MikeOH

Not a doc, but there are TWO differences that come to mind vs. 'holding your breath.' One, you don't realize the oxygen is NOT in the atmosphere you are breathing and you breath it OUT of your lungs. Two, the partial pressure at altitude is very low (doh!), there's not as much O2 even if you do hold your breath it's not going to last 'as long.' I imagine these tables assume you are breathing, not holding your breath.

Here's my theory: You have a 'weak/intermittent' short to ground on the the #2 comm radio's PTT input. Something internal to the the PMA450 is providing a 'pull-up' path to the #1 comm's PTT input which prevents #2 from going to TX most of the time (i.e., when the 'short' is weak...when it is a 'strong' short to ground #2 transmits) AS LONG AS #1 has power. When you pull #1`s CB, that 'pull-up' is now gone and #2 goes to TX continuously. One way to check this is to put BOTH transmit (pilot and co-pilot) select switches to comm #2...my guess is that comm #2 will go to continuous TX as the pull-up path to #1 will likely be disconnected. You're wire wiggling pretty much confirms an intermittent short, and Jerry's suggestion to check pin 30 to ground (if you can get to it) is a good one. Good luck with tracking down exactly where the wire is shorting...NOT fun! You might look for where wire bundles come in contact/wrap-around metal structures, especially sharp edges. Could be inside a connector back shell...shield wire/foil contacting the back of a pin.

We are in violent agreement! I've don a poor job of making that clear, I guess! Your post is EXACTLY why I find these kind of threads so amusing...all this discussion about regulatory minutiae and documentation. All this agonizing over where to get 'approved data',...what the FAA will accept,...blah, blah, blah. Find someone competent, show them the old part, and let them make a new one out of the same material. The hardest part is finding someone competent... and that is competent enough to know when what you want is beyond his abilities.

Makes sense. Thanks!

Curious what you are using for safety? I was taught never to trust the O-ring in an hydraulic jack. Always used safety stands with cars, and aircraft jacks have safety wheels built-in.

Well, now that's the rub, "...if done correctly." So, if the plane's in annual, in theory, that should mean "it's done correctly." But, I think we all know that isn't really always true. So, the question becomes, after the fact, will the FAA and/or the insurance company do a deep-dive on the logs to determine that an OPP was NOT 'done correctly?' My point is that I'm a lot more worried about the insurance being denied than the FAA. I seriously doubt claims have been denied over illegal OPPs. Hence, my amusement with all the hand wringing over how to 'properly' produce an OPP.

Which was my point about being pragmatic

I read all of these 'arguments' with a bit of amusement. It seems to me the REALITY is if INSURANCE claims will be DENIED if the cause of an accident is somehow related to an OPP. Absent that evidence (denied claims) I will continue to take a pragmatic approach to properly maintaining my aircraft. The FAA and their after-the-fact interpretation take a distant second place to whether my insurance will be in force.

I'm pretty sure I do; I'll check next time I go the hangar. Thanks for the suggestion!

Yes, quite possible the intercom was out for some time prior. If I'm not having a squelch problem I don't touch it. Honestly, I'm hoping it's just a string of bad luck. Much preferable to tracking down intermittent electrical issues in a 50 year old aircraft! I'll crawl under the panel and see if I can ID some common ground points and check their integrity. Beyond that, I'm going to take a 'wait and see' approach absent any other suggestions. Thanks, all

Hi Greg, Thanks for responding! Yes, at the moment, everything is working (except for the intercom that I haven't yet replaced/fixed). The Garmin, G3, and intercom are all on the CB switched Avionics buss. Nothing else has burned up....so, far. I have no idea if those items share a single point ground...and, no idea how to track that down...many wires, all white, bundled together, buried behind the panel and, I'm not sure my back is up to the task Does the electrical system have any (effective) overvoltage protection system? Probably well before the days of transorbs and the like, but curious if the system is 'clamped' at some voltage. What kind of spike could occur with a temporary VR/alternator failure? Thank you!

