allowable compass error...

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?

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?

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?

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?
|
|
|

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.

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?

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?
|
|
|

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

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

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