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gdbird
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Glass panels

Post by gdbird » Mon Apr 05, 2010 10:34 am

I am thinking of instruments for a Europa project, the EFIS products have advantages and they look economical and light but then you need all the extra bits, sensors etc. Being from aerospace electronics, concerns I have is whether they are build for shock, vibration and condensation and whether instead of being static long term products become outdated and obsolete in 3-5 years like most other electronic products.
The traditional DI, AIs etc seem to last for 30 plus years, electronics should but its contacts and corrossion that could kill them plus possibly display technology. Anyone looked into these aspects?
Graeme Bird
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Dave Moore
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Post by Dave Moore » Wed Apr 07, 2010 2:54 pm

Graeme,

I don't know the answer to your question - but it hasn't stopped me replying..! In fact, if you have an aerospace-electronics background, aren't you in a position to tell us 'non-specialists'.!?

Anyway, a couple of comments from me, as someone who has been treading a similar path to yours, i.e. considering instrumentation for a Europa project.

Traditional DI and AH equipment depends on mechanical vacuum systems (mostly). These have a distinctly finite life expectancy, as do mechanical gyros in the instruments themselves. Gyros are also sensitive to shock loading. And they are heavy.

The extra bits you mention (sensors, etc) will be required for either an EFIS/EIS system or a traditional "analogue" system, so no real difference there.

EFIS products do suffer from shock, vibration, condensation and corrosion, hence the requirement for independent back up systems in commercial aviation (and even in LAA-world). However, the uptake of EFIS technology in commercial and general aviation, seems to suggest that EFIS is cost effective, i.e. they are fit-for-purpose. Otherwise, the products from Garmin, Dynon, MGL, etc. would not have survived so long.

In Europa-type projects, we need to keep a sense of perspective. We are day-time, VFR, we are required to have mechanical back up for altitude / ASI / compass. So, really, an EFIS is a "nice to have". There seems to be reasonable chance that an EFIS unit will remain operable for many a year of aviating - and if it does go blank, the consequence should be no more than a minor irritant (and another dent in the bank account.!).

Enjoy your researching.

Dave Moore

gdbird
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Post by gdbird » Mon Apr 12, 2010 9:46 pm

Well, I was looking at the photo in the latest LAA mag of an engine controller or summat and did have concerns, the article said the board had come loose and screws should have a dab of locktite. umm well, I could add a few things
1) EPROM in a socket - big no no, vibrate out, socket connections corrode.
2) commercial electrolytic capacitors - last about 5 years if rated correctly, could go short circuit. Avionics normally use derated metal tantalum. Its the cheap capacitors that normally go first on a PC motherboard.
3) capacitors bent over and blobed with RTV - not much use, should be axial and tied down,
4) board fixed at corners will be like a trampoline under vibration and at resonance the solder joints will fail on large devices
5) no conformal/ varnish like coating to stop moisture causing corrosion, could get shorts from dendritic growth on tined joints. Could get shorts from contamination.
6) connectors, standard commercial tinned or nickle plated - wont last long joints will corrode - need to be gold flashed as a minimum.
7) power transistors/regulators not bolted down, blob of spongy RTV - again copper joints/legs fail under vibration.

all these lessons have been learnt the hard way once.. can good practice just be abandoned?

If this is the build standard of an EFIS costing 2K5 I am not sure I am interested, or in updating the software due to bug fixes, or replacing the unit after 3 years as its no longer as supported product.
Graeme Bird
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gdbird
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Post by gdbird » Mon Apr 12, 2010 10:16 pm

In Europa-type projects, we need to keep a sense of perspective. We are day-time, VFR, we are required to have mechanical back up for altitude / ASI / compass. So, really, an EFIS is a "nice to have". There seems to be reasonable chance that an EFIS unit will remain operable for many a year of aviating - and if it does go blank, the consequence should be no more than a minor irritant (and another dent in the bank account.!).

Well, perspective, I know, I am IMC rated and I dont intend to fly IMC but if you find yourself in unexpectedly lumpy low cloud at 500 ft 5 miles short of Cap Gis Nes or the light tranparent rain turns into a squal, there is only one thing you absolutely must do, and thats ignore your every other perception and trust your instruments... and I wouldnt want to be in the slightest doubt at that moment. So I dont see a AH as nice to have I see it as a potential life saver when the cold sweat forms on the brow, and i think I would want to be sure in that moment that it didnt just contain some cobbled together commercial hardware and schoolboy software that had been tested for a couple of hours in a microlight and had since been updated to fix a few other bugs.
Graeme Bird
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Rod1
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Post by Rod1 » Tue Apr 13, 2010 2:57 pm

”Well, perspective, I know, I am IMC rated and I dont intend to fly IMC but if you find yourself in unexpectedly lumpy low cloud at 500 ft 5 miles short of Cap Gis Nes or the light tranparent rain turns into a squal, there is only one thing you absolutely must do, and thats ignore your every other perception and trust your instruments... and I wouldnt want to be in the slightest doubt at that moment. So I dont see a AH as nice to have I see it as a potential life saver when the cold sweat forms on the brow, and i think I would want to be sure in that moment that it didnt just contain some cobbled together commercial hardware and schoolboy software that had been tested for a couple of hours in a microlight and had since been updated to fix a few other bugs.”

I am also IMCR and I fly a similar aircraft (MCR01). I have an EFIS which of course does vastly more than just an AI. My MGL Enigma is also my main GPS and my only info on engine t&p’s. It is an uncertified unit, which has been sold in large numbers worldwide. Would I trust my life to it? Absolutely not! If it fails I have two backup AI systems (one solid state, on steam). However it is much less likely to fail than a vac pump on a conventional c of a aircraft (based on my experience). The unit has saved a lot of weight; a lot of cost, and it gives me unrivalled situational awareness. The company that produced it are still supporting mono units sold 15 years ago, and the cost of the kit is an order of magnitude cheaper than the equivalent certified kit. If you want something to rely on, spend the money and buy a certified system, but a carefully thought out installation can have many backup systems at low cost so I am quite happy with my setup. :)

Rod1
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