Hello AviationExperts,
Recently Joby #eVTOL went down after trying to do extreme stress tests. Tracking websites have shown Joby Flying at 270 Miles per hour where as top speed of Joby S4 is 200 MPH
Can some expert decode why Joby is flying at 270 MPH ? At what stage of FAA certification warrants flutter test / Setting Vne ?
On a scale of 1 - 100 Part 23 certification where exactly they need to go for 1.3x top speed ?
Highly Appreciate Any Inputs
Thank you 🙏
What exactly applies depends on the date on which Joby applied for a type certificate. Before August 30, 2017, FAR23 consisted of a large body of specific regulations which had grown like weed over the preceding decades. Among those, FAR part 23.629 covered flutter, and paragraph (c) demanded that
Any rational analysis used to predict freedom from flutter, control reversal and divergence must cover all speeds up to 1.2 VD/1.2 MD, limited to Mach 1.0 for subsonic airplanes.
It seems Joby applied before that date so they need to prove compliance with 23.629(c). However, they should have stopped at 240 MPH, unless their dive speed is higher than 200 MPH. Top speed is not an exact wording - this could as well be the top cruise speed, and dive speed must be higher than that again. FAR part 23.335 requires dive speed to be 1.25 times cruise speed. This would bring you to the 270 MPH which caused their prototype to fail.
