How wide is an NDB approach course?

What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

On Tue, 16 Jan 2007 21:28:12 GMT, Jose
wrote:

What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose

When within 10 degrees of the published course.

When within 10 degrees of the published [NDB approach] course.

Thanks. I take it the course is then 20 degrees wide, with some lesser
protected area on the outskirts.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

Jose wrote:
What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose

A whole lot wider than an ILS. From TERPs.

b. Area. Figure 57 illustrates the final approach primary and secondary
areas. The primary area is longitudinally centered on the FAC, and is 10
miles long. The primary area is 2.5 miles wide at the facility, and
expands uniformly to 6 miles wide at 10 miles from the facility. A
secondary area is on each side of the primary area. It is zero miles
wide at the facility, and expands uniformly to 1.34 miles on each side
of the primary area at 10 miles from the facility. When the 5 mile PT is
used, only the inner 5 miles of the final approach area need be considered.

The required obstacle clearance is also greater than other non-precision
approaches: 300 feet with FAF, 350 without.

The FAA does not define when established on an NDB or any other course.
It is implied by the IR PTS, but that is not a precise definition.

ICAO does define such things. But, those are not valid for FAA procedures.

Jose wrote:

What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose

From TERPs:

b. Area. Figure 57 illustrates the final approach primary and secondary
areas. The primary area is longitudinally centered on the FAC, and is 10
miles long. The primary area is 2.5 miles wide at the facility, and
expands uniformly to 6 miles wide at 10 miles from the facility. A
secondary area is on each side of the primary area. It is zero miles
wide at the facility, and expands uniformly to 1.34 miles on each side
of the primary area at 10 miles from the facility. When the 5 mile PT is
used, only the inner 5 miles of the final approach area need be considered.

Also, the minimum obstacle clearance is greater than other NPAs; 300
feet with FAF, 350 without.

The FAA has never defined on course. That is up to the pilot. The IR
PTS gives some fences, but that is about it.

Bill Zaleski wrote:
On Tue, 16 Jan 2007 21:28:12 GMT, Jose
wrote:


What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose


When within 10 degrees of the published course.

There is no policy or rule to support that.

On Tue, 16 Jan 2007 16:50:04 -0800, Sam Spade
wrote:

Bill Zaleski wrote:
On Tue, 16 Jan 2007 21:28:12 GMT, Jose
wrote:


What is the protected area under an NDB approach course? Since the
course guidance is cruder than an ILS, I'd expect it would be wider, but
how much wider? I ask also in the context of when I should consider
myself "established" on course (for purposes of descent).

Jose


When within 10 degrees of the published course.

There is no policy or rule to support that.

He asked when he should consider himself established for the purpose
of descent. Have you got better guideline to follow when in a cockpit
looking at an instrument panel? In the absence of policy or rules, as
you say, what do you suggest a better answer would be?

[You're established inbound on an NDB]
When within 10 degrees of the published course.
There is no policy or rule to support that.

Taking Sam Spade's TERPs quote,

The primary area is longitudinally centered on the FAC, and is 10 miles long. The primary area is 2.5 miles wide at the facility, and expands uniformly to 6 miles wide at 10 miles from the facility.

I draw a little diagram, and find that the angle along the outside of
the primary area to be atan(((6/2)-(2.5/2))/10) = atan(7/40) = 10
degrees. So, ten degrees from the facility puts me 2.5 miles inside the
protected area. Sounds good to me. Start on down.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

So, ten degrees from the facility puts me 2.5 miles inside the protected area.

Oops. 2.5/2 miles, or 1.25 miles inside the protected area. Pesky twos!

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

On Wed, 17 Jan 2007 04:57:04 GMT, Jose
wrote:

[You're established inbound on an NDB]
When within 10 degrees of the published course.
There is no policy or rule to support that.

Taking Sam Spade's TERPs quote,

The primary area is longitudinally centered on the FAC, and is 10 miles long. The primary area is 2.5 miles wide at the facility, and expands uniformly to 6 miles wide at 10 miles from the facility.

I draw a little diagram, and find that the angle along the outside of
the primary area to be atan(((6/2)-(2.5/2))/10) = atan(7/40) = 10
degrees. So, ten degrees from the facility puts me 2.5 miles inside the
protected area. Sounds good to me. Start on down.

Jose

That's a lot of math to try to acomplish during an NDB approach.
Sounds like you are measuring it with a micrometer and cutting it with
an axe. You need much simpler personal guidelines when you take this
stuff into the cockpit.