GNSS NPA's are dangerous
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Yes, that's the whole point. The way the profile and min alts are published against distance to next waypoint (ie FAF) rather than distance to the MAPt. Alt awareness is the main reason you would be interested in the distances, so you can monitor the descent profile.
so you can monitor the descent profile.
We actually use the 300ft per nm system as it's simpler ot anticipate on the altimeter, but the principle is the same. With a distance-to-run interrupt at Foxtrot, life becomes much more difficult.
Most of the a/c I fly have 2 x GPS or a GPS that has an additional cursor-on-map function with a display of distance & bearing to the cursor position. I either set the 2nd GPS to fly direct to the Mapt or threshold, or I activate the cursor & position it over the same point - which also gives me a distance display unrelated to the other fixes in the procedure.
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Most of the a/c I fly have 2 x GPS or a GPS that has an additional cursor-on-map function with a display of distance & bearing to the cursor position. I either set the 2nd GPS to fly direct to the Mapt or threshold, or I activate the cursor & position it over the same point - which also gives me a distance display unrelated to the other fixes in the procedure.
Maybe I am ignorant of all the technical issues in fixing this hazard, but that doesn't stop me from simply stating my opinion about how I find them in the real world, two crew, EFIS, automated, RPT cockpit.
Dodgy to say the least.
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The plates for RNAV NPAs have a distance-to-runway scale at the base of the profile diagram.
Is this an afterthought? What is the point of printing the distance to run if you can't see that anywhere in front of you?
Did the engineers of the whole GPS approach format realise something after they had signed and sealed the design?
You need a distance to the runway for true situational awareness.
Any closer to fixing this? Probably not, it will take a fatal accident with a working CVR to get it fixed.
Is this an afterthought? What is the point of printing the distance to run if you can't see that anywhere in front of you?
Did the engineers of the whole GPS approach format realise something after they had signed and sealed the design?
You need a distance to the runway for true situational awareness.
Any closer to fixing this? Probably not, it will take a fatal accident with a working CVR to get it fixed.
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In a GNSS RNAV system, we have to have a CDI with a localiser needle wired up to indicate distance off track. Many such instruments I have seen in this type of GPS approach application (E.g. King KNI 520) also have a redundant glideslope needle, sitting there doing nothing. Could the G/S be connected up, using the information from the altitude encoder and GPS distance information to provide a kind of non-precision glideslope? Surely, what we need is some sort of secondary check to make sure we are not getting too low at the wrong waypoint. At the moment, if we do mistake an intermediate waypont for a later one, there is no secondary check to tell us we are getting too low, unless maybe we have a switched on, qualified co-pilot of course.
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Working cvr
Wynsoc
There has already been a fatal cfit with a working cvr, some years ago, in a westwind freighter at Alice Springs.
There are a number of lessons that we should have learned from it, but obviously we did not.
A two pilot crew was flying a triple ndb approach, which had a bend in it, but was depicted on the plate as a straight line. I have flown that approach, and it was almost unflyable (within tolerances). The captain had flown that approach on a previous occasion, and had not been happy with his tracking tolerances.
On this occasion (on a clear night) the captain was flying the aircraft, and his pre-approach brief included a minimum altitude, which was correct. But during the approach while the captain was flying, the co-pilot called an incorrest minimum altitude, which was lower than the minimum altitude the captain had nominated himself during the brief. Despite this, the captain descended and the cfit occurred.
Why??
The captain was obviously distracted by something and appears to have lost altitude awareness. I think it is a reasonable assumption that he was concentrating on trying to track within tolerance. The required tracking tolerance was +/- 5 degrees, and the approach had a built in 4 degree error.
The ATSB report criticised the captain for not maintaining the track within 5 degrees.
This approach was fairly new, and was quickly discontinued.
The two pilot crew system did not detect and rectify the altitude error.
It was a clear night, and the appraoch could have been flown safely visually. Alice Springs had a TVASI which is visible from the crash site and beyond.
There are some similarities with the lockhart river accident.
Both were two crew turbine powered aircraft, but did the two crew system work properly during the approach? Was there effective cross checking? The co-pilot at lockhart river was not qualified for the approach being flown. There is some doubt about the clarity of the approach plates, and the possibility of error when reading distances and altitudes, in both accidents.
There are still many unknowns with the lockhart river accident, and I do not pretend to have the answers. But I do believe there are similarities and lessons to be learned from these accidents, and I hope we learn them,.And act on them this time.
There has already been a fatal cfit with a working cvr, some years ago, in a westwind freighter at Alice Springs.
There are a number of lessons that we should have learned from it, but obviously we did not.
A two pilot crew was flying a triple ndb approach, which had a bend in it, but was depicted on the plate as a straight line. I have flown that approach, and it was almost unflyable (within tolerances). The captain had flown that approach on a previous occasion, and had not been happy with his tracking tolerances.
On this occasion (on a clear night) the captain was flying the aircraft, and his pre-approach brief included a minimum altitude, which was correct. But during the approach while the captain was flying, the co-pilot called an incorrest minimum altitude, which was lower than the minimum altitude the captain had nominated himself during the brief. Despite this, the captain descended and the cfit occurred.
Why??
The captain was obviously distracted by something and appears to have lost altitude awareness. I think it is a reasonable assumption that he was concentrating on trying to track within tolerance. The required tracking tolerance was +/- 5 degrees, and the approach had a built in 4 degree error.
