What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

TSO?d vs not...

SkiMoreBumps

I'm New Here
I have a CFI who rails about the dangers of experimental aircraft and their non-TSO?d avionics etc... I pointed out that the FAA is now allowing some of the non-TSO items in part 23 certified aircraft, and he kind of shrugged.

Sooo settle this for us please... what is generally the difference between TSO?d and non TSO?d avionics that otherwise appear identical? The G3X for experimentales vs one that can be installed in part 23 airplanes for several thousand dollars more. What does one get for several more airplane dollars, other than the right to put it in a part 23 airplane?
 
IIRC, the installation for a certified aircraft as you mention is not a matter of TSO, but rather is done under a STC.

Still even with that said, sounds like a case of charging what the market will bear.
 
There is absolutely no regulatory requirement that requires TSO approval for parts installed in certified aircraft. "Meets or Exceeds" is what's in the regs. Its easier for an A&P to prove that the installation or replacement of part "meets or exceeds" if the part has a TSO/STC approval.

Using FAA AC23-27 there are many things I can approve as an A&P to do parts substitution for more modern equivalents.

Ask your CFI to open up the oil door, point to any zip tie he finds, and ask if that zip tie has TSO approval, and ask him if it's legal.

4509 light bulb has no TSO approval. Many airplanes use 4509 bulbs. I could go on...
 
I have a CFI who rails about the dangers of experimental aircraft and their non-TSO’d avionics etc... I pointed out that the FAA is now allowing some of the non-TSO items in part 23 certified aircraft, and he kind of shrugged.

Sooo settle this for us please... what is generally the difference between TSO’d and non TSO’d avionics that otherwise appear identical? The G3X for experimentales vs one that can be installed in part 23 airplanes for several thousand dollars more. What does one get for several more airplane dollars, other than the right to put it in a part 23 airplane?

TSO/PMA/STC != Safety

In fact the argument could be made that the regulatory limits placed by the FAA for years have had a regressive effect on aviation safety. Though, they're making some good changes now. Case in point, my airplane has better avionics than the Boeing I fly at work.

To argue experimental avionics are unsafe says little to knowledge of safety scope. Sure, if you test experimental vs TSO'ed on a bench the TSO'ed version may beat the experimental (probably not), but avionics don't sit on a bench - they're a part a complex aviation organism that involves several variables. The Garmin ecosystem I have has features that increase safety in very significant ways over the Boeing, and the experimental nature of the avionics can be mitigated through panel redundancy if one is worried about that.

I ferried an airplane from Bulgaria once that had a Trimble IFR/TSO'ed GPS. It was a boat anchor! It had a horrible user interface and being cleared direct to a fix was 5 minute exercise. Knowing the regulatory nature of the EU I felt more comfortable navigating off my iPad than that Trimble...the faithful Christian buddy of mine I was still flying with still curses at that thing!
 
Last edited:
I have a CFI who rails about the dangers of experimental aircraft and their non-TSO?d avionics etc... I pointed out that the FAA is now allowing some of the non-TSO items in part 23 certified aircraft, and he kind of shrugged.

Sounds precisely like the kind of CFI that I would not hesitate to quickly part ways with.
 
modern certified avionics are now largely being directly born from the exp market. The G5 is a good example. While I have no details, I doubt there is any meaningful difference between the certified and non versions other than limiting some s/w and features that dont play well with the regs or increase risk. Suspect the G3x is the same. I would be surprised if the vendors are not using real world MTBF data from their exp versions to accelerate certification efforts with the FAA and reduce testing time.

ask your cfi for a comparison of mishaps due to a failing TSO'ed attitude indicator compared to a failing Exp EFIS. Generalities based upon assumptions and folklore don't help anyone. Suggest you seek advice from more knowledgeable and forward thinking sources.
 
Last edited:
For the most part, TSO approval of equipment means that the manufacturer has demonstrated that it meets the performance standards of the TSO and that the product is produced under an FAA approved manufacturing and quality system.

Experimental avionics may meet the TSO performance requirements but not receive TSO because the manufacturer does?t want the burden of the FAA manufacturing and quality system requirements or FAA oversight.

