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Post by Erik on Feb 21, 2019 5:28:00 GMT -5
Another interesting one Ken, thanks. I like what you did regarding the later departure and low visibility. These things you could have easily changed in FS but you dealt with them in the most practical way, as one would have had to in reality. Well done!
Erik
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Post by connieguy on Feb 21, 2019 6:25:26 GMT -5
Many thanks again, Erik. I use dynamic real world weather files and accept whatever they produce. However, in reality I suspect that this flight would not have taken place until the visibility at Mururoa had cleared; or, of course, they might well have had Ground Control Approach.
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Post by Tom/CalClassic on Feb 21, 2019 10:21:32 GMT -5
If there was a printed NDB approach for the airport most of them would allow landing in 2.5 nm visibility, so you might have made it. Staying within 2.5 nm of the runway while circling to land might have been tricky in a Connie, though.
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Post by connieguy on Feb 22, 2019 11:03:07 GMT -5
Navigation by sun and sextant can be very effective in finding small islands, as we have seen, and if the line of position is abeam it is also a way of checking that the aircraft has reached the vicinity of a particular point, although the process only places the aircraft somewhere on that line. A definite fix requires not one line of position but two, and for that navigation at night is more suitable because of the availability of a number of different heavenly bodies. This might easily mask the fact that one can run down lines of position at night too. On the night of 23rd March 1951 PG Taylor, his crew and Frigate Bird II flew from Mangareva to Easter Island. Taylor's subsequent account of it was clearly based on entries in his log book and he records that they took off at 02:26 UTC. At 04:59 he estimated that they would pass 10 miles north of Oeno Island. 'Half an hour before Oeno was due I went back to the blister and took a sighting of Canopus away in the south. Next in brilliance to Sirius, the brightest of the stars, Canopus is a useful star for navigation. Bearing slightly west of south, it gave us a line running right through Oeno from the aircraft's position; so I decided to run down this line and pass over Oeno...' I give below a screenshot from Stellarium for that place and time and the resulting line of position mapped on Google Earth. I also give a line of position based on Pollux, which was also visible, but not in the right place for Taylor's purpose. When I return to flying by night I shall keep in mind this slightly different way of using the stars.
Canopus was slightly west of south, as Taylor says.
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Post by connieguy on Mar 10, 2019 11:09:36 GMT -5
This may be my last post in this thread, because I have reached a point where I think I have learnt astro-navigation in FS9 reasonably well and therefore have little more of value to say. I will start this post with an image of two sextant shots taken in the Pacific, because there are features of the Beaumont Bitzer sextant which I have only come to fully understand over a period. Although purists may recommend three shots for a good fix I am finding that two are perfectly adequate. The first of them should be the course line, which should derive from a heavenly body with an azimuth near to 90 or 270 degrees. This is then followed by the speed line based on an azimuth which is close to 0 or 180 degrees - that is near to the longitudinal axis of the aircraft, whether fore or aft. However Beauumont and Bitzer recommend that the speed line is the one which should be done as closely as possible to the fix time with the course line preceding it. The line drawn on the actual chart (below) is the line of position not the azimuth and in this example the azimuth was 206 degrees, and the resulting line of position (-90 degrees) is at 116 degrees and therefore represented by the horizontal line which falls from left to right. It is recorded as being -25 miles from the assumed position (shown under LAT, LONG and represented by the centre of the chart) and once the heavenly body has been centred in the bubble you know immediately what the result is going to be from the difference between the elevation at the assumed position (entered under Azimuth) and the real elevation (bottom right) used to centre the bubble in the eyepiece. Here the real elevation is 25 minutes less than the assumed one and that means we have flown beyond the assumed position by 25 nautical miles. If the real elevation had been greater than the assumed one that would have meant that we have not yet reached the assumed position by whatever distance is shown. The gauge shows minus results by a minus sign, but there is no plus sign to indicate the reverse - there is just no sign at all. Rather confusingly perhaps, minus indicates you have gone too far, not as one might think that you have not gone far enough. It will also be noticed