I understand that the propeller is not a constant speed propeller in either of these airplanes. What would a cruise RPM look like in the SR20 at 140KTAS and the SR22 160KTAS full throttle, lean of peak at say 8,000ft. What other cruise power settings are common…I’m a prospective owner. Always owned Bonanzas…Thanks
Thomas, this is getting a little confusing, you just asked a very similar question in another thread?
You cruise with the Cirrus at 2500 RPM. Typically at cruise altitude, you pull back from 2700 RPM until the MP drops and then advance the single power lever again to open the throttle completely (Wide Open Throttle, WOT). The upper inches of the single power lever are basically a prop. lever.
The new SR20 generations with the Lycoming 4 cylinder are not typically operated LOP, commonly flown 75% ROP. The Continental IO-360s typically cruise 65% peak EGT at 8000ft. With the SR 22 and Turbo versions it’s again different, but not RPM wise. Cruise is usually 2500 RPM.
Both SR20 and 22 have constant speed props. But as I just learned only the NA versions allow to control RPM. To understand, watch this:
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Thomas,
I see on your profile that your home airport is in Covington. Might I suggest that you take a day trip or a 2 day trip to JWN and reach out to Harmony Air. They have SR20s you can rent with continentals and lycoming. You can go up with an instructor and test the “skies” with one. You will got all the first hand experience and answers from a 2 hour flight.
Both these planes “self govern” so to say and they do have a constant speed prop. You just don’t control it. The cruise is typically around 2500 rpm. SR20s true out between 142-145 TAS.
It actually is, in both of those airplanes, as Brock described and as Robert’s embedded video explains.
I have always thought of WOT as full forward and never heard of the retard/advance technique.
So about 2650 rpm and 60% or so (13.5 gph) Been to 4 CPPP and only knew of 2500 on the T.
Am I running to high an RPM?
Maybe a little late with 1700 on hobbs : )
It’s not “wrong” but inefficient, like driving a car in a low gear. Actually there is an SPL endorsement, the single power lever is a little special.
The SPL is the same for all Cirri. It acts as a prop. and throttle lever. Full forward is 2700 RPM (prop. lever full forward) and WOT. Pulling back you first only reduce the RPM of the constant speed prop., like pulling the prop. lever back and leaving the throttle full forward, still WOT. The MP won’t change.
Once you reach 2500 RPM, the RPM will remain mostly constant and only the throttle is now being closed. You don’t want that in cruise typically, as you want all the air you can get in a NA engine. So once the MP drops, you push forward just a little until you have max. MP (WOT) at 2500 RPM, the most efficient configuration.
In a Lycoming SR20, you usually just pull back until you read 75% power and then lean to the ROP fuel flow indicated by the perspective avionics. In a Continental SR20, you pull to WOT at 2500 RPM and then lean to either a fuel flow ROP or LOP outside of the red fin of the engine (area of excessive ICPs). At typical cruise altitudes above 6000ft, your MP in a naturally aspirated engine usually is to low to create excessive ICPs, you can lean to peak EGT or slightly above, where you get max. power @2500 RPM WOT. It’s usually around 65% power. You can get a little more power by increasing the RPM to more than 2500 RPM, at higher fuel flow. The IAS increase is minimal compared to the higher fuel flow.
Hence many people cruise 65% 2500 RPM WOT peak EGT in the NA continental SR20s and they are more fuel efficient than the newer Lycoming engines that are supposed to be run rather at 75% power ROP. It makes them a little faster and Lycoming engines are designed for this mode of operation, which is good for Cirrus marketing.
I fly both our own SR20 G2 and a charter G6 (when our plane is not available for whatever reason). Typical cruise in the at lower altitudes is 145 kts TAS for the G6 at 12ish gph, the G3 is around 135 kts at 8.5ish gph LOP. At higher altitude, the G2 matches the speed of the G6 at peak EGT with 9.2ish gph (8000s) and the gph for peak EGT gets lower as you cruise higher. FL120 is more like 8.8ish gph.
The Lycoming Generation SR20 take the complexity of operating the engine LOP without damaging it an running it in the red fin away, running a ROP target fuel flow indicated by the avionics <= 75% (above 75% you don’t lean), at the cost of lower mpg. It’s a trade off. In SEP Helicopters, usually operating >=80% power, Lycoming engines are more common, flown full rich and actually designed to make it to TBO like that, the Continentals are more brittle and make TBO more like at 65%.
That’s not correct either. You CAN control the RPM between 2700-2500 at WOT (NA)… and only if you pack further you also reduce the power.
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This is not a true statement. The SR22T does not have a propeller cable attached to the throttle at all. The governor is set to 2500 RPM by mechanic and stays in that position.
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You take off with 2500 RPM in an SR22T?
In my Bonanzas I like to cruise at WOT, lean of peak and 2350rpm. These posts seem to suggest that you can’t cruise at 2350 or 2400 rpm. If that is incorrect, how do you achieve this slower prop speed (quieter I would assume) and maintain 160KTAS (Cirrus 22) or 140KTAS (Cirrus 20). So, what is the range of cruise RPMs in either model and how much cruise airspeed do you lose at a lower RPM. In a nutshell, what is the RPM control range and what will the speed cost be. As you can see, I’m all about noise reduction.
Yea
That is where the limit is set on the governor. 100% pwr, approx 36” depending on the day, and 2500 rpm. The “T” has a lower compression ratio allowing this power setting.
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As we Germans say, again what learned 