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khorton01(at)rogers.com
Guest

Posted: Sat Aug 12, 2006 4:05 pm Post subject: encoder approval

On 12 Aug 2006, at 18:27, <bakerocb(at)cox.net> <bakerocb(at)cox.net> wrote:



 	  Quote: 	
		   



 Responding to an AeroElectric-List message previously posted by  

 Kevin Horton



 2) You wrote: " How can you be assured that a non-TSO'd encoder  

 will operate correctly at

 temperature extremes, or when subjected to vibration, humidity,

 voltage variations, electromagnetic interference, etc?



 I would base my confidence in a proven non TSO'd altitude encoder  

 on two things:



 A) The superior newer technology used in manufacturing the encoder.



 B) The actual past performance of that encoder over years of use in  

 the field.



 3) You wrote: "If the manufacturer hasn't tested his encoder under  

 the full range of

 conditions, then he has no idea how well it will work there."



 I worked for years in the airborne weapons testing field and I  

 assure you that there is no such thing as ground or laboratory  

 testing "under the full range of conditions". Actual satisfactory  

 performance in the field after a significant period time in use is  

 the best indication of the suitability of a piece of equipment for  

 its intended use.


	


So, once an encoder had a significant period of satisfactory in- 

service use, it would be legal to use that encoder in service.  This  

might work for currently existing encoders, if we accept that there  

is a reasonable probability that an in-service problem would be  

detected.  But how would this approach help for a new encoder?

 	  Quote: 	
		  

 4) You wrote: "If he has done the testing, and it does operate  

 properly over the full

 range of conditions, why would the manufacturer not want to get a  

 TSO  for it?



 Two words -- time and money. When a small business sets out to  

 create, manufacture, and sell a better mouse trap that it has  

 developed it can only operate for so long on the capital available  

 before some income has to arrive in order to sustain the business.  

 If that capital is totally dissipated in un needed tests and  

 bureaucratic paper generation before sufficient income arrives the  

 company dies and the better mouse trap with it.


	


Surely the manufacturer must do a reasonable amount of testing before  

they determine that the encoder actually works correctly.  I wonder  

why they can't document that testing and use it as part of a TSO  

submission.  Maybe the answer is to improve the TSO process.  Review  

the TSO, pull out any unneeded tests, reduce the bureaucratic  

paperwork, and streamline the review process.  As it is, my  

recollection is that the FAA has 30 days from the time a TSO package  

is submitted to accept it.  That isn't bad (if my memory hasn't  

failed me).



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

N6030X(at)DaveMorris.com
Guest

Posted: Sat Aug 12, 2006 5:14 pm Post subject: encoder approval

It also has an RS-232 output that you can feed 

into a laptop if you want to record it, graph it, 

or use it to create your own flight instrument 

displays.  Combine it with a $100 GPS from 

Wal-Mart, and you can do this: http://www.myglasscockpit.com/FMSSample1.jpg

Dave Morris

At 07:02 PM 8/12/2006, you wrote:

 	  Quote: 	

On Aug 12, 2006, at 6:22 PM, Charlie Kuss wrote:

>Brian,

>  The RMI uEncoder is a great addition for the need stated above. I

>gives you redundancy for all 3 primary instruments as well as an

>encoder which is tied to the altimeter function. It only takes up

>one 3.125" hole in the panel. It's also handy for simplifying your

>scan during "partial panel" practice.

It looks like a good instrument. The only problem with a digital

display is that it makes it hard to see trends. With steam gauges or

tapes, I get information from how fast they are moving, something

hard to see with changing numbers.

Regardless, it does give you a lot of information in one hole. I

think that if I had AoA to give me airspeed trends I wouldn't care.

Something like the uEncoder combined with an electric AI and I would

have good backup for a glass PFD.

