Pitot Leaks
 

Hello Gents

This week end I flew my RV-4 in formation with a friend of mine ( Also an RV-4 ) and we started checking our IAS/TAS/GS as we were moving along and to my surprise his IAS/TAS were 12 knots higher than mine on the same GS.

Mine were IAS/TAS ; 140/148 knots at 4500' and 2450RPM and his were exactly 12 knots higher at the same altitude and RPM.152/160 .:eek:

I think mine are a little low for an RV-4 with an 0-320 with around 175HP. so after talking with a friend who an engineer on the C Series ( Scott here on VAF ) he told me that I may have a leak in my pitot lines..

I have a Dynon Skyview with the Dynon pitot installed and used these to do the connection to the Adhars..

http://www.steinair.com/storedetail.cfm?productid=532

Are these good enough to provide a good seal or should I use something and if yes...What should I used??

Also what did you guys used to make the connection at the pitot level ( Connecting the pitot line and the AOA line)???

Thanks

Bruno
rv4@videotron.ca

I fixed the leaks in my system by putting some DC4 lubricant on the outside of the plastic line and then reinserting the tube into the connector. Technique curtesy of Walt.

Stein's fittings work great.

I would recommend to use a Pitot-Static test set and inspect your system if you have a leak or indication failure.
You can easily troubleshoot that system with isolating parts of the tubing.
The fittings from Stein are great. I always use teflon tape on the threads of fittings.

kai

wrigley's spearmint gum! :D

It is always good to do leak checks on both pitot and static. The static system is much more sensitive to leaks than the pitot however. You might notice that for certified aircraft, the regs list a static system leak rate, but leave the pitot leak rate up to the aircraft manufacturer.

It takes a pretty significant pitot leak to cause an error in airspeed. It is always possible that a pitot tube is set up to close to the wing which could cause an error, but more likely it is a static system error. If you both set your altimeters to the same altitude on the ground, then did a similar side by side test, would the altimeters read the same? If so, then it is a pitot problem. If not it is a static system problem. The static port can be a source of large errors if not set up properly.

It also might be your friends airplane and not yours.

Static errors are the most common cause of IAS errors in my experience.

Do you have the standard pop-rivet head in the location described in the manual?

MY RV-4 had been modified with a flush static vent and didn't read correctly until I glued a pop rivet head over the flush vent. Some have experimented with dams etc to adjust the static pressure to the true, free-stream value.
The same goes for checking for static leaks as cabin static could easily give a 5-10 knot error.

He said the alt was the same as the other airplane he was formating on so likely the static is fine.

Missed that. Yes if the altimeters were matched, then either pitot location or a leak.

I wouldn't rely too much on that. A 5% error in IAS due to static error at 120 knots is equivalent to a 50 ft altimeter error. That could easily be lost in the other errors when comparing altimeter readings.

E.g.At 120 KIAS at sea level the static pressure is 1.00 atmospheres and the Pitot pressure is about 1.02 atm.. It doesn't take much of a static error to cause a significant airspeed error!