As a person who does STC?s for a living, having TSO equipment saves us the costs of qualifying the equipment for each STC. Even if we wanted to, demonstrating the performance requirements for certain TSO?s, like say a transponder would be difficult to do unless you are the equipment manufacturer.

Environmental testing is essential. As I tell my clients, I have not yet witnessed a complete set of environmental testing from an equipment manufacturer that has passed all tests the first time.

Companies like Dynon and Garmin who have the experience generally verify internally to their companies that their equipment meets the expected performance, including environmental standards and save the cost of TSOA.

Then there is the software issue. The necessary development processes required for TSO can be very expensive. Critical systems like PFD displays have to go through exhaustive testing in a way that ensures all code is exercised. I am certain, the Experimental avionics manufacturers aren?t as detailed in their SW controls and testing. This is why we see SW releases with sometimes immediate fixes necessary. Almost never happens in TSO equipment for critical functions. The blank screens that we too often hear about on our systems would be fleet grounding events in the certified world.

That said, I have Dynon in my airplane and I am sure I am safer than with a six pack. We all choose our acceptable risks.
 
Many may remember the King KX-170B that was in most if not all single engine Cessnas and Pipers produced in the 60 -70?s, I recall the KX-170B was not TSO?d, maybe your CFI learned to fly behind it if he is in that age group.
 
FWIW, I spoke with a Lycoming rep. a few years ago at SnF, and asked him what the difference was between their certified engines and the "Y" experimental versions. His response "absolutely nothing, they come down the assembly line together, only difference is the data plate".
This may very well be the case with the avionics manufacturers as well, why have 2 different assembly lines for virtually the same product. The difference in price can only be due to liability and FAA compliance.
 
As a person who was involved in getting avionics through the TSO process, I can say that most of the info imparted above is correct, if perhaps only partially so.

Firstly, TSO is about the device... it has nothing to do with the manufacturing process - that's an entirely different certification. TSO is an equipment performance certification, meaning the equipment has been tested against the Minimum Operating Performance Specification (MOPS) defined for that device. The design house documents the testing of the device, then submits those test results to the regulatory authority for approval and issuance of the TSO approval. Approval to manufacture the device comes along after the design approval, be it TSO or any other design approval.

Now what's the difference between experimental and TSO'd avionics? The real answer is we have no clue because most experimental avionics manufacturers provide no documentation to us in which they state they have tested to meet particular levels of performance categorized in DO-160 (environmental) and DO-178 (software).

We know the experimental avionics manufacturer is in the same boat as, for instance, LSA manufacturers, where they have to make a product that meets or exceeds common industry performance benchmarks. If they failed to do so, their products would get a pretty severe black eye in the marketplace, and perhaps in the courtroom.

Smaller manufacturers may not have the resources to conduct meaningful environmental testing, and they surely won't be documenting their software development in accordance with DO-178. Their products inherently carry more risk, but we balance that off against the reward of lower cost and a much more powerful feature list.

As for your instructor, ditch him. He clearly has taken an entrenched position and has steadfastly refused to educate himself. If he's like this with avionics, you can rest assured he is just as likely to be as far behind the times in many other areas, including air regulations, instructional techniques, engine management etc etc. Don't walk away... RUN!
 
This is going to be a fun conversation with a CFI haha. Thanks folks. I can't wait to point out a zip tie and ask him about it haha.
 
This is going to be a fun conversation with a CFI haha. Thanks folks. I can't wait to point out a zip tie and ask him about it haha.

More ammunition for you from an avionics company who makes NON-TSO equipment and installs them in Standard category aircraft all the time :

CAN NON-TSO'D EQUIPMENT BE INSTALLED IN A TYPE-CERTIFICATED AIRCRAFT?

It is widely believed that all avionics equipment that is installed in a type certificated aircraft must have TSO authorization. The purpose of this pamphlet is to examine this idea by references found in FAA documentation. The scope of this discussion will be limited to aircraft with a standard category U.S. airworthiness certificate. To begin lets first take a look at the CFRs.

14 CFR 91 Subpart C? Equipment, Instrument, and Certificate Requirements.

Section 91.205 ?Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements.

