ark (12/21/82)
Jeff Williams makes the following statement:
First, the approach catigory of an airplane is based on 1.3 Vs0.
However, if you are maneuvering at a speed over 90 knots, your
Cessna 172 (catigory A - 1.3 Vs0 = ~58 knots) will actually use
catigory approach minima.
I presume he meant to put a "B" between the first and second words
of the last line. At any rate, I believe this statement is only
partially correct. Here is my evidence:
>From the Pilot/Controller Glossary section of the Jeppesen Airport
and Information Directory (their version of the AIM):
Aircraft Approach Category -- A grouping of aircraft
based on a speed of 1.3 times the stall speed in the
landing configuration at maximum gross landing
weight. An aircraft shall fit in only one category.
If it is necessary to maneuver at speeds in excess
of the upper limit of a speed range for a category,
the minimums for the next higher category should be
used. For example, an aircraft which falls in
Category A, but is circling to land at a speed in
excess of 91 knots, should use the approach Category
B minimums when circling to land. The categories
are as follows:
A - < 91 knots
B - 91 to < 121 knots
C - 121 knots to < 141 knots
D - 141 to < 166 knots
E - 166 knots or more
This is a curious paragraph. First it says that a particular
airplane is permanently assigned to a single category. Then it
says that under certain conditions you should use the miniums
appropriate to the next higher category. The conditions are
when it is "necessary to maneuver" faster than the upper limit
for the category.
Is flying an ILS "maneuvering?" This paragraph does not say
explicitly, but it refers only to circling as its example. For
further elucidation, we turn to the "Arrival--IFR" section:
INSTRUMENT APPROACH PROCEDURES
a. Minimums are specified for various aircraft
approach categories based upon a value 1.3 times the
stalling speed of the aircraft in the landing
configuration at maximum certificated gross landing
weight. (See FAR 97.3(b)) If it is necessary,
whilc circling to land, to maneuver at apeeds in
excess of the upper limit of the speed range for
each category, due to the possibility of extending
the circling maneuver beyond the area for which
obstruction clearance is provided, the circling
minimum for the next higher approach category should
be used. For example, an aircraft which falls in
category C, but is circling to land at a speed in
excess of 145 knots, should use the approach
category D minimum when circling to land.
This paragraph is more clearly restricted to circlng to land.
I have not been able to find any such paragraph to talk
about other approach operations. I do not have a copy of FAR 97.3.
The argument about using circling minimums for the higher
category are well taken, but I wasn't talking about that.
My question is this: If I am flying an ILS approach at an
indicated airspeed of 95 knots in a 172, do I have to use
Category B approach minimums? If the answer is yes, can someone
quote me the regulations that apply?ark (12/21/82)
Excerpt from Jeppesen's "Avchart" cassette #3 (Approach Charts): Remember, these values [approach category airspeeds] are computed numbers, and do not necessarily represent the approach speed of the airplane. As an example, if you're flying a Category A airplane but elect to fly an approach speed of 100 knots to conform to faster traffic, you still use Category A minimums, not Category B. That seems pretty explicit. Thus the information available to me seems to indicate that (1) approach category is a characteristic of your airplane, not of your airspeed, but (2) if you must circle to land at an airspeed that is too fast for your category, you should use the circling minimums for the next higher category.