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Pipistrel Panthera (combined thread)

it will still rely on a 1950's engine up front.

That's not a problem. The SFC of those engines is better than that of any modern petrol engine.

I disagree. In level cruise at peak EGT, the SFC might be bearable but before you reach level cruise, you spend 20-30 minutes in full rich climb and that ruins your SFC.

I would never buy a new AVGAS burning airplane (not even if it's certified for unleaded AVGAS). The Panthera design is great and I would expect them to look at diesel alternatives, most likely the SMA/Continental.

In level cruise at peak EGT, the SFC might be bearable but before you reach level cruise, you spend 20-30 minutes in full rich climb and that ruins your SFC.

OK, but it depends on the flight profile.

If you just climb and then just descend, it's true that the extra you burn during the climb is not recovered in the descent.

However I have done various measurements on climbs, trying (to say 5000ft)

  • full-rich
  • the constant-EGT profile
  • peak EGT

and there is suprisingly little difference in the fuel burnt to reach the altitude. Obviously the last one takes the longest time, especially as one has to keep the speed up for cooling. The reason might be because most of the extra burn is the accumulation of potential energy but I don't know how to work that out

FADEC would not help, AFAIK, because the issue is that the engine cannot deliver max rated power at stochiometric combustion, because it cannot get rid of the heat fast enough. For an air cooled engine like the Lycos to run at stochiometric (close to peak EGT) at max rated HP, it would need a better cooling system than just air and an oil cooler. Or, of course, you could sell it as a lower power version but that would be bad marketing.

I would never buy a new AVGAS burning airplane (not even if it's certified for unleaded AVGAS). The Panthera design is great and I would expect them to look at diesel alternatives, most likely the SMA/Continental.

I don't think anybody would disagree, but the choices are somewhat limited.

Administrator
Shoreham EGKA, United Kingdom

OK, but it depends on the flight profile.

If you just climb and then just descend, it's true that the extra you burn during the climb is not recovered in the descent.

If I climb for 30 minutes and my enroute segment is 2h and my SFC in climb is twice the enroute SFC, then my overall SFC is still 20% worse. That is a lot and already accounts for most of the much better fuel burn of a diesel (e.g. SMA) which does not climb at full rich.

FADEC would not help, AFAIK, because the issue is that the engine cannot deliver max rated power at stochiometric combustion, because it cannot get rid of the heat fast enough. For an air cooled engine like the Lycos to run at stochiometric (close to peak EGT) at max rated HP, it would need a better cooling system than just air and an oil cooler.

I don't think that is true for my installation (235hp O-540) with its huge cowl flaps. I can climb quite a bit on the lean side while keeping CHT in range. The main danger is detonation and full rich is a crude solution to that. A FADEC system should constantly monitor all parameters and avoid detonation, just like car engines have been doing for decades.

Also a lot if not most aircraft cannot climb at full power and Vx or Vy.

main danger is detonation

Do you think so?

The tests which GAMI did suggested that detonation is actually very hard to achieve. They did it on a TSIO540 but had to go to a CHT of about 450F and loads of MP.

I think the main danger in climb is insufficient airflow -> high CHT -> cracked cylinders.

Also a lot if not most aircraft cannot climb at full power and Vx or Vy.

They can but not for long

Administrator
Shoreham EGKA, United Kingdom

A few points...

Cooling: In the 200 HP power range occupied by this (Pipistrel) aircraft there have been few issues with thermal gradients, cylinder cracking etc with air cooled aero engines. For decades people have been flying O-320s and O-360s at full power from takeoff through the entire flight, especially in high altitude operations with marginally powered aircraft like 172s and Cherokee 140s. They give no trouble when totally abused in that way, as they regularly are with rental aircraft. Plenty of people renting 172s think the throttle is a switch, on or off :-) The cylinder problems come with faster, higher powered aircraft that have a wider range of cooling air dynamic pressure available in normal operations and high power density. There's a reason why radial engines dominated once you get above about 350 HP.

