Erebus 25 years on
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Navigation by Weather Radar
Greybeard #394:
I anticipate that Desert Dingo will, at some stage, post an extract where Mister Justice Mahon deals with the failure to locate Erebus via the weather radar.
To those, like me, who want to shoot Mahon down, it has to be accepted that he is a quite a difficult target.
I anticipate that Desert Dingo will, at some stage, post an extract where Mister Justice Mahon deals with the failure to locate Erebus via the weather radar.
To those, like me, who want to shoot Mahon down, it has to be accepted that he is a quite a difficult target.
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Thanks for the update on Mahon. I had forgotten that gem. The ice cannot be hundreds of feet thick near the pointy part of Erebus; else how could it be steaming? Even if the weather radar signal penetrated the ice, rather than bouncing off it, the signal would bounce off the rocks below the ice. In fact, that's how they measure ice thickness. Also, wasn't there some visible rock on Beaufort Island?
Ice without a wet surface is indeed a poor radar reflector, but it is not radar absorbent, so it will pass the signal in both directions.
Granted, the radio altimeters are C band, 4350 MHz, while the RDR-1F is X-band, 9300 MHz, but the radio altimeters saw the 300 foot ice cliff at the water's edge, and tripped the GPWS.
BTW, weren't they flying at 700', and hit at the 1500' level?
There was no good reason for not employing the weather radar for navigation at least some time in the last half hour.
GB
Ice without a wet surface is indeed a poor radar reflector, but it is not radar absorbent, so it will pass the signal in both directions.
Granted, the radio altimeters are C band, 4350 MHz, while the RDR-1F is X-band, 9300 MHz, but the radio altimeters saw the 300 foot ice cliff at the water's edge, and tripped the GPWS.
BTW, weren't they flying at 700', and hit at the 1500' level?
There was no good reason for not employing the weather radar for navigation at least some time in the last half hour.
GB
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Greybeard #398:
They were 43 miles out at 18000 heading for Erebus (which goes to 13000), and then orbited down to 2000 and locked the aircraft back onto the nav track, again heading for Erebus. They then dropped to 1500, which is near enough to the impact altitude.
Chippendale's 3D plot of the track against the terrain is chilling. Worse still are the passengers' photos. It seems very clear that the crew were completely taken in by the sector whiteout.
They were 43 miles out at 18000 heading for Erebus (which goes to 13000), and then orbited down to 2000 and locked the aircraft back onto the nav track, again heading for Erebus. They then dropped to 1500, which is near enough to the impact altitude.
Chippendale's 3D plot of the track against the terrain is chilling. Worse still are the passengers' photos. It seems very clear that the crew were completely taken in by the sector whiteout.
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Ampan,
"This aspect has been hotly debated. Many pilots flying the DC10's to Antarctica used the weather radar in mapping mode, which clearly confirmed the outline of Ross Island and its high ground that they could see through the cockpit windows in the clear Antarctic conditions."
How difficult would it have been to monitor their movements on their own radar??
"It seems very clear that the crew were completely taken in by the sector whiteout."
That is glaringly obvious, but why did they put themselves in that position?? They had the AINS, just transfer a position onto the chart prior to descent, they had their own radar, it would appear that mapping mode showed up Ross Island, they could have confirmed with McMurdo Radar, or why did they not accept the weather advice from McMurdo, not good for sightseeing. go to Taylor Valley.
"This aspect has been hotly debated. Many pilots flying the DC10's to Antarctica used the weather radar in mapping mode, which clearly confirmed the outline of Ross Island and its high ground that they could see through the cockpit windows in the clear Antarctic conditions."
How difficult would it have been to monitor their movements on their own radar??
"It seems very clear that the crew were completely taken in by the sector whiteout."
That is glaringly obvious, but why did they put themselves in that position?? They had the AINS, just transfer a position onto the chart prior to descent, they had their own radar, it would appear that mapping mode showed up Ross Island, they could have confirmed with McMurdo Radar, or why did they not accept the weather advice from McMurdo, not good for sightseeing. go to Taylor Valley.
Last edited by prospector; 24th Feb 2008 at 03:00.
