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#501
03-19-2010, 12:37 PM
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Thanks for the excellent information (even illustrated with pictures). So that's what the round coil below the fuselage is for - believe it or not but I have been trying to find that out through google for about two months (every week or two I'd go hunting). At first I thought maybe it was ordnance related, but later realized it could not be that.
I did not expect the model itself to be animated  I meant that I never realized there were directional antennas & how radio compasses work, and was surprised to find out that the Bf 110 was 'getting it' (full radio compass) while all the other fighters don't. Would be nice to be able to have it shot off or damaged, it would make navigation a bit more challenging unexpectedly. But that is unlikely as well.One thing is unclear to me - while I understand the reason, the usefulness of being able to have the antenna turn and the way that antennas transmit differently depending on angle to source - how does the 'auto' G-2 antenna work compared to the manually turned? Do we use buttons to electrically move it, and it then automatically turns itself when the aircraft turns, or does it home in on the strongest signal, or on a selected frequency-signal? Or does it actually keep spinning around at a set rate and some kind of electronics make the radio compass point to the strongest signal in the frqeuency? |
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#502
03-19-2010, 01:28 PM
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Automatically motor driven loop will try to turn and stay at the direction which gives null signal or no signal. Operator would tune the receiver to the frequency of certain beacon, but we have simplified this and selection is based on beacon ID.
I'm pretty sure that all war time automatic D/F-equipment had a manual mode too because of meaconing. Meaconing will get the automatic mode confused. But we haven't planned any manual mode even simple meaconing is possible now. Google is your friend: http://en.wikipedia.org/wiki/Radio_direction_finder http://en.wikipedia.org/wiki/Direction_finding http://en.wikipedia.org/wiki/Radio_navigation And the most epic navigation document ever which makes you appreciate the Art of Navigation. http://aafcollection.info/items/docu...0198-01-00.pdf
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#503
03-19-2010, 02:05 PM
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Quote:
The last link is a forbidden hotlink, but I'll dig it up (and other things) from the website it resides on.The AF Loop antenna would still have to deal with figuring out which 180 degree direction is the actual heading of the beacon, but I read on wiki just now that modern systems have an auxilliary "sense antenna" to solve that problem. Navigation in those auto AF planes must be a lot more convenient than flying the fighters for sure.. The 110 seems to be stuffed with various navigational aids, with redundant functions if any other fails. But there's never been any use of either of these things until TD and 4.10. Going to be fun exploring a whole new side (area) of the airplane (instrument panel).There's a few more strange antennas sticking out from the 110 G-2, and I have been unable to identify any of them. Maybe the manuals I found today from WW2 will shed light on that. One of them is bound to be the sense antenna. |
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#504
03-19-2010, 04:30 PM
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From my limited experience on a friend's FSX installation and payware WWII 3rd party add-on aircraft, the process goes something like this.
First, you tune the nav radio to the frequency of the beacon you want to use. The radio panel had various controls for com radios and nav radios. At the time, there were no VOR beacons like we have today to supply information of your course's track relative to the beacon, so all you had were the so called NDBs (Non Directional Beacons). These can tell you the beacon's bearing relative to your aircraft, but not on which track radial you are flying on. That means they are fine for flying directly to and from a beacon, but they can't be used for more complex navigation. For example a modern VOR beacon can indicate to you when you intersect a certain radial (imagine a top-down map view with the VOR beacon and 360 lines extending away from it, one for every degree of the compass). This way, you can use VORs even if you are not flying directly to and from them. For example, let's say you need to exit the airway you are flying on at a predetermined point and then make your approach to the airport. If there's a VOR with sufficient range nearby, the navigation documents published for air traffic control and navigation would clearly mark the exit point with the VOR frequency and intersecting radial. To keep it simple, let's say that the exit point lies due east of the VOR beacon. So, instead of having to estimate/calculate your exact position and distance from the airport to begin your approach, you would simply keep flying on your course (usually with the aid of another VOR you fly directly to on a certain radial) and tune the 2nd nav radio to the other VOR. On the 2nd VOR instrument, you would choose radial 90 or radial 270 (it's the same, all it changes is the to/from setting on the instrument) and when the line was centered you would know you are intersecting the selected radial. That means you're due east of the beacon and it's time to exit the airway. Of course, in WWII they didn't have such advanced beacons or the instruments to go along with them. These are all advancements that were made after the war, because of the increased civilian air traffic and the need to to be able to fly blind (at night or with bad weather), which is what gave rise to the IFR (instrument flying rules) specified by the international ICAO organization. However, WWII-style NDBs are still used today because they are simple to work with and much of the aviation traffic in the 50s relied on them for navigation. You can still deduce radials and precise fixed with NDBs, it's just that it's more difficult and takes more time, that's why VORs took the lead. So, in a WWII aircraft's radio panel you would have a 2-3 position switch to select the frequency band and then you would turn a smaller crank to fine-tune the exact frequency of the NDB. After that, you would turn another knob while watching the reception signal strength on an indicator in the panel. I think what that knob does is rotate that