Change in AIM wording concerning procedure turn

"S Narayan" wrote in message
news:1128031835.1bb41b72ab7f6a781ad35e5e7380cc8f@t eranews...

"Gary Drescher" wrote in message
...
"Kris Kortokrax" wrote in message
...
New text

5-4-9. Procedure Turn
a. A procedure turn is the maneuver prescribed to perform a course
reversal to establish the aircraft inbound on an intermediate or final
approach course. The procedure turn or hold in lieu of procedure turn is
a required maneuver

(the following text is underlined in the AIM)
when it is necessary to perform a course reversal.

The procedure turn is not required when the symbol "No PT" is shown,
when RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.

The new text strikes me as entirely ambiguous. It could mean:

"The procedure turn is a required maneuver, unless one of the following
conditions obtains, in which case a course reversal is unnecessary: 1)
the symbol 'NoPT' is shown; 2) radar vectoring to the final approach
course is provided; 3) you are conducting a timed approach; or 4) the
procedure turn is not authorized."

Or it could mean:

"The procedure turn is a required maneuver, unless: 1) the symbol 'NoPT'
is shown; 2) radar vectoring to the final approach course is provided; 3)
you are conducting a timed approach; or 4) the procedure turn is not
authorized; or 5) there is (for any reason) no necessity to perform a
course reversal."

The two interpretations differ if conditions 1-4 don't obtain, but the
pilot (and/or controller) thinks there's no need for a course reversal.
The first interpretation says the procedure turn is still required in
that case; the second one says the opposite.

As a previous poster noted, they need to define how many degrees of turn
constitutes a "course reversal". Then it would clear and unambiguous.
Otherwise it is still is open to interpretation depending on the
aircraft/speed etc.

No, the ambiguity I'm pointing out isn't just a matter of the vagueness of
"course reversal". The new AIM phrasing is ambiguous as to whether the
enumerated conditions are meant only as an *elaboration* of what it means
for a course reversal to be unnecessary (in which case a charted PT is
required unless the enumerated conditions are met), or whether a lack of
need for a course-reversal is meant as an *addition* to the enumerated
conditions (in which case the PT might not be required even if none of the
enumerated conditions are met).

A secondary point (mentioned earlier in the thread) is that the TERPS
standards can require a PT on the basis of altitude, even if you're already
aligned with the final approach course. Moreover, it would make little sense
for the AIM to recapitulate the TERPS criteria for PTs in order to specify
the required action by pilots. Instead, the procedure chart itself should be
designed according to the TERPS criteria, and should specify a PT
requirement (by omitting the 'NoPT' designation) whenever those criteria are
met. The first interpretation above would be consistent with that intent.

--Gary

"Gary Drescher" wrote in message
...


No, the ambiguity I'm pointing out isn't just a matter of the vagueness of
"course reversal". The new AIM phrasing is ambiguous as to whether the
enumerated conditions are meant only as an *elaboration* of what it means
for a course reversal to be unnecessary (in which case a charted PT is
required unless the enumerated conditions are met), or whether a lack of
need for a course-reversal is meant as an *addition* to the enumerated
conditions (in which case the PT might not be required even if none of
the
enumerated conditions are met).

I think its the second case. Here is the language again:

The procedure turn or hold in lieu of procedure turn is a required
maneuver when it is necessary to perform a course reversal.
The procedure turn is not required when the symbol "No PT" is shown, when
RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.

The first sentence doesn't make any sense unless there are situations where
"it is necessary to perform a course reversal." If that's true, then the
second sentence must be exceptions to the first, that is, situations where
it would appear "necessary to perform a course reversal" but a PT is not
required.

If the intent were that a PT is required unless one of the four exceptions
applied, they would (or at least should) have said:

The procedure turn or hold in lieu of procedure turn is a required
maneuver unless the symbol "No PT" is shown, when
RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.

which would have been clear and unambiguous. General rules of construction
suggest that you should interpret the language so that the first sentence is
not redundant or meaningless, which leads to the second interpretation, what
G. Drescher calls *addition*. Maybe the rules of construction should be in
the POH?

Just my opinion, I could be wrong.

On Sat, 01 Oct 2005 08:21:52 GMT, "Brad Salai"
wrote:



If the intent were that a PT is required unless one of the four exceptions
applied, they would (or at least should) have said:

The procedure turn or hold in lieu of procedure turn is a required
maneuver unless the symbol "No PT" is shown, when
RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.

which would have been clear and unambiguous. General rules of construction
suggest that you should interpret the language so that the first sentence is
not redundant or meaningless, which leads to the second interpretation, what
G. Drescher calls *addition*. Maybe the rules of construction should be in
the POH?

