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

wrote:

The origin of the timing table was not specifically referenced to ground
speed. In fact, the KISS concept in pre-GPS days favored simply applying IAS
on final, as in managing human factors and keeping the priority tasks at the
top of the list, so to speak. So, the discussion is not silly at all.


That may have been a simple way some pilots were taught to use it, but
the time/distance table is based on true speed, not indicated speed. If
the FAF to MAP distance is 5NM, the time shown under 60 kts will be 5:00
minutes. This requires 60 kts TAS to cover that 5 NM distance in 5
minutes. If you have a IAS of 60 and a TAS of only 30 based on
headwinds, then it will take you 10 minutes to get to the MAP. Of
course, using IAS, you're unlikely to overshoot the MAP as long as you
have a headwind, so you're safe in that respect, but then you might
start a missed approach turn too early, and fly into an area not
protected by TERPS obstacle assessment.

JPH

"JPH" wrote in message news:NkZDe.26717$mC.16233@okepread07...
wrote:

The origin of the timing table was not specifically referenced to ground
speed. In fact, the KISS concept in pre-GPS days favored simply applying IAS
on final, as in managing human factors and keeping the priority tasks at the
top of the list, so to speak. So, the discussion is not silly at all.


That may have been a simple way some pilots were taught to use it, but the time/distance table is based on
true speed, not indicated speed. If the FAF to MAP distance is 5NM, the time shown under 60 kts will be 5:00
minutes. This requires 60 kts TAS to cover that 5 NM distance in 5 minutes. If you have a IAS of 60 and a TAS
of only 30 based on headwinds, then it will take you 10 minutes to get to the MAP. Of course, using IAS,
you're unlikely to overshoot the MAP as long as you have a headwind, so you're safe in that respect, but then
you might start a missed approach turn too early, and fly into an area not protected by TERPS obstacle
assessment.

JPH

I don't think you really meant TAS in that paragraph...

That is what I said. read the post.

Mike
MU-2


"Dan Malcolm" wrote in message
...
Mike,
Actually, niether Vbg nor minimum sink is correct in all circumstances.
Vbg will yield the greatest distance by definition, and minimum sink will
yield the greatest time. Which one is the most beneficial? Gotta look at
the circumstances. There is a good discussion at
http://www.auf.asn.au/emergencies/aircraft.html#vbg
Dan Malcolm

"Mike Rapoport" wrote in message
ink.net...
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

Just look at the NOS charts. Categories are based on IAS. It tells
you that.

When flying to the MAP from the FAF you have the distance given and
can often use GPS, or DME for the distance to the MAP, but you still
have a time to calculate time (or take it off a chart) and that is
based on a distance which has to be based on ground speed.

They come right out and tell you. It doesn't get much more simple than
that.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

On 7/22/2005 11:29, Roger wrote:

Just look at the NOS charts. Categories are based on IAS. It tells
you that.

Where does it say that? I don't see anything on the IAP that says this.
I've looked in the FARs and AIM (see the initial posting of this thread)
and they simply say "speed" and don't specifically state indicated or
ground speed.



When flying to the MAP from the FAF you have the distance given and
can often use GPS, or DME for the distance to the MAP, but you still
have a time to calculate time (or take it off a chart) and that is
based on a distance which has to be based on ground speed.

Note that I'm not talking about the FAF to MAP times (although this
thread has morphed into that discussion by others). Those times must
be based on ground speed.


They come right out and tell you. It doesn't get much more simple than
that.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


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

I did read the post and if you think that's what you said, then so be
it.
Dan
"Mike Rapoport" wrote in
ink.net:

That is what I said. read the post.

Mike
MU-2


"Dan Malcolm" wrote in message
...
Mike,
Actually, niether Vbg nor minimum sink is correct in all
circumstances. Vbg will yield the greatest distance by definition,
and minimum sink will yield the greatest time. Which one is the most
beneficial? Gotta look at the circumstances. There is a good
discussion at http://www.auf.asn.au/emergencies/aircraft.html#vbg
Dan Malcolm

"Mike Rapoport" wrote in message
ink.net...
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

OK.

