Glareshield mounted compass?

[Echo]

Anyone have any experience modifying the glareshield for a partially embedded compass? I have a brand new airpath panel mount, but would like the panel space for a transponder, flarm, something more productive. Ideally would prefer to swap my airpath for something I could mount somehow half set into the glareshield, then line the whole game with black felt. Thoughts?

Jordan
ASW20 E

[Dan Marotta]

Use aluminum or fiberglass, not any steel in your fabrication.


"Echo" > wrote in message
...
Anyone have any experience modifying the glareshield for a partially
embedded compass? I have a brand new airpath panel mount, but would like
the panel space for a transponder, flarm, something more productive.
Ideally would prefer to swap my airpath for something I could mount somehow
half set into the glareshield, then line the whole game with black felt.
Thoughts?

Jordan
ASW20 E

[Steve Koerner]

Given that you are going to install a magnetic compass, the best place for it is behind the seat back so that it is completely out of the way of your forward view.

[mike]

On Sunday, March 9, 2014 9:46:46 AM UTC-6, Dan Marotta wrote:
> Use aluminum or fiberglass, not any steel in your fabrication.
>
>
>
>
>
> "Echo" > wrote in message
>
> ...
>
> Anyone have any experience modifying the glareshield for a partially
>
> embedded compass? I have a brand new airpath panel mount, but would like
>
> the panel space for a transponder, flarm, something more productive.
>
> Ideally would prefer to swap my airpath for something I could mount somehow
>
> half set into the glareshield, then line the whole game with black felt.
>
> Thoughts?
>
>
>
> Jordan
>
> ASW20 E

Black felt will stop some glare on the glare shield, so does flat black paint. I have a pedestal mount compass towards the front of the glare shield in my Mini Nimbus, and it works well.

[son_of_flubber]

If you need magnetic shielding and you want to save a few bucks, scavenge the sheet metal case of an old harddrive. It has a nickel rich alloy that blocks magnetic fields generated by your DC power and vario step motors etc... Put the shield around the offending item, or between the item and the compass. Aircraft Spruce also sells unblemished sheets of the this material.

[kirk.stant]

I'm totally with Steve Koerner on this one - Sticking a useless piece of 18th century hardware on the glareshield where it obstructs the field of view forward is ridiculous and potentially dangerous.

Seriously, have you EVER navigated using your mag compass as the primary nav instrument?

In my LS6, a compass on the glareshield will completely block my view of the towplane when in normal high tow. It was the first thing I pitched when I got the glider. I replaced it (to keep the A&Ps happy) with a small PZL ball compass tucked in a corner of the instrument panel. It has now been moved due to the mounting of a PFlarm butterfly display in it's prized bit of panel real estate, and will be relocated in the shade behind my Oudie; so when the end of the world happens and all the GPS satellites fall out of the sky I can still pretend to navigate (until the earth's magnetic field switches again - it's due).

Another good place to put it is in the side map pocket - then you can pull it out and admire it when needed. Very retro, and all...

Kirk
66

[[email protected]]

Do like the MD-80 does:

Standby compass is behind the pilots. When all hell breaks loose, and you need to navigate via this compass, you flip up a little mirror on top of the glare shield and it reflects/mirrors the compass behind you.. You can't believe it till you see it.

Yes, the FAA approved this for use, especially in an emergency...

That's why I fly Boeing!

[son_of_flubber]

On Sunday, March 9, 2014 6:47:24 PM UTC-4, kirk.stant wrote:

> Another good place to put it is in the side map pocket

I have my backup backup compass back behind the seat back in my landout kit. A compass is the best tool if you ever need to bushwhack in dense woods.

[Echo]

It's part of my manufacturer issued type certificate as well as a part 91 reg. As a professional pilot, I just assume not hang my livelihood out there with some hokie backup compass. That being said, I agree that it's useless with the exception of a very few scenarios. I do love the DC9 series compass. So much swing error that it has to be mounted on the aft cockpit bulkhead. Seen it many times. Awesome. Incredible that thing was designed looking at slide rules through thick glasses before we even engineered the Lunar Lander. What a TANK.

