B377 Autopilot

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Jason210
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B377 Autopilot

Post by Jason210 »

Hi

I'm curious as to why the autopilot in the B377 is so basic? If you compare it with the B-17's autpilot, or other autopilots of the era such as the Sperry, the b377's is quite limited.

Jason
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MTFDarkEagle
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Re: B377 Autopilot

Post by MTFDarkEagle »

Well, it is basically the C1 extremely simplified: you can do the same things?

What would ya expect, a full FMS with 3 CDU's? :P
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allonan2361
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Re: B377 Autopilot

Post by allonan2361 »

MTFDarkEagle wrote:Well, it is basically the C1 extremely simplified: you can do the same things?

What would ya expect, a full FMS with 3 CDU's? :P

And a Garmin 8)
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Raebo
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Re: B377 Autopilot

Post by Raebo »

It's not as basic as you may think.
In flight planner click GPS, or fly VOR to VOR for nostalgic reasons using the fabulous A2A Map for situational awareness.
Set your Nav 1 and Nav 2 to the runway ILS you want to use
So now back to flying GPS, go to FSX map, you will see a magenta coloured line to your pre-flight planned destination. ( Find route )
Put your pointer on this line and drag it over to an intersection ( triangles ) you may need to connect multiple intersections to get lined up right down the ILS feather for your runway choice. (remember to zoom in)
Now go dark screen ( terrain) on your A2A map screen about 35 miles out to see your intersections just keep clicking they will show up.
Remember to zoom in as well.
Take off, engage auto pilot, hit ctrl N, Nav 1 Hold on.
The Strat will turn to the heading that you pre-set and fly to your destination following that magenta line.
Very important.
Because you set up the FSX GPS to follow intersection pathways to line up with the ILS, do not turn off the GPS/Nav as it will do all the work for you.
Only when you are lined up perfectly flying ""toward the runway"", then and only then go to Nav/loc, it will do this automatically the second you hit ctrl A approach mode.
Once lined up with the runway, about 20 miles out I try to fly in at 1800 to 2200 feet to meet the ILS/GS from below, Remember always intersect the GS from below.
Its fussy sometimes and will not engage I think its speed, so keep her at about 120 knots.
About 35 miles out your NAV-1 will sound letting you know it is now communicating with the ILS runway frequency that you set before take off. Set your heading indicator to the runway heading this gives you a good visual when your on final that you are on track.
I use to hit Ctrl O, Localizer Hold and the Strat would kick out of GPS/NAV and go to NAV/hold and follow the signal. But it was sloppy until I started engaging the more powerful Ctrl A approach mode.
Because the localizer signal by itself is weaker than the combined signal that the LOC/GS puts out I go right to Ctrl A approach mode now. Not sloppy at all. Corrections are aggressive which is good as an approach is time sensitive.
Keep your altitude hold on and set at 1800 feet, 20inches of manifold, or about 130 Knots, gear down you will then start to see the flight path boxes coming into view right above you that you set for 3500 feet ( NAV 1) before take off.
As the Strat is about to intersect these boxes it will automatically kick off the altitude hold button, now let out a few flap settings to get the nose to drop and it will fly the boxes right down the ILS/GS.
At 400 feet kick off the AP.
At ten feet raise the nose ever so slightly staying at 20 inches until the rubber meets the runway.
This is a non-precision approach, FSX does not allow for precision approaches or hands off approaches as far as I know.
A very good thing in my opinion.
It is also my opinion that those Strat pilots would have loved to have had a GPS in those days.
This way I get the full meal deal, using todays technology, but flying a historic beauty.

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Jason210
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Re: B377 Autopilot

Post by Jason210 »

No I didn't expect to find an FMS or Garmin :-)

I expected a large and complex airliner like the B377 to make greater use of the technology that was available at the time, as exemplified by the C1, especially with respect to landing instruments. Curious...
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Jason210
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Re: B377 Autopilot

Post by Jason210 »

Raebo wrote:It's not as basic as you may think.
In flight planner click GPS, or fly VOR to VOR for nostalgic reasons using the fabulous A2A Map for situational awareness.
Thanks for the interesting post.

