-8 in 2014. It had a Bell tailwheel fork and a single steering arm on it. It looked dandy! I liked the way it handled while taxiing and I was happy. It wasn?t very long after my first flight that I noticed controllability during the landing rollout was not as good as I would have liked. I never left the runway or scratched anything but came way too close on more than one occasion. Sometimes the rollout was straight as an arrow, but the excitement started as soon as the SLIGHTEST correction was made to chance direction. Wind speed or direction did not matter. My RV grin turned to an RV grimace right before touchdown.

I talked to local experts and any RV guys I found at OSH, phoned distant experts and poured through VAF archives. I checked toe in/out several times and it was fine. I was SURE I must be dragging a brake since sometimes it would be turning opposite the rudder input. Usually turning right while applying full left rudder AND brake. I found Randy Leverold?s rudder pedal extension plans and modified my pedals. Initially I thought I had the problem solved but it was only about a dozen landings or so before the same symptoms popped up.

My attention turned to the tailwheel again. I propped the tail up on a saw horse, checked the adjustment again, checked the locking pin operation again and checked for freedom of movement again. I went back to VAF and read about what a docile pussy cat the RV-8 was to land. I could 3 point or wheel land on either or both mains with no problem, but just couldn?t seem to keep it going straight. Either my issue was unique, or everyone just figures it?s a problem with the pilot and they?re embarrassed to say anything. While the thought of selling it and buying a 150 flashed through my head, I got the idea to lift the tail by the bottom of the wheel. I interlaced my fingers and lifted the tailwheel while turning it left and right at the same time. The more weight I put on it, the harder it was to turn. By the time I had the tail totally lifted up I could barely turn it. Light bulb time! I greased it up really good and flew it again. It was magnificent! But in only 5 to 10 landings it started to get stiff again. I looked back and found there were 30 landings on the grease job prior to discovering the binding. I disassembled the tailwheel assembly and looked for burrs, or anything amiss and found nothing. I put a grease zerk in the tailwheel yoke and polished everything in there really well. I?d give it a little pump of grease every other time I went flying and flew it until the next winter.

My fix was to buy a tailwheel yoke with the ball bearing from JDair, keep my Bell fork, install the stock springs and make custom steering cables attached to new attach points on the rudder (copied from Dan Horton). Another thing I learned was that full rudder deflection should not unlock the tailwheel. I couldn?t achieve that without machining out a little of the key slot in the top of the yoke if I kept my single steering arm.

http://i67.tinypic.com/2s94zz7.jpg

With 10,000 RVs flying and a bunch of them tail draggers I don?t think there?s anything wrong with the Van?s yoke, but the combination of MY stock yoke, and MY Bell fork and (maybe) MY steering link did not allow ME to steer.
I have been flying with this tailwheel set up for almost two years and it has transformed my tasmanian devil into the pussy cat I read about.

The lack of complaints about this prompted me to write about my experience. Maybe it?s unique, maybe not, but if it saves just one RV I?ll be happy.

I am curious if this has caused any loss of control accidents? You?ll never know unless you lift and turn.

Click to expand...

I had a (I think it was a Rocket" single arm) on my 1st RV 8. Almost every time I landed it, (wheel landings), and the tail came down, I thought for sure I was going off the runway into the grass. It was "really" bad with a guy in the back seat.

Now on my 2ed RV 8, I've got the double chain throw. No problems whatsoever. I'd switch if I were you.

I tried many different greases on my tailwheel? most all were very short term fixes. Finally tried Lubriplate 630 AA grease. Lasts MUCH longer than anything else I?ve tried. Now I relube it every other oil change and it never gets sticky. Your results may vary!

Similar RV-6 Learning Experience

When I bought my RV-6, had similar issues. Thought it was just me having issues learning to fly a tail wheel.

Decided to ask some questions here. Learned real fast I needed to look at the operation.

Lifted the tail, used a jack stand, and pulled apart the steering assembly. The grease had turned into a "glue" locking the worn out spring, allowing only "full castering" operation.

Before my own investigation, with help from here, each time I asked a non-homebuilt savy AP, they just greased it again.

