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Transponder/Static System Check IFR vs. VFR

Hello EuroGA!

I am a bit confused, thinking about all that new Part-NCO stuff and there have been very enlightening threads already. :)

One question remained: Part-M says that the Transponder and Static System Check is part of the annual/100hr inspection (ELA1). However, I hear that there used to be – and supposedly still are – two different ways to conduct those tests. One for VFR with high tolerances and IFR with obviously stricter tolerances. The Part-M ELA1 implementing rule in Part-M only says:
“The MIP shall contain the following: …Operational test of transponder (if existing). …   Operational test of the pitot-static system. ", and no word about IFR or VFR.

In my opinion the difference of the tests doesn’t really make sense. In the USA I always had to check that the altimeter indicated +-75ft of a known elevation. The same instrument check must (probably) be performed by the PIC under Part-NCO, so why should there be a difference between the two tests? In my opinion, there is no way a pilot could tell if a VFR or IFR altimeter check was done, but he can compare the indication to a known altitude – that’s it.

I would appreciate, if somebody could tell me if there was an implementing rule specifying what the two maintenance checks are (specifying the difference between IFR/VFR)? Or is this even something from JAR times that the CAAs forgot to get rid of?

Ultimately, I wonder if the MIP Static-System Check of the Cessna I fly suffices for IFR (it only has the “VFR” check done).


Last Edited by ArcticChiller at 14 Feb 20:33

Since I have had the same question, I have been trying to find out how this works for France. So I contacted the OSAC, which is the responsible entity overseeing aircraft maintenance in France. They said that it is the responsibility of the “operator” (“exploitant”) to verify that the aircraft is capable from a regulatory and maintenance point of view to undertake a given flight. I don’t know if “operator” in that context could mean my aeroclub, but I would tend to think it means me, the pilot has to go digging into how a plane has been maintained before going on a given flight.

As to the necessary technical checks, they pointed me to this guide P-41-15: Exigences en matière d’entretien de l’installation radioélectrique de bord (IRB) et de la chaîne ATC

There are two parts, 1) the radioelectrical installations (“IRB”, installation radioélectrique de bord) which consist of VHF, HF, VOR, LOC, Glide, Markers, ADF, GPS + ABAS, DME, ELT and Transponder as well as “other systems”: ACAS, Radio Altimeter, TAWS and Weather Radar. And 2) the “ATC chain” (altimeter, altitude encoder and transponder).

The difference between VFR and IFR is in the periodicity of the checks for old IRB equipment (certified before 1980), which is 6 years for aircraft used for VFR and 4 years for aircraft used for IFR. Then it seems that you have to do bi-annual “global IRB checks” (according to Annex 1 and 2 in that document, which are also available in English starting from page 25) if you don’t have a “programme de fiabilité” (? “reliability programme” ?) and want to use the aircraft for IFR. VFR aircraft don’t need to do them in any case. And finally, the periodicity of the “ATC chain” verifications is the same regardless of VFR or IFR.

All very confusing for someone merely renting a plane from an aeroclub, I must say.

Last Edited by Rwy20 at 14 Feb 21:06

This testing is done by avionics company, and has a much tighter tolerance then the indicated 75 Ft. There is no difference between the testing between VFR and IFR. On some countries the frequency of testing used to be higher for IFR.

Your supposed testing says nothing on how an altimeter performs on different altitudes. The same is true for the altitude encoder. The transponder testing also includes sensitivity and power output measurement, amongst many other items, and can not be done without calibrated test gear.


So if it used to be a difference but now the test is the same, I guess this is a relict from old regulations.

ArcticChiller wrote:

So if it used to be a difference but now the test is the same, I guess this is a relict from old regulations.

Nothing basically changed. The interval in some countries used to be larger, and smaller in other countries. Do note that you might be required to follow national regulations on this. In the Netherlands for example, the testing is always the same on all aircraft, VFR or IFR, and also includes testing of navigation equipment, ELT etc.


As Jesse said, it mostly comes down to national regs.

For GA in France, there is virtually two tests : the small altitude / encoder test (VFR / IFR) (1) and the global test for IFR aircraft (2)
The encoder test has now a 5 years periodicity (with an intermediate check between the 2nd and the 3rd year) for EASA aircraft (annex I) if you use DAH data to design your maintenance program.
But if you elect to choose the MIP (which is supposed to be lighter !), you have to comply with the yearly periodicity.
So regarding XPDR / encoder test, for a F-reg EASA GA aircraft, the MIP is actually 5 times more restrictive than the previous maintenance program !
I don’t understand how they ended up mandating a yearly periodicity as EASA SIB 2011-15R2 itself recommends 2 years periodicity.
The only “good news” is that for F-reg aircraft, the light encoder testing can be done by Part 66 staff (it’s not necessary to go to an avionic shop).

Last Edited by Guillaume at 14 Feb 22:01

Thank you for all the information. Now that is a bit bad news, because unlike Part-NCO/SERA etc. this is apparently nationally regulated…

Is this periodicity and national regulation going to change with Part-ML? Will there remain a difference between the IFR and VFR static system check?

Thanks for helping out on this subject, I really don’t know this much about maintenance, unfortunately.

Guillaume wrote:

The only “good news” is that for F-reg aircraft, the light encoder testing can be done by Part 66 staff (it’s not necessary to go to an avionic shop).

You can do so for some other countries as well. The downside is that you need calibrated test equipment for pitot static and at least transponder. This will be quite expensive for someone who doesn’t spend all the time using the equipment.

I do both Part 66 and Part 145, and there is no price difference, as you need all the same tools, manuals, workspace etc. Part 145 can sometimes be more restrictive, so sometimes I have to perform work on Part 66, as that is wider with respect to aircraft types then the Part 145.


ArcticChiller wrote:

Now that is a bit bad news

Under which registration do you fly?

I don’t think it is a bad idea to test this kind of equipment under a certain interval. Many pilots don’t recognize and altimeter which is out by fair amount, even when it is on a level which they can easily check.

This 75 Ft is a good example, which is almost 4 times the allowable tollerance at typical ground levels.

Then with transponders etc you can discover problems (out of tolerance) situations, before your no longer visible. So this you can perform preventative maintenance this way.


Guillaume wrote:

and the global test for IFR aircraft (2)

I guess some of you have had to perform those global tests (bi-annually for F-reg’d aircrafts, flown in IFR). Could you share the fee applied ?
For me, it was 620,- € excl. VAT the last time.

What about you ?

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