"Your papers, please!" And, you are here to tell us that is, "a total non-event," and are, apparently, only too happy to comply with gathering them all up. History is lost to many, I'm afraid. Sad

Well, I'm going to be mean...Too Stupid for Arby's (They advertised jobs on pizza boxes for gawd's sakes!) (But, I'm nice to 'em, too. They can easily make my life more miserable than going through airport security already is)

Good to know! I suspect mine have been neglected...annual coming in December.

Hmm, must have taken out the sound-proofing by the time Mooney built my F

What Garmin provided with the repaired unit left a LOT to be desired. In it's entirety: "Verified problem. Replaced main board and display lens. Tested and met all specifications." Pretty disappointed. Never flown in rain. Never washed with water (use Wash-Wax-All). Yuup. I'm hoping one of the avionics guys here will see this thread and take pity on me

No reason to. The G3's ONLY electrical system monitor is system voltage. And, as an EE, and as previously stated, there are NO clues in the system voltage as far as what the G3 records: stable at 13.8 volts right up to the point where the G3 'froze.' Subsequent downloads show the same stability. If this is NOT just coincidence, then it's a transient event whose source remains a mystery.

Thank you! That's the kind of 'out-of-the-box' idea I was hoping for. I'll check that out.

Well, I have been flying since with no issues. And, I have pulled the G3 data with no anomalies seen. G3 is at its highest sampling rate, but that's not going to capture micro, or even milli, second transients. Never any popped CBs, or over-voltage indication. Absent that, I'm not concerned with fire, but with more failed avionics. While I appreciate the suggestion, taking it to a shop with NO presenting symptoms sounds like a great way to spend hundreds, or thousands, of dollars looking for ghosts. I am a practicing EE, so it's not like I have no background. But, yes, some intermittent in the VR/alternator system would seem plausible; was hoping someone here had seen and fixed the same kind of problem. I brought up this over-voltage theory with the avionics shop I took the blown GN430W to, and the owner seemed to think that was HIGHLY unlikely as the WAAS models are universal input (switch-mode power supply) good up to something like 40 volts. Anyone know what voltage an alternator can reach? Also, isn't there an overvoltage 'clamp' in the system?

So, yeah, I can and I did.

I've owned my M20F for two years and have not had any avionics problems...until the last month. On a recent flight my G3 Insight engine monitor 'froze' with a random pattern on the screen. I was IFR and did not want to cycle power during flight. After landing the G3 reset after cycling power and has been fine ever since. However, the next morning, the GNS430W was dead, and no amount of cycling power changed that. It took $1200 and a trip to Garmin (see my "Black screen of death" thread). Now, the PM1000ii intercom is dead. It may have failed on the trip above because it 'fails safe' to pass through and it was my wife that noticed on our last flight that she could barely hear. No response from the volume or squelch controls, but unit is receiving power. This looks all the world like a serious over voltage event occurred, but I have ZERO idea what would have caused it. The G3 data showed a stable 13.8 Volts right up until the unit 'froze'...and, has shown the same since. Obviously, I'm concerned about this happening again. Unless, this was just coincidence. Anyone ever had something like this happen? I'm at a loss for troubleshooting ideas as this appears to be the mother of an intermittent: a single event. Now living in fear that this will happen again...

I guess that makes sense. Still curious If the data shows over age 70 pilots actually having a higher accident rate.

I'm guessing you're going to be calling your doctor

Is it correct to infer that over 70 pilots would not have this issue with a non-RG aircraft? And, if so, it would imply the gear-up accident rate increases for those pilots over 70....are there data to actually back that up, or is this just 'caution/paranoia' on the part of carriers?

Seems like you could just use a spot of epoxy to hold the nut in place. I did it the 'hard way' with painters blue tape and an open-end wrench; really wasn't that hard.Or, maybe it just seemed easy after what a TOTAL PAIN IN THE ASS putting the clamp around the frame tube was!! Gawd, that was two years ago and the memories still haunt me....makes safety wiring a prop look easy!