AdamFrisch wrote:
As aside, I keep reading more and more on forums about Aspens and G500/600’s that fail in flight. Many of them with weird intermittent failures and red crosses all over in IMC.
In general, the last few years there are FAR more issues with avionics then lets say 10 years ago. It seems avionics design get pushed very hard, to bring it out. It happens to all brands, with a 150% return rate on NEW units (I rejected most units once, some twice). It happens on American hardware just as well. Recently had two diffent items from different manufacturers. One NEW units required SEVEN unit’s before I got working unit, different issues on the others during checkout. On another unit of the same brand, I needed 3 units to get a working unit.
Apart from that all avionics fail. I haven’t seen a single manufacturer who produces equipment that does not fail. The failure rate is different between manufacturers, and manufacturers will generally say that they haven’t seen those issues before, only to find out when you talk to other avionics shop they have the same issues.
AdamFrisch wrote:
As the technology gets older and older (G600 is well over 10 years now), expect this to happen more and more. Just remember how those old 80’s cars with the then fancy new LCD or digital dashboards look or work today – that’s how these systems will be in 20 years time. Try to get an old Casio watch repaired today, or a Camaro z28 speeder, or an Aston Marion Lagonda panel. Unreliable and unsupported.
I do think this is valid point. Manufacturers used to publish very good repair manuals, with schematics, troubleshoot trees, oscilloscope views etc. This has changed to replace the defective board afterwards. Currently most manufacturers don’t allow field repair at all. This makes it more difficult, especially when support is ended, or the manufacturer is out of business.
Garmin has a clever design for themselfs. Being an OEM supplier and with highly intergrated systems. These systems communicate with Garmins own protocols.
Which makes future additions or replacements also Garmin units.
Aspen for example is much more open, and communicates with almost all thirth party hardware, which is a more customer friendly option IMHO. Cobalt wrote:
I agree with the need for proper redundancy, I would want a unit that is completely isolated from the main avionics (I had more failures of the G1000 because the service centre botched a software update,
It is quite easy to do that. That is part of the design as well, it could have been designed more robust at this point I would think.
Airborne_Again wrote:
So a solid state AI will work perfectly fine without any air or navigation data, but the risk of incorrect indications is greater than with a mechanical AI and that’s why you need the additional data for cross-checking. Have I understood you correctly?
For “normal” flight, yes. I don’t agree that the risk of incorrect indications is greater then with a mechanical AI. Some mechanical AI have a warning flag based on gyro speed, others don’t have flag at all. The last can fail as well, without any indication. Mechanical AI’s don’t like aerobatics either, and will tumble if not caged.
On solid state design if the unit feels your are moving based on the MEMS sensor or GPS, but the pitot senses a much lower speed the units knows something must be wrong. In this case likely the pitot. So it will issue a check pitot heat indication, while still displaying the measured airspeed and altitude. This is an indication you won’t get with a mechanical system, so is additional safety. If it doesn’t feel any pitot pressure it will become, airspeed and altitude will be flagged out using a red croos.
On the solid state design, when it feels that you are moving base on GPS or pitot pressure, but the MEMS don’t “feel” this movement, it knows again something is wrong, in this case the MEMS. If the difference is small, it will show something like “cross check attitude”. It will keep showing the AI. If the difference is large, it will red cross the AI.
Jesse wrote:
For “normal” flight, yes. I don’t agree that the risk of incorrect indications is greater then with a mechanical AI.
So then why do systems like the G1000 require airdata and/or navigation data to show attitude information? Cross-checking is a good idea, but on a G1000 if the ADC and magnetometer both fail, then the attitude information will disappear, too.
Jesse wrote:
This is used for cross checking. When this data does not agree one of the data sources is invalid.
It’s not. There is no need for anything but rate gyros and accelerometers. What true airspeed (in particular) does is simply to enable algorithms that make the system erect faster. On the MGL the airspeed can be set permanently (typical cruise speed). It seems though, all this is just the result of sub-optimal algorithms, because there are certified systems with no need for external data other than the gyros and accelerometers.
In general, the last few years there are FAR more issues with avionics then lets say 10 years ago. It seems avionics design get pushed very hard, to bring it out. It happens to all brands, with a 150% return rate on NEW units
I’ve got this confirmed from the USA, too. Staggering how much goes on that we don’t hear about. I guess some companies are “firefighting” to stay above the water.
Manufacturers used to publish very good repair manuals, with schematics, troubleshoot trees, oscilloscope views etc. This has changed to replace the defective board afterwards. Currently most manufacturers don’t allow field repair at all. This makes it more difficult, especially when support is ended, or the manufacturer is out of business.
How true! I have a huge collection of avionics manuals (though not anything like what a dealer can accumulate if he downloads everything to which he gets login access 
) and there is a massive difference between say the 1990s King stuff and the current stuff. Also Garmin never published any MMs (maintenance manuals) which contained detailed schematics… well I haven’t seen any. For example recently the GNS430 MM escaped into the wild and it’s useless for anything other than changing the memory backup battery. (Of course I had this already but anybody who publishes these on an open website gets trouble).
Jesse wrote:
Manufacturers used to publish very good repair manuals, with schematics, troubleshoot trees, oscilloscope views etc
Probably why those KX170 series navcoms seem to last forever. It’s almost as if 8.33kHz spacing was a plot to finally kill them all off!
Welcome to the Kleenex Generation !
