Inverted ILS

[DFC]

NSEU, I would say IMHO your fig. B) confuses the issue, because a) you've drawn it upside down, whereas the pilot still sees it "right side up", and because b) the instrument indicates you're on the righthand side of the centreline, contrary to your "runway and plane" view.

No. I think that you have it wrong.

Forget the horizon for a moment. In both A and B the localiser indicates correctly that the aircraft is to the left of the centerline. The position of the aircraft has not changed from A to B and the indication has not changed either.

No look at the horizon in isolation.

Right way up - sky is near your head and ground is near your feet.

Roll the aircraft upside down and now the ground is near your head and sky near your feet.

A correctly represents the sky / ground position as you would see them during erect flight.

B correctly represents the sky / ground position as you would see them during inverted flight.

Perhaps it is easier for you to forget the ILS display on a horizon and think of the following -

If the final approach course is 270 degrees and the aircraft at A and B is on a heading of 270. With the course bar on the HSI set to 270, what will the picture be and how would that change if the aircraft rolled inverted?

The answer is that the heading will not change and that the HSI indication will not change either because the aircraft position relative to the centerline has not changed.

I said earlier that it is a pilot interpreted aid. It tells you where the aircraft is in relation to the centerline. Based on that you have to interpret how to get the aircraft back to the centerline and how to keep it there.

Banking the aircraft left or right does not get you back to the centerline - in the extreme all it does is fly you round in a circle.

What gets you back on the centerline is selecting an appropriate heading that will acheive that.

So assuming the final approach course is 270. Both the A and the B indications tell me that a track greather than 270 is required to regain the centerline.

If I am heading 270 and there is no wind, I may choose a new heading of 280.

Having decided to change my heading from 270 to 280, now for the first time I have to pay attention to the horizon position because the control inputs to acheive that are different in A and B.

Regards,

DFC