FAR Part 97: Aircraft Approach Categories - IAS vs Ground Speed

On 7/15/2005 11:17, Steven P. McNicoll wrote:

"Mark Hansen" wrote in message
...

I'm an Instrument Airplane student, and am having a disagreement
with my instructor on one topic - that of Aircraft Approach Categories.

According to 14 CFR Part 97.3 (b), it provides the speed ranges for
the different aircraft categories (A-E). In all the documentation I've
read, this "speed" is the IAS of the airplane.

However, my CFI says that this is based on the Ground Speed. When
we are flying an approach with a tail wind and can see that, although
we are remaining below 90kts IAS, our Ground Speed (shown by the GPS unit)
is just over 90kts, he said I must use the category B minimums.

I understand his reasoning (in that the faster we're moving across
the ground, the faster we'll move out of the protection zone, etc.),
but from what I can find, the FAR doesn't mention ground speed at all.

If I use the minimums associated with the higher of the IAS or
Ground Speed, would I get dinged during a proficiency check?

The reason I ask is that I've been asked questions before where the
examiner was trying to make sure that I completely understood the
rule, and I'm worried that selecting minimums that are higher than
necessary will show that I don't really understand it.


I think your instructor is confusing the approach category speeds with the
timing table speeds, which ARE ground speeds.


No, Actually, he's not (unfortunately).




--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

"Mark Hansen" wrote in message
...

No, Actually, he's not (unfortunately).


Well, he had to get the idea they were ground speeds somewhere. The timing
table is pretty much the only possible source.

On 7/15/2005 11:52, Steven P. McNicoll wrote:

"Mark Hansen" wrote in message
...

No, Actually, he's not (unfortunately).


Well, he had to get the idea they were ground speeds somewhere. The timing
table is pretty much the only possible source.



His reasoning is that the faster we're moving across the ground,
the faster we'll move outside of the protected area, for example,
on the circling maneuver, and that to use the higher minimums
'just made good common sense'.

However, he's interpreting the rule using this 'common sense'
and claiming that this is what the rule implies.

He made it clear to me that he was talking about the approach category
minimums and not just the time from FAF to MAP (which, of course,
is based on ground speed).



--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

"Mark Hansen" wrote in message
...
On 7/15/2005 11:12, Michael wrote:

According to 14 CFR Part 97.3 (b), it provides the speed ranges for
the different aircraft categories (A-E). In all the documentation I've
read, this "speed" is the IAS of the airplane.

And so it is (almost - I seem to recall it's really CAS, but that
wouldn't make much difference). That's the regulation.

However, my CFI says that this is based on the Ground Speed.

It's hard to prove a negative, so I can't say there is NO regulatory
support for what he says, but I've certainly never seen it. Have you
asked him to show you where he read this? Further, without RNAV that
works at low altitudes or DME on the approach (which isn't rare but is
far from universal), ground speed is an estimate - and these rules are
a lot older than widespread use of RNAV that works at low altitudes.

In other words - I think your CFI is totally wrong on this one.

The reason I ask is that I've been asked questions before where the
examiner was trying to make sure that I completely understood the
rule, and I'm worried that selecting minimums that are higher than
necessary will show that I don't really understand it.

Well, yes, it will. Only I think you understand it fine; it's your
instructor who is steering you wrong.

There are situations where it makes sense to select higher minimums on
an approach (especially a circling approach) where the higher speed
makes remaining within the protected area for the lower mins
problematic. I certainly don't think it would be wrong to say "Yes, I
know that technically cat A mins apply, but I am going to use Cat B
mins because the wind conditions make remaining within the Cat A
protected area problematic." If the situation is a circling approach
with restrictions imposed and very high winds that would require an
excessive bank angle to remain within the protected area, he would
probably consider that a sign of good judgment. But you should be
clear that this is something you are choosing to do because it makes
sense, and that the regulations do permit lower mins.

Thank you Michael. This is how I've been looking at it (but I didn't
express it very well).