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Pilot Error
I agree, Prospector. This crew could have done better. At least one AirNZ crew that we know of, when faced with similar conditions, decided to divert. You would obviously have done the same, whereas Desert Dingo would have ended up "spread all over the mountain". The problem I have is that once they were off the ground, there is no one discreet incident that anyone can point to and say "That was an error".
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Originally Posted by ampan
I agree, Prospector. This crew could have done better. At least one AirNZ crew that we know of, when faced with similar conditions, decided to divert. You would obviously have done the same, whereas Desert Dingo would have ended up "spread all over the mountain". The problem I have is that once they were off the ground, there is no one discreet incident that anyone can point to and say "That was an error".
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Already covered, Hempy.
But it was covered by reference to the evidence of Captain Wilson, who said that he told the crews that they could go below FL160 VMC with ATC approval - thereby completely buggering up AirNZ's minimum altitude argument. Yet this same gentleman, having had no difficulties potting the boss over the altitude issue, was found to be lying when he said that he told the crew the nav track went over Erebus.
I note that Capt. Wilson served in WW2, so he is probably gone by now. But he and his family have my sympathies.
But it was covered by reference to the evidence of Captain Wilson, who said that he told the crews that they could go below FL160 VMC with ATC approval - thereby completely buggering up AirNZ's minimum altitude argument. Yet this same gentleman, having had no difficulties potting the boss over the altitude issue, was found to be lying when he said that he told the crew the nav track went over Erebus.
I note that Capt. Wilson served in WW2, so he is probably gone by now. But he and his family have my sympathies.
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Ampan,
Bob Thomson, who has been quoted by me a few times in this thread was probably closest to the cause he states
"The captain didn't give attention to problems he might have around there. These people were taking a Sunday drive. When I heard the transcript of the CVR I fell out of my chair. Most of the times Mulgrew had been down there he had gone by sea, and all his travels from Scott Base had been to the south. Hardly anybody ever went into Lewis Bay.
Had they orbited Ross Island they would have seen the cloud. If a pilot is unsure he always goes up, never down. The Co-Pilot on FLT901 never opened his flight bag to look up the co-ordinates. I always had a chart in the cockpit and checked the lat and long readout, but the crew of the fatal flight never referred to it."
Bob Thomson was not qualified aircrew, but he had done more trips to the ice than most, and very often in the cockpit, and he certainly was New Zealands most experienced Antarctic person.
Bob Thomson, who has been quoted by me a few times in this thread was probably closest to the cause he states
"The captain didn't give attention to problems he might have around there. These people were taking a Sunday drive. When I heard the transcript of the CVR I fell out of my chair. Most of the times Mulgrew had been down there he had gone by sea, and all his travels from Scott Base had been to the south. Hardly anybody ever went into Lewis Bay.
Had they orbited Ross Island they would have seen the cloud. If a pilot is unsure he always goes up, never down. The Co-Pilot on FLT901 never opened his flight bag to look up the co-ordinates. I always had a chart in the cockpit and checked the lat and long readout, but the crew of the fatal flight never referred to it."
Bob Thomson was not qualified aircrew, but he had done more trips to the ice than most, and very often in the cockpit, and he certainly was New Zealands most experienced Antarctic person.
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I was acquainted with a DC-10 Flight Engineer for McDouglas who was a friend of the F/E on 901. He heard the tape early on, and told me his friend was the only one in the cockpit who had been there before. He heard his friend say, "I don't like it," and he implied, or maybe said, "Let's get out of here."
He went on to say that when the GPWS warned, the captain calmly said, "Climb power, please."
The pilots were so sure of their position, they obviously believed the GPWS to be a nuisance warning, which did happen now and again, but almost always above 2,500 agl.
I promised myself before I started posting on this thread that I would not be judgemental. I may go back and delete some of my statements. This was such a preventable accident in such an improbable place..
GB
He went on to say that when the GPWS warned, the captain calmly said, "Climb power, please."
The pilots were so sure of their position, they obviously believed the GPWS to be a nuisance warning, which did happen now and again, but almost always above 2,500 agl.
I promised myself before I started posting on this thread that I would not be judgemental. I may go back and delete some of my statements. This was such a preventable accident in such an improbable place..
