I find the claims here completely unsuprising.
We've had a decade of claims by Cirrus Marketing of "operating simplicity" etc etc.
This company claims "Reduced fuel consumption, 1+ gallon per hour in cruise" which is best part of 10% (high altitude economy cruise). The thing is that anybody who is even remotely familiar with CS prop operation would have known that flying everywhere at max rated RPM is a big waste of fuel. How come it's taken 10 years?
The funniest bit would be if somebody one day gets an STC for a retractable gear mod, and finds that the plane goes another 15kt faster, with a 20kg loss of payload. Not likely of course, due to the impossible complexity of such a mod.
I have nothing against the aircraft. It's a very fine aircraft, and a great GA success story (one of the very few piston GA success stories of recent decades actually). I just never believed the marketing claims behind the removal of the prop RPM lever (while leaving behind the relatively much more complex to understand mixture lever).
And of course I don't believe in the fixed gear costing just a "few" knots, but this will never be settled 
I agree. However, the Cirrus is not cruising at max rated rpm, 2700, but at 2500. The final bit of lever travel towards full throttle increases rpm so that 2700 is available at full power. It does that via simple mechanical linking from the throttle lever to the prop governor. What I always wondered is why the linkage is not designed to reduce rpm gradually as power is reduced.
I miss the prop lever when flying Cirrus, for reasons of both fuel burn, vibrations and noise. However, I suspect that most Cirrus pilots do not. Many pilots of naturally aspirated singles fly for speed. They generally leave throttle and prop forward from takeoff to top of descent, managing only the mixture. For those, the Cirrus just have one lever less not to manage.
Other pilots with a prop lever set 2300 for cruise rpm as if that number was required by law. For those, the missing lever in a Cirrus is probably a welcome simplification, and the fuel penalty is not likely to be observed at all.
My observation as well: Cirrus pilots tend to pay less attention to the whole engine configuration issue because it is so simple at first sight. In a classical black/blue/red lever quadrant, you have to know more because there are infinite combinations of the levers and not all are allowed. A friend of mine with a SR20 (> 500h) doesn't even know much about the red lever, he just pulls it back a little bit (to the level of the "X" in "MIXTURE" which is written next to it as he explained to me). He doesn't know Vx and Vy either.
My cruise (TR182) is usually 23"/2100RPM which is very quiet and I often take off the headset during cruise. That's 65% BHP and gives the best mileage. With a Cirrus like mechanism such a power setting would not be available.
I also find it unsurprising, that a reduction in power and a reduction in speed leads to a reduction of fuel flow, thus leading to an increase in fuel efficiency.
In fact, looking in the Cirrus POH, the number you get for a corresponding reduction of power and speed are in a comparable ball park.
I find it quite interesting, that the company presents three tables from flights, were two of them are ROP, which is not in alignment with the Cirrus POH. And the single tabel in line with the POH, the LOP table, has a 0 to 100 scale for speed (therefore a 10% decrease looks like a 10% decrease), but a scale from 11 (not 0!) to 14 for the fuel efficiency, so a (claimed) 20% increase has a visual appearance of an 80% increase.
For me, companies misleading their potential customers with their visual marketing material in such a way will get an extra portion of scrutiny from me regarding their claims.
Achim,
A friend of mine with a SR20 (> 500h) doesn't even know much about the red lever, he just pulls it back a little bit (to the level of the "X" in "MIXTURE" which is written next to it as he explained to me). He doesn't know Vx and Vy either.
That guy needs a bit of work... I find that totally unacceptable and I wonder how he passes his flight checks. The SR20 needs to be mixed properly like the next airplane and if I recall correctly, the EFIS gives him quite a few hints on how to do it. Not knowing those speeds and "mixing" like that does not sound like a competent pilot to me.
I always thought the solution Cirrus went for was a bit half done... either you put a proper FADEC and have a single lever or you stay conventional. So if the move is to bring back the prop lever, they basically admit they failed with that. Looking at the performance figures, I found that there should be more possible with that airframe especcially in the range department.
Had a talk once with one guy who works for one of the new companies in Eastern Europe building the small planes which seem to become so popular now. One bit we discussed is how to do a proper one lever engine control. His answer was if he could decide that, he'd have a full fadec steered with an either integrated or separate control panel where the pilot could choose between Max Speed, Max Performance, Max Range e.t.c. The engine would then be configured accordingly in all three controls.
