Today's Message Index:
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1. 05:42 AM - Questions on avionics ()
2. 06:19 AM - only hearing broken transmissions (Ron Patterson)
3. 09:54 AM - Re: only hearing broken transmissions (Noel Loveys)
Message 1
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| Subject: | Questions on avionics |
4/15/2008
Hello Bruce, You wrote:
"1. What does it mean to "cage" an attitude indicator?"
Some attitude indicators have a mechanical means to lock the gyro gimbals so
that the gyro gimbals are held rigidly to the instrument case. This can
serve two functions:
A) It can save wear and tear on the gyro if you are going to do some
aerobatic manuevering and don't want the gyro to be moving around
extensively as it tries to always show the proper aircraft attitude.
B) If the gyro has tumbled and one wants to erect it again to a proper
attitude one can put the airplane in a level attitude, cage and then uncage
the gyro, and it will then start indicating properly a level attitude from
that new starting point.
"3. Is purchasing a separate encoder necessary?.....I see some avionics
vendors packaging
in a separate encoder but don't really understand why."
They are doing this because the altitude encoder in almost all of the EFIS
being sold to the amateur built community are not TSO'd and therefore do not
comply with FAR Sec 91.217 copied here:
"91.217: Data correspondence between automatically reported pressure
altitude data and the pilot's altitude reference.
No person may operate any automatic pressure altitude reporting equipment
associated with a radar beacon transponder-
(a) When deactivation of that equipment is directed by ATC;
(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; or
(c) Unless the altimeters and digitizers in that equipment meet the
standards of TSO-C10b and TSO-C88, respectively."
So you can see that an altitude encoder in use must meet either be TSO'd or
comply with subparagraph (b) above.
Some people think that the encoder, altimeter, and transponder checks
required every two years by FAR Sections 91.411 and 91.413 meet the
requirements of subparagraph (b) above, but that is not the present position
of FAA HQ. They prescribe a more elaborate, almost impossible to accomplish
test.
So one solution to the problem created by having an EFIS with a non TSO'd
altitude encoder installed in your airplane is to install and use a separate
TSO'd altitude encoder.
If you want to read more on this subject go to the Matronic aeroelectric
list archive and search for 91.217.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
PS: Some EFIS manufacturers will claim that their altitude encoder "meets
TSO standards". Note that a claim of "meeting TSO standards" and being
actually TSO'd are not the same thing. Ironically some of these non TSO'd
altitude encoders are actually superior in performance and technology than
the standards required by the TSO. The EFIS manufacturers have chosen not to
obtain actual TSO approval for their altitude encoders because of the
expense and bureaucratic burden involved.
------------------------------------------------
> Time: 05:57:43 PM PST US
> Subject: Avionics-List: Questions on avionics
> From: "Rv9APlane" <rv9aplane@gmail.com>
>
>
> Hi all,
> I have a couple of basic questions I don't understand well:
>
> 1. What does it mean to "cage" an attitude indicator? I've never flown a
> plane
> that has had this option but I see it on some I'm considering for my
> homebuilt.
>
> 2. I want a light IFR panel and have read some things about Mode S
> transponders.
> Is there any advantage to having one over a Mode C other than the TIS
> capability?
>
> 3. Is purchasing a separate encoder necessary? I was planning on putting
> a Blue
> Mountain EFIS One in my plane (please no negative comments as I'm already
> committed),
> a Garmin 430W with a GI-106A CDI, and a Garmin 327 transponder (pending
> the answer to number 2 above) in my plane. I see some avionics vendors
> packaging
> in a separate encoder but don't really understand why.
>
> Thanks for your help
>
> --------
> Bruce Peters
> RV9A, Fuselage
> Bakersfield, CA
Message 2
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| Subject: | only hearing broken transmissions |
I have a problem with receiving on my COMM. It's normal except when I call the
local Tower. Then I get a broken transmission and have a hard time decifering
what the instructions are. What could be causing this?
Thanks
Ron
Message 3
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| Subject: | only hearing broken transmissions |
How is your squelch set? It may have to be opened a bit.
Noel
From: owner-avionics-list-server@matronics.com
[mailto:owner-avionics-list-server@matronics.com] On Behalf Of Ron Patterson
Sent: Tuesday, April 15, 2008 10:45 AM
Subject: Avionics-List: only hearing broken transmissions
I have a problem with receiving on my COMM. It's normal except when I call
the local Tower. Then I get a broken transmission and have a hard time
decifering what the instructions are. What could be causing this?
Thanks
Ron
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