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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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 Posted: Mon Jan 08, 2007 8:50 am Post subject: GRT GPS TSO |
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1/8/2006
Hello Bret, You quote GRT as writing: "The new RAIM-equipped version
provides integrity
monitoring and 5 updates per second to meet the requirements of IFR GPS TSO
C129 and C146."
This sounds like some subtle weasel wording to me. A piece of equipment
either meets the full TSO requirements and is marked TSO compliant or it is
not TSO'd.
The manufacturer does not get to cherry pick certain standards within the
TSO, or its references, just meet certain standards, and then mark the
equipment as TSO'd.
Most manufacturers who have gone to the expense and effort of obtaining TSO
approval for a piece of equipment are very eager to make that approval and
marking very evident to any prospective purchaser.
OC -- The best investment we will ever make is in gathering knowledge.
On 5 Jan 2007, at 22:05, Bret Smith wrote:
| Quote: | <smithhb(at)tds.net>
See http://www.grtavionics.com/documents/Horizon%20System%20Flyer.pdf
"The addition of the internal GPS receiver eliminates the need for an
external
GPS, or may be used as a backup to your primary GPS. Available in two
versions. The standard WAAS GPS module is perfect for VFR use, or
as backup
to an external GPS. The new RAIM-equipped version provides integrity
monitoring and 5 updates per second to meet the requirements of IFR
GPS
TSO C129 and C146."
Standard WAAS GPS Receiver with antenna $450
RAIM-Equipped WAAS GPS Receiver with antenna $750
Bret Smith
RV-9A (91314)
Mineral Bluff, GA
www.FlightInnovations.com
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wjrhamilton(at)optusnet.c
Guest
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| Posted: Mon Jan 08, 2007 6:57 pm Post subject: GRT GPS TSO |
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Folks,
There seems to be some confusion on standards here.
RAIM is only applicable to C129 GPS engines, when used as "stand alone" units (ie: not as part of a full FMCS system as installed in larger aircraft, giving a navigation capability semi-independent of RAIM, such as IRS to cover short term signal outages).
A major aim of the C145/146 RTCA docs. is to eliminate the shortcomings of the RAIM system, ie: when RAIM is lost the navigation function is lost, not something desirable with sole source navigation.
There are serious shortcomings with the way the TSO is written, it is not outcome based, but very prescriptive of process, and allows little room for alternative means of compliance with the TSO, hence the limited choice and very high price of C145/146.
As to TSO's, they are not necessarily a "one stop shop", but go in "steps and stages".
WAAS is another matter altogether, used to improve the derived position accuracy.
Cheers,
Bill Hamilton
At 03:47 AM 9/01/2007, you wrote:
| Quote: | --> Avionics-List message posted by: <bakerocb(at)cox.net>
1/8/2006
Hello Bret, You quote GRT as writing: "The new RAIM-equipped version provides integrity
monitoring and 5 updates per second to meet the requirements of IFR GPS TSO C129 and C146."
This sounds like some subtle weasel wording to me. A piece of equipment either meets the full TSO requirements and is marked TSO compliant or it is not TSO'd.
The manufacturer does not get to cherry pick certain standards within the TSO, or its references, just meet certain standards, and then mark the equipment as TSO'd.
Most manufacturers who have gone to the expense and effort of obtaining TSO approval for a piece of equipment are very eager to make that approval and marking very evident to any prospective purchaser.
OC -- The best investment we will ever make is in gathering knowledge.
On 5 Jan 2007, at 22:05, Bret Smith wrote:
| Quote: | <smithhb(at)tds.net>
See http://www.grtavionics.com/documents/Horizon%20System%20Flyer.pdf
"The addition of the internal GPS receiver eliminates the need for an
external
GPS, or may be used as a backup to your primary GPS. Available in two
versions. The standard WAAS GPS module is perfect for VFR use, or
as backup
to an external GPS. The new RAIM-equipped version provides integrity
monitoring and 5 updates per second to meet the requirements of IFR
GPS
TSO C129 and C146."
