I guessing I’ll see two or three Wankel powered cars on my home tonight. Too bad Mazda stopped them recently – I wouldn’t mind having a late model RX8 because they are a practical car and not too expensive. For aircraft they would be OK in some applications but what we have now is overall better and the development effort that might’ve come in the 70s wasn’t pushed hard for that reason.
Too bad Mazda stopped them recently …
I know it exists, but I can’t remember ever seeing one of those in Europe. But recently I saw a beautiful specimen of the grandfather of all Wankel cars, an NSU Ro80, dating from around 1970. I had a brief chat with the owner and he told me that his is one of the very few surviving Ro80s that still has the Wankel engine. Most were refitted with a VW Golf engine at some point because the Wankel had a typical life of 10.000km…
Mazda has produced about 1.8 million rotary cars. After decades of development they are as reliable and long lived as anything else.
I’d have to say that it is a bit far fetched to say the current Diesels are still unproven designs. The one bit which was unproven was primarily the business model of the original Thielert manufacturer, but the engine itself became quite sound after a few issues were resolved very early on. After more than 10 years of Diesel experience, these engines are pretty much known quantities, actually there is a lot more operating experience than for the IO390 for starters.
I agree with Achim and others here that with the move to a large avgas engine the Panthera has lost much of it’s appeal to many of us who know the business and what is around. But it is abundantly clear what happened if you look at the updated tech spec page posted by Pipistrel. In short, the IO390 did not deliver the “bragged” speed and they decided they could not have that. So now they bumped the IO390 to the experimental version of the Panthera while they are also indicating fantasies about a “hybrid powered” variant with a “soon to be developed” powerplant. Actually, I never heard of any such engine avialable so far..
The figures are pretty clear but there is still a LOT of marketing inside which have to be taken with a medium size salt pitcher.
The IO390 powered Experimental first:
For an MTOW of 1315 kg they claim a usefull load of 545 kg. With full fuel this means 394 kgs for crew, pax and bags. That figure is pretty neat but remains to be verified. It would make the plane a “true” 4 seater.
Performance: They now claim 181 kts @ FL080 as max speed, 173 kts as 65% and 155 at “the cruise which makes it go 1000 NM”. Only it doesn’t, or at least not with reserves. My trusty calculator gives it about 650 NM at top speed, 800 NM at 65% and 890 NM at “1000 NM speed” based on Lycoming consumption charts of 12 GPH/75%, 9.2 GPH@65% and 7.5 GPH at 55%.
Now: That are not bad figures at all for a 210 hp airplane but it is egg in the face of the marketing crowd who said 200 kts and 1000 NM range, for sure! Also they claim FL200 as the max level with that engine. Having seen a DA of over 20k in my 180 hp plane I hesitantly believe that.
The certified version with the IO540 looses 50 kg of payload. Still, 348 kg is not bad for a 4 seater at full fuel (55.4 USG useable).
Performance: Now the reason for the engine switch becomes clear, they now claim 198 kt @ FL080 Max and 193 kt @ FL120 and 65%. These are great speeds, but given a final reserve of 9 USG (45 min cruise) and 8 USG to climb to FL120 as well as 15 GPH@ 75%, 13 @ 65% the range drops dramatically to about 500-550 NM. They indicate the same “1000 NM with 4 people at 155 kt” but heaven knows what power setting that is, must be in the 45% range or so which then would give around 9 GPH fuel flow and I only get 600 NM range for that and this at speeds widely available in many planes with smaller engines and lower consumption. They do claim FL250 as the max altitude for this engine which, seeing that it is not turbocharged, I find doubtful.
Full table here: Link
Now from where I am sitting, they had themselfs a neat little speedster with a great payload using the IO390. But physics caught up with them and it did not deliver what the modelling said it would and what marketing told everyone so the decision was to get it to 200 kts at all cost. Only, that cost in my view is way too big. The original design with it’s 170-180 kt / 800 to 900 NM range still is a damn attractive airplane, considering it can use MOGAS and has a neat payload. Who however wants to fly an airplane which burns the same fuel in realistically 550 NM but is 20 kts faster? There may be some but I would not be one of them.