>Charlie Kuss

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

nuckollsr(at)cox.net
Guest

Posted: Sat Aug 12, 2006 5:55 pm Post subject: encoder approval

At 06:27 PM 8/12/2006 -0400, you wrote:



 	  Quote: 	
		  



8/12/2006



Responding to an AeroElectric-List message previously posted by Kevin Horton



Hello Again Kevin, Continuing our dialogue on our current favorite subject:



1) You wrote: "Do you agree that there are important safety-related reasons to

require that the altitude encoder report the correct altitude, over

the full range of conditions under which it will operate?



Yes.



2) You wrote: " How can you be assured that a non-TSO'd encoder will 

operate correctly at

temperature extremes, or when subjected to vibration, humidity,

voltage variations, electromagnetic interference, etc?



I would base my confidence in a proven non TSO'd altitude encoder on two 

things:



A) The superior newer technology used in manufacturing the encoder.



B) The actual past performance of that encoder over years of use in the field.



3) You wrote: "If the manufacturer hasn't tested his encoder under the 

full range of

conditions, then he has no idea how well it will work there."



I worked for years in the airborne weapons testing field and I assure you 

that there is no such thing as ground or laboratory testing "under the 

full range of conditions". Actual satisfactory performance in the field 

after a significant period time in use is the best indication of the 

suitability of a piece of equipment for its intended use.



4) You wrote: "If he has done the testing, and it does operate properly 

over the full

range of conditions, why would the manufacturer not want to get a TSO  for it?



Two words -- time and money. When a small business sets out to create, 

manufacture, and sell a better mouse trap that it has developed it can 

only operate for so long on the capital available before some income has 

to arrive in order to sustain the business. If that capital is totally 

dissipated in un needed tests and bureaucratic paper generation before 

sufficient income arrives the company dies and the better mouse trap with it.



5) You wrote: "The fact that air traffic control has not detected a 

problem with

someone's encoder says very little."



You are right. But we are not talking about just someone's encoder. We are 

talking about hundreds of encoders that have been performing 

satisfactorily in flight for years and have satisfactorily passed the FAR 

Part 43 Appendices E and F tests many times every two years.



6) You wrote: "If there is a problem, it might not show up until another 

aircraft, responding to a TCAS alert tries to avoid your aircraft, yet 

hits it because the encode was in error.

Is this acceptable?"



No. But I say again, the technology used and the performance of the proven 

non TSO'd encoders is superior to that called for in the TSO. No piece of 

equipment can guarantee perfect peformance throughout its entire service 

life, but the better technology encoder is less likely to have a problem 

show up.



7) You wrote: "If you could write your own wording for 91.217, how would 

you word it

to make it cheaper to comply, yet still achieve the safely objective?"



My preferred first step in the process to resolve the present situation is 

an interpretation from FAA headquarters that automatic pressure altitude 

reporting equipment that is installed in amateur built experimental 

aircraft and tested in accordance with the appropriate provisions of FAR 

91.411, 91.413, and appropriate Appendices to FAR Part 43 are considered 

to be in compliance with FAR 91.217 (b).



I'll let the experts and lawyers work on a permanent rational solution.


	


    I've been watching this thread for several days. Permit me

    to offer some observations:



    A large portion of my career has been used in efforts to track

    down, identify and resolve system malfunctions in broad range

    of aircraft. ALL of the mis-behaving systems were tested, blessed,

    beat, bashed, certified, etc., etc. Most had LONG histories of

    reasonably satisfactory service. Nonetheless, none of the above prevented

    expensive failures in these systems. If gizmos in airplanes

    didn't break, FBOs would go out of business.



    Irrespective of an encoder's pedigree, the ultimate system reliability

    is achieved not by filling out one's pre-installation dance-card.

    Due diligence the third, forth, and fifth questions

    in a Failure Mode Effects Analysis (FMEA) as described in . . .



http://www.aeroelectric.com/articles//FMEA.pdf



    . . . is a more useful activity.



    In the case of encoders, the person at the ATC 'scope

    could not care less whether your encoder is a 30 year old

    electro-mechanical marvel/nightmare or last year's latest

    and greatest, all solid state design. He/she doesn't care

    if it's TSO'd and fabricated from space-grade parts

    or whether you built the thing on your workbench from

    recycled TV set parts.



