tkatc

tkatc

Well Known Member
During last night's flight my co-pilot and I were fighting over the cabin temp. I wanted the vents open and she wanted them closed. As we played around with opening and closing I noticed the airplane would pitch up or down depending if the vent was open or closed. Anybody else notice this phenomenom or is it just me?
 
Were you on altitude hold? If so, you probably have a leak in the static system.
 
My auto pilot altitude hold is connected to the rear static ports (Vans style). I use a combination pitot static tube for the instruments. A tube runs from the back static ports to the panel for a future "alternate" static source .............if I ever get around to hooking it up.

Anyway, the tube was pulled off the tee, the auto-pilot static source was now sensing cabin pressure............and it was up & down with ventilation & heat............as temps went from the 70's to 14.

L.Adamson --- RV6A
 
Now that you mention it, I was on altitude hold.

If I have a leak, would that cause problems with my AK350 encoder? My mode C has not been functioning correctly.

Ahh, the growing pains of a non-builder. Now how do I locate that leak?
 
My alt hold is vented to cabin pressure and it is sensitive to vents exactly as you discribe. Unrelated to this I also had a leaky staic line due to cold flow of nylon fittings at the threaded input of the instruments. They were 5 yrs old at the time and all of them were "finger" loosely threaded in to the instruments. I know they were tight initially. I replaced all threaded input connections with brass and the static port problem went away.
 
for starters see if the hose has come off the encoder. easy to check and can happen very easy. mine did this year. how is your airspeed reading? mine was off a bit because of this.
 
tkatc said:
Now that you mention it, I was on altitude hold.

Now how do I locate that leak?
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Unfortunately, there is no easy way to find the leak--but, it can and will be found with a little perseverance!

First, you have to have a source for vacuum applied at the static port (tape over the other one). You can use a hypodermic syringe, but the absolute best source IMO is a brake bleeder kit such as the one sold at Sears with the Craftsman label. I believe the criteria used by the FAA is to pump up your altitude to 1,000 feet above current elevation and your altimeter should not lose more than 100 feet in one minute. If you can achieve this, you are good to go.

To locate the leak, begin by unplugging each instrument attached to the static system one at a time and plugging the end of the static tube beginning with the last instrument in the static system schematic. This way you can eliminate each instrument as the source of the problem working backwards from the end of your static system network. After you have checked each instrument, replace its static line. Work backwards or upstream from here back to the static ports, one fitting at a time. Remove the fitting and plug the line until the problem goes away. Eventually you will be all the way back to the T over the two static ports, but you will probably find the offending component way before this.

I recently had a pesky static leak and it turned out to be the RMI µEncoder. There probably aren't that many around any more, but for those of you who built them, the internal tubing will disintegrate with time. I replaced the tubing inside and the problem was solved.

Another good (quick) way to check your static system for integrity inflight is to pull the cabin heat full out with altitude hold engaged and if the aircraft pitches at all, you probably have a static leak. P.S. (Or you can observe the VVI and it should not move at all when pulling the cabin heat out.)
 
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RV7AV8R said:
My alt hold is vented to cabin pressure and it is sensitive to vents exactly as you discribe.
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I have the same setup. When I installed my altitude hold, years after the plane was built, I let it vent to the cabin so every time one of us shuts off a vent there's a slight pitch change. This doesn't necessarily mean you have a leak in your static system since your altitude hold may not be connected, like mine.
When you get your transponder certified the tech should be able to detect a problem, since you didn't specify what the problem is that you're having with it. If ATC keeps telling you you're not maintaining your assigned altitude it's probably your encoder, get it checked! First do what Turbo suggested, check the line on the encoder to make sure it's still hooked up properly.
 
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My mode C is not being detected by ATC. I know when it is working because the Garmin 327 will display pressure altitude in feet. Lately, it has not been displaying any altitude. It was happening intermittently but the last flight it didn't display at all. I suspect a bad encoder...:confused:
 
tkatc said:
My mode C is not being detected by ATC. I know when it is working because the Garmin 327 will display pressure altitude in feet. Lately, it has not been displaying any altitude. It was happening intermittently but the last flight it didn't display at all. I suspect a bad encoder...:confused:
Click to expand...

Check the simple stuff first. Is it plugged in? power available? I would bet a loose cable connector.
If it were bad electronics, I doubt you will see intermittent operation.
 
KTTN

Tony,

When you get your encoder fixed come up to KTTN so you can take me for a ride :D I'll buy ya lunch.

Tom
 
Heck Tom, I'll come before I get it fixed! :D

But make it N87 or 39N. Neither of them have landing fees!
 
Tony, I have another encoder.

Tony,

I replaced my ameriking encoder with a serial connection to the skyview. I have the encoder and the wiring sitting in my hanger. If you suspect it is the encoder you can try mine out.

Also, one thing I'm thinking, is that the garmin 327 has to be set correcly. If it's set to recieve serial info and you have it hooked to an encoder it will not work. There is a bunch of settings to play with. If you, or someone was in there playing with settings I could see it geting messed up. Check out the manual for the settings required for your encoder.

Richard
 
Richie,
You have been in my thoughts a lot recently....no, not that way!:D I know you just re-did your panel and I envy your knowledge. I wish I knew what you knew!! I would love to get up there to troubleshoot some things and pick your brain.

I met a DAR who knows you a few weeks ago and we talked about you. I forget his name at the moment but I think he was your DAR too.

What are your plans this weekend? I work Sat but Sunday is wide open.
 
Sunday late afternoon.

I'm probably going to be out there late afternoon Sunday. Even if not this weekend we can get together soon. I wouldn't mind flying down your way either. I've been flying a lot with the new panel and finally feel like I know what I'm doing with it. I have about 15 hours on it.

The DAR your talking about is probably Jon Ross. He inspected my plane. Good guy, fair and thorough.

Anyway your welcome to borrow my encoder anytime. Give me a call this Sunday if you think you might want to fly up. 516 313-8119.
 
Email me

Tony, Also if you don't have the manual for the Garmin GTX 327, email me and I can email you back the manual. You'll see the parts about the encoder setup.

[email protected]
 
Tony, does your plane have a GRT EFIS

I had the same thing happen with our transponder. It turned out I had changed the setting one of the serial ports to bring in GPS info from our new 696. What I did not realize is that the output of that port was sending pressure data to the transponder. Changed it back to 9600 baud and ATC is much happier now.
 
No Bill...it doesn't but thanks for the suggestion. RFazio and I are leaning towards a wiring problem. We are going to make a new harness someday but since we got it to work about 95% of the time.....I was happy to leave it alone for now. Well....it went out for a good hour on the way home from OSH yesterday so it has moved up on the priority list of squawks.
 
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