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IFR PIlots: KLN 94 Gotcha Flying RNAV GPS Y and Z Approaches

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Article on a problem that can get instrument pilots in trouble flying GPS approaches with the King/Bendix KLN 94 GPS. That's the GPS found in all Cessnas built from 1997 through much of 2004. Essentially the problem is that if you're flying an approach labeled with a Y or Z letter in the title, that letter does not show up in the list of approach titles when selecting an approach on the KLN 94. (www.maxtrescott.com) עוד...

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tdubose
Tony DuBose 0
Thanks for the post Max!!
amahran
amahran 0
So the difference between Y's and Z's is the minimum?
garymcginnis
Gary McGinnis 0
The Z approaches usually have lower minimums. That is the idea right from the FAAs mouth. Yet there are a few TERPS built approaches that do not conform. Another function is to differentiate between RNAV(GPS) and RNAV(RNP) approaches since official ATC terminology is cleared RNAV Z XX not cleared GPS XX. Usually Z is given to (RNP) approaches for the reason above.

Usually you will see a RNAV Y approach simply have LNAV MDA minimums and a published VDP while an RNAV Z approach will be basically the same but have LPV and LNAV/VNAV DAs along with LNAV and/or LP MDA minimums which are different than the Y approach. It also allows database coders to code all the approaches. I.E. RNAV Y 25 would be coded as RNVY25 what RNAV Z 25 would be coded as RNVZ25 allowing both approaches to be flown.

Hope that helps.
amahran
amahran 0
Okay and one more thing, I saw a Jeppesen Chart with the title "VOR Y or VOR Z runway XX" into Muscat, but the thing is, there was no way to identify which of the 2 ways to enter the approach was Y or Z. They were kind of 'merged' onto the same chart (an entry via a DME circle and an entry via a procedure turn) and the title said VOR Y and VOR Z

how do i differentiate between the 2 entries in this case?
garymcginnis
Gary McGinnis 0
Its a similar concept. Same approach just one IAF was via a DME/ARC and the other was via a procedure turn. One thing to note is Muscat Oman has approaches built by PAN OPS, which is different then TERPS.

Side note, I pulled up OOMS and that approach is not in the jepp database anymore.
amahran
amahran 0
let me see if i can pull one out of a simmer site, they normally have the outdated ones
amahran
amahran 0
HAHA oops it's not Muscat, it's apparently somewhere else.
Still trying to dig it up
amahran
amahran 0
My bad it's actually Fujairah
http://vatme.net/FILES/VATUAE/Downloads/Charts/OMFJ.pdf is the link

i think it's safe to say 11-1, 11-2, 13-1, and 13-2 are the ones that confuse me, as i have no way of telling of the DME arc is Y or Z, and the same goes for the Proced. turn
incase flightaware doesn't allow links, h t t p : / / v a t m e . n e t / F I L E S / V A T U A E / D o w n l o a d s / C h a r t s / O M F J . p d f
garymcginnis
Gary McGinnis 0
OK that is a simple one.

Always look for the ball flags and its associated data. Looking at 11-1 ILS Z 29 is for category A and B aircraft while ILS Y 29 is for category C and D. The difference is then between 11-1 and 11-2. Chart 11-2 is an entirely different ILS procedure with a different missed approach procedure as well. Chart 11-2 has lower minimums then 11-1 and one can assume the missed approach procedure for 11-2 makes a left turn towards lower terrain allowing planes to stay on the approach lower.

As to why the use letters to differentiate between the aircraft categories is weird since its the same procedure for all planes and all the published minimums are there for all categories.

The above is applicable with the 13- pages as well.

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