Compass selection

[skippydiesel]

Back again seeking your input.

 

Despite going all digital, I would like to have a "whiskey" compass  in/on my panel.

 

This may actually be a legal requirement but in any case this will give the old boy at least one instrument he recognises straight away.

 

Just returned from Googling what, non TSO'd units, are available in Australia -  quit a lot; vertical cards, in panel, on top of panel, etc

 

I would be interested in your recommendations (remember day VFR only)

[Old Koreelah]

I believe it’s a legal requirement. I rarely glanced at mine for years due to it’s wild inaccuracy. Then i finally got around to doing a proper compass swing (actually following instructions) and now it’s accurate. 

Well worth doing properly, because modern tech will fail when you need it most.

[skippydiesel]

On 14/12/2021 at 9:00 AM, Old Koreelah said:

I believe it’s a legal requirement. I rarely glanced at mine for years due to it’s wild inaccuracy. Then i finally got around to doing a proper compass swing (actually following instructions) and now it’s accurate. 

Well worth doing properly, because modern tech will fail when you need it most.

Could do with a recommendation (Brand/Model/Supplier)

[Old Koreelah]

Skippy I can’t help there; mine looks like this one:

https://www.skyshop.com.au/shopdisplayproducts.asp?id=244&cat=compasses

 

…but some people prefer this style:

https://www.aircraftspruce.com/catalog/inpages/vertcard_compass3.php

 

There’s mobs of interesting vids on compass use, like this one:

 

[skippydiesel]

Thanks again OK - the very references (& others) you gave are the ones causing me grief.

 

I really would like to get some pros/cons and recommendations - make/model/supplier and mounting location.

 

If it helps - the compass will be mounted in an all metal aircraft (Sonex) either in or above the panel ( dont think there are other location (could be wrong). The panel contains a heap of electronic wizardry (potential  interference) that the compass must somehow cope with.

[RossK]

Here's our panel mounted one, I have no idea of the make etc, looks like the Airpath.

Seems to point north when i'm lined up on 36 at YLIL.

[skippydiesel]

Thanks RossK - How old ? and any complaints? and is it about 50mm?

[peter]

An excellent topic. I tried a small boat compass suspended from the windscreen frame on the Onex - useless.

Flying day VFR what do you need? Mobile phone - mine has a built in compass, hand held garmin etrex has built in compass (which has proved accurate from the arctic to the antarctic). Who actually flies off the compass which has huge errors (deviation), points to the magnetic pole and has locality/area errors ( variation). If to be used seriously would need to be swung for all headings at different RPM and a deviation card produced, just not worth the effort for day VFR.

Peter

PS good luck with the Sonex, the whole range are fun to fly!

[Old Koreelah]

1 hour ago, peter said:

Who actually flies off the compass which has huge errors (deviation), points to the magnetic pole and has locality/area errors ( variation). If to be used seriously would need to be swung for all headings at different RPM and a deviation card produced, just not worth the effort for day VFR.

 

Peter that used to be my attitude, until my iPad failed me on a trip. Luckily I had landmarks to follow, but that experience convinced me to do a proper compass swing. It only took half an hour and in flight testing for the last year has shown it accurate to within a couple of degrees all around the dial.

[skippydiesel]

Sorry Peter - outvoted. I do regular checks across my electronic (GPS based) devises against my compass. Something reassuring about everything agreeing with a degree or so.

[Old Koreelah]

Relevant:

[RossK]

20 hours ago, skippydiesel said:

Thanks RossK - How old ? and any complaints? and is it about 50mm?

Skip, it's the 57mm one, unsure of manufacturer though.

age, 14 years according to the maintenance logs - ie it's the original one fitted.

 

I check it as part of my pre-flight routine during taxi and line up. 

Only used it once during flight to verify that the Aspen PFD was having a bad day, once. It confirmed that the Aspen was telling me lies.

But I also have an Ipad, a Garmin 296 and my mobile in the plane, so plenty of redundancy.

Edited December 16, 2021 by RossK

[Geoff_H]

A little off track of this conversation but I have a bottle ( one litre I think) of compass oil free to a good home.  

[skippydiesel]

Starting to narrow the field - its got to be a pedestal mount compass - on the small side (its a back up so no need for big dial) - may have to be fixed to the canopy forward bow (so capable of being rotated in housing/pedestal to correct orientation)
 

[Old Koreelah]

15 hours ago, Geoff_H said:

A little off track of this conversation but I have a bottle ( one litre I think) of compass oil free to a good home.  

Crickey Geoff, that would fill a lot of aeroplane compasses- or was it purchased for one of those ginormous ship’s binacles?

 

12 hours ago, skippydiesel said:

Starting to narrow the field - its got to be a pedestal mount compass - on the small side (its a back up so no need for big dial) - may have to be fixed to the canopy forward bow (so capable of being rotated in housing/pedestal to correct orientation)

My panel is plywood, with brass screws only in the vicinity of the compass. Even a tiny steel fastener can affect the accuracy.

[Geoff_H]

I know, I needed a very small amount for rebuilding a compass.  That was the only size available in WA at the time.  Seems a waste to just throw it away.  

[Bruce Tuncks]

I have actually used a magnetic compass for real. Sometimes on a good gliding day, the cu's have a dome and the lift is great up there but you have then to fly under the cloud or through the cloud to move on. If through the cloud, then you have a few seconds of blind flying. the old magnetic compass was the thing you used to head off on the right bearing, and the ASI and the turn-and -bank helped too.

[turboplanner]

On 15/12/2021 at 5:56 PM, peter said:

An excellent topic. I tried a small boat compass suspended from the windscreen frame on the Onex - useless.

Flying day VFR what do you need? Mobile phone - mine has a built in compass, hand held garmin etrex has built in compass (which has proved accurate from the arctic to the antarctic). Who actually flies off the compass which has huge errors (deviation), points to the magnetic pole and has locality/area errors ( variation). If to be used seriously would need to be swung for all headings at different RPM and a deviation card produced, just not worth the effort for day VFR.

Peter

PS good luck with the Sonex, the whole range are fun to fly!

For day VFR a GA Pilot will set the DG (Directional Gyro) in pre takeoff checks, and that will gove rock steady readings suitable for navigation. The DG is affected by precession, so will be reset from time to time when there's a quiet moment. For flight planning tracks are converted from True to Magnetic on the ground before the fight starts, and become part of your reference material for the flight.