I don't see what is ambigous about "it must depend on the wind"

Mike
MU-2
ATP


"PilotCFI" wrote in message
4...
I did read the post and if you think that's what you said, then so be
it.
Dan
"Mike Rapoport" wrote in
ink.net:

That is what I said. read the post.

Mike
MU-2


"Dan Malcolm" wrote in message
...
Mike,
Actually, niether Vbg nor minimum sink is correct in all
circumstances. Vbg will yield the greatest distance by definition,
and minimum sink will yield the greatest time. Which one is the most
beneficial? Gotta look at the circumstances. There is a good
discussion at http://www.auf.asn.au/emergencies/aircraft.html#vbg
Dan Malcolm

"Mike Rapoport" wrote in message
ink.net...
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

On Fri, 22 Jul 2005 12:36:15 -0700, Mark Hansen
wrote:

On 7/22/2005 11:29, Roger wrote:

Just look at the NOS charts. Categories are based on IAS. It tells
you that.

Where does it say that? I don't see anything on the IAP that says this.
I've looked in the FARs and AIM (see the initial posting of this thread)
and they simply say "speed" and don't specifically state indicated or
ground speed.


As I said, get out a set of NOS approach charts. It's right there in B
& W.

Actually, it's on page A2. Approach category and the explanation in
reference to Vso

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

When flying to the MAP from the FAF you have the distance given and
can often use GPS, or DME for the distance to the MAP, but you still
have a time to calculate time (or take it off a chart) and that is
based on a distance which has to be based on ground speed.

Note that I'm not talking about the FAF to MAP times (although this
thread has morphed into that discussion by others). Those times must
be based on ground speed.


They come right out and tell you. It doesn't get much more simple than
that.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Because wind may not be the only determining factor. Can I name them
all? No. But you should take into account
1. Wind (of course)
2. Where are trying to get to for landing
3. What is the condition of the aircraft and pilot.
4. In addition to wind, what is happening with the weather?
5. There are undoubtedly more.

So is the additional airtime a benefit? Each circumstance will dictate
the appropriate answer. Not just wind.

Dan
CFI/CFII

"Mike Rapoport" wrote in news:cpcEe.6612
:

OK.

I don't see what is ambigous about "it must depend on the wind"

Mike
MU-2
ATP


"PilotCFI" wrote in message
4...
I did read the post and if you think that's what you said, then so be
it.
Dan
"Mike Rapoport" wrote in
ink.net:

That is what I said. read the post.

Mike
MU-2


"Dan Malcolm" wrote in message
...
Mike,
Actually, niether Vbg nor minimum sink is correct in all
circumstances. Vbg will yield the greatest distance by definition,
and minimum sink will yield the greatest time. Which one is the
most
beneficial? Gotta look at the circumstances. There is a good
discussion at http://www.auf.asn.au/emergencies/aircraft.html#vbg
Dan Malcolm

"Mike Rapoport" wrote in message
ink.net...
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

wrote in message ...

Most everything pertaining to instrument procedures is predicated on
fixes,
facilities or waypoints either on the ground or geo-referenced to a
precise
location on the ground. Yet, many (most) of these procedures are
predicated on
indicated airspeed.

The origin of the timing table was not specifically referenced to ground
speed. In fact, the KISS concept in pre-GPS days favored simply applying
IAS
on final, as in managing human factors and keeping the priority tasks at
the
top of the list, so to speak. So, the discussion is not silly at all.


It's your position that is silly. When others stated the speeds in the
timing tables were ground speeds you asked for a reference showing that the
speeds on NACO charts are ground speeds. It has since been demonstrated
that the speeds are ground speeds, yet you still insist they're IAS.
Where's your reference that the speeds on NACO charts are IAS?