GPS Fix on an ILS Approach??

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godfreypilot

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godfreypilot
Well, I'm baffled.

They just made quite a few changes in the approaches at my local airport (SBP), namely, splitting the ILS/LOC 12 approach into separate approach plates: a ILS-12 and a LOC-12.

Now here's the catch: The OM, while still part of the LOC-12 approach, is no longer a component of the ILS-12. Instead, there is a GPS fix located at the glideslope intercept point (look at: http://155.178.201.160/d-tpp/1206/00989I11.PDF)

Now this is an ILS-12, not an ILS/RNAV-12. It doesn't say anything about GPS being required in the remarks section. So I'm assuming you could legally fly this without a GPS?

Seems pretty strange that there's no way of verifying the glideslope intercept point if you're flying a plane without a GPS unit (false glideslopes, anyone?).

So, has anyone seen anything remotely like this before that can maybe explain the thought process behind the change? Maybe I'm just behind the times a bit...
 
If you are referring to JAMPO, since no GPS is required (or not equipped) what the chart is trying to tell you is that you are at 6.9nm from the threshold when on the GS at 2400 feet.Typically when you are on the GS at 1000ft AGL you will be 3nm from the runway end.

José
 
Looks like another airport being prepped for a Marker Beacon-ectomy.
 
godfreypilot said:
They just made quite a few changes in the approaches at my local airport (SBP), namely, splitting the ILS/LOC 12 approach into separate approach plates: a ILS-12 and a LOC-12.
Click to expand...
They also renumbered them to runway 11.

Now here's the catch: The OM, while still part of the LOC-12 approach, is no longer a component of the ILS-12.
Click to expand...
That's typical. The FAA is slowly doing away with outer markers wherever they can on ILS approaches.

Instead, there is a GPS fix located at the glideslope intercept point (look at: http://155.178.201.160/d-tpp/1206/00989I11.PDF)

Now this is an ILS-12, not an ILS/RNAV-12. It doesn't say anything about GPS being required in the remarks section. So I'm assuming you could legally fly this without a GPS?
Click to expand...
Absoulutely. JAMPO is there purely for reference. The FAF is the glide slope intercept point, not JAMPO.

Seems pretty strange that there's no way of verifying the glideslope intercept point if you're flying a plane without a GPS unit (false glideslopes, anyone?).
Click to expand...
Well, at many airports, there's nothing at all out there, or maybe an NDB or the like. More and more, if you only have two VOR receivers for nav, there is no way to do that check. I guess DR and situational awareness are the keys to that, as well as making sure you intercept the GS from below, since there are no false GS lobes permitted below the real one, only above it.

So, has anyone seen anything remotely like this before that can maybe explain the thought process behind the change? Maybe I'm just behind the times a bit...
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As I said, the FAA is doing away with OM's wherever possible. And if you compare the two approaches, you'll see JAMPO is 0.8 nm farther from the approach end of the runway than the OM used as the FAF on the LOC 11 approach. I don't know where the GS intercept was before, since I don't have the old ILS/LOC chart, but it is now farther out and 100 feet higher than the FAF crossing altitude on the LOC 11 approach.
 
godfreypilot said:
Well, I'm baffled.

They just made quite a few changes in the approaches at my local airport (SBP), namely, splitting the ILS/LOC 12 approach into separate approach plates: a ILS-12 and a LOC-12.

Now here's the catch: The OM, while still part of the LOC-12 approach, is no longer a component of the ILS-12. Instead, there is a GPS fix located at the glideslope intercept point (look at: http://155.178.201.160/d-tpp/1206/00989I11.PDF)

Now this is an ILS-12, not an ILS/RNAV-12. It doesn't say anything about GPS being required in the remarks section. So I'm assuming you could legally fly this without a GPS?

Seems pretty strange that there's no way of verifying the glideslope intercept point if you're flying a plane without a GPS unit (false glideslopes, anyone?).

So, has anyone seen anything remotely like this before that can maybe explain the thought process behind the change? Maybe I'm just behind the times a bit...
Click to expand...

The policy is now to have the P-FAF for RNAV and ILS at the same location. A high percentage of airplanes now have LNAV. If not, the ILS is no different than many others that only mark the P-FAF with an altitude intercepting the GS. You would have to be 1,500 feet, or so, high to capture a false GS. If you fly the profile even close, there is no way that will happen.
 
