IR written Primary/Secondary instrument questions

I believe strongly in the primary/supporting instrument concept. For
the experienced pilot, this may not make any sense because they look
at the whole panel and figure out what's going on. But a beginning
student needs clear directions. The primary/supporting concept
provides that direction. If you let a new student loose without
teaching the primary/supporting, they will eventually learn the
correct technique, but it will take longer. There is also the
potential for omitting one instrument in the scan.



"Jeremy Lew" wrote in message ...
I do too, but that simply makes the answers more obscure-seeming.
Anyway, I just completed that section of the test bank flawlessly after
following everyone's advice (Bob G's "which instrument do you NOT want to
move" tip was especially helpful).

Thanks,
Jeremy

"Andrew Sarangan" wrote in message
om...

The supporting instruments can be a bit obscure. I treat every
instrument on the panel as a supporting instrument.

I don't understand the strong objection(s) to the primary/supporting method.

I think that if the primary/supporting system is taught properly, it's really
not too much different from the control/performance system that I prefer.
Note that the FAA's Instrument Flying Handbook states that the attitude
indicator (AI):

"... should always be used, when available, in establishing AND MAINTAINING
[my emphasis] pitch and bank attitudes".

However, it's been my experience, first as an instrument student then as a
CFII, that learning the primary/supporting method often leads to jerky,
overcontrolled flight. The problem is that the word "primary" is misleading.
Students tend to overemphasize the "primary" instrument and don't catch trends
early enough. For example, in straight and level flight, the altimeter is
"primary" for altitude, but it's really the least important instrument for
precise pitch control. A small pitch deviation, due to turbulence or
inadvertent control input, shows up first on the attitude indicator, then on
the VSI, and lastly on the altimeter. If a student concentrates too much on
the altimeter, by the time he sees a need for correction the plane can already
be in a pretty major climb or descent. This is similar to what happens to a
primary student who does steep turns staring at the altimeter instead of
looking outside at the position of the nose on the horizon. It's very easy to
get into a mode where he's chasing the altimeter, pulling the nose way up and
down, instead of catching deviations early using the outside pitch reference
and the VSI.

This is also similar to the problems a lot of students have while tracking the
localizer. They stare at the CDI needle and try to center it by reacting to
its movement, and end up chasing it back and forth.

As yet another example, although the airspeed indicator is "primary" for pitch
in a full-power climb, trying to use it for pitch control often leads to
oscillations as the student chases the lagging indication. This is
something I see a lot with VFR pilots on climb out, or in a simulated
engine-out glide. They try to chase the airspeed and are always a couple of
seconds behind, pulling the nose up and pushing it down instead of just
setting a pitch attitude, trimming away the control pressure, and then
checking the airspeed to see if the pitch needs a small correction.

Barry

A small pitch deviation, due to turbulence or inadvertent control
input, shows up first on the attitude indicator, then on the VSI, and
lastly on the altimeter.


Strongly agree with everything you said.

Barry wrote:
: However, it's been my experience, first as an instrument student then as a
: CFII, that learning the primary/supporting method often leads to jerky,
: overcontrolled flight. The problem is that the word "primary" is misleading.
: Students tend to overemphasize the "primary" instrument and don't catch trends
: early enough. For example, in straight and level flight, the altimeter is
: "primary" for altitude, but it's really the least important instrument for
: precise pitch control. A small pitch deviation, due to turbulence or
: inadvertent control input, shows up first on the attitude indicator, then on
: the VSI, and lastly on the altimeter. If a student concentrates too much on
: the altimeter, by the time he sees a need for correction the plane can already
: be in a pretty major climb or descent. This is similar to what happens to a
: primary student who does steep turns staring at the altimeter instead of
: looking outside at the position of the nose on the horizon. It's very easy to
: get into a mode where he's chasing the altimeter, pulling the nose way up and
: down, instead of catching deviations early using the outside pitch reference
: and the VSI.

: This is also similar to the problems a lot of students have while tracking the
: localizer. They stare at the CDI needle and try to center it by reacting to
: its movement, and end up chasing it back and forth.

: As yet another example, although the airspeed indicator is "primary" for pitch
: in a full-power climb, trying to use it for pitch control often leads to
: oscillations as the student chases the lagging indication. This is
: something I see a lot with VFR pilots on climb out, or in a simulated
: engine-out glide. They try to chase the airspeed and are always a couple of
: seconds behind, pulling the nose up and pushing it down instead of just
: setting a pitch attitude, trimming away the control pressure, and then
: checking the airspeed to see if the pitch needs a small correction.

: Barry

Thus my original comment on the most "integrated" (mathematically) instrument.
Those are usually the primary instruments for non-transitioning flight.

