I press it when heading (usually in HDG mode) towards the LOC.
Then in intercepts the LOC and shows GS is awaited, then it intercepts the GS and there you go.
Any sort of auto intercept is a bit dodgy because you can have false localisers. These are well away from the real one; say 50 degrees off. But I’ve had it happen. So I set up the OBS mode to show a magenta line where the LOC is expected to be (OBS mode, plus the course pointer set to the LOC bearing) and then I can see where I am.
Then there is no LOC or GS. You fly it entirely in NAV mode and don’t touch anything (KLN94 and KFC225). APR is not used.
OK, I should have said LPV. Same question. There is a GS – albeit a synthetic one.
Peter wrote:
Then [GPS approach] there is no LOC or GS. You fly it entirely in NAV mode and don’t touch anything (KLN94 and KFC225). APR is not used.
Shouldn’t you use APR because of the added sensitivity of the CDI when flying an approach?
I don’t know the KFC225 logic for LPV. Do a search – multiple threads on the button sequence.
No; an IFR GPS auto selects 1nm FS in 30nm radius of the airport and then gradually reduces this to 0.3nm after the FAF. This is done in the GPS, not in the autopilot which has no idea where the airport is.
Peter wrote:
No; an IFR GPS auto selects 1nm FS in 30nm radius of the airport and then gradually reduces this to 0.3nm after the FAF. This is done in the GPS, not in the autopilot which has no idea where the airport is.
Exactly. That’s why I would expect you to use APR as the A/P has no means of automatically knowing that you have selected a navigation source which is more sensitive. The feedback loop in the A/P would need different parameters depending on the sensitivity of the CDI.
Actually an LPV (WAAS) acts as a funnel and narrows from 0.3 nm at FAF to around 350 feet at DA MApt
