TLAs hurt my head

[silver-eagle]

Explain, if you can, the difference between a localizer directional aid (LDA), a LOCalizer, and an Instrument Landing System (ILS).
And while we're at it, it seems the Non direction beacons (N D B) are being phased out. I have a BK 89B GPS (approach certified). Since I can program the NDB approach into it, can I legally fly the NDB approach IF said NDB is out of service.

 

[Skip Miller]

Explain, if you can, the difference between a localizer directional aid (LDA), a LOCalizer, and an Instrument Landing System (ILS).

A Localizer provides horizontal course guidance to a runway threshhold.

A LDA gives horizontal course guidance that does NOT terminate at a runway threshhold. The one I am familiar is the LOC-A approach to LaGuardia, where the LDA lines you up properly to make the turn to final. So you turn final and then tune in the localizer for the next phase of the approach.

An ILS is a localizer plus a glide slope signal to provide vertical guidance.

-Skip

 

[HPNPilot1200]

An ILS is a localizer plus a glide slope signal to provide vertical guidance.

-Skip

Some LDA approaches utilize glideslopes as well, which you can identify by noting the the approach minimums (S-LDA/GS).

LDA's are offset localizer approaches in essence, while ILS systems use localizer antennas that are not offset from the runway extended centerline. Most LDA's don't incorporate glideslopes, but there are approaches out there that do.

 

[vontresc]

While we are on the subject of Aviation TLAs what the hell does BFO mean???? It has been bugging me for sometime as everytime I get into 41E and play with the ADF I cannot figure out what that switch does on the ol AM radio.

 

[KennyFlys]

While we are on the subject of Aviation TLAs what the hell does BFO mean???? It has been bugging me for sometime as everytime I get into 41E and play with the ADF I cannot figure out what that switch does on the ol AM radio.

BFO: Beat Frequency Oscillator

It's used to establish an audio frequency when one would not otherwise be heard. I think I have that right. It's been a while!

 

[jmaynard]

While we are on the subject of Aviation TLAs what the hell does BFO mean???? It has been bugging me for sometime as everytime I get into 41E and play with the ADF I cannot figure out what that switch does on the ol AM radio.

That's not an aviation TLA, but a radio TLA. A BFO is used to make a dead carrier wave audible. There's no need to use it at any navaid in the US I'm aware of, since they don't use dead carriers (they're all modulated with the ID tone), but I've read that some navaids elsewhere int he world key the carrier on and off to identify, and have no other modulation; the BFO is needed to make those audible.

If you have the BFO on on an NDB with just the Morse code identifier, you'll hear a tone besides the identifier. That tone is the carrier being made audible by the BFO.

 

[Skip Miller]

While we are on the subject of Aviation TLAs what the hell does BFO mean???? It has been bugging me for sometime as everytime I get into 41E and play with the ADF I cannot figure out what that switch does on the ol AM radio.

That does make it an old radio. From Wiki:

A beat frequency oscillator or BFO in radio telegraphy, is a dedicated oscillator used to create an audio frequency signal from carrier wave transmissions to make them audible, as they are not broadcast as such. The signal from the BFO is then heterodyned with the intermediate frequency signal to create an audio frequency signal.

All that means is that if you can't hear the code signal, try flipping the BFO switch.

-Skip

 

[flyingcheesehead]

Explain, if you can, the difference between a localizer directional aid (LDA), a LOCalizer, and an Instrument Landing System (ILS).
And while we're at it, it seems the Non direction beacons (N D B) are being phased out. I have a BK 89B GPS (approach certified). Since I can program the NDB approach into it, can I legally fly the NDB approach IF said NDB is out of service.

LDA is a localizer that isn't aligned closely enough with a runway to be a LOC approach. A LOCalizer is like an ILS but with no vertical guidance. An ILS is like a localizer with vertical guidance. (Like the circular reference? )

Examples:

LDA to a runway (note the angular offset): LDA 2 HFD
LDA not to a runway: LDA-A VUO and the aforementioned LDA-A LGA

Also, there's the SDF (Simplified Directional Facility) which is like a localizer but less accurate (IIRC, 6-12 degrees). A fairly close to home example is the SDF 2 ISW.

