Cirrus prop lever

[E1453]

I know the Cirrus has just one lever for power and prop speed.

I would like to know if any of you knows what settings the Cirrus system uses, like what MP/rpm combinations it uses for different power settings. Does it permits oversquare operation? (I do it everyday in my Bonanza).

I personally prefer to operate the controls all by my self.

Thank's.

[2Donkeys]

Cirrus MP and RPM settings are governed by a FADEC. The FADEC will frequently select "over-square" settings.

To the extent that the FADEC is more aware than the average human pilot of the optimum power settings for the engine, it will do a much better job than the human pilot.

Over-square as a concept is a grossly-simplified aid used by instructors down the ages to help people get a grip of the concepts of VP props. Sadly, bit like the "two out of three" licensng 'rule', it leads to a whole world of unnecessary confusion.

[Fly Stimulator]

To the extent that the FADEC is more aware than the average human pilot of the optimum power settings for the engine, it will do a much better job than the human pilot. Very true. When I'm flying a Cirrus I miss the prop control about as much as I miss a carb heat control, which is not at all.

E1453, the POH and various other manuals for both the SR20 and SR22 are online at the Cirrus website here (http://www.cirrusdesign.com/serviceandupgrades/pilotoperators//) if you want to have a look at them. They include performance tables for various operating conditions.

There's also a public discussion forum at the Cirrus Owners and Pilots Association (COPA) (http://www.cirruspilots.org) which is a good place to ask questions about the aircraft.

[E1453]

Thank's for the POH link!

I will copy here the page that explains the power lever system:

"Power (Throttle) Lever
The single-lever throttle control, labeled MAX-POWER-IDLE, on the
console adjusts the engine throttle setting in addition to automatically
adjusting propeller speed. The lever is mechanically linked by cables
to the air throttle body/fuel-metering valve and to the propeller
governor. Moving the lever towards MAX opens the air throttle butterfly
and meters more fuel to the fuel manifold. A separate cable to the
propeller governor adjusts the governor oil pressure to increase
propeller pitch to maintain engine RPM. The system is set to maintain
approximately 2500 RPM throughout the cruise power settings and
2700 RPM at full power."

I didn't like the last phrase. I usually fly with lesser and quieter rpms: 2100 for long range and 2300 for best operational economy.

As stated at the cruise power settings table, the pilot just selects the power setting among those available for that temperature and altitude. He then sets the correspondent MP and the RPM is automatic (normally at 2500RPM for most settings).

That's why I don't like this system: It is stupid, because it´s made for stupid pilots. It's inefficient: I'd rather set a higher MP + lower RPM for best efficiency. I always fly wide open throttle, all the way until top of descent.

I've found a very smart recomendation in the SR20's POH:
The best economy mixture setting is at 50 degrees LOP! God, they got it after all! So, why the Bonanza POH says that operating LOP is harmfull to the engine? I have been ignoring that dumb sentence since I read PelPerch columns, one year ago.

www.avweb.com/columns

(You must read it!)

Anyway, I would love to change my A36 for the SR20 soon. Just wayting the Cirrus to get cheaper in the market.

[Flyin'Dutch']

Both the SR20 and SR22 are lovely machines to fly.

They are very user friendly with great ergonomics compared to anything that was on the certified market until recently.

The combination of MP and RPM to be governed by one handle is easy but as you rightly say makes it impossible to choose anything else than the factory has determined is 'the good thing'

Yet to take someone up in one and say they did not like it!

FD

[IO540]

I am VERY suprised that the Cirrus flies at 2500rpm at all cruise power settings.

At say 65% power, I can get a 10% improvement in mpg (as indicated by a fuel flowmeter linked to the GPS which displays the mpg) just by reducing rpm from 2400 to 2200. This is when already LOP.

If one had to really extend one's range then one could go lower still, 1800rpm.

Unless I am missing something, this is very wasteful of fuel. But then the aircraft is aimed at the US market, where fuel is cheap. Because its aerodynamics is undoubtedly superior to any "conventional" 4-seater, it gets away with it, but another 10-15% mpg would be worth having.

