GPS Question - "Holding Pattern" not Normal

[jtaugher]

I ran across something on the GPS that nobody seems to have an answer for. Some instructors at our flight school didn't know either.

I found the same thing with a couple of different approaches but I'll use GPS 31 into West Bend (ETB) as an example.

After crossing the MAP, the GPS indicated that the next way point (MAHWP) is a holding point that is about 2 miles east of the field and about 1 mile north (see #3 below). This isn't on the Approach Chart. LLE NDB is the MAP and the holding fix.

The sequence in the GPS was as follows-

1 IGUWUf
2 LLEm
*No Waypoint Seq
3 N31HP
4 LLEh


What gives? What is N31HP?

 

[Fast n' Furious]

This is an overlay approach. Basically, overlay approaches were implimented to allow you to use your GPS to fly some previously established non precision approaches. Unlike todays RNAV (GPS) approaches, these approaches were never re-TERP'd to allow for things like better lateral accuracy and obstacle avoidance. That's not to say they are unsafe at all.....they just don't take advantage to the best that is out there because at the time the criteria to do that didn't exist.
Anyway, back to your question. The extra coding is what the GPS is using to describe the holding pattern for an approach that uses the MAP as the missed approach holding fix. While using the GPS you have to have some means of identifying that protected airspace should you have to hold. N31HP does that for you. I took a look to see if West Bend has a conventional RNAV approach scheduled but didn't see it. Depending on what obstacle is used as the controller you might get better mins. Hope this helps you.

 

[jtaugher]

So in other words, since it's a climbing right turn to 2600 and then to LLE the NDB waypoint -- N31HP is providing the furthest out point potentially where 2600 as an altitude is safe?

 

[Fast n' Furious]

That point defines the start of back side of the holding pattern for the highest category of aircraft (Cat D) that might need to use that missed approach hold. You got it. Have fun!