GB
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AINS-70 Navigation
This background info starts with INS, Inertial Navigation Systems, that were prevalent for long haul over water ops in the 1970s and 1980s, and still used today. It will no doubt be old hat to many of you, but always new to some.
The gyro stabilized platform contains a very sensitive accelerometer in each of the 3 axes. They are sensitive enough to sense the earth's rotational rate, and can thereby independently determine the latitude of the platform's present position on earth to within several miles. It cannot independently determine longitude.
Once the platform is given actual latitude and longitude,it aligns itself over a period of maybe 15 minutes, during which time it must not be moved or jarred.
Once aligned and moving, simple physics formulas are used to integrate accelerations into track, ground speed and present position. The platform pitch, roll and yaw outputs are great for feeding the pilots' insruments and the autopilot, as precession, turning errors, etc., are eliminated.
INS was a wonderful advancement over Doppler and Loran A. The Delco Carousel IV and the Litton LTN 51 were the first on the scene, with Collins Avionics a minor player on Continental and Western Airlines' DC-10 fleets. INS was legal for navigation only for flight beyond line of sight from VOR-DME, as its accuracy degraded at a rate of up to 2 nm per hour from time of alignment. The US Dept of Defense even had rules limiting the accuracy of INS, just like in the early days of GPS.
The Inertial Sensor Unit, or platform plus integration, was the heart of the INU, Inertial Navigator Unit. The INU also contained a navigation computer to calculate where you're going and when you'll arrive.
After Present Position for alignment, the pilot would key in the lat/long of each succeeding waypoint into the CDU, for a total of up to 10 or more. If more waypoints were need for the flight, they would have to be keyed in enroute.
What could go badly wrong with INS to cause error in navigation? Other than the usual mechanical failures, INS depends on the eyes and scrutiny of the pilot to enter the correct lat/long. Airline ops therefore have required a separate set of eyes and fingers be used to enter the present position numbers into each CDU/INU. One pilot might enter all enroute waypoints and destination, and then crossload to the other INS units aboard, but starting position was too important to cross load.
Again, the ISU would sense a wrong latitude for present position, but not wrong longitude. There have been many cases over the years of pilots confusing East longitude for West, and it even continues to happen with GPS. If the Long is Wrong, you may swim.
I'm of the belief that the F/E or copilot on KAL-007 entered the wrong longitude for p/p in Anchorage. Instead of 149 West, he may have entered 139 west or 140 west. Either one would put them west of correct track, and over Sakhalin.
Just a month before 007, a Continental DC10-10 did an air turnback to KLAX. The crew had been alerted by ATC for being off course as they were leaving the coast, headed for Honolulu. They had entered the correct lat for LAX, but the longitude of Denver, another of their hubs. If ATC had not called, they just might have gone for a swim some 800 miles west of HNL, having passed to the north on the great circle.
The INS has outputs to the pilots' instruments and to the autopilot, similar to VOR-DME navigation. It was up to the pilots to average or guess the correct present position when the two or three units aboard differed. The LTN-72 had an upgrade in the 1980s called triple mix in which it calculated a present position based on averaging the three, and even ignoring one if it differed much from the other two.
More coming.
GB
The gyro stabilized platform contains a very sensitive accelerometer in each of the 3 axes. They are sensitive enough to sense the earth's rotational rate, and can thereby independently determine the latitude of the platform's present position on earth to within several miles. It cannot independently determine longitude.
Once the platform is given actual latitude and longitude,it aligns itself over a period of maybe 15 minutes, during which time it must not be moved or jarred.
Once aligned and moving, simple physics formulas are used to integrate accelerations into track, ground speed and present position. The platform pitch, roll and yaw outputs are great for feeding the pilots' insruments and the autopilot, as precession, turning errors, etc., are eliminated.
INS was a wonderful advancement over Doppler and Loran A. The Delco Carousel IV and the Litton LTN 51 were the first on the scene, with Collins Avionics a minor player on Continental and Western Airlines' DC-10 fleets. INS was legal for navigation only for flight beyond line of sight from VOR-DME, as its accuracy degraded at a rate of up to 2 nm per hour from time of alignment. The US Dept of Defense even had rules limiting the accuracy of INS, just like in the early days of GPS.
