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Raptor - 300kts, 130k usd, 7gph jet-a1

Definitely, Cirrus did a super marketing job on the target audience (which is mostly in the USA – the bulk of the GA market). Apart from the application of the BRS to such a “large” airframe (previous BRS uses have been on much smaller ones, mainly some “very evidently flimsy” types) it is a non-innovative aircraft. Well, there is the removal of the prop RPM lever But a lack of “risky technology” was also a great selling point – the IO550/TIO550 is a proven power plant, respected in the prime market (notwithstanding the ritual slagging off these old engines get in Europe, but Europe was not Cirrus’s prime market, and European attempts to make use of “intellectually superior” car engines have been originally a disaster). So one has to get the whole package just right. Too much innovation will kill it, too.

To me, one big Q is whether the BRS is really necessary for a new design to succeed. It is tempting to roll out the “wife demands it” argument (which is valid – I have heard it off-forum countless times from SR22 owners) and it is quite possible that that is necessary to sell thousands like Cirrus have, but I think we just don’t know the answer for smaller numbers, because there is no supporting data. The Cessna 400/TTX – a design at least as good as the SR22 – failed abysmally, but then Cessna’s marketing was dreadful… even worse than Socata’s. Diamond are not big in the USA, too, especially not in the touring sector. But anyway the Raptor says it will be available as an option. In this context, perhaps Cirrus’ smart move was to make it non-optional, which had two benefits: (a) easier certification and (b) it conceals the payload penalty which very cleverly removes the “wasted payload” debate from any social media discussion.

The other big Q is whether the car engine is too much of a risk. I think it is, and almost nobody who is informed about the history of car engines in GA will commit that much cash. Just to pick up a small point: car engines are so very reliable not because of some magic build quality or magic clever design, but because a car engine spends most of its life pottering along at some 20-30% of max rated power. Car engines used in competition get shagged really fast but nobody cares because motor racing sponsorships bring in so much money.

I don’t doubt that 230kt at FL250 can be achieved and you could do it with a TIO540 or similar (with a big enough turbo).

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

I don’t doubt that 230kt at FL250 can be achieved and you could do it with a TIO540 or similar (with a big enough turbo).

That’s not what they’re claiming. The homepage says 300KTAS @ FL250 with 11 GPH and 230 KTAS @ FL250 with 7 GPH Jet A-1

Last Edited by mh at 05 Oct 15:29
mh
Inside the sky.
EDXE, EDXF, Germany

Must be very slippery, maybe..

As a comparator, the DA62 WILL give about 190kts at FL200, burning Jet at 14USG/hr. For sure, the Raptor probably brings a bit less drag but 100kts+ with 60hp less. Hmmmm.

Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom

That’s not what they’re claiming

They do claim the figures I posted, and my drift is that they will have problems with the diesel engine, and will end up sticking one of the proven ones in there to keep the project moving forward.

Must be very slippery, maybe

There is very little about subsonic airflow that isn’t known already…

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

To me, one big Q is whether the BRS is really necessary for a new design to succeed.

I think the market has shown that. How else would Columbia have failed? It was the much faster airframe. Or why don’t Mooneys sell in figures? They are cheaper than the Cirrus, they are faster than the respective counterpart and they are much more economical.

Cirrus is the ideal package for the standard family of 3 or 4 and the decisive factor is a) the horrified wife and b) the undisputable fact that in 99% of the cases the shute will eliminate the need for a 2nd engine in night/imc conditions as well as for a 2nd pilot. It really is that easy.

When Mooney brought out the M10 design, the hubbub was huge until they said it won’t have the shute. That was the end of the project noboday talked about it anymore. And it would have been a great airplane with true game changer potential.

LSZH, Switzerland

The Cessna 400 had loads of problems in the early days and these blighted it, and then Cessna more or less abandoned it for a few years. As for the Mooney, we have already had this thread and old-timers here will remember what happened there, and I am grateful to see EuroGA in a period of relative peace; long may it last

Administrator
Shoreham EGKA, United Kingdom

Just to start with – the Audi/VW 3.0 V6 TDI in a car needs an ECU update for mountain operations, because the parameter mapping does not work well above 2500m. So I guess above FL100 they have to develop a totally new mapping and design a brand new ECU – at that price tag? Further, it needs electricity, which is a (kind of avoidable by backup) problem. Further, as compression self ignited engine it has no restart capability above what, 8000ft? Talking of Diesel fuel for these altitudes? My bet, it won’t happen.

