IO550 vs Cirrus installation

[Tantalum]

Part of this may also come down to how quickly people lean the engine. The transition course I took was very strict on keeping CHTs below 380, and I now push to operate in the 360 range or better, leaning as required to keep the temps low.. that has seemed to work pretty well. Climbs are always full rich. Someone mentioned above the "big pull" method of leaning, as opposed to gently pulling the mixture back.. which the lean assist page is a disaster at.. when I've seen other people use it they'll spend 5 minutes on that page science experimenting with it.. just crank it back and lean to the desired fuel flow then adjust

Think about it, if you gently pull it back you could spend a good 30 seconds in that danger zone, vs if you do the big pull you kind of just pass through it.. after 800 or so hours of flying that is not an insignificant figure

**People have mentioned running at 65% vs 85% power, etc. Frankly, for how massive that engine and cylinders are I feel like it is grossly "de-tuned" for what it could handle. I firmly do believe that it comes down to temps and other operational techniques and considerations. 85% power out of a 310 hp engine gives you 265 hp (about)... out of a 9.1 liter engine is, quite patently, pathetic. You can't tell me that puts any kind of real "abuse" on it

 

[Checkout_my_Six]

I know they are completely different animals... but in the turbo Bonanzas, if you run at the max continuous power (balls to the wall), they go through cylinders like oil. Reduce manifold and rpm after takeoff and the cylinders will go to tbo.

On the other hand. Cylinders are relatively inexpensive, replace them when they need replacing and enjoy the power.

mine is a turbo Bonanza......

 

[TheGolfPilot]

mine is a turbo Bonanza......

I’m sure you have read this already then!
https://www.dropbox.com/s/yy7saag0a38mdp6/ABS article r2.docx?dl=0

 

[Checkout_my_Six]

I’m sure you have read this already then!
https://www.dropbox.com/s/yy7saag0a38mdp6/ABS article r2.docx?dl=0

yup....good stuff.

 

[wayne]

To be fair, I think there may be a single FADEC-eqiuipped Cirrus out there somewhere, which I sssume has no mixture control.

I haven't seen that yet, still could be out there, but there is a STC for adding a blue knob.

 

[MetalCloud]

Part of this may also come down to how quickly people lean the engine. The transition course I took was very strict on keeping CHTs below 380, and I now push to operate in the 360 range or better, leaning as required to keep the temps low.. that has seemed to work pretty well. Climbs are always full rich. Someone mentioned above the "big pull" method of leaning, as opposed to gently pulling the mixture back.. which the lean assist page is a disaster at.. when I've seen other people use it they'll spend 5 minutes on that page science experimenting with it.. just crank it back and lean to the desired fuel flow then adjust

Think about it, if you gently pull it back you could spend a good 30 seconds in that danger zone, vs if you do the big pull you kind of just pass through it.. after 800 or so hours of flying that is not an insignificant figure

**People have mentioned running at 65% vs 85% power, etc. Frankly, for how massive that engine and cylinders are I feel like it is grossly "de-tuned" for what it could handle. I firmly do believe that it comes down to temps and other operational techniques and considerations. 85% power out of a 310 hp engine gives you 265 hp (about)... out of a 9.1 liter engine is, quite patently, pathetic. You can't tell me that puts any kind of real "abuse" on it

Yeah CHTs below 380 and TITs. I never run at 85%... always 75% for cruise. I tried running at best power once but TITs went high and I backed off.

I’m with you on the big pull. When leveling off, I’ll pull power first then mixture back. Seems to make more sense than easing it back slowly, and it’s easy to dial in the target numbers. I never use lean assist... I did in the 182, but for the Cirrus I lean to target fuel flow and check CHTs and TITs. The cyan line is helpful but sometimes it’ll make me go too lean.

Hmmm. Maybe I do need a sensor adjustment somewhere

 

[MooneyDriver78]

If you have a engine monitor, you can lean in the climb. I would lean to keep EGTs about 150° ROP, plenty rich enough but also getting best power.

