Do instruments need to be TSO'd for a certified IFR aircraft?

[SteveR]

Can anyone clear this up for me? I know TSO stands for "Technical Standard Order" and is apparently a minimum standard for equipment to meet when manufactured, but when is one required to use TSO'd equipment? Is the minimum equipment for a specific type required to be TSO'd, and nothing else matters?

My primary question is the one in the title...do instruments need to be TSO'd for a certified IFR aircraft (altimeter, Attitude Indicator, Airspeed, etc.)?

 

[Bob Noel]

fwiw - I'm just an owner.

No, the equipment does not need to be TSO'd, unless the FAA regs state that
a specific piece of equipment must meet some requirement. For example,
"ATC transponder equipment installed must meet the performance and environmental requirements of any class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the appropriate class of TSO-C112 (Mode S)."

I don't believe the regs state anything wrt TSO requirements for certified IFR
aircraft flight instruments such as the airspeed indicator.

 

[gismo]

fwiw - I'm just an owner.

No, the equipment does not need to be TSO'd, unless the FAA regs state that
a specific piece of equipment must meet some requirement. For example,
"ATC transponder equipment installed must meet the performance and environmental requirements of any class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the appropriate class of TSO-C112 (Mode S)."

I don't believe the regs state anything wrt TSO requirements for certified IFR
aircraft flight instruments such as the airspeed indicator.

AFaIK, many instruments in our planes have to be TSO'd per the certification standards for the airplane when it was first certified. That's in addition to the requirements in the FARs. Also many such requirements are spelled out in Advisory Circulars such as the one governing IFR GPS installations. If no standards were needed for things like flight instruments we could install all sorts of devices that can only be used in experimental homebuilt aircraft.

 

[Bob Noel]

AFaIK, many instruments in our planes have to be TSO'd per the certification standards for the airplane when it was first certified. That's in addition to the requirements in the FARs. Also many such requirements are spelled out in Advisory Circulars such as the one governing IFR GPS installations. If no standards were needed for things like flight instruments we could install all sorts of devices that can only be used in experimental homebuilt aircraft.

Instruments have to meet the standards appropriate for the intended use.
I have a certified installation of a DME interrogator in my aircraft. The
King KN-64 is not TSO'd, but the installation is certified via an STC.

Technically, you can get a GPS installation certified (via STC, amended
Type Certification, or Form 337) if you can show the equipment meets
the performance requirements of the TSO even if the GPS equipment
itself doesn't actually have a TSO approval. It won't be easy, and people
usually wouldn't try it, but it can be done. But that doesn't really help
the OP.

I wish the FAA website didn't breakup the various part 23, 91, etc. It
would make searching for TSO requirements soooo much easier. Anyway
I didn't find much in the way of TSO requirements for stuff other than
GPS, ELT, Mode-S, TCAS, TAWS.

 

[weirdjim]

My primary question is the one in the title...do instruments need to be TSO'd for a certified IFR aircraft (altimeter, Attitude Indicator, Airspeed, etc.)?

First of all you have to tell me what a "certified" IFR aircraft is. I don't recall seeing that word in my copy of the FAR.

Jim

 

[weirdjim]

For example,
"ATC transponder equipment installed must meet the performance and environmental requirements of any class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the appropriate class of TSO-C112 (Mode S).".

Read it VERY, VERY carefully. It doesn't say it has to be TSO'd, just meet the performance and environmental requirements. Great Lakes Instruments fought this out with the FAA about ten years ago.

Jim

 

[Bob Noel]

Read it VERY, VERY carefully. It doesn't say it has to be TSO'd, just meet the performance and environmental requirements. Great Lakes Instruments fought this out with the FAA about ten years ago.

Jim

ok, bad example (or actually a good example of what the real requirement
is).

 

[peter-h]

This is a very interesting field...

AIUI, there are two issues

1) Some reg requires a TSOd instrument - in this case you have no choice. I believe one example is an IFR GPS (if somebody can find a reference to the contrary I would love to see it as it would cause a storm here in the UK and probably everywhere else )

2) Some reg requires a specific minimum performance (a TSO is just a paperwork-easy way to comply)

AIUI, case 2) can be dealt with by using a DER to generate Approved Data, and the you can install "anything". This can be very expensive though. An example might be a satellite phone which is "removable" but its car holder is not certified so cannot be permanently installed unless somebody generates the Approved Data for it. A more mundate example would be the installation of a backup oil pressure gauge; if all the parts are TSOd then an IA can sign off the installation (AIUI).

 

[Bob Noel]

> AIUI, case 2) can be dealt with by using a DER to generate Approved
> Data, and the you can install "anything".

AIUI - yes, with approved data you can indeed install any box or
device

The trick is to remember that the set of data needed includes
information about the installation, not just the box/device.
In other words, the TSO approval provides only a subset of
the approved data needed for an installation.

> A more mundate example would be the installation of a backup
> oil pressure gauge; if all the parts are TSOd then an IA can sign
> off the installation (AIUI).

That IA can only sign-off the installation if there is approved data
for the installation.

 

[peter-h]

That IA can only sign-off the installation if there is approved data
for the installation.

Indeed, but let's take the case of a second altimeter. You have to

1) make a hole in the panel

2) screw the altimeter in the hole (4 screws)

3) connect it up to the static system, with a piece of tube.

Let's look at these.