Standard WAAS GPS Receiver with antenna $450
RAIM-Equipped WAAS GPS Receiver with antenna $750
Bret Smith
RV-9A (91314)
Mineral Bluff, GA
www.FlightInnovations.com
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Dolores capitis non fero. Eos do.
[quote][b]
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
|
| Posted: Tue Jan 09, 2007 9:49 am Post subject: GRT GPS TSO |
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1/9/2007
Hello Bret, Continuing our dialogue.
1) You wrote: "If I get called out on the carpet for a non-TSO'd GPS, what
would they say
about my non-TSO'd TruTrak AP, Ray Allen trim system, GRT AHRS/Magnetometer,
HID homegrown landing lights, LED nav lights, etc?"
I believe that IFR / Night equipment for ABEA's falls into one of the
following categories:
1A) Purely optional equipment installed at the desire of the builder with no
existing regulatory requirement.
1B) Equipment required by FAR 91.205 (b), (c), and (d) because of wording in
the aircraft's Operating Limitations.
1C) Equipment required by FAR 91.205 (b), (c), and (d) because of wording in
the aircraft's Operating Limitation that is identified as needing to be
"approved" in those paragraphs.
1D) Equipment required by other paragraphs within the FAR's that would apply
to all aircraft, both type certificated with standard airworthiness
certificates and ABEA's with special airworthiness certificates.
1E) Equipment required by the AIM for certain types of operations that would
apply to all aircraft, both type certificated with standard airworthiness
certificates and ABEA's with special airworthiness certificates.
2) Your non-TSO'd TruTrak AP, Ray Allen trim system, GRT AHRS/Magnetometer,
HID homegrown landing lights and other equipment of that ilk would fall into
category 1A above and should generate no FAA criticism because it is not
TSO'd.
3) Your LED nav (position) lights would fall into category 1C above. See
91.205 (c), (2). If your initial ABEA airworthiness inspector issues the
aircraft a special airworthiness certificate he has, by implication,
"approved" those position lights in the name of the FAA Administrator (see
FAR 1.1). If he refuses to issue the certificate and demands to see TSO
markings because the regulations require it, he is wrong. If he refuses to
issue the certificate and demands to see either TSO markings or test results
showing that the lights meet FAR Part 23 position light standards, that is
within his prerogative as an inspector.
4) If you had only a non TSO'd GPS aboard and performed a specific operation
that the AIM required a TSO approved GPS for then you would not be in
compliance with 1E and may be subject to a charge of careless or reckless
operation (see FAR 91.13).
5) You wrote: "My understanding is that before flight into the national air
system, under
IFR, the pilot/builder of the OBAM aircraft must determine and document via
flight testing that the aircraft and it's systems meet the requirements for
IFR flight, night flight, etc."
This is certainly common sense. I would be interested in seeing some
regulatory basis for the above. The sources that I am aware of that cover
specific ABEA requirements for IFR and night flight are the Operating
Limitations for that aircraft and the references contained therein including
FAR 91.319.
FAR 91.319 (d), (2) reads "Operate under VFR day only, unless otherwise
specifically authorized by the Administrator."
The Operating Limitations will contain these words: "After completion of
Phase I flight testing, unless appropriately equipped for night and/or
instrument flight in accordance with 91.205, this aircraft is to be operated
under VFR, day only."
If the aircraft meets the "appropriately equipped" criteria it is considerd
by the FAA to have been given the Administrator's specific authorization to
fly at night and under IFR. What we have been discussing is what constitutes
"appropriately equipped".**
OC -- The best investment we will ever make is in gathering knowledge.
**PS: It is interesting to note that if the aircraft is given authorization
for aerobatic flight in the Operating Limitations that those maneuvers must
be specifically tested and documented in the aircraft's logbook.
PPS: You wrote: "This is a really interesting topic and I truly respect your
opinions.
It is evident you have a good understanding of these issues."
I appreciate your kind words.
---
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
|
| Posted: Tue Jan 09, 2007 10:52 am Post subject: GRT GPS TSO |
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1/9/2007
Hello Bill,
1) You wrote: " In some instances the regs require that a piece of equipment
MUST MEET TSO
STANDARDS. This is the case with transponders. In other instances the
equipment MUST BE TSO'd. This is the case with IFR GPS units."