Bought new plunger and spring, cleaned up all the gook from the grease. Now I use a special dry lube for bicycle chains. Re-lube every three months.

Works like a charm, all the experience from the full castering landings taught me to be quick on the rudders.

Now directional control for landings is no longer a question of, "which way is it going to go?"

Glad you found your issue, thank you for sharing your experience.

Best regards,
Mike Bauer

thank you bubba

Thank you to all

Thank you, I will study bubba

I used to get those swerves - tower must have had a great time when they saw me come in. I have the solid steering arm. I found a solution that works for me:

Firstly, I always wheel it on - tail slightly low. So my solution won't work for the 3 pointers.

Then I keep the tail up on rollout...always moving the stick forward as the tail starts to come down.

Finally, the tail eases itself down slowly as the speed gets really low. Tailwheel touches nice and gently. By that time the plane is going so slowly that it's easy to control. There's no massive lunge for the weeds.

As you said, many people have different experiences. I have the stock Van's tail wheel with about 1 inch of slack in the chains (per the plans) and have been very happy with the control ability. I think the slack helps with controlability at landing speeds.

I got my RV-7 back from annual a little over a year ago and it was really hard to control on the ground. I knew nothing was binding but it was very difficult to initiate a taxi turn. So I also knew I had to pull the system apart and see what was happening. As soon as I touched the pivot area, I knew what was wrong. The mechanic had 'serviced" it and used some type of very tacky substance. It wasn't grease per se, it was very sticky to the touch, like fuel lube. So I pulled the system apart, cleaned all the "lube" out, and greased it with my chosen white lithium grease. Smooth as butter.

I had the complete opposite situation. The pedals felt very loose on rollout when I had the stock setup.

I changed it for the Flyboys Condor2 8" Pneumatic Tire and Tailwheel Fork unit https://www.flyboyaccessories.com/product-p/1152.htm and the RV Rocket Steering Link https://www.flyboyaccessories.com/RV-Rocket-Steering-Link-p/1200.htm . It is steady like a train on tracks now. I use a white grease from Germany that I had left over from when I owned a AutoGyro MTO and that's what has to be used on the main rotor blades so even with lots of heat it doesn't "melt away". In fact when I serviced it last week the old grease was still good.

The whole idea is to enjoy all of the flight events - including landings.
I think tailwheel setup is overlooked by many builders. We expect to just install it and it will work perfectly (like everything else in the kit) but not so. It is hard to know what is a good setup because the airplane is typically new to us - so how would we know?
My experience:
1. Make sure full rudder deflection does not unlock the tailwheel. I had to add almost 2 inches to the tailwheel arm to make this happen on my setup.
2. Provide some slack on the cables (or chains). I have maybe 1/4 inch per side (Tail-Lynx cable and spring set up).
3. Clean and relube the components at every other oil change.
4. Land with the centerline of the fuselage straight with the direction of travel. Don?t be afraid to go around.
5. Land at the slowest possible speed. I three point land. Everyone has to determine this for themselves and whether they want to 3 point or wheel land.

With a good tailwheel setup, these airplanes are fun to land. I am always trying for that perfect landing - which only happens when nobody is around to see it!!

I recall a service note from Vans that says to service the spring pawl with WD-40, not grease.

I know for sure that Maule recommends this https://www.lightlink.com/ithnet/Orgs/EHFC/maul tailwheel.pdf

Vern

Mine says grease.

Here's the grease I use. It's very sticky. It's the only one to use on the bearing on the rotor head and it's called " Lagermeister WHS 2002 ". In Canada I read they found a replacement grease with the same properties called " Chevron Grease EP Delo NLGI 0 " and it's sold on Amazon.

I use Krytox 205 grease. It was originally purchased to lube the o-rings in my fuel caps but works great in the tailwheel swivel as well. It is expensive stuff but very little is required so it goes a long way. Bought mine on Amazon.

