Flying IFR with Garmins

"Michael 182" wrote in message
newsDtBc.126215$3x.55034@attbi_s54...
Sounds like you have a Cessna 300A.

A Century 31. It's a good autopilot and flies smoothly even with
a fair amount of turbulence, and holds altitude to within a few feet.
But its nav following isn't great. I think it could be fixed with
some tweaking, but I've given the avionics shop enough of
my money as it is, and it isn't a practical problem.

John


Michael


"John Harper" wrote in message
news:1087790958.150362@sj-nntpcache-5...
I agree that this is a great technique. In fact I never use NAV mode on
my autopilot, I just tweak the heading until the track matches what it
should
be (and keep an eye on it obviously). Much better than the autopilot
zigzagging its way down the airways.

"Ron Rosenfeld" wrote in message
...

As recommended by STEC, I use the APR mode for tracking a GPS course.

That could get entertaining if you pick up a glide slope while
you're at altitude....

There is another way to do this with the Garmin. Suppose
you're on V123 sector between the A and B VORs,
and you have to turn onto V345 at an unnamed intersection
between the X and Y VORs. Enter the flightplan
A-B-X-Y. It will look funny on the display, but don't
worry about it. Start flying from A to B. When you
get fairly close to V345 (say five miles), go to the
flight plan page, cursor down to Y and hit
Direct-Direct-Enter. The GPS now thinks you're
trying to intercept V345. Fly current heading
until the CDI comes in, or even easier
hit HDG-NAV on the a/p and let the autopilot
fly the intercept.

Or you can just use the VORs - which is what
I do.

Would it be easier if the GPS could do this all
by itself? Sure. Would it be of the slightest
significance in the big scheme of things? I don't
think so.

John

"Andrew Gideon" wrote in message
online.com...
Michael 182 wrote:

You enter the one behind you and activate the leg you are intercepting.

This is about intercepting an airway at some point that's not a fix,
right?
In that case, you could "build" the airway segment with the fixes before
and after your intercept point or you could get "after" fix into the GPS
and then use OBS mode.

I have to admit, though, when given an airway intercept I find it easier
to
use a VOR receiver. The "user interface" seems to involve less work to me
(although the end result of the GPS process yields more benefit).

- Andrew

On Tue, 22 Jun 2004 12:15:06 -0700, "John Harper"
wrote:

That could get entertaining if you pick up a glide slope while
you're at altitude....

How would that happen?


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Not sure what you mean. The glide slope goes on for
ever, it doesn't stop at the outer marker. Given the
right runway and a powerful enough receiver, you could
pick it up on Pluto. (Voyager transmits on 2W or so).

So there you are at 15000' in APP mode and you
pick up a GS, whereupon the autopilot will start a
coupled approach and start you on down the glideslope.
My understanding is that the only difference between
APP and NAV modes is whether the GS coupling
is enabled. If the GS and dest waypoint happen to be in much
the same direction you could get a long way down...

Of course you'd spot this happening and recover (right?)
but still it would be an interesting moment.

John

"Ron Rosenfeld" wrote in message
...
On Tue, 22 Jun 2004 12:15:06 -0700, "John Harper"
wrote:

That could get entertaining if you pick up a glide slope while
you're at altitude....

How would that happen?


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

"John Harper" wrote:
..
My understanding is that the only difference between
APP and NAV modes is whether the GS coupling
is enabled.

Nope. On an S-TEC 50, the only difference between APP and NAV is the
degree of sensitivity to CDI deflection: APP is more sensitive. The 50
does not do VNAV; there's now way it could "pick up the glide slope."

In my airplane, I set the S-TEC 50 to APP and the KLN-90B GPS CDI output
to 1.0 mile. This setup keeps me on course with a cross track error of
50'.
--
Dan
C172RG at BFM

On Tue, 22 Jun 2004 14:20:18 -0700, "John Harper"
wrote:

Not sure what you mean. The glide slope goes on for
ever, it doesn't stop at the outer marker. Given the
right runway and a powerful enough receiver, you could
pick it up on Pluto. (Voyager transmits on 2W or so).

