Props, Props and more Props

Dear Gregg,

I had an 912 UL 80 hp engine manufactured 2005. The crankshaft housing, especially the bearing shells, looked the same as in your pictures.After running while the engine was hot the propeller blocked, after cooling down the engine runs well.The reason, like Roger wrote, there where construction faults from ROTAX at the crankcase. Rotax changes the crankcase maybe 2007/2008.

No chance to get from ROTAX the korrekt answers, no appologies about this. From ROTAX you get the information, its a pilots problem and the pilot/manufacturer of the airplane/the propelller ... are the reason. They spreaded the information the engine was unter to high load, esp. by a to high propeller pitch. Its right, to high pitch leads to a lower WOT by a high stress at the crank shaft, esp lateral loads on the bearing shells.

But in my oppinion the crankcase was not constructed well. So set the propeller pitch that you can reach at WOT in flight approx 5400 to 5600 rev. Nobody flyies permantently with WOT so at 75% you have approx. 4900 to 5000 rec. thats OK.

So in my oppinion your problem is not the propeller. First it was the crakcase. Maybe you had to much pitch at the propeller but you can adjust it (high propeller load can lead to reduce the service time - my 912 UL had 1700h by WOT 5000 in flight and 4800 at launch - now i reduced the pitch). Yes inappropriate setting of the propeller can damage the engine in future but Its no a question which propeller brand harms the engine if the propeller fits to your aircraft and adjusted well. I know there are differences between propeller brands but by appropiat settings every propeller works.

Greetings

@Roger

I have been reading through this thread with interest.  I have a Bristell NG5 with a Fiti In Flight Adjustable prop and it has just gone TBO.  They only give them 6 years.  :(

So I now have a choice - Replace it with another In Flight Adjustable Fiti (about $7000AUD) or look at an alternative - Possibly ground adjustable.

So my questions is - seeing how this thread was started some time ago, is the advice any different?

Cheers

John

Roger at Zenith said the sensenich ground adjustable is a night and day difference going from a warp drive to a sensenich prop. Better everything, would you agree? CH 701 rotax 912 ul with edge performance 100 HP upgrade.

John Fleming wrote:

@Roger

I have been reading through this thread with interest.  I have a Bristell NG5 with a Fiti In Flight Adjustable prop and it has just gone TBO.  They only give them 6 years.  :(

So I now have a choice - Replace it with another In Flight Adjustable Fiti (about $7000AUD) or look at an alternative - Possibly ground adjustable.

So my questions is - seeing how this thread was started some time ago, is the advice any different?

Cheers

John

I doubt that you have to replace the Fiti  IFA -

The advice is to return to factory for an inspection. Should the inspection find a problem, the action will vary from replace part, through to replace prop. If the prop is still in good condition its unlikely replacement will be the outcome.

The Fiti advice on prop TBO is very conservative - I flew one (19 aircraft) for over 10 years with no sign of an issue (I never sent it back to Fiti either).