that the two lines of position (at 90 degrees to the azimuths) cross at almost right angles and that I have moved the small circle on the chart as near to the crossing point as I can, whereupon the chart tells me that my real position is S (-)17 0, W (-) 151 4 (these figures are minus because I am south of the Equator and west of Greenwich). It is, of course, this true position that really matters, because that is the one which tells you where you actually are (give or take a few miles, sometimes). Having now learnt how to navigate by taking sextant shots of the sun during the day (less satisfactory than flying at night because you only have one azimuth) and how to find a particular place during the day by flying along a line of position derived from the sun (see above), I have recently returned to navigation at night, but this time not using fictional stars as I did previously, but real ones seen from the aircraft and identified by means of the program Stellarium, which is running simultaneously from a usb drive on my laptop. The assumed position entered in the sextant must be entered in Stellarium too, and the precise time of the shot, while turning the viewpoint initially to the direction in which the aircraft is flying. Once all that is done you should and do see in Stellarium exactly what you are seeing through the windscreen. In this context I am happy to use ndbs where they existed at the points of departure and arrival, because this accurately represents what was done in the early 1950s. Two recent flights were from Samoa to Tahiti and back. As in the past I have created waypoints at intervals of 200 nm to provide me with weather reports and assumed positions and I show below the planned track via these waypoints as represented by Google Earth. Although I started off some weeks ago by entering my fixes on physical charts I now find that Google Earth shows the latitude and longitude lines so clearly that I can work out the fixes from this by viewing it in the aircraft pdf viewer and without actually marking them on a chart. This next illustration is of the Plan G breadcrumb trail from the second flight, a distance of 1311 nm. There was a brief period intially when the stars were not visible and the sun rose when I was 400 nm from the destination so they were not visible again, but by this time I was for practical purposes home, though as the breadcrumb shows I did drift south slightly. Weather was almost consistent headwinds which required only a point or two of adjustment to the magnetic headings, but slowed me to a groundspeed of around 230 kts rather than the true airspeed of about 250. I used 230 in calculating the flying time between the waypoints on my E-6B, which returned about 53 minutes and this seemed accurate. In addition to the computer the other vital aid is my stopwatch (i.e. kitchen timer) which tells me when the required time has elapsed. My starshots at around waypoints 024, 023 and 022 all suggested I was slightly north of track and I made small adjustments to the heading to compensate which are just about visible on the breadcrumb. At waypoint 021 the assumed position was S 15 13, W 165 6 and the sextant returned S15 5 W 165 5 (it could not return 6 because it works in multiples of 5). I noted at the time that this was almost dead on and the breadcrumb shows that I in fact passed directly over the waypoint. Finally, some comment on actually seeing the stars. I flew at 12,000 feet and stars may be obscured by cloud and haze, in which case the sextant cannot be used. I am using a modified FS9 stars.dat file, as I said at the start of this thread, and in clear visbility this shows the constellations perfectly well, though all the stars look the same size - there is no variation in brightness as in real life and nor does one see the planets (I believe they do appear in FSX) though as these are shown in Stellarium I see no reason not to use them. What one is looking for, of course, is constellations which have a shape so distinctive that their identification is beyond doubt, and you only really need two, although things can get very difficult if there is patchy cloud which obscures some stars and not others. On the Tahiti-Samoa flights I used the constellation Scorpio for the fore and aft shots (fore travelling east, aft west) and in particular the star Acrab which is part of that constellation. For the beam shots I largely used Crux, and the star Acrux, in the sky to the south, another constellation with a distinctive pattern.* My confidence in using the sextant has grown significantly in recent weeks. Once you know what you are doing astro-navigation delivers, as it has done for so many centuries and will continue to do. That is partly why I believe the US Navy has recently reintroduced its study.
Only after completing the flight did I read in the Army Air Forces navigation manual (p.266): 'The constellations in the northern hemisphere which should be remembered are the Big Dipper, Cassiopeia, Leo, Cygnus or the Northern Cross, and Pegasus... The constellations in the southern hemisphere to remember are Scorpio and the Southern Cross or Crux.'
