Turbo performance question

[wsuffa]

I broke these up into three parts because I wanted to answer the questions without opinion of whether you should buy a turbo anything... If you have plenty of experience in complex then the advantages of the turbocharger over its naturally aspirated cousin are significant and NOT just at oxygen altitudes. That said there is a Lot more overhead in workload to consider with a turbo. Over boosting is one of those. Except for the really new planes an automatic waste gate is not the same as a turbo-normalized waste gate. You have to watch your throttle settings. Automatic waste gates like my Merlin mean they will adjust to provide full power to higher altitudes.. Example, critical altitude (full rated power) in a standard Turbo Arrow with fixed waste gate is 12,000 feet but with my Merlin it is 18,000 feet. So besides riding the throttle as you climb, you must watch your turbo And cylinder head temps as there is a lot of heat built up! Also not shock cooling the engine is a big thing. You have to plan descents like an airliner does. I usually start my descent from 11,000 about 60 miles out so I can stabilize my descent at about 155 knotts indicated and keep enough power in to not shock cool the engine. I would not recommend any turbo without JPI type engine mgt because of the cooling and heating extremes... That constant 155 knott descent means stepping down the throttle as you go and it will easily jump up in a retractable to 180 knotts Indicated in a heartbeat if you are not paying attention. Also it means arriving at the airport still pretty fast and needing to get down to gear extension and flap extension speeds with again not shock cooling the engine. Then after you land you need a minimum of 5 minutes at idle before shutdown on a turbo. Some of that can be while taxing as long as you are at idle. So my recommendation? Don't get a turbo anything without a Lot of complex experience. But once you have it, it is doubtful you will ever want anything else but a turbo even with the extra expense. After all... Most of us buy airplanes to go fast and it is so much fun in a turbo to scream along and fly right over the center of the DFW Class B and state... Roger, I will remain clear of the class B... I will be Above your Airspace!

It really isn't much more work at all. Like learning to fly a complex, you get the hang of it very quickly, and it becomes second nature.

 

[Ted]

Insurance depends heavily on your company. There's enough competition these days that you can find one with reasonable checkout requirements even for ridiculous moves like SR22-421 with 0 multi and 0 complex. If your insurance company makes a ridiculous training request, find another company.

As to the turbo vs not, buy a turbo if you're going to see high DAs like that. if I was routinely taking off from elevations above 5k, I'd be looking turbo. If I routinely needed above 10k for terrain clearance, I'd want turbo and maybe pressurization. The 310 does pretty well around the tall rocks with naturally aspirated 520s (300 HP instead of 260 stock) so long as the weather is cold and/or the load is light. However if we routinely headed west, I'd be looking for turbos.

 

[Clark1961]

Then after you land you need a minimum of 5 minutes at idle before shutdown on a turbo. Some of that can be while taxing as long as you are at idle.

Welcome to POA. We operate the same base engine but I've got a few more modifications and about twice the time with it that you do. I added an intercooler and bolted on the fuel system from a -K to get 20 more HP.

The TSIO-360 has its pluses and minuses. I just wish there was a larger oil cooler available for it.

The statement you made above is interesting. What exactly does your POH recommend for time at idle before shut-down? During operation, when is the engine and turbo the coolest? What does the Merlyn do for cool-down? What can you do operationally to avoid cool-down problems?

Can you fry the turbo by shutting down too soon? sure
When is that likely to happen? When won't it happen?

 

[Sac Arrow]