Both TSO-145A and TSO-C146A dealing with IFR GPS units contain the following
paragraph (MPS means Minimum Performance Standards):
"g. Deviations. The FAA has provisions for using alternative or equivalent
means of compliance to the criteria set forth in the MPS of this TSO.
Applicants invoking these provisions shall demonstrate that an equivalent
level of safety is maintained and shall apply for a deviation per 14 CFR §
21.609"
2) TSO-C129a is an older TSO dealing with IFR GPS units and does not contain
specific alternate compliance words within it as is the case with more
current FAA TSO's, but here is a quote from the current AIM, note the use of
the word "equivalent":
"g. Equipment and Database Requirements.
1. Authorization to fly approaches under IFR using GPS avionics systems
requires that:
(a) A pilot use GPS avionics with TSO- C129, or equivalent, authorization in
class A1, B1, B3, C1, or C3; and......"
3) You wrote: "If simply meeting the TSO requirements is adequate, why
should a
manufacturer "go to the expense and effort"?"
My point exactly. Simply meeting some of the TSO requirements is not
adequate to fulfill the intent of the FAA TSO requirements.
GRT implies that they are completely fulfilling the FAA TSO intent by
writing: "The new RAIM-equipped version provides integrity monitoring and 5
updates per second to meet the requirements of IFR GPS TSO C129 and C146."
The equipment must either be TSO'd in accordance with the provisions of FAR
Part 21 Subpart O or FAA deviation approval from the TSO in accordance with
paragraph 21.609 must be obtained. Neither one of these are easy actions to
take and there is no indication in the GRT statement posted that either
action has been taken. Hence my suspicion of misleading weasel wording.
OC -- The best investment we will ever make is in gathering knowledge.
Time: 09:35:15 AM PST US
From: "Bill Denton" <bdenton(at)bdenton.com>
Subject: RE: GRT GPS TSO
"A piece of equipment either meets the full TSO requirements and is marked
TSO compliant or it is not TSO'd."
True, but not necessarily the point...
In some instances the regs require that a piece of equipment MUST MEET TSO
STANDARDS. This is the case with transponders.
In other instances the equipment MUST BE TSO'd. This is the case with IFR
GPS units.
You mentioned, "...manufacturers who have gone to the expense and effort of
obtaining TSO approval for a piece of equipment..."
If simply meeting the TSO requirements is adequate, why should a
manufacturer "go to the expense and effort"?
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
|
| Posted: Tue Jan 09, 2007 2:13 pm Post subject: GRT GPS TSO |
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1/9/2007
Hello Bret:
1) You wrote: "As you can see, the FAA has left a wide loophole with the
phrase "or equivalent"."
The FAA has learned from experience that locking technical requirements in
bureaucratic documents in concrete can come back to bite them when
technology comes up with a better mouse trap that was not envisioned in the
document. So now-a-days they caveat their TSO's with a statement to the
effect that "if you can do it just as good, but maybe a little differently
we are willing to listen to your proposal."
The process for a request to deviate is described in FAR 21.609 and the
loophole is not that wide. You might find that entire FAR 21 Subpart O
interesting reading. You can see that obtaining TSO approval and
manufacturing in accordance with that approval can be burdensome.**
2) You wrote: "It appears that, from my understanding, a GPS used for IFR
navigation must meet the minimum standard of RTCA/DO-208 in order to meet
the standard of TSO-C129 in order to be approved for IFR navigation."
I agree. Also realize that there are other documents referenced in TSO-C129a
that may contain standards that the unit may have to meet. And the FAA may
chose to not incorporate all provisions of referenced documents into the
TSO. Some TSO's are absolutely infuriating -- they say nothing of substance
technically themselves, but instead reference several documents (such as SAE
documents) that cost a bunch of money for just three or four pages.
3) You wrote: "Problem is, I don't see where the FAA requires the GPS to be
"certified".
I agree. The words theFAA uses are "authorization (to perfom IFR operations)
requires equipment approved IAW TSO -C129" (version C129a is the current
version). Lawyers may not agree with me, but I bet the Garmin marketing
people looked at the FAA terminology of "authorization" and "approved" and
said "certified sounds better to us".