Fuel: It is self evident to me that when you cut through all the BS, Avgas is the highest quality fuel for aircraft piston engines, and the one that will continue to power the highest performance, simplest, lightest aircraft engines. Its BETTER than car gas or kerosene, that's why it was created and why engines were designed to use it. When 100/130 transitions to no-lead, it will again be better. The anti-GA problems in Europe that are driving to market to seek alternates to Avgas are local political issues, and I don't think the GA world is going to wrap itself around European politics and tax policy. I suspect the rest of the GA world (most of which is in the Americas) will buy what works better when politics and taxes aren't so much warping the market.

The anti-GA problems in Europe that are driving to market to seek alternates to Avgas are local political issues, and I don't think the GA world is going to wrap itself around European politics and tax policy.

I think you're wrong here. There is a big political movement in the US trying to abandon leaded AVGAS but not really in Europe. Here's it's just simple economics: a small and constantly declining demand for AVGAS, high costs to ship and store it. Some months I ago I landed at a large airport in Germany where AVGAS costed 50 cents more per liter than anywhere else. I asked them why and the answer was: we are required by management to add all cost for having AVGAS onto the fuel price. It's clear where this will end, the costs are somewhat fixed and the number of liters to put them onto keeps shrinking.

Apart from the overall decline of GA, AVGAS is under attack from two sides. First of all a lot of aircraft use auto fuel these days, the microlight scene is taking over recreational flying in the Europe. I've converted my C172 to auto fuel years ago. On the other hand, everything commercial is Jet A-1 these days. Until a few years ago, Cessna 340/421, Dukes, etc. were common but they are quickly disappearing from the market.

I spend about 8 weeks a year in Germany, so I have some (although not complete) understanding of the GA situation there. Its a place where GA is seemingly dominated by the opinions and politics of the uninvolved, GA operations and GA airports are tremendously restricted by law, and fuel sales volume is tiny as a result.

Meanwhile in the US, the use of auto fuel for aircraft has pretty much disappeared in the last 10 years, and diesel aero engines hold little interest except for a (very) few dilettantes who like to be different for its own sake, at considerable extra cost. The issues are:

(1) Many aircraft (including mine)were STC'd auto fuel about 30 years ago, burned it for about 20 years, and are still certified to use it. However, US federal and state environmental regulation has dictated that you can no longer buy auto fuel without alcohol, which means that the certified GA fleet has transitioned back to Avgas.

(2) Modern auto fuel formulations smell awful, aren't available at any airport I know, and aren't a lot less expensive than Avgas. I'm paying the equivalent of 0.80 Euro/liter for premium auto fuel and 1.1 Euro/liter for Avgas. Using auto fuel would save me only about 9 Euro/hour for my aircraft.

(3) Jet fuel is more expensive than Avgas at the pump.

In time 100/130 will transition to unleaded, just as it transitioned to low-lead 30 years or so ago. US general aviation and the GA market will go on, minus drama. In Europe, I think the vast majority of flying will move to 80 HP or less, with utility GA suffering under the weight of ever more regulation and taxes. Expensive, complicated diesels may sell in Europe at great cost, affordable by few. More of the same in other words - I think its tough to fight city hall when city hall, driven by politics, dislikes you.

I reckon we will have UL91 replacing avgas, but it's hard to guess when because most turbocharged engines, or engines above 9.5:1 (most - all? - aerobatic planes) can't burn UL91.

Everybody is waiting for a "UL100"... there is PLENTY of money to be made making avgas and plenty of people make it (I don't buy into the "shortages of avgas / shortages of TEL" stuff) but nobody wants to stock 2 fuels.

Well, nobody except TOTAL who are out to make a fast buck (IMHO) on their UL91 and who are reportedly offering free bowsers to some airfields, knowing that the airfields then come under pressure to drop 100LL.

Administrator
Shoreham EGKA, United Kingdom

No question that any country that would rather tap into the country's emergency fuel reserves (or worse) rather than have petrol go over 4 bucks a gallon is at a distinct advantage relative to Europe.

However, this thread is way off topic of the OP, and folk looking to read a thread about Pipistrel's new aircraft are going to be disappointed.

So maybe I'll start another thread..."Why does the US appear to love GA, whereas Europe appears to hate it"

Looks a fantastic aircraft - and probably one I would be interested in when it has been around for at least a couple of years and some of the gremlins have been dealt with.

However, I can't see any reference to TKS, which I think is a major oversight?

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