Most of these approaches are going the way of the dodo bird even faster than the NDB's are.

As for the NDB - If the approach plate says "NDB or GPS" you can fly it with the 89B, assuming your installation is approach certified. If not, you cannot fly it with the 89B (and it should say so if you try).

Can be flown with GPS: NDB or GPS 23 RYV
Can't be flown with GPS: NDB 5 RYV

 

[HPNPilot1200]

As for the NDB - If the approach plate says "NDB or GPS" you can fly it with the 89B, assuming your installation is approach certified. If not, you cannot fly it with the 89B (and it should say so if you try).

...and the procedure (IOW, GPS overlay) exists in the current database on the 89B.

 

[Everskyward]

LDA's are offset localizer approaches in essence, while ILS systems use localizer antennas that are not offset from the runway extended centerline. Most LDA's don't incorporate glideslopes, but there are approaches out there that do.

Here's an LDA with glideslope where the final approach course is pretty much aligned with the runway. This is actually a pretty new approach for this airport.

LDA/DME RWY 25 KEGE

 

[flyingcheesehead]

Here's an LDA with glideslope where the final approach course is pretty much aligned with the runway. This is actually a pretty new approach for this airport.

LDA/DME RWY 25 KEGE

Interesting approach. I'm not sure why it's not an ILS - It's not offset by much (3 degrees), we have an ILS at MSN that's offset by more IIRC. The minimums are really high, as is the climb gradient on the missed. Would that do it?

What confuses me is that the straight-in minimums are with the glideslope are 8330-2 but it says "For LDA/GS fly visual to airport 246 - 4.3nm. For LDA fly visual to airport 246 - 2nm." That segment starts at CIPKU, 2nm from the runway, so it appears that they're saying to fly visually PAST the airport for a straight-in approach? I don't get it.

 

[mantakos]

That segment starts at CIPKU, 2nm from the runway, so it appears that they're saying to fly visually PAST the airport for a straight-in approach?

The profile view, as drawn, seems to "imply" that the glideslope crosses CIPKU at about DA, but a 3.8 degree glideslope is 1790' high about 4.4 miles out. So I think that if you're coming down the glideslope, you hit DA a little over 2 miles before CIPKU.

What I'm a little confused about is that if the DA is reached 4 miles out, how come the visibility requirements are 2 miles?
-harry

 

[poadeleted20]

Explain, if you can, the difference between a localizer directional aid (LDA), a LOCalizer, and an Instrument Landing System (ILS).

In addition to what the others said, all three use the same localizer transmission system -- same lateral sensitivity, same antenna array, etc. The only difference is where they put the antenna array in relation to the runway. The other system that kinda looks like a LOC/LDA is the SDF, which as noted has a 6-12 degree wide course, and may be either aligned with the runway like a LOC or off alignment like a LDA.

And while we're at it, it seems the Non direction beacons (N D B) are being phased out. I have a BK 89B GPS (approach certified). Since I can program the NDB approach into it, can I legally fly the NDB approach IF said NDB is out of service.

If it's a plain NDB approach, you are only authorized to fly that approach with both the NDB on the ground and the ADF in your aircraft operational. If it's an "NDB or GPS" approach, you can fly it off the GPS (assuming the database is current and the approach is loaded) even if the NDB is off the air or you have no working ADF in the plane. The key is that GPS is not authorized as the sole source for tracking the final segment of an approach which doesn't have "GPS" in its title.

This used to be clear in AIM 1-2-3c, but for reasons comprehensible only to the FAA bureaucratic mind, they dropped the clarifying statement from the Aug 08 version of the AIM in advance of publication of the new AC 90-94A where that statement is being moved, and where it eventually will be (whenever the new version of that AC gets published). I confirmed that this week with AFS-470, which is responsible for that portion of the AIM and AC 90-94.

 

[poadeleted20]

Interesting approach. I'm not sure why it's not an ILS - It's not offset by much (3 degrees), we have an ILS at MSN that's offset by more IIRC. The minimums are really high, as is the climb gradient on the missed. Would that do it?

IIRC, the runway alignment requirement for an ILS (0.6 degrees, I think) is tighter than for a LOC (30 degrees) to be published with straight-in landing mins.

