ILS reception question

[gatt]

Anybody ever seen intermittent ILS localizer reception during multiple
missed approaches?
What causes that?

Was doing ILS localizer and back course approaches at McNary (Salem) last
night in solid IMC. That was a blast, until the third approach. We hit the
intersection at the right altitude, but couldn't get a solid enough needle
reading to complete the approach.

That's kind of a rush, when you lose radio navigation and you're in the
middle of a freakin' cloud. Seattle Center vectored us to VFR and all was
fine, but my instructor said she'd seen that happen at that particular
approach maybe a half dozen times, in as many airplanes. We've had NO
trouble with reception in that particular aircraft anywhere else, so it
looks like a transmission problem. What causes that, to whom can we report
it who will take it seriously, and is this common?

The flight home was pure Kodak. Vectored us to 6,000 feet which was the
overcast top and found outselves right on top of that layer with another
layer over us, and the setting sun right in between.

-c

[EDR]

In article >, gatt
> wrote:

> Anybody ever seen intermittent ILS localizer reception during multiple
> missed approaches?
> What causes that?

Not sure about the localizer, but glideslope can be affected. I will
have to pull out my copy of TERPS to check.
Was there an aircraft parked somewhere in the runway environment
(beyond the hold-short line) between you and the the ILS antennas?
The glideslope signal is reflected off the flat ground between the
antenna and the runway threshhold. Hold-short lines on the taxiways are
placed far enough back from the runway that an aircraft in the runup
area will not interfer with the glideslope signal.

[gatt]

"EDR" > wrote in message news:100620041637580530%

> Was there an aircraft parked somewhere in the runway environment
> (beyond the hold-short line) between you and the the ILS antennas?
> The glideslope signal is reflected off the flat ground between the
> antenna and the runway threshhold. Hold-short lines on the taxiways are
> placed far enough back from the runway that an aircraft in the runup
> area will not interfer with the glideslope signal.

Shouldn't have been. It was right after tower closed for the evening and
the only other aircraft reporting was a National Guard helicopter taxiing
for closed traffic (IFR minimums...low clouds/fog) We had the glidescope,
just not the localizer needle. And we had it on the first approach as well
as on the back course loud and clear. Was just that one time, and it came
around right as I called for missed approach, but that wasn't until I'd
passed the outer marker (I was already climbing out by then. )

We were there. Followed the needle out, did the procedure turn, came back
around, picked up the needle again and the right before the outer marker it
just blipped out and we got nothing.

Given the IMC conditions we didn't ask to be vectored to try again, but it
was a great learning experience anyway.

-c

[EDR]

In article >, gatt
> wrote:

I wonder if the helicopter was doing its approach in the path of the
localizer antenna?

> "EDR" > wrote in message news:100620041637580530%
> > Was there an aircraft parked somewhere in the runway environment
> > (beyond the hold-short line) between you and the the ILS antennas?
> > The glideslope signal is reflected off the flat ground between the
> > antenna and the runway threshhold. Hold-short lines on the taxiways are
> > placed far enough back from the runway that an aircraft in the runup
> > area will not interfer with the glideslope signal.
>
> Shouldn't have been. It was right after tower closed for the evening and
> the only other aircraft reporting was a National Guard helicopter taxiing
> for closed traffic (IFR minimums...low clouds/fog) We had the glidescope,
> just not the localizer needle. And we had it on the first approach as well
> as on the back course loud and clear. Was just that one time, and it came
> around right as I called for missed approach, but that wasn't until I'd
> passed the outer marker (I was already climbing out by then. )
>
> We were there. Followed the needle out, did the procedure turn, came back
> around, picked up the needle again and the right before the outer marker it
> just blipped out and we got nothing.
>
> Given the IMC conditions we didn't ask to be vectored to try again, but it
> was a great learning experience anyway.
>
> -c

[gatt]

"EDR" > wrote in message news:100620041919505739%

> I wonder if the helicopter was doing its approach in the path of the
> localizer antenna?

That's very possible. He was doing closed traffic, but for a helicopter in
that kind of weather it was probably a very tight pattern which would
explain how the needle would come alive and then just as suddenly go dead.

-c

[BTIZ]

I once flew a Piper Arrow.. that the ILS would be intermittent depending on
gear configuration.. or loose it in a turn.. we figured the nose gear was
blocking a belly antenna.. but it was not consistent

BT

"gatt" > wrote in message
...
>
> Anybody ever seen intermittent ILS localizer reception during multiple
> missed approaches?
> What causes that?
>
> Was doing ILS localizer and back course approaches at McNary (Salem) last
> night in solid IMC. That was a blast, until the third approach. We hit
the
> intersection at the right altitude, but couldn't get a solid enough needle
> reading to complete the approach.
>
> That's kind of a rush, when you lose radio navigation and you're in the
> middle of a freakin' cloud. Seattle Center vectored us to VFR and all was
> fine, but my instructor said she'd seen that happen at that particular
> approach maybe a half dozen times, in as many airplanes. We've had NO
> trouble with reception in that particular aircraft anywhere else, so it
> looks like a transmission problem. What causes that, to whom can we
report
> it who will take it seriously, and is this common?
>
> The flight home was pure Kodak. Vectored us to 6,000 feet which was the
> overcast top and found outselves right on top of that layer with another
> layer over us, and the setting sun right in between.
>
> -c
>
>

[Roy Smith]

In article >,
"gatt" > wrote:

> "EDR" > wrote in message news:100620041637580530%
>
> > Was there an aircraft parked somewhere in the runway environment
> > (beyond the hold-short line) between you and the the ILS antennas?
> > The glideslope signal is reflected off the flat ground between the
> > antenna and the runway threshhold. Hold-short lines on the taxiways are
> > placed far enough back from the runway that an aircraft in the runup
> > area will not interfer with the glideslope signal.
>
> Shouldn't have been. It was right after tower closed for the evening and
> the only other aircraft reporting was a National Guard helicopter taxiing
> for closed traffic (IFR minimums...low clouds/fog)

Didn't have to be an aircraft. Could have been anything big and metal.
Like a truck. Or a tractor mowing the grass (but I suspect they don't
mow the grass late at night). But why are you so sure it wasn't the
chopper?

You might want to file a NASA report if you can't find anybody else
interested in listening.