4) You wrote: "I may be confused here but it seems that when Garmin states
their GNS430 is "IFR Approach Certified", they are only stating that this
receiver meets the requirements of TSO-C129."
I agree -- and also meeting all the pertinent references to TSO-C129a and
permitting the FAA oversight of Garmin's production of the GNS 430. (See FAR
21.615).
In addition now Garmin is stating that the GNS 430W meets all the
requirements of TSO 146a.
OC -- The best investment we will ever make is in gathering knowledge.
**PS: I worked with Lance Turk, founder of Vision Microsystems, on a special
size oil temperature probe for my TCM engine. He would not make the probe
for me because it would be non TSO'd and he did not want to contaminate his
FAA TSO approved production line. I wound up buying an empty brass
temperature probe body from Westach and sending it to Lance so that he could
have one of his technicians epoxy one of the Vision Microsystems special oil
temperature probe sensors into that brass body's cavity. Works like a charm.
---
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wjrhamilton(at)optusnet.c
Guest
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| Posted: Tue Jan 09, 2007 7:33 pm Post subject: GRT GPS TSO |
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Folks,
The difference between the performance of TSO'd equipment and apparently similar performance non-TSO'd equipment is not trivial.
There are very good reasons for requiring RAIM in C-129a units, for most of the non-TSO units, there is no or inadequate internal monitoring of the position solution and navigation output, as the accident record shows, that can be seriously fatal.
Please, please, please, everybody, don't go flying IFR with non-TSO GPS equipment, the database of demonstrated problems in the field is hair-raising.
Just for starters, the integrity of the basic software (not the navigation database) is unknown.
A hunt around the Australian CASA web site will find some interesting facts about incidents and accidents, world wide, using the wrong GPS in the wrong place, or drop Ian Mallet, head of the GNSS Office at CASA an email, I am certain he will provide you with some rather interesting references.
Cheers,
Bill Hamilton
At 09:10 AM 10/01/2007, you wrote:
[quote]--> Avionics-List message posted by: <bakerocb(at)cox.net>
1/9/2007
Hello Bret:
1) You wrote: "As you can see, the FAA has left a wide loophole with the phrase "or equivalent"."
The FAA has learned from experience that locking technical requirements in bureaucratic documents in concrete can come back to bite them when technology comes up with a better mouse trap that was not envisioned in the document. So now-a-days they caveat their TSO's with a statement to the effect that "if you can do it just as good, but maybe a little differently we are willing to listen to your proposal."
The process for a request to deviate is described in FAR 21.609 and the loophole is not that wide. You might find that entire FAR 21 Subpart O interesting reading. You can see that obtaining TSO approval and manufacturing in accordance with that approval can be burdensome.**
2) You wrote: "It appears that, from my understanding, a GPS used for IFR navigation must meet the minimum standard of RTCA/DO-208 in order to meet the standard of TSO-C129 in order to be approved for IFR navigation."
I agree. Also realize that there are other documents referenced in TSO-C129a that may contain standards that the unit may have to meet. And the FAA may chose to not incorporate all provisions of referenced documents into the TSO. Some TSO's are absolutely infuriating -- they say nothing of substance technically themselves, but instead reference several documents (such as SAE documents) that cost a bunch of money for just three or four pages.
3) You wrote: "Problem is, I don't see where the FAA requires the GPS to be "certified".
I agree. The words theFAA uses are "authorization (to perfom IFR operations) requires equipment approved IAW TSO -C129" (version C129a is the current version). Lawyers may not agree with me, but I bet the Garmin marketing people looked at the FAA terminology of "authorization" and "approved" and said "certified sounds better to us".
4) You wrote: "I may be confused here but it seems that when Garmin states their GNS430 is "IFR Approach Certified", they are only stating that this receiver meets the requirements of TSO-C129."
I agree -- and also meeting all the pertinent references to TSO-C129a and permitting the FAA oversight of Garmin's production of the GNS 430. (See FAR 21.615).
In addition now Garmin is stating that the GNS 430W meets all the requirements of TSO 146a.
