Positive Course Guidance and Descent when near localizer course

[John777]

Hi everyone,

While reviewing for those for my IPC check next week, I had doubts over topics relevant to Positive course guidance and descending from assigned altitude when in close proximity to localizer course on ILS approach.

First of all, during my instrument training, while doing the GPS holding(flew G1000), we flew direct to the waypoint to conduct holding and remember my instructor yelled at me for turning OBS to inbound course. He reasoned it with a term called "positive course guidance," and when I looked at IPH chapter 2, it mentions about PCG during DP. No other explanation for holding and other segment of flight.

Secondly, when you are at assigned altitude, say 4,000ft and ATC clears you for ILS approach, we always start desending when getting closer to the localizer course. I know it provides obstacle clearance as in circling appoach, but if you could help me find reference on that, that would be great.

Thank you and enjoy your weekends !

 

[John Collins]

Positive course guidance is the opposite of dead reckoning. You are following a navigation signal using a CDI or HSI or RMI or equivalent on a defined course.

One starts descending when cleared for the approach and established on a published portion of the procedure. This includes any feeder route, airway, TAA segment, or approach segment needed to navigate to and fly the approach. One does not start descending just because you are closer to the localizer course, you must be established on a segment and cleared for the approach before any descent may commence.

 

[Cooter]

Hi everyone,

While reviewing for those for my IPC check next week, I had doubts over topics relevant to Positive course guidance and descending from assigned altitude when in close proximity to localizer course on ILS approach.

First of all, during my instrument training, while doing the GPS holding(flew G1000), we flew direct to the waypoint to conduct holding and remember my instructor yelled at me for turning OBS to inbound course. He reasoned it with a term called "positive course guidance," and when I looked at IPH chapter 2, it mentions about PCG during DP. No other explanation for holding and other segment of flight.

Secondly, when you are at assigned altitude, say 4,000ft and ATC clears you for ILS approach, we always start desending when getting closer to the localizer course. I know it provides obstacle clearance as in circling appoach, but if you could help me find reference on that, that would be great.

Thank you and enjoy your weekends !

Did you spin the OBS before reaching the holding point?

 

[John777]

Positive course guidance is the opposite of dead reckoning. You are following a navigation signal using a CDI or HSI or RMI or equivalent on a defined course.

One starts descending when cleared for the approach and established on a published portion of the procedure. This includes any feeder route, airway, TAA segment, or approach segment needed to navigate to and fly the approach. One does not start descending just because you are closer to the localizer course, you must be established on a segment and cleared for the approach before any descent may commence.

Thank you sir for your response.
Sir I am trying to find out the reference where it originated from and I do not know why IPH discusses PCG with DP only, I am correct.
I also referenced FAA order 8260.3B and it mentions about PCG as below:-
PCG must be provided for feeder routes, initial (except as provided for in paragraph 233b), intermediate, and final approach segments. The segments of a procedure wherein PCG is provided should be within the service volume of the facility(ies) used, except where Expanded Service Volume (ESV) has been authorized. PCG may be provided by one or more of the navigation systems for which criteria has been published.
It does not necessarily say that PCG must be provided whole duration of flight whenever using RNAV or NAVAID to fly plane but it is still confusing.

If you do not mind could you provide me with more information?

Also, does ILS provide certain amount of obstacle clearnace? if it does then how much?

John.

 

[John Collins]

In the IPH Glossary of terms, it defines:

Positive Course Guidance (PCG). A continuous display of navigational data that enables an aircraft to be flown along a specific course line (e.g., radar vector, RNAV, groundbased NAVAID).

 

[John Collins]

Also, does ILS provide certain amount of obstacle clearnace? if it does then how much?

John.

Getting into explaining TERPS criteria for obstacle clearance for an ILS is a very complex subject. It is defined in order 8260.3 and beyond the scope of what I am willing to provide education on.