Glideslope Intercept Altitude

#1 guarantees I'll intercept the GS from underneath. I flew a plane (luckily in VFR) where the GS needle was stuck in the center with no flag. Apparently the wire that deflects the needle upward broke somewhere. Does #2 offer the same indication?
 
dmspilot said:
I thought Plano was referring to people to intercepting at 2,000.
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I know. That they would probably be missing the mandatory altitude at DANDY. I was just saying that if you didn’t, there would still be a dive n drive choice at DANDY. 200 feet worth of dive. Just an academic discussion really. The needle would probably already be moving by then.
 
luvflyin said:
I know. That they would probably be missing the mandatory altitude at DANDY. I was just saying that if you didn’t, there would still be a dive n drive choice at DANDY. 200 feet worth of dive. Just an academic discussion really. The needle would probably already be moving by then.
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The glide slope is above 2000 feet at Dandy, FWIW.
 
MauleSkinner said:
The glide slope is above 2000 feet at Dandy, FWIW.
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Ok. But ya gotsta be at 1500 at DANDY. At. DANDY is 6 miles out. Do you figure the needle would be moving by then? I forget how wide full needle deflection is on a Glideslope.
 
luvflyin said:
Ok. But ya gotsta be at 1500 at DANDY. At. DANDY is 6 miles out. Do you figure the needle would be moving by then? I forget how wide full needle deflection is on a Glideslope.
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Pretty sure it wouldn’t, but ive never been at 2000 ft there to find out, and I’m not going to look it up. ;)
 
MauleSkinner said:
Pretty sure it wouldn’t, but ive never been at 2000 ft there to find out, and I’m not going to look it up. ;)
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I’m talking about being at 1500 like yer supposed to be. Relax, statute of limitations is probably up on that time you was at 2000:fingerwag:
 
I learned technique 1. All those misplaced concerns about false glideslopes. I was introduced to #2 when LPV came along (no false glidepath :D). Then I came to the conclusion that worrying about false glideslopes was silly. There are exceptions but procedure design is intended to have the IF or straight in IAF below glideslope/path False glideslopes appear at twice the height of the real glideslope. And early stabilization is less work than dive and drive.

OTOH, I have a friend who continues to prefer diving down. He claims it works better for him in "best forward speed" situations.
 
asicer said:
#1 guarantees I'll intercept the GS from underneath. I flew a plane (luckily in VFR) where the GS needle was stuck in the center with no flag. Apparently the wire that deflects the needle upward broke somewhere. Does #2 offer the same indication?
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Yes. #2 also guarantees you will intercept the glideslope from underneath. (Someone is sure to point out an exception but so what?)

And I have had the glideslope needle come in and stick too. Mine was in the clouds.
 
Walboy said:
Because the AIM says, "The ILS glide slope is intended to be intercepted at the published glide slope intercept altitude."

Seems crystal clear to me. So why not teach what the FAA says the intent should be?

I'm not sure how anyone can find fault with that. I'd say it's a good practice to follow the AIM.
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Good Discussion...
Here is the last two sentence for those that want to be well informed...

"Interception and tracking of the glide slope prior to the published glide slope interception altitude does not necessarily ensure that minimum, maximum, and/or mandatory altitudes published for any preceding fixes will be complied with during the descent. If the pilot chooses to track the glide slope prior to the glide slope interception altitude, they remain responsible for complying with published altitudes for any preceding stepdown fixes encountered during the subsequent  descent."

Brian
 
brcase said:
Good Discussion...
Here is the last two sentence for those that want to be well informed...

"Interception and tracking of the glide slope prior to the published glide slope interception altitude does not necessarily ensure that minimum, maximum, and/or mandatory altitudes published for any preceding fixes will be complied with during the descent. If the pilot chooses to track the glide slope prior to the glide slope interception altitude, they remain responsible for complying with published altitudes for any preceding stepdown fixes encountered during the subsequent  descent."

Brian
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As an example, following the glide slope on the LDA 25 at KEGE will put you below at least one of the step downs.
 
HF17 said:
I understand that there are two methods to intercept the glideslope. Technique 1: descend to step down fixes and intercept the glideslope at glideslope intercept altitude. Technique 2: intercept the glideslope at your last assigned altitude and verify your altitude at the outer marker. I normally use technique 1, but if I’m being vectored, or I’m in a faster airplane, or if I’m task saturated, I’ll choose technique 2.

