Nose "Worm gear" failure

Hi Cozybuilders and flyers,

I just got back from an interesting week of COZY-flying in Europe...For those who don't know me, I'm European (Belgian), but I live and work as an airline pilot in Dubai (United Arab Emirates). My little COZY3 is based in Belgium.

Enough said... Last Friday I did a short test-flight after some repairs on a leaking fuel indicator in the cabin. The flight went as planned, when joining the circuit, I lowered the nose-gear (manual system) and as a bit of of surprise, after the gear extended for about 2/3rds, the gear rachet kept on "free turning" without any resistance...Did a couple of resets, the gear would retract normally, but wouldn't extend in the full down and locked position. I have a green and red gear indicator installed and the unsafe condition was indicated with red ON and Green NOT LIT... Hmmmm!!!

Did a low pass over the tower and they confirmed that the gear was about in the 60° down position. As I seriously expected a gear collapse, I opted to land on the freshly mawn smooth grass strip and not on the 6000ft concrete runway.

Approched with minimum speed, (airbrake retracted), touchdowned smoothly and....after the nose gear contacted the grass...it collapsed, eating all of the other teeth! Stopped in about 100ft (30m). Spectacular!!! There is some damage to the nose-section and of course the "nose worm gear" is missing 1/3th of its teeth...Lucky enough the gear retracted nicely into the wheel well and didn't cause any damage overthere...

Regarding the above I have some question to you guys who might have lived the same thing...

* From time to time, I used to park my COZY with the nose in the half-retracted position. Did this weaken the tooth that finally broke off?

* How do you explain that the gear retracted normally, just after take-off...?

* Is my way of thinking correct that probably only a single tooth broke loose and that the rest was damaged after the landing?

* With what kind of worm gear would you replace my broken one? Yes, I know I can turn it 180°, but I would like to replace with a new one... A bronze one? Is this not worst...if you end up with a worm gear stronger than the worm itself...?

* The landing on the grass strip was smooth but caused lots of dust to enter the engine compartement. I changed the air-filter allready. The engine was shut down just before landing... Any specific things to check with the engine...?

* Do you think that landing on the smooth grass strip was a wise idea...? What kind of damage can I expect landing on a concrete runway?

* If I would have held the gear rachet with my right hand (during the landing), would this have stopped the lowering of the nose...?

* Any other bright ideas regarding the incident?

I removed the entire nose-gear system and will do the repair on the epoxy end of AUG. There seem to be a couple of cracks in the structure that will need to be repaired carefully. All of them are in the front section, left and right of the pitot, none of them are visible from inside (tru the removeable nose panel).

All help, is more than welcome,

Regards,

Cozylover,

BJORN

PS: I have some pics of the damamge, for those of you interested.

flybjorn@emirates.net.ae

Bjorn,

* From time to time, I used to park my COZY with the nose in the half-retracted position. Did this weaken the tooth that finally broke off?

> Probably. The gear teeth aren't strong enough to hold the strut extended. The over center linkage does all the work. The gear is strong enough to retract the strut, but not hold it down against any kind of load. I used to park my Long-EZ that way, but no more.

* How do you explain that the gear retracted normally, just after take-off...?

> Perhaps the aerodynamic drag helped push it across the broken tooth coming up and drag and retraction momentum were in the same direction.

* Is my way of thinking correct that probably only a single tooth broke loose and that the rest was damaged after the landing?

> That would be my guess.

* With what kind of worm gear would you replace my broken one? Yes, I know I can turn it 180°, but I would like to replace with a new one... A bronze one?

> Why not turn it over. It would probably last long enough for you to save enough pennies to buy an electric nose lift that is perfectly happy half retracted and you'll never have to lift the airplane off the groung again.

* Is this not worst...if you end up with a worm gear stronger than the worm itself...?

> Quite possibly. Which link in the chain do you want to be the weakest? Which gear would you prefer to change when it breaks?

* The landing on the grass strip was smooth but caused lots of dust to enter the engine compartement. I changed the air-filter allready. The engine was shut down just before landing... Any specific things to check with the engine...?

> I don't know. If the engine was stopped, just clean it off and be done with it. Besides the air cleaner, I would vacuum out the exhaust pipes and be done with it.

* Do you think that landing on the smooth grass strip was a wise idea...?

> You seem to have gotten through it OK with minimal damage to the airplane. I would probably have landed on hard surface where I know the only damage will be to the underside of the nose.

* What kind of damage can I expect landing on a concrete runway?

