Goose-step?

[Splinter]

Ok heres the problem..... on a recent trip one of the Manne van Staal experienced a few violent "Goose-Steps" on three diffirent landings. All three the landings were on tar with a slight crosswind, no other strip available. The goose-step happens on the grass as well but it is less violent because the grass in more forgiving. The plane is a Cobra 912.

What we have checked is the following.....
1) Front wheel. No play anywhere (steering) on the front wheel but we did find the preasure to be a bit low and inflated the tyre
2) Front fork. Also no play to be found and shocks are working as normal.
3) Rear suspension checked on both sides, working just fine. No play on shocks, wheels or suspension mountings.
4) Wheel alignment. Rear wheels are slightly toe in. According to the manufacturer this is how it should be. Any comments?
5) Pilot landing technique? Pilot has 1000+ hours experience and flies in "bad wx" frequently. Had the landings checked in crosswind conditions to see if he is doing something wrong. Instructor found nothing unusual.
6) Trike going to manufacturer to inspect the bushes on the hangblock and pylon assembly to see if the movement on the wing is bigger than it should be.

Does anyone have some more suggestions on this matter?

Regards
Splinter

[Tumbleweed]

Since no one else wants a go;

You should only be able to goose walk by landing on either back wheel first, causing the wobble.
Have you checked for structural movement on the trike frame?

Otherwise, have each of you take turns landing to elliminate bad technique.

Carefull that prop.

[KFA]

With all of the above covered I want to suggest that :
- Landing speed to high
- Not pulling the bar back on touchdown to set the tyres firmly on the tar. When you half landed and and half flying trying to do that perfect greaser it usually happens especially in a x wind. You have to plonk it down more firmly and keep those knees locked.

my 2c

[Splinter]

Since no one else wants a go;

You should only be able to goose walk by landing on either back wheel first, causing the wobble.
Have you checked for structural movement on the trike frame?

Otherwise, have each of you take turns landing to elliminate bad technique.

Carefull that prop.

That was the 1st thought, that it could be the landing technique but there was a twist. He flew the trike while I was standing at the midway holding-point to watch the landing in front of me. Perfect landing followed by a violent goose-step. Took off again after regaining controll of the trike and came in for a second landing. Again perfect touch down but this time the goose-step did not happen immediately, it only started after rolling on the runway for about 30m after the point of touch-down. No brakes were applied during the slow down run. Thats why i`m leaning towards something on the trike. If the goose-step was caused by landing technique it would start Immediately after touch-down and not 30m down the runway? Is this assumption correct?

[Jetman]

Hi Splinter

I 100% agree with KFA. There can be a couple of reasons.... Just try this one thing. Pull bar back into chest as soon as wheels touches the ground and WHALLA. I had the same problem a while ago. Speculating here and there. Then a friend gave me this hint and problem solved.

Cheers Skin

[Chris Liebenberg]

I bet this guy pumped his tyres nice and hard just before the trip.

This goose-step thing happened to me as well, and the reason was that my tyres were inflated to more than 1 bar.

I found my problem after reading an article in a Microlight magazine of many moons ago, where the same thing happened to the author, and after he experimented with tyre pressure, eliminated goose-step completely.

It also worked for me.

Regards

[German]

Agree tyres to hard.Not more than 0.8bar!

[Splinter]

I bet this guy pumped his tyres nice and hard just before the trip.

This goose-step thing happened to me as well, and the reason was that my tyres were inflated to more than 1 bar.

I found my problem after reading an article in a Microlight magazine of many moons ago, where the same thing happened to the author, and after he experimented with tyre pressure, eliminated goose-step completely.

It also worked for me.

Regards

Hi Chiris

Unfortunately this is not the problem. The tyre was at 0.5 bar (to low) when returning from the trip after all the goose-steps. I inflated the tyre to exactly 0.8 knowing this can also be a problem. After that my father flew the trike again with me at the midway holding point. Made no difference, still doing a goose-step on two consecutive landings!

Skin I will ask Big Man to try pulling in the bar (if he is not doing it already) like you and KFA suggested and see if this changes things!
Trike going in to Rainbow today to have everything checked!

Will keep you updated

Splinter

[Bayliner]

Please excuse my ignorance but I have to ask. What is a goose step?

[Bayliner]

And of course any dangers to self and aircraft. Is this perhaps something that should be pointed out during training?

[Splinter]

Please excuse my ignorance but I have to ask. What is a goose step?

Imagine this. When you are landing and the front wheel touches down it starts swerving from left to right accross the runway. It is so violent that you can almost not controll the front wheel. The swerving in turn causes the rear wheels to take turns lifting of the ground and then banging back down again. Thes happens numerous times. a "Goose-Step" mimics a goose or duck running on water.

Dangers: You can roll the plane causing sinificant damage and possible serious injury to the pilot.

[bryan]

Hullo Ruan
I presume this has suddenly started happening. If so then obviously something has changed on the aircraft. If not it can be something you are doing differently on landing over a period of time and you may not have noticed. I hope you find the problem soon since it can become a pain in the arse literally and figuratively.
Fly safe
Regards
Bryan
ZU BFR

[Conrad]

Just a thought !
Are both back wheels free running,
Could it be that one back wheel breaks a bit on landing?
I would check the front wheel option last.

Please remember to tell us what the outcome is.

[Splinter]

Hullo Ruan
I presume this has suddenly started happening. If so then obviously something has changed on the aircraft. If not it can be something you are doing differently on landing over a period of time and you may not have noticed. I hope you find the problem soon since it can become a pain in the arse literally and figuratively.
Fly safe
Regards
Bryan
ZU BFR

Hello Bryan.

Die probleem is op my pa se vliegtuig nie myne nie. Ons sal die naweek nog n paar dinge probeer en kyk wat gebeur. Het nog nie kans gehad om die Cobra self te gaan vlieg na die probleem begin het nie maar sal dit die naweek tyd maak en terugvoer gee.

Sal bietjie kyk na die Conrad se voorstel ook.

Thanx manne

[Sukkelaar]

Check the wheel bearings under load, i sugest towing the aircraft with a vehicle while someone sits in it for load, on a smooth surface, and then you might be able to hear them without the deafening noise of the aircraft motor.

Or maybe a dead stick landing on a smooth surface, without a helmut to hear the wheels turning at speed with weight on them.

Regards