Looking at that, the decision to upgrade the engine in my view is wrong in all regards. To make the IO540 powered Panthera a viable airplane, they would need to massively increase useable fuel to about 85 USG useable to reach their 1000 NM target, which then reduces payload to about 250 kg, that is 2 plus bags or 3 without. That is not shabby, but on the other hand also not exactly new.
Frankly, I think there is still too much marketing and face saving going on there and I don’t think it is going to go down well in the market place.
(Diesel?)
I ran figures for the SR305-230E Diesel as much as I could find them. Now that engine produces 230 hp. Cessna claims a consumption of 9 GPH @ 75% and 6.6 GPH @ 65% (SMA does not offer any figures I could find) plus a MTOP Figure of 12 GPH (Max take off power).
The SMA is about in the same weight class as the IO540. Jet A1 is however heavier than Avgas, so full fuel payload would be around 330 kg. If I assume the same speeds (and actually it might be a bit better due to the 20 extra HP) I am seeing ranges of 850 NM @ 180 kts (75%) or 1100 NM @ 175 kt (65%) or 1300 NM @ 155 kt (50%). Now how close is that to the original spec?
Possibly the SMA is too expensive or there are other reasons. But it would have been a better solution than simply brute force the problem by a larger avgas engine.
My 2 cents.
I’d say the Thielert is not so much proven as disproven 
For the majority of potential buyers, It remains an exceptionally expensive engine to operate when compared with others in its power range that are simpler, more robust and supported by the GA industry and not just the original manufacturer. The SMA on the other hand will begin to be proven when the first one has been supplied to an airframe manufacturer and in turn to their first SMA equipped retail customer. Subsequent to the engine failure on their prototype, Cessna has AFAIK delayed their SMA C182 program without any indication of when, or if, it will be resumed. Does anybody have any better information than that?
Diesels are an aspiration for those who would like to fly long distances in what amounts to the GA version of the third world, where no fuel distribution infrastructure exists. I can certainly relate to that goal as I’d like to do it myself. However, I’d maintain that the better route in achieving that end would be auto fuel certification, and in fact conversion of the European GA scene in its entirely to auto fuel including high power engines. For aircraft, I think the performance and simplicity of gasoline powered engines is fundamentally better and I don’t see that changing. Pipistrel apparently agrees, and I think the marketing problem they have is that the kind of people who will actually step up and buy a Panthera are likely to be a few dilettantes who are not afraid to spend money on image without corresponding value. I think satisfying the desire of those people to appear cutting edge while actually taking the best technical course is a challenge.
It remains an exceptionally expensive engine to operate when compared with others in its power range that are simpler, more robust and supported by the GA industry and not just the original manufacturer.
You assume that avgas availability and cost is comparable to jet fuel. That assumption is wrong except in one small part of the world which you happen to live in. You can call the rest of the world 3rd world if you wish…
where no fuel distribution infrastructure exists
There is fuel distribution infrastructure worldwide and it’s for jet fuel. If it wasn’t for the short period after WW II where GA was fashionable, there wouldn’t be any avgas infrastructure anywhere given that commercial users have moved off avgas years ago and only the private pilots remain on it and that is a rapidly shrinking group, even in the US of A.
The solution in North America is going to be 100UL, but in Europe and elsewhere it appears to me that availability of that fuel is not going to be any better than it currently is for 100LL. However, Mogas is available almost everywhere in the world. Given my observation that Mogas can power better performing, simpler engines than kerosene, I can’t see a reason not to use it. The fuel efficiency issue does not appear to be all that compelling. To me this appears doubly valid when considering the obvious problems with making a practical diesel aero engine, and the obvious commercial reality that most of the world’s current GA market won’t be buying diesel aero engines regardless.
Jet fuel is no cheaper as far as I know than auto fuel, and I don’t see a tax dodge as being the right underpinning for any fundamental technical shift.
That’s just where the facts drive me – I didn’t make the facts.
100UL will be the European solution also.