> Scuffed, scraped nose section. Do you not have the "hockey puck" under the nose for parking? That would be gone and some skin. Perhaps reinforce the hockey puck when you repair the rest of it.

* If I would have held the gear rachet with my right hand (during the landing), would this have stopped the lowering of the nose...?

> I seriously doubt it.

* Any other bright ideas regarding the incident?

> I've already told you more than I know

Thanks Jim for your reply!

To replace the worm gear (yes...I know I can turn it!), would you have one machined locally or go for the Brock one...? Remember I live in Europe...

Regards,

Cozylover,

Bjorn

As I said, I would go for one of the electric nose lifts available. If you are a member of Marc Zetlin's Cozy mail list you know all about them. If not, let me know and I'll help you join. You can surf the archives and find all the details. Basically, they replace the worm gear mechanism with an electric screw jack that has a hand crank backup. I believe it's about a 5-10 lb weight penalty over the Rutan system. It enables you to get into the airplane in the "grazing" position, start the engine, get all settled in, and then lower the nose gear/raise the nose and drive away.

My first choice all the way .... Jim S.

Jim,

Thanks for the quick reply.

Yes, I will probably change to the electric nose-lift at some stage. Unfortunately I don't have the time now, will do the nose repair and replace the gear in AUG. I live and work 6000miles!!!(yes) from where my COZY is based, so it doesn't make life easy...

And yes, I'm on Marc's www.

Thanks for all,

BJORN:)

<... at some stage. Unfortunately I don't have the time now...>

IIRC it bolts on through just about the same holes. In any event, if you flip your boston gear you will have a conventional setup until you DO get the time to convert to nose lift.

Hi Cozyflyers and builders,

On this post I explanied earlier (see above), what happened about a month ago on landing my COZY in Belgium....Nose gear collapse, due to Worm gear failure, etc...

I'm just about to start the body work repair on the nose of my bird. I'm not the builder and this is my first epôxy job ever on the aircraft.

Can somebody comment on the way of making the repairs...? I'll post a pic together with this post, in order to have an idea what the damage is like... Did a lot of reading on general composite stuff including the plans.

I'm especially interested in what kind of cloth to use...BID and/or UND for the nose section plus the orientation. Also please comment on anything that can make the job easier...

I'm a newbie with this, so please bear with me.

Looking forward to your comments,

Reagards,

Cozylover,

Bjorn

Sorry...apperently the promised pic did'nt come thru!

I'll try again!

Cozylover

Hi Bjorn,

From the picture it doesnt look as though anything has "shifted". It "looks" like you only have surface damage. Better check the inside carefully to look for any bent or cracked layups or joins. Look very carefully around the bulkheads to see if anything has broken or moved. If the inside looks good I'd sand everything on the outside down to bare glass a couple of inches past the damage. Next remove any stray glass that's sticking up from the cracks. Fill any holes in the foam with dry micro, paint the border with epoxy, then layup 3 ply BID over the entire area extending at least one inch onto the undamaged glass. If the inside is damaged, then closer inspection will be needed to make sure nothing is compromised or misaligned. Personally I'd then cover the layup with 4ml clear plastic and squeege all the air and excess epoxy out of the sides of the layup, but thats my favorite technique and might not work for you on the first try.

Once cured sand the edges for a smooth transition, and add a covering of very dry micro with a heat gun to help it stick. When the micro cures, sand with 50 grit to remove the bumps, then sand with 100 grit to get it smooth. You might need a few more applications of dry micro before you have a nice finish ready to prime and paint.

I hope this helps.

Regards,

John

Hi John,

Thanks for the nice explanation! It certainly helps...

Do you make the "dry micro" yourself or do you use one of the so called filler products?

I'm planning to have a proffesional car-painter do the paint job...he will probably know how to finish as well I hope...

Thanks again John,

Regards,

BJORN

PS: Any other Canardiens ar emore than welcome to comment on the above!

>Do you make the "dry micro" yourself

Yes. Get the epoxy hot (110 F) and mix in as much micro as you can, then a bit more until it becomes a little flakey. Stick it on with a sheetrock putty knife and a heat gun looking for full coverage rather a smooth finish, then rub it smooth after cure.

>I'm planning to have a proffesional car-painter do the paint >job...he will probably know how to finish as well I hope...

He'll know how to finsh an automobile, but he'll probably want to use bondo or some other filler that will shrink and may come off in chuncks. I'd recommend doing the filling yourself.