-Cory



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(Andrew Sarangan) wrote
I believe strongly in the primary/supporting instrument concept.

I don't.

For
the experienced pilot, this may not make any sense because they look
at the whole panel and figure out what's going on. But a beginning
student needs clear directions.

I agree with this part completely.

The primary/supporting concept provides that direction.

It absolutely does. I just think it provides suboptimal direction.

If you let a new student loose without
teaching the primary/supporting, they will eventually learn the
correct technique, but it will take longer. There is also the
potential for omitting one instrument in the scan.

I think everything you say would be 100% correct if the only choices
were "teach the student a scan based on the primary/supporting method"
or "let him flounder around and find his own way." I do not in any
way disagree with the value of teaching a scan. I simply do not agree
that "primary and supporting" is the best scan to teach. Neither does
the military, which teaches the performance/control method
exclusively.

From a control theory viewpoint, the primary/secondary method is
primarily a feedback method, and the performance/control method is
primarily a feedforward method. Of course this is a gross
oversimplification - there are feedback and feedforward components to
each - but it's a matter of emphasis.

In the performance/control model, the emphasis is on the attitude of
the airplane. This is either read directly off the AI, or inferred
from the TC and ASI in partial panel flight. That centers the scan.
If you keep the wings level, heading will stay approximately constant.
If you keep the wings banked, you will turn. If you keep the nose on
the horizon, you will hold altitude. If you raise it, you will climb.
Lower it, and you will descend. The correct pitch and bank angles
vary based on the performance of the airplane, but they are pretty
well known in advance, so the method is more about acting than
reacting.

On the other hand, the primary/secondary method is based on reaction.
In level flight, the primary pitch instrument is the altimeter. So
let's say the altitude goes up. Why did it go up? Did you let your
nose come up? How much? By the time you saw the result on the
altimeter, it might have been a lot or a little. How much should you
correct? What if your nose is still on the horizon, and you simply
entered rising air?

Of course this is more important when flight attitude changes - at
which point the FAA gives up and makes the AI primary, making the
methods equivalent. But why should it not be primary all the time?

Michael

"Barry" wrote in message
...
I don't understand the strong objection(s) to the primary/supporting
method.

I think that if the primary/supporting system is taught properly, it's
really
not too much different from the control/performance system that I prefer.
Note that the FAA's Instrument Flying Handbook states that the attitude
indicator (AI):

"... should always be used, when available, in establishing AND
MAINTAINING
[my emphasis] pitch and bank attitudes".

However, it's been my experience, first as an instrument student then as a
CFII, that learning the primary/supporting method often leads to jerky,
overcontrolled flight. The problem is that the word "primary" is
misleading.
Students tend to overemphasize the "primary" instrument and don't catch
trends
early enough. For example, in straight and level flight, the altimeter is
"primary" for altitude, but it's really the least important instrument for
precise pitch control. A small pitch deviation, due to turbulence or
inadvertent control input, shows up first on the attitude indicator, then
on
the VSI, and lastly on the altimeter. If a student concentrates too much
on
the altimeter, by the time he sees a need for correction the plane can
already
be in a pretty major climb or descent. This is similar to what happens to
a
primary student who does steep turns staring at the altimeter instead of
looking outside at the position of the nose on the horizon. It's very
easy to
get into a mode where he's chasing the altimeter, pulling the nose way up
and
down, instead of catching deviations early using the outside pitch
reference
and the VSI.

This is also similar to the problems a lot of students have while tracking
the
localizer. They stare at the CDI needle and try to center it by reacting
to
its movement, and end up chasing it back and forth.

As yet another example, although the airspeed indicator is "primary" for
pitch
in a full-power climb, trying to use it for pitch control often leads to
oscillations as the student chases the lagging indication. This is
something I see a lot with VFR pilots on climb out, or in a simulated
engine-out glide. They try to chase the airspeed and are always a couple
of
seconds behind, pulling the nose up and pushing it down instead of just
setting a pitch attitude, trimming away the control pressure, and then
checking the airspeed to see if the pitch needs a small correction.

Barry



So then really the objections are because the students/instructor haven't
really learned the proper techniques. The fundamentals behind the method
are sound. I was taught both and see no problems with either. I suspect
the objections are then because the instructors aren't teaching it well
enough or want to find ways to make the students progress faster, possibly
at the expense of learning the fundamentals.

After taking my training I have trouble seeing how it is possible to get
good training without using a simulator.

Chasing a cdi needle is bad. and clearly the student needs to be corrected -
the best way is to cover it up. Have them focus on heading, then look at
the cdi for a moment, etc.