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

For that matter, don't accept what the FAA says about the regs, unless it
comes from the regulatory support division. The folks at FSDO know even
less about the FARs than the uninformed CFIs.



"Gary Drescher" wrote in
news
"Stan Gosnell" wrote in message
...
If I were
you, I would be seriously considering finding a new CFII, one who
actually knows something about flying IFR.

I don't dispute that it's worth considering; still, I think it's
possible that the CFII is a good one. His interpretation of some regs
may be sketchy, but not in a way that adversely affects safety. No
pilot should ever take a CFI's word for what the regs say anyway, so a
responsible pilot (as Mark gives every indication of being) won't be
misled by a CFI's misinterpretation of the regs.

--Gary

wrote in message ...

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.


Those values are expressed in ground speed already, converting them to
anything else would be a bad operating practice.

wrote in message ...

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


Do the timing tables on the NACO plates have different values than the
Jeppesen plates?

I had a primary instructor who insisted that the best speed to use in the
event of an engine failure was the published best glide speed. I said that
it must depend on the wind and pointed out that if there was a headwind
equal to Vbg that any speed over the Vbg was better. I also pointed out
that with a strong tailwind that the minimium sink speed would get more
distance. He continued to insist that Vbg was the speed to use. That was
our last flight.

We all harbor misconceptions but there is no excuse for being too stubborn
to learn.

Mike
MU-2

"Mark Hansen" wrote in message
...
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

"Steven P. McNicoll" wrote:

wrote in message ...

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.


The FAA is a chart maker, the speeds in the timing tables on FAA charts are
ground speed.

And, your reference that the speeds on NACO charts are ground speeds?

Gary Drescher wrote:

wrote in message ...


"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.

Whether they state it or not, there's nothing but ground speed that they
*could* be using to calculate the time to traverse the stated distance.

--Gary

For the best accuracy, it obviously has to be ground speed. But, there is no
requirement to make the necessary calculations to arrive at ground speed. A
lot of folks over many years have simply treated the timing table values as
indicated airspace, on the premise there are a lot more important things to do
in the final approach segment than attempt to make conversions.

In recent years, RNAV has all-but-eliminated any need to use the timing table
in any case.

"Steven P. McNicoll" wrote:

wrote in message ...

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


Do the timing tables on the NACO plates have different values than the
Jeppesen plates?

The values are there to be used as IAS or ground speed; it is pilot option.
Jeppesen is making an assumption that is not a regulatory charting value.

wrote:
And, your reference that the speeds on NACO charts are ground speeds?

Oh, come on, this is getting silly. The table is labeled (for example, on
the HPN NDB 16) "FAF to MAP 4.8 NM". That's one point on the ground to
another point on the ground. The times in the table tell you how long it
will take to cover that distance at various speeds. What else could the
speeds possibly mean if not ground speed?

The chart has a date on it (04 AUG 2005). Do I need to cite a reference to
convince you that the date should be interpreted according to the Julian
calendar?

This is amendment 21. Do I need to cite a reference to convince you that
"21" should be interpreted in decimal? After all, we set our transponders
in octal, why shouldn't we also number our SIAP amendments in octal?

wrote in message ...

And, your reference that the speeds on NACO charts are ground speeds?


This is getting absurd even for you. The tables provide times between fixed
points at various speeds. They can't be anything other than ground speed,
ground speed is defined as the speed of an aircraft relative to the surface
of the earth.

Let's look at an example, the LOC-B at Eagle County Regional Airport.

http://map.aeroplanner.com/plates/Fa...fs/06403LB.PDF

The distance from the FAF to the MDA is 9.5 miles. The table shows a time
of 3:10 for a speed of 180 knots. A vehicle traveling at a steady speed of
180 knots will cover a straight line distance of 9.5 nautical miles in 3:10,
so this speed certainly appears to be ground speed. But let's try another
one to be sure. The table shows a time of 9:30 for a speed of 60 knots. A
vehicle traveling at a steady speed of 60 knots will cover a straight line
distance of 9.5 nautical miles in 9:30. Again, this speed has the
properties of ground speed.

But you say they're IAS, so let's examine that. The MDA is 10,160 MSL, in a
standard atmosphere an aircraft at 180 KIAS will have a TAS of 209 knots and
will take 2:44 to travel 9.5 miles. Only with a pretty stiff headwind
component would it take 3:10 if the speeds are IAS as you insist. Are the
chart makers factoring in that wind?

Let's look at a speed of 60 KIAS. At that speed the TAS will be 70 knots,
at that speed the airplane will travel the distance in 8:57. Only with a 10
knot headwind will it require 9:30 to travel 9.5 miles. Are the chart
makers factoring in different winds for different indicated airspeeds?

I say the speeds on these charts are ground speeds simply because they can't
be anything else, I don't need a reference for that. Where's your reference
that the speeds on NACO charts are IAS?

wrote in message ...

A lot of folks over many years have simply treated the timing table values
as indicated airspace, on the premise there are a lot more important
things
to do in the final approach segment than attempt to make conversions.


What makes you think that?