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Post by Erik on Jan 31, 2019 17:58:23 GMT -5
Well this topic keeps getting better with everything you post, Ken. Congratulations once more, on another great feat in your fascinating adventures. For the first time, I feel I have a real idea what celestial navigation is about and most of all, how versatile it is. The video you linked added greatly to that of course, thanks to mr. Crowley as well. As the topic has been somewhere in the back of my head throughout the past week, I was glad to at least grasp by myself how determining a LOP actually works, with reference to a heavenly body. That helped me understand the rest of what is explained above. It seems to me you are not far anymore from determining ground speed and track based on fixes, which I think would make celestial navigation complete. That way one could take all the captaincy decisions, that eventually determine if destination if ever reached, based on the outcome of the sextant shots. As a side note, the video demonstrates a broader interest in both classic flightsimming and fitting navigation than I was aware of, which is a nice surprise. Finally, the following is the quote of the day for me. In the meantime I am in the astrodome scanning ahead, although through this entire process I have never really believed that this could possibly work Many thanks, Erik
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Post by Defender on Feb 1, 2019 8:35:52 GMT -5
Hi, Sounds like good fun and a great way to occupy the long ocean sectors. As regards finally finding the island I suspect they used the local NDB and/or DF. I recall seeing this direction finding equipment in a late 50's visit to the Prestwick tower, a small screen that flashed a pointer to show the direction (but not range) of the aircraft's VHF transmission. It was a common aid in smaller airports. Capt P G Taylor's book "Frigate Bird" is also a good read in relation to remote Pacific crossings. Another useful read in relation to practical navigation accuracy is a 278 page report commissioned by the FAA in 1961 in connection with reducing North Atlantic separation standards, entitled "SYSTEMS ANALYSIS OF THE NORTH ATLANTIC AIR TRAFFIC COMPLEX". It covers the causes of position and track errors in great detail and reveals that between Gander and Shannon the standard deviation at 30W, half way, was between 5 and 15 miles and up to 20 miles at landfall. And that's with Loran and Consol coverage as well. It also reports feedback from one airline that its standard procedure was to ignore any track or heading correction of 2 degrees or less, presumably as the new heading may be no more reliable. The report is available to read online but if you want to download it you need to register. It's one of many I've saved from the US Government's Department of Transportation library over the years, a goldmine of information for anyone interested in historic aviation regulation and practice. Go to, dotlibrary.specialcollection.net/Loginand after you've registered and logged in go to CAA and FAA reports/FAA and BRD Reports then down to System Analysis etc. It will open only a single page headed Abstract and to open or download the full report you need to click on the pdf icon at the top of the page. Bill
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Post by Tom/CalClassic on Feb 1, 2019 12:30:09 GMT -5
Thanks Bill, very useful info. I've downloaded that file and will look for others.
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Post by connieguy on Feb 1, 2019 14:36:53 GMT -5
Erik, Many thanks for your continued support. It is true that the people actually contributing to this thread are a handful of the usual suspects, but I think this is tending to mask the interest in the subject. It has now had over 1100 views and among the recent threads on the Chat forum this is only exceeded by Jorge's very useful Historic Airfields and Navaids in Europe, which has had over 1300. Thus, quite a lot of people seem to be interested in these things, even if they may never contribute. Bill, Thank you for the recommendations. Hardback copies of Frigate Bird are rather expensive, but there was a paperback edition in the late 1980s and I have ordered a copy of this from Australia. I have also downloaded the Systems Analysis report from the DOT archive and look forward to reading it. There is nothing like reading literature from the period, whether it is 'Fate is the Hunter' or instruction manuals on navigation issued during the war or anything else. Now for today's flight, which was a failure but an informative one. After yesterday I decided that I would fly from Johnston Atoll to Hickam Air Base (PHNL) employing as my only radio aid