Misleading Notam

[Greg Esres]

One of our local pilots misunderstood a common Notam, as shown below.
He thought the "ADD: From Shelby to RW 17: 3.52 degrees" meant add
3.52 degrees to the final approach course.

How reasonable do you think his interpretation?

(BTW, the notam just adds a descent gradient to a NP approach.)

FDC 3/0143 M01 FI/T GENERAL DEWITT SPAIN, MEMPHIS, TN. VOR RWY
16, ORIG...CHANGE ALL REFERENCES TO RWY 16/34 TO RWY 17/35.
ADD: FROM SHLBY TO RW 17: 3.52 DEGREES, TCH 31. ADD NOTE: VGSI
AND DESCENT ANGLES NOT COINCIDENT.

[Larry Fransson]

On 2003-12-01 09:49:46 -0800, Greg Esres > said:

> One of our local pilots misunderstood a common Notam, as shown below.
> He thought the "ADD: From Shelby to RW 17: 3.52 degrees" meant add
> 3.52 degrees to the final approach course.
>
> How reasonable do you think his interpretation?
>
> (BTW, the notam just adds a descent gradient to a NP approach.)

I can see where one might interpret it that way. But what the "ADD" means is
that you should ADD that note to the chart. That 3.52 degrees is the "glide
path" angle from SHLBY to the missed approach point.

If there was a change to the final approach course, that would have been
explicitly stated.

[Bob Gardner]

Gotta agree with Larry. The whole thing smacks of vertical descent path, not
lateral alignment. Poorly written, for sure. Should at least have had
quotation marks surrounding the phrase between "From" and "degrees."

Bob Gardner

"Greg Esres" > wrote in message
...
> One of our local pilots misunderstood a common Notam, as shown below.
> He thought the "ADD: From Shelby to RW 17: 3.52 degrees" meant add
> 3.52 degrees to the final approach course.
>
> How reasonable do you think his interpretation?
>
> (BTW, the notam just adds a descent gradient to a NP approach.)
>
> FDC 3/0143 M01 FI/T GENERAL DEWITT SPAIN, MEMPHIS, TN. VOR RWY
> 16, ORIG...CHANGE ALL REFERENCES TO RWY 16/34 TO RWY 17/35.
> ADD: FROM SHLBY TO RW 17: 3.52 DEGREES, TCH 31. ADD NOTE: VGSI
> AND DESCENT ANGLES NOT COINCIDENT.
>

[Mike Granby]

Hmmmm. Just how accurate is this guy's DG?

Headings in one hundredths of a degree???

--
Mike Granby, PP-ASEL,IA
Warrior N44578
http://www.mikeg.net/plane

[Greg Esres]

<<Headings in one hundredths of a degree???>>

What about descent angles to within one hundredths of a degree?

[Michael]

Greg Esres > wrote
> One of our local pilots misunderstood a common Notam, as shown below.
> He thought the "ADD: From Shelby to RW 17: 3.52 degrees" meant add
> 3.52 degrees to the final approach course.
>
> How reasonable do you think his interpretation?

For someone coversant with TERPS - not very. For someone who meets
the knowledge requirements for the instrument rating but not much more
- pretty reasonable. Note the context - the runway numbers are
changed (increased). I can easily see how someone might think that
this means the final approach course should also be adjusted, and the
direction and magnitude of the adjustment are consistent with the
runway change.

> (BTW, the notam just adds a descent gradient to a NP approach.)
>
> FDC 3/0143 M01 FI/T GENERAL DEWITT SPAIN, MEMPHIS, TN. VOR RWY
> 16, ORIG...CHANGE ALL REFERENCES TO RWY 16/34 TO RWY 17/35.
> ADD: FROM SHLBY TO RW 17: 3.52 DEGREES, TCH 31. ADD NOTE: VGSI
> AND DESCENT ANGLES NOT COINCIDENT.

Not exactly plain English, is it?

Michael

[Ron Natalie]

"Greg Esres" > wrote in message ...
> <<Headings in one hundredths of a degree???>>
>
> What about descent angles to within one hundredths of a degree?