Thanks on the correction on the runway number. It is, and always has been, runway 11. Silly of me to mess that up.

It sounds like is type of thing is far more common than I had realized. My instrument instructor told me to always verify the FAF with some means of navigation other than the glideslope intercept itself (where I trained, this was a VOR cross-radial). Guess that's no longer an option for me, and for an increasing number of pilots from what people have been saying.

Thanks all for the input!

Ryan
 
It's a really stupid move. MB transmitters are dead simple and hard to break. GPS has no backup system.
 
denverpilot said:
It's a really stupid move. MB transmitters are dead simple and hard to break. GPS has no backup system.
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But MB transmitters need to be maintained. I don't think it costs very much to create a GPS waypoint. Besides, as others have pointed out, identifying that waypoint isn't necessary in order to do the approach since GPS isn't required.
 
godfreypilot said:
It sounds like is type of thing is far more common than I had realized. My instrument instructor told me to always verify the FAF with some means of navigation other than the glideslope intercept itself (where I trained, this was a VOR cross-radial). Guess that's no longer an option for me, and for an increasing number of pilots from what people have been saying.
Click to expand...
As long as you have a clock and a compass, you still have a means to cross-check.
 
denverpilot said:
It's a really stupid move. MB transmitters are dead simple and hard to break. GPS has no backup system.
Click to expand...

That's not the point. The point is the FAA moved the ILS P-FAF to be at the same location as the RNAV P-FAF. This is what ATC has mandated.

If you cannot determine the GPS fix it makes no difference whatsoever for flying the ILS approach.

Marker Beacon transmitters are a relic of the low frequency radio range days. Did you get in on that gig? I did. :wink2: MBs are expensive to maintain and often difficult to get to for the FAA maintence folks.
 
aterpster said:
That's not the point. The point is the FAA moved the ILS P-FAF to be at the same location as the RNAV P-FAF. This is what ATC has mandated.
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And anyway, there's no way to ensure that your GS intercept at a particular indicated altitude will coincide with a GPS waypoint under all conditions, since indicated altitudes are barometric and barometric altitudes vary with temperature. If the GS crosses JAMPO at 2400 MSL, then on a warmer than standard day, when your altimeter reads 2400 your actual altitude will be higher, and so the P-FAF will be outside JAMPO. And the reverse for a colder than standard day... assuming I didn't get that backwards. :rolleyes:
 
denverpilot said:
It's a really stupid move. MB transmitters are dead simple and hard to break. GPS has no backup system.
Click to expand...

Depends on how you look at it. I look from the optimistic side of things. Considering that GPS picks up between eight to eleven satellites of the couple of dozen orbiting, and uses four or five of the best signals...........I'd consider that as a pretty good backup.

I'll take GPS anyday.

L.Adamson
 
L.Adamson said:
Depends on how you look at it. I look from the optimistic side of things. Considering that GPS picks up between eight to eleven satellites of the couple of dozen orbiting, and uses four or five of the best signals...........I'd consider that as a pretty good backup.

I'll take GPS anyday.

L.Adamson
Click to expand...


+1

Problem is a ton of librarians always look for why you can't. Should GPS have a backup? Sure, Europe and the Russians have their own systems. Want a backup? Put those systems is your plane.. FAA won't certify it? BS, I've seen those Antonovs in the US and guess what they use.
 
aterpster said:
Marker Beacon transmitters are a relic of the low frequency radio range days. Did you get in on that gig? I did. :wink2: MBs are expensive to maintain and often difficult to get to for the FAA maintence folks.
Click to expand...

That's the marketing spin for killing them anyway. Got a reference with real dollar/price numbers on it? I haven't seen one.

The human tech is already there on a regular basis to work on the ILS. Regular tests and calibration. The MB is a short drive away in most cases.

Anything non-NexGen just isn't "cool" anymore. The cool kids at FAA want to play with NexGen.

Just like any other tech company...
 
aterpster said:
Marker Beacon transmitters are a relic of the low frequency radio range days. Did you get in on that gig? I did. :wink2: MBs are expensive to maintain and often difficult to get to for the FAA maintence folks.
Click to expand...

Hey, when I got started there was still a 50-foot penalty for no middle marker.
Isn't going to be long as noted until they are gone entirely.

