Turbos altitude advantage

[JB78382]

Ok, I've been in the 337 market for several months now. I have seen Ps, Ts and normally aspirated aircraft come and go. My A&P guy says the I.O. 360 was not designed to be turbocharged, and that will result in much faster engine wear. Resolve?

[YankeeClipper]

JB,

I'm by no means an expert here but have copious amounts of reading on the subject behind me. It seems that at the hand of a well trained and disciplined pilot, tbo and greater is just as achievable in a turbo. Some have argued more so, under those conditions. But was your previous owner in that category? Therein ...

But that really stands to reason, right? After all, what is the turbo that is rarely boosted past 30"? ... Warmer air at eternal sea level. More maintenance given the additional parts, yet still the owners who switched almost never, in my reading, bemoan the expense. Some old logic that may ring true still:http://www.avweb.com/news/maint/182808-1.html

[JamesC]

Many TSIO 360's go past TBO as we know. Also they make them better now eg. my SFRM TBO is 1600 hrs.
Engine management planning however as we know should be in the pre-descent checklist so that you can plan ahead and then ahead some more so that the standard 1" per min MP reductions can happen etc. The other thing is not shutting down for 5 mins until after touchdown to reduce coking. As we know sometimes ATC mismanages the flow and leaves you too high - luckily the Skymaster has plenty of drag with the gear out (140 KIAS ext'n but 130 KIAS I have been told is much easier on the gear, so I do that - means sometimes you have to pull up slightly, start extension, continue descent) and also the 1st notch of flaps is 165 KIAS which is really useful. My acft has speedbrakes- useful sometimes esp in long descents from the high teens in winter. All this to say that even though it is 'just' a Skymaster, with the TSIO's you still need to manage power and speeds really much like a bigger twin, though not to the same extent as in a geared engine environment. All really doable (ideally) with practice and good checklists that you stick to. You always have to fly the plane and not just be along for the ride, but perhaps just moreso with TSIO engines.

[JamesC]

One more thing - nowadays most of us have EDM 760's or 960's. They tell you what the CHT cooling rate is and it gives you an alarm if > 50 deg/min. If you are foolish enough to think you can descend at 195 KIAS and impress your friends then at least the monitor will let you know you are being very unkind to your engine. Much better to not let things get cold under the cowling. Also in winter in descent you can freeze the air/oil separator can that the TSIO's have or the breather tube and end up pressurizing the case, then blowing the seal, which has caused engine failures in many different types of acft. In acft that fly in colder conditions you often see this can and the breathing tubes insulated, with holes drilled or notches cut before the cowling interface to let liquid water out and minimize the chance of this happening. Keeping things nice and toasty with slower descent rates and proper engine management still however remains safe and smart.
So with the TSIO 360's, if you have the right engine monitoring equipment it is easier to ensure that the engines remain much more durable and dependable than in the olden days.

[JamesC]

Single engine service ceiling numbers are attached for a 1971 (non-turbo) Skymaster. Just to illustrate as an example, today it is +70 deg F at Sedona airport (4830 ‘ asl) and say an engine fails at max gross after take off. In a turbo model you will be climbing at ~ 240 fpm. According to the attached table, in the 1971 model you will have to descend. Obviously those who fly the non-turbos already know this. This also implies that say it is 80 deg F and humid, you will be lucky to maintain even 4000 feet at max power if an engine fails. Anecdotes re turbo vs non-turbo are entertaining, but the only anecdote that really matters is the one that you got yourself into when those Swiss cheese holes line up.
So like anything in flying you have to weigh the pros and cons (for turbos cons include the weight, the cost of maintenance/repair/overhaul, you have to be more careful with MP settings and treat them right, and it’s another thing that can fail in flight), and make your choice. Personally I chose turbo for all the reasons in the P337H tables attached earlier.

[YankeeClipper]

Originally Posted by JamesC

Just to illustrate as an example, today it is +70 deg C at Sedona airport (4830 ‘ asl).

Yikes ... sure hope that's a typo.

[JamesC]

Fixed it thanks for your feedback.