    What he expects is for you to report level when arriving at

    various assigned altitudes and/or reporting present altitude

    on initial contact.  As you speak the words, he checks for

    reasonably accurate representation of your words

    displayed on his screen. This operating procedure is a

    due diligence to question 3.



    Periodic ramp checks are important for both checking

    agreement between separate encoder/altimeter combinations

    -AND- finding leaks in the system that might cause

    significant errors in BOTH systems. While not a pre-flight

    test, your hand-off from tower to departure control is

    an early-on test of encoder function when you report present

    indicated altitude. This has been a reasonable due diligence

    to question 4.



    Going to question 5 . . . let's consider the probability

    of failure while en route combined with the gross numbers

    of hours you spend in congested airspace. Here again,

    no amount of bureaucratic hat-dancing will guarantee that

    the encoder installed on your aircraft will be forever

    orderly.



    If you perceive a value in reducing risk of en route

    failures going un-noticed, then it's up to you and not your

    friendly flying-fuzz to mitigate your concerns. If you're

    not adverse to having every manner of useful accessory

    installed in your airplane, you might consider something

    like this:



http://www.airsport-corp.com/



    A friend of mine designed these electro-whizzies and

    made a living from their manufacture and sale for a number

    of years. This is a line of totally independent monitors

    of transponder output that offers not only a real-time test

    of PRESENT encoder and transponder behavior, additional

    features provide pilots with potentially useful aids to

    navigation an aviation.



    One may argue the FARs 'til the cows come home but I think

    everyone will agree that the ultimate goal is to achieve

    the lowest practical level of risk for having a bad day

    due to encoder malfunction. We're told that the spirit

    and intent of the FARs is to insure this golden condition.



    I'll simply suggest as both pilot and system designer that

    your lowest practical level of risk will be more closely

    achieved by YOUR knowledge and understanding. Then combine

    understanding with a reasonable implementation of operating,

    monitoring and maintenance of the altitude reporting system.

    This philosophy goes directly to risk mitigation and is

    TOTALLY independent of who made your encoder, who blessed it

    or how well/badly it is made.



    Once you're airplane is signed off, what's the likelihood

    than ANYONE will ask or care what the pedigree of your

    encoder is as long as it accurately performs the regulatory

    hat-dances? Once your airplane is signed of, what are YOU

    going to do to achieve YOUR goals for system reliability?



    I'll suggest that an answer to the later question has a

    greater influence on your future flying comfort than answers

    to the first.



    Bob . . .

cfi(at)conwaycorp.net
Guest

Posted: Sun Aug 13, 2006 8:30 am Post subject: encoder approval

In regard to our concerns about encoder approvals, let’s not be hasty about

accusing the EAA of burying their head in the sand on this important, but not

necessary urgent issue.  We must remember that the EAA does not have unlimited

resources, therefore, they (like everyone else) must chose their battles

carefully.  To put this issue in the spotlight would be very BAD TIMING in

light of the user fee threat that has been looming for at 10 years now.  This

would give the Airline Pilots Association and other opponents to the AOPA/EAA

ammunition to show that we are not capable of following the rules as published

and therefore create a hazard to transportation safety (at least in their eyes)

and should be subjected to the fees to minimize the hazards.  I believe the EAA

is correct by standing by 91.217(b) since it is the current rule.   It would be

foolish and counter-productive for the EAA to publicly support breaking any FAR.

  Excuse the pun, but I believe the encoder issue is “under the radar” so to

speak since our ATC friends are not complaining about it.  I’m also not aware

of anybody who has had enforcement action taken against them for using a non

TSO’d encoder.     If you have, please let us hear about the facts of the

case.



Michael H.



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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 9:26 am Post subject: encoder approval

[rant-mode]



The thing that I don't understand is why this is such a problem. Just  

who do you think is going to crawl under your panel to check to see  

if your encoder is TSO'd?



