GPS approaches

B

buffalopilot

Well-Known Member
I was out flying with a flight instructor friend last night and we were shooting a GPS approach with Vectors to final selected in the Garmin 430. We were vectored inside the final approach fix and the garmin did not cycle to the final leg, it stayed on the leg outside the FAF, any information on why this happened?
 
buffalopilot said:
I was out flying with a flight instructor friend last night and we were shooting a GPS approach with Vectors to final selected in the Garmin 430. We were vectored inside the final approach fix and the garmin did not cycle to the final leg, it stayed on the leg outside the FAF, any information on why this happened?
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Perhaps you should've selected "Activate Vector to Final mode" which would've only had the last leg in there...
 
buffalopilot said:
...We were vectored inside the final approach fix...
Click to expand...

I didn't think controllers were allowed to vector inside the FAF. Are you sure the controller didn't screw up and put you in too tight?

If that is the case, maybe the GPS thought you were getting vectored to the other side of final or something.

If only I had a quarter for every time I said, "Ok, why is it doing that?" to a GPS...
 
I thought the same thing, i thought they had to vector outside the FAF, i believe the gps gets confused if they dont do this.
 
I think you have to cross the FAF - within 2 miles of the FAF the CDI sensitivity will scale down to 0.3 (go with me on this, it's something like that) so if you don't at least get outside the FAF within 2 miles it won't scale and the GPS won't sequence the approach.

It cetinaly SHOULDN'T sequence the approach, just as the controller SHOULDN'T have had you join final inside the FAF - inside the gate is one thing, inside the FAF is something else.
 
The .3 sensativity should activate weather you are sequenced on final or not. The GPS changes to terminal mode within 30 NM of the airport and then to approach mode when 2 miles from FAF. I believe the sensativity is based on your position from the missed approach point no matter where you are if you have the approach activated in the GPS.

I don't know what the rules are on vectoring for GPS approach, but I think you could have sequenced properly by hitting the OBS button. i don't know for sure as I have never shot one from inside the FAF

There's a lot of good information in the AIM and Garmins website about this stuff..
 
I would agree with everyone else that it was probably because you where inside the FAF. However, I do know that the 430 doesnt always sequence into approach mode if you are close to the FAF and turning away from the approach course at a certain rate or degree. Im assuming that the GPS thinks you are no longer shooting the approach since you are turning away from your course, therefore it wont activate.
 
If outside the FAF, you didnt "Activate" the vectors to final, you just selected Load. Unless you hit the CDI button, which would have prevented it from flipping after the FAF. It wont load the final leg of the approach if you are inside the FAF. It wouldnt be a proper approach. Dont be scurred to use the white line as your reference (as opposed to the pink). If you are using a single stack 430, just flip it over to the CDI screen. Itl still give you runway allignment. Ive been using the 430 for a few years now, so Im pretty familiar with its operations. shoot me over a PM if you have any more questions
 
FlyingNole said:
If outside the FAF, you didnt "Activate" the vectors to final, you just selected Load. Unless you hit the CDI button, which would have prevented it from flipping after the FAF. It wont load the final leg of the approach if you are inside the FAF. It wouldnt be a proper approach. Dont be scurred to use the white line as your reference (as opposed to the pink). If you are using a single stack 430, just flip it over to the CDI screen. Itl still give you runway allignment. Ive been using the 430 for a few years now, so Im pretty familiar with its operations. shoot me over a PM if you have any more questions
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???

"It wouldn't be a proper approach" - O.K., I'll go along with that, but then you turn around and say: "Dont be scurred to use the white line as your reference (as opposed to the pink). If you are using a single stack 430, just flip it over to the CDI screen. Itl still give you runway allignment." Now I'm confused. You aren't saying to "use the white line" during a GPS approach, are you???
 
So did you guys just go into the Flight Plan and activate the FAF to RWY leg? Did it give you .3 sensitivity when you did it?
 
SteveC said:
???

"It wouldn't be a proper approach" - O.K., I'll go along with that, but then you turn around and say: "Dont be scurred to use the white line as your reference (as opposed to the pink). If you are using a single stack 430, just flip it over to the CDI screen. Itl still give you runway allignment." Now I'm confused. You aren't saying to "use the white line" during a GPS approach, are you???
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Well if you are in actual IMC, then you would have to go missed because you arent properly established on the approach in the first place. I was talking about using the white line,etc for reference ONLY for allignment. If the GPS isnt displaying the proper leg, then you cant safely shoot the approach anyway. If you are trying to practice a true GPS/RNAV approach, turning inside the FAF isnt proper, and you should declare a missed and request vectors that turn you outside the fix. When Ive shot them in IMC, most controllers will give you a heading that intercepts an IAF (looks like the base leg of the pattern), and the GPS will sequence each leg. Sorry if I was confusing ya before.
 
I happened to be the safety pilot on that flight with Buffalopilot, and everything seemed pretty cool up until the point the control gave us vectors that IMHO screwed up the approach. He had everything set up cool, approach activated, and we initially had vectors that were taking us directly to the FAF. Then the controller gives us vectors that pointed us directly at the end of the runway, which in turn turned us inside the FAF. Seemed like he just didn't want to deal with us, the vectors he gave for the most part just negated the entire GPS approach. If we would have continued on the assigned vectors we would have never intercepted the final approach course, instead it would have taken us directly to the end of the runway at a weird angle. I was kind of pissed because we didn't need vectors to the runway, we needed vectors so we could practice th approach, and it pretty much just ended up wasting our time and $$$.
 
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