Flight Design C4 & Tecnam P2010 & non TSO avionics in certified aircraft

Aviathor wrote:

Actually Mr Yeager does say it will sell for just under 400 k$ fully loaded.

That was the Tecnam, not the C4

USFlyer wrote:

Carbon fiber in aircraft construction is the future, not the past. The aerodynamic shape and weight savings cannot be matched by the old materials from the past.

USFlyer wrote:

The strutless planes shown are canvas covered. The Cessna’s with struts are metal/rivet not canvas or wood. The use of struts is clumsy, draggy, old school and wreck the siteview.

Not sure how to extract a coherent message from that but responding factually, neither the Cessna Airmaster or Lockheed Vega had fabric covered wings. Both had monocoque, stressed skin wing structures in which the skin was a low density, buckling resistant composite called wood. Low density material can be thicker for the same weight, making it efficient in resisting buckling due to shear loading, a primary function of a light aircraft wing skins in stressed skin construction.

I believe the first strutless monoplane was built in 1915. I was quite involved in building an aircraft with carbon fiber wing spars just under 35 years ago, and have since designed large structures incorporating composite material five times as strong as alloy steel. Neither technology has become universal for aircraft and never will. Selecting a structural concept and making material selections for a given design is not a process or technology that’s well covered by blanket statements. Cessna and Tecnam both think strut braced wings are better for planes in their speed range, and they are not stupid or careless. A very light steel wire braced Pitts biplane climbs at 2600 fpm on essentially the same 180 HP Lycoming engine as the Tecnam, good weight savings and aerodynamic design if climbing is what you want to do.

Neil wrote:

I’m just saying that it’s good for GA that companies are choosing to invest in bringing out new aircraft.

Neil – I totally agree with the above statement.

What a vehemently DIS-agree with is the proliferation of BS, whether it is propagated by the Marketing Dept or some would-be customer of said product …

USFlyer wrote:

Carbon fiber in aircraft construction is the future, not the past. The aerodynamic shape and weight savings cannot be matched by the old materials from the past.

Finally something that has some truth …

Silvaire wrote:

Low density material can be thicker for the same weight, making it efficient in resisting buckling due to shear loading, a primary function of a light aircraft wing skins in stressed skin construction.

I think the “problem” with light aircraft is you cannot really get thin enough aluminium, because it will become too flimsy. But then again, by using thicker skin, the design can be made very much simpler, but “boxier/tubular” without much weight penalty. What composites lack is rigidity. Carbon fibre is very strong, but also very flexible without much internal damping, which is not always an advantage. The WT9 Dynamic is built using thin sandwich design (karbon/kevlar – foam – karbon/kevlar) in parts of the structure. Very strong, rigid and extremely light (feels like balsa sheets), but judging by the price of the WT9, also very expensive. Composites can be lots of different things, and just because it is “carbon” doesn’t necessarily mean it is any better than wood or aluminium. The thing with carbon is it lends itself easily to “low cost” (low man hour) mass production, but to really get a good material (light, strong and rigid), a sandwich design is necessary, and then it is not that low cost anymore. I see from the C4 website it uses a mix of different methods.

From what I understand most composite materials are not really lighter than aluminum. Carbon fiber is but the composite used in most light aircraft today is not carbon fiber. Is my understanding correct? Could someone provide an overview of the different types of materials that can be used in light aircraft and their advantages/drawbacks?

I looked at the specs of the C4 on Wikipedia. It is supposed to have an empty weight of 600 kg, 1200 kg MTOW and a fuel capacity of 70 USG (190 kg). If that turns out to be true, it will be able to carry 4 adults, full tanks and then some, which is really impressive and could make it very attractive in its class.

In comparison “my” DA40-180’s empty weight is 802 kg (with DME, TAS600, WX500) for the same MTOW as the C4, and the fuel capacity is 50 USG (136 kg). In other words barely 400 kg useful weight compared to 600 kg for the C4.

On Wikipedia the max cruise speed for the C4 is given as 160 kts whereas that for the DA40 is 150 kts. In reality the max cruise speed I have seen on the DA40 is about 138 kts (at 65% BHP) and I believe that was at 8000 or 9000 feet with a lightly loaded aircraft.

Edit: I see LeSving partly answered my question while I was writing this :-)

At this point absolutely NOTHING is official concerning the C4 specs.

Until it is certified and a POH is issued, it’s ALL pure speculation … and most of that, does not pass a reality check.

Michael wrote:

Until it is certified and a POH is issued, it’s ALL pure speculation … and most of that, does not pass a reality check.

It looks cool, 6 cylinder smoothness, 2x G3x touch + GTN750, designed and produced in Germany/Ukraine and the price is 220k euro. It’s hard to see how this can go wrong, even if it should lack a knot here and a kg there.

Thing is, reality showed that from a pre-certification phase to the manufacturing phase, cruise speeds, empty weights and puchase prices have often changed not by a few percent, but by much much more.

Realistically, my guess is the C4 will weigh about 700 kgs (which would still be a very good value, right there in the Robin ballpark), will cruise 145 knots in max cruise regime and will cost about 350.000€ plus VAT, just like the P2010.

That’s simply the way it goes in GA.