GRP Approach Questions

[Bman.]

Morning all-

This is my first real post (outside of looking for expired sectional charts etc). I am nothing but an arm chair pilot trying to fly FSX by the books. I am in the process of reviewing various approach options. Currently I am learning GPS approaches.

A few questions I have come across-

1) Is there any way to link the marker annunciator to the GPS? It's nice to dial in an ILS or LOC and have the LOM/LMM give audible warning. I noticed last night that the GPS doesn't do anything when you pass the FAF. I didn't know if should just manually also set the localizer in my NAV1 just to get the marker notification

2) When flying a GPS approach, at what point would I have to turn off the GPS autopilot nav if not flying by hand? I know that GPS is a non-precision approach so I figured at the MDA I should turn it off - is this too late?

3) On a Garmin 500 - does the sensitivity of the CDI adjust automatically based on what is loaded into the flight plan? I see that it will change between en-route, terminal and approach.

That's all I have for now. Thanks in advance-

Benjamin

[Ian J]

Originally Posted by Bman.

Morning all-

This is my first real post (outside of looking for expired sectional charts etc). I am nothing but an arm chair pilot trying to fly FSX by the books. I am in the process of reviewing various approach options. Currently I am learning GPS approaches.

A few questions I have come across-

1) Is there any way to link the marker annunciator to the GPS? It's nice to dial in an ILS or LOC and have the LOM/LMM give audible warning. I noticed last night that the GPS doesn't do anything when you pass the FAF. I didn't know if should just manually also set the localizer in my NAV1 just to get the marker notification

2) When flying a GPS approach, at what point would I have to turn off the GPS autopilot nav if not flying by hand? I know that GPS is a non-precision approach so I figured at the MDA I should turn it off - is this too late?

3) On a Garmin 500 - does the sensitivity of the CDI adjust automatically based on what is loaded into the flight plan? I see that it will change between en-route, terminal and approach.

That's all I have for now. Thanks in advance-

Benjamin

Man - with that level of detail you might as well go out and do the real deal!

1) As long as you marker beacon button on your comm panel is on, you should hear the sound when you pass it. It is not linked to a loc frequency. If the marker coincides with a GPS waypoint it will flash at you when you pass it.

2) This is really up to you. Airlines might have some rules laid out - I dunno. You can leave to AP on till the MAP if you want, but what's the fun in that?

3) If it is like most GPSs, yes the sensitivity does change from 5nm, 1nm, and .3 nm respectively (There's a lot more to it than that - but this should do for your purposes.)

[Bman.]

Yeah, my current career is a far path from flying (architect). I just have enjoyed learning about it all. FSX provides a good level of detail and opportunity for practice. Granted, I know it's a far cry from RW application and experience. Oh well - it does the job.

Back to the questions-

1) Hmm. If the marker is not linked to the localizer, what is it linked too? Surely I have to have something dialed in for the LOM to sound.

2) Yeah, I stick flew the approach a few times last night but the cross wind was knocking off course - see visibility below. In RW I am sure I would have done miss 100% of the time

3) So the GPS will adjust automatically based on current leg?

[Ian J]

Originally Posted by Bman.

Yeah, my current career is a far path from flying (architect). I just have enjoyed learning about it all. FSX provides a good level of detail and opportunity for practice. Granted, I know it's a far cry from RW application and experience. Oh well - it does the job.

Back to the questions-

1) Hmm. If the marker is not linked to the localizer, what is it linked too? Surely I have to have something dialed in for the LOM to sound.

2) Yeah, I stick flew the approach a few times last night but the cross wind was knocking off course - see visibility below. In RW I am sure I would have done miss 100% of the time

3) So the GPS will adjust automatically based on current leg?

1) Not at all - just make sure the button is pushed in. Marker beacons emit their own signals that the airplane will pick up on its own. (The frequencies for the outer, middle and inner markers have unique frequencies that are the same everywhere).

2) Gotta correct for that wind!

3) As long as you have a flight plan and approach loaded, yes.

[BobDDuck]

It's been so long since I've shot a GPS approach in a light plane (or even in the jet) I'm digging a bit here...

As Ian said, marker beacons are always the same freq (which can be dangerous sometimes if there is another approach near by) so all you have to do is turn up the volume on the panel to hear them. That said, a marker beacon isn't going to help much on a GPS approach. On a few approaches the FAF on the GPS approach might be near the LOM, but that would just be coincidence. From your question it sounded like you wanted an alert when passing the FAF on the GPS approach. If that's the case, the only way you'll know is you probably will get a momentary full scale deflection on the CDI needle, as well as the "distance to fix" number will get bigger and then start counting down. Also the fix name you are going to should change from the FAF to either an intermediate step down fix, or the MAP/Runway.

As far as autopilots... it will vary depending on your autopilot or your op specs. We can't use the autopilot below 600 feet on a precision approach and 100 feet on a non precision approach.

From what I remember about the Garmins they operate in RNP of 5.0 in cruise flight 1.0 in the terminal area (within 30 miles of your destination airport) and .3 within 2 miles of the FAF. The Collins does pretty much the same thing in the CRJ, except instead of giving RNP numbers it just says TERM and APPR.

[Ian J]

Oh yeah, if you are really interested in stuff like this, take a look at this:

http://www.faa.gov/airports_airtraff...ns/atpubs/aim/

It's the Aeronautical Information Manual and has lots about how marker beacons, approaches, GPS, and stuff like that works.

[Bman.]

Thanks guys.

Yeah, I have purchased the hard copies of most of the FAA manuals. Lots of good information in there.

I see, I didn't realize that the FAF on a GPS approach were different that a marker location. I made the assumption that they were linked somehow. It must have been fairly coincidental.

Is there a specific distance that Outer Makers are located? They weren't indicated on the plan view of the approach plate. This was the approach I was using:

http://myairplane.com/databases/appr...s/06643G23.PDF

Nothing fancy. There is no indicator on here of the marker. Is there any way to get audible warning when I have crossed the FAF as indicated on the GPS? I mean, I can look at the GPS but under condition right near the minimums looking at the 6 pack and out the window during approach are my preference. If I had my choice, I would like to hear FAF and begin my decent to MDA.

Benjamin

[sundog]

not every airport/runway has marker beacons. not all approaches use them. the markers aren't a part of the approach you referenced. the FAF is the PORCY waypoint, which only your GPS will identify.

(there are no marker beacons out at shelton. for fun, try the NDB approach http://naco.faa.gov/d-tpp/0801/06643NGA.PDF with only an ADF needle and a strong crosswind)

on a GPS approach, you need to scan your instruments AND the gps AND look out the window. oh, and starting the timer wouldn't hurt either, just in case the GPS konks out on ya.

[E6BAV8R]

Is there a specific distance that Outer Makers are located?

Of course!

OM - 4-6 miles from runway threshold
MM - ~3500ft. from runway threshold
IM - ~1000ft. from runway threshold

Typically the OM is the FAF on an approach, or glide-slip intercept on an ILS; as well as the MM being the Decision Height on a Cat I ILS approach.

[fish314]

To add a little somethin' to your GPS question, depending on your system you will get different indications as you cycle to the next waypoint. The system in my aircraft, for example, flashes a white "WPT" annunciator several times 10 seconds before crossing the fix. But it's all specific to your system.

In a previous aircraft, the system would turn the next leg a different color, (obviously a glass cockpit).

[mojo6911]

You should read here:

http://www.faa.gov/airports_airtraff...M/chap1toc.htm