If it is a case of not erecting, then they are probably not being overhauled correctly IAW the service manual. The UK is full of little outfits in wooden sheds, doing repairs of 1970s radios and such, all off the books of course, but that is how most of UK GA (schools especially, IME) like it. Some are good, some not.
If it is other mechanical bits not working then you may just be looking at a generally shagged instrument. For example it is common for glideslope bars to get sticky.
I think it’s a case of the vacuum instruments are very old and been overhauled so many times that I think it’s now a false economy and simply need replacing with new every time they fail.
I would also like to standardise all aircraft with the same instruments.
European disti for Aircraft Spruce
Not sure you can get anything delivered tomorrow however unless you find one on the shelf in the UK. DHL delivers next day in Europe, normally, but that relies on the suppliers actually processing it before their collection deadline. Also the above firm stocks almost nothing; like most useless distributors they order it back to back. Aircraftspruce.com (the US firm) might be quicker in some cases.
BTW if you need to OH a vacuum instrument really every year, something is drastically wrong! I would start with overhauling your “maintenance” company 
OK sigmatek it is.
Does anyone know a good retailer of the sigmatek instruments? Everyone seems only to have RC Allen.
And I need it by tomorrow if possible?
As for the AH well I suspect that’s also about shot as again it’s probably 40 years old and been overhauled 40 odd times. The plan when thus fails is to replace it with a brad new sigmatek unit as well.
Peter wrote:
Not so, sadly. You still need the redundancy.
I wrote that it can be done, not that there are no conditions (like battery backup). FAA policy on this changed about a year ago IIRC.
It is of course possible to get this change certified if someone wants to fund an STC
Indeed, but this is non-trivial for a KI256 replacement for driving the various King autopilots. I recall talking to the owner of one of the major US avionics mfgs (not Aspen Avidyne or Garmin) who had the technology for emulating the KI256 all ready in-house (like the EA100/GAD43 boxes which I think use the ARINC429 pitch/roll from the AHRS to drive an LVDT emulator; a fun electronics project) and he said it is very hard because of the way the King STCs are done. I don’t have any more detail but the bottom line is that nobody else AFAIK has ever succeeded (or bothered). And the market is gradually disappearing, although I am sure far from everybody wants to fit an Aspen which has had a very long history of failures, and likewise for the G500 which is a pricey installation (a few tens of k).
Peter said: ‘They incidentally also make a TSOd electric lookalike of the KI256, but there is no way to generate the paperwork for the installation. So I have that on the RHS…’
It is of course possible to get this change certified if someone wants to fund an STC. And to make it more useful, it could be done as an EASA STC and then get FAA validation under the bilateral agreement. However, it would probably be cheaper if it’s just for one aircraft to fit an Aspen EFD1000 PFD and an EA100 autopilot interface which then gets rid of the KI256. You still need a back-up AI but this can be a simple RCA or Signatek vacuum unit, or alternatively a MidContinent MD4300-411 with integral back-battery.
With the KI256 the usual thing is that it won’t, ahem… erect 
Or it does but takes minutes, when it should be almost instant.
It rarely fails during flight.
Sometimes you get a few degrees of roll to one side, presumably due to one bearing sticking.
I have sent these away to a UK firm but they conned me last time by saying, at the very end and after I paid them, that they lost the ability to generate any paperwork. I believe they ran a scam of working on the back of a 145 company and the arrangement ended. So now I use Castleberry Instruments in Texas, who actually used to make this AI for Honeywell, for a time. They incidentally also make a TSOd electric lookalike of the KI256, but there is no way to generate the paperwork for the installation. So I have that on the RHS…
@Peter
I would really be interested to see that when you find them out.
What are the symptoms in flight ? False attitude indication ? Latency ? Unusual noise ? (I doubt about the last one ;-))
Do you service it by yourself ? Or send it somewhere to get the bearing changed ?
I don’t think you will get an EFD1000 installed for much under 10k in Europe, by the time the installer has got stuck into some 30 year old plane’s wiring, hacked the panel around, etc
Should vacuum instrument, such as AH, be cleaned on a regular basis ?
Maybe, but the one I have cannot be usefully cleaned. What happens is that the bearings wear out, start to stick, and have to be replaced. They cost best part of 1k. I was about to post a photo of my last ones but can’t find them now… IAW the Honeywell service manual, it is “illegal” to oil them.