Jordan
E

[Paul Remde]

Hi,

We installed a PAI-700 vertical card compass far forward in our DG-1000.
There was a recess near the front of the instrument panel cover that must
have been designed for some sort of compass that was no longer in the plane.
The vertical card compass mounted perfectly and is partially recessed. It
fit using the existing mounting holes. We can see about 1/2 to 2/3 of the
top of the compass. That is plenty to use it easily. It looks good and
works well and doesn't block vision nearly as much as it would if it were
mounted using an L-bracket on top of the instrument panel cover. I don't
have any photos of the installation handy, but I can take one in a few weeks
if that would help. It is this compass.
http://www.cumulus-soaring.com/precision.htm

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
______________________________________

"Echo" wrote in message
...

Anyone have any experience modifying the glareshield for a partially
embedded compass? I have a brand new airpath panel mount, but would like
the panel space for a transponder, flarm, something more productive.
Ideally would prefer to swap my airpath for something I could mount somehow
half set into the glareshield, then line the whole game with black felt.
Thoughts?

Jordan
ASW20 E

[kirk.stant]

On Thursday, March 13, 2014 1:04:03 AM UTC-5, Echo wrote:
> It's part of my manufacturer issued type certificate as well as a part 91 reg. As a professional pilot, I just assume not hang my livelihood out there with some hokie backup compass. That being said, I agree that it's useless with the exception of a very few scenarios.

Understood - which is why I still have an aviation compass in my cockpit - but I refuse to be less safe (reduced visibility) to satisfy some bogus FAR requirement. So I found the smallest certified aircraft compass (the little PZL KI-13A) that I could mount in an inconspicuous location on my panel.

Sometimes, it's the little things in life...

Kirk
66

[Brian[_1_]]

On Thursday, March 13, 2014 12:04:03 AM UTC-6, Echo wrote:
> It's part of my manufacturer issued type certificate as well as a part 91 reg. As a professional pilot, I just assume not hang my livelihood out there with some hokie backup compass. That being said, I agree that it's useless with the exception of a very few scenarios. I do love the DC9 series compass. So much swing error that it has to be mounted on the aft cockpit bulkhead. Seen it many times. Awesome. Incredible that thing was designed looking at slide rules through thick glasses before we even engineered the Lunar Lander. What a TANK.
>
>
>
> Jordan
>
> E

I agree with that you must comply with the manufacturers type certificate, but I can't seem to the find any part 91 regs that require one for glider?

Brian

[Echo]

Glider=aircraft unless the SSA pulled a waiver from the FAA for that too...

[Mike Koerner]

I think some of you are underestimating the potential value of a magnetic compass when properly used. If you can't see out the window any more, holding a southerly heading (in the northern hemisphere) may keep your wings attached long enough for you to get to where you can see out again... assuming you don't reach the ground first.
On a southerly heading the compass can help you avoid a spiral dive by indicating turns - even without a gyro. Instead of "Needle, ball, airspeed..." the scan becomes "Compass, yaw string, airspeed..."
The southerly heading is critical as it avoids the northerly turning error and acceleration errors associated with the use of a magnetic compass on other headings.
In the southern hemisphere you head north instead.
Of course, if you have a GPS with a moving map display... and the light is still on... you can do the same thing by keeping the track straight - in any direction (it doesn't have any compass errors).
I consider a compass cheap, reliable insurance. I wouldn't fly without one.
Mike Koerner

[Echo]

Most people here also didn't get any partial panel instrument training either. I'm not sure I agree about southern only heading. Lead/lag errors are the only issues that apply to the compass when associated with non-east/west headings. If turning towarda northern heading you'd overshoot the compass heading and undershoot the rollout to a southern heading. Either way it won't be accurate in the short term. Are you thinking just due to the physics of a compass that it's more likely to be stable and leas prone to swinging if the magnetic pull is behind the gauge? I don't think that would make a difference. It's been a while since my most active CFII days, so I could be missing something...

E

[Mike Koerner]

In the northern hemisphere, when turning from a northerly heading, a magnetic compass will lag behind the turn (or even initially start to turn in the opposite direction). It would be difficult to effectively use that that information to maintain wings-level flight.
In turning from a southerly heading, on the other hand, the compass will lead the turn - exaggerating the amount you've turned. Since you are trying to avoid turns altogether, lead is not at all bad. You just need to respond with appropriate restraint to avoid excessive roll oscillations.
On an easterly or westerly heading, the acceleration error swings the compass toward the north as you speed up and toward the south when you slow down.. To the degree you only look at the compass when you are flying straight and level, it works fine. But as things start to go haywire, speed corrections are going to play havoc with your ability to keep the wings level.
In between headings present an amalgamation of these errors.
So if all you have is a magnetic compass, airspeed indicator and ball (or yaw string)... head south. That's what I was taught. I admit, I haven't practiced this teaching, or (fortunately) had the need to implement it, but it seems to make sense anyway.
This assumes that you are not trying to navigate to some specific heading. Whether you roll out on the right heading or not is not the issue. In this case you're just trying to maintain a heading to keep the wings level (and attached) until you get back into VMC. Other options are a benign spiral or induced spin.
Mike Koerner