Pick the encoder you want, wire it to your transponder, finish the  

panel, and present to finished product (airplane) to the radio shop  

for a transponder check (encoder/altimeter correspondence test) or  

for an IFR certification check (correspondence and pitot-static leak- 

down test). They run the test and if it meets spec, they sign your  

airframe logbook. They aren't going to check to see if your encoder  

is TSO'd. They aren't responsible for the airworthiness of your  

airplane. You are. You just need them to certify that the encoder and  

altimeter read the same thing at the same altitude.



If there is a problem then drag your airplane away, fix it, and bring  

it back. Alternatively, fix it right there *yourself*. Don't ask your  

avionics tech, A&P, or IA for their opinion or their blessing. If ATC  

squawks your transponder, fix it, get it checked, send the FAA the  

paperwork, and go about your business. If your transponder really  

breaks, pull it out of the panel, carry it into the radio shop, have  

it fixed, and put it back in your panel. Your repairman's certificate  

means you get to do that.



You learned how to pound rivets didn't you? You learned to construct  

your control systems, didn't you? You learned to lay up fiberglass,  

weld tubing, or rib-stitch fabric, didn't you? You learned to wire an  

electrical system, didn't you? Well then learn to run #22AWG wire to  

D-sub pins, solder, and heat-shrink. Yes, you can build your avionics  

wiring too.



OBAM means "owner *built* and *MAINTAINED*". Maintain your avionics.  

If there is a problem, FIX IT. That is one of the reasons why you  

built your airplane -- so you could save on the cost of maintenance  

too. If you really want to sweat all the certification crap then GO  

BUY A TYPE-CERTIFIED AIRCRAFT.



[/rant-mode]



Brian Lloyd                         361 Catterline Way

brianl at lloyd dot com             Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



"Five percent of the people think.

  Ten percent of the people think they think.

  Eighty-five percent of the people would rather die than think."

        ---Thomas A. Edison

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

Bill Denton

Joined: 10 Jan 2006
Posts: 97
Location: Chicago, IL USA

Posted: Sun Aug 13, 2006 10:00 am Post subject: encoder approval

I think things may have wandered away from the original issue here...



I believe we started out discussing the situation where non-TSO'd EFIS units

were being used to provide encoded altitude output, and that some radio

shops are reluctant to sign off on these types of installations.



And from what I have read, with the increasing use of the GRT, Blue

Mountain, and Dynon EFIS units, this is increasingly becoming a problem...



--

jschroeder(at)perigee.net
Guest

Posted: Sun Aug 13, 2006 11:10 am Post subject: encoder approval

Bryan -



Thoroughly enjoyable rant and it was the best advice on this subject yet.  

One small nit, and I hesitate to argue. The FAA inspector who gave us our  

airworthiness certificate last month said that the only thing the  

repairman's certificate allows one to do is sign off the annual condition  

inspection. My build partner, Ron, will have this. He looked at me and  

said that Ron and I could do anything else to the airplane we so desired.  

He did caution however that some additions and subtractions to a certified  

engine may put the engine into the experimental category. No problems  

there, until we decide to sell. The engine would be experimental and that  

may not make it easy to sell.



Cheers,



John

Lancair ES - ready for first flight

On Sun, 13 Aug 2006 13:23:20 -0400, Brian Lloyd <brian-yak(at)lloyd.com>  

wrote:



 	  Quote: 	
		   Your repairman's certificate means you get to do that.


	


--

jschroeder(at)perigee.net
Guest

Posted: Sun Aug 13, 2006 11:44 am Post subject: encoder approval

Hello Bill,



One data point:



When the tech showed up for the IFR/Altimeter/Encoder/Transponder  

certification, he was surprised when he saw the panel and seemed reluctant  

to go forward. We have to have this check before the first flight because  

we live under the veil of a Class B.



We showed him the pitot tube (looks like any other), the main & aux static  

ports (they look like any other) and showed him the BMA EFIS screen and  

the Dynon screen. He was happy when he could see the altitudes and  

airspeeds. Both altimeters were within tolerance, there were no static or  

pitot leaks and the pressure altitude readout on the transponder was right  

on.



