NDB approaches -- what are they good for?

On Mon, 07 Jul 2003 21:33:19 GMT, Sydney Hoeltzli wrote:
GPS approaches are very unit-specific and have a high initial
learning curve which involves way too much head-down time.
Maybe we should have a similar limitation on GPS approachs.

They do in Australia.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

"Dan Luke" wrote
What you are seeing are the death throes of an obsolescent technology. It's
not a pretty picture.

You mean like the taildragger? It's been obsolete for decades, but
10% of my total time is tailwheel time.

Due to bureaucratic wishy-washiness, the FAA won't go
ahead and put NDB/ADF out of its misery, preferring to let the condemned
twist slowly in the wind.

That's because at many airports (including my home field) the only
alternative is GPS - too expensive, and with a user interface not
ready for prime time.

Expert practitioners cling to their skills
because, well, they're experts.

No, becaue it's the only way they have to use many airports. Half my
actual approaches are NDB. My enthusiasm for spending a lot of time
and money and reducing the redundancy in my airplane (I would have to
remove either the ADF or LORAN to add an IFR GPS to my panel) is very
low. Thus I'm glad the FAA keeps the NDB approach alive.

So we are in the neither-here-nor-there limbo you describe. It's kind of
like the time when pocket calculators were replacing slide rules. The senior
engineer at Honeywell would snort when he saw the cubs using their TI's:
"What are you gonna do if that dam' toy quits on you?" It turned out not to
be a problem.

Actually, as a senior engineer at one of Honeywell's big competitors,
I can tell you that it IS a problem. Not the toy quitting, but the
absolute lack of understanding of certain concepts (most obviously
significant figures) in the new crop of engineers who were never
forced to master the slide rule. It's not that you CAN'T teach these
concepts without a slide rule - but with the calculators, you can get
by with not teaching them.

Meanwhile, look at your whizwheel and tell me slide rules are
obsolete.

Michael

"Michael" wrote:
What you are seeing are the death throes of an obsolescent technology.
It's
not a pretty picture.

You mean like the taildragger? It's been obsolete for decades, but
10% of my total time is tailwheel time.

Yes. The taildragger also still has certain operational advantages and
nostalgic appeal. But what does it hurt to keep taildraggers around as long
as people want to fly them?

...GPS - too expensive, and with a user interface not
ready for prime time.

That's what I meant by "death throes" and why it isn't pretty. The same
thing could have been said of word processors when they appeared.

Expert practitioners cling to their skills
because, well, they're experts.

No, becaue it's the only way they have to use many airports. Half my
actual approaches are NDB. My enthusiasm for spending a lot of time
and money and reducing the redundancy in my airplane (I would have to
remove either the ADF or LORAN to add an IFR GPS to my panel) is very
low. Thus I'm glad the FAA keeps the NDB approach alive.

In your place I might feel the same.
I kept my ADF when I installed an approach GPS three years ago, but I
haven't used it except, rarely, for practice.

Actually, as a senior engineer at one of Honeywell's big competitors,
I can tell you that it IS a problem. Not the toy quitting, but the
absolute lack of understanding of certain concepts (most obviously
significant figures) in the new crop of engineers who were never
forced to master the slide rule. It's not that you CAN'T teach these
concepts without a slide rule - but with the calculators, you can get
by with not teaching them.

Yes, it is true that practically everything is dumbing down. Technological
advancements often drive this. GPS for pilots is a great example. I'm not
arguing that this is a good thing, only that it is inevitable. Easier wins
every time. Despite the miserable MMI's of certified GPS's, it's still a lot
easier to *fly* a non-precision approach with one than it is with an ADF.
All you've got to do is make track=bearing and you're right down the pipe.

Meanwhile, look at your whizwheel and tell me slide rules are
obsolete.

I don't have a whizwheel. I have an electronic E6B.
--
Dan
C172RG at BFM

"Dan Luke" c172rgATbellsouthDOTnet wrote
Yes. The taildragger also still has certain operational advantages

It does? The operational advantages have managed to elude me. I
suppose if you make the strip rough enough and the engine big
enough...

and nostalgic appeal.

There you go. That's really what keeps them alive.

But what does it hurt to keep taildraggers around as long
as people want to fly them?