OC -- The best investment we will ever make is in gathering knowledge.
**PS: I worked with Lance Turk, founder of Vision Microsystems, on a special size oil temperature probe for my TCM engine. He would not make the probe for me because it would be non TSO'd and he did not want to contaminate his FAA TSO approved production line. I wound up buying an empty brass temperature probe body from Westach and sending it to Lance so that he could have one of his technicians epoxy one of the Vision Microsystems special oil temperature probe sensors into that brass body's cavity. Works like a charm.
---
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wjrhamilton(at)optusnet.c
Guest
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| Posted: Wed Jan 10, 2007 2:10 am Post subject: GRT GPS TSO |
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|
Folks,
My comments were only directed at what seemed to me, to be some confusion about RAIM versus C145/146. I think my post has been taken a bit too widely.
Re. compliance standards for C145/146, believe me the way the TSO (and RTCA docs.) are written, they are very prescriptive, generic words about alternative means of compliance, however expressed, don't make much difference here. The difference in price between C129a(still the majority of production GPS, whether the final set is TSO or not) is really quite dramatic.
As to FAA requirements for IFR flight, I'm not buying into that, I have enough problems with our own rules, but I would much rather be working with the FAA system, it is quite reasonably pragmatic and at least has some flexibility.
Cheers,
Bill Hamilton
At 05:50 AM 10/01/2007, you wrote:
| Quote: | --> Avionics-List message posted by: <bakerocb(at)cox.net>
1/9/2007
Hello Bill,
1) You wrote: " In some instances the regs require that a piece of equipment MUST MEET TSO
STANDARDS. This is the case with transponders. In other instances the equipment MUST BE TSO'd. This is the case with IFR GPS units."
Both TSO-145A and TSO-C146A dealing with IFR GPS units contain the following paragraph (MPS means Minimum Performance Standards):
"g. Deviations. The FAA has provisions for using alternative or equivalent means of compliance to the criteria set forth in the MPS of this TSO. Applicants invoking these provisions shall demonstrate that an equivalent level of safety is maintained and shall apply for a deviation per 14 CFR § 21.609"
2) TSO-C129a is an older TSO dealing with IFR GPS units and does not contain specific alternate compliance words within it as is the case with more current FAA TSO's, but here is a quote from the current AIM, note the use of the word "equivalent":
"g. Equipment and Database Requirements.
1. Authorization to fly approaches under IFR using GPS avionics systems
requires that:
(a) A pilot use GPS avionics with TSO- C129, or equivalent, authorization in
class A1, B1, B3, C1, or C3; and......"
3) You wrote: "If simply meeting the TSO requirements is adequate, why should a
manufacturer "go to the expense and effort"?"
My point exactly. Simply meeting some of the TSO requirements is not adequate to fulfill the intent of the FAA TSO requirements.
GRT implies that they are completely fulfilling the FAA TSO intent by writing: "The new RAIM-equipped version provides integrity monitoring and 5 updates per second to meet the requirements of IFR GPS TSO C129 and C146."
The equipment must either be TSO'd in accordance with the provisions of FAR Part 21 Subpart O or FAA deviation approval from the TSO in accordance with paragraph 21.609 must be obtained. Neither one of these are easy actions to take and there is no indication in the GRT statement posted that either action has been taken. Hence my suspicion of misleading weasel wording.
OC -- The best investment we will ever make is in gathering knowledge.
Time: 09:35:15 AM PST US
From: "Bill Denton" <bdenton(at)bdenton.com>
Subject: RE: AeroElectric-List: GRT GPS TSO
"A piece of equipment either meets the full TSO requirements and is marked
TSO compliant or it is not TSO'd."
True, but not necessarily the point...
In some instances the regs require that a piece of equipment MUST MEET TSO
STANDARDS. This is the case with transponders.
In other instances the equipment MUST BE TSO'd. This is the case with IFR
GPS units.
You mentioned, "...manufacturers who have gone to the expense and effort of
obtaining TSO approval for a piece of equipment..."
If simply meeting the TSO requirements is adequate, why should a
manufacturer "go to the expense and effort"?