Last Edited by at 05 Oct 18:02

I stand corrected. Indeed I have heard Peter (the project owner of the Raptor) say he is a pilot. Apologies.
I continue to follow his amazing videos on Youtube – learning a lot – he is really a genius allrounder and a tough worker. Hat off.

Through one or two comments I have tried to inject some words of caution about

- Relying on glue to hold the windshield (in fact all windows) of a pressurized aircraft in place. This mistake was a primary cause of the demise of Evolution Aircraft.
This is now at least partially fixed. Some bolts have been added, but nowhere near what Extra put in the 400 for example and the issue of gluing together parts which such radically different thermal expansion coefficients remains. Add thermal excursions and pressure and I can very well imagine the plexiglass exploding from internal stress.

- Also suggested that he should proactively address the issue of his “homemade” engine’s operation at altitude.
This is a totally exotic (for aircraft) cascade twin turbo setup. This may make sense in a car, but it doubles the number of points of (full) failure and multiplies complexity by 4…
Setting up the ECU and sorting out the gremlins will take many flights to FL250 – taking into account the practicality of such flights, I believe this alone will waste years and fail based upon the simple observation that several competent and generously funded big players have had never ending trouble…
I think that he will eventually revert back to a commercially available engine such as the big FADEC Lyco or one of the new diesels.
Doing so right now would save a lot of cost and time. But it would make the targeted price point unachievable.

- made him aware of the unpleasant cascade effects when flying this high: lose the engine at FL250 and you now have a pressurization issue to deal with first.
The prototype will (need to ) routinely lose its engine in high altitude tests and good luck with restarting a turbocharged diesel at altitude…

- recommended that he focuses on getting the basics right for the prototype and only then develop peripherals that will get in the way of the redesign work…

A peripheral topic is that somehow people designing composite aircraft seem to apply structural schemes copied from the metal era, resulting in unnecessarily heavy airframes. If anything this is where I would have wanted the Raptor to innovate.

I know of at least three isolated designers who took the opposite direction with convincing results:

David Algie who designed the LP1 (and stopped there it seems)
Falcomposite who made the Furio, a beautiful composite clone of the Falco.
and recently a french company called Elixir aircraft who created a “one shot” wing meaning that a single manufacturing operation outputs the finished wing.

Back to the Raptor: the claim of 7 GPH cruise fuel burn is the telltale of the designer disregarding the state of the art.

All too often innovators in aviation seem to ignore the fact that subsonic flight is indeed a closed science. “Closed” means that the science is fully developed and that theoretical modeling and experimental results are in agreement. One can literally use cookbook engineering to design a subsonic propeller driven aircraft with predictable results since the 1960s and this is getting easier and more accurate.

When creating a plane to a certain set of specs, a designer should use existing aircraft as data points to estimate the achievable level of performance.
In this case, a Cirrus SR22 T, Piper Malibu/Mirage, Extra 400 or the Velocity XL would give valid reference points. The Velocity uses a similar architecture but with less frontal area, so it should be faster than the Raptor.

Since the Raptor does not use any particular magic, there is no reason for it not to fall into the group.

It is easy to overestimate the expected aerodynamic cleanliness of a “real” aircraft versus a model in a fluid dynamics simulation package. Since this is an input parameter for the program this would be a root cause for such a fantastic fuel economy claim. See the remarkable Pipistrel Panthera for a similar “miss” between design claim and real world data.

As fascinating as the technical project is, I believe that the Raptor in its present specs will never make it beyond prototype stage, due to its unmanageable degree of innovation. I believe that it can at best become a better (unpressurized) Velocity, powered by an off the shelf engine. And that it will be more expensive than a similar Velocity XL.

And yet, I follow every video… What an amazing project…

Last Edited by Flyingfish at 24 Nov 11:43
LSGG, LFEY, Switzerland

Is there a way to simulate 25000ft altitude for the engine? For example put the whole engine in an airtight chamber and only let the exhaust stick out through a sealed hole. Then start the engine – it will suck air out of the chamber, pressure sinks. Once the 25000ft pressure is reached, open a small valve to let air into the chamber, enough to keep the pressure constant to the 25000ft pressure.

Switzerland

I suspect the problem is the vast amount of air the engine needs in operation. Also you need to properly simulate things like the reduced exhaust back pressure at altitude, and any RAM air effect on the air inlet. Also, certification includes high altitude restarts so you would have to pump the air out… and what about restarts from the windmilling condition, and with the engine hot, and cold… There could be all sorts of things which work differently e.g. the electronics might not work when cooled to -50C or whatever the cert requirement is (actually it must be damn hard to test the lowest ECU ambient spec on the engine anyway).

Administrator
Shoreham EGKA, United Kingdom
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