Primarily for general aviation discussion, but other aviation topics are also welcome.
User avatar
By marioair
#1712526
With a fresh IR I’m toying with the idea of my next aircraft having a turbo

How / what should you consider, say for a PA32R versus the T variant.

1) assume it’ll never make it past TBO? Is this true?
2) assume overhaul costs more?
3) what other regular maintenance costs should be factored into static or hourly rate?
User avatar
By Rob L
#1712540
Ask yourself:
1. What does a turbo do to a normally-aspirated piston aircraft engine?
2. At what altitude does a turbo-charged piston aircraft engine benefit from being turbo-charged?
3. Now often are you likely to be up there?
4. Do you have portable oxygen to be at that height?
5. Do you have an airways-capable licence and aircraft?
6. How much money are you willing to pay for the installation, servicing & maintenance of all of the above?

If you are happy with your own answers to those, then go for it!

If you can't, then don't.
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By Chris Martyr
#1712547
Hey Mario . What RobL says .

And the answers to any other possible questions you can come up with , will be :

Yes
Yes
Yes
Yes
Yes

,,,,[and yes]

If your flying requirements tell you that you need 'a turbo' , then by all means , go for that option .

If you're doing it to impress your neighbours , then don't !

Engines are fitted with turbos for different reasons , whether it be a a diesel looking for low end torque , a small capacity petrol engine looking to be a screamer .

You can achieve climb performance with a VP prop , same thing with cruise performance . But it mostly depends on the level that you're planning to doing this .
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User avatar
By marioair
#1712549
Rob L wrote:Ask yourself:
1. What does a turbo do to a normally-aspirated piston aircraft engine?
2. At what altitude does a turbo-charged piston aircraft engine benefit from being turbo-charged?
3. Now often are you likely to be up there?
4. Do you have portable oxygen to be at that height?
5. Do you have an airways-capable licence and aircraft?
6. How much money are you willing to pay for the installation, servicing & maintenance of all of the above?

If you are happy with your own answers to those, then go for it!

If you can't, then don't.


Based on my existing steed (PA32 non turbo):

1) get me into airways more Quickly
2) above about FL120
3) fair point
4) yes
5) yes and that’s the bl***dy point of the OP
6) that’s what I’m trying to figure out by the post!
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User avatar
By Rob P
#1712557
Hello. Day, VFR, normally aspirated pilot here.

I'm trying to understand this post.

I have spent lots of time in the airways of late (RHS in a Lance) at FL110 and environs. You say the turbo brings a greater rate of climb, and then suggest you can negate that time saving by climbing higher and then having the complications of oxygen provision.

Where's the benefit that you see ? :scratch:

Rob P
Last edited by Rob P on Tue Aug 13, 2019 10:06 pm, edited 1 time in total.
User avatar
By marioair
#1712569
I’m just throwing around the idea to see what the cost - benefit is. So I was hoping for some constructive input on the cost which I’ve not had yet! :)

If I was planning a trip above FL100 I wouldn’t want to do this for a long period without o2.
Also, if the better option was FL130 or above either because that’s where the CAS is,
or the wind is more favourable,
or it keeps me VMC on top/less turbulence,
or (with caution) keeps me above cloud in icing conditions,

then it’d be nice to have the option. My current a/c. Runs out of puff at about FL110/120.

Of course, if that means an extra £x/hour I’m in, if it’s say £5. If it’s £50 then no.
User avatar
By TheFarmer
#1712570
As an aside,

I once took my Luscombe to 11,000 feet with a Continental A65....! Could have done with a turbo! The last 1,000 feet took me 15 minutes!

There was ice on the wing struts and it stopped climbing at full power. :D

I was wearing a T-shirt, shorts and loafers, and I’ll never forget how cold it got up there. 8)
User avatar
By Miscellaneous
#1712579
marioair wrote:I’m just throwing around the idea to see what the cost - benefit is. So I was hoping for some constructive input on the cost which I’ve not had yet! :)

I'm inclined to think that is maybe due to how you have worded the question in focusing on the cost of a turbo. It's an over simplification to my reading. Seems to me the major cost considerations in a new aeroplane to fit your needs are not in fact in the turbo, but in the other systems which a turbo aircraft you are considering is likely to be equipped with? :D

Which I'm sure you are aware of, but maybe not fully considered in posing the question?
User avatar
By marioair
#1712588
I’m in the market anyway for a “better equipped” aircraft. For the price range / type I’m looking at, some come with a turbo as well, hence that’s what got me thinking.

