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Oxford EGTK AIP: Auto-coupled approaches are not permitted (ILS glide-path is not suitable for auto-coupled approaches)

From Oxford AD entry and I come across this again,

AD2.EGTK.4 Instrument Approach Procedures: 2. Auto-coupled approaches are not permitted (ILS glide-path is not suitable for auto-coupled approaches)

I remember that coupled-ILS worked fine in DA40/DA42 (with GFC500/GFC700), the GP/GS modes worked fine on ILS, maybe it’s ‘GPS-aiding’?

I am looking for a trip down there and I am tempted to see if there is any difference using something like KAP140, has anyone tried before with old AP? very curious on auto-pilot behavior and nature of glide-path glitch and if one should degrade to LOC minima during planning

PS: it should work with ILS procedure loaded from database as LNAV+V, the pilot can always hand-fly or auto-pilot down to 200ft DH if he monitors LOC/GS deviation on 2nd CDI…

Last Edited by Ibra at 15 Jun 08:58
Paris/Essex, France, , United Kingdom

Radio telescopes one mile from threshold cause glide slope fluctuations. There is also a warning on the approach plates.

Last Edited by RobertL18C at 15 Jun 10:47
Oxford (EGTK), United Kingdom

So the GS will wiggle in last part near the ground at 300ft (AP gets disconnected by then) or it happens higher?

Why it affects GS and not LOC? they run on different frequencies but paid on one frequency

Paris/Essex, France, , United Kingdom

Ibra wrote:

Why it affects GS and not LOC? they run on different frequencies but paid on one frequency

They’re on different frequencies, the LOC is the frequency you set in the radio, the GP is somewhere in the lower 300mhz range. So I’m guessing the radio telescope does something that interferes with that 300mhz frequency range.

Netherlands

Thomas28 wrote:

So I’m guessing the radio telescope does something that interferes with that 300mhz frequency range.

That sounds like the only explanation, I will test GP on KAP140 next week and see if it slides all the way down on it, the AP has many problems of capturing LOC+GP on ILS already, even without issues with signal and it needs some babysitting, anyway, carefully watching an AP is not a bad thing (it can’t catch LOC above 120kts: needs NAV mode and can’t hook to GS from under: needs gentle pull up)

Paris/Essex, France, , United Kingdom

A single channel puddle jumper A/P. I think the KAP140 is CAT 1 approved, not sure my faith is strong enough.

Oxford (EGTK), United Kingdom

It’s CAT1 approved, it flies beautifully on LPV & ILS near 200ft DH (if speed is kept higher than 80kts otherwise goes crazy on pitch on the back of the curve and without auto-trim it will hand a surprise), it’s only hooking to LOC & GS near FAP on radar vectored ILS while flying faster cruise speeds: it does not get it, I have to drag it slowly and pull up to catch it

In the other hand, with GPS (LPV or ILS procedural overlay), KAP140 hooks nicely on LPV or LNAV+V near FAP/FAF, even at 160kts, not sure if it’s the CDI progressive scaling and sensitivity versus cruise & approach speeds? or if GPS signal has wide coverage and is smoother than ILS signal?

Last Edited by Ibra at 17 Jun 09:36
Paris/Essex, France, , United Kingdom
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