I broke these up into three parts because I wanted to answer the questions without opinion of whether you should buy a turbo anything... If you have plenty of experience in complex then the advantages of the turbocharger over its naturally aspirated cousin are significant and NOT just at oxygen altitudes. That said there is a Lot more overhead in workload to consider with a turbo. Over boosting is one of those. Except for the really new planes an automatic waste gate is not the same as a turbo-normalized waste gate. You have to watch your throttle settings. Automatic waste gates like my Merlin mean they will adjust to provide full power to higher altitudes.. Example, critical altitude (full rated power) in a standard Turbo Arrow with fixed waste gate is 12,000 feet but with my Merlin it is 18,000 feet. So besides riding the throttle as you climb, you must watch your turbo And cylinder head temps as there is a lot of heat built up! Also not shock cooling the engine is a big thing. You have to plan descents like an airliner does. I usually start my descent from 11,000 about 60 miles out so I can stabilize my descent at about 155 knotts indicated and keep enough power in to not shock cool the engine. I would not recommend any turbo without JPI type engine mgt because of the cooling and heating extremes... That constant 155 knott descent means stepping down the throttle as you go and it will easily jump up in a retractable to 180 knotts Indicated in a heartbeat if you are not paying attention. Also it means arriving at the airport still pretty fast and needing to get down to gear extension and flap extension speeds with again not shock cooling the engine. Then after you land you need a minimum of 5 minutes at idle before shutdown on a turbo. Some of that can be while taxing as long as you are at idle. So my recommendation? Don't get a turbo anything without a Lot of complex experience. But once you have it, it is doubtful you will ever want anything else but a turbo even with the extra expense. After all... Most of us buy airplanes to go fast and it is so much fun in a turbo to scream along and fly right over the center of the DFW Class B and state... Roger, I will remain clear of the class B... I will be Above your Airspace!

Serious question - do you actually know of a specific instance where someone has destroyed an engine by shock cooling it? (I don't.)

Regarding your first point on insurance, as previously stated, whether the turbocharger makes a difference is dependent on your insurance company. Mine didn't care either way. And for that matter, when I went on the policy of my present N/A Arrow, they (Avemco) didn't care that all of my 600 hours of time in type at the time was in a Turbo Arrow.

 

[Ted]

Serious question - do you actually know of a specific instance where someone has destroyed an engine by shock cooling it? (I don't.)

There are stories of 421s (GTSIO-520s) where a shutdown from cruise caused all cylinders to crack. Now, all of these stories I've heard are old (20 years or so). That was when light cases and earlier design (read: weaker) cylinders existed, plus you had poor/non-existant engine instrumentation, so the engines were probably being run hotter than what you typically see today.

The stories could also be bogus, as I haven't talked to the individuals who experienced them.

 

[Clark1961]

There are stories of 421s (GTSIO-520s) where a shutdown from cruise caused all cylinders to crack. Now, all of these stories I've heard are old (20 years or so). That was when light cases and earlier design (read: weaker) cylinders existed, plus you had poor/non-existant engine instrumentation, so the engines were probably being run hotter than what you typically see today.

The stories could also be bogus, as I haven't talked to the individuals who experienced them.

On the anecdotal side an old A&P on the field had specific stories of on particular pilot and cracked cylinders. The story was that the pilot would fly to Denver from the west staying up high then just pull the throttles all the way off for the descent. Supposedly cylinders were replaced regularly.

Of course there are lots of stories out there.

 

[Sac Arrow]

There are stories of 421s (GTSIO-520s) where a shutdown from cruise caused all cylinders to crack. Now, all of these stories I've heard are old (20 years or so). That was when light cases and earlier design (read: weaker) cylinders existed, plus you had poor/non-existant engine instrumentation, so the engines were probably being run hotter than what you typically see today.

The stories could also be bogus, as I haven't talked to the individuals who experienced them.

On the anecdotal side an old A&P on the field had specific stories of on particular pilot and cracked cylinders. The story was that the pilot would fly to Denver from the west staying up high then just pull the throttles all the way off for the descent. Supposedly cylinders were replaced regularly.

Of course there are lots of stories out there.

I'm not saying this can't happen, but I think maybe running the engines too hard or too hot in the first place might have been what destroyed them, not necessarily excessive cooling rates. I'm just saying I've never experienced that problem or have known of anybody that did. I haven't managed to destroy my TSIO 360 in over 600 hours (save for one turbo replacement) and I never made any special effort to avoid shock cooling in descents.

