ILS instrument accuracy? Help......

[TripFarmer]

I'm just starting to work on my Instrument Rating and yesterday when doing an
ILS approach I was keeping the localizer centered and my instructor told me to
look up about a mile out. We were maybe 200 yards off the centerline. Next
one we stayed on the centerline (visually) and the needle was 1/2 deflection.

Any thoughts about what to do? It seemed like a practice ILS I did at another
airport didn't do this a couple of weeks ago. Could it be this one facility
(BHM)? Do I need an avionics shop to look at it?

I'm new at this so I'm not really sure what step to take next. Any help will
be appreciated.


Trip

[Roy Smith]

(TripFarmer) wrote:
> I'm just starting to work on my Instrument Rating and yesterday when doing an
> ILS approach I was keeping the localizer centered and my instructor told me
> to
> look up about a mile out. We were maybe 200 yards off the centerline. Next
> one we stayed on the centerline (visually) and the needle was 1/2 deflection.
>
>
> Any thoughts about what to do?

Get your radios checked?

[C J Campbell]

"TripFarmer" > wrote in message
...
| I'm just starting to work on my Instrument Rating and yesterday when doing
an
| ILS approach I was keeping the localizer centered and my instructor told
me to
| look up about a mile out. We were maybe 200 yards off the centerline.
Next
| one we stayed on the centerline (visually) and the needle was 1/2
deflection.
|
| Any thoughts about what to do? It seemed like a practice ILS I did at
another
| airport didn't do this a couple of weeks ago. Could it be this one
facility
| (BHM)? Do I need an avionics shop to look at it?
|

Could be your radios. Or if you have a GPS tied to your CDI you might have
inadvertently selected "GPS" instead of "NAV" and so the CDI needle was
actually indicating your position to some GPS course instead of the
localizer. I am seeing this error a *lot* in training.

[Ben Jackson]

In article >,
C J Campbell > wrote:
>
>Could be your radios. Or if you have a GPS tied to your CDI you might have
>inadvertently selected "GPS" instead of "NAV" and so the CDI needle was
>actually indicating your position to some GPS course instead of the
>localizer. I am seeing this error a *lot* in training.

What ACUs will allow you to select GPS display when a LOC frequency is
tuned in on the NAV? I know UPSAT's won't actually select the GPS until
you tune a normal VOR on the associated NAV.

--
Ben Jackson
>
http://www.ben.com/

[Dave Butler]

Ben Jackson wrote:
> In article >,
> C J Campbell > wrote:
>
>>Could be your radios. Or if you have a GPS tied to your CDI you might have
>>inadvertently selected "GPS" instead of "NAV" and so the CDI needle was
>>actually indicating your position to some GPS course instead of the
>>localizer. I am seeing this error a *lot* in training.
>
>
> What ACUs will allow you to select GPS display when a LOC frequency is
> tuned in on the NAV? I know UPSAT's won't actually select the GPS until
> you tune a normal VOR on the associated NAV.

I've seen UPS installs where that's true, and where that's not true. Apparently
it depends on how it's installed.

Remove SHIRT to reply directly.

Dave

[Teacherjh]

>>
We were maybe 200 yards off the centerline. Next
one we stayed on the centerline (visually) and the needle was 1/2 deflection.
<<

Perhaps the ILS transmitter is not on centerline? They can be offset, but I
don't know by how much.

The glide slope transmitter is often separate.

Jose

(for Email, make the obvious changes in my address)

[Ron Natalie]

"Teacherjh" > wrote in message ...

> Perhaps the ILS transmitter is not on centerline? They can be offset, but I
> don't know by how much.

Three degrees I think. And remember the localizer is at the far end of the
runway (on the front course).
>
> The glide slope transmitter is often separate.
>
It's always separate. The glide slope transmitter is down approximately
where the touchdown is (and obviously off to the side of the runway).

[Jeff]

I had a similar problem with my HSI, my nav receiver went through the RNAV then to
the HSI, my avionics shop told me the rnav was bad, they removed it and problem
solved.