They are consistantly listed in approach plates to that precision. Even
when they are exactly 3 degrees, the notation looks like:

GS 3.00

[Gary L. Drescher]

"Greg Esres" > wrote in message
...
> <<Headings in one hundredths of a degree???>>
>
> What about descent angles to within one hundredths of a degree?

That makes more sense. A hundredth-degree change in descent angle is
(barely) perceptible on the ASI or VSI. A hundredth-degree change in
heading is not perceptible on the HI or MC.

--Gary

[Roy Smith]

"Gary L. Drescher" > wrote:
> A hundredth-degree change in descent angle is
> (barely) perceptible on the ASI or VSI.

I'd like to see a pilot or VSI which can notice the difference between
500 fpm and 502 fpm.

[Ron Natalie]

"Roy Smith" > wrote in message ...
> "Gary L. Drescher" > wrote:
> > A hundredth-degree change in descent angle is
> > (barely) perceptible on the ASI or VSI.
>
> I'd like to see a pilot or VSI which can notice the difference between
> 500 fpm and 502 fpm.

It's not even that much.

However, the charts always show the glideslope to the 100th. They never
show headings to that accuracy. If he'd actually looked hard at the chart
as to what they were changing, the fact that the elevation (which is depecited
on the chart in the same location) also changed would have been a big clue.

[Gary L. Drescher]

"Roy Smith" > wrote in message
...
> "Gary L. Drescher" > wrote:
> > A hundredth-degree change in descent angle is
> > (barely) perceptible on the ASI or VSI.
>
> I'd like to see a pilot or VSI which can notice the difference between
> 500 fpm and 502 fpm.

You're right, it would have been more accurate for me to say a *few*
hundredths of a degree. But that still justifies more than one decimal
place of precision. A few hundredths of a degree change of descent angle
moves the VSI needle almost as much as a one-degree heading change moves the
HI (and courses are routinely specified with single-degree precision).

--Gary

[Haggerty]

Just to avoid potential confusion, the NOTAM has been reworded to include
"Vertical Descent Angle" in front of 3.52 degrees. The previous way had been
used for at least 4 years when adding VDA's to non-precision procedures via
NOTAMS, but will probably change now since the old appears to lead to
confusion. Incidentally, the reason this NOTAM was originally created is
that the airport painted new runway numbers (17/35) on the runways due to
magnetic variation updates, and Memphis Approach didn't hear about it until
after the fact.

FDC 3/1417
FI/T GENERAL DEWITT SPAIN, MEMPHIS TN. VOR RWY 16, ORIG... CHANGE ALL
REFERENCES TO RWY 16/34 TO RWY 17/35. ADD: FROM SHLBY TO RW17: VERTICAL
DESCENT ANGLE 3.52 DEGREES, TCH 31. ADD NOTE: VGSI AND DESCENT ANGLES NOT
COINCIDENT.
--

JPH


"Michael" > wrote in message
m...
> Greg Esres > wrote
> > One of our local pilots misunderstood a common Notam, as shown below.
> > He thought the "ADD: From Shelby to RW 17: 3.52 degrees" meant add
> > 3.52 degrees to the final approach course.
> >
> > How reasonable do you think his interpretation?
>
> For someone coversant with TERPS - not very. For someone who meets
> the knowledge requirements for the instrument rating but not much more
> - pretty reasonable. Note the context - the runway numbers are
> changed (increased). I can easily see how someone might think that
> this means the final approach course should also be adjusted, and the
> direction and magnitude of the adjustment are consistent with the
> runway change.
>
> > (BTW, the notam just adds a descent gradient to a NP approach.)
> >
> > FDC 3/0143 M01 FI/T GENERAL DEWITT SPAIN, MEMPHIS, TN. VOR RWY
> > 16, ORIG...CHANGE ALL REFERENCES TO RWY 16/34 TO RWY 17/35.
> > ADD: FROM SHLBY TO RW 17: 3.52 DEGREES, TCH 31. ADD NOTE: VGSI
> > AND DESCENT ANGLES NOT COINCIDENT.
>
> Not exactly plain English, is it?
>
> Michael

[Greg Esres]

<<Just to avoid potential confusion, the NOTAM has been reworded to
include>>

One of my fellow instructors called the Flight Procedures Quality
control guru and pointed out the possible confusion.