I use the Flight One GTN 750 and the Saitek Multi Panel with P3D and I am not sure at what point I should switch from the NAV mode to APR mode. 

Thanks a lot,

Howard

I switch when the glideslope indicators become visible on the HSI.

In simplest terms, I agree with Bert

 

Make sure you know if your approach is vertically guided. Only a few are: ILS and rnav (GPS) with LPV minimums.

And at the time you switch you should still be below the glidescope.  

I usually wait until I'm on final, or at least turning onto final. Activating APPR mode on a downwind leg could confuse things, especially if neighbouring runways have the same ILS frequencies.

British ATC phraseology comes to mind "When established on the localiser, descend on the glidepath" i.e. I don't engage approach hold until I'm lined up on the final approach course.

In simplest terms, I agree with Bert

 

Make sure you know if your approach is vertically guided. Only a few are: ILS and rnav (GPS) with LPV minimums.

? But there's no such thing as having the autopilot control the CRS/HDG but at the same time you manually control the plane vertically, unless you mean an LOC APPR?

? But there's no such thing as having the autopilot control the CRS/HDG but at the same time you manually control the plane vertically, unless you mean an LOC APPR?

Huh?

? But there's no such thing as having the autopilot control the CRS/HDG but at the same time you manually control the plane vertically, unless you mean an LOC APPR?

It's called LNAV, or simply NAV. The plane will handle the lateral stuff (your heading) and you programme the autopilot for whatever vertical mode you want (ALT hold, V/S, IAS, pitch hold etc).

 

As stated, most approach types do not provide vertical guidance (LOC, NDB, VOR and other non-precision types, and even in some cases GPS vertical guidance cannot be used).

? But there's no such thing as having the autopilot control the CRS/HDG but at the same time you manually control the plane vertically, unless you mean an LOC APPR?

 

In that case, you fly the airplane manually, watching the instruments.

In that case, you fly the airplane manually, watching the instruments.

 

Stop it Bert! Your complicating things!! 

As stated, most approach types do not provide vertical guidance

 

True. But the number of published approaches with vertical guidance has increased dramatically over the past few years and in the USA most airports of any significant size, including general aviation airports, have an approach with vertical guidance, and in many cases more than one. So it is not just a matter of the number of approach "types".

 

The number of approach types has also increased. Appending the approach names with letters has added confusion. The short table below shows what appears to be different RNAV types. But by name there are only two. RNAV (RNP) and RNAV (GPS). Here is a link to a great article explaining the letters.

http://ww1.jeppesen.com/download/aopa/jan01aopa2.pdf

 

RNAV (RNP)

RNAV (RNP) X

RNAV (RNP) Y

RNAV (RNP) Z

RNAV (GPS)

RNAV (GPS) X

RNAV (GPS) Y

RNAV (GPS) Z

 

Unfortunately, the approach names, with appended letters or not, do not indicate whether the approach has vertical guidance. The only way I know of is to look at the approach plate (chart) in the Category table near the bottom, and look for the LPV or LNAV designations.

 

Smaller airports, such as KBMG Bloomington, Indiana, and KESN Easton, Maryland, which have over the years have each had (1) ILS type approach with vertical guidance. Now each has (4) RNAV (GPS) type approaches, two of which at each airport have vertical guidance. So at each the number of approaches with vertical guidance has tripled in recent years.

 

Then take another example, Chicago Midway (KMDW). Midway has historically had (3) ILS type approaches, each with vertical guidance. It still has those, and KMDW now has (13) published RNAV (GPS) type approaches. However only (3) of those (13) contain vertical guidance. Still, the number of published approaches into Midway with vertical guidance has doubled.