The avgas market, just in Europe, is worth hundreds of millions of euros a year. That’s big enough for serious players and this is why avgas is still here despite various people posting on forums that avgas is finished and everybody who makes it actually hates making it and is waiting for the first chance they get to stop making it. Yeah, right
I too think the Panthera didn’t reach the originally published performance figures, but (as I wrote before) I think dropping the IO390 also happened to solve some other problems which appeared (from the Lycoming end of things) since the IO390 was originally chosen.
The payload looks very good. The TB20’s payload – which is among the best for an IFR tourer, especially such an efficient one – is 500kg, minus 235kg for full fuel.
Avgas is OK in Europe. Sure, you can’t fly around in a C152 around Greece (unless you fly circuits around Megara) but there is a simple solution: don’t buy a C152.
Outside Europe avgas is hard (for long range touring; there is plenty of avgas within Africa, for shorter runs – my AIR BP handbook shows an amazing amount of the stuff down there) but almost nobody from Europe wants to fly outside Europe anyway, because of the distances, bad infrastructure, violence in many places, because you need permits for every damn flight, etc.
Fuel pricing as read of the web today in Switzerland were as follows (per Liter including tax)
Avgas 100: 2.70 CHF
UL91: 2.40 CHF
Jet A1 : 2:09 CHF
Mogas 98: 2.04 CHF
These prices vary from airport to airport but the relation is about the same.
Now take the situation with the Panthera.
We showed that at 65% power the IO390 will use 9.2 GPH Mogas @ 173 NM, that is 71.30 CHF p.h or 41 cents per NM.
We showed that at 65% power the IO540 will use 13 GPH Avgas @ 193 NM, that is 132.70 CHF p.h or 78 cents per NM.
We showed that at 65% power the SMA will use 6.6 GPH Jet A1 @ 173 NM, that is 52.14 CHF p.h. or 30 cents per NM.
You can convert that into Euros or Dollars but I think it does show roughly what the story is. If you extrapolate this for a yearly fuel cost with 100 hours per year, a Panthera with an IO390 will cost 7’130.- for fuel, one with a IO540 13’270 (almost double), and an SMA powered one 5’214 CHF.
And if we are talking only fun flying, not enroute: A PA28-140 or Cessna 172 with Mogas STC will have a fuel cost of about 60 CHF per hour whereas one without Mogas will cost around 80 CHF. That is a whopping 25% reduction if you can use Mogas. An Austroengine will burn around 5 gph or 40 CHF per hour. (same for the Centurion but I could not find any overhaul data for it).
So if someone has an Austroengine, he will spend 40’000.- CHF per 1000 hours, a O320 with Mogas STC owner will spend 60’000.- per 1000 hours if Mogas can be used or 80’000 CHF per 1000 hours for Avgas.
Or if we go by TBO/R:
An Austroengine has a TBO of 1500 hours, so that is a total sum of 60k CHF. TBO price is 15’600 CHF.
An O320 has a TBO of 2000 hours 2000 hours, so that is either 120k for Mogas or 160k for Avgas, or if we want to compare directly, 90k/120k for Mogas/Avgas and 1500 hours. TBO price is around 25 k CHF.
Never mind all this is Swiss Francs, but the relation can be seen brutally I think, even if these are only very rough estimates. That is why I am aware of quite a few converted club planes which use Centurions or at least have converted to Mogas wherever possible.
So yes, the fact that the O390 has Mogas capability is of quite a vital importance in the European market.
Why on earth would I buy a IO540 Panthera instead of a Cirrus SR22? And this is assuming I am a wealthy-only-buy-new guy. In reality I would never buy a new SR22 so that makes it even worse for the Panthera because there is a large market of very nice SR22s with BRS, TKS, oxygen, G1000 etc.
The IO540 Panthera is going to be a complete economic failure, I am absolutely convinced. The IO390 Panthera was interesting, it had quite something to offer in the efficiency domain. An SMA Panthera would be even more interesting in that regard, it could show Diamond and Cessna what modern aerodynamics can do with a diesel engine but an IO540 Panthera is a solution without a problem.