The ATSB report criticised the captain for not maintaining the track within 5 degrees.
This approach was fairly new, and was quickly discontinued.
The two pilot crew system did not detect and rectify the altitude error.
It was a clear night, and the appraoch could have been flown safely visually. Alice Springs had a TVASI which is visible from the crash site and beyond.
There are some similarities with the lockhart river accident.
Both were two crew turbine powered aircraft, but did the two crew system work properly during the approach? Was there effective cross checking? The co-pilot at lockhart river was not qualified for the approach being flown. There is some doubt about the clarity of the approach plates, and the possibility of error when reading distances and altitudes, in both accidents.
There are still many unknowns with the lockhart river accident, and I do not pretend to have the answers. But I do believe there are similarities and lessons to be learned from these accidents, and I hope we learn them,.And act on them this time.
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It's been a while since this thread was discussed. Have there been any changes of note?
Like getting rid of the distance-to-run to multiple waypoints for e.g.
What happened to the company involved? Still flying?
Like getting rid of the distance-to-run to multiple waypoints for e.g.
What happened to the company involved? Still flying?
Wheeler, the Honeywell GPS system in my Citation Bravo did just that – i.e. it came up with a pseudo-glideslope indicator by simply projecting a 3º glideslope back from the missed approach point using the data from the Jeppesen database and the altimeter.
My current Citation CJ3 with the Proline 21 does even more – it is completely coupled vertically, and you can do the approach to the missed approach point with any GPS approach in Australia coupled to the autopilot.
This is not rocket science. The glideslope indicator is simply taking the information from the Jeppesen database and connects it directly to the autopilot.
I have had a few friends at CASA fly with me in the CJ3 and shake their heads in disbelief – I think they are trying to work out why such a simple system should be allowed!
In the United States they have the Wide Area Augmentation System (WAAS) which provides this coupled glideslope, but as I said, I have it in Australia today – in a standard CJ3 with a current Proline 21. As long as you push the buttons correctly, the autopilot will not make a mistake on the approach. Of course you monitor the approach, as you do on an ILS, to check that everything is working OK. So far, in all of the approaches I have done, it always has been.
My current Citation CJ3 with the Proline 21 does even more – it is completely coupled vertically, and you can do the approach to the missed approach point with any GPS approach in Australia coupled to the autopilot.
This is not rocket science. The glideslope indicator is simply taking the information from the Jeppesen database and connects it directly to the autopilot.
I have had a few friends at CASA fly with me in the CJ3 and shake their heads in disbelief – I think they are trying to work out why such a simple system should be allowed!
In the United States they have the Wide Area Augmentation System (WAAS) which provides this coupled glideslope, but as I said, I have it in Australia today – in a standard CJ3 with a current Proline 21. As long as you push the buttons correctly, the autopilot will not make a mistake on the approach. Of course you monitor the approach, as you do on an ILS, to check that everything is working OK. So far, in all of the approaches I have done, it always has been.
Dick
Ditto of course for any other aircraft fitted with Proline 21 ie B350 / B200.
Great gear.
Bushy
Exactly, but then Casa insist on such low equipment standards its hard to get the bar raised.
Ditto of course for any other aircraft fitted with Proline 21 ie B350 / B200.
Great gear.
Bushy
Exactly, but then Casa insist on such low equipment standards its hard to get the bar raised.
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Now my 2 cents worth. The coupled autopilot is great, but errors do occur even in the database. I am an experienced RPT jet Captain who flies these approaches every week or two. The Boeing/Jep database is sometimes in error & even if it is spot on there is a number of correct inputs some of which may accidently be overlooked by the pilots. I see it in the the sim every so often. Despite what is req'd(ie the FAF waypoint) all data should be referenced the Mapt or runway threshold enroute to the mapt section of the procedure. Some approaches like CBR 35 have waypoints reference off others in this way. Reading & matching FMC/GPS data gives very little situational awareness the way it is now. If reference is given from the airport gross errors will usually be picked up.(ie everyone knows how high they should be at 10nm etc). I believe CASA got off with murder with the Lockhart river crash. The Captain was at fault ultimately & from my knowledge wasn't overly conservative, but...CASA gave him a loaded pistol in the form of the modeled GPS approach depiction. Even with 10,000 hrs & most on RPT jets, in IMC I have a tough time tracking the approach as well as I could an ILS, VOR or even an NDB approach. The way the approach is represented needs to be changed. Everyone in my airline I speak to agrees. Most elect to do the GPS approach as a last resort because of the stated reasons. Please change this format to make it easier on everyone.
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It won't be changed, at least not until it causes a big prang and it's all there on the tape. Then they will change it and give themselves a big pat on the back for being so proactive.
[QUOTE][/it came up with a pseudo-glideslope indicator by simply projecting a 3º glideslope back from the missed approach point QUOTE]
...and if the MAPt is not at the threshold ....what then????
...and if the MAPt is not at the threshold ....what then????
Reynolds number, Dick describes the system in it's most simple form. The reality is (provided the database is coded correctly and actually has the capability to do so), the required "glideslope" is coded into the database taking into account the position of all the fixes, step limits and the MAPt.
I should of added that the Proline 21 system continues to provide tracking and height requirements through to the end of the missed approach where you then decide to hold ( all on the autopilot ), re do the approach / fly a different approach or divert.
ASA and CASA sat on their hands and did nothing when it was an identified problem.
Is that Ozexpat I see coming??