I've seen something like that used on the Saab 2000, a turboprop but never the less a very nice airplane from the pilots side of things. They had exactly that, one lever per engine plus a control panel with MTOP, MCP, Climb and Cruise detent. It did not have different cruise regimes, but I reckon that should be fairly easy to do.
The advantage I can see of something like that is that with the analyzing capabilities we have today, we could probably achieve a very advanced kind of engine management and get those who are e.g. scared of the mixture control or don't know how to really use it (which is a frighteningly high number of pilots) a real assistence. In combination with the GNSS systems we have, we could easily implement calculations per route, e.g the FMS could calculate the max fuel flow it can afford to reach the destination and then calculate the best possible performance for the given route, e.t.c.
Unfortunately, due to the certification nightmare we do have, I reckon we might see such things on non certified planes soon enough but it will be a long time before someone comes up with something like it for certified planes. I once had the chance to fly one of the planes in question, equipped with a full set of Dynon Avionics including AP and I have to say they are miles ahead of most of our airplanes for a ridiculous price. Why we can't have such instruments in our privately operated planes will stay beyond me.
Best regards Urs
Thanks for all of the good questions/comments. Fullest disclosure: my company makes the Control Quadrant Upgrade that adds the propeller level back to the quadrant.
Just a couple of points…
I’m not sure what was meant by ROP not being in alignment with the Cirrus POH. My POH specifically states, “Best Power is achieved at 750 F Rich of Peak EGT” (SR22, Section 4 Normal Procedures, Cruise Leaning).
I’m sure you know there continues to be a lot of controversy/dialog on ROP and LOP. I candidly am in the LOP camp – driven there by some excellent articles by the GAMI folks and Continental (you can “google” for those). We included the ROP charts because many (most?) Cirrus pilots seem to operate their aircraft ROP.
Tamarack Aerospace Group is comprised of a small group of very experienced engineers and pilots. The Control Quadrant Upgrade was something that we as pilots wanted in our aircraft, and thought that other pilots might like it in theirs. We had some engineering time available, so we decided to go ahead with the STC. But, it is something like manual vs. automatic transmissions. Some people like the extra control and economies; some people like the simplicity of the single Power Lever (as an aside, you would be surprised how many comments we got on why we would “bypass the FADEC”!).
Rory also had some comments on the LOP table. I’m afraid there maybe some confusion – Air “speed” is not on this chart. Propeller Speed (RPM) is, but that scale does not start at 0. There certainly is no intent to mislead, everything is on the chart, and yes, you do need to pay attention to the scale on the charts.
We certainly welcome any and all scrutiny; it helps us make the product stronger!
If you would like to reach me directly, my email is: [email protected]
Cheers!
Rotor ATP SEL/MEL FAA “Gold Seal” CFI/II/MEI Master CFI-A
Finally I got around to doing a little test...
All done at peak EGT i.e. best-economy.
There are worthwhile economy gains at lower RPM.
I used just 20" MP because the engine doesn't like running at 23" at 2200rpm or less, but at Eurocontrol altitudes (FL100+ generally) one flies at wide open throttle and the MP is low enough.
Unfortunately, due to the certification nightmare we do have, I reckon we might see such things on non certified planes soon enough but it will be a long time before someone comes up with something like it for certified planes.
I wonder why that would be. You just have to calculate those figures and let the pilot do the actual settings, just some sort of proposed setting display. Similar to the speed to fly indicators in gliders. You don't need to certify a lot with this system (at least at a first stage).
Cheers,
I have a little over 100 hours in a SR22TN, 2008 with the Perspective system. The TN supplement really only shows LOP operation for cruise. Climb is ROP at 32 GPH or so or LOP around 16 GPH, but LOP climbs only work for short climbs or on particularly cold days. The Perspective engine management information on the MFD shows % Power and fuel flow with a blue line representing the desired LOP maximum fuel flow. Initial climb is full power ROP, then pull the power lever until the RPM drops to 2500. At level off, you pull the mixture to set the power. At 85% power, the blue line is just below 18 GPH. I would normally cruise with the fuel flow at 16 to 17 GPH, around 75 to 80%, engine ran smooth and cool, always LOP. One could generally count on 180 Knots at low altitude, it is a fast sucker, but in comparison to the way my Bonanza flies, I very much prefer the Bonanza. It has a great autopilot and flies wonderfully, except when hand flown, but maybe that is my poor technique. It is very unforgiving in landing and the TN being nose heavy runs out of side stick a lot sooner than I would like.