What confuses me is that the straight-in minimums are with the glideslope are 8330-2 but it says "For LDA/GS fly visual to airport 246 - 4.3nm. For LDA fly visual to airport 246 - 2nm." That segment starts at CIPKU, 2nm from the runway, so it appears that they're saying to fly visually PAST the airport for a straight-in approach? I don't get it.

The ILS MAP (where the GS intercepts the DH) is almost always passed before the LOC MAP (usually the runway threshold). In this case, with the DH of 1790 above the runway, you're going to reach the GS MAP a very long way out (4.3 nm from the threshold), well outside the LOC MAP (the 3.5 DME fix, which is two miles from the runway threshold).

Just remember that as with many nonprecision approaches, if you spot the runway right at the MAP doing the LOC-only approach, you'll be two miles from touchdown at over 2000 feet above the runway, and losing over 1000 ft/nm is a bit of a tricky proposition unless you're flying a helicopter or a Bell 609. Although they don't give a VDP, my feeling is that if you're running LOC-only and don't spot the runway by about five miles from the airport, you're pretty well hosed.

 

[Dan Thomas]

That's not an aviation TLA, but a radio TLA. A BFO is used to make a dead carrier wave audible. There's no need to use it at any navaid in the US I'm aware of, since they don't use dead carriers (they're all modulated with the ID tone), but I've read that some navaids elsewhere int he world key the carrier on and off to identify, and have no other modulation; the BFO is needed to make those audible.

If you have the BFO on on an NDB with just the Morse code identifier, you'll hear a tone besides the identifier. That tone is the carrier being made audible by the BFO.

It's also used in shortwave communications. Single-Sideband (SSB takes the full-wave modulated carrier and snips off everything on the top or bottom of the neutral line (upper or lower sideband) and the remaining is transmitted. At the receiver the operator turns on the BFO and adjusts its frequency to make the speaker's voice sound normal. The idea is to fill in the missing waves. I think the basic reason for SSB was to allow two conversations on the same frequency.
And that's as I remember it from my DSL days. A long time ago. Still have a receiver but it gets used maybe once a year. Not much of interest on the amateur bands, just like RAP.

Dan

 

[flyingcheesehead]

IIRC, the runway alignment requirement for an ILS (0.6 degrees, I think) is tighter than for a LOC (30 degrees) to be published with straight-in landing mins.

It's not 0.6 degrees, as we have an ILS at MSN with a 2.46 degree offset:

http://204.108.4.16/d-tpp/0809/00245IL21.PDF

Maybe 3 degrees is the limit?

The ILS MAP (where the GS intercepts the DH) is almost always passed before the LOC MAP (usually the runway threshold). In this case, with the DH of 1790 above the runway, you're going to reach the GS MAP a very long way out (4.3 nm from the threshold), well outside the LOC MAP (the 3.5 DME fix, which is two miles from the runway threshold).

What still confuses me, then, is how would you get in on the LDA-GS portion of this approach if visibility was at minimums?

 

[poadeleted20]

It's not 0.6 degrees, as we have an ILS at MSN with a 2.46 degree offset:

http://204.108.4.16/d-tpp/0809/00245IL21.PDF

Maybe 3 degrees is the limit?

Could be.

What still confuses me, then, is how would you get in on the LDA-GS portion of this approach if visibility was at minimums?

You don't (at least, not legally).

 

[flyingcheesehead]

You don't (at least, not legally).

So then, what's the point of those mins even existing? I would think they'd require 3.5-4 mile vis, whatever would get the approach lights in sight. Although, even that wouldn't be enough.

 

[poadeleted20]

So then, what's the point of those mins even existing?

Me , too.

I would think they'd require 3.5-4 mile vis, whatever would get the approach lights in sight. Although, even that wouldn't be enough.

I'm sure it's a TERPS thing. You see this all the time -- visibility minimums such that you couldn't make it down from MDA without an elevator if you spotted the field at the visibility minimum distance. It's an issue I hit pretty hard when giving instrument training and IPC's -- knowing when to just give up and go missed even if you spot the runway.

 

[dparter]

IIRC, the runway alignment requirement for an ILS (0.6 degrees, I think) is tighter than for a LOC (30 degrees) to be published with straight-in landing mins.

