allowable compass error...

[Casey Wilson]

My FARAIM is at my daughter's house and I can't find anything on the 'net to
answer my questions. Please indulge me....

Scenario:
1) line up with runway centerline[for my hypothetical, the runway is
dead nuts to the compass]
2) note compass heading
3) add/subtract compass card correction

Questions:
1) How much error is allowable between known heading and corrected
compass reading?
2) Does a significant error down the airplane as unworthy?
3) Where can I find applicable references?

[Bob Gardner]

I searched for "compass error" on my Summit CD-ROM and got 11 hits, all
definitions except one that, when referring to radio installations, said
that the compass card had to be checked with radios both on and off, with
the max allowable deviation 10 degrees. I don't think that there are any
regs that speak directly to the situation you describe.

Bob Gardner

"Casey Wilson" <N2310D @ gmail.com> wrote in message
news:xQllg.2530$RU4.408@trnddc03...
> My FARAIM is at my daughter's house and I can't find anything on the 'net
> to answer my questions. Please indulge me....
>
> Scenario:
> 1) line up with runway centerline[for my hypothetical, the runway is
> dead nuts to the compass]
> 2) note compass heading
> 3) add/subtract compass card correction
>
> Questions:
> 1) How much error is allowable between known heading and corrected
> compass reading?
> 2) Does a significant error down the airplane as unworthy?
> 3) Where can I find applicable references?
>
>
>

[RomeoMike]

Don't know, but if you are using the runway heading to judge whether
your compass reading is in error, remember that runway headings are not
always true. There are other ways to calibrate your compass.

Casey Wilson wrote:
> My FARAIM is at my daughter's house and I can't find anything on the 'net to
> answer my questions. Please indulge me....
>
> Scenario:
> 1) line up with runway centerline[for my hypothetical, the runway is
> dead nuts to the compass]
> 2) note compass heading
> 3) add/subtract compass card correction
>
> Questions:
> 1) How much error is allowable between known heading and corrected
> compass reading?
> 2) Does a significant error down the airplane as unworthy?
> 3) Where can I find applicable references?
>
>
>

[Jim Macklin]

Part 23 and Part 43.

Runways are to the nearest 5 degrees and will be renumbered
as required. During the annual inspection the compass
should be checked to be sure it is within degrees on all
headings and any time there has been a change in the
airplane that would cause the deviation to change.


Yes, an error greater than 10 degrees, even with the
correction card, requires correction.


--
James H. Macklin
ATP,CFI,A&P

"RomeoMike" > wrote in message
...
| Don't know, but if you are using the runway heading to
judge whether
| your compass reading is in error, remember that runway
headings are not
| always true. There are other ways to calibrate your
compass.
|
| Casey Wilson wrote:
| > My FARAIM is at my daughter's house and I can't find
anything on the 'net to
| > answer my questions. Please indulge me....
| >
| > Scenario:
| > 1) line up with runway centerline[for my
hypothetical, the runway is
| > dead nuts to the compass]
| > 2) note compass heading
| > 3) add/subtract compass card correction
| >
| > Questions:
| > 1) How much error is allowable between known heading
and corrected
| > compass reading?
| > 2) Does a significant error down the airplane as
unworthy?
| > 3) Where can I find applicable references?
| >
| >
| >

[Jose]

> Runways are to the nearest 5 degrees and will be renumbered
> as required.

Usually. LAX has five runways with the same alignment; they cheat the
numbers.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Casey Wilson]

Thanks, I know about compass roses and swinging the compass. What I'm
looking for is an indication that the compass needs swinging. That's why my
hypothetical scenario stated that the runway alignment is correct. That does
happen, by the way, even if the odds are against it.

