Peter c'mon, you're writing to other pilots here. Ofcourse it's TAS. :-)
Pipistrel claim a "typical" cruise speed of 202kts at an undefined altitude on their website. Given the choice of engine which is normally aspirated one could assume that they're quoting around 8000 ft.
Just for comparison, a Lancair Legacy with fixed gear and the same engine, IO390 producing 210 hp, has a quoted MAX cruise speed of 186 kts at 8000 ft. And that's at 1000 kg gross weight.
Pipistrel have managed to create a machine that is larger than the Lancair, weighs more yet with the same engine cruises some 20-25 kts faster all day long. It doesn't compute. Lancairs are known for their petite airframes, like an italian shoe, so any improvements over their aerodynamic achievements (drag especially) are nothing short of unbelievable.
To add further insult, Lancair claim their speed at 11.5 gph. So, Pipistrel have managed to squeeze this performance from less power essentially. Wow, I've gotta see this!
Ok, I'm skeptical...
FL140, 160KTAS at 9.5GPH
This is reasonable.
Looking at some flights last year...
FL120 TAS145 9.5GPH 2400RPM +1C
FL120 TAS146 9.5GPH 2300RPM +4C
FL130 TAS150 10.4GPH +2C
FL130 TAS147 10.0GPH 2400RPM +4C
FL140 TAS155 11.0GPH 2575RPM +3C
FL140 TAS145 9.6GPH 2400RPM +3C
The Panthera is much lighter and has a much smaller cockpit cross-section.
What is striking about 2012 are the temperatures - usually ISA+10 or more.
I can live with switching to AVGAS for high temperature operation
Is there a temperature issue? I thought that Mogas had an altitude issue. 91UL will be as good as 100LL for all this.
Pipistrel claim a "typical" cruise speed of 202kts at an undefined altitude on their website. Given the choice of engine which is normally aspirated one could assume that they're quoting around 8000 ft.
I don't think you can assume anything. As a pilot myself ;) I would have never allowed such an unqualified statement to go into a sales brochure.
Pipistrel have managed to create a machine that is larger than the Lancair, weighs more yet with the same engine cruises some 20-25 kts faster all day long
Retractable gear?
I think "we" are conditioned to thinking it makes little difference, but most of the clear evidence for that is at low speeds - say 120kt. At these higher speeds it will make a huge difference. Admittedly the TB20 gear has no cowlings but I lose 20kt the instant I drop it. I recall from a PA28-140 POH that cowlings are worth about 7-10kt and that is at about 100kt. The gear could easily be worth 20kt+ at a TAS of ~ 180kt.
Even a VHF antenna is worth best part of 1kt and this has been tested. Socata have quite detailed figures on this. It HAS to be a complete lie for e.g. Cirrus to claim the 3 legs cost them just 5kt.
I guess Pipistrel will lose a few kt on the way, especially if they add an ADF etc (which they must, for IFR approval). Unless they hide the antennae in the composite e.g. in the vertical stabiliser.
Looking at some flights last year...
You don't have an ADC (airdata computer), do you? How do you reliably determine TAS then? Ever since I got an ADC, TAS is all I look at and IAS is only used for Vref during landing etc. Calculating TAS from IAS is non trivial.
I can live with switching to AVGAS for high temperature operation
Is there a temperature issue? I thought that Mogas had an altitude issue. 91UL will be as good as 100LL for all this.
I dimly remember something about many aeroplanes not being mogas certified above 20C due to vapour lock issues - maybe this isn't a problem if the fuel system is designed for it from the start. Does anyone know what the low temperature performance of Mogas is like (presumably the ethanol actually helps here...).
I think "we" are conditioned to thinking it makes little difference, but most of the clear evidence for that is at low speeds - say 120kt. At these higher speeds it will make a huge difference. Admittedly the TB20 gear has no cowlings but I lose 20kt the instant I drop it. I recall from a PA28-140 POH that cowlings are worth about 7-10kt and that is at about 100kt. The gear could easily be worth 20kt+ at a TAS of ~ 180kt.
I'm with Peter on this. Even on the TB10 the wheel fairings make a 9 knot difference (when flying around 120KTAS). As we all know, parasite drag is more or less proportional to the square of your speed, and the force required to overcome the drag is proportional to the cube of your speed. Working from this, the drag is about 30% higher without wheel fairings. If we apply the same drag change to an aircraft going 180KTAS, we gain 16.5KTAS.
You claim a drop from 145 to 125 when lowering the gear. This about about a 60% increase in the drag coefficient - which for a 180KTAS aeroplane equates to 210 KTAS after raising the gear.
I would guess that the difference in speed between the TB10 with wheel fairings and the TB20 with gear up would give a good indication of the difference between a cirrus with and without its nicely streamlined gear. Peter, if you raise the gear at 110 KTAS in level flight, how fast do you go with the gear up?
Issues above +20C make Mogas as useful as a chocolate teapot, surely?
Much of southern Europe can be +35C in the summer.
You don't have an ADC (airdata computer), do you? How do you reliably determine TAS then? Ever since I got an ADC, TAS is all I look at and IAS is only used for Vref during landing etc. Calculating TAS from IAS is non trivial.
I have the adjustable subscale on the ASI.
I have also done the 3-GPS TAS check of the ASI. It is within 1kt.
This vapor lock issue can be overcome by fuel pumps. If it was such an issue, then there wouldn't be STCs for Mogas. I have a Mogas STC on my C172M (which only has one fuel pump) and it's problem free.
There is so much BS about Mogas out there, how it destroys your engine, causes vapor lock, detonates, freezes, kills the bearings, etc. Fact is that it's much better for the engine that the nasty lead sludge called AVGAS.
The Panthera uses the IO390 which pumps back heated fuel to the tanks.
I guess Pipistrel will lose a few kt on the way, especially if they add an ADF etc (which they must, for IFR approval). Unless they hide the antennae in the composite e.g. in the vertical stabiliser.
Here's hoping they don't have to... Given EASA's protectionist certification department (see the Robinson R66), maybe they will find a way to drop the need for an ADF in a European aircraft.
Still, DME, 2 * VHF, ILS and 2 * GPS antennae must come to a few knots. Putting the VHF antennae behind one of the leading edges would get in the way of deicing, but maybe the flat GPS antennae can be hidden (at the cost of future upgradeability).
if they add an ADF etc (which they must, for IFR approval).
Why would they have to add an ADF? Have you ever seen a Cirrus with an ADF?
Still, DME, 2 * VHF, ILS and 2 * GPS antennae must come to a few knots.
There are combined antennae, like VHF/GPS in one.
Why would they have to add an ADF?
Its still debatably required equipment in many places. Also, for anyone wanting to use their own plane for IR training in Europe, it is a de-facto requirement.
Have you ever seen a Cirrus with an ADF?
Yep, horribly ugly thing hacked into the panel.
Its still debatably required equipment in many places. Also, for anyone wanting to use their own plane for IR training in Europe, it is a de-facto requirement.
Backwards as Germany might be in many aspects, ADF is unheard of in modern aircraft and not a requirement for IR training. I had a hard time convincing the avionics company not to rip out the ADF during the last panel update.
Although the clothesline antennae are somewhat cool. 