Yeah, but you have to have a receiver tuned to that frequency, don't you?
At least with the receivers I've used in light GA a/c, I've not picked up a
GS signal without tuning to the appropriate frequency.

You would also need to have the CDI in the GPS receiver set to output the
VOR/LOC signal, and not the GPS signal information.


So there you are at 15000' in APP mode and you
pick up a GS, whereupon the autopilot will start a
coupled approach and start you on down the glideslope.
My understanding is that the only difference between
APP and NAV modes is whether the GS coupling
is enabled.

With respect to the STEC50, your understanding is incorrect. The
difference has to do with sensitivity to the signal. And there is no GS
coupling with my STEC50.

If the GS and dest waypoint happen to be in much
the same direction you could get a long way down...


Do other GPS receivers allow you to navigate with both a GPS signal, and
some random GP signal that happens to be in the same direction? The CNX80
certainly does not.


Of course you'd spot this happening and recover (right?)
but still it would be an interesting moment.

I can't imagine a failure mode that would result in this scenario.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Hmm. Yep, I guess you're right. You'd have to be
tuned to an ILS for this to happen (even assuming
you have an a/p that does coupled approaches),
and have the GPS in VLOC mode (well I suppose
so, I haven't actually checked to see if the HSI
tracks the GS if you have the 530 tuned to an ILS
but in GPS mode, it would be odd if it did).

I guess I just had it drummed into me not to use APP
mode unless you really mean it, and this was the
rationale. I don't know if my a/p does anything
different in APP mode, other than GS tracking.
Certainly the GPS is more sensitive when you get
within 30 miles of the destination. And my a/p
works a lot better in that case for NAV tracking,
which is what makes me think it could be made
to work well in normal mode too.

John

"Ron Rosenfeld" wrote in message
...
On Tue, 22 Jun 2004 14:20:18 -0700, "John Harper"
wrote:

Not sure what you mean. The glide slope goes on for
ever, it doesn't stop at the outer marker. Given the
right runway and a powerful enough receiver, you could
pick it up on Pluto. (Voyager transmits on 2W or so).

Yeah, but you have to have a receiver tuned to that frequency, don't you?
At least with the receivers I've used in light GA a/c, I've not picked up
a
GS signal without tuning to the appropriate frequency.

You would also need to have the CDI in the GPS receiver set to output the
VOR/LOC signal, and not the GPS signal information.


So there you are at 15000' in APP mode and you
pick up a GS, whereupon the autopilot will start a
coupled approach and start you on down the glideslope.
My understanding is that the only difference between
APP and NAV modes is whether the GS coupling
is enabled.

With respect to the STEC50, your understanding is incorrect. The
difference has to do with sensitivity to the signal. And there is no GS
coupling with my STEC50.

If the GS and dest waypoint happen to be in much
the same direction you could get a long way down...


Do other GPS receivers allow you to navigate with both a GPS signal, and
some random GP signal that happens to be in the same direction? The CNX80
certainly does not.


Of course you'd spot this happening and recover (right?)
but still it would be an interesting moment.

I can't imagine a failure mode that would result in this scenario.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

On Tue, 22 Jun 2004 17:56:11 -0700, "John Harper"
wrote:

I guess I just had it drummed into me not to use APP
mode unless you really mean it, and this was the
rationale. I don't know if my a/p does anything
different in APP mode, other than GS tracking.
Certainly the GPS is more sensitive when you get
within 30 miles of the destination. And my a/p
works a lot better in that case for NAV tracking,
which is what makes me think it could be made
to work well in normal mode too.

Well, the reason I started using APP mode for tracking GPS was because that
was the recommendation of the a/p manufacturer! (Stec in this case). And,
being more sensitive, there is less course wandering. Since the signal is
more stable than a VOR signal, it made sense to me to follow the mfg
recommendation.

I never had the (mis)fortune of having someone drum into me anything about
using the a/p :-)




Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

If the 430 is in GPS mode, it won't output GS information.

Mike
MU-2


"John Harper" wrote in message
news:1087931861.386166@sj-nntpcache-3...

"Ron Rosenfeld" wrote in message
...

As recommended by STEC, I use the APR mode for tracking a GPS course.

That could get entertaining if you pick up a glide slope while
you're at altitude....