And what does it hurt to keep NDB's around as long as people want to
fly them? We've solved the taildragger problem. It's obsolete
technology of marginal utility, but some people like them, so we
acknowledge that tailwheel flying demands some skills you don't
absolutely need in tri-gear flying (if you're willing to fly sloppy)
and have a special endorsement. I'm suggesting that the same solution
is appropriate for NDB's. I think that makes a lot more sense than
just shutting them down (since they cost next to nothing to operate)
and also makes a lot more sense than letting some CFII who never flew
an NDB approach in his life try and teach an instrument student how to
do it (which is exactly what happens at my home field).

I kept my ADF when I installed an approach GPS three years ago, but I
haven't used it except, rarely, for practice.

I use my ADF for practice a lot. My personal standard for multiengine
IFR proficiency is being able to fly a night circling single engine
partial panel full procedure NDB approach to a short obstructed
runway. Some people have told me I'm nuts, but I think it makes good
training. No, I would not do that in real life unless I absolutely
couldn't avoid it - but I think if more IFR pilots did it in training,
we would have fewer accidents in real life.

Michael

David Megginson wrote
I think that the only way that a LOC or VOR approach would be
significantly easier than an NDB approach is if you were chasing the
needle: if you chase the CDI in a VOR or LOC approach, you still stay
close to track (in a constant series of S-turns); if you chase the NDB
needle, you end up approaching the NDB downwind from the track.

You got it. The other difference - with the NDB, you absolutely must
keep the DG (if available) on the correct compass heading.

I'm not nearly good enough to do a lot of mental math on any approach
(not as long as they maintain that picky requirement about not flying
into the ground), so I just leave my ADF card with north at the top
like a fixed card, and remember how far my wind-correction angle is to
the left or right, just like I do with a VOR or LOC approach. As long
as the NDB needle position is the same as my wind-correction angle,
I'm on the approach track.

How about when you're doing the procedure turn? How do you know when
to start your turn to your final approach course? More mental math?

The only difference is the fact that the ADF starts (sort-of)
reverse-sensing after station passage, so that what starts out like a
LOC approach can end up like a LOC(BC) approach. I just remember

Push the head, pull the tail

and everything usually works out fine.

More stuff to remember. The VOR needle keeps working the same way
throughout the approach.

You can teach those skills without the ADF, but without the ADF you
can get by with NOT teaching those skills, save 10 hours, and the
student can still pass the checkride.

I find it hard to believe that anyone could pass an IFR checkride by
chasing a CDI in a zigzag -- can they?

Yes. They can. I've seen it happen. Just like students who drive
the airplane onto the runway can pass the private checkride in a 172
or Cherokee, when a Cub or a Champ would eat their lunch for doing it.
I've seen that happen too.

Like I said - you don't need an ADF to teach these basic skills - and
they are basic - but without the ADF, you can get by without teaching
them, and many do.

Michael

(Michael) writes:

How about when you're doing the procedure turn? How do you know when
to start your turn to your final approach course? More mental math?

There are big marks on the ADF indicator every 45 degrees, just as
there are on the HI. Depending on which side I'm coming in from the
PT, I wait until the needle is close to the 45-degree mark to the left
or right of the top of the indicator, then turn in.

The inbound turn is actually one of the few places where the NDB
approach is easier -- the LOC sometimes comes across so fast that my
inbound turn from the PT becomes an S-turn, especially if I have a
tailwind (i.e. a crosswind for the final approach). The ADF always
gives me lots of warning as I approach the track and never forces me
to snap into a 30-degree bank just to stay within the protected area.

I hope that there aren't any instructors who force students to do
complex mental math for this kind of thing instead of just using the
big, easy marks on the ADF indicator. If instructors do that, no
wonder people hate NDB approaches so much!

More stuff to remember. The VOR needle keeps working the same way
throughout the approach.

Quite right. As someone else mentioned, though, the LOC(BC) approach
can be even more of a challenge. Not only do you have the reverse
sensing, which can be a big problem if you don't have special
equipment and you're not current with LOC(BC) approaches, but you also
have the exaggerated sensitivity near the threshold approach, at
exactly the time that you don't want to destabilize your approach by
chasing a wandering CDI.

I find it hard to believe that anyone could pass an IFR checkride by
chasing a CDI in a zigzag -- can they?

Yes. They can. I've seen it happen.