1) presumably requires an A&P for that level of "hacking" but nothing else. Some UK avionics shops would say you need a DER a) because it is a structural change and b) a DER is mandatory for anything not on the original TC

2) the screws and nuts need to come from a batch accompanied by a Certificate of Conformity / 8130-3 etc and a copy of that CofC needs to be included in the work pack

3) the tube and the T-union needs to come from [as above]

I don't see Approved Data existing (in practice) for such an installation as a whole - otherwise the altimeter mfg would need to get an STC (which AIUI is no more than Approved Data) for everything under the sun that flies. How is this dealt with?

Or the altimeter (make and model) and the installation details are on the aircraft mfg's Type Certificate, in which case any A&P can just install the lot, without a 337 or any other external approval.

In a lot of this stuff, the question arises as to what exactly an IA can do. It does sound like an IA has no authority higher than an A&P because the strict position is that an IA still needs the Approved Data.

This apparent total lack of discretion on the part of an IA is certainly not common industry practice!!

One possibly famous case is the installation of a Concord battery in place of a Gill one. I have it from two DARs (DARs) that Part 43 Appendix A (the list of Major Mods) lists everything which the FAA lawyers wanted to be a MM, and if they wanted you to read in between the lines they would have put it in there. But since many installers want to cover their six o'clock, they submit a 337 for everything; this puts the "do I need a DER?" ball in the FAA's court, but (according to statements from FAA inspectors at various seminars) inundates the FAA with huge numbers of silly 337s. And, back to that battery issue, one aircraft owner has it in writing from an FSDO that a similar-size similar-capacity battery is not a MM (the words in App A are "a basic change to the electrical system") and is thus within the A&P's discretion, and definitely within an IA's discretion to just install. A 337 is for a MM only.

The Q then arises as to why do Concord etc bother to obtain STCs. The answer I got was that they do it for marketing reasons; a lot of installers won't read 43 App A and if they do they don't want to interpret it.

I am confused, but I know this debate has been done to death in so many places...

 

[flyersfan31]

One possibly famous case is the installation of a Concord battery in place of a Gill one. I have it from two DARs (DARs) that Part 43 Appendix A (the list of Major Mods) lists everything which the FAA lawyers wanted to be a MM, and if they wanted you to read in between the lines they would have put it in there. But since many installers want to cover their six o'clock, they submit a 337 for everything; this puts the "do I need a DER?" ball in the FAA's court, but (according to statements from FAA inspectors at various seminars) inundates the FAA with huge numbers of silly 337s. And, back to that battery issue, one aircraft owner has it in writing from an FSDO that a similar-size similar-capacity battery is not a MM (the words in App A are "a basic change to the electrical system") and is thus within the A&P's discretion, and definitely within an IA's discretion to just install. A 337 is for a MM only.

The Q then arises as to why do Concord etc bother to obtain STCs. The answer I got was that they do it for marketing reasons; a lot of installers won't read 43 App A and if they do they don't want to interpret it.

I am confused, but I know this debate has been done to death in so many places...

And people wonder why flying is so expensive....

 

[gismo]

Indeed, but let's take the case of a second altimeter. You have to

1) make a hole in the panel

2) screw the altimeter in the hole (4 screws)

3) connect it up to the static system, with a piece of tube.

Let's look at these.

1) presumably requires an A&P for that level of "hacking" but nothing else. Some UK avionics shops would say you need a DER a) because it is a structural change and b) a DER is mandatory for anything not on the original TC

2) the screws and nuts need to come from a batch accompanied by a Certificate of Conformity / 8130-3 etc and a copy of that CofC needs to be included in the work pack

3) the tube and the T-union needs to come from [as above]

I don't see Approved Data existing (in practice) for such an installation as a whole - otherwise the altimeter mfg would need to get an STC (which AIUI is no more than Approved Data) for everything under the sun that flies. How is this dealt with?

Or the altimeter (make and model) and the installation details are on the aircraft mfg's Type Certificate, in which case any A&P can just install the lot, without a 337 or any other external approval.

In a lot of this stuff, the question arises as to what exactly an IA can do. It does sound like an IA has no authority higher than an A&P because the strict position is that an IA still needs the Approved Data.

This apparent total lack of discretion on the part of an IA is certainly not common industry practice!!

One possibly famous case is the installation of a Concord battery in place of a Gill one. I have it from two DARs (DARs) that Part 43 Appendix A (the list of Major Mods) lists everything which the FAA lawyers wanted to be a MM, and if they wanted you to read in between the lines they would have put it in there. But since many installers want to cover their six o'clock, they submit a 337 for everything; this puts the "do I need a DER?" ball in the FAA's court, but (according to statements from FAA inspectors at various seminars) inundates the FAA with huge numbers of silly 337s. And, back to that battery issue, one aircraft owner has it in writing from an FSDO that a similar-size similar-capacity battery is not a MM (the words in App A are "a basic change to the electrical system") and is thus within the A&P's discretion, and definitely within an IA's discretion to just install. A 337 is for a MM only.

The Q then arises as to why do Concord etc bother to obtain STCs. The answer I got was that they do it for marketing reasons; a lot of installers won't read 43 App A and if they do they don't want to interpret it.

I am confused, but I know this debate has been done to death in so many places...

I believe that a recent change in the regs specifically allows the substitution of a dimensionally similar battery of the same or greater capacity from a different manufacturer than the TCDS calls for on older aircraft. I suspect that the reason behind the need for a STC is the fact that the original battery is usually called out on the TCDS and it's generally accepted that anything that deviates from the TCDS requires a STC.