The Inertial Sensor Unit, or platform plus integration, was the heart of the INU, Inertial Navigator Unit. The INU also contained a navigation computer to calculate where you're going and when you'll arrive.
After Present Position for alignment, the pilot would key in the lat/long of each succeeding waypoint into the CDU, for a total of up to 10 or more. If more waypoints were need for the flight, they would have to be keyed in enroute.
What could go badly wrong with INS to cause error in navigation? Other than the usual mechanical failures, INS depends on the eyes and scrutiny of the pilot to enter the correct lat/long. Airline ops therefore have required a separate set of eyes and fingers be used to enter the present position numbers into each CDU/INU. One pilot might enter all enroute waypoints and destination, and then crossload to the other INS units aboard, but starting position was too important to cross load.
Again, the ISU would sense a wrong latitude for present position, but not wrong longitude. There have been many cases over the years of pilots confusing East longitude for West, and it even continues to happen with GPS. If the Long is Wrong, you may swim.
I'm of the belief that the F/E or copilot on KAL-007 entered the wrong longitude for p/p in Anchorage. Instead of 149 West, he may have entered 139 west or 140 west. Either one would put them west of correct track, and over Sakhalin.
Just a month before 007, a Continental DC10-10 did an air turnback to KLAX. The crew had been alerted by ATC for being off course as they were leaving the coast, headed for Honolulu. They had entered the correct lat for LAX, but the longitude of Denver, another of their hubs. If ATC had not called, they just might have gone for a swim some 800 miles west of HNL, having passed to the north on the great circle.
The INS has outputs to the pilots' instruments and to the autopilot, similar to VOR-DME navigation. It was up to the pilots to average or guess the correct present position when the two or three units aboard differed. The LTN-72 had an upgrade in the 1980s called triple mix in which it calculated a present position based on averaging the three, and even ignoring one if it differed much from the other two.
More coming.
GB
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AINS
Interesting stuff, Greybeard. I think that the potential for data-entry errors was the one of the reasons why AirNZ's Navigation Section converted the waypoints for their routes to a computer-tape system in the late 1970s. It would take the pilots out of the equation.
It was this exercise that resulted in the shift of the nav track to McMurdo Sound. (Although if the route was on computer-tape, why the need for manual entry?)
It appears that most of AINS incidents occurred after the Erebus flight, the only exception being the Ozarks accident. It would be interesting to know how much publicity that accident received.
It was this exercise that resulted in the shift of the nav track to McMurdo Sound. (Although if the route was on computer-tape, why the need for manual entry?)
It appears that most of AINS incidents occurred after the Erebus flight, the only exception being the Ozarks accident. It would be interesting to know how much publicity that accident received.
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There was no provision for ANZ to load any routes electronically into the AINS-70. That was done for all operators by Swissair. For Antarctica flights, Ops printed a flightplan, and the pilot keyed each waypoint in manually.
What Ozarks crash?
GB
What Ozarks crash?
GB
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AINS-70 History
Now to AINS-70:
There once was a booklet titled, "Everything you wanted to know about AINS-70, but were afraid to ask." Kinda' wish I still had a copy.
The Area Inertial Navigation System, AINS-70, was a milestone in commercial air navigation, and ahead of its time. It could fly the airplane hands-off from takeoff to touchdown. The FMS, Flight Management System, in the 767 a decade later, built on the concept of the AINS-70. In fact,the FMS copied significant parts of the AINS-70, including the CDU.
The AINS-70 was a collaboration of the KSSU group of airlines, McDonnell Douglas DC-10 group, and Collins Avionics.
There were two identical Control Display Units, CDU, located in the center pedestal. Each one consisted of a monochrome CRT, a full alphanumeric keyboard (non-qwerty), and line select keys. It displayed route, progress, performance and status info.
The two Navigation Computer Units, NCU, were located in the electrical and electonics equipment bay below the flight deck. They were about a foot wide, nine inches tall, and two feet deep, and weighed in excess of 60 pounds each. They contained plug-in modules along either side. The two NCU performed all calculations independently and communicated for comparisons.
Non-Volatile Memory consisted of two magnetic core memory modules, roughly 8 inches tall, 3 inches wide, and six inches deep. Each one had a capacity of 8 kilobytes of data, and they were 4-bit bytes, IIRC. Each bit was held by a tiny ferrite donut with five wires passing through it, and all the donuts were arrayed in a three dimensional grid. Being magnetic ferrites, they were not expected to survive a severe mechanical shock.
