The main reason that the plumbing at the back of most panels is so bad is that anyone who try’s to do the job to a very high standard will not get any business because they will be undercut on price by the cowboys.
Most pilots only see the front of the new Avionic installation ……… Not the back and so as long as all the flashy functions work when the new kit is delivered all is OK and very little consideration is given to what is going to happen five or so years down the line. I know of one guy who purchased an aircraft that was approaching death trap status just on the basis of a new Garmin box or two, the fact that the rest of the aircraft was so bad that the CAA inspected the aircraft to see the string of MOR items that I was compelled to raise illustrates the general level of ignorance or self delusion within some sectors of the pilot population.
A few years back I was asked to oversee a major Avionic upgrade for a customer, I got a number of quotes the cheapest was IRO £1500 cheaper than the most expensive, on further investigation the cheapest quite did not include slaving the DME to both the NAV boxes or any provision for Avionic cooling to hi light just two of a number of issues.
As with all things you will only get what you pay for, so in a highly competitive market some people cut corners and the more reputable loose business to those who do simply because the customer sees only the price tag of the installation. While you can sometimes explain the cost of a top quality job to an individual aircraft owner I have yet to meet a syndicate that buys anything except at the very lowest quote.
Can you guess why the fittings for the 306 hose (which itself is far more sturdy than the hose normally used for pitot/static) are marked “for experimental use” when the “apparently proper” ones are for the 303 hose which is a wire braided higher pressure hose and completely way over the top for this application?
I tested one of the “experimental” fittings to destruction. To break it, the “screw” end had to be in a vice and the bit which goes into the hose had to be bent with a large pair of pliers. Then it broke off. This will never happen in normal use. Anyway, if the fitting is correctly assembled with the correct very small gap, there is no way to exert a bending moment on the internal tube. Any bending will result in a pull along the axis and the fitting is much stronger there.
I am sure a lot of avionics wiring is bodged but nobody finds it because almost nobody looks behind there. My favourite example is this – look under Installer Performance.
I know a number of people who run syndicates and most of them have great difficulties getting an agreement on costs.
The nice blue anodized fittings are lesser used because of cost, weight, and complexity of assembling the hoses. Mis-assembling the hose is certainly possible, and detection of the error is not always easy. They are otherwise excellent when correctly installed. Older Cessnas, and my Teal are all this style of fitting. But, the desire to reduce cost and weight has lead to the use of plastic hardware. For pitot static systems on non pressurized aircraft, they work perfectly well, if used as intended. “rubber” type hose tywarpped over barbed fittings also works, but does seem crude. I occasionally see it in a supplemental installation, though I try to change to the plastic/nylon hardware when I can.
I got a reply from the supplier of those blue Aeroquip fittings.
Apparently there is nothing “experimental” about them – it was a batch they got from another well known aviation supplier (for whom they act as a retail distributor, and who is well known for charging a lot extra for an 8130-3 etc) without the traceability docs, and listed it apparently in error on their main site.
This morning, the “experimental” stock has vanished. I looked last night and they were showing the stock in two lots; one “experimental” and the other normal (traceable) but it looks like early this morning they have taken out that non-paperwork stock.
