Prop off thruster

[frankmcm]

Last week I helped a friend retrieve his thruster from a field. Prop separated at 2300 rpm as he was climbing to join the circuit. He was fortunate to walk away, but wrote off the thruster. This is the second such event at our airfield with this combination of jab 2200 & composite prop. Sheared the bolts connecting the prop boss to crank i believe. I am sticking with wooden blades henceforth.

 

 

[fly_tornado]

At least your friend walked away unhurt.

 

 

[Riley]

Could you provide some elaboration regarding which specific Thruster was involved and also the flying history of the failed components (would like to know if it was one of the UK Vision 600's or one of the few local T-300's that were retro-fitted with Jab 2200 engines)? Not intending to bring the propellor into disrepute but would also be interested to learn the prop type, size, nr of blades etc etc. Were the problems your mate faced a 'carbon copy' of the initial similar failure?. We all can learn from this. tks n rgds

 

 

[jetjr]

Carbon props on 2200 engines have a history of failure, too stiff, too much vibration. Hence why Jabiru Aust only approve wooden props. Might be about to change though.

 

3300 is Ok

 

Most Ive heard of have been blade or hub failures, this seems different being bolts. Plenty to check there, type, age, torque, etcetcetc

 

 

[frankmcm]

Lets see if I can post some graphics. Advise if this doesnt come through..

 

 

 

[frankmcm]

And again ...........

 

 

 

[Guernsey]

Heard on the grapevine that Bolly Props are now supplying Jabiru.

 

Alan.

 

 

[fly_tornado]

Are you 100% positive that the engine hasn't seized?

 

 

[frankmcm]

T600 I think . Not completely up to speed on all the details, but I believe that Jab UK mandated replacement of bolts every 500 hrs following the first event 2 years ago. GKYLE had the specified bolts changed, and the failed bolts were way short of 500 hours. I dont know what prop was involved, except that it was 2 bladed composite. Both events I understand were similar, no warning sudden departure of complete prop. Neither prop retrieved incidentally !

 

 

[Keenaviator]

The early Jab engines are absolutely not suitable to use with composite/carbon props. They had 1/4" grub screws on the fly wheel to crank. Later they increased the size to 5/16" (still not suitable for carbon prop), then they added dowels and later a steel 'spider' reinforcing plate. I updated the Jabiru engine in my (ex) Corby Starlet to one with all the mods so was able to fit a Patroney carbon ground adjustable prop which is still performing very nicely (correct me if I'm wrong Darren if you are watching!).

 

Cheers, Laurie

 

 

[jetjr]

They arent prop bolts which failed but main extension shaft bolts - serious bits of kit, fitted and "loctited" into place

 

Cant see too well but no corrosion on broken shafts so this has been a sudden breakage of the whole lot in my uneducated opinion.

 

2200 rely on the wooden prop to absorb inherant 4 cyl vibrations, if it isnt doing that then other components take the pain ie main shaft bolts on flywheel and prop ext shaft.

 

I heard some of the flywheel problems (and upgrades) were related to use of non factory extension shafts and props overseas. In the end it was seen some were made poorly adding to vibration problems. Also maybe why Jabiru are so strong on using wooden propellers.

 

Yes Bolly are making blades for Jabiru to Jabiru design. First models available soon. Very nice, increased performance Im told. Ground adjustable but pinned in place by Jabiru. Really not sure how these will go on 2200 for the above reasons.

 

After playing with wooden and CF props for some years Id strongly suggest getting your prop dynamically balanced, can remove most of the vibrations which damage props and engines - even those not related to the prop itself.

 

 

[Methusala]

The pictures are quite sad. A friend flys a Cygnet with an 1835cc VW. He installed his propeller using high tensile bolts which broke in flight. On the same day another aircraft with a pusher installation Rotax 477 had 3 out of 6 , again h/t prop bolts fail. Both aircraft were undamaged in the incidents. AN bolts are, I believe annealed to increase ductility. Perhaps the steel used in the failed components is below par? (Don't know what you could do about this.) Don

 

 

[frankmcm]

Are you 100% positive that the engine hasn't seized?

The LAME who inspected it just diagnosed bolt failure, seizure was not mentioned so I presumed it had been ruled out. it will be a few weeks before I talk with him again, and should it be an issue I can update. Meanwhile I expect that some thruster drivers will be looking hard at their bolts..