Two Flight Data Storage Units, FDSU, were located in the hat closet at the back of the cockpit. Each FDSU was a transport for a magnetic tape cartridge, which contained all route data. Swissair was the keeper of all KSSU member route data for the whole world, some 13,000 routes. Updated tape cartridges every provided on a 28 day cycle. Each route was identified with a five digit number. 92649, for example, might take you from Anchorage to Seoul.
Position sensors feeding the NCU included radials from dual VORs, distances from dual DME's, and data from three LTN-58 ISU, Inertial Sensor Units.
OPERATION:
To align the AINS-70, the pilot would enter the 5-digit route number. The computer would then bring up and display the route info. The pilot would select gate number of the departure airport from a list, and the NCU would then direct the alignment of the 3 ISU. One NCU was primary, and the other was automatically crossloaded for backup.
It took a noticeable amount of time for the NCU to build the route, selecting a swath of VORs and DMEs along the route. Once the route was complete, the pilot could select the SID and altitudes to fly. STARS were available for selecting at any time, also.
Once engaged for navigation, the AINS tuned the VOR/DMEs automatically, and navigated based on best inputs.
Once beyond VOR-DME reception, it relied solely on the three ISU. This was years before the LTN-72 triple mix became available.
AINS-70 to ANTARCTICA:
Participating airlines paid Swissair for creating the company routes and for update service. Swissair maintained the data base and Collins Avionics updated the tape cartridges. ANZ chose not to have routes created for the Antarctic flights, as it was only a few waypoints, and "What could go wrong?
The AINS-70 could be operated almost like a triple mix INS. That meant, however, the ANZ pilots had to enter full lat/long for probably their first time in a DC-10. No matter how many times the crew of 901 might have checked the numbers in the CDU to the numbers on the company flight plan given them, it was always right.
They "merely" failed to compare the numbers on the company flight plan to a chart.
-----------
GB
There once was a booklet titled, "Everything you wanted to know about AINS-70, but were afraid to ask." Kinda' wish I still had a copy.
The Area Inertial Navigation System, AINS-70, was a milestone in commercial air navigation, and ahead of its time. It could fly the airplane hands-off from takeoff to touchdown. The FMS, Flight Management System, in the 767 a decade later, built on the concept of the AINS-70. In fact,the FMS copied significant parts of the AINS-70, including the CDU.
The AINS-70 was a collaboration of the KSSU group of airlines, McDonnell Douglas DC-10 group, and Collins Avionics.
There were two identical Control Display Units, CDU, located in the center pedestal. Each one consisted of a monochrome CRT, a full alphanumeric keyboard (non-qwerty), and line select keys. It displayed route, progress, performance and status info.
The two Navigation Computer Units, NCU, were located in the electrical and electonics equipment bay below the flight deck. They were about a foot wide, nine inches tall, and two feet deep, and weighed in excess of 60 pounds each. They contained plug-in modules along either side. The two NCU performed all calculations independently and communicated for comparisons.
Non-Volatile Memory consisted of two magnetic core memory modules, roughly 8 inches tall, 3 inches wide, and six inches deep. Each one had a capacity of 8 kilobytes of data, and they were 4-bit bytes, IIRC. Each bit was held by a tiny ferrite donut with five wires passing through it, and all the donuts were arrayed in a three dimensional grid. Being magnetic ferrites, they were not expected to survive a severe mechanical shock.
Two Flight Data Storage Units, FDSU, were located in the hat closet at the back of the cockpit. Each FDSU was a transport for a magnetic tape cartridge, which contained all route data. Swissair was the keeper of all KSSU member route data for the whole world, some 13,000 routes. Updated tape cartridges every provided on a 28 day cycle. Each route was identified with a five digit number. 92649, for example, might take you from Anchorage to Seoul.
Position sensors feeding the NCU included radials from dual VORs, distances from dual DME's, and data from three LTN-58 ISU, Inertial Sensor Units.
