Lost it

[Yenn]

I was doing a first flight test today of a friends D18 Jodel.

 

I lost it completely, left the runway on both sides, missing lights and the Vasis by very little. No damage to the plane and only my ego suffered.

 

It was a bit squirrely on taxi at slow speeds, but not enough to alarm me.

 

I started a high speed run with the intention of flying if I was happy. I lifted the tail fairly early in the run and and it was difficult to keep straight. So much so that I took off to get myself sorted out. Not bad in the air, so at about 50' I cut the power and landed. Not a bad landing, 3 point and then the fun started. I was all over the place, with not enough rudder to straighten it up.

 

Being stupid I then did another run in the opposite direction and lost it again, but didn't take off.

 

Wind was very light crosswind 2kts at most and no other traffic in the area.

 

What went wrong?

 

Maybe I got my feet tangled up in the heel brakes. I hope that is the reason. Maybe there is a problem with the plane, but it was thoroughly checked before and after the flight. I know it was an interesting few minutes and my only fear was that I was going to bend the plane.

 

Any Jodel experts out there to help explain?

 

 

[winsor68]

:blush:Did you need a change of jocks after?

 

 

[turboplanner]

Ah, Yenn at last - you're just like us!

 

 

[Barefootpilot]

Have a look at the toe in/toe out on the wheels that can have a huge effect on the controlablity and might be worth checking the tracking aswell. (I'm not expert but that would be my first things to start looking at)

 

 

[Skyhog]

What is the steering link to the tailwheel?There are a few different tailwheel steering mechanisms as we all know,ranging from bungees/springs to castoring/partially castoring.To fly a Thruster it is generally taught to get the tail up ASAP on takeoff as you would be aware Yenn.On some other aircraft such as the Citabria (and maybe the D18) it is recommended not to rush the transition to get the tailwheel off the ground.It sounds a bit like it was hard to control in the 3 point attitude with the tailwheel on the ground,suggesting that the tailwheel may not be aligned with the rudder.Think about if you were happily rolling with the tailwheel on the ground as your steering control and it was 10 degrees different angle to the rudder,then suddenly you lifted it off the ground,there would have to be a drastic change.If you combine this with the torque and slipstream effects as well,it may be quite significant.I could also suggest (as I once did in my Thruster),that you were not paying enough attention with your feet.I didn't groundloop but left the runway.You have probably thought of all these angles but I'm just trying to enlighten other readers of the many variables.

 

 

[Yenn]

Oh dear, did I give the impression I was different?

 

It seems the probable cause is wheel alignment, which I wil pursue.

 

With it not being my plane I only did the usual checks prior to flying. Will talk to the owner again as one of my local friends came up with the same solution.

 

 

[turboplanner]

I'd bone up on weight and balance, control surface alignments, binding and anything else which would destabilise the ac, and check it slowly item by item. Better than hairing down the strip knowing you may not have found the cause and not being so lucky next time.

 

This might sound silly but a trip to the local model ac field may help. The top guys there are experts at fixing unstable aircraft built by people like me, and may be able to pick the problem from the symptoms

 

 

[bushcaddy105]

Gooday Yenn

 

Having helped out before with this problem, may I suggest that you check the mechanical advantage between the rudder and the tailwheel. The principle is that for any given amount of rudder pedal movement, the tailwheel should move through a larger deflection angle from straight ahead than the rudder, assuming that there is little, if any, free play in the tailwheel linkage.

 

This ensures that there is more direction control on the ground by the tailwheel than by the rudder as the rollout commences. In the air, this uneven deflection is of no significance.

 

In practice, where the tailwheel is operated by spring links back from the rudder, it requires the lever length (measured from the aircraft centreline) to be longer on the rudder than on the tailwheel assembly. I'll attempt to post a photo to illustrate the above.

 

Hope this helps

 

 

 

 

[vk3awa]

I agree with Adam. Very important to check wheel alignment with the emphasis on toe in/out. You did mention it was hard to keep directional control with the tail up.

 

I had a similar issue with my jabiru taildragger until I aligned the mains.

 

Cheers

 

Daryl

 

 

[farri]

Yen,

 

I`m sure you know by now that everyone you walk away from is a good one.;)

 

Frank.

 

 

[rick-p]

Hi Yenn,

 

Did you sort the problem?

 

I would at a pinch also go with wheel alignment.

 

I had an incident occur a few years ago in the Skyfox.

 

I was doing a fast taxi up to the other end of the strip and as I slowed down a bit the old girl started to ground loop.

 

This was a first for me as I had never ground looped in a Skyfox previously despite all the fan fair from the experts that it was a very easy plane to ground loop.

 

It really did take me by supprise as nothing I did to stop it worked.

 

Thank God my strip is very wide from fence to fence.

 

Anyway the end result was that I came to rest with one of the main gear wheels resting right in the middle of one of the tyres I use as a marker on the strip.

 

Well you can't imagine the difficulty I had in lifting the old girl on my own and trying to then move it over the tyre.

 

Please don't anyone say why didn't you taxi it out of the tyre, please think about what the end result would have been if I had have done that.

 

Anyway once the plane was out of the tyre I couldn't see anything wrong looking at it close up but I did what I always do and as I was taught to do by Greg McG that is when you do your pre flight always after your checks move away from the aircraft and look at the big picture.

 

As I said I did this and very quickly spotted the problem.

 

It was the wheel alignment.

 

A bungie hadn't broken but somehow on one side of it's attachment had slipped and slightly lengthened hence allowing that wheel's angle relative to the ground to be less thus altering the camber and efectively the wheel had less toe in.