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Post by chris_c on Mar 10, 2019 13:01:42 GMT -5
This has been a great read; both fascinating and useful. Having dabbled with the Beaumont Bitzer bubble sextant but never achieved your level of competence I am very grateful for this thread and expect to return to it often. Thank you and fly safe.
Chris
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Post by connieguy on Mar 10, 2019 13:21:33 GMT -5
Thank you very much, Chris. It is good to know that there has been an appreciative audience out there.
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Post by warbaby on Mar 14, 2019 10:28:49 GMT -5
Thank you Connieguy for this fabulous thread. I have had the sextant in some of my aircraft but never took the time to really discover it. Now with your instruction and Andrew Crowleys videos, I can't wait to give it go. Allen
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Post by connieguy on Mar 14, 2019 12:14:30 GMT -5
Thank you very much Allen. As I hope you will discover, there is a feeling of rightness about doing things that way, Ken
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Post by Erik on Mar 16, 2019 18:56:03 GMT -5
Yes, what a gread thread this is. It made me understand how the whole system actually works. Of course I also installed the B&B sextant in some aircraft and can use it routinely now. For the time, the application has been limited to simulating position fixing by a wireless operator. I assume convenient azimuths and elevations to achieve that and it delivers the closest match to that part of vintage navigation that I can think of, in the sim.* Later, I will follow your guidelines on how to achieve maximum realism in celestial navigation, including actual identification of constellations and stars. A very big thank you to all who have made this possible. Erik * Edit: let me rephrase that. I like it as a substitute for having a wireless operator at work for the fix, while still being involved myself in that part of naviation. 'As real as it gets' HFDF is also available for the sim, as Stearmandriver just happens to mention here on CalClassic!
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Post by connieguy on Mar 17, 2019 6:40:47 GMT -5
Erik, Thank you for your support throughout this project. You mention the 'as real as it gets' HDF, which I did not know about, and I watched the Stearmandriver (a.k.a. Andrew Crowley) video, where he illustrates the Weatherships Gauge at length. This is available on the A2A Constellation Forum apparently only for FSX and Prepar3D. I have downloaded it but not tried installing it in FS9, because on the face of it there is nothing additional to Tom's Weatherships add-on, except in providing the kind of loop antenna used in the 1930s (and you can get this from the Austin-Bitzer RDF gauge, which is for FS9 and is on Flightsim). Naturally people simulating 1930s navigation (as I know you do) will find this of value, but I believe (correct me if I am wrong) that loop navigation had been superceded by the late 1940s, which is the earliest period I operate in. Good luck with identifying the stars. I think you may find that it is the last touch in making the whole thing seem pretty real, Best wishes, Ken
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Post by Erik on Mar 18, 2019 17:26:35 GMT -5
Ken, Many thanks again to you too. I obviously agree with you there. I had forgotten about the RDF gauge for FS9, that is indeed a more logical choice. For the time, on relatively short flights, I think I'll keep the sextant to simulate (a sim within a sim...) a crew member calculating the fix, as opposed to having to take the bearings and do the calculations. When I get to using the sextant the way it is meant to, I certainly expect the extra thrill of actually identifying stars and navigate by them! This again brings me to how fascinating it is to see it all come together. It is totally obvious to me now why a long flight over really open waters would be flown at night and one along a chain of islands by day. I also came to understand, right here, how using the sextant basically comes down to determining what the angle of our local horizontal plane on the earth is by using the known position in space, as seen from the earth's surface, of stars or the sun. Based on that outcome and by using the smart unit that the nautical mile is, it makes for a very clever system to determine one's position. Moving on to course lines and speed lines, it isn't hard to see why it's best to start with the first one. And all of that can be replicated to a high degree in our venerable fifteen-year-old desktop simulator. Another side step to radio direction finding maybe: I think there are two types of it.* FSAviator explains how the 'gps' system of the 1930s was using bearings taken by ground stations on aircraft transmissions, which were then relayed back to the crew (all through morse of course). There was no other airborne equipment involved. Using a loop antenna works the other way around: a ground transmission from a beacon is required and the crew finds its relative direction from the plane using the aerial. I believe that is what these RDF gauges simulate and this later evolved to ADF (Automatic DF). I haven't delved into what the weather ships provided, perhaps both.
