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  #1  
Old 03-25-2020, 09:45 AM
SkiMoreBumps SkiMoreBumps is offline
 
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Default TSO’d vs not...

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?
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  #2  
Old 03-25-2020, 10:10 AM
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Mike S Mike S is online now
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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.
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  #3  
Old 03-25-2020, 10:31 AM
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rocketbob rocketbob is offline
 
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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...
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  #4  
Old 03-25-2020, 10:42 AM
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Quote:
Originally Posted by SkiMoreBumps View Post
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!
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Last edited by avrojockey : 03-25-2020 at 11:01 AM.
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  #5  
Old 03-25-2020, 11:04 AM
krw5927 krw5927 is offline
 
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Quote:
Originally Posted by SkiMoreBumps View Post
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.
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  #6  
Old 03-25-2020, 11:10 AM
lr172 lr172 is offline
 
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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.
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Last edited by lr172 : 03-25-2020 at 11:20 AM.
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  #7  
Old 03-25-2020, 11:31 AM
RVDan RVDan is online now
 
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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.
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  #8  
Old 03-25-2020, 11:39 AM
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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.
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  #9  
Old 03-25-2020, 11:52 AM
Jpm757 Jpm757 is online now
 
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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.
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  #10  
Old 03-25-2020, 12:24 PM
Canadian_JOY Canadian_JOY is offline
 
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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!
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