I wonder what type of grease is best suitable for lubing the inner part during assembly – for pitot/static use? Almost everybody uses Grease 7 – well those who don’t use WD40 
this AN system really is overkill in aircraft systems and rather clumsy for instruments you are dealing with. It is appropriate for Yaks and AN 2 with up to 60 bar pneumatics. But you are supplying only a few bar pressure so why go for hydraulic designs ? In industrial production the kind of push-lock fittings for polyethylen hose is applied worldwide now, so when this is OK for producing millions of Mercedes, BMW, etc. with up to 16 bar pressure your examiner for the annual should accept this for next to no pressure systems in aircraft – unless he is a complete idiot. Taper thread fittings are not used in hydraulics and require teflon tape or Loctite on the threads for tight sealing. I´d go for designs using O-rings for seal and definitely for the pneumatic push-lock system easily available for metric or imperial threads, starting with 3 mm hoses for low airflow – great for static or airspeed connections to instruments. If you don´t like the push-lock fittings you may still find the threaded type for the same calibrated plastic hoses but clearly the industry prefers the modern type. Just browse your Ebay categories for handy fittings to make life a lot easier for the mechanic once the next annual is due. Look here to get the idea :
http://www.ebay.de/itm/Einschraubsteckverbinder-mini-Steckverbinder-alle-Grosen-/320828027084
http://www.ebay.de/itm/Steckverbinder-Einschraubverbinder-alle-Grosen-/321161952007
http://www.ebay.de/itm/T-Einschraubverschraubung-Schraubverbinder-drehbar-alle-Grosen-/221289644781
http://www.ebay.de/itm/Winkeleinschraubverschraubung-Schraubverbinder-alle-Grosen-/321124574804
Peter, silicon grease works best with rubber or plastics for lubrication, but don´t be overenthusiastic with it, the hose may slip off the fitting.
Thanks, Vic.
Those are interesting fittings and I agree about the overkill…
However the instruments use the American NTP (tapered thread) fittings which narrows down the options a bit.
Also, strictly speaking, for an ICAO CofA aircraft you should use parts with traceability docs, which rules out most Ebay stuff if you are doing something “visible”.
you may be right about NPT thread, I´d try a standard imperial pipe thread pneumatic fitting anyway, it should be close enough to NPT – we are not talking hydraulics, but a mere one or two bar pressure air system. A low strengh Loctite like 243 plus O-ring seal should easily do in this case. According to Mike Bush the FAA would be happy when components are industrial production or supply – as these Ebay items certainly are. So traceability should not be an argument for the annual to a decent mechanic. And you certainly don´t get individual papers for all 14963 items an aircraft consists of ?? Again, this depends on the mechanic, so you better ask him in advance, he might approve this mod. It is clearly not the original design but definitely an optimisation. Why not accept decades of technical development when outdated components show a lack of inspiration in detail ? These original hose clip cum rubber hose connections are definitely a disgrace and a shame for aviation - now these items remind me of traceability ……. ???
Cheers VicHere is a better pic of the back of the KI256 and its lovely neat air hoses
I had a play today with the AN fittings and actually none of them fit, due to the required 90-deg angled ones not having enough room to rotate while being screwed in. The only way is to screw in the two end ones and then make up a “taller” middle one (from 3 parts) and screw that in as last.
There are pipe fittings which get around this “rotational room” business. I know what they look like but can’t describe them.
your troubles did not come unexpectedly to me as I think this AN system is far too bulky for this place. So I really suggest you looking at these pneumatic fittings below. What size of NPT thread is actually required and did you try normal pipe thread ? Provided you apply some mild Loctite or teflon tape the slight difference in pitch really does not matter. I suspect both threads being very close in diameter and so should be fine for next to no pressure. Just don´t tell me these fittings not being certified for aviation whereas rubber hoses and clips said to be so !!! This could only be a joke and a disgrace anyway – not to be published to uninformed people outside aviation.
Vichttp://www.ebay.co.uk/itm/Pneumatic-Push-Fittings-Air-Water-Hose-Tube-ALL-SIZES-AVAILABLE-Stem-/261120824703
http://www.ebay.co.uk/itm/1-4-NPT-Male-1-4-Bsp-Male-Adaptor-Nipple-Air-Water-etc-b277-/110973971376
http://www.ebay.co.uk/itm/6mm-x-1-4-Bsp-Push-Swivel-Elbow-Fitting-s-s-claw-b82-/120920062062
http://www.ebay.de/itm/Winkel-Schwenkverschraubung-Steckverbinder-Messing-alle-Grosen-/220984725349
So traceability should not be an argument for the annual to a decent mechanic.
In fact the FARs do not mention traceability at all….the A&P or A&P/IA needs to ascertain that the component is “airworthy”….having traceability via an 8130-3 or a Certificate of Conformance to an FAA approved design certainly makes it easier to determine airworthiness but is not the only way….