He even did the airspeed cal for us so we could develop our own AD table.  

WE showed him what that meant and how it is done so it meant no additional  

work for him. We also told him, that were it necessary, we could do the  

same to get an accurate altimeter on the BMA. Incidentally, both airspeed  

indications were within a knot or two of each other.



My feeling is that if an OBAMer takes the time to explain how their system  

works, and the tests show that it works, it will alleviate a lot of the  

angst.



Cheers,



John

 	  Quote: 	
		   I believe we started out discussing the situation where non-TSO'd EFIS  

 units

 were being used to provide encoded altitude output, and that some radio

 shops are reluctant to sign off on these types of installations.



 And from what I have read, with the increasing use of the GRT, Blue

 Mountain, and Dynon EFIS units, this is increasingly becoming a  

 problem...

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 11:52 am Post subject: encoder approval

On Aug 13, 2006, at 1:56 PM, Bill Denton wrote:



 	  Quote: 	
		   

 <bdenton(at)bdenton.com>



 I think things may have wandered away from the original issue here...


	


Actually, I think I have hit the real nail on the head.



 	  Quote: 	
		  

 I believe we started out discussing the situation where non-TSO'd  

 EFIS units

 were being used to provide encoded altitude output, and that some  

 radio

 shops are reluctant to sign off on these types of installations.


	


I understand that was what people were talking about.

 	  Quote: 	
		  

 And from what I have read, with the increasing use of the GRT, Blue

 Mountain, and Dynon EFIS units, this is increasingly becoming a  

 problem...


	


That is just it and it is just what I said. The non-TSO'd EFIS units  

are just fine. Wire it to your transponder and be happy. Don't worry  

about the radio shop.



The only REAL issue with using your EFIS to provide both your display  

altitude and your encoded altitude is that a single pressure sensor  

is providing both. This is a single-point-of-failure. Use a separate  

pressure sensor somewhere so you have two sources.



Along that line someone talked about the Rocky Mountain uEncoder and  

then there was a discussion of whether you could use that as it  

wasn't TSO'd. Don't worry. Use it. The key point is now you have  

separate pressure sensors, one in your EFIS and one in the uEncoder.  

The interesting thing is whether they give the same information when  

being tested, i.e. for your IFR cert or xpdr correspondence test, and  

in flight.



But you can use any encoder you want to. It doesn't have to be TSO'd.  

You are responsible for the airworthiness of your aircraft. Satisfy  

yourself.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

rdunhamtn(at)hotmail.com
Guest

Posted: Sun Aug 13, 2006 1:06 pm Post subject: encoder approval

So........



I've wired my Becker TXPDR with altitude encoding from my Dynon EFIS in my 

VFR only Sonex.



Am I legal??? Must I have to have an avionics shop "sign off" on it??? 

WHAT!!!!!!!!



Rodney in Tennessee



Do not archive



[quote]From: "Bill Denton" <bdenton(at)bdenton.com>

Reply-To: aeroelectric-list(at)matronics.com

To: <aeroelectric-list(at)matronics.com>

Subject: RE: Re: encoder approval

Date: Sun, 13 Aug 2006 12:56:47 -0500




<bdenton(at)bdenton.com>



I think things may have wandered away from the original issue here...



I believe we started out discussing the situation where non-TSO'd EFIS 

units

were being used to provide encoded altitude output, and that some radio

shops are reluctant to sign off on these types of installations.



And from what I have read, with the increasing use of the GRT, Blue

Mountain, and Dynon EFIS units, this is increasingly becoming a problem...



--

Bill Denton

Joined: 10 Jan 2006
Posts: 97
Location: Chicago, IL USA

Posted: Sun Aug 13, 2006 1:11 pm Post subject: encoder approval

"Wire it to your transponder and be happy. Don't worry about the radio

shop."



Since the altimeter/encoder/transponder combination have to be inspected and

checked by the radio shop, how could one do this?