===========
Avionics-List Email Forum -
http://www.matronics.com/Navigator?Avionics-List
===========
; - NEW MATRONICS WEB FORUMS -
http://forums.matronics.com
===========
|
CONFIDENTIALITY & PRIVILEGE NOTICE
W.J.R.Hamilton,Glenalmond Group Companies,Fighter Flights Internet Services and Warbirds.Net.<wjrhamilton(at)optusnet.com.au> & <GlenalmondEngineering(at)Gmail.com>
This message is intended for and should only be used by the addressee. It is confidential and may contain legally privileged information.If you are not the intended recipient any use distribution,disclosure or copying of this message is strictly prohibited.Confidentiality and legal privilege attached to this communication are not waived or lost by reason of the mistaken delivery to you.
If you have received this message in error, please notify us immediately to: Australia 61 (0)408 876 526
Dolores capitis non fero. Eos do.
[quote][b]
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wjrhamilton(at)optusnet.c
Guest
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| Posted: Wed Jan 10, 2007 2:16 am Post subject: GRT GPS TSO |
|
|
Folks,
My comments were only directed at what seemed to me, to be some confusion about RAIM versus C145/146. I think my post has been taken a bit too widely.
Re. compliance standards for C145/146, believe me the way the TSO (and RTCA docs.) are written, they are very prescriptive, generic words about alternative means of compliance, however expressed, don't make much difference here. The difference in price between C129a(still the majority of production GPS, whether the final set is TSO or not) is really quite dramatic.
As to FAA requirements for IFR flight, I'm not buying into that, I have enough problems with our own rules, but I would much rather be working with the FAA system, it is quite reasonably pragmatic and at least has some flexibility.
Cheers,
Bill Hamilton
At 05:50 AM 10/01/2007, you wrote:
| Quote: | --> Avionics-List message posted by: <bakerocb(at)cox.net>
1/9/2007
Hello Bill,
1) You wrote: " In some instances the regs require that a piece of equipment MUST MEET TSO
STANDARDS. This is the case with transponders. In other instances the equipment MUST BE TSO'd. This is the case with IFR GPS units."
Both TSO-145A and TSO-C146A dealing with IFR GPS units contain the following paragraph (MPS means Minimum Performance Standards):
"g. Deviations. The FAA has provisions for using alternative or equivalent means of compliance to the criteria set forth in the MPS of this TSO. Applicants invoking these provisions shall demonstrate that an equivalent level of safety is maintained and shall apply for a deviation per 14 CFR § 21.609"
2) TSO-C129a is an older TSO dealing with IFR GPS units and does not contain specific alternate compliance words within it as is the case with more current FAA TSO's, but here is a quote from the current AIM, note the use of the word "equivalent":
"g. Equipment and Database Requirements.
1. Authorization to fly approaches under IFR using GPS avionics systems
requires that:
(a) A pilot use GPS avionics with TSO- C129, or equivalent, authorization in
class A1, B1, B3, C1, or C3; and......"
3) You wrote: "If simply meeting the TSO requirements is adequate, why should a
manufacturer "go to the expense and effort"?"
My point exactly. Simply meeting some of the TSO requirements is not adequate to fulfill the intent of the FAA TSO requirements.
GRT implies that they are completely fulfilling the FAA TSO intent by writing: "The new RAIM-equipped version provides integrity monitoring and 5 updates per second to meet the requirements of IFR GPS TSO C129 and C146."
The equipment must either be TSO'd in accordance with the provisions of FAR Part 21 Subpart O or FAA deviation approval from the TSO in accordance with paragraph 21.609 must be obtained. Neither one of these are easy actions to take and there is no indication in the GRT statement posted that either action has been taken. Hence my suspicion of misleading weasel wording.
OC -- The best investment we will ever make is in gathering knowledge.
Time: 09:35:15 AM PST US
From: "Bill Denton" <bdenton(at)bdenton.com>
Subject: RE: AeroElectric-List: GRT GPS TSO
"A piece of equipment either meets the full TSO requirements and is marked
TSO compliant or it is not TSO'd."
True, but not necessarily the point...
In some instances the regs require that a piece of equipment MUST MEET TSO
STANDARDS. This is the case with transponders.