Thinking of it, the radio range and later the VOR were in turn sophisticated ways of doing something similar as the vintage methods of the thirties, only much more precise and convenient: a ground station providing bearings from a fixed point to the aircrew.
Ground-based direction finders (DF stations) remain in use even today, for instance to show cross bearings on radar screens with every radio transmission from an aircraft, simplifying their identification for the air traffic controller. Aditionally, they can be used to provide navigation help to lost VFR pilots. These are then generally VHF DF's (so not HF) or VDF in short. But I do think you are right on when the use of loop antennae was superseded by more modern equipment. It is one big and rewarding learning experience. Cheers, Erik
* Addition: watching the 2nd China Clipper video just now in which Andrew Crowley mentions exactly that.
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Post by connieguy on Mar 19, 2019 15:01:01 GMT -5
Erik, Your posts are always of interest, so thank you for the latest. I think it is FS Aviator who points out that HF/DF actually goes back to before the First World War, and that the Titanic had it as a navigational aid, a ship that size I suppose being easily able to carry what was presumably some fairly heavy radio equipment. I agree that the venerable 15 year old sim isn't doing too badly. My next project is replicating the earliest B.O.A.C. Constellation flights across the Atlantic. Their early Constellations were converted C-69s which had engines with two-stage superchargers and the ability to lean the mixture below Auto Lean. The much-hyped A2A Constellation for FSX and Prepar3D does not replicate this, but the Connie Team L049 for FS9 does, and it is possible to adjust the aircraft.cfg to produce this early version of the aircraft, with a maximum take-off weight of 86,250 lbs. My enjoyment in preparing for this has also been greatly enhanced because I have at last acquired a copy of Peter Marson's magnificent book on the Constellation. There are also the two Flight articles from 1946 which record one of B.O.A.C.'s proving flights. On the return leg from Shannon to London with a light fuel load the Flight journalist used his watch and a pocket altimeter to record climb to 2,000 feet in 1 minute 24 secs, and that is the sort of performance I seem to be seeing in this Connie Team version of the early 049, which might perhaps be described as a racehorse of an airliner before the edge was taken off its performance by the demands for greater and therefore heavier payloads. However, I shall need to do a few proving flights of my own to make sure I know how to get the best out of this fine simulation, and at the same time I can also experiment with the latest version of Manfred Jahn's wonderful Ground Control Approach gauge. When I eventually do the flights I hope and believe that the sextant and the weather ships will get me from Shannon to Gander safely. I may well do a detailed description of it, but that will be for another thread. Happy flights. Ken
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Post by Erik on Mar 19, 2019 16:31:31 GMT -5
Thank you, Ken! Enjoy the new adventure indeed, good luck with it and I suppose many here will much appreciate an account of it, in due time.
Erik
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Post by connieguy on Jul 29, 2020 11:19:08 GMT -5
Although this is quite an old thread and I have written on period navigation in more recent ones, I have returned here because I think it is simpler if all such contributions are in the same place, because there is now a little more to be said and because among the members of the forum are some who want to hear it. Others will remain wedded to the idea that pilots flew and navigators navigated, that the roles of the two never met and that therefore period flying does not involve period navigation, especially when nearly all aircraft come with the stock Microsoft gps which can readily be used as a substitute navigator; and with some justification when it is being used as a stand-in for period systems we do not have, the most obvious one being Loran. But broadly speaking the real world was not really like that, and not only because gps did not exist. I have recently acquired 'The Longest Hop: Celebrating 50 Years of the Qantas Kangaroo Route 1947-1997' (Qantas, 1997). One is reminded of what a fine airline Qantas is fairly frequently, but nevertheless there is some fascinating and valuable period detail, some of which almost certainly derives from those who actually operated Constellations and Super Constellations in the 1950s, and is very relevant to period flight simulation. Particularly interesting in the present context is this. Qantas Constellation crews usually consisted of 10 people, 3 pilots, 2 flight engineers, a navigator, a radio operator and 3 cabin crew. On long flights they relieved each other, and being singletons the navigator and radio operator were given their rest periods by pilots who also held licenses in one and sometimes both of their disciplines. Indeed, this was true of 'most Qantas captains' (p. 63).