Actually I'm a retro freak so I don't use the GPS, nor the A2A moving-map nor flight the plan facility in FSX! I make my own flight plans with Google earth and notepad then print them out along with a map showing beacon locations :-). Then I navigate using dead reckoning, triangulation and VFR. You should try it - it's a real challenge! I've also started getting interested in astral navigation but I don't know how accurate the stars are. The seem to be accurate but whether they are accurate enough to navigate by is another question.

Still I'm surprised that many of the FSX autopilot functions work - such as approach hold. However I will not use anything that was not available to the pilots of these aircraft. As far as I can see, the B377 has an extremely spartan autopilot. It simply does heading hold when engaged (on) with a heading adjust lever, and then offfers an optional altitude hold but heading hold must be on for the altitude hold to work -- which seems a bit odd.

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Re: B377 Autopilot

Post by MTFDarkEagle »

Jason210 wrote:I've also started getting interested in astral navigation but I don't know how accurate the stars are. The seem to be accurate but whether they are accurate enough to navigate by is another question.
yes, they are accurate. In our B-17 MP flights (http://a2asimulations.com/forum/viewtop ... 79&t=21872), David (our flightleader most of the time), regularly uses celestial navigation. Check this as well: http://a2asimulations.com/forum/viewtop ... 37&t=22881 , might be interessting
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Jason210
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Re: B377 Autopilot

Post by Jason210 »

Thanks for the links about celestrial (as opposed to "astral" :lol: ) navigation. Looks great fun and I'm going to be playing with this tonight!
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Re: B377 Autopilot

Post by lonewulf47 »

And at all: the Strat's Autopilot is not as basic as one might think. It includes the C1 features like Heading Hold (not only a wing leveler) and Pitch Hold (much better than V/S hold...) plus one more important thing: barometric altitude hold. As far as I know the C1 was a purely gyroscopic controlled autopilot which did NOT feature barometric altitude hold.

Operationally it is not much of a difference whether you do corrections on your heading using a turn handle or a heading bug. NAV coupling however - which was a big step forward - came a few years later. As you might have read in the books the A2A Strat is covering the B377 in it's purety without the ongoing modifications during it's life. That's also why there is no DME although on later models and on the C97 it has been introduced of course. That's where the fun comes from :lol: basic navigation with a basic aircraft... :wink:

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bigjuicyspider
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Re: B377 Autopilot

Post by bigjuicyspider »

Jason210,

I just did the Celestial Nav thing not too long ago (http://a2asimulations.com/forum/viewtop ... 37&t=23897). You must get yourself a copy of something called "Autostar X". This will give you real stars for any given date or time. You run this before your flight and then when you enter the sim, they are all there, and accurate.

The Bubble Sextant guage available for FS does a pretty convincing job of "faking it". You enter your assumed position, and the assumed position of the star and it gives you a line of position regardless of whether or not the star is actually there...so even if you used default stars and made up the az/el of the star on the fly, it would still work. Now that is cheating, of course, so the method I used was to establish some house rules: I used AutoStar X and a freeware planetarium program, and put in real data. So the stars actually were there, in the correct place, at the correct time, and I made sure that I could actually identify them as such before allowing myself to take a reading, however artificial that reading might actually be. After getting my current position, I used a variety of freeware apps, as well as a manual chart, to get the course headings, and ETAs refined. It was a pain in the rear to do all that, but I'm glad I had the experience. The whole thing was also very time critical. It is definitely taking your simming to the next level, and a good way to bore your friends and family over the dinner table.
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Jason210
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Re: B377 Autopilot

Post by Jason210 »

bigjuicyspider wrote:Jason210,

The Bubble Se'xtant guage available for FS does a pretty convincing job of "faking it". You enter your assumed position, and the assumed position of the star and it gives you a line of position regardless of whether or not the star is actually there...so even if you used default stars and made up the az/el of the star on the fly, it would still work.
Thanks for the information. I noticed that it's not a true sight reduction instrument like a real sextant. So I was also looking out the window at the constellations in FSX to find the star before taking a reading. I guess it's the same kind of thinking. Problem for me is that I don't like to interupt the flight to look at other programs, so I am trying to use my iPhone for reference.

