Flying GPS when you are supposed to look for the LLZ
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Flying GPS when you are supposed to look for the LLZ
Delta did this to me two days in a row now. Care to comment?
As you see on my sketch, pretty simple stuff. On the intercept heading about 2 nm from the LLZ, he turns northbound. Away from the airport. According to him, because he is flying via his mapping (GPS?) I ask him why he's turning away, and he answers that he was infact turning IN because he was through the final! (Again he must be reffering to his GPS because he was never even close). Pushed hard he addmits that he never "saw" the LLZ. Is this just a case of faulty mapping and poor airmanship, or is it happening all the time? (new to me)
dangerous stuff to be turning on your own under radorvectors in busy final environment.
Rgrds!
As you see on my sketch, pretty simple stuff. On the intercept heading about 2 nm from the LLZ, he turns northbound. Away from the airport. According to him, because he is flying via his mapping (GPS?) I ask him why he's turning away, and he answers that he was infact turning IN because he was through the final! (Again he must be reffering to his GPS because he was never even close). Pushed hard he addmits that he never "saw" the LLZ. Is this just a case of faulty mapping and poor airmanship, or is it happening all the time? (new to me)
dangerous stuff to be turning on your own under radorvectors in busy final environment.
Rgrds!
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Not experienced it myself but is it really fair to say 'dangerous stuff to be turning on your own under radorvectors in busy final environment' when the aircraft is on an intercept heading? You would expect the pilot to finish the turn onto the LLZ on his or her own - the problem that you have is that the aircraft is turning in the wrong direction!
I would be inclined to look upon this as a navigation problem and get it looked into. Have you reported it under your occurrence reporting scheme? Maybe your company could contact Delta direct to see if there is a problem that they can fix without difficulty?
I would be inclined to look upon this as a navigation problem and get it looked into. Have you reported it under your occurrence reporting scheme? Maybe your company could contact Delta direct to see if there is a problem that they can fix without difficulty?
Sounds to me like his database has the wrong mapping convention installed. We used to get it a lot in the early days when we were still OSGB 36 and the GPS was WGS 84; made about 500m difference ie the aircraft positioned itself 500m north of the correct final approach track.
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Was it a 767 and were they high on the profile?
If it was a 767 it may have been that they were looking at the Map, and if it was not a GPS jet, that would explain why the Map was not accurate (although 2 nm seems like a lot). Regardless, if APP was armed the jet would have intercepted the LOC.
Many prefer to stay in HDG SEL (or LNAV) until late in the intercept to ensure that the glideslope is not captured first. If they thought they had blown through the Localizer, raw data would have answered that question.
Many prefer to stay in HDG SEL (or LNAV) until late in the intercept to ensure that the glideslope is not captured first. If they thought they had blown through the Localizer, raw data would have answered that question.
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I would say he should not turn on to the LLZ track using his GPS unless he is cleared for an Approved GPS Approach.
From what you say, it seems it was not a GPS Approach but an ordinary ILS Approach.
Clearly, if he is on a heading for LOC intercept, the only turn should be on to the Localiser beam itself i.e. at ILS LOC capture. To anticipate this turn for any other reason than an active beam bar would be, to use your words, just "poor airmanship".
JD
From what you say, it seems it was not a GPS Approach but an ordinary ILS Approach.
Clearly, if he is on a heading for LOC intercept, the only turn should be on to the Localiser beam itself i.e. at ILS LOC capture. To anticipate this turn for any other reason than an active beam bar would be, to use your words, just "poor airmanship".
JD
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Hmm my sketch isn't showing but you get the picture. It was a 767 and he might have been a bit high on the profile. I thought it a bit funny that he was descending on the glideslope but heading 40 degrees away from the airport. Good thing we don't have anything higher than the little mermaid here in Copenhagen. 
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Short Approach?
A possible explanation (not excuse)...
I will guess that they were not a GPS-equipped jet, and that their Nav Display (called the MAP) was off a bit. The non-GPS jets update FMS position (MAP position) based on IRS inputs and DME inputs. That can be off a mile or so after 9 hours of flying. The jets with GPS do not have that problem, and typically keep the FMS position very accurate...often within .2nm or less.