 

[Tantalum]

I never run at 85%... always 75% for cruise

Yes. You'd be hard pressed to get 85% power out of it anyway with the CHTs or TITs anywhere in a comfortable range.. I feel like I'm generally temp limited to somewhere in the 74% to 76% range.. environmental factors depending of course. In the G5 I did my transition on the SOP for the club was 85% cruise as long as CHTs were under 380.. this setup resulted in CHTs right around the 378-385 range.. but the savvy data showed some people ran higher towards the 400 range (which our organizer was good at publicly email shaming people on lol). Naturally, by the time the engine had 800 hrs on it they began having issues with oil loss, low compression, etc.

I’m with you on the big pull. When leveling off, I’ll pull power first then mixture back.

Yup. It does freak people out who aren't used to flying in the plane though. I've brought some 172/182 friends up in it who are used to fiddling slowly with the vernier knob like they're tuning a piano, they watch me do that one big pull and I can always see them get tense for a minute

**Keep in mind also that these engines, really, are piles of rubbish. The tolerances are loose, metallurgy is suspect, and in general one is not like the other. Every 172N/180 in our club has the same engine, yet each one feels totally different. So we're used to operating airplane engines like an exact science since most pilots are type A perfectionists.. but keep in mind that sometimes the metal and engine you have just might not last that long even if you run at textbook values. Other people can probably get away with 85% power until TBO and beyond, just by luck of the draw

but there is a STC for adding a blue knob

Not an incendiary statement on my part, a genuine question though.. for a cross country cruising plane like the Cirrus what's the point of that really? As in, what's the value added? The blue knob planes I've flown are generally very straightforward.. max RPM for takeoff, then dial it back a little for climb, then dial it back yet again to the 22-24 RPM range for cruise.. in reality the blue knob moves in and out less than a quarter inch during normal ops. What is gained by adding it to the Cirrus? Heck, the checklist for the 182 generally for the prop and man pressure just say "as desired" .. so as long as you're in the green it's just another thing to fiddle with

 

[Tantalum]

If you have a engine monitor, you can lean in the climb.

Good point, but in a turbo setup on the Cirrus you'll basically get sea level manifold pressure until around 18K.. so there isn't much in the way of leaning.. just keeping fuel flow near the red-line (ish) to keep CHT low. (Some) of the non turbo's have an altitude compensating fuel pump so same thing, you don't really lean it. This was strange to me the first few times I departed Big Bear in a NA SR20 at full rich

 

[Kenny Phillips]

And all of this should be moot, with our single-lever FADEC systems. That cars have had for decades. Cars that cost less than an O-200.

 

[Checkout_my_Six]

And all of this should be moot, with our single-lever FADEC systems. That cars have had for decades. Cars that cost less than an O-200.

Should be... but not.

 

[vman]

I know they are completely different animals... but in the turbo Bonanzas, if you run at the max continuous power (balls to the wall), they go through cylinders like oil. Reduce manifold and rpm after takeoff and the cylinders will go to tbo.

On the other hand. Cylinders are relatively inexpensive, replace them when they need replacing and enjoy the power.

afaik, continental jugs are known to be problematic from new..

another beechtalk thread - Superior Millennium cylinders

 

[wayne]

Not an incendiary statement on my part, a genuine question though.. for a cross country cruising plane like the Cirrus what's the point of that really? As in, what's the value added? The blue knob planes I've flown are generally very straightforward.. max RPM for takeoff, then dial it back a little for climb, then dial it back yet again to the 22-24 RPM range for cruise.. in reality the blue knob moves in and out less than a quarter inch during normal ops. What is gained by adding it to the Cirrus? Heck, the checklist for the 182 generally for the prop and man pressure just say "as desired" .. so as long as you're in the green it's just another thing to fiddle with

Some complain that the blue knob isn't there. I agree, it's not a big deal. I've flown SR22s and complex with a blue knob. They all work fine.