You also get a lot more noise at 2500 v. 2300.

[Flyin'Dutch']

IO540,

I think nobody can argue with anything you state there!

FD

[Croqueteer]

Ah! My Cirrus had a fixed pitch wooden prop. Happy christmas, everyone.

[Fly Stimulator]

This year most of my flying has been in two different types, an SR20 and a couple of CT2K microlights. The fuel economy comparison is quite interesting.

In the cruise and leaned for best economy the SR20 uses about 9.5 US gallons (36 litres) per hour. The microlight's 100hp Rotax uses about 4 3/4 gallons (18 litres) per hour.

If one is just going up to potter around the sky for a couple of hours it's obviously going to cost more in fuel for the Cirrus. If one is actually making a specific journey though then the speed of the Cirrus begins to claw back the difference.

I made two very similar flights from London to Ireland this summer, one in each aircraft. The Cirrus used 15 litres more each way than the microlight, simply because I was in the air for a shorter time.

My point being that the relatively high cruising speed achieved by the Cirrus means that the fuel used per journey, rather than per hour, is not at all unreasonable.

This ignores the slight difference in purchase capital required of course. Thanks Ian! :ok:

[valenii]

This thread started with the comment:

Cirrus MP and RPM settings are governed by a FADEC

Just to keep you guys straight, this is not true. The first FADEC Cirrus is likely to be the new Diesel, and the FADEC will be about eliminating the mixture control and possibly the magnetos, not changing the way Pitch is controlled.

On all cirrus planes (SR series) build to date the VP prop is controlled using a cable in the same way as a normal VP aircraft.

If you look inside the Cirrus throttle mechanism, the "Power Lever" that the Pilot uses, actually pushs and pulls seperate throttle and pitch cables, using a series of cams and levers.

The shape of the levers and cams, not an electrical FADEC system is what controls the comblinations of MP and RPM.

Having flown more than 500 hours with the system, I can't fault it. I can see nothing that I'm missing from a normal VP set up except the possibility of getting the comblinations wrong.

I respect Cirrus for their commitment to making flying Safer, Faster, Easier and more Comfortable.

People criticise parts of the design of the SRxx aircraft without understanding the whole package. Pilot magazine ran an editorial over a year ago commenting on the wasted fuel from carrying around a solid rocket and parachute recovery system the whole time. They were flamed by Cirrus pilots in the UK. A few months later it saved a guy's life, (really?) (http://www.cirrus147.com/CAPS.htm) and now the same plane is flying again. (Press Release) (http://www.cirrusdesign.com/downloads/pdf/nr_10_30_03historicaircraft.pdf)

The key is understanding the design as a whole, what Pilot Mag missed was that even when the Cirrus was hawling the BRS around it was still going faster and further than the average Cessna for the same fuel burn.

I don't miss the "Gear Up" lever either. I flew to Bordeaux and back from London the other day, round trip less than 6 hours, and I must have been on the ground at LFBD for more than 40 mins having coffee and pastries after re-fueling....

Ian

[2Donkeys]

You're absolutely right, it was a little Diamond/Cirrus confusion there.

The point relating to over-square still stands though.

[E1453]

I loved the Cirrus from the first time I saw it. For me, the CAPS concept is perfect. I think many twin operators will be tempted to switch to the SR22. The safety x cost relation is unmatchable.

One question to Cirrus pilots: do the engine runs smooth at Best economy?

I think the only fault Cirrus has is the power lever. It´s just too inefficient to be smart. The pilot who cannot manage the conventional MP and Prop levers should not be flying anyway.

I usually fly at 9,000-12,000ft, wide open throttle, 2100 or 2300 rpm, peak EGT (I don`t have the GAMIs yet).

As for the fixed landing gear...who cares! I think the extra weight of retracts is not compensated by the lesser drag. Not at that speed range. I first noticed it when I flown the Arrow II, after one hundred yours in the Archer II. The plane is almost the same, but for the landing gear (retractable in the Arrow) and the engine (200hp in the Arrow, 20hp more than the Archer). I was surprised when I realised that the Arrow took more runway for takeoff and the cruise speed was only 15 knots faster (IAS). The payload was significantly smaller.