It's not 0.6 degrees, as we have an ILS at MSN with a 2.46 degree offset:

http://204.108.4.16/d-tpp/0809/00245IL21.PDF

Maybe 3 degrees is the limit?



What still confuses me, then, is how would you get in on the LDA-GS portion of this approach if visibility was at minimums?

For a long time, the straight-in ILS 21 was N/A by NOTAM. As far as I know, that NOTAM has been canceled, and the minimums did not change (but some details on the approach did change, I think).

--david

 

[flyingcheesehead]

For a long time, the straight-in ILS 21 was N/A by NOTAM. As far as I know, that NOTAM has been canceled, and the minimums did not change (but some details on the approach did change, I think).

Really? I never heard that NOTAM. I am, however, sick and tired of the "ILS 18 OM and MM decommissioned" ones that should have been published ages ago.

All of the ILS's at MSN were changed somewhat about 3 years ago. The FAF's used to be MONAH (36), WINSR (18) and ABVIZ (21), now they're OZMIX, RUKIY, and HOBIG, the markers have disappeared, DME (or radar) is required on 18 and 36, and some other minor stuff.

Comparing the old ILS 21 to the new one, there's now a procedure route from DLL instead of a feeder and you no longer need to do a procedure turn coming from DLL, the FAF was moved 0.4 nm closer to the airport, circling minimums for Cat A are 20 feet higher, and the missed hold was moved from MONAH to IMMES, so ADF is no longer required. (Aha! I think we've discovered the reason for the changes... MONAH NDB used to be the FAF for 36 and the missed approach holding fix for 18 and 21, so ADF or GPS was required for all of the ILS's. Now, it's required for none.)

 

[Everskyward]

The profile view, as drawn, seems to "imply" that the glideslope crosses CIPKU at about DA, but a 3.8 degree glideslope is 1790' high about 4.4 miles out. So I think that if you're coming down the glideslope, you hit DA a little over 2 miles before CIPKU.

The Jepp chart shows the profile more like it is in reality than the NACO chart. I attached the profile view... once I figured out how to do it. They don't make it easy to cut and paste these charts.

What I'm a little confused about is that if the DA is reached 4 miles out, how come the visibility requirements are 2 miles?
-harry

I don't understand that either. Ours is not to wonder why, I guess. You just fly it to the DA and if you don't see it you miss... which I have done on this approach. When this approach was issued I was curious why it was an LDA. I think it's because the angular difference between the final approach course and the runway is about 4 degrees. It's definitely noticeable from the air, although it is not all that much. In any case it's a better approach than the one it replaced which was a LOC/DME with only circling minimums where the MDA was something like 2,500 AGL.

 

[silver-eagle]

Given the NDB at Arlington, I had a discussion with someone about approaching for landing from RITTS. He suggested you'd cross WATON making a left turn outbound 109 degrees until you intercept R339 then a right PT inbound. If you made the airport visually planning to land on RW 34, 860' (or 960' if using Whidbey NAS), you could circle to land all the way back to 34 by following a normal upwind, cross, downwind, base and final. This would allow you to use up the altitude without any dramatic manuvers.
Sounded okay to me, but what do I know.

 

[flyingcheesehead]

Given the NDB at Arlington,

Had to look - This would be the NDB or GPS 34 into AWO: http://204.108.4.16/d-tpp/0809/00795NG34.PDF

I had a discussion with someone about approaching for landing from RITTS. He suggested you'd cross WATON making a left turn outbound

LEFT turn?

109 degrees until you intercept R339

A 307-degree left turn? I would think that unless the wind was really strong out of the east, you wouldn't need to make a 50-degree cut towards the course if you're making a teardrop type of turn. Also, if the wind was strong out of the west, you might not even make it back onto the desired course if you turned all the way around to 109.

then a right PT inbound.

This is the first part that makes sense to me.

[/quote]If you made the airport visually planning to land on RW 34, 860' (or 960' if using Whidbey NAS), you could circle to land all the way back to 34 by following a normal upwind, cross, downwind, base and final. This would allow you to use up the altitude without any dramatic manuvers.
Sounded okay to me, but what do I know.[/QUOTE]

Personally, it sounds like a LOT of dramatic maneuvers to me! I'm not sure why you'd need to circle all the way around to 34 anyway, even if you stayed at 2000 until FAF inbound, you'd only have to descend at a bit over 600 fpm (at 90 knots GS) to make it down to the runway.