OPERATION:
To align the AINS-70, the pilot would enter the 5-digit route number. The computer would then bring up and display the route info. The pilot would select gate number of the departure airport from a list, and the NCU would then direct the alignment of the 3 ISU. One NCU was primary, and the other was automatically crossloaded for backup.
It took a noticeable amount of time for the NCU to build the route, selecting a swath of VORs and DMEs along the route. Once the route was complete, the pilot could select the SID and altitudes to fly. STARS were available for selecting at any time, also.
Once engaged for navigation, the AINS tuned the VOR/DMEs automatically, and navigated based on best inputs.
Once beyond VOR-DME reception, it relied solely on the three ISU. This was years before the LTN-72 triple mix became available.
AINS-70 to ANTARCTICA:
Participating airlines paid Swissair for creating the company routes and for update service. Swissair maintained the data base and Collins Avionics updated the tape cartridges. ANZ chose not to have routes created for the Antarctic flights, as it was only a few waypoints, and "What could go wrong?
The AINS-70 could be operated almost like a triple mix INS. That meant, however, the ANZ pilots had to enter full lat/long for probably their first time in a DC-10. No matter how many times the crew of 901 might have checked the numbers in the CDU to the numbers on the company flight plan given them, it was always right.
They "merely" failed to compare the numbers on the company flight plan to a chart.
-----------
GB
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The "Ozarks" accident is the one referred to your post numbered #387. I'm just curious to know whether DC10 pilots, as at November 1979, were aware of the potential risks of the AINS as regards the human inputs.
Which was the piece of gear that enabled investigators to prove that the crew correctly entered the coordinates listed on their flightplan? Was it the "NCU", or did the "Non-Volatile Memory" miraculously survive the impact?
Which was the piece of gear that enabled investigators to prove that the crew correctly entered the coordinates listed on their flightplan? Was it the "NCU", or did the "Non-Volatile Memory" miraculously survive the impact?
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Sorry to confuse, ampan; I'm pretty sure now that VOR was renamed to Rich Mountain VOR. It was not a DC-10, but a two pilot commuter plane, IIRC. It was a big enough plane to have a CVR.
In fact, most of that post #387 is non-pertinent if the military reporting point was named BYRD, and not MCMDO, as I remembered.
Discounting Korean Air, I don't remember another serious accident or incident with the KSSU DC-10 fleet. There was one occasion where an ISU with a stuck non-significant data bit in its ground speed output would cause its valid to go on and off. Somehow that slewed the computed position to where the plane missed the inbound gateway by about 60 miles.
The algorithm in the NCU required the word to be invalid for 6 consecutive times before the data was tossed, but had to be valid only once in six times to be counted. It was straightforward to change it so that once an invalid word was received, it had to be valid for six consecutive times before it was used once again.
While "impeccable" it may not have been, the AINS-70 was pretty darned good. The plane would always arrive well within the gateway from overseas, and begin updating as soon as VOR-DME signals were received. It would faithfully guide the plane onto the ILS, even tuning that. The pilots were pampered, I tell you; pampered - spoiled.
I'll get to the crash recovery later...
GB
In fact, most of that post #387 is non-pertinent if the military reporting point was named BYRD, and not MCMDO, as I remembered.
Discounting Korean Air, I don't remember another serious accident or incident with the KSSU DC-10 fleet. There was one occasion where an ISU with a stuck non-significant data bit in its ground speed output would cause its valid to go on and off. Somehow that slewed the computed position to where the plane missed the inbound gateway by about 60 miles.
The algorithm in the NCU required the word to be invalid for 6 consecutive times before the data was tossed, but had to be valid only once in six times to be counted. It was straightforward to change it so that once an invalid word was received, it had to be valid for six consecutive times before it was used once again.
While "impeccable" it may not have been, the AINS-70 was pretty darned good. The plane would always arrive well within the gateway from overseas, and begin updating as soon as VOR-DME signals were received. It would faithfully guide the plane onto the ILS, even tuning that. The pilots were pampered, I tell you; pampered - spoiled.
I'll get to the crash recovery later...
GB
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Oh, there was one more. As ANZ and then the KSSU group began shedding their DC-10s, they went to other carriers that did not have everything in place to assure pilot proficiency. Even Aloha operated a single one in 1983, mixed in with their 737-200 fleet.