I've just got two very interesting apps for it. The first is a very simple program called "Stars" which simpy shows the night sky, with constellations and main stars. It shows the hour angle and declination in the centre of the screen, the celestial equator and ecliptic. It's very simple to use for the bright stars.

Another app is called "iNA", which stands for iPhone Nautical Almanac. That actually costs $, but it's worth it. It works exactly the USN's online almanac, giving you the star, sun or moon cooridinates.

Neither of these apps, once installed, require an Internet connection to do the computations. All reference info is in the app. That means that the iPhone effectively serves the purpose of physical almanac - nothing more, well, just more convenient.

There is also a se'xtant available for the iPhone, which again does not use Internet or GPS or any other external reference, but obviosuly that's not going to work in FSX! Interesting that someone has bother to create a means of ascertaining one's position without the use of GPS or Internet databases.

The only difficulty I still have is in knowing which stars to use at the flight planning stage. I use Google Earth to plan great circle routes, but don't know how to determine which stars I'm going to see on that route.
bigjuicyspider wrote:I used a variety of freeware apps, as well as a manual chart, to get the course headings, and ETAs refined. It was a pain in the rear to do all that, but I'm glad I had the experience. The whole thing was also very time critical. It is definitely taking your simming to the next level, and a good way to bore your friends and family over the dinner table.
Well, at this stage I'm happy just to get an accurate fix on my position and take it from there. You're right about boring friends and family. I don't talk about it unless the subject of my interest in "computer games" comes up (grrr), and then I try to explain...

It is interesting why we do this. I think for me it's a reaction against the present day touch-button acessibilty of knowedge. I don't want to lose touch with these alternative traditional techniques, where all you needed was a few instruments and your brain!
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bigjuicyspider
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Re: B377 Autopilot

Post by bigjuicyspider »

"The only difficulty I still have is in knowing which stars to use at the flight planning stage. I use Google Earth to plan great circle routes, but don't know how to determine which stars I'm going to see on that route."

Here is what I did:

First I determined the distance of the great circle route. For SFO to HNL, that was 2080 nm. Then I decided that I wanted a "fix" at Hour 1, a fix at Hour 2, Hour 4, Hour 6, Hour 7 etc...

Based on those fixed time constraints, and speeds of the 377, I tried to work out how far along the path I would be at each fix, and then using a variety of online, and offline tools, I was able to work out a precise latittude and longitude for that fix along the great circle. There is a way that I go about doing that, which would take far too much time to explain, but if you play around enough with the tools available, you should probably be able to figure out how to get "waypoints on a great circle" (you might google that)

Then using the Stellarium program, you are able to punch in those lat/lons, and the time you expect to be there, and get the az/el of the star. It takes you to the place of the Observer, including altitude, at the time you specify, and shows you the night sky there, on the screen. It is a graphical program, where you locate the star on the screen and click on it...an alternative to using the almanac. (Apparently some planetariums use this wonderful freeware program to project stars on to the ceiling) This is how I was able to determine exactly what the night sky would look like at any given time/place along my great circle route. I simply wrote down the az/els of the stars I expected to see at each of my fixes, and punched those very same numbers into the Bubble Xtant at the appropriate places and times during the flight.

And they were there, in FSX! It was very cool to be able to say, "okay, here is Orion's Belt, and I'm looking for the red star, Betelguese, several degrees above it. And next, I'm looking for the bright star, Sirius, near the horizon, off the port quarter." Very awesome.

I did these things before the flight, for the most part, so I wasn't online looking at almanacs or anything. I used a second computer to do all my calculations...so I never had to pause the sim, or use multiple windows.