If I were flying the approach, I'd take a right to about 189 (133 degree right turn) at WATON. From the start of the turn, it'd take about a minute and a half to intercept the desired course. I'd turn to 159 and see how the wind affected me. After a minute, PT to the right. Established inbound, down to 1500 and after crossing the station, a nice easy 500fpm descent to minimums (unless I had a tailwind) should result in a stabilized descent the whole way down to the runway, assuming I spot it at MDA.

 

[poadeleted20]

Given the NDB at Arlington, I had a discussion with someone about approaching for landing from RITTS. He suggested you'd cross WATON making a left turn outbound 109 degrees until you intercept R339 then a right PT inbound.

While you could do that (it would keep you on the wider side of the protected area), I would more likely make a right turn to 189-204 (depending on wind) to intercept the 159 bearing outbound -- much shorter turn.

If you made the airport visually planning to land on RW 34, 860' (or 960' if using Whidbey NAS), you could circle to land all the way back to 34 by following a normal upwind, cross, downwind, base and final. This would allow you to use up the altitude without any dramatic manuvers.

In this case, you can do that. In the original case, there are no circling minimums; circling is not authorized -- see the field far enough out to descend using a "normal rate of descent" or miss the approach. In most other cases, the straight-in MDA is lower than the circling MDA, and you'd have to climb back up to that higher MDA before leaving the final approach course and commencing your circling maneuver -- and that might (depending on ceilings) take you back up into the clag.

 

[flyingcheesehead]

While you could do that (it would keep you on the wider side of the protected area), I would more likely make a right turn to 189-204 (depending on wind) to intercept the 159 bearing outbound -- much shorter turn.

Ron,

I don't understand your comment about the protected area. The "wider side" of the protected area is on the west of the approach path, and coming from RITTS you're going to cross over to the east side. Or are you referring to the fact that the left turn would have you starting to come back towards the protected side after 77 degrees of turn (056-339) while the right turn would take 103 degrees of turn (056-159)? At 90 knots and standard rate, that means a difference of 1302 feet from the FAC (2243 feet vs. 3545 feet) at the furthest distance from the FAC, and both of those are well within the 2.5 mile minimum protected area, so it wouldn't seem to really be a consideration.

 

[poadeleted20]

I don't understand your comment about the protected area. The "wider side" of the protected area is on the west of the approach path, and coming from RITTS you're going to cross over to the east side. Or are you referring to the fact that the left turn would have you starting to come back towards the protected side after 77 degrees of turn (056-339) while the right turn would take 103 degrees of turn (056-159)? At 90 knots and standard rate, that means a difference of 1302 feet from the FAC (2243 feet vs. 3545 feet) at the furthest distance from the FAC, and both of those are well within the 2.5 mile minimum protected area, so it wouldn't seem to really be a consideration.

Correct on all counts.

 

[bobmrg]

Had to look - This would be the NDB or GPS 34 into AWO: http://204.108.4.16/d-tpp/0809/00795NG34.PDF



LEFT turn?



A 307-degree left turn? I would think that unless the wind was really strong out of the east, you wouldn't need to make a 50-degree cut towards the course if you're making a teardrop type of turn. Also, if the wind was strong out of the west, you might not even make it back onto the desired course if you turned all the way around to 109.



This is the first part that makes sense to me.

If you made the airport visually planning to land on RW 34, 860' (or 960' if using Whidbey NAS), you could circle to land all the way back to 34 by following a normal upwind, cross, downwind, base and final. This would allow you to use up the altitude without any dramatic manuvers.
Sounded okay to me, but what do I know.[/quote]

Personally, it sounds like a LOT of dramatic maneuvers to me! I'm not sure why you'd need to circle all the way around to 34 anyway, even if you stayed at 2000 until FAF inbound, you'd only have to descend at a bit over 600 fpm (at 90 knots GS) to make it down to the runway.

