Glareshield mounted compass?

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

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

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

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

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.

How about inside a bumpy Cumulus cloud?

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.

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