TripFarmer wrote:

> I'm just starting to work on my Instrument Rating and yesterday when doing an
> ILS approach I was keeping the localizer centered and my instructor told me to
> look up about a mile out. We were maybe 200 yards off the centerline. Next
> one we stayed on the centerline (visually) and the needle was 1/2 deflection.
>
> Any thoughts about what to do? It seemed like a practice ILS I did at another
> airport didn't do this a couple of weeks ago. Could it be this one facility
> (BHM)? Do I need an avionics shop to look at it?
>
> I'm new at this so I'm not really sure what step to take next. Any help will
> be appreciated.
>
> Trip

[C J Campbell]

"Ben Jackson" > wrote in message
news:PeIab.524381$uu5.87404@sccrnsc04...
| In article >,
| C J Campbell > wrote:
| >
| >Could be your radios. Or if you have a GPS tied to your CDI you might
have
| >inadvertently selected "GPS" instead of "NAV" and so the CDI needle was
| >actually indicating your position to some GPS course instead of the
| >localizer. I am seeing this error a *lot* in training.
|
| What ACUs will allow you to select GPS display when a LOC frequency is
| tuned in on the NAV? I know UPSAT's won't actually select the GPS until
| you tune a normal VOR on the associated NAV.
|

The KLN-94 installation in all the new Cessnas has a NAV/GPS button which
must be pushed manually. The NAV/COM is a separate unit; you can tune in all
the localizers and VORs you want, but they will not be displayed on the CDI
unless you select NAV on the ACU.

[Stan Gosnell]

(Ben Jackson) wrote in
news:PeIab.524381$uu5.87404@sccrnsc04:

> What ACUs will allow you to select GPS display when a LOC
> frequency is tuned in on the NAV? I know UPSAT's won't
> actually select the GPS until you tune a normal VOR on the
> associated NAV.
>

With the installations we have, the HSI has no idea what's
selected, or what frequency. There's a push/push button, which
cycles between VOR & GPS, and the HSI just gets voltage from
whichever is selected. There is no logic at all to prevent
using either one. The nav radios and the GPS are completely
independent, and have no relation to each other in any way.

--
Regards,

Stan

[Peter Bondar]

The 'preferred' option is to have a loc frequency automatically force the
NAV/GPS switch to go to nav mode.


Almost all wiring suggestions imply that as the deafult mode.

So you barrel along with your gps upto the IAF cros tracking your favourite
VOR then swap frequencies
on nav1 and bingo your automatically lined for a loc intercept.

Personally I find it it irrating and also if P2 happens to tune the ILS/DME
for cross references
purposes and the A/P is on then you can do a beautiful intercept of the ILS
for an airfield you just
happen to be passing!!


Peter


"Stan Gosnell" > wrote in message
...
> (Ben Jackson) wrote in
> news:PeIab.524381$uu5.87404@sccrnsc04:
>
> > What ACUs will allow you to select GPS display when a LOC
> > frequency is tuned in on the NAV? I know UPSAT's won't
> > actually select the GPS until you tune a normal VOR on the
> > associated NAV.
> >
>
> With the installations we have, the HSI has no idea what's
> selected, or what frequency. There's a push/push button, which
> cycles between VOR & GPS, and the HSI just gets voltage from
> whichever is selected. There is no logic at all to prevent
> using either one. The nav radios and the GPS are completely
> independent, and have no relation to each other in any way.
>
> --
> Regards,
>
> Stan

[EDR]

In article >, TripFarmer
> wrote:

> I'm just starting to work on my Instrument Rating and yesterday when doing an
> ILS approach I was keeping the localizer centered and my instructor told me
> to
> look up about a mile out. We were maybe 200 yards off the centerline. Next
> one we stayed on the centerline (visually) and the needle was 1/2 deflection.

When was the last time the required VOR checks were performed?
This is an instrument requirement, isn't it?
Check your AFD for a VOT in your area.
If no VOT, perform and airborne check with two VOR receivers, if
installed.

[Ron Rosenfeld]

On Sat, 20 Sep 2003 16:24:18 GMT, EDR > wrote:

>When was the last time the required VOR checks were performed?

