430/530 Back Course Question...

Here's one for U all. 530s.

Or as we learned in Melborne FL, home of the 27
Back Course LOC approach, all-y'all is the plural.

When selecting VLOC mode, the thing behaves correctly
on a BC approach... you set the ILS FRONT COURSE on the
yellow arrow HSI course datum, and inbound on the BC,
the tail of the arrow is up and there's no reverse sensing.
Just as we've been taught.

And there's no automatic switching to VLOC.

But while inbound on the GPS lead-in to the LOC, it
looked like the sensing was backwards at least in some
of the airplanes.

On the simulator, it looks like the GPS sensing was
also reversed so that while on "gps" tracking in the
vectors to final mode that the HSI read correctly--
while dialed to the front course heading--as it would
be in anticipation of the BC approach.

One customer asserted that they sensed the BC out of
the approach list and reversed everything--dial in the
BC inbound heading on the HSI. This did not make sense
as it would completly fake out the autopilot.

Anyone have the authoritative word on this?? Couldn't
find it in the Garmin documentation. Hadn't run into
the problem before. Versions?

I just told 'em to aim at it on the map.

Bill Hale BPPP

I don't know the answer to your specific question, but I can tell you
that all the GPS units that give right and left indications are
capable of "reverse sensing". It is inherent in the navigation system.

(Bill Hale) wrote in message . com...
Here's one for U all. 530s.

Or as we learned in Melborne FL, home of the 27
Back Course LOC approach, all-y'all is the plural.

When selecting VLOC mode, the thing behaves correctly
on a BC approach... you set the ILS FRONT COURSE on the
yellow arrow HSI course datum, and inbound on the BC,
the tail of the arrow is up and there's no reverse sensing.
Just as we've been taught.

And there's no automatic switching to VLOC.

But while inbound on the GPS lead-in to the LOC, it
looked like the sensing was backwards at least in some
of the airplanes.

On the simulator, it looks like the GPS sensing was
also reversed so that while on "gps" tracking in the
vectors to final mode that the HSI read correctly--
while dialed to the front course heading--as it would
be in anticipation of the BC approach.

One customer asserted that they sensed the BC out of
the approach list and reversed everything--dial in the
BC inbound heading on the HSI. This did not make sense
as it would completly fake out the autopilot.

Anyone have the authoritative word on this?? Couldn't
find it in the Garmin documentation. Hadn't run into
the problem before. Versions?

I just told 'em to aim at it on the map.

Bill Hale BPPP

On the simulator, it looks like the GPS sensing was
also reversed so that while on "gps" tracking in the
vectors to final mode that the HSI read correctly--
while dialed to the front course heading--as it would
be in anticipation of the BC approach.

I don't have a Garmin 530 but a KLN 94 and a King/Bendix HSI; however,
in any case it is important to distinguish between the GPS based
approaches and the actual ground navigation equipment based
approaches.

For example, I can select and load a LOC BC approach on my GPS (I get
a warning that this is for monitoring only since there are no LOC
based overlay approaches). If I were to fly this approach on the GPS,
i.e. have the information to the HSI coming from the GPS and "GPS" on
the HSI source annunciator, I would have to set the LOC front course
outbound or back course inbound on the HSI course bearing pointer.
That would give me correct sensing.

On the other hand, if I fly the BC LOC approach based on the NAV radio
(no GPS involved here), i.e. the information to the HSI coming from
the NAV source and "NAV" on the HSI source annunciator, I must set the
HSI course bearing pointer to the LOC front course inbound for correct
sensing.

I hope that's not too confusing and may answer your question.

Gerd (ATP since Monday)
T182 C-FDOW

A lot of students will load the BC approach on the 430 and forget t
switch to VLOC, attempting to fly the approach with the CDI in GP
mode. While on GPS navigation, the needle will behave normally, a
long as the dead of the HSI needle is set to the BACK course.
Remember, GPS navigation is capable of reverse sensing if the course i
set incorrectly. While the CDI is in GPS mode, the Desired Track i
the back course heading, and must be set this way in order to ge
normal sensing, since GPS navigation is "to-to" navigation. Th
problem arises when the pilot forgets to switch the CDI mode to VLO
before intercepting the back course. At this point, you must als
remember to flip the HSI needle around to the Front Course for norma
sensing
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