Vertical Card Compasses vs GPS Compass Display

"Tom N." wrote in message
ps.com...
On Sep 20, 8:09 pm, Bill Zaleski wrote:
On Fri, 21 Sep 2007 00:01:32 +0100, Martin Gregorie





wrote:
wrote:

Some of the GPS's have a compass display. Is that a viable alternative
to a vertical card compass (still having regular old style compass as
backup) ?

That works for me. I have a Garmin GPS II+ and the bearing page is my
preferred directional display when I'm flying. My compass is tucked away
at the bottom of the panel for emergency use only.

As it sounds like you haven't seen a GPS II+, here's a description. The
bearing page shows a circular disk containing a large arrow that points
at the selected waypoint. Round it is a ring showing the main compass
points. Like a compass card, the ring rotates so heading is always at
the top of the display. For good measure the heading and waypoint
bearing are also shown as three digit numbers.

Some other basic handheld Garmins (12XL, GPS III+, eTrex, GPSMAP 60 and
76) also have this display page.

You may still be able to find the older models (GPS II+, III+, 12XL) on
eBay. Of the current basic handhelds, the GPSMAP series look the best
suited for our use because all controls are on the front next to the
display. The Geko series are too small to be practical while the eTrex
series have their controls on the edges which probably makes a panel
mounted one harder to use.

A GPS can not, and will not display heading. No GPS can do this. The
most it can do is display track, which is also heading only if there
is no wind correction. It can not be substituted for a compass.- Hide
quoted text -

- Show quoted text -

I love my vertical card compass. It is a PAI-700. I have it mounted
on the bottom of the pedestal where I occasionally look at it. No
problems with sticking. I use it to verify rough heading before my
GPS has a chance to register my track. In some parts of the country
the landscape is monotonous without distinguishing landmarks such as
mountains or ridges. I also believe that a compass is required
equipment for any aircraft - GPS is not a substitute.

Tom Nau


We need an FAR reference.

Does the FAR say that ALL aircraft MUST have a compass? Or does it say that
the aircraft in question must be equipped as shown in the Minimum Equipment
List found in the certification documents and reflected in the POH? I think
it's the later where if the POH doesn't list a compass as required
equipment, you can fly without one. Of course, MOST aircraft POH's do list
a compass - but not all.

Yes it's true that ordinary GPS receivers do not generate and display
compass heading - but some do. These are dual-antenna, carrier-phase
receivers that generate compass heading data referenced to TRUE NORTH. This
heading data is in NMEA format that some glide computers can use to generate
extremely accurate real-time vector wind.

Whether a particular receiver does or does not display compass data, ground
track is far more useful anyway. I care about the direction I'm going much
more than the direction I'm pointing. A long time ago I was given a vector
of 270 degrees magnetic when there was a 50 knot north wind. The resulting
ground track was WSW. The controller grumbled at me until I turned NW to
achieve a ground track of 270. The ATC controllers were much happier with
me when I flew ground track vectors.

Bill Daniels