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Old May 21st 18, 01:19 AM posted to rec.aviation.soaring
Darryl Ramm
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Default Glide computer in certified glider

On Sunday, May 20, 2018 at 9:06:11 AM UTC-7, 2G wrote:
On Saturday, May 19, 2018 at 9:52:05 AM UTC-7, jfitch wrote:
On Saturday, May 19, 2018 at 8:51:12 AM UTC-7, 2G wrote:
On Saturday, May 19, 2018 at 7:23:32 AM UTC-7, jfitch wrote:
On Saturday, May 12, 2018 at 3:10:57 PM UTC-7, 2G wrote:
On Thursday, May 10, 2018 at 11:35:08 PM UTC-7, Bob Kuykendall wrote:
On Thursday, May 10, 2018 at 7:48:12 PM UTC-7, 2G wrote:
So, you think I am full of ****...

I wouldn't have put it in so few words.

If you do call the FAA for guidance, they will likely refer you Advisory Circular AC 43-210A (https://www.faa.gov/documentLibrary/...AC_43-210A.pdf) “Standardized Procedures for Obtaining Approval of Data Used in the Performance of Major Repairs and Major Alterations.” This covers what constitutes a minor repair:

“3.2.2 Determine the Repair or Alteration Classification. Determine if the repair/alteration is a minor change in type design (as defined in 14 CFR part 21, § 21.93) to the product’s type design; and if so, is it a major or a minor repair/alteration. To determine if a repair/alteration is major or minor, refer to part 43 appendix A. Figure 3-2, Determination of Major or Minor Alteration or Repair, is a flowchart of the field approval evaluation process based on part 43 appendix A.”

The regulation referenced, 14 CFR part 21, § 21.93, explicitly defines what constitutes a minor repair (https://www.law.cornell.edu/cfr/text/14/21.93):

"(a) In addition to changes in type design specified in paragraph (b) of this section, changes in type design are classified as minor and major. A “minor change” is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. All other changes are “major changes” (except as provided in paragraph (b) of this section)."

The addition of instrument not required for certification constitutes a minor alteration (unless it affects the performance of required instrumentation) and meets the above criteria. An FAA airframe inspector are available to answer any questions concerning these regulations. My experience with FAA inspectors is they are really trying to make compliance as easy as possible and are not trying to make your life miserable.

Tom

That definition of minor change leaves very wide latitude for minor changes. Also great latitude for judgement about what is considered a minor change.

I totally disagree. 14 CFR 21.93 clearly states:

A “minor change” is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product.

If ANY of these conditions are met, it is a major change requiring the attendant paperwork. You don't make this judgment, your A&P does. And I would consult with an IA who is authorized to sign off on major changes.

Tom


There is very little you can do to the panel that would affect any of those things. As long as the required instruments stayed in place, you could replace the entire panel with a homebuilt one made from crumb board from Home Depot, complete with a lawn sprinkler controller and a hair dryer. Weight, balance, structural strength, reliability, operational or other characteristics? No appreciable affect, hence minor change. Yeah the A&P would need to sign. He's the one with the great latitude for judgement.


Now you are being silly. Adding ADS-B Out to a standard category aircraft, for example, IS NOT a "minor" change, requiring an STC.

Tom



No, this is not correct and is misinformation that can create problems for other glider owners.

Show us one regulation or FAA policy that states an ADS-B Out install is necessarily a major modification....

ADS-B Out installs can "require an STC?" yes, in a very specific way, as one (the most common) way to justify the pairing of a specific ADS-B transmitter and GPS Source. That use of an STC is special and does *not* automatically make the install a major alteration, but that seems to be confusing Tom here.

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So people do not cause themselves problems by believing this wrong information here is more explanation: (or just remember this is here and point your A&P at it if needed).

Wether an ADS-B Out install is a major or minor modification in a certified aircraft has the same tests applied to it as any other modification. That's because there is *no* FAA regulation or policy saying an ADS-B Out install is a major modification, so the normal rules apply.

Once upon a time an ADS-B Out install in a type certified aircraft was more complex, it's simpler now. So be careful about looking at old information.

For the last few years the FAA policy uses an STC as (the most common) basis for pairing the transponder and GPS source, and requires the installer to follow the relevant STC documentation for pairing those devices. That STC is not necessarily used there as the basis for the approval of a major modification (and since there are no glider-specific STCs for any of these installs, or even a basic transponder install, those STC likely do not cover enough for an install in a glider to do so). The FAA was being very pragmatic here about avoiding problems with pairing different devices and wanted to know that devices paired in actual installs had been proven to work well together and documented in a prior STC.

The key FAA policy document guiding all this is N 8900.362 https://www.faa.gov/regulations_poli...mentID/1029526 (People wanting more technical info can also read AC 20-165B https://www.faa.gov/regulations_poli...entID/1028666). And yes this policy document is past its expiration date, but is still the reference doc being used by FSDOs and others (the expiration date issue has been explained a lot elsewhere, Google for it if curious). Section 6 in that policy describes the requirements for "subsequent installs" using an STC to justify the pairing, and is pretty straightforward.

That policy requires filing an "notification only" (the term commonly used to refer to doing that, but the policy does not use that exact term) 337 with FAA HQ in Oklahoma, not with the FSDO. That does *not* make that installation automatically a major change, and does not anywhere require filing that 337 with the FSDO for major modification approval. If the A&P IA determines the change is a major modification (separate from anything to do with that is is "ADS-B") then they could would file a 337 for approval with the FSDO as normal for a major modification.

Some folks have unfortunately read that the policy and see mention of 337s and are not reading clearly what it says and assume they *have* to file the 337 with the FSDO, the FSDO may see an inbound 337 and assumes the A&P is seeking approval for a major change... and that might start a pile of unnecessary work. Read the policy document carefully and follow it, it's really that simple.

Owners may want to talk to their A&P IA before they do an ADS-B Out install and ask them what paperwork they plan to file/where/why if it's different than what I'm outlining here it may be a good to check they are familiar with that FAA policy N 8900.362.

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Other general things to help A&Ps and glider owners:

There is no paperwork/notice only 337 to file for any ADS-B Out or TABS install in any experimental aircraft.

For 2020 Complaint installs in a type certified glider: you need to use a Trig TT22 transponder and TN70 GPS Source (since its actual TSO-C145c approved). All the glider community Trig dealers know how to get the TT22+TN70 STC paperwork from Peregrine (Trig's STC development partner). Your A&P will want to get that paperwork, even though again its not being used to support a major alteration approval.

Do NOT do a SIL-3/"2020 Compliant" install in a type certified aircraft using a non-TSO-C145c or similar actual TSO approved GPS source. And the FAA could easily spot that something is up as there won't be that notification only 337 filed for your aircraft in their database. The TN72 CAN be used to do TABS SIL=1 in a type certified glider, but not 2020 Compliant ADS-B Out. There is no paperwork to file anywhere for a TABS install. Double check any such install to make sure you are transmitting SIL=1 not SIL-3.

Since the TN72 is a "meets performance requirements..." but not actual TSO-C145c or similar GPS source, you can do a 2020 Compliant SIL-3 install with a TN72 and TT22 in a *experimental* glider (but not a type certificated glider) again, there is no FAA paperwork to file for a TABS install, just a maintenance log book entry.

Pull an FAA ADS-B flight report for all installs, ideally the first few flights, for both 2020 Compliant ADS-B Out or TABS. https://adsbperformance.faa.gov/PAPRRequest.aspx I'm happy to help people look at the reports and make sure they look OK.