Larry, the RV guys have been through this a few times. One of
the tool suppliers sold a “flush” static port kit. It looked real
nice, but lead to errors like your friend’s. You didn’t mention if
your altimeters were also disagreeing.
It seems the pressure in the boundary layer is not the same as
free stream pressure. But, if the port sticks out a little, it works.
One popular fix is to just take the head of a pop rivet (with
the hole in the center) and glue it over the flush port. Another is to replace
the port with one that sits 1/8” or so proud of the surface. STEC sells
one like that, and also a little spoiler that goes upstream of the port.
This is all airframe specific of course, so YMMV. I know that no
self respecting Lancair guy would just use an entire pop-rivet like Van’s
suggests in their plans (neither would I).
John Huft
RV spy
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Larry Henney
Sent: Sunday, June 22, 2008 8:38 AM
To: lml@lancaironline.net
Subject: [LML] IAS Error/ Trouble shooting tips?
I
flew formation with a 320 today that had an IAS 20 kts above mine in welded
wing. The weird part was that the a/c had an IFR pitot/static transponder
cert less than a month ago. Additionally, the internal static port was
found to be loose and the shop reattached it and certified the
installation. Meanwhile the airspeed indicator was sent out for check out
and was yellow tagged with no problem found.
What
is wrong with my buddies airspeed system? Inquiring minds need to know.
TIA
for helping us mitigate trouble shooting.
IAS
within a couple kts of a dozen other planes.