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A prebuy checklist for the 21st century European buyer / avionics prebuy

Every good mechanic who knows the type should be able to do a basic mechanical and AD check competently.

But what about avionics? Most mechanics don’t fly, and know little about instruments.

Then you get the European stuff especially for IFR eg the AFMS required to legally fly GPS approaches. This is much more obscure and almost nobody (off EuroGA ) knows about it.

How about throwing together a checklist?

Administrator
Shoreham EGKA, United Kingdom

I am definitely interested in the topic but I have little to contribute to it. I will however keep track of the thread and save the useful information in concise form under http://pilot.uraster.com.

LSZH, LSZF, Switzerland

Peter wrote:

Most mechanics don’t fly, and know little about instruments.

I’m lucky – my current mechanic is experienced DA42 pilot and knows a lot about avionics.

LDZA LDVA, Croatia

Something came up recently which made me come back to this old topic. Most (smart) people do a prebuy but almost nobody includes a comprehensive avionics check. In fact most buyers are not able to do a comprehensive avionics check simply because they are not familiar with the actual boxes in detail. And that can turn out to be very expensive…

If I was buying a G1000/GFC700 equipped plane I would not be able to check out most of it…

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

…but almost nobody includes a comprehensive avionics check.

What makes you think that? The advice that was given to me in the early 90ies (when I was buying shares in two aeroplanes) and which I have passed on ever since is this: Before even making an offer to the seller of the plane, get him to compile a list of every bit of avionics installed with type/part number (including leading and trailing "A"s or "B"s which are often forgotten and which can make a big difference between approved or not-approved!) and possibly also serial number. This should also include “hidden” bits like blind encoders, ELT, glideslope receivers, interfaces and similar. Take that list to the guy who will do the avionics part of each annual inspection once you have bought the plane and have him check it out. If he charges an hour or two for his time this is definitely worth the expense, because it can save very expensive surprises.

Last Edited by what_next at 04 Jul 10:38
EDDS - Stuttgart

What makes you think that?

Stuff I hear from pilots.

I suspect it was easiler in the 1990s when you had individual avionics which all did the same job (HSI, etc). Probably the autopilot was the only complicated thing back then.

Administrator
Shoreham EGKA, United Kingdom

Well I for one have zero idea about avionics and it really would be great to have some guidance about which units are good/required and which aren’t.

I imagine the following situation for comparison: someone who’s buying their first high-end gaming PC. They now have to decide on what type of CPU, what kind of GPU, what kind of RAM and what kind of HDD to buy. Not to mention all the other components. I have been involved in that scene since age 10 when I got my first PC and even I have a hard time keeping up with the cryptic designations the hardware developers keep coming up with. But I am a regular reader of a gaming magazine which goes to great lengths to test and evaluate all relevant hardware and publishes recommendations for prospective buyers on a monthly basis.

Now what would be the avionics equivalent for that?

Low-hours pilot
EDVM Hildesheim, Germany

The avionics business is much slower moving than the PC hardware business (I have built all my PCs for many years).

So it is feasible for a clever pilot to become familiar with most of the stuff that’s currently out there. However, it is rare for pilots to acquire such an understanding – even for planes they own. I think this is because most flight, even IFR flight, is very simple in reality. For example my late-1990s KLN94 does everything needed for IFR in Europe, except LPV approaches.

Also, every PC is an “IBM compatible” PC so will run any version of Windows (or even MS-DOS) and then you can run any application software which works under that version of Windows. Avionics does however present many different user interfaces and you may literally have to read a 300 page manual to fully cover a current “GPS+NAVCOM box” like a GTN750 or IFD540. You also need a very good understanding of IFR navigation procedures.

To check out avionics functionality on a prebuy check you need to know how the various boxes interconnect functionally. For example a fuel totaliser sends the current FOB (fuel on board) to the GPS which, knowing the flight plan, computes the LFOB (landing FOB). If that connection is broken (or was never wired-up) then the LFOB won’t show but frankly many owners will never notice, because they do only short flights so they don’t need to do accurate fuel management. You would be amazed how many €500k planes with 7hrs endurance never go over say 3hrs. There are many other example e.g. the HSI/EHSI course pointer needs to be wired back to the GPS and then it can be used to set the bearing in the OBS mode, and I reckon 90% of IFR pilots don’t know about that. One avionics guy I know installed ~100 GNS boxes without that connection and nobody noticed

Administrator
Shoreham EGKA, United Kingdom

Yes, many things seem to be different in England, I do get that part.

You may have been lucky, or your “they checked every single system of the plane” comment could just be blind trust since you were not in a position to verify it anyway.

Well, I got a written and signed protocol. And yes, I do trust “that company”, simply because they always did very good work on my airplane.

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