It was June 1984, that an AINS-70 equipped Continental DC10 departed KHNL for Guam. They got as far as Wake Island, didn't like the look of the navigation and turned back, dumping fuel and putting the full load of pax in a hotel. It was said that the pilot never took the plane out of Heading Select mode, duh.
Adding to the confusion was the fact that the FAA had moved the HNL VOR off the field some five miles, then back on - a few times. Swissair got lost in the movements and had the VOR location on the data tape at the wrong location. That skewed the navigation by a couple of miles, but it would have washed out long before they got to Wake Island.
GB
It was June 1984, that an AINS-70 equipped Continental DC10 departed KHNL for Guam. They got as far as Wake Island, didn't like the look of the navigation and turned back, dumping fuel and putting the full load of pax in a hotel. It was said that the pilot never took the plane out of Heading Select mode, duh.
Adding to the confusion was the fact that the FAA had moved the HNL VOR off the field some five miles, then back on - a few times. Swissair got lost in the movements and had the VOR location on the data tape at the wrong location. That skewed the navigation by a couple of miles, but it would have washed out long before they got to Wake Island.
GB
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Definitely pampered compared to the DC8, which was operated by AirNZ for most of the 1960s, on very long routes over the Pacific. There's no doubting that a DC8 captain would be regularly looking over his navigator's shoulder, whatever the navigator's repution might have been.
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In chapter 18 of Verdict on Erebus, Mahon was standing close to the tower looking towards the crash site and says, quote,
"It was there I came to the conclusion, as I stared at the mountain in the sunliut clear air, that the approaching airliner must surely have been visible on the radar in the tower as it turned away to the west on its first orbit.
The track of the aircraft, as it emerged from behind the mountain and flew out to my left almost to the coastline of Cape Bird, must have shown up as a series of "blips" on the radar screen at the tower, because, as I could see from where I stood, the line of sight between the tower and the aircraft had been uninterrupted, I could see no alternative the thats conclusion". unquote
Does anyone know if the radar aerial was on the top of the tower, and what the rpm of that aerial was ?
"It was there I came to the conclusion, as I stared at the mountain in the sunliut clear air, that the approaching airliner must surely have been visible on the radar in the tower as it turned away to the west on its first orbit.
The track of the aircraft, as it emerged from behind the mountain and flew out to my left almost to the coastline of Cape Bird, must have shown up as a series of "blips" on the radar screen at the tower, because, as I could see from where I stood, the line of sight between the tower and the aircraft had been uninterrupted, I could see no alternative the thats conclusion". unquote
Does anyone know if the radar aerial was on the top of the tower, and what the rpm of that aerial was ?
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Since they were never able to establish vhf comm contact, it's unlikely they were ever line of sight to McMurdo. And that's one more hint Erebus was in the way.
I've seen ATC radars that interrogate about every 12-13 seconds.
GB
I've seen ATC radars that interrogate about every 12-13 seconds.
GB
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Henry Crun,
" It was there I came to the conclusion, as I stared at the mountain in the sunliut clear air, that the approaching airliner must surely have been visible on the radar in the tower as it turned away to the west on its first orbit"
Very good eyesight, the aircraft track would have been at least 20 miles away, on the 3D reconstruction it is most unlikely to have provided a return to McMurdo radar, if it did it would only have been for 30 to 60 seconds. All this was covered in the US District Court,Washington DC by Judge Harold Greenes enquiry.
Typical of the conclusions that Justice Mahon jumped to. To make a statement like that, and then to follow it up with a suspicion of another cover up by the McMurdo controllers because the facts never fitted in with his assumptions.
" It was there I came to the conclusion, as I stared at the mountain in the sunliut clear air, that the approaching airliner must surely have been visible on the radar in the tower as it turned away to the west on its first orbit"
Very good eyesight, the aircraft track would have been at least 20 miles away, on the 3D reconstruction it is most unlikely to have provided a return to McMurdo radar, if it did it would only have been for 30 to 60 seconds. All this was covered in the US District Court,Washington DC by Judge Harold Greenes enquiry.
Typical of the conclusions that Justice Mahon jumped to. To make a statement like that, and then to follow it up with a suspicion of another cover up by the McMurdo controllers because the facts never fitted in with his assumptions.