(as an aside, I even used Stellarium outside, on a laptop, during the last lunar eclipse. It was rather neat watching the moon start to eclipse on the computer screen, at exactly the same time as it was doing in the real world :D )
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Jason210
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Re: B377 Autopilot

Post by Jason210 »

bigjuicyspider wrote:Based on those fixed time constraints, and speeds of the 377, I tried to work out how far along the path I would be at each fix, and then using a variety of online, and offline tools, I was able to work out a precise latittude and longitude for that fix along the great circle. There is a way that I go about doing that, which would take far too much time to explain
If you use google earth ( I suppose that's me cheating) then finding great circle routes and their lengths is not a problem, and the longitude and latitiude of any waypoint along it is just read off. What charts are you using for reference for this part? For the moment I prefer not to go in this deep since because the other part is complicated enough. Eventually I'll try to learn it all.

To work out the time taken to get there should be distance/speed, but that would have to be ground speed. There's another problem they had to figure out - ground speed based on current airspeed (taking into account the wind, of course)!
bigjuicyspider wrote:Then using the Stellarium program, you are able to punch in those lat/lons, and the time you expect to be there, and get the az/el of the star.
I wonder how the old pilots used to do it? Did they have books with star charts? I have an A4 star chart that you can download and print out from USNO. It looks like mercators map of the world but shows star projections instead. There must be a way to use this - by taking into account your longitude and the time. Another approach could be to have a good look at the FSX sky during early on the journey, and pick out certain constellations that are going to be around for a long time. So long as you can identify a couple of stars then you look them up in an almanac.[/quote]
bigjuicyspider wrote:I simply wrote down the az/els of the stars I expected to see at each of my fixes, and punched those very same numbers into the Bubble Xtant at the appropriate places and times during the flight.
What if the Azimuth of the star is not a whole degree? I seem to be unable to enter minutes for the azimuth on that gauge. Do you have this problem?

I shall definitely have a look at this Stellarium program. The "Stars new" app for the iPhone is ok but you can't enter your location, orientation or time or anything.
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bigjuicyspider
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Re: B377 Autopilot

Post by bigjuicyspider »

Jason210,

The Sxtant doesn't let you enter the Azimuth of the Star in minutes, only degrees. I don't know why that is; Perhaps the azimuth of the star isn't relavent to the real-world calculations in order to derive a Line of Position.(EDIT: I didn't phrase that correctly..the az of the star most certainly is relavent, but for the purposes of the sim, I guess degrees only is sufficient for charting purposes within the sim. The azimuth isn't something that is actually dialed into a real sxtant, I don't think, although I don't know a darn thing about real sxtants) Don't know...but don't worry about it, since the figures you enter in are for all practical purposes, fake, anyway.

To get the ground speed (making sure not to look at the Shift-2 display, of course), I used the "Virtual E6B" that you can download from dc3airways.com. In addition to E6B functions, it also has a handy tool that allows you to enter 2 different sets of lattitudes and longitudes, and it will give you the distance between them, and just as important, the Rhumb Line course between them. Since you know the time between fixes, you can derive your groundspeed from that. Then, use the traditional functions of the E6B to compute your TAS from the temp and pressure altitude...from these functions you should be able to derive the headwind component, and deviation angle.

I use this tool on a second PC, but I wouldn't be surprised if you can find something like that for the Iphone...I know there is a plain E6B, but what you need is a tool to compute the Rhumb Line Course and a Rhumb distance between two Lat/Lon pairs.

I'm not familiar with the program you are using to populate the FSX sky with stars, but AutoStar X will place the stars and planets accurately, and easily identifiable for a given date. This matches up pretty much precisely with what you will see in Stellarium, so you should have no trouble predicting what stars are in view at any given time and place during your flight, assuming the clouds aren't in the way. (I decided using almanacs, and slide rules, and doing the calculations to get a LOP by hand was better left to somebody from the 1950s who went to navigator's school...I think there are several of those old guys that frequent these forums, so maybe they have something to say about this thread, who knows)
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Jason210
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Re: B377 Autopilot

Post by Jason210 »

Thanks! I seem to be getting the hang of it now.

Somewhere, in the attic, I have a real E6B calculator that I had when doing flying lessons many years ago. Gonna see if I can dig it out!
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