 

This allowed the aircraft to ground loop to that side.

 

And of course,you guessed it it was on the near side so it was further effected by the weight of the pilot with no passenger to act as a counter weight on the farside.

 

Regards,

 

Rick-p

 

 

[facthunter]

Few Thoughts.

 

General comment . I think toe in makes the thing pretty sensitive but I don't claim to be expert here.

 

The jodel has a pretty small tail from memory. Use of brakes compounds directional problems and is not recommended in the Citabria handling notes. Heel brakes are more difficult to operate than toe brakes. The chipmunk system where the handbrake can be partly on and will cause the brake on the side that the rudder is applied to come on differentially works but it is a coarse application. Essentially steering by brake application is difficult to do and it is easy to overdo it and get into trouble.(Including putting it on its nose.)

 

Some higher performance british aircraft (T/W) prewar had directional pecularities caused by the rudder being too small or blanketted and the technique was to get the tailwheel on the ground early, ( means you have to touch-down slow) and keep it there by holding back stick, and rely on it rather than the rudder. For this to be a good method the tailwheel steering system has to be well designed and effective.

 

My comments about not using differential braking to steer are general and do not apply to when you have a flat tyre, or a rock jammed in the brake caliper etc. Nev.

 

 

[Yenn]

I havn't been back to the plane, had a bad back and a weekend away, also couldn't raise the owner by phone. I am guessing it will be a toe in problem and will probably fly into Gladstone tomorrow when the hangar might be open. It sure made me work hard for a while and a video would have been usefull. I am told the media were filming it all as a busload of them were at the airport at the time. Not game to ask them for a look as they would then start asking questions.

 

 

[kevinfrost]

Any info on the prang sth of Waikerie on the week end. One fatality I've heard.

 

 

[Jabiru Phil]

Lucky Graham

 

GRAHAM’S EMERGENCY LANDING

 

On the 23rd May, I destroyed my KR2 just south of Waikerie in an emergency landing. The engine failed at 1500’ and could not be restarted. There were not many options. Prior to the impact I activated my PLB and was located by the rescue helicopter that was sent up from Adelaide, which then airlifted me back to the RAH with minor injuries. I would like to thank those that helped on the day, those that retrieved what was left of the KR2, and those that have offered constructive support since. It is a lesson for all of us, that we should be current with our emergency procedures. Rgds Graham Strout

 

 

[facthunter]

response.

 

My sympathys Graham. We never know when it will happen to any of us I hope it will sort itself out for you. I appreciate your honesty regards Nev.

 

 

[kevinfrost]

Graham, I 2nd Nevs response and am glad the first report I heard was not 100% accurate........Regards Kevin.

 

 

[turboplanner]

Graham, any chaf running us through the sequence from when the engine cut?

 

We've all practiced forced landings with an engine idling, knowing we are going top lift off it turns sour and often with an instructor who helpfully guides us out of difficulty, but hearing about the real thing may help us manage to achieve what you did.

 

 

[Jabiru Phil]

Sorry Turbocharger. I printed what Grahame put in the Renmark news letter. I do not think that he is a member of this forum.

 

I will post more with his OK when I catch up in a week or so, hopefully.

 

Phil.

 

 

[rotor]

Hi all ....

 

bit late but adding to what's already been said. Without changing anything on the plane, it was successfully test flown without any ground problems at at all on take off or landing. Having said that the test pilot was a very very experienced tail dragger pilot.

 

Toe in Toe out - from memory the jodel plans advise this be nil - I should look again but during construction the tow in/out was as per the plans instructed.

 

I haven't done anything with the plane since that test flight - simply been to busy with work and family, but have got back into it this year and I'll be continuing and hopefully completing very soon.

 

I'll keep you posted on the ground handling - as I don't have as many hours as Yenn - but I have a couple of very good tail dragger pilots now to pass on their knowledge ....

 

Cheers

 

Geoff

 

 

[facthunter]

What hasn't been mentioned is the tailwheel itself. The centre of the wheel is behind the pivot point so it castors. With the wheel on the ground there is a tendency for the pivot to jamb on most setups, due to the offset load. Check that it is free and well lubricated. The spring can deflect too far also if it is not set right, and affect the way the wheel turns. It should be horizontal when the weight of the A/C is on it.

 

Your candidness is most refreshing Yenn. There must be something not right, if a person with your tailwheel experience has a problem with it. Nev

 

 

[rotor]

Nev,

 

The plane has a Matco 6" tailwheel assembly set up as it should be - no jamming here.

 

Before Yenn went out I did stipulate not to try doing fast ground runs and to keep the stick back and the tail wheel grounded. This was what I had been told by people that knew Jodels and their apparent bad ground handling characteristics. I put the whole episode down to bad preparation before the test run.

 

The consequent test flight was fine as far as ground handling went on take off and landing. I did ask the pilot about the ground handling to which he stated that the ground handling was fine.

 

Geoff

 

 

[geoffreywh]

I'll bet that there's no problem with the aeroplane, Just not quick enough with the feet.

 

 

[bones]

So you finally got the thing in the air did you??

 

Now i spose you finally get up here then :)

 

 

[Yenn]

G;Day Geoff

 

Welcome to this site. In retrospect I think what happened with that flight was caused by my wearing heavy shoes and getting mixed up with the heel brakes. My biggest fear was that I was going to bend your plane, never had any worries about my own safety. Obviously not a fault with the plane as Ronny flew it OK.

 

Now I have to get ready to first flight my RV4. I have ordered the engine and prop and the A$ is going up, so it is getting cheaper by the day.