circular antenna you see in the belly of the 110. As you rotate it, the signal strength will rise, peak and then start falling, so you rotate it back and forth until you get the peak value. Depending on the angle of the antenna, the electronics can deduce the bearing of the beacon relative to your aircraft. So, when the navigator is finished tuning it, the pilot looks at his instrument panel and watches what was then called a radio compass (now it's referred to as ADF-Automatic Direction Finder). That gauge has a compass rose (actually it's bearings and not compass headings) along the rim, with a needle in the middle that points directly to the beacon, so just by looking at it the pilot knows where to turn to fly to the beacon. I guess there is some sensing mechanism to deduce if you are flying towards or away from it, because the needle always points to the beacon without ever getting confused, no matter what heading you turn to. So, in a hypothetical B17 mission the heavies would climb out to a certain rally point marked by a beacon, assemble the formation from the different bomb groups and head out towards the target. Take off, tune the nav radio to the appropriate NDB (things like that go in the mission briefing) and the pilot flies the plane in a heading that results in the of the needle in the ADF showing a bearing of zero/360 (directly to the beacon). They know from the briefing that they have to turn south-east to find the target (it's a short-range raid to occupied France today), let's say to a heading of 120 degrees. Here's the neat part now. When you are directly over the beacon, headings and bearings coincide. North of the beacon means north for you as well since you are directly over it. However, the moment you pass the beacon headings and bearings are reversed, because you are now flying away from it. So, if you want to fly a track of 120 degrees TOWARDS the target, you can simply fly a track of 120 degrees FROM the beacon. That means the reciprocal track/radial if you want to convert it to read towards the beacon, which is: 120+180=300 degrees, however we can't fly precise tracks without a VOR. What we do is, the moment we are over the NDB (the ADF needle will flip from zero to 180 degrees when you overfly it) we turn southeast until our compass shows 120. Our ADF will read 180 and not 300, because the ADF always displays bearings to the tuned beacon and not tracks in relation to them. Since the beacon is now behind us, it reads 180. After the bomb run, the heavies are going back home. This time they need to fly the reverse course, so they are flying a heading to 300 directly to the beacon and the ADF should show a bearing of zero. Here comes the reason VORs are better than NDBs now...i could have explained it on the route to target leg, but it would be more confusing because of flying away from the NDB during that leg. It's easier to explain when we are flying towards it because we don't need to calculate reciprocal tracks and so on. Let's say a wind is blowing from the west and it moves the bombers off course. How can they correct for it? If the beacon was a VOR, they would calibrate their instruments to fly on the 300 radial directly to the beacon. If the western wing is blowing you off course to the east, you would see the VOR needle moving left and be able to correct for it...the needle is the chose track in relation to your airplane, so it if moves left it means you are to the right of the correct course. But how do we do it with a simple NDB beacon and an ADF gauge? Ideally, in a no wind situation we would be flying a heading of 300 back to friendly airspace and since that is the direct course to the beacon from our position over the target, the ADF needle (which shows the bearing to the beacon and not our compass heading) would read zero. Now that the wind is blowing from the west, we are drifting away from our chosen track to the east. Well, our compass still reads 300, but our ADF needle doesn't read zero anymore. Actually, it's a bit to the left, reading a bearing of 330 degrees. This way we realize that while we are pointing the right way, there is a wind that's blowing us off course. To establish the correct track once again, we would need to turn left by a few degrees (as much as 30-45 for nimble fighters, but maybe no more than 15 for bombers in formation), then return to our original heading of 300. This results in a zig-zag pattern until we finally reach the coast and have some landmarks to navigate with. Better yet, we could turn the aircraft into the wind and neutralize it if it's coming from our forward quarter. So, let's say the western wind has stopped and we now have a wind that's coming from a mere 10 degrees left of our heading (we are flying 300, the wind blows from 290). It takes some experimentation to discover the correct offset, but it's simple. Turn into the wind in steps of 10 degrees and wait a bit, watching how the needles move. If the wind keeps blowing us off course to the right, the ADF needle will keep moving to the left. If however we manage to turn into the wind, the ADF needle will be stable. So, by making a small turn from 300 to 290, we can neutralize the wind component. Our aircraft flies a little sideways relative to the earth (it's NOT sideslip, that one is relative to the air while in this case we are talking relative to the ground) and our ground speed will be a bit reduced by flying into the wind, but we won't have to make constant corrections. Behold my supreme MSPaint skills for a visual explanation  Also, screenshot of a WWII era radio panel included. The ADF gauges are similar to those found on the pilot's instrument panel. Where it gets really weird though is how fighters did it. German fighters have a similar installation, but allied fighters usually navigated by listening to some kind of morse code. Not having a dedicated ADF gauge meant that the pilot would enable the voice output of the nav radio from time to time and listen in to the tones. For example, if he was to the left of his chosen course he would hear dots and if he was to the right he would hear dashes in morse code (or vice versa, don't exactly remember), or it could be any other kind of tone. For sure, not as accurate or easy as having an ADF gauge. |
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#505
03-19-2010, 05:28 PM
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#506
03-20-2010, 02:57 AM
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Structural Modelling
The addition of realistic structural damage & failure will be a real game-changer. Thx for all the good work Team Daidalos. You guys are awesome.