"RomeoMike" > wrote in message
...
> Don't know, but if you are using the runway heading to judge whether your
> compass reading is in error, remember that runway headings are not always
> true. There are other ways to calibrate your compass.
>
> Casey Wilson wrote:
>> My FARAIM is at my daughter's house and I can't find anything on the 'net
>> to answer my questions. Please indulge me....
>>
>> Scenario:
>> 1) line up with runway centerline[for my hypothetical, the runway is
>> dead nuts to the compass]
>> 2) note compass heading
>> 3) add/subtract compass card correction
>>
>> Questions:
>> 1) How much error is allowable between known heading and corrected
>> compass reading?
>> 2) Does a significant error down the airplane as unworthy?
>> 3) Where can I find applicable references?
>>
>>

[Casey Wilson]

Okay, Jim, I think you said an error greater than ten degrees will ground
the airplance. I'll accept that. Can you give me the reference for the ten
degree figure? Are you saying that the airplane should be taken to the
compass rose during the annual or is there some "quick check?"

"Jim Macklin" > wrote in message
news:NBplg.49163$ZW3.16236@dukeread04...
> Part 23 and Part 43.
>
> Runways are to the nearest 5 degrees and will be renumbered
> as required. During the annual inspection the compass
> should be checked to be sure it is within degrees on all
> headings and any time there has been a change in the
> airplane that would cause the deviation to change.
>
>
> Yes, an error greater than 10 degrees, even with the
> correction card, requires correction.
>
>
> --
> James H. Macklin
> ATP,CFI,A&P
>
> "RomeoMike" > wrote in message
> ...
> | Don't know, but if you are using the runway heading to
> judge whether
> | your compass reading is in error, remember that runway
> headings are not
> | always true. There are other ways to calibrate your
> compass.
> |
> | Casey Wilson wrote:
> | > My FARAIM is at my daughter's house and I can't find
> anything on the 'net to
> | > answer my questions. Please indulge me....
> | >
> | > Scenario:
> | > 1) line up with runway centerline[for my
> hypothetical, the runway is
> | > dead nuts to the compass]
> | > 2) note compass heading
> | > 3) add/subtract compass card correction
> | >
> | > Questions:
> | > 1) How much error is allowable between known heading
> and corrected
> | > compass reading?
> | > 2) Does a significant error down the airplane as
> unworthy?
> | > 3) Where can I find applicable references?
> | >
> | >
> | >
>
>

[GeorgeC]

I had a thought, what do you think? If you are tracking a radial on a VOR
couldn't you compare the radial to the compass heading and get a good idea of
the compass error?


On Mon, 19 Jun 2006 14:17:23 GMT, "Casey Wilson" <N2310D @ gmail.com> wrote:

>Thanks, I know about compass roses and swinging the compass. What I'm
>looking for is an indication that the compass needs swinging. That's why my
>hypothetical scenario stated that the runway alignment is correct. That does
>happen, by the way, even if the odds are against it.

GeorgeC

[Casey Wilson]

I've got no problem with that George, as a general indication of
discrepancy. On the other hand, I sure that some of the nitpickers in our
RAP community would want to immediately toss in the VOR calibration and
accuracy, crab angle caused by crosswind drift relative to the actual course
versus heading, yadda, yadda...

What my question really is, is how much difference (for discussion I'll
agree that the method described is acceptable) between that compass heading
and the VOR radial is tolerable before the airplane should be grounded and
the compass readjusted, repaired, or replaced? Secondly, what is the
applicable reference for that?


"GeorgeC" > wrote in message
...
>I had a thought, what do you think? If you are tracking a radial on a VOR
> couldn't you compare the radial to the compass heading and get a good idea
> of
> the compass error?
>
>
> On Mon, 19 Jun 2006 14:17:23 GMT, "Casey Wilson" <N2310D @ gmail.com>
> wrote:
>
>>Thanks, I know about compass roses and swinging the compass. What I'm
>>looking for is an indication that the compass needs swinging. That's why
>>my
>>hypothetical scenario stated that the runway alignment is correct. That
>>does
>>happen, by the way, even if the odds are against it.
>
> GeorgeC

[Jim Macklin]

No, the radial can be flown on any heading. What you can do
in parts of the country that have been laid out with section
line grids of roads and highways, is fly a heading along a
road and not correct for drift. These roads were laid out
to true north/south/east and west. You can apply the local
variation to get the magnetic of that road. You manually
set your heading indicator and then turn to magnetic north,
etc, and check the compass. You can thus swing the compass
in-flight on every 30 degree heading and write down the
observed error. You should probably do this with various
combinations of configuration.

