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LAX to Hawaii w/o using GPS - How?


davefr

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Actually, GPS IS standard these days. Even GA pilots carry hand-held GPS units they stick to the glareshield, just like you would in your car.

I know, this isn't what you want, just letting you know. GPS is a pretty "standard instrument" anymore. Not long ago, it wasn't, I understand. I remember when GPS first hit the market, I had to use it for my job. Had to have exact Lat/Long for some remote beacons, for correcting a radar's display to account for the movement of it's platform. The GPS we had was a large gym-bag full of electronics. It was as long as I am tall, and about 3' in diameter.

We had to go to location we were considering for the beacon, set up an antenna on a tall pole, and gather satellite data there for at least 2-3 hours, preferably more, then return to base, plug into a 286 computer and massage the data gathered for another couple hours to get the exact location.

Nowaday, GPS is a small, hand-held device. Incredible. You don't even need to check the satellite constellation info to make sure you'll have enough sats visible.

Thank you military for releasing GPS to the public!

 

Have fun, however you navigate.

Pat☺

 

When I was a kid during the first Iraq war (Desert Storm) I heard about GPS then. They used handheld units called Sluggers. If I can remember. I was about 10 or 11 at the time and I knew about dumb bombs. I thought to myself why don't they attach a GPS to the bomb and have a precision drop. Since every time I have an idea it comes to light, the JADAM was born. It's really just a kit I guess that attaches to a dumb bomb.

 

Several years ago I read an article about how DARPA was developing a small chip with a gyro, timer and accelerometer, an INS to be specific. This is the chip that will no doubt replace GPS. No more having to worry about signal reception or jamming. I think as of now we are way too dependent on GPS, and I don't think that's a good thing. INS is the way to go if you ask me. Subs, planes and missiles use it.

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Only at high airspeeds. At lower airspeeds, particularly over long distances, drift errors can be significant. Even surface motion of just a few knots can make a big difference.

 

What difference does surface drift make exactly? Drift we are talking about here is based on wind, not water. Our airplane is an AIRplane... potentially several or many thousand feet above the surface where the wind speed and direction can be completely different.

 

I agree there is a minor contribution to calculation from surface movement if one launches a smoke float or takes a sighting from a piece of driftwood but in general what is being calculated is wind drift and relative bearing, in order to apply a correction. But typical drift speed will be in the order of a handful of knots, so its relative effect on a plane going 125-325 kts is frankly, irrelevant. If one were flying a flying boat a few hundred feet above the ocean then it might have some meaning, otherwise it doesn't.

 

I understand what our OP is trying to achieve, but frankly, many replies here are just confusing the issue not helping.

 

The three basic principles at play are:

Knowing where you start from

Knowing where you're going

and

What route you need to take to get there.

 

Thats the broad picture. And two out of three are fixed points so relatively easy for even a novice to work out. But it's the third that has ALL the complication...

 

The finesse requirements are:

Knowing what the wind is doing at all phases of flight

What impact this has on course and heading

Knowing where you ARE at any given moment in flight.

 

Modern navigation makes this a push-button, continuously updated affair. And therefore easy.

 

In the past things were less easy and required calculation and re-calculation to enable update of knowing where you are, and understanding of what needed to happen to course and heading. That information was previously derived from star and sun shots and the use of a sextant; smoke floats or flares for some indication of wind drift at the aircrafts altitude (NOT sea level) and a stopwatch or clock. Aircraft carried a Navigator as they could dedicate their time to such matters and would typically produce a revised course-to-steer every half hour or so, to feed to the crew flying.

 

Maps were of limited use but could be used to provide present-position information that allowed calculation of where the aircraft IS, and using a protractor and ruler the direct course to steer to the destination. The Navigator then factored in wind speed and relative bearing to calculate `drift` then revised the course-to-steer so that the aircraft course would coincide with the destination.

 

In practice, radio aids were added as was direction-finding on non-navaid radio signals as early as the 1920's so that as long as one could navigate to a position within radio range, one could use it as a homing beacon.

 

Hope this makes things clearer.

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You CANNOT just head off in an initial direction over long distances, even in no wind conditions, maintain only an initial heading, and expect any degree of accuracy!

 

use FSPF and just put in KLAX as a departure, then PHNL as an arrival and let the FP show its proposed route - look at it as it crosses lines of longitude - the course is CONSTANTLY increasing over the whole route, and varies by about 30 degrees over that route. You must break the route into small segments to determine "chord lines" that vary new departure angles from incremental waypoints based on time enroute.

 

The FSFP is not great, BUT - it uses great circle math for calculations, considers magvar vs true courses, and that is the essence of long range navigation, by GPS or sextant, it is the same and the most accurate. Anything else is flat Earth nav, and one of the reasons why VOR radials, which are flat Earth, seem not to necessarily agree totally with a GPS course between two VOR's that are some distance apart. Of course magvar between two VORs affects this as well, though.

 

Plotting a course on a flat paper chart by hand is extremely inaccurate over long distances. You need to have extensive great circle tables to do an accurate course, or have a computer. It is a big deal - not easy.

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You CANNOT just head off in an initial direction over long distances, even in no wind conditions, maintain only an initial heading, and expect any degree of accuracy!

 

use FSPF and just put in KLAX as a departure, then PHNL as an arrival and let the FP show its proposed route - look at it as it crosses lines of longitude - the course is CONSTANTLY increasing over the whole route, and varies by about 30 degrees over that route. You must break the route into small segments to determine "chord lines" that vary new departure angles from incremental waypoints based on time enroute.

