more bitching about the IFR written - CDI left/right versus north/south/etc

On Fri, 7 Jan 2005 07:51:51 -0800, "C J Campbell"
wrote:

The information on the OBS, combined with the information from the
CDI, augmented by information from the DG, tells you, at a single
glance:


Yes, it tells me something, but what does it mean to the CDI? You said your
wording was deliberate and specific.


Quite the contrary, I said that when I use words, they mean just what
I want them to mean, nothing more and nothing less.

That way I don't get involved in bull**** semantic wordgames.

Adios.

Great article. I read it a while back and ....... *poof*.... it all made
sense.
Thanks!

"Andrew Sarangan" wrote in message
1...
No, it is not just a reminder, it is a tremendous aid in interpretation.
Reverse sensing is all in your head. The aircraft or the CDI does not
know reverse sensing. Read this article:
http://131.238.38.204/~sarangan/avia...or-article.pdf





Andrew Gideon wrote in
online.com:

wrote:

If the OBS is set to the course, you can immediately discern whether
you are north or south of an eastbound course, for example. You can
do this by looking at a properly set OBS ring, and at which way the
needle is leaning.

Setting the OBS during a localizer approach is a good mnemonic. I do
that. It's also a good habit.

But it doesn't really impact *interpretation* of the CDI's display
(unless one forgets the course marked by the localizer, in which case
the OBS setting saves having to look down at the plate).

Using your example, the OBS doesn't do anything but remind you that
the course indicated by the localizer is eastbound. Useful, true, but
I'd not consider that a part of the interpretation process. I make
this distinction because, unless I forget the course, I never need to
look at the OBS to discern the meaning of the CDI.

- Andrew

wrote in message
news
On Fri, 7 Jan 2005 07:51:51 -0800, "C J Campbell"
wrote:

The information on the OBS, combined with the information from the
CDI, augmented by information from the DG, tells you, at a single
glance:


Yes, it tells me something, but what does it mean to the CDI? You said
your
wording was deliberate and specific.


Quite the contrary, I said that when I use words, they mean just what
I want them to mean, nothing more and nothing less.

Well, if I misunderstood what you said, I am indeed sorry. OTOH, it is not
just semantic word games. Students tend to take what their instructors say
quite literally.

When you are being vectored (or intercepting from
a PT), how do you tell whether you have blasted through the course, or
still heading towards it?

Do to this, I do have to use more interpretation and I extract enough
heading information to tell me. (All I need to know is "yes/no"). My
mental process is to mentally rotate the airplane to point towards the
runway; this tells me which side I'm on, and then when I mentally
unrotate the airplane, this tells me whether it's the side I want or
not. This does not take me several miles, and is acutally quite
natural when intercepting from a PT, where I'm primarily using the
compass to accomplish the turn anyway (I use the 80-260 method).

Some fixes on approaches are defined by a VOR cross radial. How
do you know whether you have passed that fix or still heading towards
it?

When the OBS is set to the radial, the needle points towards the radio
station until passage, then it points away. On my chart (which I hold
or can orient track up) I can see where the station is. Drop dead
simple. This is easily visualized by mentally flying away from the
station.

Jose
--
Money: What you need when you run out of brains.
for Email, make the obvious change in the address.

"Jose" wrote in message
m...
When you are being vectored (or intercepting from a PT), how do you tell
whether you have blasted through the course, or still heading towards it?

Do to this, I do have to use more interpretation and I extract enough
heading information to tell me. (All I need to know is "yes/no"). My
mental process is to mentally rotate the airplane to point towards the
runway; this tells me which side I'm on, and then when I mentally unrotate
the airplane, this tells me whether it's the side I want or not. This
does not take me several miles, and is acutally quite natural when
intercepting from a PT, where I'm primarily using the compass to
accomplish the turn anyway (I use the 80-260 method).

Some fixes on approaches are defined by a VOR cross radial. How do you
know whether you have passed that fix or still heading towards it?

When the OBS is set to the radial, the needle points towards the radio
station until passage, then it points away. On my chart (which I hold or
can orient track up) I can see where the station is. Drop dead simple.
This is easily visualized by mentally flying away from the station.


All this mental rotation of the aircraft and figuring out position is
completely unnecessary. All you have to do is glance at the CDI and see if
your heading is on the same side as the needle. If it is, you are still
headed toward the radial, you have not passed it. If not, you have passed
through it. Doesn't matter whether the radial number is set at the top or
bottom of the dial, it still works exactly the same way.