[Echo]

Ah yes, thanks. Been close to 7 years since I was an active CFI-I. BUT...when I used to teach a lot of partial panel, we'd do a demo of the turn coordinator failing during a partial panel scenario...never went well. Point being, most guys would mess themselves up and pull their wings off before a mag compass will get them out of the clouds successfully. Only a very few with RECENT practice in IFR partial panel training would have a chance. There's a reason why I and most other CFIG teach the benign spiral. Simple and effective.

E

[Dan Marotta]

I recall a warning somewhere in the Dash-1 that went something like,
"WARNING - Instrument flight with the magnetic compass is an emergency
procedure." My partial panel practice always included a working needle and
ball.


"Echo" > wrote in message
...
Ah yes, thanks. Been close to 7 years since I was an active CFI-I.
BUT...when I used to teach a lot of partial panel, we'd do a demo of the
turn coordinator failing during a partial panel scenario...never went well.
Point being, most guys would mess themselves up and pull their wings off
before a mag compass will get them out of the clouds successfully. Only a
very few with RECENT practice in IFR partial panel training would have a
chance. There's a reason why I and most other CFIG teach the benign spiral.
Simple and effective.

E

[Bill D]

On Friday, March 21, 2014 10:04:16 PM UTC-6, Mike Koerner wrote:
> In the northern hemisphere, when turning from a northerly heading, a magnetic compass will lag behind the turn (or even initially start to turn in the opposite direction). It would be difficult to effectively use that that information to maintain wings-level flight.
>
> In turning from a southerly heading, on the other hand, the compass will lead the turn - exaggerating the amount you've turned. Since you are trying to avoid turns altogether, lead is not at all bad. You just need to respond with appropriate restraint to avoid excessive roll oscillations.
>
> On an easterly or westerly heading, the acceleration error swings the compass toward the north as you speed up and toward the south when you slow down. To the degree you only look at the compass when you are flying straight and level, it works fine. But as things start to go haywire, speed corrections are going to play havoc with your ability to keep the wings level.
>
> In between headings present an amalgamation of these errors.
>
> So if all you have is a magnetic compass, airspeed indicator and ball (or yaw string)... head south. That's what I was taught. I admit, I haven't practiced this teaching, or (fortunately) had the need to implement it, but it seems to make sense anyway.
>
> This assumes that you are not trying to navigate to some specific heading.. Whether you roll out on the right heading or not is not the issue. In this case you're just trying to maintain a heading to keep the wings level (and attached) until you get back into VMC. Other options are a benign spiral or induced spin.
>
> Mike Koerner

I actually tried this from the back seat of a G103 while wearing "Foggles" to restrict my view to the panel. With a safety pilot in the front seat watching for traffic I found it surprisingly easy to maintain a wings-level southerly course. However, I do have an instrument rating with a lot of partial panel practice. Although I will do everything I can to avoid the necessity of using the trick for real in cloud, I think it might work.

[Greg Delp]

How about inside a bumpy Cumulus cloud?

[Bill D]

On Saturday, March 22, 2014 5:14:57 PM UTC-6, Greg Delp wrote:
> How about inside a bumpy Cumulus cloud?

The idea of using the magnetic compass "Northerly Turning Error" as an emergency letdown procedure has appeared in instrument flying books for the last 75 years - accompanied by the statement that it probably wouldn't work in a real emergency. It's used to help students understand one of the many compass errors.

A wet compass itself doesn't really work well in bumpy air. As one poster wrote, magnetic compasses are probably the most useless instrument found in gliders. GPS ground track is much more useful - and accurate.

Flying slow light airplanes under instrument rules, I found controllers aren't always well versed in the difference between track and heading. With fast jets, there isn't much difference. I found the controllers were much happier when I flew a GPS ground track instead of the "heading" in my clearance.