OK, now I see what you mean about the NDB approaches forcing
instructors to teach basic skills that they might otherwise neglect.
I don't particularly like that argument -- it's the same as the flawed
argument that teaching Latin helps people learn English grammar -- but
at least I can see where you're coming from. Perhaps raising the test
standards in that area would be a better solution.

For me, finishing up my instrument rating in Eastern Ontario, NDB
approaches and enroute navigation along LF/MF airways are simply a
fact of life and will likely be so for a while after my flight test.
I make no claim that NDB approaches are especially virtuous or make me
a better pilot, but the alternative (an IFR-certified GPS) is
prohibitively expensive -- a whole year's flying expenses for my
Warrior II -- and even then, it wouldn't let me fly IFR in much of the
far north.


All the best,


David

--
David Megginson, , http://www.megginson.com/

David Megginson wrote:


There are big marks on the ADF indicator every 45 degrees, just as
there are on the HI. Depending on which side I'm coming in from the
PT, I wait until the needle is close to the 45-degree mark to the left
or right of the top of the indicator, then turn in.

Laugh It took me a while to figure out what you meant by this. My mental
picture of the process is sufficiently different from yours that I'd no
idea from where you were getting the number 45. It finally dawned on me
that you're flying a 45 degree intercept to the inbound course.

I know when to turn because the ADF is telling me that I'm close to the
desired inbound course. I tend to do this by mentally overlaying the
picture of the HI with the picture of the ADF, but I'll turn the card if I
think of it.

It never occurred to me to see it as you do, although of course we're doing
precisely the same thing.

The inbound turn is actually one of the few places where the NDB
approach is easier -- the LOC sometimes comes across so fast that my
inbound turn from the PT becomes an S-turn, especially if I have a
tailwind (i.e. a crosswind for the final approach). The ADF always
gives me lots of warning as I approach the track and never forces me
to snap into a 30-degree bank just to stay within the protected area.

For this reason, why not a 30 degree intercept to a localizer? It slows the
needle.

- Andrew

Andrew Gideon writes:

Laugh It took me a while to figure out what you meant by this. My
mental picture of the process is sufficiently different from yours
that I'd no idea from where you were getting the number 45. It
finally dawned on me that you're flying a 45 degree intercept to the
inbound course.

Sorry -- I was assuming the standard, hockey-stick procedure turn, and
should have said that.

For this reason, why not a 30 degree intercept to a localizer? It
slows the needle.

Sure, that would work fine, and would have the advantage of giving me
a longer final. I use 45 only because I can read the headings
straight off the procedure-turn diagrams on the approach plates, so I
don't have to think too much. I love aviation-arithmetic problems
sitting here at my desk, but my head gets a little mushy in the plane
sometimes.


All the best,


David

--
David Megginson, , http://www.megginson.com/

David Megginson wrote
OK, now I see what you mean about the NDB approaches forcing
instructors to teach basic skills that they might otherwise neglect.

Like I said, you don't need the ADF to teach those things. On the
other hand, without the ADF, you can get by without teaching them. I
don't believe that's a good enough reason to put an ADF in every
instrument trainer - you'll recall I was the one who proposed an
instrument rating not valid for ADF approaches as the solution for
those who didn't learn the necessary skills. It's the same solution
used for taildraggers, and I think it works OK.

Perhaps raising the test
standards in that area would be a better solution.

Maybe. Or maybe in the modern world we just don't need to force
people to learn those basic skills. Look at how many pilots fly just
fine for years without really learning to use the rudder or make full
stall landings. Those things are not tremendously relevant in today's
trainers (C-172's and Cherokees) under most conditions, and they're
REALLY not relevant in today's transport category airplanes. Thus I
can easily see why one of those career-track programs wouldn't bother
teaching those skills.

The same applies to the ADF. For this reason, a lot of the
career-track operations just don't have ADF's in any of their
airplanes. And that's fine. My real goal with the ADF limitation is
to make it impossible for the graduates of those programs (who are all
CFII's) to teach IFR in the world of light GA, where the NDB approach
is alive and well, without being forced to develop those basic skills.

Michael

(Michael) writes:

Look at how many pilots fly just fine for years without really
learning to use the rudder or make full stall landings.

Doesn't loss of control on the landing roll account for a
disproportionately large number of accidents, even for Cherokees and
Skyhawks?


All the best,


David

--
David Megginson, , http://www.megginson.com/