Sticky DG and DME distance question

Couple of questions.

Went up to practice some ILS approaches. While being vectored for my
approaches, my DG kept sticking through the 270 heading. First time on my
initial approach and the second approach. Third and fourth approaches, DG
acted normal, though seem a little off compared to the magnetic compass.
(gave me good practice for partial panel approaches!).

Also, my header bug seem to be frozen, couldn't move it at all. I ended up
using my magnetic compass and VFR GPS for my primary navigation and
tracking.

I had this happen once on the ground a long time ago, and never gave any
thought as it performed flawlessly in the air since. Vacuum gauge was
exactly where it should be.

Last thing I want to worry about in the clag is the DG. Is the DG worth
overhauling or just getting a new one???

I went to http://www.aircraftspruce.com/menus/in/gyros.html to see what
prices I am looking at, and it seemed all over the page in price. This
would be a part obviously I don't want to cheap out on, but I don't want to
buy a part that is has something in it I never will need.

Suggestions much appreciated. I figured to post this time b4 going out on
the limb.

DME question. While on my VOR Alpha approach back to MBO, ATC reported me
3 miles from the VOR, and my DME reported me 4 miles. This is the first
time I ever had a discrepancy that much. Anybody know what gives. My DME
seemed correct as it reflected 5 miles to my airport.

Allen

A Lieberman wrote:
DME question. While on my VOR Alpha approach back to MBO, ATC reported me
3 miles from the VOR, and my DME reported me 4 miles. This is the first
time I ever had a discrepancy that much. Anybody know what gives. My DME
seemed correct as it reflected 5 miles to my airport.

DME is slant range, ATC may be horizontal. How high were you?

On Sat, 09 Jul 2005 16:11:22 GMT, john smith wrote:

A Lieberman wrote:
DME question. While on my VOR Alpha approach back to MBO, ATC reported me
3 miles from the VOR, and my DME reported me 4 miles. This is the first
time I ever had a discrepancy that much. Anybody know what gives. My DME
seemed correct as it reflected 5 miles to my airport.

DME is slant range, ATC may be horizontal. How high were you?

Hi John,

I was at 2000 feet, which is about 1700 AGL.

Allen

A Lieberman wrote:
DME is slant range, ATC may be horizontal. How high were you?

I was at 2000 feet, which is about 1700 AGL.

Certainly not enough to give you an extra mile of slant range.

On Sat, 09 Jul 2005 16:53:57 GMT, john smith wrote:

A Lieberman wrote:
DME is slant range, ATC may be horizontal. How high were you?

I was at 2000 feet, which is about 1700 AGL.

Certainly not enough to give you an extra mile of slant range.

That was my thought in flight, in which I queried approach and asked him to
verify my distance.

Never noticed a problem before, and wondered if DME's can lose their
accuracy.

I didn't have the time to reprogram my GPS as I had to fly the plane, but
if I had the time, that would have been my next step.

Allen

Allen,

I can't remember if you ave an auto-pilot or not but if oyu don't we are
having a S-TEC30 installed in 3 weeks and will ahve an "extra" DG when
we are done. Works fine for us now but it doesn't have a heading bug.

Jon Kraus
4443H @ TYQ

A Lieberman wrote:
Couple of questions.

Went up to practice some ILS approaches. While being vectored for my
approaches, my DG kept sticking through the 270 heading. First time on my
initial approach and the second approach. Third and fourth approaches, DG
acted normal, though seem a little off compared to the magnetic compass.
(gave me good practice for partial panel approaches!).

Also, my header bug seem to be frozen, couldn't move it at all. I ended up
using my magnetic compass and VFR GPS for my primary navigation and
tracking.

I had this happen once on the ground a long time ago, and never gave any
thought as it performed flawlessly in the air since. Vacuum gauge was
exactly where it should be.

Last thing I want to worry about in the clag is the DG. Is the DG worth
overhauling or just getting a new one???

I went to http://www.aircraftspruce.com/menus/in/gyros.html to see what
prices I am looking at, and it seemed all over the page in price. This
would be a part obviously I don't want to cheap out on, but I don't want to
buy a part that is has something in it I never will need.

Suggestions much appreciated. I figured to post this time b4 going out on
the limb.

DME question. While on my VOR Alpha approach back to MBO, ATC reported me
3 miles from the VOR, and my DME reported me 4 miles. This is the first
time I ever had a discrepancy that much. Anybody know what gives. My DME
seemed correct as it reflected 5 miles to my airport.

Allen

Regarding the DG:

Sounds like a mechanical interference issue, which could account for both
the "snagging" on the 270 hdg and the bug being "frozen". The DG may only
need repair rather than full overhaul. Take it to a competent instrument
shop for diagnosis.

If it does need overhaul, whether to do it or not, in my opinion, depends
upon the quality of your unit. Some of the newer "cheapies" are not worth
overhauling while older, more robust designs are. Again, a good shop should
be able to advise you.

Regarding the DME issue: If your DME doesn't read to tenths of miles but
instead rounds to the nearest mile, the discrepancy may not exist. If the
DME read exactly 3.0 miles from the VOR and ATC told you 4, that could be
just a somewhat sloppy guesstimate by the controller. My understanding is
that they can bring up range rings on their new screens, but if a controller
is busy he/she might just "eyeball" it. In any event, I wouldn't worry too
much about it. If the DME indicates distance it is most likely functioning
properly. Measurement errors are conceivable but not common. Of course, as
you suggest it will be simple to do a check against your GPS

--
-Elliott Drucker

john smith wrote:
A Lieberman wrote:

DME is slant range, ATC may be horizontal. How high were you?


I was at 2000 feet, which is about 1700 AGL.


Certainly not enough to give you an extra mile of slant range.

You have a digital readout that gives exact distance. The controller
looks at the little space between you and the VOR symbol on the radar
scope. That symbol, a circle, is about a mile in diameter. The
controller looks at that space and he came up with 3 miles. He was off
a mile. No big deal.

wrote:

.. My understanding is
that they can bring up range rings on their new screens, but if a controller
is busy he/she might just "eyeball" it.

The controller almost always eyeballs it. As for range rings they are
alway displayed and are drawn around the radar site, not around an
individual airplane.

DME is slant range, ATC may be horizontal. How high were you?

I was at 2000 feet, which is about 1700 AGL.

Certainly not enough to give you an extra mile of slant range.

You have a digital readout that gives exact distance. The controller
looks at the little space between you and the VOR symbol on the radar
scope. That symbol, a circle, is about a mile in diameter. The
controller looks at that space and he came up with 3 miles. He was off
a mile. No big deal.

Another factor is the physical location of the DME site with respect to
the airport reference point.