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Date: Wed, 09 Dec 2009 12:04:43 -0500
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From: "Dr. Weinsweig" <WeinsweigD@tsnci.com>
Subject: [LML] Re: Vne discussion
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yes,  this whole thing about mach limitting speed is rather new to me =
also.  i don't really remember being taught about it in initial or =
recurrent training(though i do subscribe to grayhawk's theory of new info =
requires old info to leave the brain-lol!).  what i am understanding from =
this discussion is that vne for lancairs is indicated  airspeed ie 274 =
kias for a iv.  but the mach speed  for a iv that should not be exceeded =
due to flutter considerations is 0.57mach ie .57 x 761=3D433 mph Tas or =
382 kTas.  is this correct?  still not quite sure why this mach speed is =
in tas and not ias.  but if this is true it has definite ramifications for =
a iv or propet particularly during descent.  despite the few flames, this =
has been an interesting and practical discussion.

david weinsweig
n750dw propjet
178 hours


>>> bknotts@buckeye-express.com 12/09/2009 8:12 AM >>>
I haven't seen much on Mmo.  In fact, this is the first time I've heard=20
of a limiting mach number for the IV-P.  My Chilton PFD shows any mach=20
above .35 at the top of the airspeed tape.  I've seen .44 in cruise at=20
altitude.  (I giggled like a little girl.)  Now I'm a little concerned=20
that the "hard" Mmo should be placarded so as not to exceed it in a=20
cruise power (usual) descent.

Barry Knotts
N4XE, LIV-P, Conti TSIO-550

Frederick Moreno wrote:
>
> =20
> When Brent Regan and I were racing his Lancair IV Denver to Oshkosh=20
> (1996, 97 as I recall), the descent profile was Mach limited initially=20=

> starting at 27,000 feet using a hard limit of Mach 0.58.  This was=20
> chosen because the factory aircraft was test flown to Mach 0.6 and we=20
> did not want to enter the unknown.  This Mach number (I had to compute=20=

> it in those early days -- no Mach displays then) was held until the=20
> IAS built to Vne (274 knots IAS) and this IAS was held to the bottom=20
> of descent, all occurring at 90-100% power. The  maximum cruise speed=20
> at 27,000 was about 320 knots TAS (corrected for temperature and=20
> compressibility effects) and Mach 0.52. As I recall, it only required=20
> 200-300 feet per minute initial descent at the high power setting to=20
> drive the Mach number up to 0.58, so the descent started out very=20
> flat, and the built up as the air got thicker.  I think we hit Vne at=20
> about 12-14,000 feet and the maximum descent rate near the bottom of=20
> descent was off scale on the VSI.  It sounded quite different from=20
> cruise and caused the hair on the back of the neck to stand up a bit=20
> particularly since much of the descent was in IMC.=20
>
> =20
>
> Key point for you IVP guys: It does not take much nose down high=20
> altitudes and high power settings to push you up to Mmo, the maximum=20
> allowable Mach number.
>
> =20
>
> Y'all be careful out there.
>
> =20
>
> Fred
>
> =20
>