--

Bill Denton

Joined: 10 Jan 2006
Posts: 97
Location: Chicago, IL USA

Posted: Sun Aug 13, 2006 1:39 pm Post subject: encoder approval

 	  Quote: 	
		  From the FAR's, as noted:


	


----------------------------------------------------------------------------

--------



§ 91.413   ATC transponder tests and inspections.

(a) No persons may use an ATC transponder that is specified in 91.215(a),

121.345(c), or §135.143(c) of this chapter unless, within the preceding 24

calendar months, the ATC transponder has been tested and inspected and found

to comply with appendix F of part 43 of this chapter; and



----------------------------------------------------------------------------

--------



§ 91.215   ATC transponder and altitude reporting equipment and use.

(a) All airspace: U.S.-registered civil aircraft. For operations not

conducted under part 121 or 135 of this chapter, 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).



----------------------------------------------------------------------------

--------



As I, and many others, read this and the other portions Part 91, it says:



1. In some places, you are required to have a transponder, but in many

others you are not REQUIRED to have one.



2. VFR or IFR is immaterial for the purposes of this particular discussion.



3. If you have a transponder, whether required or not required, it must be

tested and inspected every 24 months.



In short, if you are going to use a transponder in the US Airspace system,

it must MEET TSO SPECIFICATIONS, and it must be inspected every 24 months.



Like it or not, it makes sense...



--

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 2:00 pm Post subject: encoder approval

On Aug 13, 2006, at 5:03 PM, Rodney Dunham wrote:



 	  Quote: 	
		   

 <rdunhamtn(at)hotmail.com>



 So........



 I've wired my Becker TXPDR with altitude encoding from my Dynon  

 EFIS in my VFR only Sonex.



 Am I legal???


	


Yes.



 	  Quote: 	
		   Must I have to have an avionics shop "sign off" on it??? WHAT!!!!!!!!


	


Yes. You must have the shop perform a transponder correspondence  

check where they verify that the transponder and encoder report the  

same altitude as your altimeter over the normal operating range of  

your altimeter. This is not an inspection of your installation or of  

what equipment you have chosen to use, but is just a check to make  

sure it is reporting what it is supposed to report. Every airplane  

with a transponder must pass this check.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 2:26 pm Post subject: encoder approval

On Aug 13, 2006, at 5:36 PM, Bill Denton wrote:



 	  Quote: 	
		   

 <bdenton(at)bdenton.com>



> From the FAR's, as noted:



 ---------------------------------------------------------------------- 

 ------

 --------



 § 91.413   ATC transponder tests and inspections.

 (a) No persons may use an ATC transponder that is specified in  

 91.215(a),

 121.345(c), or §135.143(c) of this chapter unless, within the  

 preceding 24

 calendar months, the ATC transponder has been tested and inspected  

 and found

 to comply with appendix F of part 43 of this chapter; and



 ---------------------------------------------------------------------- 

 ------

 --------



 § 91.215   ATC transponder and altitude reporting equipment and use.

 (a) All airspace: U.S.-registered civil aircraft. For operations not

 conducted under part 121 or 135 of this chapter, 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).



 ---------------------------------------------------------------------- 

 ------

 --------



 As I, and many others, read this and the other portions Part 91, it  

 says:



 1. In some places, you are required to have a transponder, but in many

 others you are not REQUIRED to have one.



 2. VFR or IFR is immaterial for the purposes of this particular  

 discussion.



 3. If you have a transponder, whether required or not required, it  

 must be

 tested and inspected every 24 months.



 In short, if you are going to use a transponder in the US Airspace  

 system,

 it must MEET TSO SPECIFICATIONS, and it must be inspected every 24  

 months.



 Like it or not, it makes sense...


	


And all of this applies to the TRANSPONDER, not to the altitude  

encoder feeding altitude information into the transponder. Since you  

are buying a transponder that already meets these specs you are home  

free. Yes you must have the transponder certified every 24 months but  

that is an operational check, not a verification of anything you have  

installed.



