Stockmanreef
Well Known Member
How many people are using the stock static ports versus Cleaveland, SteinAir. to some other Source?
Van?s sells an optional static port that is held in place with a bolt inside the fuselage and replicates the shape of the standard SD-42-BSLF pop rivet. Do these count as ?stock? or ?other??
https://shop.vansaircraft.com/cgi-b...8-444&browse=airframe&product=static-kit-port
Just curious.
Decades ago the "best" location was determined experimentally.
Anyone know how?
Has the location later been verified by fluid dynamic modelling?
Finn
I used the Vans port outside and SafeAir1 port inside. It allows the use of the reliable Vans port on the outside and the SafeAir1 fittings inside.
Not flying yet.
The location choice was based on a lot of prior experience and the verification was by flight testing to show that airspeed indications (the one most effected by static pressure error) are correct.
Side note - In my opinion a poll such as this without also asking whether the ports being used have been verified with detailed flight testing, is not of much value. It could just show indications of the blind leading the blind.
A lot of different ideas are used by experimental aircraft builders. Many of them are adopted by others. Sometimes in large #'s. And often times when the originator of the idea hasn't even made their first flight yet.
I am not saying that any in the poll list are bad. They are probably all fine because the tribal knowledge in the RV community has spread wide enough now that it is pretty well known that there are some specific details regarding static ports that need attention.
Bottom line..... following a popular trend based on numbers alone is rarely a good decision when it comes to experimental aircraft.
My complaint about the original port provided by VANs is that it does not provide a positive and long lasting seal. As airplane ages, the tube that is simply inserted into the pop rivet loses its seal and will leak.
Of course much more important if you fly IFR and get your altimeter certified or not.
Just to be clear.
The SafeAir Static port(s) is riveted and prosealed to the inside of the fuse where Vans plans recommend each side. It may be a hair off to allow the flannge to clear the bulkhead.
The side skin and SafeAir port are drilled to the size requied for the Vans port (rivet).
The Vans port (rivet) is installed with proseal from the outside. No possibility of a leak and the port is, for all practical purposes, flush to the skin as Vans intended.
On the inside, the SafeAir port is plumbed with SafeAir fittings and tubing.
I elected to put the "T" at the top of the bulkhead.
As I mentioned, mine has not flown yet.
Just to be clear.
The SafeAir Static port(s) is riveted and prosealed to the inside of the fuse where Vans plans recommend each side. It may be a hair off to allow the flannge to clear the bulkhead.
The side skin and SafeAir port are drilled to the size requied for the Vans port (rivet).
The Vans port (rivet) is installed with proseal from the outside. No possibility of a leak and the port is, for all practical purposes, flush to the skin as Vans intended.
On the inside, the SafeAir port is plumbed with SafeAir fittings and tubing.
I elected to put the "T" at the top of the bulkhead.
As I mentioned, mine has not flown yet.
Regarding accuracy of various static ports, this is a more complicated issue than some may realize. The CAFE Foundation tested the RV-9A factory ship and published the table below They measured pitot and static pressure using a special probe mounted to a cuff on the wing, in order to minimize errors caused by airflow around the aircraft. The resultant CAS measurements may still not be perfect but are presumably better than any measurement made on the aircraft skin. They also used a calibrated barograph to measure errors in the airspeed indicator.
The result shows that there are errors of up to +7 mph caused by the factory pitot-static system. The error gets smaller at lower airspeeds, which is probably what you want (more accurate near stall). Interestingly, the instrument error does the opposite; it is up to +8 mph error on the slow end and very accurate at the high end. From the pictures in the report it was an analog "steam gauge" indicator, but digital isn't necessarily more accurate. The total error for this particular system runs up to 12+ mph (at speeds near Va).
One conclusion from this might be that the stock pitot-static system really is not all that accurate. Or, one might conclude that it's accurate enough, provided you have an idea of the indicated airspeed at Vso. These data also make it clear that getting accurate data takes a lot of work. As anyone who has been involved in racing will tell you, its difficult to get reproducible numbers at precision better than ~3 kts.
I asked the mother ship where to get the rivets after telling them that my plan to possibly install the standard rivet head into the safair air.
The response was in a driven out SD-42-BSLF followed by the following links:
http://porcupinetech.com/rvproj/pitotstatic.htm
https://buildaplane.wordpress.com/tag/static-system/
http://smilinpete.com/wp/?cat=65
https://buildaplane.wordpress.com/2010/05/14/pitot-static-system/
http://rvplane.com/?dayid=506
http://www.vansairforce.com/community/showthread.php?t=8836
No other comments at all in the email.
cheers
One thing I found a long time ago on the RV-10 model was that I purchased flush flat mounted ports by Cleaveland and they were not accurate. I can't remember the error but I think it was around 7kts in cruise. They later came out with domed ports, which were much more accurate.