I remember a twin that had a compass error of 30 degrees if
the left alternator was off-line. I seem to remember that
the problems was in the right alternator, the compass would
point to the right engine.

You're probably most concerned about compass errors when the
compass is all you have, so I'd check with alt/gen off,
radios off as well as with all systems on-line. Make a grid
and fill in the blanks. Check the heading indicator on each
true road to be sure that you have compensated for gyro
drift. If you have a remote compass, manually set the
heading to check at least the four headings on the road.


If you find any errors greater than 10 degrees on any
heading, you will need some professional assistance to
determine why and fix the problem. It can be electrical
leakage, or some local magnetic item, even a lightening
strike could have magnetized the engine mount or other steel
parts of the airplane.


--
James H. Macklin
ATP,CFI,A&P

"GeorgeC" > wrote in message
...
|I had a thought, what do you think? If you are tracking a
radial on a VOR
| couldn't you compare the radial to the compass heading and
get a good idea of
| the compass error?
|
|
| On Mon, 19 Jun 2006 14:17:23 GMT, "Casey Wilson" <N2310D @
gmail.com> wrote:
|
| >Thanks, I know about compass roses and swinging the
compass. What I'm
| >looking for is an indication that the compass needs
swinging. That's why my
| >hypothetical scenario stated that the runway alignment is
correct. That does
| >happen, by the way, even if the odds are against it.
|
| GeorgeC

[Jim Macklin]

§ 23.1327 Magnetic direction indicator.
(a) Except as provided in paragraph (b) of this section-

(1) Each magnetic direction indicator must be installed so
that its accuracy is not excessively affected by the
airplane's vibration or magnetic fields; and

(2) The compensated installation may not have a deviation in
level flight, greater than ten degrees on any heading.

(b) A magnetic nonstabilized direction indicator may deviate
more than ten degrees due to the operation of electrically
powered systems such as electrically heated windshields if
either a magnetic stabilized direction indicator, which does
not have a deviation in level flight greater than ten
degrees on any heading, or a gyroscopic direction indicator,
is installed. Deviations of a magnetic nonstabilized
direction indicator of more than 10 degrees must be
placarded in accordance with §23.1547(e).

[Amdt. 23-20, 42 FR 36969, July 18, 1977]


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--
James H. Macklin
ATP,CFI,A&P

"Casey Wilson" <N2310D @ gmail.com> wrote in message
news:0sylg.2531$DI2.2291@trnddc05...
| Okay, Jim, I think you said an error greater than ten
degrees will ground
| the airplance. I'll accept that. Can you give me the
reference for the ten
| degree figure? Are you saying that the airplane should be
taken to the
| compass rose during the annual or is there some "quick
check?"
|
| "Jim Macklin" > wrote
in message
| news:NBplg.49163$ZW3.16236@dukeread04...
| > Part 23 and Part 43.
| >
| > Runways are to the nearest 5 degrees and will be
renumbered
| > as required. During the annual inspection the compass
| > should be checked to be sure it is within degrees on all
| > headings and any time there has been a change in the
| > airplane that would cause the deviation to change.
| >
| >
| > Yes, an error greater than 10 degrees, even with the
| > correction card, requires correction.
| >
| >
| > --
| > James H. Macklin
| > ATP,CFI,A&P
| >
| > "RomeoMike" > wrote in
message
| > ...
| > | Don't know, but if you are using the runway heading to
| > judge whether
| > | your compass reading is in error, remember that runway
| > headings are not
| > | always true. There are other ways to calibrate your
| > compass.
| > |
| > | Casey Wilson wrote:
| > | > My FARAIM is at my daughter's house and I can't find
| > anything on the 'net to
| > | > answer my questions. Please indulge me....
| > | >
| > | > Scenario:
| > | > 1) line up with runway centerline[for my
| > hypothetical, the runway is
| > | > dead nuts to the compass]
| > | > 2) note compass heading
| > | > 3) add/subtract compass card correction
| > | >
| > | > Questions:
| > | > 1) How much error is allowable between known
heading
| > and corrected
| > | > compass reading?
| > | > 2) Does a significant error down the airplane as
| > unworthy?
| > | > 3) Where can I find applicable references?
| > | >
| > | >
| > | >
| >
| >
|
|

[Jose]

> If you are tracking a radial on a VOR
> couldn't you compare the radial to the compass heading and get a good idea of
> the compass error?