The FS9 period navigator has the sextant and the driftmeter. He also has John Hewson's Flickr albums of historical airfield photographs and charts and a slowly increasing amount of information on the radio aids of the period, so much less extensive than they are today. A particularly useful site for this latter material when dealing with western Europe is the Military Airfields Directory, whose remit is rather wider than the title suggests, and not least here:
Since I last looked at this site the coverage has been extended to include Greece, and this has encouraged me to re-visit a route I last flew when I navigated by following a line on Plan G - Air France Flight 192 from 1957, titled the Champs Elysees, from Paris Orly to Tokyo via Rome, Tel Aviv, Tehran, Karachi, Rangoon, Bangkok, Saigon and Manila. It is not difficult to re-create the historical radio beacons if you have the bgl compiler from the FS2004 SDK and some time ago I made as FS9 flight plans two of the chief European airways of the period, Amber One and Amber Two, which ran south and north respectively between Glasgow Prestwick and the south of Italy. The first leg of AF192 was therefore easily obtained by deleting the points north of Orly and south of Rome Ciampino. From Orly, therefore, the route started by flying a reciprocal bearing from the Orly Range south to Moulins and Montelimar, where it dog-legged to port to cross the coast near Monaco at Mont Leuza. From there it proceeded to Elba and Ortebello and (leaving Amber One) reached Ciampino via the beacon at Urbe. There was also a Radio Range station just north of Ciampino. This was a longer route than an aircraft left to its own devices might have flown, and more expensive in time and fuel, something which caused adverse comment at the time, but it could be implemented entirely by radio aids, as could the next leg from Rome to Tel Aviv. It was here that the new information on Greece came in useful. I could have used Airway Amber Thirteen south of Rome but chose instead to fly to Ponza on Amber One and then south to Caraffa di Catanzaro, where Amber One ended. From there it was a choice between proceeding via Athens or Crete. On the map the latter route looks a great deal shorter but in fact is hardly so at all, and the Athens option had more radio beacons at this time. One of these which would have been extremely useful on the western coast of Greece was that associated with the air base at Araxos, except that our flight left Rome at 18:30 (UTC+1) and Araxos only operated between 05:00 and 17:00. After Caraffa, therefore, the next beacon was Corinth and then Athens Hellinikon and Rhodes. After that it was over 400 nm to Tel Aviv, although such a distance is perfectly feasible if weather reports give an idea of wind direction. When I did eventually pick up the Tel Aviv beacon I was north of track, but not to any great extent. Although essentially a radio aids flight, this second leg was also used to practise something that I have not often done in the past although it was a way of establishing the aircraft's precise position employed very frequently - the identification of a known point on the ground. Thus, the RAF's 'Air Navigation' from 1944 suggests that their navigators were expected to be able to recognise every coastal estuary in the British Isles. Consequently I took screenshots of the route as it crossed the Greek islands ready to use with my kneeboard pdf reader at the appropriate time. It may be that much FS9 scenery is too inaccurate for this kind of procedure, but about ten years ago the Greek Airports Project released excellent photographic representations of the archipelagos south and east of Athens,* and the unique shape of each island and their positions relative to each other are ideal for this sort of purpose. As the flight entered this area on the reciprocal of the Athens beacon there wasn't too much doubt where it was, but this was confirmed by a positive sighting of Amorgos in the Cyclades. Like establishing a position with the sextant, there was something about this that simply felt completely right.
Beyond that, there was almost certainly a reason why the flight left Paris in the early afternoon, because as a result the third leg departed Tel Aviv for Tehran at 02:20 (UTC+3) and an area I assume to have been devoid of radio aids could then be navigated largely by the stars. What follows from that is the interesting question of how they did the leg between Tehran and Karachi during the day. I have one or two ideas about that, but we shall see.
* Although the Greek Airports Project still has a website these files are no longer available.
On the leg between Ponza and Caraffa di Catanzaro, the western coast of Italy bathes in the evening sunlight.
Amorgos on the map and at night.
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