You guys are trying to make this just WAY too hard.



Here it is, one more time:



1. Buy the transponder you like best. Transponders from reputable  

manufacturers of avionics all qualify. (I have had good experience  

with King, Narco, and Apollo. I have had bad experience with Terra  

and Garmin. YMMV.)



2. Connect it to the encoder you like best, be it your EFIS, a Rocky  

Mountain uEncoder, a standard production encoder, etc. It does not  

matter what kind of encoder it is so long as it does what it is  

supposed to do.



3. Install all this stuff in your airplane using standard practices  

and good workmanship. (But you are already doing that anyway because  

you know that the butt you save may be your own.)



4. When you are ready to fly your airplane, find someone who can do  

the transponder certification check for you. It will probably be your  

local radio shop but there may be others. They will do the  

*operational* check and make an entry in your airframe logbook.



5. Go fly and have a good time.



6. Go to step 4 in 24 months.



NOTE: at no time in the above five steps do you see the words "get  

approval".



Brian Lloyd                         361 Catterline Way

brianl at lloyd dot com             Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



"Five percent of the people think.

  Ten percent of the people think they think.

  Eighty-five percent of the people would rather die than think."

        ---Thomas A. Edison

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 2:30 pm Post subject: encoder approval

On Aug 13, 2006, at 5:06 PM, Bill Denton wrote:



 	  Quote: 	
		   

 <bdenton(at)bdenton.com>



 "Wire it to your transponder and be happy. Don't worry about the radio

 shop."



 Since the altimeter/encoder/transponder combination have to be  

 inspected and

 checked by the radio shop, how could one do this?


	


Just what I said. Your installation does not need any kind of FAA  

approval, IA approval, A&P approval, or radio shop approval. The only  

thing you need to get is a transponder check to verify that the  

transponder is working, on frequency, and that its mode-C reports the  

same altitude as your altimeter. It is not a check of what kind of  

encoder you have or of how you installed it. It is just an  

operational check. Of course, you want to do that anyway because  

*YOU* want to make sure it is working properly. The radio shop has  

the tools to interrogate your transponder on the ground and you  

essentially want to borrow that.



The radio shop just needs to connect to the static port and place an  

antenna from the test box near your transponder antenna. They will  

then vary the pressure on your static port. Your altimeter should  

show the same altitude that their altimeter shows. Your transponder  

should also report the same altitude in its mode-C. That is all there  

is to it. If it passes this functional test, you get a logbook entry  

and you are good to go.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

N1DeltaWhiskey(at)comcast
Guest

Posted: Sun Aug 13, 2006 2:38 pm Post subject: encoder approval

Brian,



A quick question (I hope) - if the transponder displays what altitude it is 

transmitting to ATC, is it still necessary to have the shop do the 

calibration?  Would seem to me that one would only need to compare one's own 

altimeter to the transmitted information.  I am speaking of experimental AC, 

not certified.



Doug Windhorn



---

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Aug 13, 2006 3:06 pm Post subject: encoder approval

On Aug 13, 2006, at 6:33 PM, Doug Windhorn wrote:



 	  Quote: 	
		   

 <N1DeltaWhiskey(at)comcast.net>



 Brian,



 A quick question (I hope) - if the transponder displays what  

 altitude it is transmitting to ATC, is it still necessary to have  

 the shop do the calibration?


	


Yes. The correspondence check is requires by the FARs.



 	  Quote: 	
		   Would seem to me that one would only need to compare one's own  

 altimeter to the transmitted information.  I am speaking of  

 experimental AC, not certified.


	


That is a good idea to do on a regular basis but it is not enough.  

You must get a transponder certification check every 24 months.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

khorton01(at)rogers.com
Guest

Posted: Sun Aug 13, 2006 5:26 pm Post subject: encoder approval

On 13-Aug-06, at 6:33 PM, Doug Windhorn wrote:



 	  Quote: 	
		   

 <N1DeltaWhiskey(at)comcast.net>



 Brian,



 A quick question (I hope) - if the transponder displays what  

 altitude it is transmitting to ATC, is it still necessary to have  

 the shop do the calibration?  Would seem to me that one would only  

 need to compare one's own altimeter to the transmitted  

 information.  I am speaking of experimental AC, not certified.