 

[Ted]

I'm not saying this can't happen, but I think maybe running the engines too hard or too hot in the first place might have been what destroyed them, not necessarily excessive cooling rates. I'm just saying I've never experienced that problem or have known of anybody that did. I haven't managed to destroy my TSIO 360 in over 600 hours (save for one turbo replacement) and I never made any special effort to avoid shock cooling in descents.

I think we're basically agreeing with you. No doubt, hot and hard running wears the jugs out faster. Cracked cylinders I find are typically a result of this rather than a single shock cooling event.

They also usually happen around 800 hours, at least for Continentals. We once put a 3/4" hole in a Lycoming in 50 hours or so, but there were other reasons for that (specifically it was being run well above design power).

 

[Checkout_my_Six]

There are stories of 421s (GTSIO-520s) where a shutdown from cruise caused all cylinders to crack. Now, all of these stories I've heard are old (20 years or so). That was when light cases and earlier design (read: weaker) cylinders existed, plus you had poor/non-existant engine instrumentation, so the engines were probably being run hotter than what you typically see today.

The stories could also be bogus, as I haven't talked to the individuals who experienced them.

I'd be more inclined to think that all those shock cooling stories have another side....that no one will talk about.....the climb.

I'd bet dollars to donuts that the cylinder cracks came from the long extended high power.....low speed.....high CHT climbs.

Someone who is ham fisted and willing to chop and drop....is also one who would not take care of the CHTs during the climb.

 

[Clark1961]

I'm not saying this can't happen, but I think maybe running the engines too hard or too hot in the first place might have been what destroyed them, not necessarily excessive cooling rates. I'm just saying I've never experienced that problem or have known of anybody that did. I haven't managed to destroy my TSIO 360 in over 600 hours (save for one turbo replacement) and I never made any special effort to avoid shock cooling in descents.

I should have typed "lots of stories out there, no telling how many are accurate" instead of the closing I used.

The trick is to find the happy medium between running too hard and running too soft. When I bought the 'kota it had a lot of blow-by. A couple different shops told me to run it hard to re-seat the rings. Well, they never did re-seat and I wonder if the previous owner had already damaged the engine. No way to know and I'm not complaining since I got 600 hrs out of it before replacing cylinders.

 

[Ted]

I'd be more inclined to think that all those shock cooling stories have another side....that no one will talk about.....the climb.

I'd bet dollars to donuts that the cylinder cracks came from the long extended high power.....low speed.....high CHT climbs.

Agreed, if you have high CHTs in cruise you almost certainly have them in climb.

 

[narchee]

The turbo will deliver sea level power up to about 8000 feet sure enough(model dependent), but the prop and wings will not be as efficient at that DA as they would be at sea level. So, you do gain the performance of the engine back, but the prop and wing are still sitting at your DA altitude.

(BTW, on a 'somewhat warm day' of 76F, the DA would actually be closer to 9000')

Yes.

Important not to forget that.

Also, don't forget that on a warm day at a high airfield like Telluride your TAS for your rotation airspeed is higher. It will take longer for your engine even developing full power to accelerate the plane to that higher TAS. That effect alone could add as much as 15% takeoff roll. Don't be lulled into complacency by a turbo it is NOT exactly the same as taking off on the equivalent runway at sea level.

 

[wsuffa]

I'd be more inclined to think that all those shock cooling stories have another side....that no one will talk about.....the climb.

I'd bet dollars to donuts that the cylinder cracks came from the long extended high power.....low speed.....high CHT climbs.

Someone who is ham fisted and willing to chop and drop....is also one who would not take care of the CHTs during the climb.

Agree. I had to do climbing turns out of Henderson on a 110-degree day at close to max load in order to ensure reasonable CHTs. ATC was very cooperative.

 

[arnoha]

I would never in a million years attempt a takeoff at 8k DA with my family of 4 in a NA Cherokee 6 unless it was a really long runway and no surrounding terrain.

I have departed from Telluride in a fully loaded Turbo Lance. Not a problem.

Actually...I've done this, almost. Worked out OK. Took off full gross out of Reno on a 7000' DA day with a Cherokee 6/300. Not sure I'd try it with a /260.

Long runway, check.

