Breaking in new engine. run ?

"Just my opinion, but it would be safer to start his pitch adjustment journey at 5,500 WOT static and make small pitch adjustments to lower takeoff rpm after he’s comfortable the aircraft will perform safely."

Just my opinion - start at WOT 5200 RPM  STATIC and then make whatever adjustments seem appropriate to the aircraft type & mission.

When I did my prop research project 4700 was very close to all the 3 blade props and 4500-4600 was close for two blades. This isn't an exact number and is why after static is set you need to flight so it can be fine tuned for your specific needs and altitude. This is just like doing a mechanical sync on the carbs. It only gets you in the ballpark then you must do a pneumatic sync to do a final adjustment. As people have stated that altitude and density altitude play a part. This is why you set the final pitch at your average altitude. The higher we go the HP and torque start to drop. At 10K you could loose approximately 30% performance. and can be worse if you add prop over pitching to the equation.This is why we want to unload the prop (over 5500 WOT) so we keep some of that HP and torque and if we leave it over pitched you're stressing the engine and loosing all the good things that releasing this stress gives us.

Most of the LSA aircraft that come to me for maint. have a static right around that 4700 and some a little higher. When I set a few two blade props at 4700 WOT static rpm like the three blades that put me over 5800 WOT in level flight. Each prop may be a little different and that's why we must fly it for it's final setting. 4700-4800 static should put you right around 5000 - 5100 at take off.

Thanks a lot to all of you for taking the time and for sharing your knowledge and experience! Big thanks!

Hi Roger,

"Each prop may be a little different and that's why we must fly it for it's final setting. 4700-4800 static should put you right around 5000 - 5100 at take off."

Sorry to be a pain in the nether regions BUT I was always taught that when you want to operate an engine under load (TO & CO)  you should be above MAX torque so that any increase in load (sudden need to avoider an obstacle or just rotating for CO) would be accommodated by a rise in torque as rpm reduced. 

If you agree with above then the Rotax 912 pilot should be looking for well above 5200 rpm (max torque) during ground roll and in CO.

There seems to be some sort of reluctance to throttle back in cruise why? This drive to fly at WOT makes no real sense to me, unless its a particularly speedy airframe eg 150 knots.

Howdy Sean,

Pilots around the world seem to do different things depending on the type of aircraft they fly. So some of this has to be tailored into general terms.

Most I know have a take off rpm of 5000 - 5100. I personally don't know of anyone that flies at WOT in cruise and I personally don't know of any with a fixed pitch or ground adjustable prop that does. Setting the pitch to get 5650 is only 150 rpm below max and does not have a big and/or significant affect. During my flight test with those 14 props the difference was almost not even noticeable. Things would be different if we had variable pitched prop options for the LSA aircraft in the USA, but we don't. So we find a happy well balanced sweet spot since we can't make in flight adjustments. I have heard over the years that some do fly at max rpm of 5500 all the time with a ground adjustable prop.Normally WOT is for climb at take off or making sure we aren't over stressing the engine or just a max rpm check in level flight for a test or a climb somewhere during a flight. Everyone I know and that's hundreds of Rotax pilots fly around 5000 - 5300 rpm in level cruising flight. This seems to depend on what they fly. As many say the extra rpm above 5300 doesn't justify the additional fuel burn vs the small gain in speed. Yes some pilots use even lower and some higher depending on what they are flying. The whole idea for a WOT test in level flight at your average altitude is to only check what that WOT rpm really is and to make sure we aren't over pitched with WOT readings under 5500 rpm. When we set the WOT pitch in level cruise we are also more or less setting it for all other flight times too like climb out. Me I personally use 5200-5300 in cruise. My WOT rpm at my average altitude which is 6.5K' is 5600-5650. All planes rpms vary depending on whether. If it's winter with cooler more dense air or summer and hotter less dense air.