Localizer signal quality can be erratic at some places (Brussels is a known location), and it is preferred to stay in HDG SEL or LNAV (and look at the MAP instead of raw data) so that the autopilot is not chasing what looks like a windshield wiper. Still, one look at the raw data would clue the crew that they have not overshot the localizer.
My guess is that you got their attention by questioning them, and that they reported the situation internally and anonomously so as to spread the word.
A possible explanation (not excuse)...
I will guess that they were not a GPS-equipped jet, and that their Nav Display (called the MAP) was off a bit. The non-GPS jets update FMS position (MAP position) based on IRS inputs and DME inputs. That can be off a mile or so after 9 hours of flying. The jets with GPS do not have that problem, and typically keep the FMS position very accurate...often within .2nm or less.
Localizer signal quality can be erratic at some places (Brussels is a known location), and it is preferred to stay in HDG SEL or LNAV (and look at the MAP instead of raw data) so that the autopilot is not chasing what looks like a windshield wiper. Still, one look at the raw data would clue the crew that they have not overshot the localizer.
My guess is that you got their attention by questioning them, and that they reported the situation internally and anonomously so as to spread the word.
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If ATC assign you a heading to intercept the localiser, then the pilot has to maintain that constant heading until 'LOC' capture - either manually or automatically. To turn away from the assigned heading is due to finger-trouble on the part of the PF, or problems with the a/c's systems. Continuing with LNAV or GPS when given a specific heading, would be contrary to SOP's. If Delta were trialling GPS approach then it should have at least been subject to approval as a trial by the relevant ATC unit.
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Short Approach?
From what you say it seems that the aircraft was not complying with an ATC instruction......and therefore carrying out an illegal manoeuvre. In an extreme case this practice could compromise not only the safety of the subject aircraft and its passengers, but also the safety of other airspace users.
Hopefully there will be sufficient evidence to absolve ATC of any liability should this practice continue.
TOP TIP: keep a record of these occurrences to set up a database......not necessarily a full blown official report.....the aim is to help everyone rather than cause upset.
PRECEDENT: aircraft given a surveillance radar approach [SRA]...traditionally the controller gives headings to maintain track....adjusting as necessary for wind change etc. The aircraft flies the assigned heading as instructed. Peculiar things started to occur when pilots just set the track required and the aircraft flew its own constantly/continuously corrected headings instead...and without the knowledge of the controller. In such cases the controller was then completely unable to give an SRA because his/her reference heading was no longer valid.
Hopefully there will be sufficient evidence to absolve ATC of any liability should this practice continue.
TOP TIP: keep a record of these occurrences to set up a database......not necessarily a full blown official report.....the aim is to help everyone rather than cause upset.
PRECEDENT: aircraft given a surveillance radar approach [SRA]...traditionally the controller gives headings to maintain track....adjusting as necessary for wind change etc. The aircraft flies the assigned heading as instructed. Peculiar things started to occur when pilots just set the track required and the aircraft flew its own constantly/continuously corrected headings instead...and without the knowledge of the controller. In such cases the controller was then completely unable to give an SRA because his/her reference heading was no longer valid.
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skiesfull..."Continuing with LNAV or GPS when given a specific heading, would be contrary to SOP's"
No pilot would do that. However, if in HDG SEL, and on the directed heading, if the MAP shows you going through the localizer (but the MAP is incorrect because of FMS position error), it is tempting to turn inbound, or in this case to turn to a heading to intercept from the perceived blow-through. It is best to first verify with raw data that you have in fact gone through the localizer before trusting the MAP display in this scenario.
055166k..."From what you say it seems that the aircraft was not complying with an ATC instruction......and therefore carrying out an illegal manoeuvre"
Are you suggesting that the crew was intentionally deviating from an ATC clearance? I have never flown with a pilot who would do that.
No pilot would do that. However, if in HDG SEL, and on the directed heading, if the MAP shows you going through the localizer (but the MAP is incorrect because of FMS position error), it is tempting to turn inbound, or in this case to turn to a heading to intercept from the perceived blow-through. It is best to first verify with raw data that you have in fact gone through the localizer before trusting the MAP display in this scenario.