If I were flying the approach, I'd take a right to about 189 (133 degree right turn) at WATON. From the start of the turn, it'd take about a minute and a half to intercept the desired course. I'd turn to 159 and see how the wind affected me. After a minute, PT to the right. Established inbound, down to 1500 and after crossing the station, a nice easy 500fpm descent to minimums (unless I had a tailwind) should result in a stabilized descent the whole way down to the runway, assuming I spot it at MDA.[/quote]

Why not just extend the "missed approach" holding pattern into a racetrack procedure turn? You are protected at 2000 feet ten miles south from WATON. Why do a lot of unnecessary maneuvering?? There is no requirement to intercept the 159 bearing outbound.

Bob Gardner

 

[flyingcheesehead]

Why not just extend the "missed approach" holding pattern into a racetrack procedure turn? You are protected at 2000 feet ten miles south from WATON. Why do a lot of unnecessary maneuvering?? There is no requirement to intercept the 159 bearing outbound.

So, parallel entry and then right back in? Doable, but my thought with intercepting the 159 on the way out and doing a standard procedure turn was that it'd give me a bit of time on the outbound course to see what the wind was doing, and quite a bit more time on the inbound course to get things nice and stabilized before descending. Were I doing NDB approaches every day, I might do as you describe.

 

[poadeleted20]

So, parallel entry and then right back in? Doable, but my thought with intercepting the 159 on the way out and doing a standard procedure turn was that it'd give me a bit of time on the outbound course to see what the wind was doing, and quite a bit more time on the inbound course to get things nice and stabilized before descending.

You can do that 1-minute-outbound parallel entry if you think you can handle it, or you can extend the racetrack as far as you need (without exceeding 10 miles) to accomplish what you want. In addition, many times you will be higher than the PT altitude when you hit the IAF outbound, and will need to lose altitude to cross the fix inbound at the depicted altitude. I'd extend outbound for that, too.

How far out would I go? Depends on the altitude at which I cross the fix, the PT altitude, and the minimum altitude to cross the fix inbound.

For this approach, let's say they clear me for the approach outside RITTS, and I'm down to 2000 before I reach WATON outbound. I have to lose 500 feet once I'm established inbound, so I want at least a 1-minute inbound leg. If I'm doing the racetrack, I go out 90-120 seconds (depending on wind) so I have time to get established inbound, start my standard 500 fpm descent, and get stabilized at 1500 feet before WATON inbound. Doing a standard 45-180 PT, I may not go so far out, because the PT will drop me about a mile further out than where I started it.

OTOH, let's say send me direct WATON, maintain 3000 until established. Now I've got 1000 feet to lose going outbound, and only half that inbound. With either the racetrack or the PT, I'll get headed out, start descending, level at 2000 feet, then immediately commence my PT or inbound turn without regard for time (it will take longer to lose 1000 feet outbound than to lose 500 feet inbound), get established inbound, and then start down to 1500. My only concern on this would be staying within 10 nm, although that shouldn't be an issue with about 2 minutes required to lose that 1000 feet.

 

[bobmrg]

So, parallel entry and then right back in? Doable, but my thought with intercepting the 159 on the way out and doing a standard procedure turn was that it'd give me a bit of time on the outbound course to see what the wind was doing, and quite a bit more time on the inbound course to get things nice and stabilized before descending. Were I doing NDB approaches every day, I might do as you describe.

The words "standard procedure turn" hurt my head. According to AIM 5-4-9, "...the type and rate of turn is left to the discretion of the pilot," followed by several options (a racetrack is one of them). < ten miles outbound would not give you enough time???

Bob Gardner

 

[flyingcheesehead]

The words "standard procedure turn" hurt my head. According to AIM 5-4-9, "...the type and rate of turn is left to the discretion of the pilot," followed by several options (a racetrack is one of them). < ten miles outbound would not give you enough time???

Poor choice of words on my part. 45-180-45 is the variety I think of as "standard" but you are right, there isn't a "standard" in this case.

<10 miles had better give me enough time, because I have to remain within 10 miles!

But, within parameters, the more time I have to get established and stabilized, the better. I don't get to do NDB approaches nearly often enough - We have 3 ILS's at the home drome, and our sole NDB approach was decommissioned a few years ago.