the NDB at Johnston which I would use to settle myself on the correct track at the beginning. Otherwise I would use a sun line of position to bring me to Hickam and then land VFR. Astro-navigation is heady stuff, and I am in danger of developing a 'radio aids are for kids' mentality. However, this time I used a real weather file, but left the visibility settings in FSUIPC set to Unlimited, which meant that the visibilty was controlled by FS Global Real Weather. The two extracts from the Plan G breadcrumb trail show what happened: I was aware from the weather reports that there would initially be a side wind from the left and then a rather stronger one from the right, but decided I could deal with this by flying a constant heading of 060 magnetic. In fact, as the breadcrumb shows, the wind must have strengthened as I approached Hawaii, although at the point at which I turned along the line of position I was only 16nm away from the intended track, which is not a big error from a flight of 700 nm. I decided to cruise at FL150 to keep me clear of cloud, and in the initial stages there were patchy clouds below me but the sea was always visible. Unfortunately as I neared Hawaii I found myself flying over dense cloud with nothing visible below at all. I was not concerned about this because I assumed I would see the peaks of Hawaii peeping above it, blissfully unaware, because I had not researched it in advance, that the highest of those peaks is at 13,000 feet. The sun line of position method worked beautifully as it did yesterday (though in this case I flew the reciprocal of the azimuth minus 90 degrees) and the result was that I passed within 5nm of Hickam without seeing it. I was reluctant to descend into the murk because of the danger of seeing nothing at all, but should in fact have descended below 10,000 feet before turning on the line of position and continued to descend as I travelled along it. In fact, the breadcrumb shows that as I turned I was only 34 nm from Hickam. I think part of my lack of confidence in not descending was that I am still trying to shed my disbelief that this line of position method actually works, when it is now quite clear that it does. The breadcrunb ends at the point where I had flown far too long without seeing anything and abandoned in the belief that I had missed Hawaii altogether. Not a bit of it. Trust your sextant!
I shall try this flight again with a different weather file tomorrow. We are having a bit of winter in the UK at the moment, as Bill will be aware, and this is a good time to be doing these things.
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Post by Defender on Feb 1, 2019 16:40:15 GMT -5
Hi, Glad that's all of interest. Your comment about missing Hickham reminds me that there's an accident report in that DoT library that demonstrates the hazards of dead reckoning and inattention big time. So if you still have trouble sleeping then go to the aircraft accidents section then 1949 and last item Transocean Airlines (Ernie Gann's pals). The link at the end opens a PDF of the original report and a chart. In your case you might get more favourable winds at lower altitudes, at least westbound. Glad your thread gets so many reads and clearly of much interest but few will have much to add. Bill
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Post by connieguy on Feb 2, 2019 15:55:23 GMT -5
That is because few know as much as you do. I don't know much but I like learning. This is just to tidy up what happened yesterday. I did repeat the flight with a different weather file which warned me of sidewinds from the south for about two-thirds of the flight veering northerly near Hawaii. I adjusted my headings accordingly and it worked fairly well. I also descended much earlier (as the aircraft slows down, of course, this has to be allowed for in the travel time estimates, although one can use the sextant at any time). Once again I came in on the correct line but didn't see the mainland of Hawaii until I was quite near and quite low. Hickam isn't the easiest of places to land and I didn't make a particularly good job of it, but the crucial navigation aspect of the flight went perfectly satisfactorily. breadcrumb trail: first sight of land:
I looked at some of the accident reports when I was doing the Air France Super Constellation crash in 1954. They can certainly be very informative. Yesterday I read one about a Flying Tigers DC4 which crashed in the Pacific after faulty manipulation of the fuel tank selectors and crossfeeds caused three of the engines to fail. Only two of the five crew survived, to be were rescued after 30 hours in the water being bitten by sharks. I will certainly look at the Transocean one, thanks for pointing it out.