I recently got my CFII and want to teach one technique or the other to make things as simple as possible for the student. I’m most likely going to teach technique 1, but I’m just wondering how other CFII’s teach it.

The reason why I’d avoid teaching technique 2 is because there is more to think about. You have to make sure you’re within 10nm, that you’re not on a false glideslope, and that you aren’t descending below any step down fixes.


Sent from my iPhone using Tapatalk
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Why does it have to be one or the other? Why not teach both? Factors like icing, ceiling, etc.. will make a difference. You are teaching them to be flexible and adapt to different situations, not to always do the same thing.
 
sarangan said:
Why does it have to be one or the other? Why not teach both? Factors like icing, ceiling, etc.. will make a difference. You are teaching them to be flexible and adapt to different situations, not to always do the same thing.
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Excellent response!
 
mandm said:
Usually doing the full approach takes too much time and holding patterns and missed approaches are often rushed or skipped that I would say those are weak spots on my skill set. Being vectored in and intercepting the course is more normal and the idea would to be at the correct altitude by outer marker, given permission to intercept the course is your indicator to start your descent to the outer market altitude, from what I remember.
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If you're not established on a published part of the approach, ie. you;re being vectored to the final approach coarse, and you're given permission to intercept, aren't you required to maintain the last altitude given until you're receiving course guidance?
 
Witmo said:
If you're not established on a published part of the approach, ie. you;re being vectored to the final approach coarse, and you're given permission to intercept, aren't you required to maintain the last altitude given until you're receiving course guidance?
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You are required to maintain the last assigned altitude until given an approach clearance and established on a published approach segment.
 
I have taught and demonstrated both methods, depending on the circumstances.

I have also requested and been approved for a 270 degree intercept on a localizer in a non-radar environment.

"Own navigation" is a wonderful thing...
 
IK04 said:
I have taught and demonstrated both methods, depending on the circumstances.

I have also requested and been approved for a 270 degree intercept on a localizer in a non-radar environment.

"Own navigation" is a wonderful thing...
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Knowing what you can and can’t do with regard to procedure turns can make a significant difference in the amount of puke you have to clean up. ;)
 
IK04 said:
You mean aerobatics in IMC is frowned upon?

Wussies!
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I had a guy use up pretty much every bit of protected airspace in a procedure turn trying to fly the standard 45-degree one rather than simply doing a direct entry to a HILPT.
 
IK04 said:
I have taught and demonstrated both methods, depending on the circumstances.

I have also requested and been approved for a 270 degree intercept on a localizer in a non-radar environment.

"Own navigation" is a wonderful thing...
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Can you give us some details on that. I’m having trouble picturing it.
 
luvflyin said:
Can you give us some details on that. I’m having trouble picturing it.
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Here's the scenario: An active restricted area North of the airport restricts the flow of traffic inbound to an ILS RWY 1 approach without a long outbound leg and a course reversal several miles South of the FAF. Arriving from the West, I ask for direct to the LOM on and Easterly heading and cross at the assigned altitude.

Upon station passage, I make a standard rate turn to intercept the localizer and roll out on course, at the GS intercept altitude. There is a lot happening in a short period of time, but after a few successful iterations, it is mostly just a time saver, but the local ATC boys like getting rid of me while I'm out doing multiple practice approaches.

Oh, I should mention this is in a helicopter, so it may not be quite as fun while trying to slow down and reconfigure an airplane. That would be pretty busy...
 
IK04 said:
Here's the scenario: An active restricted area North of the airport restricts the flow of traffic inbound to an ILS RWY 1 approach without a long outbound leg and a course reversal several miles South of the FAF. Arriving from the West, I ask for direct to the LOM on and Easterly heading and cross at the assigned altitude.

Upon station passage, I make a standard rate turn to intercept the localizer and roll out on course, at the GS intercept altitude. There is a lot happening in a short period of time, but after a few successful iterations, it is mostly just a time saver, but the local ATC boys like getting rid of me while I'm out doing multiple practice approaches.

Oh, I should mention this is in a helicopter, so it may not be quite as fun while trying to slow down and reconfigure an airplane. That would be pretty busy...
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Ok. Sounds like you did a PT. You did it on the side indicated by the Barb and remained within 10 NM. Arriving at a 90 degree angle from the Non Maneuvering side and hanging a 270 on the Maneuvering side is perfectly legal. Some Approaches may have you a little high doing that and intercepting the Glideslope from above though.
 
