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Date: Wed, 09 Dec 2009 15:31:27 -0500
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From: Matt losangeles <mattinlosangeles@yahoo.com>
Subject: Re: [LML] Re: Vne discussion
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A few years ago I owned a Mooney with a Rayjay turbo that was installed via=
 an STC. On the panel, there was a placard that was added saying "reduce VN=
E 5 knots for each 1000 feet over 23400 feet."=A0 I think the Mooney was or=
iginally certified to 18000 feet and this STC increased it to 24000 feet. B=
ased on that I have always figured VNE was not based on TAS or IAS but some=
 kind of calculation of both and likely other factors. I am planning on add=
ing a Turbo normalizer to my Legacy so getting to the bottom of this is imp=
ortant to me or I am going to have to slow down in decent from high altitut=
e at all times. I sure would like to be able to keep the power in on decent=
 if possible. If I can't find any conclusive information I am going to have=
 to assume the worst of TAS not exceeding 274 knots.=0A=0AMatt=0A=0A=0A=0A-=
---- Original Message ----=0AFrom: Dr. Weinsweig <WeinsweigD@tsnci.com>=0AT=
o: lml@lancaironline.net=0ASent: Wed, December 9, 2009 9:04:43 AM=0ASubject=
: [LML] Re: Vne discussion=0A=0A=0Ayes,=A0 this whole thing about mach limi=
tting speed is rather new to me also.=A0 i don't really remember being taug=
ht about it in initial or recurrent training(though i do subscribe to grayh=
awk's theory of new info requires old info to leave the brain-lol!).=A0 wha=
t i am understanding from this discussion is that vne for lancairs is indic=
ated=A0 airspeed ie 274 kias for a iv.=A0 but the mach speed=A0 for a iv th=
at should not be exceeded due to flutter considerations is 0.57mach ie .57 =
x 761=3D433 mph Tas or 382 kTas.=A0 is this correct?=A0 still not quite sur=
e why this mach speed is in tas and not ias.=A0 but if this is true it has =
definite ramifications for a iv or propet particularly during descent.=A0 d=
espite the few flames, this has been an interesting and practical discussio=
n.=0A=0Adavid weinsweig=0An750dw propjet=0A178 hours=0A=0A=0A>>> bknotts@bu=
ckeye-express.com 12/09/2009 8:12 AM >>>=0AI haven't seen much on Mmo.=A0 I=
n fact, this is the first time I've heard =0Aof a limiting mach number for =
the IV-P.=A0 My Chilton PFD shows any mach =0Aabove .35 at the top of the a=
irspeed tape.=A0 I've seen .44 in cruise at =0Aaltitude.=A0 (I giggled like=
 a little girl.)=A0 Now I'm a little concerned =0Athat the "hard" Mmo shoul=
d be placarded so as not to exceed it in a =0Acruise power (usual) descent.=
=0A=0ABarry Knotts=0AN4XE, LIV-P, Conti TSIO-550=0A=0AFrederick Moreno wrot=
e:=0A>=0A>=A0 =0A> When Brent Regan and I were racing his Lancair IV Denver=
 to Oshkosh =0A> (1996, 97 as I recall), the descent profile was Mach limit=
ed initially =0A> starting at 27,000 feet using a hard limit of Mach 0.58.=
=A0 This was =0A> chosen because the factory aircraft was test flown to Mac=
h 0.6 and we =0A> did not want to enter the unknown.=A0 This Mach number (I=
 had to compute =0A> it in those early days -- no Mach displays then) was h=
eld until the =0A> IAS built to Vne (274 knots IAS) and this IAS was held t=
o the bottom =0A> of descent, all occurring at 90-100% power. The=A0 maximu=
m cruise speed =0A> at 27,000 was about 320 knots TAS (corrected for temper=
ature and =0A> compressibility effects) and Mach 0.52. As I recall, it only=
 required =0A> 200-300 feet per minute initial descent at the high power se=
tting to =0A> drive the Mach number up to 0.58, so the descent started out =
very =0A> flat, and the built up as the air got thicker.=A0 I think we hit =
Vne at =0A> about 12-14,000 feet and the maximum descent rate near the bott=
om of =0A> descent was off scale on the VSI.=A0 It sounded quite different =
from =0A> cruise and caused the hair on the back of the neck to stand up a =
bit =0A> particularly since much of the descent was in IMC. =0A>=0A>=A0 =0A=
>=0A> Key point for you IVP guys: It does not take much nose down high =0A>=
 altitudes and high power settings to push you up to Mmo, the maximum =0A> =
allowable Mach number.=0A>=0A>=A0 =0A>=0A> Y'all be careful out there.=0A>=
=0A>=A0 =0A>=0A> Fred=0A>=0A>=A0 =0A>=0A=0A=0A=0A--=0AFor archives and unsu=
b http://mail.lancaironline.net:81/lists/lml/List.html=0A=0A=0A=0A