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Static port location help

E

etekberg

Active Member
Hi,

I purchased an already flying RV-7A from a builder. He installed the static ports in the forward fuselage. They read too fast, so he disconnected them and left them vented open in the cockpit.

The plane is in the shop for repairs and I am thinking about having some new ports installed in the correct location while it is repaired.

Can anyone tell me where the correct location is? Or better yet, does anyone have a copy of the instructions they can e-mail me? I have to communicate the correct location to the shop. Pictures would help a ton.



Thanks in advance!
 
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Static Port is a Rivet!

Hi Eric,

I have a bag of these left over from my baffles and would be happy to send you a few if you need them
 
Static Port is a Rivet!

Hi Eric,

I have a bag of these left over from my baffles and would be happy to send you a few if you need them.
 
Thanks

Thank you to everybody. Roberta sent the instructions which I forwarded to the shop.

I didn't realize it was just a plain rivet. I'm sure the shop has them. Thank you for the offers and all the help!
 
As a data point:
I installed aftermarket flush static ports
at Van's location. My airspeed indicated
low until I bonded the heads of baffle rivets
to the flush ports. Airspeed seems to be much
more accurate now. Not done testing.
Tom
 
etekberg said:
I didn't realize it was just a plain rivet. I'm sure the shop has them.
Click to expand...
The height of the rivet head is important, as that determines how much the air has to accelerate to go over it, and that determines the pressure sensed at the port. So, if you don't have the exact rivet type that Van specifies, you should at least use one with the same height head.
 
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Cheesy?

jlfernan said:
I'm going with some from Spruce. They look like what you see on Cessnas. The pop rivet Vans uses is just too cheesy. The A.C. Spruce ones are tapped for fitting and that alone, to me, is worth the cost of admission. I don't like how the Vans ones are installed, ie; zip tie the static tubing to them and then RTV over that. IMHO.

[http://www.aircraftspruce.com/catalog/inpages/staticports.php

http://www.aircraftspruce.com/catalog/hapages/hosetubefit.php
Click to expand...

Van's solution is simple, small and unobtrusive, and works very well. Be carefull of the "flush" solutions as they do not work well. The protrusion of the pop rivet head is very important to "break up" the airstream so the port reads properly.
 
JonJay is spot on.

Roberta

staticpbf3.jpg
 
jlfernan said:
I'm going with some from Spruce. They look like what you see on Cessnas. The pop rivet Vans uses is just too cheesy. The A.C. Spruce ones are tapped for fitting and that alone, to me, is worth the cost of admission. I don't like how the Vans ones are installed, ie; zip tie the static tubing to them and then RTV over that. IMHO.

[http://www.aircraftspruce.com/catalog/inpages/staticports.php

http://www.aircraftspruce.com/catalog/hapages/hosetubefit.php
Click to expand...
I've seen reports of 10 kt airspeed errors and 100 to 200 ft altitude errors caused by flush static ports. The airspeed error is not significant in the big scheme of things, but the altitude error could put you a lot closer to the IFR traffic than expected, even if your altimeter shows you at a VFR altitude. And, if any larger aircraft are responding to a TCAS RA from you, the TCAS will think you are a different altitude than you really are, which could increase the odds of a very close encounter with another aircraft.

While I understand people's desire for a good looking aircraft, static ports are one area where proper function is more important than looks.
 
jlfernan said:
I'm going with some from Spruce. They look like what you see on Cessnas. The pop rivet Vans uses is just too cheesy. The A.C. Spruce ones are tapped for fitting and that alone, to me, is worth the cost of admission. I don't like how the Vans ones are installed, ie; zip tie the static tubing to them and then RTV over that. IMHO.

[http://www.aircraftspruce.com/catalog/inpages/staticports.php

http://www.aircraftspruce.com/catalog/hapages/hosetubefit.php
Click to expand...


The outside of the Spruce static ports are 3/32" thick, not flush, which is slightly thicker than Van's. That should be sufficient to function properly.
 
I agree with Kevin wholeheartedly about flush static ports. However, the ones you are using from ACS are not flush and should be fine. I used a very similar unit from another vendor (about 3/32 thick) and have no static problems at all. And, frankly, they do look a lot better than the pop rivets, IMHO.
 
All of the big iron I've seen has completely flush static ports. They might even be slightly recessed because they are typically bare metal while the surrounding area is painted.

Why are we in such a backwards world here in RV-land?

Paul (flush ports installed)
 
Paul Eastham said:
All of the big iron I've seen has completely flush static ports. They might even be slightly recessed because they are typically bare metal while the surrounding area is painted.

