Anyone flown atn LPV yet?

"Sam Spade" wrote in message ...
Ron Rosenfeld wrote:




I've not noted a "step change" in my CNX80. The changes in sensitivity are
supposed to be gradual, and at the FAF I believe the "scaling" goes to
angular, to mimic an ILS. But maybe I've just missed it.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

As I understand it, it first ramps down to 0.3 from 1.0 starting at 2
miles from the LPV FAF, then it does a continuous angular "ramp down"
from the FAF to the runway so it will be ILS-like close in. Have you
noted that doing small incremental "stepping" on an LPV IAP during final
approach?

You say LPV course widths ramp down gradually over some miles?
Should LNAV/VNAV approaches do the same?
Around the FAF, it's usually too busy a time to collect every detail.
If it's not a step change in course width, it seems at least pretty quick.
Quick enough to disturb my autopilot a small amount, it seems.
But the reason I asked was to learn if other CNX80 users see a similar effect.
So far, the answer seems to be "no".
The effect I see is small, though, so it could be ignored easily.

If the blame turns out to be on my autopilot, I could send it back
to Collins to get it re-calibrated.

John R. Copeland wrote:


You say LPV course widths ramp down gradually over some miles?
Should LNAV/VNAV approaches do the same?

RNAV IAPs, other than LPV, ramp down from 1.0 miles to 0.3 miles
starting two miles prior to the FAF, and completed at the FAF. Then,
the sensitivity remains at 0.3 throughout the final approach segment.

With LPV, the sensitivity continues to increase (course width decreases)
from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.

"Sam Spade" wrote in message ...

With LPV, the sensitivity continues to increase (course width decreases)
from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.

Thanks. I didn't know of the difference. I'll watch for it.

John R. Copeland wrote:

"Sam Spade" wrote in message ...

With LPV, the sensitivity continues to increase (course width decreases)
from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.

I getting up to speed on the 145/146 spec. The LNAV approach also
reduces in the lateral mode similar to the laternal mode of the LPV
approach. When you reach the MAP, it is only 350 feet full scale
deflection, instead of the 0.3 mile defection for TSO 129 LNAV final.

"Sam Spade" wrote in message
...
John R. Copeland wrote:

"Sam Spade" wrote in message
...

With LPV, the sensitivity continues to increase (course width decreases)
from the FAF to the runway. That causes LPV to be an angular system from
the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.

I getting up to speed on the 145/146 spec. The LNAV approach also reduces
in the lateral mode similar to the laternal mode of the LPV approach.
When you reach the MAP, it is only 350 feet full scale deflection, instead
of the 0.3 mile defection for TSO 129 LNAV final.

Do you have a link to the TSO handy? And is it the full requirement? Last
time I tried to read TSO C129, seems like it was a skeleton document,
referencing a commercial spec that had to be purchased.

Stan Prevost wrote:

"Sam Spade" wrote in message
...

John R. Copeland wrote:


"Sam Spade" wrote in message
...


With LPV, the sensitivity continues to increase (course width decreases)

from the FAF to the runway. That causes LPV to be an angular system from

the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.


I getting up to speed on the 145/146 spec. The LNAV approach also reduces
in the lateral mode similar to the laternal mode of the LPV approach.
When you reach the MAP, it is only 350 feet full scale deflection, instead
of the 0.3 mile defection for TSO 129 LNAV final.


Do you have a link to the TSO handy? And is it the full requirement? Last
time I tried to read TSO C129, seems like it was a skeleton document,
referencing a commercial spec that had to be purchased.



Same with 145/146. The nuts-and-boths is in RTCA Doument 229C. $350.

"Sam Spade" wrote in message ...
John R. Copeland wrote:

"Sam Spade" wrote in message ...

With LPV, the sensitivity continues to increase (course width decreases)
from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.

I getting up to speed on the 145/146 spec. The LNAV approach also
reduces in the lateral mode similar to the laternal mode of the LPV
approach. When you reach the MAP, it is only 350 feet full scale
deflection, instead of the 0.3 mile defection for TSO 129 LNAV final.

I'm definitely gonna have to set up an experiment over that!
I'd expect to have noticed it, if my CNX80 behaved that way.
Is that a behavior demanded by TSO-C145/146, or merely allowed?

John R. Copeland wrote:

"Sam Spade" wrote in message ...

John R. Copeland wrote:


"Sam Spade" wrote in message ...


With LPV, the sensitivity continues to increase (course width decreases)

from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.


I getting up to speed on the 145/146 spec. The LNAV approach also
reduces in the lateral mode similar to the laternal mode of the LPV
approach. When you reach the MAP, it is only 350 feet full scale
deflection, instead of the 0.3 mile defection for TSO 129 LNAV final.


I'm definitely gonna have to set up an experiment over that!
I'd expect to have noticed it, if my CNX80 behaved that way.
Is that a behavior demanded by TSO-C145/146, or merely allowed?


Stay tuned.

John R. Copeland wrote:
"Sam Spade" wrote in message ...

John R. Copeland wrote:


"Sam Spade" wrote in message ...


With LPV, the sensitivity continues to increase (course width decreases)

from the FAF to the runway. That causes LPV to be an angular system
from the FAF to the runway. Not so with other RNAV.


Thanks. I didn't know of the difference. I'll watch for it.


I getting up to speed on the 145/146 spec. The LNAV approach also
reduces in the lateral mode similar to the laternal mode of the LPV
approach. When you reach the MAP, it is only 350 feet full scale
deflection, instead of the 0.3 mile defection for TSO 129 LNAV final.


I'm definitely gonna have to set up an experiment over that!
I'd expect to have noticed it, if my CNX80 behaved that way.
Is that a behavior demanded by TSO-C145/146, or merely allowed?


The following language suggests that LNAV must always be 350 feet at the
MAP. Both Figures 2-12 and 2-13 show 350 at the MAP.

2.2.3.3.1 Approach Path Definition

If the pilot has not selected a VTF approach, deviations shall be
provided with respect to the active leg of the approach procedure. See
Figure 2-12. If the pilot has selected a VTF approach, deviations shall
be provided relative to the inbound course to the FAF. See Figure 2-13.
The active waypoint shall initially be the FAWP. The equipment should
also account for short turns onto the final approach where the FAWP may
not be crossed.

Note 1: A VTF approach can be selected at any time.