 

[flyingcheesehead]

Not an incendiary statement on my part, a genuine question though.. for a cross country cruising plane like the Cirrus what's the point of that really? As in, what's the value added? The blue knob planes I've flown are generally very straightforward.. max RPM for takeoff, then dial it back a little for climb, then dial it back yet again to the 22-24 RPM range for cruise.. in reality the blue knob moves in and out less than a quarter inch during normal ops. What is gained by adding it to the Cirrus? Heck, the checklist for the 182 generally for the prop and man pressure just say "as desired" .. so as long as you're in the green it's just another thing to fiddle with

Efficiency.

The SR22 is at 2700 for takeoff, comes back to 2500 near the top of the throttle travel, and stays at 2500 all the way down until it's out of the governing range.

To me, 2500 is a climb setting. I have an IO-550-G which is limited to 280hp via limiting it to 2500 RPM anyway, but if I had the N I would run it at the full 2700 for takeoff, 2500 for climb, and 2300 for cruise (Continental's minimum recommended RPM on the 550).

There are several things that help efficiency at lower RPM:

1) Lower friction losses in the engine.
2) Lower pumping losses.
3) Better prop efficiency - This may hurt Cirrus the most. The SR22 is a very noisy airplane, and it's mostly prop noise. That means the tips are getting in the transonic range, where efficiency quickly drops off. I'm sure they picked 2500 on purpose, but I'm betting it's slightly over the knee of the thrust curve yet is an OK RPM to run at any MP setting, so it makes the throttle/prop linkage simpler.

For cruise, I run mine at 2300 RPM (again, minimum recommended by Continental), whatever MP I need for 65% or full throttle, and 50º LOP. I get 170 KTAS on 12 gph.

 

[Tantalum]

There are several things that help efficiency at lower RPM

Thanks for the detailed response..

 

[tspear]

Efficiency.

The SR22 is at 2700 for takeoff, comes back to 2500 near the top of the throttle travel, and stays at 2500 all the way down until it's out of the governing range.

To me, 2500 is a climb setting. I have an IO-550-G which is limited to 280hp via limiting it to 2500 RPM anyway, but if I had the N I would run it at the full 2700 for takeoff, 2500 for climb, and 2300 for cruise (Continental's minimum recommended RPM on the 550).

There are several things that help efficiency at lower RPM:

1) Lower friction losses in the engine.
2) Lower pumping losses.
3) Better prop efficiency - This may hurt Cirrus the most. The SR22 is a very noisy airplane, and it's mostly prop noise. That means the tips are getting in the transonic range, where efficiency quickly drops off. I'm sure they picked 2500 on purpose, but I'm betting it's slightly over the knee of the thrust curve yet is an OK RPM to run at any MP setting, so it makes the throttle/prop linkage simpler.

For cruise, I run mine at 2300 RPM (again, minimum recommended by Continental), whatever MP I need for 65% or full throttle, and 50º LOP. I get 170 KTAS on 12 gph.

I think this is the first descent critique I have seen of the lack if a prop control.

Curious what you will do when we get FADEC.

Tim

Sent from my SM-J737T using Tapatalk

 

[wayne]

Efficiency.

The SR22 is at 2700 for takeoff, comes back to 2500 near the top of the throttle travel, and stays at 2500 all the way down until it's out of the governing range.

To me, 2500 is a climb setting. I have an IO-550-G which is limited to 280hp via limiting it to 2500 RPM anyway, but if I had the N I would run it at the full 2700 for takeoff, 2500 for climb, and 2300 for cruise (Continental's minimum recommended RPM on the 550).

SR22 POH shows "Power - Full Throttle" in their climb charts, including the enroute climb charts up to 16,000'.

The lowest RPM on the cruise performance is 2500 RPM.

I have a POH for a 2002 G1 and a 2013 G5 and both show that.

 

[Checkout_my_Six]

2,500 RPM is the sweet spot for prop efficiency......

I run 2,500 RPM and 26" on my TSIO-520 V35A.....and have the mixture pulled back to 15 GPH. That's a cool CHT setting....if I want to go faster I twist the red knob, increasing the gas flow, till the CHTs get to the limits (380 F usually cyl #2 is my reference for the hottest cylinder). At that point....I might even crack the cowl flaps to help with cooling.

 

[RudyP]

Efficiency.

