Dom old chap (et al),

 

Y'know, I also have problems with the TAS argument and I read the report (Flying High and Fast) written for a Van's publication by Ken Krueger (no relation).  No other publication I have ever read discussed Vne related to TAS.  In any event, the emphasis of this report is the overpowering RVs with big turbo-charged engines and thereby exceeding a variety of design limited specifications.  Vne being one of them.  One way to look at Vne is that it pertains to theoretical design limits beyond which the concept "unknown consequences" enters the picture.  Flutter is not the only issue as structural limits may also be exceeded.  Remember that aluminum can become distorted (a hint) before it breaks whilst glass fails explosively when stressed beyond its limits. 

 

That idea should bring the following into focus.  The 320/360 Vne was set by the designer.  From a structural view, the wings were tested to 9 Gs for a Max Wt of 1685 pounds with the stated load limit of 4.5 Gs - a 100% safety factor.  Some have set the MTOW somewhat higher thus reducing the safety factor.  Then we have those that added outer fuel bays or extended wing tips along with the big/small tail difference.  Flutter can be induced by airframe and flying surface interactions that create a destructive resonance, a resonance peculiar to the construction characteristics of the whole system.  Thus, the same differences that may alter original structural limitations may also affect resonance relationships - i.e. The stiffening of the tail cone may affect the stabilizer response to prop pulses and maybe even the natural harmonics in the airframe.

 

Vne in our Lancairs (200/300 series) may be a conservative value and exceeding it (IAS) makes one a serious test pilot.

 

For myself, exceeding 225 KIAS (235 KIAS Vne) requires conscious work as rudder trim is exceeded requiring the left foot to exert some pressure to keep the ball centered and the nose down trim is also exceeded requiring a good push on the stick.  Thus, power is often reduced in a dive (Hmmmm, power used as a trim device).

 

I looked at NTSB reports for fatal Lancair accidents from 2001 to now (97 total) and could only find 3 where, uh, things came apart, 2 IVs were broken up in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a IVP where one aileron couldn't be found among the debris (N299SD 5-15-04).  I forgot which one of these raised questions about re-balancing control surfaces after a paint job.............

 

Scott Krueger

 

PS  During my review of the 97, it seemed that the most common cause of a fatal crash was loss of control because of going too slow while too low.

 

G’day Bill,

So Van, of Van’s is saying that when I was flogging along in my B727 and Airbus at 470 KTAS each of which had a VMO of 350 KIAS I was exceeding Vne?

Don’t think so.

Cheers

Dom

VH-CZJ

 

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Bill Kennedy
Sent: Tuesday, 1 December 2009 10:29 PM
To: lml
Subject: [LML] Re: Vne is NOT a meaningless number

 

Van of Van's Aircraft wrote about VNE a couple of years ago. Much to my surprise, VNE is true airspeed, not indicated. It's pretty easy to exceed in my Lancair. Results can be explosive, meaning onset of flutter to component failure can be nearly instantaneous. I can't wear a parachute in my plane (Lancair 320), so I wouldn't screw around with it.