FWIW some info below.
Where can Krytox lubricants be used?
Krytox lubricants can be used in applications where nonflammability, oxygen compatibility, materials compatibility, high temperature stability, and resistance to aggressive chemicals are requirements. Some examples include:

Automotive: Wheel bearing grease, CV joint grease, universal joint grease, fan clutch bearing grease, emission air pump grease, spark plug boot lubricant, weather stripping lubricant, sunroof seal lubricant, clutch throw out bearing grease, ABS system grease, paint plant conveyor bearings, paint spray system valve lubrication, gasoline pump bearings, windshield wiper motors, oil pressure sensors, truck window lift mechanism, sintered bearings in motors, leather seats, consoles and trim, flocked and unflocked window seals and channels, door handles, switches, air vents, controls

Aviation: Fuel resistant grease, oxygen compatible grease, ventilation fan bearing grease, cruise missile rear main bearing lubricant, starter bearing grease, emergency generator bearing grease, missile launch
platform gear lubricant, space shuttle lubricant, sealant

The standard grease consistency is NLGI grade 2 penetration (265?295). Softer or harder NLGI penetration grades can be made by special order.

Krytox lubricants will not carbonize or form gummy deposits that typically cause failures, nor will they evaporate. Therefore, maintenance costs can be significantly reduced.

Grease here is not the problem. Just about any grease will work. A moly waterproof grease is probably best. Takeaway is that the thing needs to be disassembled.

The pawl is subject to wear and needs to be replaced often. It is cheap, around $7. When the pawl gets worn the tail wheel will kick out and you will lose steering at the most inopportune time. Don't ask how I know this.

swjohnsey said:

Grease here is not the problem. Just about any grease will work. A moly waterproof grease is probably best. Takeaway is that the thing needs to be disassembled.

The pawl is subject to wear and needs to be replaced often. It is cheap, around $7. When the pawl gets worn the tail wheel will kick out and you will lose steering at the most inopportune time. Don't ask how I know this.

Click to expand...

+1. None of the popular tailwheels have a seal at the top of the shaft, so they all collect dirt and grit in the area of the "tombstone" pin. Regular cleaning is the hot ticket.

https://www.danhorton.net/Articles/1013_TailWheelTuneUp.pd.pdf

swjohnsey said:

Grease here is not the problem. Just about any grease will work. A moly waterproof grease is probably best. Takeaway is that the thing needs to be disassembled.

The pawl is subject to wear and needs to be replaced often. It is cheap, around $7. When the pawl gets worn the tail wheel will kick out and you will lose steering at the most inopportune time. Don't ask how I know this.

Click to expand...

The pawl is certainly easy to replace. However, the original pawl is still in my 1999 RV-6. The key to good service is to make sure no burrs have formed on the pawl. A light filing of the long edges of the pawl to prevent it sticking in the bore, cleaning and grease will keep the pawl functioning properly for a very long time.

Lock Pin

Sam Buchanan said:

The pawl is certainly easy to replace. However, the original pawl is still in my 1999 RV-6. The key to good service is to make sure no burrs have formed on the pawl. A light filing of the long edges of the pawl to prevent it sticking in the bore, cleaning and grease will keep the pawl functioning properly for a very long time.

Click to expand...

I second this. I've replaced my pin once in 900 hours and mostly because I was worried about it eventually breaking from fatigue which happened to a Harmon Rocket guy I knew. I disassemble, clean, and re-lube my tail wheel assembly 1-2 times per year. After I disassemble the fork from the gooseneck, I clean everything with coleman fuel. I then check the pin for burrs and usually kiss the edges of it on a scotch-brite wheel. I also check to make sure no burrs have formed around the edges of the broached pin-bore in the fork and file as needed. Finally I grease the fork assembly BELOW the locking pin bore and use LPS-1 on the pin, spring and steeering arm when I reassemble it. I try to keep grease away from the pin and use dry-lube here because grease in this area can trap grit and cause to pin to stick in the disengaged position.

Issues with the locking pin disengaging too easily are most likely due to rounding of the corners of the "notch" in the steering arm.

One other note: When I built my -8, I found that the washer that sits on top of the steering arm was resting on the root radius of the threaded portion of the fork assembly which resulted in a lot of end-play of the arm. I cut a chamfer on the ID of the washer which allows it to sit down flat against the step on the steering for shaft.

Skylor

The pin is softer than the notch. The pin new as a squared off profile, the folks who make it call it "bull nosed". After some wear it is more rounded. The old pin looks fine until you compare it to a new one.