Remote Compass

[jrenwick]

So, if I understand this right:

Set the "bug" (the split arrow) to the magnetic course, and point the aircraft so that the difference between the bug and the compass needle is equal to the WCA. If the compass needle doesn't remain steady relative to the bug, it means the winds are different than forecast, and you need to figure out a new WCA. Similar to tracking an ADF course in a crosswind.

Is that the way it works?

John

[bpaige]

So, if I understand this right:

Set the "bug" (the split arrow) to the magnetic course, and point the aircraft so that the difference between the bug and the compass needle is equal to the WCA. If the compass needle doesn't remain steady relative to the bug, it means the winds are different than forecast, and you need to figure out a new WCA. Similar to tracking an ADF course in a crosswind.

Is that the way it works?

John

The instrument is essentially an electronic magnetic compass. It is a heading indicator in the same sense as a DG. It is very stable (unlike a liquid filled compass) and always points in the right direction (unlike a DG). The 'bug' is a visual aid. It is set to the desired heading manually. Keeping the compass needle centered in the 'bug' is easier than keeping it pointed at a particular point on the compass dial. Reversing direction 180 deg is a simple matter of turning the plane until the compass needle is pointing backwards and centered inside the 'bug' . The instrument does not help determine the correct heading, it just displays the current heading.

[hilltop170]

Where is the Blue Leader to explain this instrument.

He's in Idaho for the summer in a motor home, probably happy there is no computer around.

[johneeb]

Where is the Blue Leader to explain this instrument.

He's in Idaho for the summer in a motor home, probably happy there is no computer around.

Richard,
I hope you are right, it always gives us pause when we do not hear from him for awhile.

[DaveF]

... certain that a remote compass would not be part of any engine installation instructions. I'll bet those familiar with the instruction will chime in here and confirm my suspicion.

You're right, Bruce. The compass isn't part of the Avcon conversion.

[GAHorn]

There are, in history, several notable instances in which remote compasses are used. Lindbergh had an "earth inductor" compass which was a remote unit similar to the one in this thread, except as for power-source. (Lindbergh's had it's own wind-generated power.)
http://www.oldbeacon.com/beacon/earth_i ... ompass.htm


Ty Sundstrom, of the LIndbergh group had some interesting comments on the installation.
The original Earth Inductor Compass (EIC) installed in the Spirit was found to be defective while in San Diego.

A replacement was not available so it was left in the aircraft until being removed and replaced in New York. The replacement EIC was of a slightly different model as well,
which can be noted externally by the wind generator cups (looks just like a wind cup anemometer) on the later version

http://www.charleslindbergh.com/images2 ... _aug25.jpg

and the turbine style disc on the first (appears as a small round tuna can size disc on the top of the vertical mast on the back of the fuselage).

http://www.charleslindbergh.com/hall/1/ ... st1970.jpg

The magnetic compass (sometimes called a wet compass) was originally installed on the cockpit floorboard just to the left of the control stick torque tube in San Diego. You can see the original magnetic compass installation in this view;

http://www.charleslindbergh.com/hall/5/ ... st1970.jpg

The deviation create by the steel torque tube could not be compensated for because the torque tube would always be rotating slightly left and right as the ailerons were moved using the control stick.

Once the Spirit was in New York, the magnetic compass was replaced with a different unit as well.

It was relocated to a position directly in front of Lindbergh's head. The compass card which is the internal moving part of the compass which has the compass headings on it (north, east, south, and west) was printed backwards on the replacement compass which necessitated the use of a mirror on the instrument panel to actually read the compass. The compass installed apparently was not specifically made for the Spirit installation hence the reverse reading compass card.

Reverse reading compass cards were put in compasses which had remote installation locations which placed them well away from any substantial steel structure to improve the accuracy of the compass. Unfortunately, this also placed it sometimes out of direct view of the pilot so the compass was modified for this specific type of installation to read after being seen through a reflecting mirror.

The final installation of the magnetic compass can be seen in this view;

http://www.geocities.com/CapeCanaveral/ ... irinst.jpg

http://z.about.com/d/dc/1/5/W/3/WEB10067-2003h.jpg

It is interesting to note that Lindbergh had trouble with both the magnetic compass and the earth inductor compass at various times and once both failed him and he made the largest over water navigational error that was survived by anyone in a single engine aircraft when he flew out across the Caribbean at night when returning from South America on his good will tour there. The details of this adventure can be found in several places including Lindbergh’s log in the back of his book, the Spirit of St. Louis.

The work carried out on the instruments while in New York was done so by the Pioneer Instrument Company’s field rep. The instruments were originally bought from the Ryan Airlines Company but the earth inductor compass was purchased by Ryan from Pioneer Instrument Company. The special instruments installed in the Spirit were over and above the construction cost as seen in this invoice;

http://www.charleslindbergh.com/images2/Roberts8.JPG

There were many small changes to the Spirit while in New York;

The propeller spinner was replaced when the original was found to be cracked.
A carb air heater, duct hoses and cockpit control for carb air heater were installed.
The cockpit lights were disabled and their heavy telephone batteries removed.
Mirror was added to instrument panel to read replacement mirror.
The tailskid fairing was removed during skid repairs and not replaced.

One note; the removal of the heavy telephone batteries was never specifically addressed in any of the weight and balance computations by Donald Hall.

[W.J.Langholz]

George

Not that I don't appreciate your very informative post.............I still miss Bluelder ..........maybe we could all chip in and get him a laptop with a wireless data card .......we could call it and early birthday gift


W.

[blueldr]

Greetings! It is I, the blueldr! I have returned, so to speak. My sojourn to the delights of Yellow Pine,ID, was interruped by a medical problem that gave me considerable concern until I was able to consult with my physician yesterday. Apparently I have been afflicted ith "BPPV", Vertigo. Scared hell out of me.

Anyway, I seem to remember those remote compass insallations from back in the "Big War". You simply set the "Bug" and then kept the needle centered between the parallel lines. Easier than trying to keep the point of the needle on a number other than a prime one, and it was stable in comparison to a wet compass. One of the principal avantages of the system was the ability to install the transmitter in a location, such as a wing tip, that was least affected by aircraft items that produced deviation requiring correction.

P.S. No laptops, thank you.

[GAHorn]

Greetings! It is I, the blueldr! ...P.S. No laptops, thank you.

Whatsamatter? No "Fast Erect" provision with them?

[blueldr]

Now that George has brought up the mention of "erection", if I thought that a laptop could possibly have any "magical" powers, you can bet your sweet ass I'd have the biggest and most expensive one I could afford. Oh my! Think about the "Email" accounts one could develope.

[GAHorn]

I once occupied one of the pilot's seats of a commuter airliner in which someone had scribbled a note to subsequent operators adjacent to the Horizon: "Warning: Slow to Erect on Fast Turn-Arounds."

About a week later, someone else had scribbled a post-script: "Who Isn't?"