When I've asked my CFI to show me the regs, he basically says that it
makes sense to use the higher mins, and I haven't pushed it. This isn't
the first time we've disagreed on the Regs. In another case, he claimed
that it was illegal to fly IFR without a flight plan and ATC clearance,
but that rule applies only to Controlled airspace.

I think I won't bother pushing it, as I'm clear on the concept, and
don't really need to head-but the CFI over it ;-)


Michael



--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

I would fire him when it is convienent. There is no point in using a CFII
that not only harbors errors in his understanding but is also incapable of
learning and changing his position when it is pointed out to him. Of
course, that applies to all people and all fields.

Mike
MU-2

"Mark Hansen" wrote in message
...
On 7/15/2005 11:52, Steven P. McNicoll wrote:

"Mark Hansen" wrote in message
...

No, Actually, he's not (unfortunately).


Well, he had to get the idea they were ground speeds somewhere. The
timing table is pretty much the only possible source.

His reasoning is that the faster we're moving across the ground,
the faster we'll move outside of the protected area, for example,
on the circling maneuver, and that to use the higher minimums
'just made good common sense'.

However, he's interpreting the rule using this 'common sense'
and claiming that this is what the rule implies.

He made it clear to me that he was talking about the approach category
minimums and not just the time from FAF to MAP (which, of course,
is based on ground speed).



--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

This CFII is stupid. Once you start circling the winds change and will
become a headwind at some point.

Mike
MU-2

On 7/15/2005 12:12, Mike Rapoport wrote:

"Mark Hansen" wrote in message
...
On 7/15/2005 11:52, Steven P. McNicoll wrote:

"Mark Hansen" wrote in message
...

No, Actually, he's not (unfortunately).


Well, he had to get the idea they were ground speeds somewhere. The
timing table is pretty much the only possible source.

His reasoning is that the faster we're moving across the ground,
the faster we'll move outside of the protected area, for example,
on the circling maneuver, and that to use the higher minimums
'just made good common sense'.

However, he's interpreting the rule using this 'common sense'
and claiming that this is what the rule implies.

He made it clear to me that he was talking about the approach category
minimums and not just the time from FAF to MAP (which, of course,
is based on ground speed).



--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

This CFII is stupid. Once you start circling the winds change and will
become a headwind at some point.

Ya know ... I mentioned this to him as well. However, I think he's
stuck on the Ground Speed reported by the GPS during the final
approach as being the speed used to determine the approach category...
That's just not what the FARs say.


Mike
MU-2




--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

Roy Smith wrote:

In article , wrote:
You are correct. There is no end to what some flight instructors will dream
up or invent. Everything the FAA does in the world of charting is predicated
on IAS.

The one exception would be the FAF-MAP timing chart for non-precision
approaches. That's groundspeed. Perhaps that's what got the
instructor confused.

The FAA doesn't provide timing tables in the source. The chart makers do those.
Those are still indicated airspeed. If you choose to convert those values to TAS,
then to G/S, that is your option and is a good operating practice. But, it is not
mandatory, at least not in the sense that courses and altitudes on an IAP chart
are mandatory.

"Steven P. McNicoll" wrote:

wrote in message ...

You are correct. There is no end to what some flight instructors will
dream
up or invent. Everything the FAA does in the world of charting is
predicated
on IAS.


Not quite everything. The approach timing table uses ground speed.

More correctly, the Jeppesen timing table states ground speed. NACO does not.

"Mark Hansen" wrote in message
...
When I've asked my CFI to show me the regs, he basically says that it
makes sense to use the higher mins, and I haven't pushed it.

But using ground speed instead of airspeed could result in selecting lower
mins rather than higher.

--Gary

wrote:


The FAA doesn't provide timing tables in the source. The chart makers do those.
Those are still indicated airspeed. If you choose to convert those values to TAS,
then to G/S, that is your option and is a good operating practice. But, it is not
mandatory, at least not in the sense that courses and altitudes on an IAP chart
are mandatory.

I meant to say if you choose to use those values as G/S and do the necessary
conversions from IAS to TAS to G/S, that is your option and a good operating practice.