From here
Peter wrote:
I think the best way to solve the “FL250 issue” is a Jetprop which at least does it properly (FL270 / 270kt TAS) but at the cost of a new fully loaded SR22
Sure but the cost difference between a jetprop and turbo piston machine is significant. For those of us that cannot afford or want to spend the amount a turboprop requires the turbo piston fits in nicely. You can get a lot of used turbo pistons around the 150k eur or even less whereas as used jet prop will set you back 600k eur or more. The overhaul cost of around 300k for a pt46 turbine is also out of reach for many private pilots. If you use an aircraft for local flights a normally aspirated engine is the better option. But to do travel at the flight levels a turbo is simply great. There is indeed an increase of heat on the cylinders from flying high, which might translate to higher maintenance costs. But the way I see it the turbo with increased speed/efficiency at attitude saves me some avgas at the same time, so the calculation is not that simple. Also I think If you operate it properly especially keeping an eye on CHT and TIT with the mixture and throttle back to NA manifold pressures it’s not a big issue. I was in fact looking for a TB20 amongst other planes, but ended up buying an used TB21. Now Im really glad i did so because of the turbo and the added ability from that. In fact I would never consider a travel piston plane without turbo again. I use it only for long distance IFR and the ability to get above weather most of the time also increases comfort and dispatch rate (missing Full TKS though). The only downside of flying high apart from oxygen requirement is if wind is against you it will be stronger. But often its still worth the tradeoff to get higher as the TAS is also higher for same power setting. You can always opt to fly lower of course and I sometimes do. Strong tail winds up high are great though. On the TB21 I recorded the ROC at FL220 to 500 feet although not at MTOW. The POH States 276 ft @ FL250 ISA (ceeling) which seems about right. The max MP is 27" at FL 250. I would never go higher than the certified ceeling anyway, partly because an oxygen failure becomes extremely critical. Newer airplanes I think has an hypoxia autopilot decend function built in if the pilot becomes unresponsive which seams like a really good idea.
Peter wrote:
I think the best way to solve the “FL250 issue” is a Jetprop
I do not agree because although a Jetprop is wonderful at FL250, it sucks (Jet-A1) down low. So it depends on what your goal is.
If you occasionally want to beat the weather but mostly want to fly low(ish) and enjoy the scenery, whether IFR or VFR, then a Turbocharged piston engine is the better choice. If you always want to fly high A to B IFR, frequently bringing a full load of (inexperienced) passengers, then the Jetprop is surely the better option. I do not think many of us fit that bill.
When I flew from Dubrovnik to Portoroz last August, I was more or less in formation with a Meridian at 2-3000 feet. Must have been an expensive leg for him.
THY wrote:
I would never go higher than the certified ceeling anyway, partly because an oxygen failure becomes extremely critical.
That is certainly true. Actually I find anything above FL200 kind of scary in that respect. And when you fly that high in a piston aircraft, it is usually because the weather is poor not VMC below, with risk of icing, embedded stuff etc, or terrain. So should you lose O2, descending into the crap should not be your preferred solution, and in some situations may not be an option be very unattractive – CB below being one example.
In addition to an installed system I have a portable bottle as a backup. One of my MH on-demand regulators is connected to the aircraft O2, and the other is connected to the portable bottle. In the event of a problem with one, I just need to switch my cannula from one regulator to the other, and then do the same for my passenger’s.
Welcome to EuroGA, THY 
I “buy” both sides of this debate but have chosen to go non-turbo. Instead I am installing a full TKS system, this winter.
The problem I see is reliability i.e. downtime.
Example: on any EuroGA fly-in, we get about 1/3 AOG rate. And the people who actually come to fly-ins (of any kind – even local ones) are not generally people who are exactly struggling financially. So these people are getting screwed by downtime even though they could throw some money at it. Downtime is really big in GA. I know of several of 1 year, and one specific TB21 case of 6 months with a seemingly intractable turbo issue… probably this was “monkey competence” at the Socata dealer but this is just another angle on downtime… if you had competent facilities, life would be so much easier all round. It is blindingly obvious that most GA owners do not have competent facilities.
What causes the extra downtime on a turbo?
