WARNING #2 (DLE engines)

[Phil Clark]

Following on from Keith's warning over multi bolt fixings on DLE engines.......I thought I should highlight this issue found on a customers DLE 111 this week (model with me for some work, I have never run or owned a DLE so this isn't specifically from personal experience)

See attached photo & note the large crack in the aluminium prop driver.

Worrying I agree, but I think there is a specific cause to this.

The prop was badly crushed in the centre (back & front) showing over tightening. In addition, a large aluminium spinner was fitted (machined type, not spun) and the back plate was badly dished (4-5mm out of 'flat' in the centre. This dishing was due to over tightening of the centre spinner bolt. There was no 'spacer' fitted between the front of the crank shaft and the inside of the spinner cone to prevent this. All forces were going back to the back plate......the more the spinner was tightened, the more it dished the back plate.

This spinner over tightening is the cause of the prop driver failure.......the over tight spinner bolt causing rearward force on the back plate/prop driver so pushing the prop driver harder & harder onto the taper on the crankshaft......eventually causing the failure.

I have to admit, I'm a little suspicious of 'Chinese cheese' metalurgy.......but this is still a very worrying failure all the same.

Phil

[Alan Cantwell 1131]

Phil, when you have got it off, could you send it to me? i would like to machine it, and see just what sort of ally it is,

[Paul Savage 1568]

I had a brand new dle 111 a couple of years ago fitted to a Pitts 12. The driver went exactly the same as the one in the photo on only the first flight and also managed to sheer all but 2 allen srews in the process. In fairness, the prop had been fitted for a few months prior to the first flight, so pre flight and then periodic checking for correct propeller fitment would probably have prevented this.

[Phil Clark]

Phil, when you have got it off, could you send it to me? i would like to machine it, and see just what sort of ally it is,

Hi Alan

The model (Bill Hemple 40% Cub) was with me for a new cowl, hence wasn't in the workshop very long, I only spotted the problem the day before the customer collected the model, hence it's already back down in Lincolnshire. I can put you in contact with him if required................

Phil

[Alan Cantwell 1131]

please Phil, he may not want to spend the money on post, but it will be usefull research

[Phil Clark]

please Phil, he may not want to spend the money on post, but it will be usefull research

Spoken with the owner and he'll get the driver to me ASAP.

He's also informed me of another possible cause of the damage.....apparantly he sheared a woodruff key a while back following a backfire trying to start it. He didn't spot anything at the time, but maybe this initiated the crack?

Phil

[david clarke]

I had exactly the same problem,bought a brand new unrun DL100 and found a crack through the prop driver,i replaced it with a new one for a DLE111 totally put me off the engine so i got rid.

Dave.