That check does not verify the accuracy of the localizer and/or glide path
receivers in the unit.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Robert Moore]

EDR > wrote
>
> When was the last time the required VOR checks were performed?
> This is an instrument requirement, isn't it?
> Check your AFD for a VOT in your area.
> If no VOT, perform and airborne check with two VOR receivers, if
> installed.

VOR checks have nothing to do with LOC accuracy. Two separate
receivers sharing the same tuning head and CDI.

Bob Moore

[EDR]

In article >, Robert
Moore > wrote:
> VOR checks have nothing to do with LOC accuracy. Two separate
> receivers sharing the same tuning head and CDI.

So what happens when both nav's are dialed in to the same localizer
frequency?
Do the indicators read the same?
Or is there a difference?
Which one yields a more accurate track?

[Ron Rosenfeld]

On Sat, 20 Sep 2003 23:31:56 GMT, EDR > wrote:

>In article >, Robert
>Moore > wrote:
>> VOR checks have nothing to do with LOC accuracy. Two separate
>> receivers sharing the same tuning head and CDI.
>
>So what happens when both nav's are dialed in to the same localizer
>frequency?
>Do the indicators read the same?
>Or is there a difference?
>Which one yields a more accurate track?

If you are interested in doing a flight check of your LOC and GP receivers,
the procedure is outlined in AC91-16.

But to just check the accuracy of the LOC & GP receivers and indicators
systems, I would do a portion of the test which consists of flying directly
over the OM at the GP intercept altitude, and at approximately a 45° to the
LOC course. The GP needle should go from full up to full down deflection;
and the LOC & GP needles should be centered when passing over the OM.

This procedure does not check the LOC flag alarms or deviation sensitivity,
but if it's grossly abnormal, it is additional evidence that the unit
should be bench-checked.



Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Stan Gosnell]

"Peter Bondar" > wrote in
:

> The 'preferred' option is to have a loc frequency
> automatically force the NAV/GPS switch to go to nav mode.

Well, maybe preferred by some, but I may want to tune in the
localizer while I'm a long way out, getting ready for the
approach, but navigating on GPS until I'm inbound, or at least
on vectors. Forcing VOR mode just because a localizer is tuned
is simply a stupid way to do things.

--
Regards,

Stan

[Ben]

Which approach was it, 24 or 06?
My last approaches at BHM seemed to be spot-on, except for pilot induced
variation of course. (about 3 mo ago for 6, 2 mo for 24 in heavy smoke).

Ben
N26RR
KBHM

>
> Any thoughts about what to do? It seemed like a practice ILS I did at
another
> airport didn't do this a couple of weeks ago. Could it be this one
facility
> (BHM)? Do I need an avionics shop to look at it?
>
> I'm new at this so I'm not really sure what step to take next. Any help
will
> be appreciated.
>
>
> Trip
>


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[EDR]

In article >, Ron Natalie
> wrote:
> > The glide slope transmitter is often separate.
> It's always separate. The glide slope transmitter is down approximately
> where the touchdown is (and obviously off to the side of the runway).

Not only is the G/S transmitter separate, the signal is bounced off the
ground from the transmitter toward the approach end of the runway. That
is why TERPS requires a specified distance of flat empty ground ahead
of the runway threshhold.

[Maule Driver]

"Stan Gosnell" > wrote in message
> > The 'preferred' option is to have a loc frequency
> > automatically force the NAV/GPS switch to go to nav mode.
>
> Well, maybe preferred by some, but I may want to tune in the
> localizer while I'm a long way out, getting ready for the
> approach, but navigating on GPS until I'm inbound, or at least
> on vectors. Forcing VOR mode just because a localizer is tuned
> is simply a stupid way to do things.
>
Agreed. My Garmin 300XL is setup to force the switch and it is a procedural
pain for approaches with with course reversal.

And if you switch to NAV mode while GPS is in Hold mode, the moving map goes
a bit crazy (I guess it's looking to the indicator for intended direction
info but it's been disco'd).

May be time to go back and have it configured to 'non-preferred' mode.