Breaking in new engine. run ?

Remember the manuals info includes variable pitched props too. Countries around the world may allow variable pitched props for light aircraft, but in the USA LSA aircraft can't have them. So you need to consider that. Do you have a solid fixed pitch prop vs a ground adjustable prop vs a variable pitched prop, ect.... What are your flight needs, ect... What did your aircraft MFG set the pitch at if it's a factory built craft. With a ground adjustable prop some owners take off on short fields and need to climb over obstructions. This owner may need a better climb prop. Someone with an amphibian may have the need for a better climb prop. Owners on a more standard and longer field and no need for a special climb prop can balance out climb vs cruise. 5600-5650 rpm is only 150 - 200 rpm lower. Several aircraft MFG's only set their props to get 5500 rpm at WOT in level flight (like Vans RV12) and that's not tailored for that owners average flight altitude. Some pilots at sea level may rarely get over 2K ft and someone else in Colorado in the USA may always be at 10K ft.

What I see the huge majority report at take off is 5000 - 5100 with a ground adjustable prop.

I did a 14 prop research project years ago with all types of props with four identical planes that took off side by side and flew next to each other for real time comparisons. It took months of work. Things aren't as cut and dry as you may think as far as one rpm / prop pitch fits all.  Just like engine temps and pressures there is a range for the rpm and it's not a specific fixed number for all props, flight characteristics or personal needs (i.e. better climb vs balanced climb and cruise). Most pilots need and want a well balanced prop pitch that contributes to their flight needs and for less stress on the engine. For instance anything under 5500 WOT in level flight is over pitched and you lose climb, cruise, higher engine temps, more fuel use and more stress on the engine.

Prop pitch is not necessarily a one size fits all and your flight needs and plane may need some variance to perform at its best. The difference in prop pitch is small, but makes a difference.

Operators Manual, Chapter 5, Page 5, Figure 4, Performance Graph - Max Torque 5200 rpm

I am unable to find the specific instructions, I used for the propeller pitch setting on my last aircraft, however the above graph shows the performance of the engine. As with all internal combustion engines, operation below max torque is ill-advised, especially when the engine is "under load" (TO/Climb).

By allowing the engine to achieve max 5800 rpm at WOT your engine will be operating above (on the curve) for max torque - as you rotate for Climb the demand on the engine increase, engine speed decreases, however torque rises, increasing the ability of the engine to perform. If the engine speed falls below (or fails to achieve) max torque there will be a rapid reduction in performance and a marked increase in the stress on the engine.

In application, this means that if you set your static rpm below 5200 rpm, on application of full throttle (WOT),  the aircraft will start its TO role slowly, the ground run will be extended, as the engine struggles to achieve a higher rpm. Maximum rpm (5800) may not be reached, so best Climb performance may also be compromised - there may be a negative impact on terrain clearance. If the aircraft is heavily loaded, operating from grass runway, or operating in elevated density altitude, you would expect reduced performance - this may be further exacerbated by a low static setting.

Some examples from EProps:

1- SAVANNAH ultralight with ROTAX 912s engine (100hp) reducer 2,43 Propeller : Durandal 100 L diameter 180 cm Use : flights in mountain, very short runways Propeller adjustment : pitch = 5800 RPM, full throttle, horizontal flight With this pitch, during take-off, the engine RPM is 5700 RPM, with allows a very short take-off.

2- JMB AIRCRAFT VL3 with ROTAX 912s engine (100hp) reducer 2,43 Propeller : Durandal 100 M diameter 170 cm Use : long navigations Propeller adjustment : pitch = 5500 RPM, full throttle, horizontal flight With this pitch, during take-off, the engine RPM is also 5500 RPM. The cruise flight is fast and comfortable. The performances at take-off are still very good (even as good as with a variable pitch propeller) due to the ESR effect of the E-Props propeller.

3- AUTOGYRO MTO Sport with ROTAX 914 engine (115hp) reducer 2,43 Propeller : Excalibur-6 diameter 172 cm Use : local flights, navigations Propeller adjustment : pitch = 5800 RPM, full throttle, horizontal flight With this pitch, during take-off, the engine RPM is 5800 RPM, with allows a very short take-off and a very good climb rate

Carlos,

SL-912-016R1, para 3.1.2 for the source of the 5,200 minimum static rpm.