Ken
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Post by connieguy on Feb 9, 2019 15:43:41 GMT -5
PJON Johnston Atoll to PLCH Christmas Island in the R7V-1 Pegasus, 3-4th February, 1956. Scenery by Mike Stevens and Cal Classic, repaint of the Jahn/Connie Team R7V-1 by Frank Gonzalez. Thanks to them all, and to Andrew Crowley. This was my third attempt at this flight, the earlier ones having foundered because although I thought I knew about Sun Lines of Position already, in fact there were things about which I was confused. Out in the field, the slightest confusion is likely to lead to failure. The Andrew Crowley video helped to sort this out, and also plotting the lines on Google Earth as he does, which helps to clarify what is happening. The route starts off from Johnston with three waypoints 200 nm apart. After that it goes through Palmyra Island and Fanning Island (PLO6 in the plan) before reaching Christmas Island. A Sun Line of Position marked on the chart for Palmyra Island ought to allow us to correct any error in our position and fly straight over it. After that dead reckoning will probably get us to Fanning Island and probably Christmas Island too; even so, I add another Sun Line of Position there just in case. Here is the Plan G Plan together with the Google Earth graphics, although the Line of Position at Palmyra for 01:00 I added later, and only that for 00:30 was there during the flight; however, I did have the necessary azimuths and elevations written down for other times. Ready to go. The R7V-1 Pegasus at runway 23 at Johnston Atoll as a Navy C-54 comes in to land. About 22:00 UTC, 3rd February, 1956. The Plan G Flight Plan. Pol6 is Fanning Island. The two Google Earth Sun Line of Position Charts for 1: Palmyra Island. 2: Christmas Island. The second one shows how the Line of Position is worked out from the Azimuth, 90 degrees being subtracted from the latter to get the former. I am a little surprised at how accurate dead reckoning can be. At the waypoint CH3 I was 9nm south of track, and 14nm south of it at the point where I turned along the LOP for Palmyra. I started taking sun shots for Palymyra at 01:00 UTC but using (for reasons given above) the bearing details of the LOP for 00:30 which has it on a True Heading of 134 degrees. As nine degrees of magnetic variation needed to be subtracted I turned to a heading of 125 Magnetic at 01:08 UTC and at 01:18 saw Christmas Island dead ahead of me. There was something uncanny about this as it emerged from the mist, and perhaps rather fortunate, but I flew straight overhead without any change of direction. I had seen these features in the sea on the two earlier flights and knew that they meant I was nearing Palmyra Island. 01:15 UTC Palmyra Island dead ahead 01:18 UTC. I could see it more clearly at the time than I can now. After that I used dead reckoning to get to Fanning and apparently passed slightly to the East of it - screenshot below - although according to the Plan G breadcrumb trail I was to the west of it. It looks as though Plan G and Open Street Map or (probably more likely) FS9 don't have it in quite the right place. I was fairly confident that dead reckoning would bring me to Christmas Island safely enough, not least because it is relatively big, but started taking sunshots for the Line of Position marked on the map. The distance to the LOP slowly came down but this tended to confirm that I was in the right place and at 02:50 I sighted Christmas Island dead ahead. By then I was cruising at 9,000 feet from the original 11,000 and put in a descent loop before landing on runway 8 at 03:14 UTC. Flight Time 5 hours 10 minutes, 3,241 lbs of fuel left from the original 18,057 lbs. Fanning Island passes to starboard. The Plan G breadcrumb trails for the first and second parts of the flight, the latter showing the turn along the LOP for Palmyra. The Plan G breadcrumb trail for the final part of the flight, showing the aircraft passing Fanning Island to the West. Taxiing in at PLCH: I will just add that I now have P.G. Taylor's Frigate Bird. It is only necessary to read a few pages to realise that he regarded the sextant as king and on occasion ignored radio aids so that he could use it.
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Post by Erik on Feb 9, 2019 17:29:35 GMT -5
Another great one. That sight of Palmyra is one to behold. Can confirm FS9 has Fanning Island exactly 21 NM due west of where it should be.
