A Slingsby Firefly did indeed fly an inverted ILS approach into Benson donkey's years ago, with the GodFather (or, if you will, GodUncle) of British Aerobatics in command. Well before my time, but, as has been outlined above, the localiser does work in the correct sense.

Well I have learnt the square root of FA.

Quote;

"The very best in practical technical discussion on the web":ugh::ugh::ugh:

Seems to me that this issue has still not been resolved. Some are saying opposite sense, others are saying same sense. Some say the LOC will vary from the GS.

The ILS system is based on "depth of modulation" and instruments are designed to show deviation from the ILS centreline using this depth of modulation. If you're flying on the left of the Loc, your loc pointer will command you to fly to your relative right irrespective of which way up you are (assuming the ILS pointers are not biased out of view at large roll angles)

Inverted, if you roll to your relative right, which way does your aircraft go? Unfortunately, drawing your instrumentation on a piece of paper and inverting it would seem to suggest that if you flew towards the needle, you would fly further away from the centreline. In this respect, it's opposite sense. However, it's probably more a question of aerodynamics. If you're upside down and turn the wheel right, will you fly away from or to the Loc centreline?

Rgds.
NSEU (not a pilot)

The localiser system provides the pilot with position information relative to the extended centerline. It tells the pilot if they are on, left or right of the extended centerline.

If the aircraft is left of the centerline and performs a loop over a point on the ground the indication of position relative to the extended centerline will not vary - nor will the indication.

Similarly the Glideslope provides the pilot with position information relative to an imaginary surface starting at the touchdown point and set as thre approach angle.

If the aircraft is above the glideslope and performs a slow roll then the glideslope indication will not move - nor will the indication.

The important thing to remember here is that we are talking about a pilot interpreted aid to navigation.

The indications always say the same thing - upright or inverted since the position of the aircraft relative to the centerline and approach slope have not changed and therefore the way that the aircraft (as an object) has to travel to regain the centerline (which is a vertical plane) and/or glideslope (which is a plane set at a specific angle) has not changed.

As in other aspects of inverted flight, if one imagines onself sitting upright on the underside of the aircraft and moves the controls appropriately, then imagine what that would happen with the end of the stick and rudder pedals you are holding while hanging upside down.

Regards,

DFC

"in a galaxy far, far away - I was involved in this very exercise. Not, I hasten to add, in a transport category aircraft but a suitable steed"

I think you are incorrect - a Galaxy must fall into the category of transport aircraft.

True.

http://www.ozemail.com.au/~b744er/UpsideDown.GIF

NSEU,
I think you're confusing the issue...

The centreline is on your 'right'.

In normal flight, A) is what you see, and your starboard wing is pointing towards the centreline.
You now bank by dropping your starboard wing to fly towards the centreline.

In inverted flight, A) is still what you see, since both your head and the instrument are upside down.
But with your port wing now pointing towards the centreline, you drop your port wing to bank and fly towards the centreline.

Never having tried it myself, I now take BizJetJock's and Bullethead's words for it, that you do this automatically, i.e., the instrument tells you to bank to the right, and even if you're upside down, your brain tells you that "right" is relative to the ground, so you now drop your port wing to bank to the right and hence curve your flightpath to the right relative to the ground.

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.

CJ

When you're inverted your ailerons appear to work in the reverse sense, e.g, if you want to turn left you must push the stick right. The localiser also works in the reverse sense when inverted, the two reversals cancel each other so from the pilots perspective it works in the correct sense. The G/S will be reversed though.

Fully correct Christiaan..:ok:

As DFC has said, no I haven't drawn it upside down. It's the pilot's view. Only the horizon changes in this situation. ILS instruments don't know that you have changed orientation, so the pointer remains in the same position on the instrument.

(Edit) Think of ILS displays as colour and volume. Colour (traditionally blue&yellow) is aircraft position, right or left of the centreline. Volume is distance from the centreline. Neither has changed by inverting the aircraft, so the displays remain the same (as presented to the pilot).

And then there ws the famous request to tower for a "gear up" low and over
:}

The display in NSEU’s post 26 is correct. The bars indicate the position of the C/L relative to the A/C. Fly to the bar.
In the diagram, the A/C is to the left of C/L in both cases and the indicator displays this. The problem is it was to the pilots right side, it is now to the pilots left side as the pilot interprets it (pilot being inverted) but still to the right of the A/C. :}
The same will happen to G/S, it will display relative to the A/C, so if the G/S C/L is below the A/C initially, when inverted it is still below the A/C but displayed in the indicator into the blue. Bars are not dependent of the ball orientation.

To give some credence to this, when ground testing it does not matter where the test set antenna is located, above, below, left or right of the A/C it is the signal strength of the individual LOC & GS frequencies emitted by the test set that determines where the bars indicate.