Only with no crosswind.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Jim Macklin]

A 100 KIAS with a 50 knot 90 degree crosswind can be flown
without any compass at all, you just need a stable heading
reference, but it is so far from being close to any easy
reference, it tells you nothing about the compass accuracy.

You need an accurate compass/heading reference for ADF
tracking and it does help with getting and staying on course
with radio navigation.

The question is not how bad can it be, but how good can it
be.



--
James H. Macklin
ATP,CFI,A&P

"Casey Wilson" <N2310D @ gmail.com> wrote in message
news:Y3Flg.22377$YI2.20622@trnddc01...
| I've got no problem with that George, as a general
indication of
| discrepancy. On the other hand, I sure that some of the
nitpickers in our
| RAP community would want to immediately toss in the VOR
calibration and
| accuracy, crab angle caused by crosswind drift relative to
the actual course
| versus heading, yadda, yadda...
|
| What my question really is, is how much difference (for
discussion I'll
| agree that the method described is acceptable) between
that compass heading
| and the VOR radial is tolerable before the airplane should
be grounded and
| the compass readjusted, repaired, or replaced? Secondly,
what is the
| applicable reference for that?
|
|
| "GeorgeC" > wrote in message
| ...
| >I had a thought, what do you think? If you are tracking
a radial on a VOR
| > couldn't you compare the radial to the compass heading
and get a good idea
| > of
| > the compass error?
| >
| >
| > On Mon, 19 Jun 2006 14:17:23 GMT, "Casey Wilson" <N2310D
@ gmail.com>
| > wrote:
| >
| >>Thanks, I know about compass roses and swinging the
compass. What I'm
| >>looking for is an indication that the compass needs
swinging. That's why
| >>my
| >>hypothetical scenario stated that the runway alignment
is correct. That
| >>does
| >>happen, by the way, even if the odds are against it.
| >
| > GeorgeC
|
|

[Casey Wilson]

Ah, Jim, finally.... thank you, thank you...

Casey


"Jim Macklin" > wrote in message
news:FqFlg.49206$ZW3.9522@dukeread04...
>' 23.1327 Magnetic direction indicator.
> (a) Except as provided in paragraph (b) of this section-
>
> (1) Each magnetic direction indicator must be installed so
> that its accuracy is not excessively affected by the
> airplane's vibration or magnetic fields; and
>
> (2) The compensated installation may not have a deviation in
> level flight, greater than ten degrees on any heading.
>
> (b) A magnetic nonstabilized direction indicator may deviate
> more than ten degrees due to the operation of electrically
> powered systems such as electrically heated windshields if
> either a magnetic stabilized direction indicator, which does
> not have a deviation in level flight greater than ten
> degrees on any heading, or a gyroscopic direction indicator,
> is installed. Deviations of a magnetic nonstabilized
> direction indicator of more than 10 degrees must be
> placarded in accordance with '23.1547(e).
>
> [Amdt. 23-20, 42 FR 36969, July 18, 1977]

[GeorgeC]

I misread read your post. I "read" that you wanted to check to see if your
compass was out of tolerance, but your question was what were the tolerances.
Which I see James answered.

On Mon, 19 Jun 2006 21:56:08 GMT, "Casey Wilson" <N2310D @ gmail.com> wrote:


>What my question really is, is how much difference (for discussion I'll
>agree that the method described is acceptable) between that compass heading
>and the VOR radial is tolerable before the airplane should be grounded and
>the compass readjusted, repaired, or replaced? Secondly, what is the
>applicable reference for that?

GeorgeC