[Fly Stimulator]

As somebody who prefers manual to automatic cars I can understand your point of view, but in practice the Cirrus system works very well. If you really don't want to fly without a prop control then I suspect that your choice of new aircraft is going to dwindle over the coming years as the single power lever concept will probably become ubiquitous in new designs, especially as we see the rise of the diesel engine in GA.

As far as smoothness goes, the SR20 is fine at best economy. The Centennial SR22 with its six-point engine mount is very smooth indeed.

[valenii]

E1453

If you are flying W.O.T. and at peak EGT, you will probably be damaging your engine unless you are high enough and non-turbocharged to have the MP reduced by the altitude to a safe level.

The nice thing about the Cirrus is that the computers onboard are instantly working out percentage power, based on OAT, MP, RPM etc.

They also help you accurately lean to either best power or best economy. The reason that there are two different "safe" leaning states (one rich of peak EGT and one lean of peak EGT) is that running at peak, like you suggest is bad for your engine.

Another reason to go Cirrus is the fact you can see all 6 EGTs and CHTs. Believe me, there can be a spread. People who rely on only one instrumented cylinder are taking risks, they can be caught by engine failures "out the blue" their instrumentation simply does not measure the cylinder that is going wrong. Russian roulette, you have a 1 in 6 chance of seeing your engine going wrong before it blows.....

I can recommend Deakin's "Pelican Perch" articles.

They can be found Here (http://www.avweb.com/news/columns/182179-1.html)

Ian

[E1453]

As I usually run above 9,000ft, even at 12,000, and my engine is an aspirated IO-520, excessive MP is not a problem. And, as anyone who read PelPerch columns knows, peak EGT is cooler than 100 degrees ROP. For an aspirated engine (no turbine), the high EGT is not a problem. The CHTs are lower at peak EGT, wich is the best I can do without running rough in my engine.

As the CHT peaks around 75 ROP, anything leaner is cooler for the engine (expect for the turbine, if you have a turbocharger).

The best power mixture is not a "safe" setting. It's actually the most dangerous of all settings. That's the hottest you can run your engine.

I agree about the digital engine instrumentation. It can improve the engine awareness dramatically. Trends and malfunctions may be detected soon, before a total failure occurs. And mechanic's job is greatly improved. Thank's JPI!

I'm not against putting MP and prop together, if it can do the job better than myself. It would be great. But the actual Cirrus's system is not better than a good human pilot. Well, other planes have much more downsides than that, so I still want the Cirrus. The electronics is great! The chute is great! The performance is great! The price is great!

There is no aircraft today in the market that can beat the Cirrus value for money.

Today I fly an 1979 A36. It's getting old I I'm afraid it's going to be too expensive too mantain soon. I'm looking for a newer plane with comparable performance. The Cirrus is my choice.

[Fly Stimulator]

E1453,

I don't think you'd regret choosing a Cirrus. If you are seriously thinking along those lines it would be worth joining COPA (http://www.cirruspilots.org) are thereby getting access to the members' discussion area. It's a mine of useful information.

Just back from a little jaunt around southern England in Ian's SR22. A bit of a windy day, but that did give us a ground speed of 225kts at one point. The crosswind landings score was one untidy one each, followed by a good one by Ian, giving him a win on points. :{

[E1453]

I would like to know the costs of operating a Cirrus, especialy the maintenance. My A36 is getting old (1979), I love this plane, but I'm afraid of becoming a hangar king in the next years. And the beech parts are not cheap.

Also, I found that a single engine 6-seater is nothing more than a very spacious 4 seater, because if you out a reasonable amout of fuel in it, you cannot take more than four.

How is the Cirrus after-sale support? Are the parts expensive?

Thank's!

[Fly Stimulator]

I doubt that information on maintenance costs in the UK is going to be very relevant for you in Brazil. You really would be better off asking this over at COPA since many of the the people there are a lot closer to your part of the world. It's also a type-specific board, whereas the Cirrus is a bit of a minority interest here.