Why are we in such a backwards world here in RV-land?
Click to expand...
The purpose of a static port is to provide a source of pressure that is as close as possible to the free stream ambient pressure. I.e. we want to measure what the pressure would be, if the aircraft wasn't there. But, the air accelerates and decelerates as it goes around the aircraft. Bernoulli's Law tells us that the pressure changes as the air accelerates and decelerates. So, the pressure at most places on the skin is not the same as the free stream ambient pressure.

The big iron folks spend quite a bit of effort to locate areas on the cylindrical (or almost cylindrical) fuselages where the pressure is very close to ambient pressure, and they put flush ports there. But, it seems that the location that Van uses for the static port has pressure that is a bit higher than the free stream ambient pressure. The domed pop rivet provides a correction, in that it forces the air to accelerate as it bends over the top of the rivet, and this causes the pressure there to decrease a bit. This is way you can't just use a flush port here.

Maybe the ACS ones will work OK, and maybe they won't. If you want to use something different than Van's recommended static port, you should plan to spend several flights doing testing to determine whether you have an accurate static source. How to do static system error testing.
 
It's how you mount it.

jlfernan said:
The outside of the Spruce static ports are 3/32" thick, not flush, which is slightly thicker than Van's. That should be sufficient to function properly.
Click to expand...
The problem I have seen with this product is in how people have used it. It is not intended to be mounted flush, but mounted "through" a 1/2" + hole. This leaves a "disk" mounted to the outside of your fuselage. So, others I have seen did not like that and mounted it inside then drilled a smaller hole for the port, basically turning into a flush fitting. Then it does not work as designed.
Personally, I'll take a small round rivet head on my fuselage over a 1"? x 3/32" disk any day, but that is personal preference.
Thousands of RV's flying with the rivet set up and I know it works and looks great from my simple perspective. But, to each his own. That's what this hobby is all about! Have fun.
 
Kevin Horton said:
If you want to use something different than Van's recommended static port, you should plan to spend several flights doing testing to determine whether you have an accurate static source.
Click to expand...
Kevin, I agree with this, and I did it for mine. However, I will submit that this is not unique to using a non-Van's static port. All homebuilts should undergo this proceedure during their first few hours. There are plenty of things other than the static ports that could have an effect.
 
sprucemoose said:
Kevin, I agree with this, and I did it for mine. However, I will submit that this is not unique to using a non-Van's static port. All homebuilts should undergo this proceedure during their first few hours. There are plenty of things other than the static ports that could have an effect.
Click to expand...
Jeff, I agree 100% with your statement. But, with the number of folks who talk about just "flying off the hours", I figured I'd be pissing into the wind to actually get folks to invest 5 hours in static system error flight testing.
 
I am curious how many (if any?) people out there have used a flush port and have NOT found major static error.

The 10kts of error someone referred to above is significant -- around stall speed that's going to be a big deal.

So my debacle is whether to epoxy on a baffle-rivet head or not, in advance of the first flight. Certainly the stall speed will be checked at altitude prior to first landing, but it would be nice to have the ASI reading something close to reality anyway.
 
The flush static ports on my 7A seemed to
have more error at high speeds. The stall
speed is about the same with the bonded
rivets as without. My concern and the tests
I need to do now are in regard to the altimeter
reading and more importantly the blind encoder.
Tom
 
Paul Eastham said:
The 10kts of error someone referred to above is significant -- around stall speed that's going to be a big deal.

So my debacle is whether to epoxy on a baffle-rivet head or not, in advance of the first flight. Certainly the stall speed will be checked at altitude prior to first landing, but it would be nice to have the ASI reading something close to reality anyway.
Click to expand...
The only data I have is at higher speeds, and that is where the 10 kt error was reported, by more than one RV-er. The effect of flush static ports at low speeds will be different.

Even if you have standard static ports, you should't take Van's stall speed numbers to the bank. There are many reasons why any given aircraft may have indicated stall speed numbers that differ from what Van reports:

  • ASI instrument error - I've seen reports of ASIs that were found to have 10 mph errors. Even serviceable ASIs may have 5 mph errors.
  • Pitot or static system leaks
  • Upper gear leg fairings on RV-8s
  • CS Prop fine pitch stop set too fine

Bottom line - Don't stake your life on Van's stall speed numbers. On the first flight, slow down to some number above the stall, and evaluate the controlablity. Add a comfortable increment above this number, and do a simulated approach and flare at altitude, reducing the power just as you would during a landing. If you have adequate controllability to arrest the descent at idle power and achieve a brief moment of level flight, then this approach speed should be OK for the first landing.
 
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