No surrounding terrain...does a largish valley count?

We then flew to Minden, had lunch, and took off again to come back to Bay Area. I ended up circling the entire Carson valley to get high enough to come back. Fortunately, we had O2 aboard for everyone, so time at altitude wasn't an issue.

 

[JustinD]

I'm down in Florida and have yet to fly out west even once in my na 182T. I chose the non turbo due to the extra 90 something lbs of useful by not having the turbo. HOWEVER. If I was a mountain dweller and departing regularly from high elevation airports with high enroute altitudes I would 100% go with a turbo. But since I'm in Florida and 98% of my flying in my 182 is within FL, GA and SC those weren't a consideration to me and therefore I found the extra useful load more valuable. I've had my bird for almost 4 years and I've used that weight more than I ever would have used the turbo. When flying mine at max gross on a hot summer isa+15 to 18 day I'm barely getting 500fpm in climb at 10,000 feet, simply put NA airplanes aren't designed for hot and high mountainous performance at max weight

 

[Dmcfly50]

If you were thinking it was going to go kablooey from shock cooling then you are wrong and that's not what happens. Quick cooling creates large temperature differences on the outsides as opposed to the insides. This causes premature wear on the cylinder walls and rings and can cause a too soon needed cylinder head replacement. On a turbo itself it is even more extreme if you don't give the turbo time to cool down before shutoff. this causes extreme overheating and can cause the seals to deform and oil to leak and you will be replacing it much more often. A parallel to this is a spotlight. There are two switches on a follow spot, one turns off the light and one turns off everything. Your life expectancy on a bulb can be many uses and more than 75 hours if you turn off just the bulb and not the switch that turns off bulb and fan. Do it the wrong way and you will replace every bulb in your spots after the first use. Engine idling for 5 minutes is not dumping super hot gases through the turbo and your big fan out front can cool it down gently. Every time you don't do it you are hastening it's demise.

 

[Dmcfly50]

As far as long hot climbs yes they can certainly hurt your engine and that's more likely to be a kablooey incident as you are likely to burn and then inhale a valve head. Here being able to monitor simultaneously all six cylinders is critical. Never let that CHT get to 400 on any cylinder and that is manageable.

 

[Dmcfly50]

I think you might have meant IAS rather than TAS. An airplane could care less about TAS it is going to lift off, fly, and stall on IAS ( of course angle of attack plays a big part of the last one as well). If you rotate at 70 kts indicated at sea level you would rotate at 70 knots indicated at an airport at 7000 feet. But the salient part it is the human that cares about TAS as it is going to tell you how fast you are moving relative to an airmass. Great for navigation and figuring out head and tailwind components and calculating actual ground speed.

 

[Checkout_my_Six]

Dmcfly have you measured the tit during shutdown and seen the cooling? If I did what you did my turbo goes from 600 deg F to over 1,100 deg F, just from long idling vs a quick shutdown after landing. Try it both ways and you'll see.

 

[Checkout_my_Six]

I think you might have meant IAS rather than TAS. An airplane could care less about TAS it is going to lift off, fly, and stall on IAS ( of course angle of attack plays a big part of the last one as well). If you rotate at 70 kts indicated at sea level you would rotate at 70 knots indicated at an airport at 7000 feet. But the salient part it is the human that cares about TAS as it is going to tell you how fast you are moving relative to an airmass. Great for navigation and figuring out head and tailwind components and calculating actual ground speed.

...and temperature....and pressure....will affect TAS vs. IAS.

 

[Dmcfly50]

Yes my JPI shows it. And how are you going about getting tit after you shut down. Anyway I guess all these years every manufacturer just made that up to **** everybody off. You are perfectly free to choose any method of shutdown you want on your engine but if you did it on mine or a club airplane with the pres looking you would get your arse kicked! A plane flys by IAS not TAS look it up ! There are fewer air molecules per cubic inch the higher you go in temp and altitude. And while on a airport at a high density altitude your plane can be screaming down the runway at 90 knots on the ground but it is not going to lift off till the IAS shows liftoff speed. It's freaking physics!