In an effort to improve aircraft reliability we decided that when a gyro instrument fails that we would by brand new units in the hope that they would last longer than the 40 year old units that were costing us 400 quid every 6 months to repair.
Unfortunately the brand new 1200 quid sigmatec AH has just failed after 14 months and about 600 hours.
This lasted much better than the 1200 quid RC Allan AH which failed after about 3 months and 100 hours. Although this was repaired under warranty which of course annoyed me big style as I didn’t want an overhauled unit in the first place.
Does anyone have any recommendations for companies that offer a quality repair?
600hrs on a vacuum AI is not too far out of line IMHO. 100hrs is obviously outrageous but I once had a KI256 ($10k list price) fail after 100hrs… perhaps not coincidentally it happened after that Icelandic volcanic ash business. Most of my KI256s lasted only about 500hrs. I have a shelf spare.
However you can knacker a vacuum AI fairly quickly if the air is not filtered properly, so check the filters are properly done up. Also make sure there is a filter between the vac pump and the instruments, otherwise a disintegrating vac pump will shoot a load of debris back up the vac pipework and knacker the AI. Most people think that filter is pointless, and it is, until…..
I think these simple instruments can be done by a range of firms, even some in the UK. The last firm I used however took quite a few months to do my spare KI256 so I am not sure I want to recommend them. I have some here under “instrument repairs” but apart from Castleberry in Texas (who are the best) I haven’t used any of those for a while.
One needs to have shelf spares of these items, to avoid significant downtime.
Here is another thread.
I would check what your vacuum is being regulated to. Too much vacuum and wear out gauges prematurely. And yes, make sure all your filters are being changed annually.
It is also imperative to use a vacuum transducer and suck out all your lines during vacuum pump replacements. As stated before, when a pump fails, it most likely will shoot bits up stream.
Another leading cause of failed gyros is when moving the aircraft on the ground after shutdown and before the gyro has run down…or re-energizing by restarting before they have fully run down… it can take 15-20 minutes to fully run down. Hard landings can also damage gyros! 
https://www.casa.gov.au/file/182131/download?token=DDov5Wkj
[ local copy ]
I wonder if that is real or an OWT. Moving a plane around is basically just horizontal acceleration and yaw. And if you sit inside a plane while it is being moved, the G you feel is miniscule, compared to the G one can get in flight.
Peter wrote:
I wonder if that is real or an OWT.
Well I’m sure many would agree that CASA is full of old wives!
Surely in 2017 you would replace it with a drop-in solid state device?
Not if it is a required separate backup. Electrical AIs are no good as a backup because if you lose electrics you lose them too. There is a certification route, available in some cases, involving a backup battery for the instrument. Also these things aren’t cheap – various past threads – example. They tend to cost a few k upwards.
Not if it is a required separate backup.
True.
Electrical AIs are no good as a backup because if you lose electrics you lose them too.
The world’s most widely sold SEP (Cirrus) has all electrical instruments. So do the Diamond aircraft. And the Cessna T240 (formerly known as Lancair Columbia.300/350/400)
Some of these airplanes have a backup battery. Others have two completely independent electrical buses each with a battery.
Peter wrote:
They tend to cost a few k upwards.
Compared to 400 per year in repairs (+ downtime and irritation), that is hardly a difficult decision.