DME will be next. The military is already getting pretty lazy about fixing domestic TACANs when they die.
 
azure said:
And anyway, there's no way to ensure that your GS intercept at a particular indicated altitude will coincide with a GPS waypoint under all conditions, since indicated altitudes are barometric and barometric altitudes vary with temperature. If the GS crosses JAMPO at 2400 MSL, then on a warmer than standard day, when your altimeter reads 2400 your actual altitude will be higher, and so the P-FAF will be outside JAMPO. And the reverse for a colder than standard day... assuming I didn't get that backwards. :rolleyes:
Click to expand...

You are correct and that makes no difference to a safe ILS approach.
 
denverpilot said:
That's the marketing spin for killing them anyway. Got a reference with real dollar/price numbers on it? I haven't seen one.

The human tech is already there on a regular basis to work on the ILS. Regular tests and calibration. The MB is a short drive away in most cases.

Anything non-NexGen just isn't "cool" anymore. The cool kids at FAA want to play with NexGen.

Just like any other tech company...
Click to expand...

There are always contra-arguments. At my home airport, (KCRQ) they recently decommissioned the OM and installed a frequency-paired, collocated ILS DME. Much, much better in my view.

When the OM was in service I visited it one time. By road, it was about a 10 mile drive from the airport.

One of the first OMs to go was at KLAX in the late 1960s.. Thugs would shoot at the maintenance folks when they showed up to maintain it. The same happens for the lead-in lighting system at KJFK.
 
flyingron said:
Hey, when I got started there was still a 50-foot penalty for no middle marker.
Isn't going to be long as noted until they are gone entirely.

DME will be next. The military is already getting pretty lazy about fixing domestic TACANs when they die.
Click to expand...

What will remain are IMs.

DME isn't going anywhere soon. Critical civil DMEs will remain at many sites after the VORs are decommissioned. At least that is the present plan.

DMEs collocated with ILS will remain as long as the ILS does. For all I know KSBP is scheduled to get an ILS DME.
 
Ron Levy said:
They also renumbered them to runway 11.
Click to expand...

The FAA has been updating the MagVar tables. Actually, They probably have been right along and I never realized how much activity there was.

In some cases, they are looking ahead to what the correction is going to be in a couple years.

When I first came back to flying, MEM was on agonic line, now we're almost 30" west.

It affects some nav system data bases too, not sure exactly how.

We ran into a case at work where the FAA kicked the MagVar adjustment up so far (KANC) it may be causing problem with some nav systems (and there is a NOTAM).

After learning about it, It doesn't surprise me to see some runway magnetic headings are getting changed.
 
aterpster said:
My guess is that an ILS DME is being unboxed.
Click to expand...

For what purpose? If there's no need to determine JAMPO it doesn't matter if JAMPO is defined by DME, GPS, ADF, marker beacon, or a cross radial.
 
roncachamp said:
For what purpose? If there's no need to determine JAMPO it doesn't matter if JAMPO is defined by DME, GPS, ADF, marker beacon, or a cross radial.
Click to expand...

So they can get rid of the MB on the LOC IAP.

If JAMPO was mandatory on the ILS IAP, then it would either be ILS/RNAV or a note "GPS required." I don't see that, do you?
 
aterpster said:
So they can get rid of the MB on the LOC IAP.
Click to expand...

JAMPO isn't on the LOC IAP.

If JAMPO was mandatory on the ILS IAP, then it would either be ILS/RNAV or a note "GPS required." I don't see that, do you?
Click to expand...

No. I don't see any purpose at all for JAMPO on the ILS IAP. Do you?
 
roncachamp said:
JAMPO isn't on the LOC IAP.



No. I don't see any purpose at all for JAMPO on the ILS IAP. Do you?
Click to expand...

I checked into it further today. The 8260.19E order requires a G/S verification fix. I pointed out that makes the IAP ILS/LNAV.

One FAA said, "No it doesn't, if you don't have LNAV you just fly level at 2,400 to intercept the G/S."

Another FAA says, "They snatched defeat from the jaws of victory by using an LNAV WP."
 
aterpster said:
I checked into it further today. The 8260.19E order requires a G/S verification fix. I pointed out that makes the IAP ILS/LNAV.

One FAA said, "No it doesn't, if you don't have LNAV you just fly level at 2,400 to intercept the G/S."

Another FAA says, "They snatched defeat from the jaws of victory by using an LNAV WP."
Click to expand...

I'd say they're not following the order.
 
They didn't want to add a third cross-radial off of two different VORs to that mess? ;)
 
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