The SR22 is at 2700 for takeoff, comes back to 2500 near the top of the throttle travel, and stays at 2500 all the way down until it's out of the governing range.

To me, 2500 is a climb setting. I have an IO-550-G which is limited to 280hp via limiting it to 2500 RPM anyway, but if I had the N I would run it at the full 2700 for takeoff, 2500 for climb, and 2300 for cruise (Continental's minimum recommended RPM on the 550).

There are several things that help efficiency at lower RPM:

1) Lower friction losses in the engine.
2) Lower pumping losses.
3) Better prop efficiency - This may hurt Cirrus the most. The SR22 is a very noisy airplane, and it's mostly prop noise. That means the tips are getting in the transonic range, where efficiency quickly drops off. I'm sure they picked 2500 on purpose, but I'm betting it's slightly over the knee of the thrust curve yet is an OK RPM to run at any MP setting, so it makes the throttle/prop linkage simpler.

For cruise, I run mine at 2300 RPM (again, minimum recommended by Continental), whatever MP I need for 65% or full throttle, and 50º LOP. I get 170 KTAS on 12 gph.

Good answer overall but there are a couple of things I'd like to point out.

You can absolutely climb at 2500rpm and full MAP on any Cirrus since the first part of the travel of the throttle/prop control reduces RPM only to 2500 rpm before reducing MAP. For NA and TN Cirrus, this is not the recommended climb procedure per Cirrus and Continental but you can easily do it if you like. The SR22T is governed to a max of 2500 RPM anyway.

You can not cruise at full MP and 2300 rpm as you point out. Fair point.

However, 2500rpm on the 78" diameter prop is Mach 0.75 for the prop tips (I just did the math) so you are not in the transonic region at the recommended 2500 rpm cruise settings. Of course, lower rpm will yield lower noise but that is a mostly linear relationship rather than a big jump because of going in/out of the transonic region.

The prop is most efficient at 2500-2700 rpm not lower. This is simply a design element and the propellers Cirrus chose are optimized for this range.

You are correct on frictional and pumping losses increasing with RPM but again, a mostly linear relationship (note - pumping losses decrease with more open throttle - not your point, but just mentioning for the benefit of other readers)

At the end of the day, I think Cirrus' solution works very well - it's an engineering tradeoff to be sure but it has an obvious ease of operation advantage, limits the ability of pilots to get the powerplant into inefficient regimes and has very, very minimal downsides.

Personally, I would love a modern, true FADEC design with just one lever but that is not very likely with dinosaurs like Continental and the FAA in the way...

 

[flyingcheesehead]

I think this is the first descent critique I have seen of the lack if a prop control.

Curious what you will do when we get FADEC.

Y'know, I would LOVE FADEC... if they did it right.

If they didn't do it right, I might have to get a job at Conti or Lyc and do it for them.

SR22 POH shows "Power - Full Throttle" in their climb charts, including the enroute climb charts up to 16,000'.

The lowest RPM on the cruise performance is 2500 RPM.

I have a POH for a 2002 G1 and a 2013 G5 and both show that.

I'm not sure what I said that you think contradicts that?

2,500 RPM is the sweet spot for prop efficiency......

Depends on the prop. The graph you posted is missing a lot of information, too... ?

You can absolutely climb at 2500rpm and full MAP on any Cirrus since the first part of the travel of the throttle/prop control reduces RPM only to 2500 rpm before reducing MAP. For NA and TN Cirrus, this is not the recommended climb procedure per Cirrus and Continental but you can easily do it if you like. The SR22T is governed to a max of 2500 RPM anyway.

Yup... Again, I think that's what I said.

I didn't realize the Turbo didn't go any higher than 2500 RPM, but I've never flown the T.

However, 2500rpm on the 78" diameter prop is Mach 0.75 for the prop tips (I just did the math) so you are not in the transonic region at the recommended 2500 rpm cruise settings. Of course, lower rpm will yield lower noise but that is a mostly linear relationship rather than a big jump because of going in/out of the transonic region.

Interesting... Why are they so dang noisy then? It sounds like prop tip whine to me.