IK04 said:
Here's the scenario: An active restricted area North of the airport restricts the flow of traffic inbound to an ILS RWY 1 approach without a long outbound leg and a course reversal several miles South of the FAF. Arriving from the West, I ask for direct to the LOM on and Easterly heading and cross at the assigned altitude.

Upon station passage, I make a standard rate turn to intercept the localizer and roll out on course, at the GS intercept altitude. There is a lot happening in a short period of time, but after a few successful iterations, it is mostly just a time saver, but the local ATC boys like getting rid of me while I'm out doing multiple practice approaches.

Oh, I should mention this is in a helicopter, so it may not be quite as fun while trying to slow down and reconfigure an airplane. That would be pretty busy...
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Works well in jets, too.
 
luvflyin said:
Isolating the first sentence of 5-4-5 b. 4. Note 2 and ignoring everything else said elsewhere in the AIM and other publications about the advantages of, and recommendations for doing stabilized, constant angle of descent Approaches does not seem wise to me.
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Note 2 was added because pilots were getting deviations for intercepting the GS early and not honoring mandatory altitudes on step down fixes. Prior to note 2 being published in the AIM there was an AC on this issue which better explained the problem, but it has to do with separation requirements outside the FAF, particularly in busy areas where mandatory altitudes on step downs are necessary. CDFA and stabilized approaches are a great thing, but a poor excuse for busting an altitude outside the FAF. If you bust DANDY on the TEB ILS RWY 06, you will almost certainly get a number to call.
 
Captain Bubba said:
Note 2 was added because pilots were getting deviations for intercepting the GS early and not honoring mandatory altitudes on step down fixes. Prior to note 2 being published in the AIM there was an AC on this issue which better explained the problem, but it has to do with separation requirements outside the FAF, particularly in busy areas where mandatory altitudes on step downs are necessary. CDFA and stabilized approaches are a great thing, but a poor excuse for busting an altitude outside the FAF. If you bust DANDY on the TEB ILS RWY 06, you will almost certainly get a number to call.
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Yeah. I sent a change request into the FAA a few years ago about how that Note was sometimes being misinterpreted by pilots and how it might be worded a little better. They acknowledged receipt. Never heard anything else and it hasn’t changed. Do you have that AC number?
 
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luvflyin said:
Yeah. I sent a change request into the FAA a few years ago about how that Note was sometimes being misinterpreted by pilots and how it might be worded a little better. They acknowledged receipt. Never heard anything else and it hasn’t changed. Do you have that AC number?
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I’m not even 100% sure it was an AC, but there was published guidance on this issue before they added the note to the AIM. This goes back a few years so I don’t remember the reference. This problem can be very insidious in some situations because on one day you might come down on the GS without problems, but on another the temps are higher, you intercept sooner, start down, and ATC is asking why. In some situations it’s better to let VNAV do your step downs and wait to arm the ILS until right before the FAF. Then you might find yourself above the GS and have to dive for it. It’s certainly not the ideal situation in regards to stabilizing your approach, but it beats having a conversation with FSDO about your future in aviation.
 
Captain Bubba said:
I’m not even 100% sure it was an AC, but there was published guidance on this issue before they added the note to the AIM. This goes back a few years so I don’t remember the reference. This problem can be very insidious in some situations because on one day you might come down on the GS without problems, but on another the temps are higher, you intercept sooner, start down, and ATC is asking why. In some situations it’s better to let VNAV do your step downs and wait to arm the ILS until right before the FAF. Then you might find yourself above the GS and have to dive for it. It’s certainly not the ideal situation in regards to stabilizing your approach, but it beats having a conversation with FSDO about your future in aviation.
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Correct me if I'm off here, but it seems these temperature-related problems can be (and prior to the chart updates, could have been) avoided with systems supporting VNAV (i.e. modern digital autopilots/flight directors):
  • such that all the segments outside the leg leading to the FAF are flown with magenta needles and VNAV advisory glide paths... hitting the stepdown altitudes precisely at each intermediate waypoint...
  • and then auto-switching to green needles once on the segment leading to the FAF and only then capturing the glideslope.
Also seems to me to be a "best practice" to avoid green needles until the segment leading to the FAF.
Thoughts?
Wayne
 
