TURBO

FlySince9

FlySince9

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Jerry
Is there anything that makes operating a turbocharged engine more complicated than non-Turbo...

Also, how much does a turbo add to operating costs?
 
From what I hear watching the manifold pressure is pretty important...:eek:
 
As someone who's only been in classes for it and read about it (never flown a turbo charged engine) I'd say yes. And how complicated depends on how the turbo is set up. I've looked airplanes with manual waste gates. You had to monitor and adjust the boost by hand while also handing mixture, prop and throttle. Some are self adjusting and somewhat easier but you still have to manage throttle , prop and mixture so as to not over boost. Then there are "turbo-normalized" which self adjust the turbo to maintain sea level pressure until it can't.

John
 
It more complicated and easier to damage an engine, but most setups are actually pretty simple.

The Turbo Normalized Viking I was flying had a Manual waste gate, you just flew it like a normally aspirated engine until you got to an altitude where you couldn't maintain manifold pressure with the throttle, then you started opening the waste gate to maintain cruise manifold pressure.

Brian
CFIIG/ASEL
 
My Mooney Acclaim is turbo normalized and not much more complicated to operate than my normally aspirated RV-8. Just need to add throttle gradually during the takeoff roll to avoid overboosting, and then watch the turbine inlet temperature when leaning for cruise, but that's about it. I'm not sure if my Mooney costs any more to maintain then a normally aspirated Ovation.
 
jsstevens said:
As someone who's only been in classes for it and read about it (never flown a turbo charged engine) I'd say yes. And how complicated depends on how the turbo is set up. I've looked airplanes with manual waste gates. You had to monitor and adjust the boost by hand while also handing mixture, prop and throttle. Some are self adjusting and somewhat easier but you still have to manage throttle , prop and mixture so as to not over boost. Then there are "turbo-normalized" which self adjust the turbo to maintain sea level pressure until it can't.

John
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I had no idea there were planes with manual waste gates...that would be pretty annoying to have to adjust boost. If I ever get a turbo'd plane I'll definitely make sure to get a turbo-normalized one.
 
Matthew K said:
I had no idea there were planes with manual waste gates...that would be pretty annoying to have to adjust boost. If I ever get a turbo'd plane I'll definitely make sure to get a turbo-normalized one.
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The ones I've seen were older twins. So you have to do it twice twice.
 
From an operations standpoint, turbos really aren't much harder to fly. There are different systems and you need to understand how each one works. The most common is a setup that will limit your maximum boost (i.e. you firewall the engine on takeoff) and will then hold whatever manifold pressure you set with the throttles. In this regard, it's actually simpler. Just set your manifold pressure and don't have to worry about it changing during climb, etc. From a pilot's perspective, that's nice.

If you have a manual wastegate or a fixed wastegate, then they do require some more vigilence, since you have to make sure not to overboost the engines and set appropriately.

The main thing is that turbocharged engines are more complex and have more failure modes. Things like induction leaks really matter and require chasing. There's extra heat in a lot of places which makes many parts not last as long. Exhausts are often made of exotic materials (such as inconel). On the turbo Twin Cessnas, for example, it's about $10k per engine. Turbos are about $3k each for an overhauled unit. You don't have to replace them often, but when you do, it's spendy.

Turbo engines also tend to run hotter and are usually more prone to going through cylinders, but a lot of this is how you operate them. Turbo planes usually burn more fuel.

I've got something on the order of 300-500 hours in turbo piston twins and a few thousand more of running them. When going from the 310 to the 414, I really wasn't thrilled about getting turbos because of the extra failure modes and expensive parts. But they're necessary to fly at 19,000 ft with 31" manifold pressure, and also necessary for pressurization. So far I've had to get one turbo un-stuck (fortunately I was able to get that taken care of with a cleaner rather than actually needing a new turbo) and had to deal with a couple of leaky intake gaskets. So far no exhaust issues (knock on wood), but the plane also had several new exhaust components done recently.

Do you have a particular plane in mind? That would help.
 
Another important operational difference is that you want to let a turbo engine run a few minutes on the ground at idle before shutting down to cool the turbos.
 
Grum.Man said:
Another important operational difference is that you want to let a turbo engine run a few minutes on the ground at idle before shutting down to cool the turbos.
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Correct. 3 minutes is the general rule. For larger airports by the time you land, taxi off the runway, and get to where you're parking, it's been 3 minutes (or close enough). At 8A7, you'll probably end up waiting around a bit given how small it is.
 
brcase said:
It more complicated and easier to damage an engine, but most setups are actually pretty simple.

The Turbo Normalized Viking I was flying had a Manual waste gate, you just flew it like a normally aspirated engine until you got to an altitude where you couldn't maintain manifold pressure with the throttle, then you started opening the waste gate to maintain cruise manifold pressure.

Brian
CFIIG/ASEL
Click to expand...

Wouldn't that be closing? Open wastegate allows complete turbo bypass creating no boost.
 
Meh....are they harder to operate? No

If it doesn't work right will you know what's going wrong? Probably not. But you will need to pay good attention to what's happening and when it's doing it.