The prop is most efficient at 2500-2700 rpm not lower. This is simply a design element and the propellers Cirrus chose are optimized for this range.

Probably because they designed the throttle/prop system the way they did.

You are correct on frictional and pumping losses increasing with RPM but again, a mostly linear relationship (note - pumping losses decrease with more open throttle - not your point, but just mentioning for the benefit of other readers)

Correct - And being able to run at a lower RPM via the blue knob allows me to go to wide open throttle at a lower altitude while getting the same power. For the same power setting, lower MAP/higher RPM will always be more efficient in terms of friction and pumping losses.

At the end of the day, I think Cirrus' solution works very well - it's an engineering tradeoff

As with most things. Otherwise, I'd have a twin that went 250 knots on 3 gph per side and hauled 1500 pounds...

Personally, I would love a modern, true FADEC design with just one lever but that is not very likely with dinosaurs like Continental and the FAA in the way...

The FAA, mainly... Continental does sell a TSIOF-550 (F for FADEC), don't they? But nobody buys it because it's just stupid expensive, thanks to the FAA.

To get the sort of FADEC that cars have had for a long time, the FADEC system would not only need control of the throttle, prop, and mixture, but also the ignition... And the FAA hasn't allowed any certified installations that replace both mags with electronic ignition yet, even absent any FADEC at all.

 

[Tantalum]

I'd have a twin that went 250 knots on 3 gph per side and hauled 1500 pounds...

Hey, the diamond DA62 gets pretty close to those figures.. and it has a proper FADEC..

it's just a crazy expensive plane that's not pressurised and ultimately doesn't go that fast.. but a cool and capable machine none the less

 

[flyingcheesehead]

Hey, the diamond DA62 gets pretty close to those figures.. and it has a proper FADEC..

it's just a crazy expensive plane that's not pressurised and ultimately doesn't go that fast.. but a cool and capable machine none the less

I was going to mention, my fantasy twin would be available for $80K brand new.

 

[Tantalum]

I was going to mention, my fantasy twin would be available for $80K brand new.

Twinkie?

 

[flyingcheesehead]

Twinkie?

Burns more, hauls less, slower, and I guess I should have specified 2018 dollars. But all planes still have engineering tradeoffs, which is why my fantasy twin will never exist.

 

[Tantalum]

which is why my fantasy twin will never exist

With the right engineering know-how I bet you could build that dream plane, the catch would be the $80K price tag..! It's a shame really that the costs are so outrageous for aviation. For the price of a new DA62 you can get a very nice house or several very nice cars. Or 3,000 lbs of composite material and two small diesel motors. Crazy.

 

[AnthonyS1]

With the right engineering know-how I bet you could build that dream plane, the catch would be the $80K price tag..! It's a shame really that the costs are so outrageous for aviation. For the price of a new DA62 you can get a very nice house or several very nice cars. Or 3,000 lbs of composite material and two small diesel motors. Crazy.

Yeah and what's the reasoning for this???? I once read something I thought was very funny.... the air conditioner option in the Cirrus costs as much as a new Honda Accord yet the air conditioner that comes with the Cirrus does not even work nearly as well as the AC in the Honda Accord. LOL.

 

[Tantalum]

Yeah and what's the reasoning for this???? I once read something I thought was very funny.... the air conditioner option in the Cirrus costs as much as a new Honda Accord yet the air conditioner that comes with the Cirrus does not even work nearly as well as the AC in the Honda Accord. LOL.

Alright well let's not poo poo the Cirrus. Aviation in general is crazy expensive. Regulations and remarkably low volume are part of it.. Only around 1,000 new piston single engine planes are sold in a year while we have over 320,000 Honda Accords alone produced in a year..

