Another reminder to keep sharp in partial pannel and have truly independent backups !
That is an eye opener to me. I never considered double failures due to a common cause, which is obviously at play here.
I am, however, not convinced that keeping the heavy, relatively maintenance hungry and relatively failure prone vacuum system is better than having a cheap, simple electrical backup horizon, or just keeping the turn coordinator – along with your new mini-EFIS. As long as you have two instruments with two independent power sources.
Obviously this double failure is something that should never happen, and Garmin or the workshop has some explanation to do.
If failure modes were truly independent, this would certainly never have happened.
Before drawing conclusions on keeping old equipment for redundancy, I would compare odds. Very much single engine IFR flying is done using a vacuum-driven horizon and a electrical turn coordinator as a backup, and nothing else to keep the wings level. The vacuum system fails once every 700 hours, which (in IMC) leaves the usually confused and unprepared pilot with the classical limited panel, for which he may or may not have trained recently. I have been there (4 vacuum failures, 1 in mist over open sea, and 1 in low IMC). That is a significant and real risk factor. Obviously a backup horizon improves odds a lot and is recommended for flying IMC, but many flies without it – I still do it sometimes.
Unless the double failure EFIS scenario turns out to be recurrent, which I doubt, I think we are still (much!) better off with a set of those than with any combination of classic instrumentation.
Yes, I am hoping to get my Aspen upgraded at the earliest possibility. That is once I get the cash saved to do it.
Antonio wrote:
I do have an Aspen but I elected to retain the old Vacuum AI
Me too. As well as a Dynon D1 as a last resort emergency ADI.
So then the question arises why this installation did not mandate the installation of a 2nd ADI which is totally independent of the GI275 installation, particularly if they are interconnected.
Is a backup ADI a prerequisite for IFR certification in Canada?
The vacuum system fails once every 700 hours
I have ~2500hrs airborne time and no failures. This is probably because when my vacuum indication starts to drop off, the pump is changed. This is every 3-5 years. Pumps are quite cheap.
I am not really sure whether “electronics” is much more reliable. Since electronics has been my hobby and day job since mid-1960s I should of course say “electronics is far more reliable”, and it probably is if you look across a lot of systems, but there are loads of things which can negatively affect electronics reliability… starting with a bad design. Thermal cycling is also a big killer and very hard to do much with; spending a lot of money helps but a commercial product like a GI275 isn’t going to use e.g. milspec metal cased semiconductors.
It is notable that in applications where extreme reliability was a requirement, the solutions adopted were definitely not a pile of electronic components in a box.
the MAX version with SW version 2.11 has different logic which makes it IAS-independent hence supposedly more reliable
This Mooney didn’t have an Aspen but AFAIK the failures were not related to loss of airdata. They were failures of the box in the panel and/or the RSM. Aspen had loads of problems with failures and they started soak testing their stuff. They have/had some videos showing this.
I have never seen a GI275 (neither have most people; it is still a very rare installation) but does it run hot like the Aspen? If so, there is no reason to think its reliability will be any better. The heat is due to AHRS temperature stabilisation.
This is of course Monday morning quarterbacking, but the guy presumably still had a TC, ASI and VSI. Classic partial panel setup, for someone of his experience should not be a big problem to happily fly along.
In any case, I think I’d much prefer big red crosses to the insidious winding down of the vacuum system. In this setup at least you know exactly what’s going on and you know it immediately.
This also is a reminder to have some external, totally independent backup like a Stratus 3 or similar that has nothing whatsoever to do with the panel. Running one of these devices and an iPad essentially gives you a backup glass panel.
They were failures of the box in the panel and/or the RSM. Aspen had loads of problems with failures and they started soak testing their stuff. They have/had some videos showing this.
If the box failed one would assume the owner could not have flown the plane for another 12.5h post incident, then fix the fuel tanks’ leaks and gear but not replace the failed box…
Peter wrote:
This Mooney didn’t have an Aspen but AFAIK the failures were not related to loss of airdata.
That is confirmed by the fact that air data was successfully read out after the incident. As I said, it will be very interesting to find out (if possible) what caused this. It also appears that the box “fixed itself” on the ground…. so the big question is, why would a box like this go into align mode in the middle of a flight.
172driver wrote:
In any case, I think I’d much prefer big red crosses to the insidious winding down of the vacuum system. In this setup at least you know exactly what’s going on and you know it immediately.
There is ample precedence of this and I agree. Better to have a blank indication or a red cross or whatever so you KNOW that box has gone. Cases where people crashed due to wrong indications are well known, most prominently a Korean 747 at Stansted in 1999. We will possibly never know how many GA planes perished that way.
172driver wrote:
This also is a reminder to have some external, totally independent backup like a Stratus 3 or similar that has nothing whatsoever to do with the panel.
I agree. I am quite happy with the Dynon D1 for this purpose. It is, to the fullest extent, completely stand alone. Today I would not hesitate to get a D3 for the same purpose. So one electronic, one vaccum and one battery driven, all completely independent, should give you a good chance. 3 is also an ideal number, as it is quite easy to see which two coincide thus identifying the broken one.
Mooney_Driver wrote:
3 is also an ideal number
Which is why I usually keep one of my iPads in AI mode with the third independent IRU in the GTX345: if the Aspen (#1) and the vacuum (#2) disagree, then it is the GTX345 (#3) which will tell which is the right one. Worst case but less evident I can use the T&B (#4).
My airplane used to have an electric (bu mechnical) AI at the lwr RH of the LH instrument panel but I replaced it with the mechanical engine instrument you can now see left of the GNS430…if I do lose all electrics I still have mechanical engine instruments and my vacuum AI…chances with two independent ipads, a backup battery on the aircraft , a main plus a stby alternator and a backup battery on the Aspen? Maybe low, but it is not unheard of that a lightning does away with most electrics!