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wayneda40 said:
Correct me if I'm off here, but it seems these temperature-related problems can be (and prior to the chart updates, could have been) avoided with systems supporting VNAV (i.e. modern digital autopilots/flight directors):
  • such that all the segments outside the leg leading to the FAF are flown with magenta needles and VNAV advisory glide paths... hitting the stepdown altitudes precisely at the each intermediate waypoint...
  • and then auto-switching to green needles once on the segment leading to the FAF and only then capturing the glideslope.
Also seems to me to be a "best practice" to avoid green needles until the segment leading to the FAF.
Thoughts?
Wayne
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Pretty much.
 
luvflyin said:
I’m not sure. Wouldn’t you have to plug that in one segment at a time?
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@luvflyin , no, the FPL includes all the stepdown waypoints and their corresponding altitudes. The pilot upon being cleared to the first waypoint (and cleared for the approach) simply activates VNAV (and dials ALTS to the FAF altitude)... and the FD/Autopilot then does ALL the stepdowns (there could be a dozen or more stepdowns) without further pilot intervention (but of course, carefully monitoring everything :)). I can confirm this is the case on GFC500/600/700 autopilots (certification of VNAV can vary by airframe, but I've confirmed the above on my DA40 and a Sling TSi).

The same process also works for VNAV operations on an Arrival procedure.
 
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wayneda40 said:
Correct me if I'm off here, but it seems these temperature-related problems can be (and prior to the chart updates, could have been) avoided with systems supporting VNAV (i.e. modern digital autopilots/flight directors):
  • such that all the segments outside the leg leading to the FAF are flown with magenta needles and VNAV advisory glide paths... hitting the stepdown altitudes precisely at each intermediate waypoint...
  • and then auto-switching to green needles once on the segment leading to the FAF and only then capturing the glideslope.
Also seems to me to be a "best practice" to avoid green needles until the segment leading to the FAF.
Thoughts?
Wayne
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wayneda40 said:
@luvflyin , no, the FPL includes all the stepdown waypoints and their corresponding altitudes. The pilot upon being cleared to the first waypoint (and cleared for the approach) simply activates VNAV (and set ALTS to be the FAF altitude)... and the FD/Autopilot then does ALL the stepdowns (there could be a dozen or more stepdowns) without further pilot intervention. I can confirm this is the case on GFC500/600/700 autopilots.

The same process also works for VNAV operations on an Arrival procedure.
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I had deleted that post because I wanted to think some more and hadn’t had a reply yet, but you obviously were as I was doing it. So. How are those Magenta needles generated? It seems that they would be generating a ‘fixed’ Glidepath via GPS, most certainly with WAAS. Just like an ILS generates a ‘fixed’ Glideslope. Therefore subject to the same problems with temperature.
 
luvflyin said:
I had deleted that post because I wanted to think some more and hadn’t had a reply yet, but you obviously were as I was doing it. So. How are those Magenta needles generated? It seems that they would be generating a ‘fixed’ Glidepath via GPS, most certainly with WAAS. Just like an ILS generates a ‘fixed’ Glideslope. Therefore subject to the same problems with temperature.
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The crossing altitudes are indicated altitude, and most of the more advanced systems use baro VNAV until the fix prior to the FAF, even if WAAS-equipped. So you’d cross at the proper altitudes.
 
luvflyin said:
I had deleted that post because I wanted to think some more and hadn’t had a reply yet, but you obviously were as I was doing it. So. How are those Magenta needles generated? It seems that they would be generating a ‘fixed’ Glidepath via GPS, most certainly with WAAS. Just like an ILS generates a ‘fixed’ Glideslope. Therefore subject to the same problems with temperature.
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The system generates the "vertical" magenta needles (it's actually a chevron VDI on the PFD) by a real-time "drive and drive" calculation of a segment "glidepath" assuring that you reach the next waypoint at exactly the assigned altitude. There's a bit of a description in this video on Modern Avionics -- Vertical Navigation. I would think that this is not subject to temperature and only subject to the appropriate local altimeter setting (as @MauleSkinner notes).
 
MauleSkinner said:
The crossing altitudes are indicated altitude, and most of the more advanced systems use baro VNAV until the fix prior to the FAF, even if WAAS-equipped. So you’d cross at the proper altitudes.
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Ok. If the needles put you over the Fixes at the correct indicated altitude then cool, do it.
 
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