..but, I do think there's also an abusive racket when it comes to aviation items. I posted about this once before, but check out these costs:

https://www.sportys.com/pilotshop/robotow-heavy-duty-cordless-towbar.html
*Over $1,100 for what is effectively a $50 Black and Decker drill on a metal rod

https://www.sportys.com/pilotshop/arctic-air-portable-air-conditioner-52-qt-dual-fan-12-volt.html
*Over $600 for basically a generic $15 WalMart cooler, $3 dryer vent hose, and maybe $15 in fans that you could buy at any PC supply shop

https://www.sportys.com/pilotshop/flight-gear-hp-tailwind-backpack.html
*$100 for what is essentially a generic LL Bean bag with a few stickers on it and extra pouches. You can't tell me it costs more than $12 to manufacture this in China somewhere

Anyway, the list goes on.. flying is expensive but it doesn't always *have* to be

 

[hindsight2020]

Alright well let's not poo poo the Cirrus. Aviation in general is crazy expensive. Regulations and remarkably low volume are part of it.. Only around 1,000 new piston single engine planes are sold in a year while we have over 320,000 Honda Accords alone produced in a year..

..but, I do think there's also an abusive racket when it comes to aviation items. I posted about this once before, but check out these costs:

https://www.sportys.com/pilotshop/robotow-heavy-duty-cordless-towbar.html
*Over $1,100 for what is effectively a $50 Black and Decker drill on a metal rod

https://www.sportys.com/pilotshop/arctic-air-portable-air-conditioner-52-qt-dual-fan-12-volt.html
*Over $600 for basically a generic $15 WalMart cooler, $3 dryer vent hose, and maybe $15 in fans that you could buy at any PC supply shop

https://www.sportys.com/pilotshop/flight-gear-hp-tailwind-backpack.html
*$100 for what is essentially a generic LL Bean bag with a few stickers on it and extra pouches. You can't tell me it costs more than $12 to manufacture this in China somewhere

Anyway, the list goes on.. flying is expensive but it doesn't always *have* to be

Those ^^^ things are easily scofflawed, so I don't have much grievance against them, though your point is noted. It's the "panel mount" BS and part 23 that incenses me, and the reaction that somehow when it comes to that, the gouge is now legitimately supported by "black magic" endemic to the FAA TSO/PMA or whatever else A&P pedantic sophistry gets thrown around.

As to piston air conditioners, I've been underwhelmed by their BTU output compared to automotive counters. The only air conditioner I've been happy with was the Texan II, and that's a tiny cabin to cool, albeit an outright greenhouse. Maybe the 28V variants in new production pistons have actually got better on the oomph factor. The vents and blower capacity of a PA-28 are a joke for instance, for the weight penalty on an already underpowered setup. I remember riding backseat in a C-340 once with 4 other males after getting picked up from dropping of a BUFF @ KTIK. The AC was a joke. I don't know if it was an actual blower capacity issue or the refrigerant level was weak, but that was one of the few days I hoped to have had a Piper door or Cessna drive-thru window to crack open, and dispense with the "catchet" of that pretentious airstair.

 

[Tantalum]

The vents and blower capacity of a PA-28 are a joke for instance

Yes they are properly pitiful. The Cirrus systems aren't bad in general, but I agree.. aviation air conditioners are mediocre at best. Hell, even a commercial airliners gets warm and stuffy until they get in the air

 

[flyingcheesehead]

Those ^^^ things are easily scofflawed, so I don't have much grievance against them, though your point is noted. It's the "panel mount" BS and part 23 that incenses me, and the reaction that somehow when it comes to that, the gouge is now legitimately supported by "black magic" endemic to the FAA TSO/PMA or whatever else A&P pedantic sophistry gets thrown around.

The "accessories" are expensive even though the materials aren't, because people like money and in a small market, things that are designed specifically for that market are likely to be expensive to recoup R&D, marketing, and overhead costs and provide a decent profit (which is the whole reason why they're making the product in the first place). If you think you can do better, then please do!

WRT Part 23 certification - Yeah, it frustrates me a lot sometimes, but overall, I would still rather have it than not. I want to be sure that when I'm going up in the sky, the equipment I'm using has had at least some level of third-party engineering review so I have a reasonable assurance that it'll work as advertised and not start on fire.

There have been a lot of improvements made lately, which is a large part of why we're suddenly seeing things like the Garmin G5 and all the new, cheaper but fuller-featured autopilots. There's still work to be done, but the situation is improving.