ADF subsitutions

[Ticket puncher]

I have access to an AC that does not have an ADF. It does have a Garmin 300.
The question is this: for approaches that use a bearing to define a fix can I use a made up waypoint as a substitute? There are some local opinions that you can on VOR and localizers approaches. Reading of the AIM seems to support the opinions. Just curious if that is in fact true or is there some not so obvious factor that prevents waypoint usage in this situation.

 

[TMetzinger]

I don't know what the GPS 300 is certified for, but if it's certified for IFR approaches you should be able to use it to substitute for ADF on an approach where the ADF isn't providing lateral guidance. An example would be to define a crossing or stepdown fix.

But, I'm not aware of any approaches where a bearing defines a fix on the approach and the fix isn't named (and you could just punch in the fix name). Can you give an example of the approach you're wondering about?

 

[Ticket puncher]

No particular approach in mind. Rainy weather hanger flying related to the limitations imposed by not having an ADF. The discussion started with a concern about LOC 34 at Arlington, WA (KAWO) and wether you could legally execute that approach with an IFR certified GPS in lieu of an ADF.

If I understand the operations allowed, as stated in Chapter 1 of the AIM, page 519, you can, including the missed app. procedure. Just curious if there is a, "yes...but", lurking somewhere.

 

[gismo]

No particular approach in mind. Rainy weather hanger flying related to the limitations imposed by not having an ADF. The discussion started with a concern about LOC 34 at Arlington, WA (KAWO) and wether you could legally execute that approach with an IFR certified GPS in lieu of an ADF.

If I understand the operations allowed, as stated in Chapter 1 of the AIM, page 519, you can, including the missed app. procedure. Just curious if there is a, "yes...but", lurking somewhere.

Yes you can use an IFR approved GPS (with a current DB) in lieu of an ADF to fly this approach. But there is a "but": The LOM would have to be in the DB of the GPS, as you cannot just make up a fix and use it for the approach. If the chart listed a DME distance along the FAC from another fix in the GPS DB you could use that to identify the LOM but that's not the case with this particular approach.

BTW ADF (or legal substitute) is required to determine when you can descend to the MDA as well as for flying the missed approach procedure.

 

[TMetzinger]

OK, plate is attached.

Identifying the LOM by using the fix name of WATON with an IFR GPS would certainly be a permittable substitution, as it isn't providing lateral guidance for the final approach segment. (AIM 1-2-3 c.3)

And holding is another permissable use of an IFR GPS (AIM 1-2-3 c.4).

So I don't see any reason why an IFR GPS couldn't be used in lieu of ADF on this approach.

The ADF required on the approach plate states that you need an ADF or an approved substitute.

As always, corrections/discussions are welcomed.

 

[Ticket puncher]

Great, thanks for the help.

 

[drizzt76]

Hey another Garmin GNC300XL user! Our club Archer has that box and it isn't very user friendly but once you get your head around it the box is a good capable IFR GPS unit. I do find that the hold button going outbound will not sometimes work as advertised.... I don't see too many people using this GPS.