FIKI I have ruled out.
User avatar
By Awful Charlie
#1712608
Like so many things, it depends on your "mission" profile, and which airframe/engine combination you end up with!
Many NA (Normally Aspirated) travelling aircraft (eg TB20, Ovation, Bonanza) can easily climb into the mid teens without a problem, and generally have a service ceiling around FL200, limited by rate of climb. Adding a turbo does keep the climb going at a better rate for a somewhat higher ceiling, normally limited by certification HPL to FL250 (although for a period some were certified to FL280) and allows a higher TAS, which can be useful in some situations: eg Terrain avoidance, weather avoidance, strong tailwinds etc. However, almost certainly you will burn more fuel - you can maintain high power settings (and hence higher fuel flows) for the whole climb, (and you don't get all of this back in the descent) and while in the cruise: a higher TAS demands more power and thus fuel - you can for sure turn down the power and fly at NA speeds, but in that case why carry a turbo? If you do a lot of low level stuff, you could well find that your fuel burn is actually *more* than the corresponding NA airframe - turbo engines typically have a lower compression ratio than their NA equivalent, the expected use being that the turbo then raises this back to near NA equivalence by doing some of the compression outside of the cylinder - if the turbo isn't doing much work then the effective CR is low, and consequently the fuel efficiency drops off.

If your trips are sub 2 hours/300nm ish, unless you have significant terrain, I would suggest you're not going to get enough to make a turbo option worthwhile - even at 400nm it will be marginal (of course, just ballparks, and very type specific) - a climb and descent to FL200 while keeping engine temperature under control will probably be in the region of 150-200nm. That said, there can be a few places where >FL200 is useful (eg overflying Paris, or when there are much more suitable upper airways than lower), and the amount of traffic in level flight between FL200 and 250 is relatively small compared to above and below

The turbo itself doesn't normally add to much to maintenance - if you budget for a new turbo(2-5k) at mid-life of the engine that seems to be about normal from my experience and conversations, but it is very type specific and also depends on how you operate the engine. Remember with a NA you are hard pushed to do engine damage over 5000' or so - with a turbo you can catastrophically damage the engine all the way to critical altitude plus a few thousand feet. You also get a bunch of additional dependencies - if any one of the turbo, waste gate, controller(s) or hoses fail, then you get an un-flyable aeroplane. Depending on the type, there may be expensive requirements: on mine the exhaust clamps can only be used twice, but the exhaust doesn't need to come off at a scheduled inspection - if it had to be removed eg at annual then it would add another 600bucks for parts, plus the labour, every year. You really don't want to skimp in this area - the turbo can literally become a blowtorch under the cowling if things come adrift, and that sort of failure has killed aircraft and occupants in the past.

Where the costs start to ramp up is that with a turbo and its capabilities, you start to need more 'stuff' to use it effectively - eg oxygen consumption approximately doubles from FL130 to FL200, so one small bottle is no longer enough, without a de-ice or anti-ice system you may get trapped by a layer, you start to want a sferic/radar detector to avoid build ups without massive climbs and descents, another horizon with a different power source (which is likely a battery with a replacement schedule), and then a second alternator, and so the list goes on. It's the maintenance of all these that adds up, and likely to more than the cost of just the additional turbo maintenance. With the change in fuel burn your cost index will probably not change a great deal, just both factors are a bit more and you get to choose from a wider range!
To answer the specific questions:
1) assume it’ll never make it past TBO? Is this true? Not necessarily, I did a factory reman at TBO+10%
2) assume overhaul costs more? Compared to NA, almost certainly
3) what other regular maintenance costs should be factored into static or hourly rate? Depends on the extra 'stuff' you go for
User avatar
By marioair
#1712615
Bill McCarthy wrote:Have you got money to burn ?

does it improve the compression ratio? :-)

playing a small violin i know, but basically, looking for a newer PA32R. Hard to come by a good one, and the ones that are for sale have a Turbo. So trying to see if i take the plunge or not
User avatar
By Paul_Sengupta
#1712617
Bill McCarthy wrote:Have you got money to burn ?


All of us who fly do....

And those of us who drive for that matter. Except those who drive electric vehicles, who have money for someone else to burn.