055166k..."From what you say it seems that the aircraft was not complying with an ATC instruction......and therefore carrying out an illegal manoeuvre"
Are you suggesting that the crew was intentionally deviating from an ATC clearance? I have never flown with a pilot who would do that.
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The aim of this site is discussion, and not to apportion blame.
My point is ....assuming the pilot is in control of the aircraft and its systems....that any unauthorised manoeuvre carried out in airspace which requires compliance with ATC instructions may be considered illegal in some nation states' airspace.
If the pilot is instructed to fly an assigned heading to intercept the localiser then it is the localiser and not another form of tracking reference that the pilot should intercept. I believe the original poster meant to highlight that point.
This should not preclude any pilot from asking for approval for any particular manoeuvre at any time.....but please tell or ask first...keep the controller in the loop.....we're not psychic!
What goes through a controller's head?
FMS failure? Unlawful interference? ILS failure? Radar/tracking malfunction? RT failure? Unexpected wind anomoly? Wake vortex upset? Pilot incapacitation?......we watch everything....tell us what you're doing if it is unusual....we're here to help, not hinder.
My point is ....assuming the pilot is in control of the aircraft and its systems....that any unauthorised manoeuvre carried out in airspace which requires compliance with ATC instructions may be considered illegal in some nation states' airspace.
If the pilot is instructed to fly an assigned heading to intercept the localiser then it is the localiser and not another form of tracking reference that the pilot should intercept. I believe the original poster meant to highlight that point.
This should not preclude any pilot from asking for approval for any particular manoeuvre at any time.....but please tell or ask first...keep the controller in the loop.....we're not psychic!
What goes through a controller's head?
FMS failure? Unlawful interference? ILS failure? Radar/tracking malfunction? RT failure? Unexpected wind anomoly? Wake vortex upset? Pilot incapacitation?......we watch everything....tell us what you're doing if it is unusual....we're here to help, not hinder.
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"The aim of this site is discussion, and not to apportion blame."
I agree 100%.
If you are looking at your workstation (radar scope or Nav Display map), and it shows you need to make an input to correct an action, it is tempting to do so without referring to back-up data.
I look at the FMS as my primary source of navigation nearly 100% of the time, backing up my localizer intercepts with raw data. Then one time the FMS shows me going through the localizer before the autopilot intercepts the localzer, and with the raw data localizer needle still offscale. Is the needle stuck? Do I have a gage problem? Is there an autopilot/autoflight irregularity?
Maybe, but the FMS display of the localizer course is not a true localizer display, but rather a course generated on a map based on FMS position (which is subject to error on rare occasions). Everything I normally look at (with the exception of the raw data localizer info) says I am going through the loc.
If the jet's FMS map showed a pilot was blowing through the localizer, he could:
1) turn inbound and then verify with raw data if the Map was in error (could be due to map shift or IRS drift);
2) hold the heading and risk going way beyond the localizer course (if there was no map error) while checking raw data;
3) always keep an eye on raw data to prevent conflicting data.
This is a reminder for me to keep up with raw data, and to share this event with others when the subject comes up.
I agree 100%.
If you are looking at your workstation (radar scope or Nav Display map), and it shows you need to make an input to correct an action, it is tempting to do so without referring to back-up data.
I look at the FMS as my primary source of navigation nearly 100% of the time, backing up my localizer intercepts with raw data. Then one time the FMS shows me going through the localizer before the autopilot intercepts the localzer, and with the raw data localizer needle still offscale. Is the needle stuck? Do I have a gage problem? Is there an autopilot/autoflight irregularity?
Maybe, but the FMS display of the localizer course is not a true localizer display, but rather a course generated on a map based on FMS position (which is subject to error on rare occasions). Everything I normally look at (with the exception of the raw data localizer info) says I am going through the loc.
If the jet's FMS map showed a pilot was blowing through the localizer, he could:
1) turn inbound and then verify with raw data if the Map was in error (could be due to map shift or IRS drift);
2) hold the heading and risk going way beyond the localizer course (if there was no map error) while checking raw data;
3) always keep an eye on raw data to prevent conflicting data.
This is a reminder for me to keep up with raw data, and to share this event with others when the subject comes up.