For a localizer, set the OBS to the inbound course at the top and you
interpret it exactly the same way, whether on the front course or the back
course. For GPS, set the OBS to DTK and it is exactly the same.

"C J Campbell" wrote in
:


"Andrew Sarangan" wrote in message
1...
There are a whole bunch of useless questions that you just have to
get through. Like the one where you have to pick which aircraft
corresponds to the given CDI indications. Who cares where the
aircraft is. You will no longer be there by the time you blink.

Are you saying that the aircraft moves from one quadrant to the other
in the blink of an eye?




No, what I am saying is, it is more important to turn to the correct
heading than to figure out where you are right now, because by the time you
figure out where you are, you will not be there anymore. The FAA exams
would lead one to think that it is more important to know where you are
now. None of the questions ask 'which heading should the aircraft turn to'.
Instead they dwell on 'where is the aircraft now'.

All this mental rotation of the aircraft and figuring out position is
completely unnecessary.

I don't need to do it, I just used it for illustration. Needle points
to the station, you're not there yet.

All you have to do is glance at the CDI and see if
your heading is on the same side as the needle. If it is, you are still
headed toward the radial, you have not passed it. If not, you have passed
through it. Doesn't matter whether the radial number is set at the top or
bottom of the dial, it still works exactly the same way.

Also nice.

For a localizer, set the OBS to the inbound course at the top and you
interpret it exactly the same way, whether on the front course or the back
course.

Nice for symmetry, but "a little left" is quicker than finding the
course on the dial for comparison, though it does make the back course
"not special".

Jose
--
Money: What you need when you run out of brains.
for Email, make the obvious change in the address.

If you have to fly to an intersection with both CDI at full scale
deflection, how would you get there? The left/right method will not help
you here, but it is trivial with the heading technique.




Jose wrote in
:

All this mental rotation of the aircraft and figuring out position is
completely unnecessary.

I don't need to do it, I just used it for illustration. Needle points
to the station, you're not there yet.

All you have to do is glance at the CDI and see if
your heading is on the same side as the needle. If it is, you are
still headed toward the radial, you have not passed it. If not, you
have passed through it. Doesn't matter whether the radial number is
set at the top or bottom of the dial, it still works exactly the same
way.

Also nice.

For a localizer, set the OBS to the inbound course at the top and you
interpret it exactly the same way, whether on the front course or the
back course.

Nice for symmetry, but "a little left" is quicker than finding the
course on the dial for comparison, though it does make the back course
"not special".

Jose

If you have to fly to an intersection with both CDI at full scale
deflection, how would you get there? The left/right method will not help
you here, but it is trivial with the heading technique.

That is correct. If I ever need to do this, I would not use the
left/right technique. I'd do the extra steps needed to figure out
which way I needed to go, and I'd expect that I'd intersect one of the
radials before the other (i.e. I'd not end up flying direct to the
intersection)

I don't think one can guarantee a direct ground track if both CDIs are
at full deflection and you need to head directly towards an
intersection. (at least not without fiddling with the OBS to see
where you really are).

How would you fly directly towards an intersection, with both CDIs
pegged, and no fiddling with the OBS? (fiddle with the OBS and you've
unpegged the CDI and now know what radial you're on)

Jose
--
Money: What you need when you run out of brains.
for Email, make the obvious change in the address.

You are correct that it is impossible to fly direct to the intersection.
But you can take a heading that will intercept one of the two radials, and
then you fly along that radial to intersection. I realize this can be done
with the left/right technique also, but it requires a lot of mind numbming
visualizations. It is really trivial the other way.


Jose wrote in
om:

If you have to fly to an intersection with both CDI at full scale
deflection, how would you get there? The left/right method will not
help you here, but it is trivial with the heading technique.

That is correct. If I ever need to do this, I would not use the
left/right technique. I'd do the extra steps needed to figure out
which way I needed to go, and I'd expect that I'd intersect one of the
radials before the other (i.e. I'd not end up flying direct to the
intersection)

I don't think one can guarantee a direct ground track if both CDIs are
at full deflection and you need to head directly towards an
intersection. (at least not without fiddling with the OBS to see
where you really are).

How would you fly directly towards an intersection, with both CDIs
pegged, and no fiddling with the OBS? (fiddle with the OBS and you've
unpegged the CDI and now know what radial you're on)

Jose