Just my opinion, I could be wrong.



That's basically how Jepp defines it for their approach charts.

"It (the procedure turn) is a required maneuver, except under the following
conditions:
1. The symbol “NoPT” is shown.
2. Radar vectoring is provided.
3. A one-minute holding pattern is published in lieu of a procedure turn.
4. A teardrop course reversal is depicted.
5. The procedure turn is not authorized. "

The one-minute holding pattern and teardrop course reversal are also
mandatory in the same sense; Jepp means that you can't do a PT turn of the
type and starting point you wish if one of those is charted.

Also, Jepp's convention for the procedure turn not being authorized is that
they don't chart it.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

"Brad Salai" wrote in message
...

"Gary Drescher" wrote in message
...

No, the ambiguity I'm pointing out isn't just a matter of the vagueness
of
"course reversal". The new AIM phrasing is ambiguous as to whether the
enumerated conditions are meant only as an *elaboration* of what it means
for a course reversal to be unnecessary (in which case a charted PT is
required unless the enumerated conditions are met), or whether a lack of
need for a course-reversal is meant as an *addition* to the enumerated
conditions (in which case the PT might not be required even if none of
the
enumerated conditions are met).

I think its the second case. Here is the language again:

The procedure turn or hold in lieu of procedure turn is a required
maneuver when it is necessary to perform a course reversal.
The procedure turn is not required when the symbol "No PT" is shown,
when
RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.

The first sentence doesn't make any sense unless there are situations
where
"it is necessary to perform a course reversal."

Sure.

If that's true, then the
second sentence must be exceptions to the first, that is, situations where
it would appear "necessary to perform a course reversal" but a PT is not
required.

Yes and no. Yes, the second sentence lists situations in which a charted PT
is not required (the PT does not necessarily "appear necessary" in those
situations, though, except to the extent that simply being charted might
make them appear necessary). But no, the second sentence doesn't list
exceptions to the if-then assertion made by the first sentence; that is, the
second sentence does not list situations in which there is a necessary
course reversal but not a required PT.

If the intent were that a PT is required unless one of the four exceptions
applied, they would (or at least should) have said:

The procedure turn or hold in lieu of procedure turn is a required
maneuver unless the symbol "No PT" is shown, when
RADAR VECTORING to the final approach course is provided, when
conducting a timed approach, or when the procedure turn is not
authorized.
which would have been clear and unambiguous.

Yes, if that was their intent, they should have used that wording, or else
they should have used the "elaboration" paraphrase I proposed earlier in the
thread. But if their intent was as you believe, then they should have used
the "addition" paraphrase I proposed, which would also have been clear and
unambiguous. In fact, though, they used neither, and their chosen phrasing
was not clear or unambiguous.

General rules of construction
suggest that you should interpret the language so that the first sentence
is
not redundant or meaningless,

Correct.

which leads to the second interpretation, what G. Drescher calls
*addition*.

No, because my "elaboration" interpretation *also* allows the first sentence
to be meaningful and not redundant. Here is the "elaboration" paraphrase
again:

"The procedure turn is a required maneuver, unless one of the following
conditions obtains, in which case a course reversal is unnecessary: 1) the
symbol 'NoPT' is shown; 2) radar vectoring to the final approach course is
provided; 3) you are conducting a timed approach; or 4) the procedure turn
is not authorized."

In this paraphrase, the sentence in question is construed to be explaining
the rationale for the exceptions--namely, that the reason the PT maneuver
isn't required in the exceptional cases is that a reversal of course is
deemed unnecessary in those cases. That explanation may not be profound, but
it is neither meaningless nor redundant.

So the AIM wording is ambiguous. But if we look beyond the wording to the
underlying logic, then the "elaboration" interpretation makes more sense
than the "addition" interpretation that you favor. That's because the
"addition" interpretation effectively expects the pilot to act as a
real-time approach designer, making her own decision as to the necessity for
a course reversal (presumably in compliance with the TERPS criteria, which
are not even part of the standard pilot curriculum). In contrast, the
"elaboration" interpretation expects the TERPS criteria to be used by the
approach-chart designer, and simply expects the pilot to comply with the
chart.

The FAA email that Tim posted earlier in the thread confirms that the FAA's
intent is indeed the "elaboration" interpretation (but of course that's not
authoritative until it appears in some official source).

--Gary