Humidity and avionics reliability

I can’t prove this but based on recent experience I reckon a lot of these bad display digit segments come back if the plane is left outside in the sun, with no cover on, so the inside gets really warm (but obviously don’t do this in +30C OAT). That seems to dry things out pretty well.

So with installation and an audio panel, I’m getting on for a £ 20,000 upgrade on a £ 30,000 plane.
I’d never make that sort of decision in my business – as you say it makes no sense! ………..But that is G.A. for you!

There is nothing inherently wrong with that. My above comment was a generic one on GA and investment patterns. Before I got the TB20 I was looking at a PA28-181 (40k) and spending another 40k on it, and ending up with an IFR tourer with a FL140 capability for 80k. I am glad I went for the TB20 instead of course (FL200 capability, 2x the range, etc) but that happened only when I was able to get more money. If you have a plane which is in a basically good condition (as a 40k PA28-181 would have been in 2001) and which does the desired mission profile, then spending money on it is fine. It also avoids buying somebody’s can of worms – almost every used plane you buy is a can of worms and generates a list of issues for the first year or so.

3kg of silica gel is a lot I use 0.5kg and have found (by RH measurement) that it lasts about a week. The effectiveness is limited by the continuous ingress of water vapour (unpressurised i.e. non-sealed airframe) to replace the vapour which has been sucked into the silica gel bags.

I find baking them for 1 night at 120C does it, but not just a few hours it seems.

I’d be interested to know if there is any moisture protection built into today’s glass panels.

Based on what I have seen, there is none.

They also use commercial RJ45 connectors which are IDC and these do tend to become intermittent after some years. I have just repaired a 20 year old Tektronix 400MHz scope… took me some hours to find it and it was just this – one wire of a 20-pole IDC connector went open circuit.

As a designer since ~ 1975 this does surprise me because the cost of decent connectors is irrelevant on the scale of avionics pricing.

We are now seeing a steady stream of failures of the 30 year plus old King etc stuff, yet there was nothing actually wrong with those designs or the build quality. They fail mostly because they are shagged by corrosion, dirt ingress, etc. King especially was at least as robust as anything made today and they used mostly decent connectors, or (internally) no connectors. So there is no reason to expect today’s products to behave differently with the passage of time. The BIG difference is that a freelance repair guy working in a wooden hut can’t fix the new stuff!

The products seem to have done well so far, but they have not been around for that long. Time-wise they don’t compare with the 30-40 year old stuff (King etc) which much of GA still flies on, and always will because a €30k retrofit makes no sense on a €30k plane, and very few people would do it on a €60k plane.

I guess they mostly do otherwise we’d all be frequently grounded.

What I see from loads of personal contacts, if there are problems with “glass” cockpits, very few people wash their dirty laundry publicly because they have to use an official dealer to fix it, so there is a relationship to maintain.

It will be interesting how today’s “glass” products work like 20-30 years from now. If there is any issue, a lot of owners will have a lot of fun because most of the equipment cannot be replaced with anything else, short of doing a custom one-off STC which almost nobody will want to do.