Cheers! Erik
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Post by connieguy on Feb 12, 2019 6:12:33 GMT -5
Erik. Thanks for the information on Fanning Island. PLCH Christmas Island to NTTG Rangiroa in a 1955 MATS R7V-1, 7th February, 1956. Scenery by Mike Stevens and Cal Classic, repaint of the Jahn/Connie Team R7V-1 by Frank Gonzalez. Thanks to them all, and to Andrew Crowley. For this flight I thought of replicating Andrew Crowley's trip to Bora Bora, but he did most of that by night using star shots whereas I want to fly by day using lines of position from the sun. I therefore need intermediate islands between PLCH and the destination and go for Rangiroa (NTTG) as the destination and Malden Island and Millenium Island as the intermediates. Leaving just about dawn this will give me good lines of position at the intermediates but not at the destination, where it will be noon and the azimuth of the sun will change by the minute. Flight plan below and the lines of position plotted on Google Earth. You will notice underwater features visible near the flight plan and I wonder if these will be visible in the sea, but they are not. Plan G breadcrumb trail also below: Initially all goes well and winds are light. The breadcrumb shows that I kept well on track and as I approach Malden Island I start taking sun shots. They show the line of position off to the left, as it should be, and with a decreasing distance as I get nearer. At the point where it shows me 10nm away I see the Island slightly off to the right from the cockpit. I don't think anything could illustrate better the use of lines of position from the sun than the screenshot below. At Millenium Island (see the breadcrumb above) I am slightly further away and it crosses my mind that if the cloud had been a little denser I might not have seen it. I know from what happened later that at this point I should have altered course to pass right over it, the reason I did not being doubts about whether FS9 has it in the right place. Rather ironically, as it turns out, it has. The result of this was that I did not get on a proper heading to the destination and slowly drifted east. There are a number of atolls in the area of the destination and I have little doubt that I will have no problem seeing them, so little that I do not bother even writing down the frequency of the Rangiroa NDB. However, cloud increases and although I have descended to 8,000 feet from 11,000 the minutes pass and I see nothing. The stopwatch is one of the critical instruments in this context and when it gets to 50 minutes after the final checkpoint I know that I must have overflown the atolls. This would not have happened if I had not disdained the radio aid, because I am in fact 27nm east of destination and the range of the NDB is 37.5 nm. With great reluctance I turn on the Synthetic ILS gauge installed in the aircraft only a few hours ago. I tune it to Rangiroa and the orange needle kicks into life - yes, the atoll is behind me to starboard. I then use the gauge to turn back, descend and land. This is something of a repeat of what happened on my recent flight to Hawaii. I am reluctant to descend because it will restrict my field of view, but by not descending the clouds and poor visibility prevent me seeing the destination. However, whether I would have seen it if significantly lower is not certain, and there is an argument that I am simply trying to do something I should not have been trying to do. This is almost exactly the area in which P.G. Taylor flew Frigate Bird II. Yes, he loved his sextant, but he was very careful with weather reports, especially in an area without radio aids, and knew that in the wrong weather without radio (Frigate Bird had radios aplenty if there was anything to tune to) things might well go wrong (Frigate Bird, paperback edition, pp. 56-7). The same awareness that the weather can kick you in the teeth emerges from Gann's Fate is the Hunter. However, there was at least one other alternative. If I had timed my arrival at the destination for mid afternoon there would have been a useable line of position which I could have flown along, the evidence so far being that this method does deliver the goods. Flight time 5:22. Fuel loaded 17,681 lbs, remaining 2,097 lbs. Cruise at FL110 at 1700 bhp. The next flight will be a short hop from Rangiroa to Tahiti. I like the Pacific in summer. About to land. I am slightly too high but make a decent touchdown on the earth runway.
Later that afternoon. Tahiti to port at 6,000 feet with the island of Mo'orea to the right. I am using the Tahiti 75 nm NDB and fly over Mo'orea before turning for a landing on runway 04. Doing it without the NDB would have been perfectly feasible.
The Cal Classic scenery provides a Polynesian welcome.
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Post by Tom/CalClassic on Feb 12, 2019 11:34:44 GMT -5
Interesting flight. Since you were among the atolls when you decided to check the ILS gauge, I would suspect if you had trusted your plot and descended to a lower altitude you might have seen them, and from a map of the islands could have navigated back to the airport?
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Post by connieguy on Feb 12, 2019 12:28:17 GMT -5
Yes, very likely. Not descending to a lower level when the stopwatch told me I needed to was certainly a mistake. I was running Google Earth on my separate laptop and this to an extent replicates the charts the real navigators had and what they saw when they looked out of the windows. The atolls tend to all have their own shapes and FS9 does represent these quite adequately, so vfr at low level would have been perfectly feasible as visibility low down was fine (the screenshot of the landing shows this). Unfortunately, once I realised I had gone wrong I wanted to land as quickly as possible (that is, I threw in the towel), and the ILS gauge facilitated this, but of course a real pilot would have had to persevere with visual recognition and had I done so I might well have achieved what the gauge did. I am ignoring the existence of the NDB here, because part of what I am doing is trying to find out what can be achieved without such things, and the conclusion so far is a lot more than I originally expected. However, as I said above, there were weather conditions which must have been insurmountable, even if now I think about it that was probably not true of this particular flight. Still, I shall persevere. This is the most interesting thing I have ever done in flightsim, and the Pacific islands are an ideal location for it.