(d) Instrument flight rules. For IFR flight, the following instruments and equipment are required:

(2) Two-way radio communication and navigation equipment suitable for the route to be flown.

There are also some general references as to the performance requirements of installed equipment. Please refer to 14 CFR 23 Subpart F Section 23.2505, 23.2510, 23.2520

At this point it would be the responsibility of the installer to verify that the installed equipment meets the requirements of the above part 23 sections. One means to insure this would be to only install TSO?d equipment. TSO?d equipment is equipment that the FAA has examined and determined that it meets the requirements of Part 23. Another way would be to review the requirements set forth for a particular type of equipment (i.e. communication or navigation radio) by referring to a particular TSO document. The TSO document will spell out the minimum performance standard for a type of equipment, usually by referencing an industry-standard organization?s documentation such as that of RTCA Inc. (Radio Technical Commission for Aeronautics). At this point in our discussion one might be overwhelmed by the process and choose the path of least resistance and go with the TSO?d equipment. Or one could look to the manufacturer of the equipment for information as to what standard the equipment was manufactured to. This information is typically found in the specifications section of the equipment?s installation manual. The idea that a piece of equipment meets the requirements of a recognized standard such as a TSO but not have the TSO authorization is backed up in FAA Order 8300.16A APPENDIX A. Definitions (10) Meet Minimum Technical Standard Order (TSO) Established Standards. Means that the equipment need not have TSO approval, but that it meets requirements set by the TSO.​

The next topic that comes up in the discussion is whether or not the installation is required to be recorded on FAA Form 337 and whether it will require a field approval. These questions are answered by examining the requirements for the use of Form 337 and for field approvals. 14 CFR Part 1 Section 1.1 defines a minor alteration as an alteration that is not a major alteration. Some examples of major alteration are defined in Appendix A of Part 43. Unfortunately the installation of radio equipment is not appropriately covered in the appendix.

FAA Order 8300.16A Chapter 3 provides guidance as to determining if an alteration is major or minor. In this discussion it will be broken down into a series of questions the installer might answer to arrive at a designation of the alteration as major or minor.

General alterations:

? Does the proposed alteration have an appreciable effect on the certificated weight? (i.e. A change in the maximum takeoff weight limitations, minimum landing weight limitations, etc.)

? Does the proposed alteration have an appreciable effect on the certificated balance? (i.e. A change in the forward or aft center of gravity limits, etc.)

? Does the proposed alteration have an appreciable effect on the structural strength?

? Does the proposed alteration have an appreciable effect on the performance?

? Does the proposed alteration have an appreciable effect on the powerplant operation?

? Does the proposed alteration have an appreciable effect on the flight characteristics?

? Does the proposed alteration have an appreciable effect on other characteristics affecting the airworthiness?

Yes to any of the above questions: The proposed change is a major change in type design requiring the application for a Supplemental Type Certificate (STC).
Confirmed no to all: Continue.

? Is it possible that the proposed alteration might have an appreciable effect on the certificated weight? (i.e. A change in the maximum takeoff weight limitations, minimum landing weight limitations, etc.)

? Is it possible that the proposed alteration might have an appreciable effect on the certificated balance? (i.e. A change in the forward or aft center of gravity limits, etc.)

? Is it possible that the proposed alteration might have an appreciable effect on the structural strength?

? Is it possible that the proposed alteration might have an appreciable effect on the performance?

? Is it possible that the proposed alteration might have an appreciable effect on the powerplant operation?

? Is it possible that the proposed alteration might have an appreciable effect on the flight characteristics?

? Is it possible that the proposed alteration might have an appreciable effect on other characteristics affecting the airworthiness?

? Does the proposed alteration alter the wings?

? Does the proposed alteration alter the tail surfaces?

? Does the proposed alteration alter the fuselage?

? Does the proposed alteration alter the engine mounts?

? Does the proposed alteration alter the control system?

? Does the proposed alteration alter the landing gear?

? Does the proposed alteration alter the hull or floats?

? Does the proposed alteration alter the elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights?

? Does the proposed alteration alter the hydraulic and electrical actuating system of components?

? Does the proposed alteration alter the rotor blades?