Charles,

Be advised if you set your WOT static rpm to 4,700 as Roger advises (I think that’s what he meant? Some of his subsequent language about a sweet spot I’m not sure if he meant at cruise or takeoff) your takeoff will be with your engine developing significantly less than maximum rated takeoff power. Somewhere around 65% of maximum or so.  And that’s under “standard” atmospheric conditions. This is a potentially hazardous situation. Should you choose to do this, ensure you are lightly loaded, have a long runway, a low Density Altitude, and no obstacles in your departure path for a few miles. Does your aircraft have performance charts? If so I recommend you set your static rpm pitch at WOT to the rpm listed in the appropriate performance chart for the conditions of your aircraft and home field Density Altitude.

Your field altitude and your AVERAGE FLIGHT ALTITUDE may be totally different and these must be taken into consideration when setting prop pitch.

Static rpm only gets you in the ballpark and you need to go fly it after that at your average altitude to be able to dial in the final WOT rpm. Static rpm on the ground may be only at 2400', but your flying altitude may be 8K'. Prop pitch set for 2K' altitude like someone from an airport at sea level will be different from someone who flies from an 7K' airport and is always up around 10K.

If you don't believe there is a prop pitch difference then try it. I've done hundreds of props over 30 years and major prop test that even the prop Mfg's said had never been done.

4700 static rpm set at the ground is just a ballpark number to get you started. 2 & 3 blade props and other variables will figure in. I've seen 2 blades set at 4700 and then on a flight they went over 5800 WOT in air. Then some 3 blades set at 4700 put them pretty close to the 5600 rpm in level flight. All this said is that your average flight altitude is important for setting a ground adjustable prop. I demonstrated this flying over the Grand Canyon in the USA over 8 years at a major fly-in with many pilots and planes when their pitch was set too course for that altitude.

The sweet spot I mentioned is a well balanced prop pitch for climb, cruise, engine temps, fuel economy and relieving engine stress. It isn't just about one thing.This sweet spot rpm of 5600 - 5650 needs to be set for level flight at WOT at your average altitude. It does no good to take off at a field that is only at 1500' above sea level and test it at 2500' when you usually fly at 8K above sea level. The air density is different. Yes we all fly higher and lower at times and that's not an issue. That's why I mention do it your average altitude.

If you set a prop pitch to only get 5500 WOT at 2K' then you'll be over pitched when you fly up at 8K - 10K and the engine will suffer and so will speed, climb and fuel economy. Your rpm at 10K WOT may only be 5100 rpm.

There's no guess work here. It's all science backed and tested.

I have friends with a Flight Design CTSW and LS that have a correctly set pitch for a 912ULS and have been up to 20K. Yes it's cold and you need oxygen and the climb is slow, but it will get there.

Thanks Roger, good information. Cruise is where most aircraft spend most of their time. It’s also the lowest risk phase of flight for most pilots most of the time. Takeoffs on the other hand…

I tend to focus on climb performance safety but that’s because of my particular “mission” and the fact that I fly with the 80hp engine- and I rarely have all 80 available. According to Rotax I will never have all 80 as I don’t have the tuned air intake box. Anyway if Charles starts his takeoff at gross weight on a typical hot summer day in Texas (let’s use a DA of 2,700’) at 4,700 rpm WOT, according to the performance graph on p.5-7 in the OM his 100hp engine will be only be delivering about 62hp to the prop. I don’t know how much Excess Thrust Horsepower his airplane needs to climb. At 5,500 takeoff rpm he would deliver an additional 10hp to the prop, I’m speculating that all of that would be ETH and available for climb performance, but only he would know. It certainly would be in my little Zenith.  Hopefully he has this data, or if not, will calculate what power his aircraft requires to maintain level flight- then he will know how much is available for climb- under various weights and DAs before his first flight and generate his own performance charts specific to his aircraft as I did. It’s not a guess, it’s a fact that aircraft climb performance will be significantly degraded under those circumstances. 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.