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Post by connieguy on Feb 17, 2019 9:08:10 GMT -5
There seem to be times in learning navigation when it is necessary to take a step back in order to take a step forward. I have recently had two flights which were essentially failures, the first from Tahiti to Rarotonga when I missed the island by about 26 nautical miles and then found it by switching on the NDB. This was a repeat of the Rangiroa flight and it happened because I relied upon dead reckoning to deliver me directly to the destination rather than deliberately off-setting the course and then running in on a line of position as I did at Johnston Atoll. In fact the latter is not just a good idea. it is a way of doing things which is absolutely essential. On the first return flight to Tahiti I did offset to the south and ran in on the line of position, having unfortunately failed to allow for magnetic deviation of about 13 degrees in setting the heading. I still hit Tahiti, because it is big and easily seen, but didn't deserve to. The second attempt got it right. Illustrated below is the line of position for 01:00 UTC 10th February, 1956. In fact I was in the correct vicinity at 00:00 UTC and therefore used a slightly different azimuth to calculate the line of position. When I shot it at 00:00 the sextant gave me a distance of +40 nm, which meant I still had 40 nm to go at a true airspeed of about 250 knots. When I shot it again 8 minutes later the sextant returned 0 nm. I was dead on the line of position and therefore turned from a heading of 062 magnetic to one of 348 magnetic, quite a tight turn and I expected that it would throw me off course very slightly. Although the weather had been clear earlier it was now cloudy and it can be difficult at a distance to distinguish between clouds with a dark lower edge and land. However, I had by now descended to about 4000 feet and eventually saw Tahiti dead ahead. When I switched on the NDB the compass needle showed its position about two points away from dead ahead, so I would have seen it had it been much smaller. The moment that makes all the effort worthwhile - Tahiti visible through the clouds. And the Plan G breadcrumb trail, which shows how the line of position method points you straight at the target.
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Post by Tom/CalClassic on Feb 17, 2019 10:25:56 GMT -5
Nice job, just like the old navigators tell you to do, and an excellent example of why they do.
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Post by Erik on Feb 18, 2019 20:13:00 GMT -5
It is indeed. And the same principle as making sure you hit for instance a coastline south of destination, to follow it northbound to get there visually. I always love the reliability of such simple but clever methods.
Erik
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Post by connieguy on Feb 20, 2019 15:46:56 GMT -5
Tom. Thank you. You could not have said anything that would have pleased me more. Erik. What you say is a reminder that it was important for navigators to look outside the aircraft for whatever clues they could pick up. The RAF training manual from 1944 has a whole section on the kinds of things that could be useful, especially in correlation with charts (Chapter III. Sect. 35 - rivers, lakes and railways were strongly recommended, and golf courses, which might also serve as emergency landing grounds). My latest flight was from Tahiti to Mururoa Atoll (NTAA to NTTX). This is a biggish atoll, I did not expect to have too much trouble finding it, and nor would I have done in normal conditions. I actually set off two hours later than I intended and this required a steeper turn to get on the line of position from Mururoa than was ideal - a heading of 330 magnetic. I descended to about 2000 feet and waited for the atoll to appear but it did not and I became convinced that I had done something wrong, so great has my confidence become that the line of position method works flawlessly when properly implemented. Visiblity was poor by this time and I finally switched on the Mururoa NDB only to find myself looking at a needle that was pointing dead ahead. Still nothing appeared but I was now within range of the airport and tuned them in to ask for landing only to be refused because they were experiencing IFR conditions. I could have tried landing using the NDB but was aware that this is not in line with the runway and was doubtful (quite correctly as it turned out) whether I would be able to see enough to find it. In these circumstances, and because the sextant had flawlessly done all it could do, I felt justified in switching on the Synthetic ILS gauge to give me the equivalent of a Ground Control Approach. This got me down, although I was only 2.6nm from runway 26 when I finally saw the runway lights in the murk. This flight was enjoyable and rewarding, but it did confirm that using only pre-radio aids will not work if visibility at the airport is below a certain distance. The Plan G breadcrumb. I took the line I did because there were small atolls to be seen to the south of the route which were useful as evidence of where I was. However, once near Mururoa I could have approached from the north, which would have made the turn to the line of position easier and considerably shortened the flight. And the landing, assisted by Karol Chlebowski's wonderful Synthetic ILS gauge:
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