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Reliability of glass in light aircraft

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Reliability of glass in light aircraft

Old 23rd Mar 2022, 09:33
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ika
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Reliability of glass in light aircraft

I’m curious what others experience of avionics “upgrades” is.

We have a PA31 which had an altimatic autopilot and now has an Aspen PFD/MFD and Garmin G600 autopilot.

The old HSI/AI did about 40 years good service, and several still going strong as backups (fortunately). The altimatic used to drift slowly off altitude at higher altitudes but was otherwise fine.

The Aspen has failed multiple times in the few years it has been installed. Generally while manoeuvring in IMC. We have been waiting for an OAT probe for months so no TAS or wind. Last week en route to Chambery it lost Attitude, Altitude, Airspeed and Terrain and could not be used to give heading inputs to Garmin.

The G600 was installed a few months ago and apart from failing to capture localisers was pretty good for a single flight to Norway. Sadly it failed middle of North Sea at night on the way back. After months of wrangling and time taken failing to diagnose error Garmin have agreed to send a replacement unit. Ironically we won’t be able to test it until the Aspen is serviceable again.

Fortunately I am reasonably happy hand flying using an old vacuum AI in a less than optimal panel position and compass but it does beg the question why pay a fortune to move the useful instruments to the side.

I would have expected modern bloody expensive certified solid state electronics to be less fickle than 40 year old moving parts and analogue components designed in the 70s.

I am also unimpressed at the responsiveness of Aspen and Garmin.

What are other people’s experiences?

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Old 24th Mar 2022, 04:27
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My personal experience with product support

Sandel terrible, Aspen pretty bad, Garmin mostly OK
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Old 24th Mar 2022, 20:10
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Originally Posted by ika View Post

I would have expected modern bloody expensive certified solid state electronics to be less fickle than 40 year old moving parts and analogue components designed in the 70s.

?
Well. I'd suggest that's your mistake right there. I've no experience directly of the units you mention, but have had similar issues with other stuff.
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Old 26th Mar 2022, 21:52
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I think statistically glass is more reliable. That's little consolation for someone who has had problems with it.
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Old 26th Mar 2022, 23:10
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Except of course glass is all or nothing !
Apart from the very few back up instruments demanded and l suspect these can also be "glass", so still vulnerable to electrickery.
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Old 27th Mar 2022, 09:56
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Originally Posted by mikehallam View Post
Except of course glass is all or nothing !
Apart from the very few back up instruments demanded and l suspect these can also be "glass", so still vulnerable to electrickery.
If backup instruments are glass they must be capable of being powered from a separate source, ie. Battery back-up
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Old 27th Mar 2022, 11:38
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With glass you have several instruments in/on one device, so you potentially lose redundancy.

Just to contrast; Airbus A320 family has fantastic glass, but has: 6 screens, 3 display management computers, 2 flight warning computers, 2 system data acquisition computers, and multiple power sources; All fed from 3 independent air data inertial reference systems, each with their own static, pitot and AoA vanes, 2 GPS systems and 2 OAT probes. Information can be switched to other screens in the event of a failed screen.

Not the same situation as a GA glass device and not the same 'mission' of course, but it just goes to show how much redundancy has been added. Glass can be wonderful but redundancy still needs to be there.

If one is relying on a single glass device, make sure your back-up instruments are both present and fully operational ! (Airbus still has back-up instruments as well as all that glass and redundancy).
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Old 28th Mar 2022, 21:37
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There are multiple failure modes in glass just as in a six pack. For example:
If your Pitot gets blocked it won't make any difference if you are glass or six pack. (well unless you are glass and have a GS read out)
If you are all electric either glass or six pack you will lose all your instruments. Unless you have a back up power supply and most aircraft do.
If you have a Vac system you may only lose a few instruments, but it will happen much more often. (And if you think you are going to be alright in IMC you will need to be very current. if you think you don't need a back up, and some do, then have a look at the accident stats. They will show you just how serious it is to lose your Vac part of your six pack.)
If you have an electric AI then it can fail on its own. Equally if you have an ADHARS it can fail on its own, its just much less common.

There is one failure mode unique to a glass screen. With a glass screen there is the chance that the the display itself will fail. In that case you will need to have your back up instruments, all aircraft with glass will be well advised to have a backup of some sort for anything mission critical. But that applied to everything be it glass or steam.

If you like a six pack, fine its not a problem. But its pretty clear a glass screen has advantages. There is good logic behind the increase in glass screens, they are better. If you don't like them fine, but that wont make them poor. They are here to stay and will just become more common. I've never heard of anyone taking out a glass set up to replace it with a six pack. I'm sure its happened. But I do know of a lot of aircraft where a six pack has been removed to be replaced by glass.

To my mind there isn't much point in comparing CAT with GA on any level, and this is no exception.

Last edited by blueandwhite; 31st Mar 2022 at 23:11.
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Old 29th Mar 2022, 14:31
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I fitted from a new build twin Dynon 10inch Skyviews in my aircraft and over the last 6years both screens have failed!...coloured vertical lines only shown! Each failure at separate times incidently resulted in returning the units each time back to Dynon in the USA for repair. Not good!
So be aware that although flying behind glass is much nicer and you generally fly with much more information at your fingertips it is not foolproof. You always need backups.
Personally if I were building a simple type Permit aircraft today I would probably just fit old fashioned steam gauges. When and if one or the other steam gauge fails it is then less of a problem/hassle and certainly not as big hole in your pocket!
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