It may not cost you any extra....till you need someone to diagnose a problem and fix any of the turbo systems. Your average A&P may not be versed in your system....and could rack up labor hours learning.

They do require a little extra preventative maintenance ...keeping linkages lubed with mouse oil, but that's not hard to learn.

I sure do like the extra performance I get with mine.....
 
Grum.Man said:
Another important operational difference is that you want to let a turbo engine run a few minutes on the ground at idle before shutting down to cool the turbos.
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that's debatable....if you have a monitor you'll notice things actually warm up with that 5 minute idle run.

My turbo is actually the coolest when we're over the numbers at idle....the TIT gets "hotter" as we taxi in. I try and keep the idle as low as possible, to prevent further turbo heat, after touch down and taxi. If I sit and idle my temps go from 650 F to +950 F.
 
Grum.Man said:
Another important operational difference is that you want to let a turbo engine run a few minutes on the ground at idle before shutting down to cool the turbos.
Click to expand...

Just add to what you said, cooling is important to the turbos so the oil doesn't coke on the shaft which will cause problems. On a hot day 3 minutes of just above idle will be enough, or whatever the POH suggest.
 
Ted DuPuis said:
Correct. 3 minutes is the general rule. For larger airports by the time you land, taxi off the runway, and get to where you're parking, it's been 3 minutes (or close enough). At 8A7, you'll probably end up waiting around a bit given how small it is.
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And if power is managed on descent everything is cool upon landing. The system will only see temperature rise after landing.
 
Many aspects of turbos have been mentioned. A few folks actually have experience to base their comments on. I've got a bit over 700 hours depending on a turbo to function correctly. Much of that time over the hills north and west of Denver.

The most important thing is that the operator understand the system and monitor operating parameters. Monitoring and adjusting during the take-off roll can be critical on some systems. At first it is a major bother but after a hundred hours it is mostly automatic. And then there is the day that you just have to clear an obstacle...pop off valves can be your friend...
 
Checkout_my_Six said:
that's debatable....if you have a monitor you'll notice things actually warm up with that 5 minute idle run.

My turbo is actually the coolest when we're over the numbers at idle....the TIT gets "hotter" as we taxi in. I try and keep the idle as low as possible, to prevent further turbo heat, after touch down and taxi. If I sit and idle my temps go from 650 F to +950 F.
Click to expand...


I have found the inverse. I'll let mine spool down and I typically see 920deg when I hit the brakes on the ramp. I pull power to the lowest idle I can and sit. I generally see it settle to 730deg after a few min. I do carry power into the flare with the T tail though. In my archer, I could pull power over the fence and chirp the stall horn when the mains touch no power.


As for the OP, my experience with the the TIO540 is that firewall power settings over boost very quickly. On TO, I've been seeing 35-36" MP at rotation and will have to pull rpm back after rotation to avoid over boosting it. Generally I like 33" at 2500 rpm on climb out. It can get busy from the start of the TO roll to initial climb to manage the boost, but once you know what's going on, it's second nature. The dummy light in front of me helps too.
 
Forgot to mention that being boosted also comes a higher fuel bill. Down low, not so,much. Up high, you are still burning sea level fuel if that makes sense. I typically cruise around 19 gal an hour. I'm still trying new rpm/mp settings but right now 2300 rpm and 29" sees to be good. But I do still have a lot to learn about this beast. I've only got about 5o hours on it since I bought.
 
full disclosure...I was referring to a TSIO-520 in a Bonanza....and I land with minimal power on final and in the flair. Think about when air flow and cooling is the best....in the air....not on the ground.
 
genna said:
Wouldn't that be closing? Open wastegate allows complete turbo bypass creating no boost.
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correct. I said it wrong.
from the cockpit it just looks like 2nd throttle, when you max out the 1st you go to the 2nd and make sure you don't overboost the engine.

Brian
 
brcase said:
correct. I said it wrong.
from the cockpit it just looks like 2nd throttle, when you max out the 1st you go to the 2nd and make sure you don't overboost the engine.

Brian
Click to expand...

that's the type of turbo system I would want because I don't do high density altitude flying.
 
Unit74 said:
Forgot to mention that being boosted also comes a higher fuel bill. Down low, not so,much. Up high, you are still burning sea level fuel if that makes sense. I typically cruise around 19 gal an hour. I'm still trying new rpm/mp settings but right now 2300 rpm and 29" sees to be good. But I do still have a lot to learn about this beast. I've only got about 5o hours on it since I bought.
Click to expand...

You may burn more fuel but you're also going much faster, so your actual fuel bill may or may not be higher for the same flight.
 
I think the "burning more fuel" is a bit misleading. If you do not use the turbo and fly it with 0 boost, you will be burning same fuel and having almost the same performance numbers as comparable NA plane. There is a small penalty due to more weight and complexity of the turbo setup, but it's very small. More fuel burn comes from your ability to use more power(which is the entire point of it), but nobody is forcing you.
 
FlySince9 said:
No, I've been doing some window shopping and noticed that, in some cases, turbos appeared to be less expensive than a comparable NA cousin...
Click to expand...

That is often true, and the maintenance aspects are the reason for it.