In other instances the equipment MUST BE TSO'd. This is the case with IFR
GPS units.
You mentioned, "...manufacturers who have gone to the expense and effort of
obtaining TSO approval for a piece of equipment..."
If simply meeting the TSO requirements is adequate, why should a
manufacturer "go to the expense and effort"?
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zenith601xl(at)gmail.com
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| Posted: Wed Jan 10, 2007 5:48 am Post subject: GRT GPS TSO |
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Enough already!
On 1/9/07, W J R HAMILTON <wjrhamilton(at)optusnet.com.au (wjrhamilton(at)optusnet.com.au)> wrote: [quote] Folks,
The difference between the performance of TSO'd equipment and apparently similar performance non-TSO'd equipment is not trivial.
There are very good reasons for requiring RAIM in C-129a units, for most of the non-TSO units, there is no or inadequate internal monitoring of the position solution and navigation output, as the accident record shows, that can be seriously fatal.
Please, please, please, everybody, don't go flying IFR with non-TSO GPS equipment, the database of demonstrated problems in the field is hair-raising.
Just for starters, the integrity of the basic software (not the navigation database) is unknown.
A hunt around the Australian CASA web site will find some interesting facts about incidents and accidents, world wide, using the wrong GPS in the wrong place, or drop Ian Mallet, head of the GNSS Office at CASA an email, I am certain he will provide you with some rather interesting references.
Cheers,
Bill Hamilton
At 09:10 AM 10/01/2007, you wrote:
[quote] --> Avionics-List message posted by: <bakerocb(at)cox.net (bakerocb(at)cox.net)>
1/9/2007
Hello Bret:
1) You wrote: "As you can see, the FAA has left a wide loophole with the phrase "or equivalent"."
The FAA has learned from experience that locking technical requirements in bureaucratic documents in concrete can come back to bite them when technology comes up with a better mouse trap that was not envisioned in the document. So now-a-days they caveat their TSO's with a statement to the effect that "if you can do it just as good, but maybe a little differently we are willing to listen to your proposal."
The process for a request to deviate is described in FAR 21.609 and the loophole is not that wide. You might find that entire FAR 21 Subpart O interesting reading. You can see that obtaining TSO approval and manufacturing in accordance with that approval can be burdensome.**
2) You wrote: "It appears that, from my understanding, a GPS used for IFR navigation must meet the minimum standard of RTCA/DO-208 in order to meet the standard of TSO-C129 in order to be approved for IFR navigation."
I agree. Also realize that there are other documents referenced in TSO-C129a that may contain standards that the unit may have to meet. And the FAA may chose to not incorporate all provisions of referenced documents into the TSO. Some TSO's are absolutely infuriating -- they say nothing of substance technically themselves, but instead reference several documents (such as SAE documents) that cost a bunch of money for just three or four pages.
3) You wrote: "Problem is, I don't see where the FAA requires the GPS to be "certified".
I agree. The words theFAA uses are "authorization (to perfom IFR operations) requires equipment approved IAW TSO -C129" (version C129a is the current version). Lawyers may not agree with me, but I bet the Garmin marketing people looked at the FAA terminology of "authorization" and "approved" and said "certified sounds better to us".
4) You wrote: "I may be confused here but it seems that when Garmin states their GNS430 is "IFR Approach Certified", they are only stating that this receiver meets the requirements of TSO-C129."
I agree -- and also meeting all the pertinent references to TSO-C129a and permitting the FAA oversight of Garmin's production of the GNS 430. (See FAR 21.615).
In addition now Garmin is stating that the GNS 430W meets all the requirements of TSO 146a.
OC -- The best investment we will ever make is in gathering knowledge.
**PS: I worked with Lance Turk, founder of Vision Microsystems, on a special size oil temperature probe for my TCM engine. He would not make the probe for me because it would be non TSO'd and he did not want to contaminate his FAA TSO approved production line. I wound up buying an empty brass temperature probe body from Westach and sending it to Lance so that he could have one of his technicians epoxy one of the Vision Microsystems special oil temperature probe sensors into that brass body's cavity. Works like a charm.
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