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From: vtailjeff@aol.com
Subject: Re: [LML] Re: the Legacy RG Static ports
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Good advice Charley. My ports are flush. A test per Charley's recommendation=
 will confirm your port location.

Jeff

Sent from my iPad

On Jan 21, 2013, at 9:42 PM, Charles Brown <browncc1@verizon.net> wrote:

> Guys, I am astonished to hear anyone advocating a protruding static port a=
nd especially for the purpose of sticking out of the boundary layer.   I wor=
ked on the critical altimetry for reduced vertical separation minimums at Bo=
eing in the mid-90s and on air data systems at General Dynamics (now Lockhee=
d).  On every airplane and missile design I've ever worked on, the only reas=
on to make a static port anything other than perfectly flush was to insert a=
 correction if the static port was located in a place where the local pressu=
re was different from ambient pressure.  Projecting anything with an edge or=
 corner out of the boundary layer was guaranteed to produce local separation=
 and vortices with unpredictable and probably inconsistent effects on the me=
asured pressure.   On Boeings, we even went to great lengths to measure and m=
inimize skin waviness for 10 feet ahead of the static ports.
>=20
> The static pressure gradient across the boundary layer is generally accept=
ed to be negligible. =20
>=20
> A protruding static port will probably measure pressure that's a little lo=
wer than the local static pressure, which is acceptable only if the port is l=
ocated in an area with higher than ambient pressure.   Perhaps Paul's RV por=
ts were located in such an area.
>=20
> Lancair tech support (whoever it was who answered the phone in 2008) told m=
e to make them flush.  I presume that the port  position that they identifie=
d on the Legacy is where the local Cp is zero, i.e., ambient pressure.  At a=
ny rate, my flush ports seem to work fine.  If you have a Garmin, a good tes=
t is to fly a closed course and see if the deduced wind value is consistent o=
n all headings.  If it is, then a number of things (magnetometer alignment, p=
itot pressure, static pressure, and OAT) are working correctly.=20
>=20
> Charley Brown
> Legacy #299  200 hr
>=20
>=20
> On Jan 21, 2013, at 7:06 PM, Paul Besing wrote:
>=20
> Yes, it has to protrude out about 3/16" on average.  I had this exact prob=
lem with my RV.  I decided I wanted a nice flush look and my airspeed were v=
ery inaccurate until it was discovered that they needed to come out of the b=
oundary layer.=20
>=20
>=20
> --
> Paul Besing
> "Flying releases the mind from the tyranny of petty things"
>=20
>=20
>=20
> On Jan 22, 2013, at 1:25 AM, Dan Ballin <dballin@gmail.com> wrote:
>=20
>> Needs to protrude a little for paint/body work and then there is an
>> argument to have them stick out slight more to get out of the boundary
>> layer.  Others can comment on that, but I would recommend using the
>> Evo static ports.  KCI part number KA0075.  Way nicer and have a
>> standard NPT thread so easier to install and you can install it after
>> paint.
>>=20
>> Dan
>> N386DM LEG2
>>=20
>>=20
>>=20
>> On Mon, Jan 21, 2013 at 11:47 AM, Jeffrey W. Skiba <jskiba@icosa.net> wro=
te:
>>> on page Chapter 24 REV. 0/02-15-02 of the Legacy RG construction manual,=

>>> gives directions for the static ports, however it does not state if they=

>>> should be flush with the skin or slightly protrude ? if they need to sti=
ck
>>> out Is there a max and a min suggested ?
>>>=20
>>>=20
>>>=20
>>> Thanks
>>>=20
>>> Jeff.
>>>=20
>>>=20
>> <Screen Shot 2013-01-21 at 11.57.56 AM.png>--
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>=20
>=20
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