Most people I come across who buy turbo airplanes and don't need the altitude performance end up wishing they hadn't. But if you're going to use the extra capability, then it's worthwhile.

genna said:
I think the "burning more fuel" is a bit misleading. If you do not use the turbo and fly it with 0 boost, you will be burning same fuel and having almost the same performance numbers as comparable NA plane. There is a small penalty due to more weight and complexity of the turbo setup, but it's very small. More fuel burn comes from your ability to use more power(which is the entire point of it), but nobody is forcing you.
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True, but often times you have to run richer to keep CHTs down (if running ROP). And running LOP with a turbo has less tolerance for imperfection from a system's perspective. Ignition, induction, etc. need to be perfect, so a lot of people end up just foregoing LOP.
 
Ted DuPuis said:
Most people I come across who buy turbo airplanes and don't need the altitude performance end up wishing they hadn't. But if you're going to use the extra capability, then it's worthwhile.
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Can't you just remove the turbo?
 
Checkout_my_Six said:
mine runs lean with no problems....
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Sure, but you're at least a reasonably mechanically competent individual. ;)

There are a lot of engines that need some work (GAMIjectors, induction leaks, etc.) to make work LOP well.

midcap said:
Can't you just remove the turbo?
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It depends. If the turbo is part of an STC and not part of the initial certification of the aircraft or the engine, then yes, you can remove it. Some aircraft have, on their Type Certificate, options for turbo or non-turbo engines. If that is the case, the non-turbo engine can be swapped out, but you typically can't simply remove the turbo. You could also go the really hard route and make an STC for an aircraft that substitutes a turbo engine for a non-turbo engine. For example, the Colemill Bearcat II STC replaces the TSIO-520 engines on T310P, Q, or R aircraft with IO-550 engines.

Turbo engines also usually have differences in the fuel system and often the ignition system as well. Often, there are airframe side differences to account for different exhaust locations, turbo heat shielding, etc.
 
Yea, I don't think I'd use it much here in the piedmont, except to cross over to Tennessee once in a while... don't think I'd want the added attention they require. A lot of good info though...appreciate it, guys...
 
yup....it depends. And some of those engines, mine included, need the turbo at low altitude because of the low compression engine. This is a bit of an Achilles heal....and the cause for efficiency loss. Driving a turbo does cost energy....or gas....even if it's not producing boost. Thus the reason for the turbo normalizing configuration. They're a bit more desirable and more efficient.

I'm very much an east coast flat lander and don't use Oxygen much....but, having the climb performance in the summer is very nice.

This turbo thingy does grow on you....I like mine.
 
Speaking of forced induction. How come superchargers have not become adopted in GA? If i remember correctly, they were all the rage in WWII high altitude fighters.
 
genna said:
Speaking of forced induction. How come superchargers have not become adopted in GA? If i remember correctly, they were all the rage in WWII high altitude fighters.
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Superchargers have some significant limitations. Since they're gear-driven (or belt-driven, depending on the setup) they need to spin at a fixed RPM, which will give you essentially a fixed pressure ratio. If you're trying to maintain 30"', that pressure ratio is 1:1 at sea level, roughly 2:1 at 14k, etc. It ends up hurting efficiency to have the supercharger spinning at a sub-optimal RPM. There are supercharged GA engines. The Twin Bonanzas and some Twin Commanders had supercharged Lycomings. They worked but were not particularly efficient. This was partly because the technology just hadn't evolved. So, turbos seemed better. Set them and forget them (assuming the controllers are working correctly), and more efficient.

Today, superchargers (and turbos) have come a long way. I was actually looking at adding superchargers to the 310, and talked to these guys about it:

http://www.forcedaeromotive.com/

The project never went anywhere, as there wasn't very good space under the cowling of the 310 in the necessary locations. However they do put superchargers on various airplanes, and the modern superchargers they use are very efficient.

Personally I'd rather have superchargers with their limitations as I think they're more reliable and ultimately more efficient than turbos for how they'd be used on, say, the 414, but the cert efforts would be fairly ridiculous on something like that. I'm also not sure if I could realistically get something that would have high enough pressure ratios to maintain, say, 30" at FL190 without having poor tendencies down low. And really 31-35" for climb power. Ceiling is FL300 on the plane which is rather ridiculous and never used, but FL250 would still be nice to have.
 
I think the superchargers are great when run at optimum altitude/speed, but since they directly geared to the engine, it always robs power to make power. Turbos do that as well, but are not nearly as parasitic on the engine when operating at lower power levels. The superchargers do have the benefit of being much less complex in terms of design and fewer potential failure modes.
 
Superchargers give the same amount of boost at all altitudes. Like an additional 8" manifold pressure, so you have 38 at sealevel and it goes down 1" per 1000' (approx). Might as well get a bigger engine. Turbos keep sealevel pressure all the way up to their critical altitude (I think it is called) and a plane with a turbo has sealevel power up high but reduced air decreases drag and they really go fast. Big difference. Turbos and Superchargers run engines hard and shorten their life. All that fuel burn takes its toll. They have shorter TBO's (if you run them hard). And you need oxygen to fly up there.
 
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