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#507
03-20-2010, 02:23 PM
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Quote:
Wouldn't determine the radial of a NDB be fairly simple? NDB bearing -180° = radial. You want to catch a 120° radial, fly until your bearing to the NDB bearing shows 300°. Or not? |
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#508
03-20-2010, 10:40 PM
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If you are interested in the history ofNavigation tecniques and equipment in general there are a few books i can recommend.
http://www.woodfieldpublishing.co.uk...n-uk/p177.html http://www.amazon.co.uk/Quest-All-we.../dp/1840372591 I have both, and they have really helped me understand navigation in ww2. also from time to time on e-bay you can get RAF navigation manual 1941 or 1944, i have the 1944 version picked it up (original copy, hardback) for about £10.00, its very comprehensive, although does not go into radio navigation much. regards slipper p.s almost forgot some free downloads here for radio nav systems in ww2 http://www.radarworld.org/books.html Last edited by slipper; 03-20-2010 at 10:50 PM. |
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#509
03-20-2010, 11:05 PM
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Take a look at the first MSPaint picture and note the enroute leg to target (the green arrow).
Bearing to the NDB is 180 degrees. Doing as you suggest, NDB bearing-180=180-180=0, so we should be on the 0/180 radial. However the bomber in the example is flying on the 120/300 radial. The thing with radials is that they are relative to the beacon's position. A 90/270 radial relative to one beacon is a totally different course than the same radial relative to another beacon. There still is a way to fly radials without use of a VOR beacon and the required gauges.You can still follow the ADF on a direct course to the beacon, but the reason radials are useful is because you can fly along a narrow corridor. So, let's say we want to fly the 300 TO/120 FROM radial to a beacon. In order to be on the 300 TO radial, the ADF should read zero bearing to beacon when the compass reads a heading of 300. That is, if when flying the radial's heading (300) the station is straight ahead (ADF shows zero bearing) we are on the correct radial. If the ADF drifts to one side then we know we are moving away from the radial and we can turn into it to intercept and track it again. It's just a bit harder to do with an NDB beacon than it is with a VOR, but it's certainly possible. I've done it on a friend's PC in FSX. We flew from Greece to London in a 1950s airliner that didn't have modern instruments. When all you have is ADF gauges, even if you tune a VOR station the extra information can't be displayed, so it was like flying exclusively on NDBs. Now i'm not very experienced in civilian flying. I only fly FSX on my buddy's PC every now and then, we schedule a trip of a few hours on an evening, order some pizzas and beers and take turns flying the route while watching a movie. What i mean is that if i can do it via ADF alone, then i'm sure everyone can. It will be real nice to be able to schedule missions online with some precision thanks to the NDBs. For example people will be able to fly indirect routes in their bombers and come in from unexpected directions, without having to rely on visual cues all the time. You could fly out over the sea for longer distances without fear of getting lost. |
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#510
03-21-2010, 10:23 AM
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Isn't it possible to just do triangulation from a single beacon to know one's position? Taking two measurements from the same beacon at an interval instead of using the bearing from two different beacons.
1. Fly a steady heading 2. Measure bearing to beacon 3. Take that bearing minus 180 degrees, and draw a line on the map from the beacon outwards. 4. Fly for a determined while longer (maybe 3 minutes and 15 seconds - knowing exactly how far we have traveled in our straight line). 5. Repeat steps 2 and 3. 6. We now know three angles (all). First is our heading and the bearing to the beacon at the time of measurement one. Second is the same but at measurement two. Third is the two different bearings from the beacon to our positions of the two measurements. And we also know the length of one side of the triangle - our own distance traveled between measurement one and two. http://www.mathsisfun.com/algebra/tr...triangles.html We can use the law of sines to find out the lengths (distance) between our aircraft and the beacon at measurement one and two), which are the two missing sides of the triangle. When those are revealed, we have our triangle drawn on the map, showing our distance from the beacon at the two measurements and the path our aircraft flew. |
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Linear Mode