Mainly, cylinders tend to crack. If you are lucky you discover a nice big crack between the spark plug hole and the exhaust port. The cylinder must be changed before further flight. Then you have to bed-in the rings, so it is c. 50% more avgas for say 50hrs. With a turbo you don’t have the problem of not being able to do IFR (high altitude) flights during this time, but still there is the cost.
But you know there will be more, soon. It’s like light bulbs in a load of external lights around a building, controlled from one light sensor. The result is corrosive on your confidence to do a long trip.
If, like most people, you discover this on the Annual, same thing. A top overhaul may be recommended, especially if you are over say 800hrs. 10k… and, ahem, which engine shop might you use? Europe has a dire reputation for engine shop competence.
Different people have different attitudes to downtime. It depends on the sort of flying they do, and their maintenance facilities. I have very poor facilities (no work allowed in the hangar, etc) and I fly a fair bit, say 150+ hrs a year, so I value uptime. I need a top overhaul, or really any work beyond a 50hr service, like a hole in the head.
And I have never seen any supported case of a turbo engine making TBO or anywhere near it. By “supported” I mean someone who has actually done it themselves. Very few people have owned one of these planes for more than a few hundred hours.
A TB21 with full TKS is a very capable FL250 2-seater. Sometimes I could really use one, but overall it doesn’t worry me much. The GT is also very rare.
I have two 1st stage regs and two O2D2 regulators. I also travel with two O2 cylinders although the 2nd one is not normally reachable in flight (I carry it in case of a leak while parked).
Personally I would take a turbo over TKS for long distance touring (excluding turbine of course). The options it provides are significant and you don’t just get a higher ceiling you get much higher ROC at altitude. Yes you need a good O2 option and you will spend more on your engine but it is worth it IMHO.
@JasonC wrote:
much higher ROC at altitude
Is it really significant ?
I can understand that jet performance ROC at altitude, combined with radar, will allow him to climb through (very) nasty weather (CB). But we are speaking about 2500-5000ft/min range, aren’t we ?
A turbo piston will do 600ft/min over 100ft/min (NA) at altitude, and except for PA46, won’t have weather radar. Will he penetrate embedded CBs area with this argument only ?
PetitCessnaVoyageur wrote:
A turbo piston will do 600ft/min over 100ft/min (NA) at altitude, and except for PA46, won’t have weather radar. Will he penetrate embedded CBs area with this argument only ?
Well that is quite a big difference. I don’t think it has anything to do with penetrating embedded CBs. It is about providing more options re weather in particular going over the top. Let’s say you need a 2000ft climb. You can do it in a 3:20minutes vs 20 minutes on your numbers.
pmh wrote:
In this league where a range of AVGAS turbos can go to 25.000 feet is it a problem / downside that the DA42 can only go to 18.000 ?
It isn’t a problem, but that is quite a meaningful difference. There is often weather below FL200 that you would top at FL250.
JasonC wrote:
Well that is quite a big difference. I don’t think it has anything to do with penetrating embedded CBs. It is about providing more options re weather in particular going over the top. Let’s say you need a 2000ft climb. You can do it in a 3:20minutes vs 20 minutes on your numbers.
If he has deicing available and weather is not convective, sounds to me a matter of being patient.
But I may be completely wrong.
Differently, turbo higher ceiling will offer the option to go over, where the NA will be stuck into IMC.
Is it really significant ?
The difference lies in how long the aircraft will be exposed to icing conditions which may screw up climb performance altogether. And it reduces the exposure to turbulence when you climb in IMC. And when you get on top you still have 75% power or more for cruise and better margin to stall.
Nobody will climbs through CBs no matter the rate of climb.
Aviathor wrote:
Nobody will climbs through CBs no matter the rate of climb
Aviator, you’re exaggerating… I meant between !
Let’s say this, minute 5
Aviathor wrote:
better margin to stall.
Agree with that. Especially with mountain waves.
PS: speaking about margin to stall at altitude… I may have found my poor man turbo
https://microaero.com
Don’t mean to be controversial… As said by seo earlier, I am sure Turbo is much more confortable, and makes IFR flights easier
PetitCessnaVoyageur wrote:
If he has deicing available and weather is not convective, sounds to me a matter of being patient.
In a NA aircraft picking up ice, patience is not something you can really afford to have.
