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  1. Scheny

    Boeing - Design Issues...

    I heard that the newest 737max problem is deactivating the flight director if the stick shaker activates. To avoid an undefined state, the flight director and autopilot would have to turn themselves off on their own. So, no toggle switch anymore.
  2. Scheny

    Canard (deep) stalling.

    I don't know this statistics, but there is a very good article about the comparison. To sum it up, the Cirrus has rather low control feedback due to the fact that you have to steer it out of your wrist rather than the whole hand and that this is combined with an abrupt and rather high stall...
  3. Scheny

    Canard (deep) stalling.

    As everyone seems to be telling about stall experience: here is what I can add from the Diamond family (DA20, DA40, DA42/62). For the DA20/DA40: When you put power to idle and gentle pull on the stick, it is almost impossible to stall. At first, the stall warning will kick in and it takes...
  4. Scheny

    Canard (deep) stalling.

    As for the prop, you are right with the angle of attack. It is of small variation, so I don't expect too much loss. What it definitely does, is create a lot of noise, as the variations in pressure are creating sound waves. Airbrakes are effective at speeds above 70kt, so with a landing speed of...
  5. Scheny

    Raptor Composite Aircraft

    His engine system is an automotive diesel. It has a high pressure pump at the engine and low pressure pumps in or at the tanks. In the car, the safety is by having low pressure pumps off in case of an accident. However, this is for cars, where safety considerations include that you can stop...
  6. Scheny

    Canard (deep) stalling.

    Keep in mind that for ANY aircraft, the Cl (factor of lift) for asymmetric airfoils is much higher in normal flight, than for inverted. A canard which let's say stalls at 70kt, wouldn't surprise me to stall inverted already at 100kt. If you are pulling G's, the effect is even worse. Thanks to...
  7. Scheny

    Canard (deep) stalling.

    The term "deep-stall" regards a stall in a stable condition and there are two different scenarios commonly called that way. There is the deep stall that you can experience in T-tails, where the elevator gets blanked by the stalling main wing. This renders the elevator useless and the plane can...
  8. Scheny

    Experimental Ducted Fan Aircraft Designs

    100% right, nothing that I could add :)
  9. Scheny

    Experimental Ducted Fan Aircraft Designs

    We didn't want to proceed with anything bigger than the DGEN, as there is already the Viperjet and honestly, this one I don't think we could beat no matter how much help I would get. As for your numbers: with rotate at 65kt, actual liftoff would be rather at 85kt. Distance is then at best 280m...
  10. Scheny

    Raptor Composite Aircraft

    You misunderstood two factors: It is not overweight. At the moment it is a one-seat aircraft instead of a five-seater, but still within design MTOW :p The particular GRS model he is using needs 150m vertical altitude, but it was shown a lot of times, that with sufficient forward speed a lot...
  11. Scheny

    Experimental Ducted Fan Aircraft Designs

    You are right, used jets don't cost that much and owning it is the expensive part. Our Eurofighters in Austria for instance, have 70k running costs per hour o_O (not including buying them!), while a Cessna Mustang is more in the 7k range, already including the leasing if flown enough hours. The...
  12. Scheny

    Raptor Composite Aircraft

    Why does everyone beat around the bush? Normal drives have the axis of the engine and the axis of the prop fixed in parallel to each other and the systems mounted on dampeners as a whole. The Raptor has prop axis fixed in relation to the aircraft (mounted fixed on motor mount), while the...
  13. Scheny

    Experimental Ducted Fan Aircraft Designs

    As for the UL39, our concept was quite similar, but we wanted it to look a bit more like the F-35 ;) . Both for me and my aerodynamics guy it doesn't make much sense to copy something and use it in a completely different aerodynamic regime. Just think, speed, Reynolds, weight, etc. all being...
  14. Scheny

    Experimental Ducted Fan Aircraft Designs

    Also, something for the UL I had two very long phone calls with their sales rep as it was our first choice for the two seat version. Without an ongoing series production, the price per unit has tripled and lies above (larger model) competition. In addition, there are some engineering hours...
  15. Scheny

    Experimental Ducted Fan Aircraft Designs

    Before we started the "Beast One" project (which uses the PBS TJ100), we wanted to start with a two-seater. Although the name suggests the TJ1500 has 50% more thrust, the TJ100 already provides 1200N, so the increase is only 25%. For transport jet aircraft, the minimum thrust is calculated in a...
  16. Scheny

    Raptor Composite Aircraft

    I just checked the repair manual for the SR22. It is using 7781-F16 fibers from Hexcell with ~9oz weight. Except for edges (where up to 10 layers without a core are used), the base layup are 2 layers (~18oz) per side on a 0.375 (or less) foam core. As it is glass fibre, you would even need less...
  17. Scheny

    Building more crash-worthy composite planes and cockpits

    About mass relief: before I knew what I do now, I once asked why a car with a 500lbs diesel engine needs the same crash structure as one for a 250lbs gas engine. Of course, the engine hits the target first and does not add this energy upon the crash structure. So, having a plane with the engine...
  18. Scheny

    The "Beast One": What doesn't kill you makes you stronger

    Because the sweep is used to substitute the elevator, by shifting lift between inner and outer portion, therefore between rear and front. As you have the trade-off between losses due to sweep and benefit of having no tail, there is a sweet spot in the middle with the optimum design point -->...
  19. Scheny

    The "Beast One": What doesn't kill you makes you stronger

    The formula for change in CLmax with sweep angle (correction factor) is: K=cos(Lambda C/4) according to Raymer K=cos³(Lambda leading edge) according to Young Losses are therefore approximately (using Raymer): ~0% @10°, 5% @20°, 15% @30°, 25% @40°, 35% @50°, 50% @60°
  20. Scheny

    The "Beast One": What doesn't kill you makes you stronger

    For academic reasons, I also took this Prandtl paper and calculated a wing based upon it. It has good behavior like slightly improved induced drag and proverse yaw, but it is not very useful in my case. With the approximately one quarter longer and super thin wingtips, this is nice for a...
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