...for our friends from the UK..."standard ILS" = procedural ILS. ;-)
FWIW, it is possible that a key thing is whether the LOC is active at the time you press the button.
For example the KFC225 APR button should not be pressed until the EHSI deviation bar (showing the LOC) has moved off its "stop". If you press it too soon, it can turn towards the airport before the intercept or do something weird...
But with the old KI525 HSI you could press APR anywhere near the inbound track - even if facing the other way, which the Sandel EHSI prohibits because it detects it as BC (back course) which will be wrong for the current heading
What "active" means is subtle and possibly not documented anywhere.
However if hand flying, you can use your judgement - provided the system has correctly switched to the LOC mode.
Just throwing in some ideas...
When I bought my plane I flew around Kent at 5000ft, on autopilot, and played around with the kit. I could pick up Lydd's LOC from say 20nm away which was a good test.
Peter, the Avidyne exhibits similar behaviour to the Sandel and if you are too early you can end up tracking the back course which (if it say happens when intercepting the ILS in Koln as happened to me) can be embarrassing. With the G1000 I can have VNAV on overhead the beacon outbound and have armed the approach and it will fly the vertical steps then turn inbound using GPS mode with LOC and GS armed followed by an switch to VLOC and capturing the glideslope.
Another good example of the differences that can exist is between an LPV approach and an LNAV approach for which Garmin provides a synthetic glidepath. Without getting into the differences between these which have been well covered, on the G1000 I had a problem with it never capturing the glidpath in an LNAV+V. This was in spite of clearly being armed to do so (or so I thought).
On the Avidyne/DFC90/GTN650 combo these approaches flew exactly like an LPV approach. If a synthetic glidepath was available and APPR mode was armed it would capture and descend as if it was an LPV approach.
But the G1000/GFC700 combo has VNAV and treats a synthetic glidepath like any other VNAV profile. So while it can be armed (showing a white GS), the autopilot will never descend below the selected altitude in the PFD. Assuming you were in ALT HOLD mode prior, this would prevent a GS capture unless you had moved the selected ALT to say the MDA. If you are capturing an LPV or ILS however the indication is the same (other than LPV rather than LNAV in the CDI annunciator for the GPS approach), but the selected ALT makes no difference to the glidepath capture.
There are a lot of subtleties with these systems. So I agree with all of the above re the importance of getting to know them well before flying in proper IMC. And always being ready to step in if they are not doing what you think they should be doing. Usually, that is because you have programmed them incorrectly. But the poor documentation means that it is hard to know what "correct" is.
on the G1000 I had a problem with it never capturing the glidpath in an LNAV+V. This was in spite of clearly being armed to do so (or so I thought).
So... how can you fly at the platform altitude (say 2000ft) in ALT HOLD and then transition to an LNAV+V approach with an MDA of say 500ft?
There must be a brief time when you have to wind down the altitude preset from 2000 to 500, but from the instant you turn the knob to leave "2000" (the system shows "ALT ARM" or similar) and you are holding altitude purely on the internal barometer, not periodically checked against the altitude preselect. Over time it will drift...
This is digressing, I know... but I think it is hard to get one's head around this without actually understanding the avionics interconnections, which even most installers don't.
Once you are in ALT hold mode you are OK to select lower. It doesn't drift (in my experience). To expand, the altitude select bug does not change anything except the bug unless you are in an altitude capture mode ie VS, FLC etc.
I got the following from a 'pilot tips' website I subscribe to, specifically about the auto CDI switch function on the Garmin 430/530 from GPS to VLOC. (Doesn't seem to be relevant whether it's WAAS or not).
Clearly, the auto switch function has be set 'on' (which is on AUX p3 for both 430 and 530). And naturally the localiser frequency has to be the active nav!
Assuming that's ok, then there are two types of condition that will cause the auto switch not to work when you expect it to. The first is that to switch the FAF must be the active waypoint (so if you still have some step down fixes ahead of you, the CDI won't switch (yet) even though you're on the final approach course. But it will switch when the FAF becomes active.
The second failure point is that it will only switch in 'the box' - which measures 1.2nm either side of the FAC and from 15nm to 2 nm outside the FAF. So, if you're vectored to intercept the FAC within 2nm of the FAF, the CDI will never auto switch from GPS to VLOC. You should get a message from the Garmin, telling you to do it manually - but you might be a bit busy just then ...
Thank you, TJ.
I was flying an ILS - i was clearly inside the box - auto CDI was on - I was on the procedure turn and very close to the loc ...and one time i was even on the loc inbound to the FAF ...
... but it did not switch!
Remember it doesn't switch straight away as it gradually transitions. For how long did you let it run before intervening? I did a G1000 course online during which it was said sometimes people are too impatient and don't let it switch in its own time.
Ok, can't remember exactly ... but will try again! What's really a trap for the newcomer is that it's easy to forget to activate the approach... because it shows up on the GNS when it its only LOADED. But I did inot forget to activate it ...
By the way: If I go into the approach flight plan and select a point inside the approach and activate THAT leg, that means the approach itself IS activated ... right?
I wish I had a simulator of that configuration, but it doesn't exist.
Yes activate approach just is a direct to the initial fix in the loaded approach.