	


Ignoring the FAR requirements for a moment - if you haven't had the  

system checked, how do you know the altimeter is showing the correct  

altitude?



Kevin Horton

RV-8 (Finishing Kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

N1DeltaWhiskey(at)comcast
Guest

Posted: Mon Aug 14, 2006 6:31 am Post subject: encoder approval

Kevin,



Thought of that after Brian's reply and reading the FAR 43 App F.



Although, as a "Repairman", AND if one had the proper equipment and knew how 

to use it, I presume one could sign off a test on their own airplane.



Doug



---

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon Aug 14, 2006 12:23 pm Post subject: encoder approval

On Aug 14, 2006, at 3:19 PM, <bakerocb(at)cox.net> wrote:



 	  Quote: 	
		   



 8/14/2006



 Responding to an AeroElectric-List message previously posted by  

 Brian Lloyd



 Hello Brian, Thanks for your input.



 You wrote in part: "But you can use any encoder you want to. It  

 doesn't have to be TSO'd.

 You are responsible for the airworthiness of your aircraft. Satisfy  

 yourself."



 I am in concurrence with the thrust of your statements, but FAR  

 91.217 is relevant. If your encoder / transponder is not TSO'd as  

 called for in 91.217 (c) then the installation must pass the tests  

 required by FAR 91.217 (b).


	


ARRGGGH! You are making me want to tear my hair out.



OK, I am going to say this just one more time as you are insisting on  

muddying the waters, pissing on the wedding cake, as it were.



YOU MAY USE ANY ENCODER YOU WANT TO USE. WIRE IT UP TO YOUR  

TRANSPONDER. DRAG YOUR AIRPLANE OVER TO GET A TRANSPONDER  

CERTIFICATION AND THEN GO FLY.



Why do I say this? Because of FAR 91.217(b) which reads:



(b) Unless, as installed, that equipment was tested and calibrated to  

transmit altitude data corresponding within 125 feet (on a 95 percent  

probability basis) of the indicated or calibrated datum of the  

altimeter normally used to maintain flight altitude, with that  

altimeter referenced to

29.92 inches of mercury for altitudes from sea level to the maximum  

operating altitude of the aircraft;



Hello! This is the transponder certification test! This is the test  

performed by the radio shop on your airplane! They feed absolute  

pressure into your static system and check the transponder altitude  

(mode-C) output at several pressure altitudes. The mode-C output of  

your transponder must track your altimeter to within 125' of what is  

indicated on your altimeter.



The key point is that you have TESTED your installation to ensure it  

is working.



 	  Quote: 	
		   Unfortunately at the present time (until corrected) FAA HQ has  

 described a testing process for compliance with FAR 91.217 (b) that  

 is unreasonable. See their response to my letter in a previous  

 posting.


	


This is what happens when people ask questions of the FAA. You get  

some boob who hasn't got a clue to interpret things for you. The key  

point is that FAR 91.217(b) is very clear and needs no interpretation.



The transponder certification test is where you test and calibrate  

your encoder to transmit altitude data corresponding within 125' of  

the indicated or calibrated data of the altimeter normally used to  

maintain flight attitude, with that altimeter referenced to 29.92"Hg  

for altitudes from sea level to the maximum operating altitude of the  

aircraft.



Notice just how similar my words are to 91.217(b)?



Now, if you don't cease and desist trying to confuse this issue, I am  

going to come over there and beat your hands into a bloody pulp with  

a hard-bound copy of the FARs so you can't type any more. 



(BTW, if you use the same pressure sensor to generate your altitude  

readout AND drive your transponder, the altitude sent by the  

transponder absolutely MUST be the same indicated since they are both  

the same data.)

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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