“Can someone give the criteria and procedure that is used to derive a Vne speed ?”

 

There are lots of issues affecting Vne as noted in previous posts.

 

But as I recall there is one test requirement for FAR 23 certified aircraft:  Whatever the manufacturer sets for Vne ( which setting could arise from many factors), the aircraft must be flight tested to 1.1 times Vne (sometimes called Vd for dive speed) successfully before it can be certificated. 

 

So an aircraft may be able to fly, say, 1.2 times Vne before something terrible happens, but only the territory up to 1.1 times Vne is explored in the certification test.   

 

Thus flying beyond this speed would suggest serious test flying as you are well and truly in unexplored territory, and best have helmet and parachute on. 

 

Whether or not a stick or rudder rap is required at 1.1 times Vne, I do not know.  Perhaps someone closer to the current version of FAR 23 can confirm or deny this requirement.  In any event, a stick rap at 1.1 times Vne would be require lots of preparation and some enlarged cojones.  Not recommended.

 

When Brent Regan and I were racing his Lancair IV Denver to Oshkosh (1996, 97 as I recall), the descent profile was Mach limited initially starting at 27,000 feet using a hard limit of Mach 0.58.  This was chosen because the factory aircraft was test flown to Mach 0.6 and we did not want to enter the unknown.  This Mach number (I had to compute it in those early days – no Mach displays then) was held until the IAS built to Vne (274 knots IAS) and this IAS was held to the bottom of descent, all occurring at 90-100% power. The  maximum cruise speed at 27,000 was about 320 knots TAS (corrected for temperature and compressibility effects) and Mach 0.52. As I recall, it only required 200-300 feet per minute initial descent at the high power setting to drive the Mach number up to 0.58, so the descent started out very flat, and the built up as the air got thicker.  I think we hit Vne at about 12-14,000 feet and the maximum descent rate near the bottom of descent was off scale on the VSI.  It sounded quite different from cruise and caused the hair on the back of the neck to stand up a bit particularly since much of the descent was in IMC. 

 

Key point for you IVP guys: It does not take much nose down high altitudes and high power settings to push you up to Mmo, the maximum allowable Mach number.

 

Y’all be careful out there.

 

Fred