Menu Sign In Contact FAQ
Banner
Welcome to our forums

Humidity and avionics reliability

My plane has been having an Annual in the usual unheated hangar for 8 weeks and

  • the KR87 ADF display is faulty
  • the KDI572 DME display is faulty
  • the KX155A radio display is faulty

Admittedly the ADF and the DME were like that to a smaller extent previously.

Obviously my normal hangar is also unheated and until recently didn’t even have a door, but normally I keep a 0.5kg bag of silica gel in the cockpit. During this Annual service I didn’t do that…

This is probably very relevant, but the 8 weeks of high humidity is a fairly direct indication of a vulnerability of some of these avionics, and of the effectiveness of the silica gel which I measured as reducing the RH by 10 percentage points.

Administrator
Shoreham EGKA, United Kingdom

Mine sat in an unheated hangar for 2 months (8 weeks) too. At one point I lifted the carpet in the baggage compartment to open the access panel to the avionics bay and noticed a lot of condensation on the access panel despite having left a dehumidifier there. At that particular time the airplane may have been colder than the surroundings.

After 8 weeks the only snag was that the trim position indicator had a few LEDs that did not work. They came back to life after a 20 minute flight and have been working since.

Eq: Avidyne PFD + MFD, 2×GNS430, S-TEC 55X, GMA340 audio panel, GTX330 XPDR

Last Edited by Aviathor at 28 Mar 06:00
LFPT, LFPN

My aircraft sleeps outside.
I used to have condensation at the base of the windshield. I requested several time a new seal, and now have a really watertight one. Condensation here has disappeared.
Silica may be good, but I guess no thing is better than flying the aircraft, to get rid of the humidity.
As for the KR87, I wonder if it is related with low temperature too ?

@Aviathor
Is your aircraft back in the air ?

PetitCessnaVoyageur wrote:

Is your aircraft back in the air ?

Yup :-) Since Friday

LFPT, LFPN

Coooool :-)

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.

Administrator
Shoreham EGKA, United Kingdom

It will all be in the then-year version of iPad, Peter. Just unroll it, peel off the adhesive backing, and stick over the existing panel. Radio panels included. Sticks best to old fashioned ‘glass’ screens. (Radios will work over 9-10G connections – no seperate antennas needed). And oh, yes, it’s waterproof. And disposable. Etc.

EGBW / KPRC, United Kingdom

Aveling wrote:

It will all be in the then-year version of iPad, Peter. Just unroll it, peel off the adhesive backing, and stick over the existing panel. Radio panels included. Sticks best to old fashioned ‘glass’ screens. (Radios will work over 9-10G connections – no seperate antennas needed). And oh, yes, it’s waterproof. And disposable. Etc.

Can’t see the CAA agreeing to that in such a short 30 year period

The photographs in this slightly related thread suggest those instruments were not designed to survive any significant amount of condensation or high humidity – but I guess they mostly do otherwise we’d all be frequently grounded.

I’d be interested to know if there is any moisture protection built into today’s glass panels. If not we’ll be flying bags of Silica Gel around with us for years to come!!

PJL
EGMD, EGKA

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.

Administrator
Shoreham EGKA, United Kingdom

Hi Peter

A couple of comments – my Piper lives outside, always with a cover on and I regularly leave 3 Kg of Silica Gel inside – I have a temperature and Humidity logger and this reduces humidity by approx 10% ……………(it makes a practical difference also, it feels much dryer inside) ………….so same results as yourself. (It takes hours to dry out the Silica Gel in the fan oven at home at 120 degrees C!!)

After thinking I’d spend the absolute minimum on 8.33; I am now on the verge of opting for an IFD550 – The IFD 540 is nearly £ 11K plus VAT then the USD 5,000 payment to grab the upgrade to the IFD550 when the software is EASA approved. 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!

United Kingdom
13 Posts
Sign in to add your message

Back to Top