? Does the proposed alteration change the empty weight or empty balance which results in an increase in the maximum certificated weight or center of gravity limits of the aircraft?

? Does the proposed alteration change the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, deicing, or exhaust systems.

? Does the proposed alteration change the wing or any fixed or movable control surfaces which affect flutter and vibration characteristics?

? Does the proposed alteration convert an aircraft engine from one approved model to another, involving any changes in compression ratio, propeller reduction gear, impeller gear ratios or the substitution of major engine parts which requires extensive rework and testing of the engine?

? Does the proposed alteration change the engine by replacing aircraft engine structural parts with parts not supplied by the original manufacturer or parts not specifically approved by the Administrator?

? Does the proposed alteration include the installation of an accessory which is not approved for the engine?

? Does the proposed alteration include the removal of accessories that are listed as required equipment on the aircraft or engine specification?

? Does the proposed alteration include the installation of structural parts other than the type of parts approved for the installation?

? Does the proposed alteration make any conversions of any sort for the purpose of using fuel of a rating or grade other than that listed in the engine specifications?

Yes or maybe to any of the above questions: The proposed change is a major alteration requiring approved data, recording of FAA Form 337 and a log book entry.
Confirmed no to all: Continue.

? Has the Administrator issued an Advisory Circular that requires the use of approved data for this installation/alteration?

Yes: Follow the guidance contained in the Advisory Circular.
No: Continue.

? Has the Administrator issued policy (HBAW, FSAW, etc.) that requires the use of approved data for this installation/alteration?

Yes: Follow the published policy.
No: The alteration is a minor alteration with no additional published guidance therefore the use of acceptable data is authorized and the alteration/installation must be recorded in the appropriate maintenance record. Follow the provisions of Part 43, 65 and/or 145 as appropriate.

Appliance alterations:

? Does the alteration affect the basic design of the appliance?

Yes: Continue.
No: The alteration is considered an appliance minor alteration.

? Is the alteration of the basic design of the appliance made in accordance with recommendations of the appliance manufacturer or in accordance with an FAA Airworthiness Directive?

Yes: Continue.
No: The alteration is considered a major appliance alteration.

? Does the change in the basic design of radio communication and navigation equipment approved under type certification or a Technical Standard Order have an effect on frequency stability, noise level, sensitivity, selectivity, distortion, spurious radiation, AVC characteristics or ability to meet environmental test conditions and other changes that have an effect on the performance of the equipment?

Yes: The alteration is considered a major appliance alteration.
No: The alteration is considered a minor appliance alteration.
 
I have a CFI who rails about the dangers of experimental aircraft and their non-TSO’d avionics etc... I pointed out that the FAA is now allowing some of the non-TSO items in part 23 certified aircraft, and he kind of shrugged.

Sooo settle this for us please... what is generally the difference between TSO’d and non TSO’d avionics that otherwise appear identical? The G3X for experimentales vs one that can be installed in part 23 airplanes for several thousand dollars more. What does one get for several more airplane dollars, other than the right to put it in a part 23 airplane?


You have plenty of proof here but it sounds like your CFI should do his/her research before making a broad statement. When I started flying back in 1997, I clearly remember my CFI telling me how crazy those people were that flew these Experimental RVs. He actually got me believing that these planes were not safe.... I finally met someone in 2010 that opened my eyes and I started learning about what "experimental" really meant and how every airplane ever made is experimental at some point, etc. Shame on me for allowing so many years of wonderful experiences go by because I listened to someone without doing my own research. I just didn't know any better :mad:.

Companies like Garmin aren't going to put out sub-par products just because it's stamped "experimental". Sounds like your CFI has this image in his mind that these are built on some assembly line and if they don't pass some sort of test they get kicked to side and sold as experimental :D.
 
Last edited:
I wonder what your instructor?s opinion is on electronic ignitions and Lean of peak operations? He?s probably not a bad guy. As said earlier, he just hasn?t taken the time to educate himself enough to opine on the subject. Truthfully, his thoughts place him in the majority of instructors. The spread of inaccurate information is pervasive. Those of us who embrace the experimental side of aviation are not, IMO, the majority. Most of the other cfi?s I know, dont fly exp. .02.
 
Back
Top