T-6 Nav Computer data source?

[kmac]

Does anyone know what the data source is for the T-6? Does it use DAFIF? Jeppesen?

I'm hearing that certain step-down fixes are not showing up on RNAV (GPS) approaches. For example, Whiting-North ILS Z or RNAV (GPS) RWY 14 does not have JOHNC in the database.

Anyone care to help??

 

[sevenhelmet]

@kmac , is this in the T-6A or T-6B? Presuming B for now, since you mentioned Whiting… Has this always been an issue, or did it crop up recently? I’m pretty sure those databases come from the OEM (fed from the avionics provider) so what you might be looking for is a way to alert them to the issue so they can have a chance to correct it.

I might know a guy. Give me a day or two, and I’m 90% sure I can find a vector for you to follow.

 

[kmac]

@kmac , is this in the T-6A or T-6B? Presuming B for now, since you mentioned Whiting… Has this always been an issue, or did it crop up recently? I’m pretty sure those databases come from the OEM (fed from the avionics provider) so what you might be looking for is a way to alert them to the issue so they can have a chance to correct it.

I might know a guy. Give me a day or two, and I’m 90% sure I can find a vector for you to follow.

I’m not sure if it was the A or B, but you are probably right. I tried reaching out to some of the maintenance folks, but it was second shift by the time I called. The Avionics shop would have to update the database every 28 days, so I imagine that someone there might know.

This is the first I’ve heard of a step down fix not appearing as a waypoint, since we code them as such. I was talking to a Navy contractor today that alerted me to this. He was telling me that they teach students to use the baseline distance to the MAP as a proxy. That startled me a bit since those distances are not always precise.

 

[RandomGoat1248]

I haven't worried about RNAV in a while now so I am probably way off base, but the T-6B does not have anysort of VNAV capability as far as I remember. Do you have any other example of the fixes not showing up? Because if I had to guess I would assume that the system doesn't have points that only denote altitude stepdowns inside the FAF because the system is sequencing FAF->MAP.

Isn't this more an issue of the plate not correctly listing the distance to the MAP from JOHNC?

 

[kmac]

I haven't worried about RNAV in a while now so I am probably way off base, but the T-6B does not have anysort of VNAV capability as far as I remember. Do you have any other example of the fixes not showing up? Because if I had to guess I would assume that the system doesn't have points that only denote altitude stepdowns inside the FAF because the system is sequencing FAF->MAP.

Isn't this more an issue of the plate not correctly listing the distance to the MAP from JOHNC?

It could be the case that the chart needs to have a "3 NM to RW14", but I have yet to determine that. I also have not heard of other approaches that have this issue, but... it could not be isolated to just this one.

That's why I'm trying to find what data source the T-6B uses. I checked the coding and DAFIF has JOHNC in it, as a step down fix. I don't know if Jeppesen/Garmin/whatever the T-6B uses codes that waypoint.

VNAV is not relevant in this case since any step down fix beyond the glide path intercept point only applies to LNAV or Circling mins.

 

[kmac]

...And I just received an answer. The T-6B uses Jeppesen and, for whatever reason, Jeppesen does not code any step-down fixes. Apparently it has to do with the system being so old that there just isn't enough memory for the number of waypoints.

So with that said, good luck to everyone in Primary!

 

[sevenhelmet]

Glad you got an answer. Pretty much matches what I got from the OEM chief production pilot.