 

The FSFP is not great, BUT - it uses great circle math for calculations, considers magvar vs true courses, and that is the essence of long range navigation, by GPS or sextant, it is the same and the most accurate. Anything else is flat Earth nav, and one of the reasons why VOR radials, which are flat Earth, seem not to necessarily agree totally with a GPS course between two VOR's that are some distance apart. Of course magvar between two VORs affects this as well, though.

 

Plotting a course on a flat paper chart by hand is extremely inaccurate over long distances. You need to have extensive great circle tables to do an accurate course, or have a computer. It is a big deal - not easy.

 

 

Hence the incredible feat achieve by Kingsford Smith and crew...in 1928!

But hey, it’s a ‘game’ not real life, so try it and see. :)

 

I have a ‘Southern Cross’ replica I downloaded. I’ve been wanting to recreate the flight. One day I’ll try it.

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INS is an older system. The subs we had in the Pacific in WWII had it. I think the German subs did too. Problems with the older INS is they depended on spinning gyros, which drift. It's called Earth Rate Precession.

Since a gyro remains still in space once it's spun up to speed, and uncaged, and since the Earth moves through space in several directions, IE: It rotates about it's center, it orbits about the sun's center, it moves through the Universe, orbiting the Universe's central black hole, all at the same time. Thus, the gyro seems to drift. It's not really, it's environment does, but the effect is there.

INS systems need to be corrected every so often to compensate for ERP. The ones on planes have a magnetic sensor, and every so many minutes, seconds, whatever, the system compares the sensor's output to the gyro's, and corrects the system. I don't know just how subs do it, but it's probably similar. Plane's systems have to be told just what their latitude is, so they can apply the right correction. I wager newer systems use GPS to update the INS system once in a while.

Even "solid state", or laser ring gyros, have the drift problem. Same reason. Once they turned on, they sense the Earth's movements, as well as their platform's.

When a missile is launched, the system is corrected at the last second before launch. It won't drift signifigantly prior to impact. But even solid state gyros have the drift. It's inherent in the system. After all, even solid state gyros sense the various movements the Earth makes, in addition to their platform's movement.

 

I think all that is why the preferred method of navigation is GPS. No drift. INS is used as a backup, in case the GPS's electronics go wonky for some reason.

 

Sorry, I ramble...

Pat☺

[sIGPIC][/sIGPIC]

Had a thought...then there was the smell of something burning, and sparks, and then a big fire, and then the lights went out! I guess I better not do that again!

Sgt, USMC, 10 years proud service, Inactive reserve now :D

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INS v GPS

 

Right, INS is essentially the equivalent of dead reckoning - it's a leap in the dark and any unanticipated influences after the leap can't be accounted for. Likewise, GPS and cross-checking position visually are essentially equivalent because they are empirical observations of the current position. The HSI is an example of a hybrid system - the gyro is a dead-reckoning system that is periodically corrected by automatic observations (as you described, via a magnetic compass).

 

(P.S. I don't think it has been established that there is a black hole at the centre of the universe :) )

MarkH

 

C0TtlQd.jpg

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In the real world, airliners and military transports have three of everything -- IRS and GPS typically. Nowdays the IRS's are corrected by the GPS units to take out the earth rate precession errors described above. Airliners still need IRU's for the gyro flight instruments (heading indicator and artificial horizon). Other than that I suppose they could dispense with the IRU's entirely. The Garmin G1000 also has an IRU for the same purpose, although the navigation itself is done with GPS only.

 

Prior to all of that, in my early career in the C-141A with the Military Airlift Command, we had navigators as part of the crew and they used doppler, celestial, Loran, and bearings from vortacs and NDB's to augment the rest.

 

In FS, you could probably have avoided the miss you described by flying one heading all the way across, a heading roughly halfway between the initial mag heading out of LAX and the final one going into HNL. Based of course on one leg, direct. Splitting the difference like that might avoid the problem of the great circle heading changing constantly as you proceed. And fly as high as possible to improve your chances of receiving the VOR!

 

In the very earliest days, back when Pan Am Captain Ed Musik and his crew inaugurated the route from Oakland to Honolulu, they used celestial plus drift bombs. Drift bombs were flasks filled with powdered aluminum, which burst on impact with the water and left a large enough silver spot on the water surface that it could be tracked with a drift meter and the aircraft's track across the water determined. This way they could correct for wind drift. At night, a flask was used that was filled with a substance that would burn on impact and float, again enabling drift to be determined and thus aircraft track. They also calculated, as did Lindbergh, the correct mag heading for the great circle course every hundred or so miles. Knowing their drift angle the navigator could compute the correct heading to make good each leg's desired ground track. Both day and night, celestial navigation could provide longitude information, which gave them their ground speed; thus they knew when to turn to the next heading. Complex, to be sure, which is why they had the specialist navigator aboard -- the best of which was Fred Noonan, who would eventually be lost with Amelia Earhart several years later.

 

In both the real world and FS, you should be able to get close using a flight plan that has arbitrary waypoints often enough to define the various desired headings on the great circle route, and enroute times to dictate when to turn to the next heading. If you put a waypoint in roughly each 5 degrees of longitude you should be able to fly the flight plan headings for the flight plan times, and get pretty close. In the no-wind world of FS, you might be able to overfly the airport!

 

Let me know how it works out!

 

Tony Vallillo

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Avillilo,

 

As an old RW Marine Chopper Jockey we never had to deal with any of these long range weather or drift issues. 250 miles was about our max range.

 

So I am finding this question very interesting and totally outside my field of expertise. In order to increase my expertise, I'm totally into what advice anyone can offer. As I never did that long range flying RW, I hope to learn from this link!

 

Having said that, as I'm trying my best to sim RW, I "fly" RW weather conditions and use online downloaded every fifteen minutes weather.

 

IMHO, those who are trying to recreate this flight as close to accurate as possible must also deal with RW weather! (Which is probably most accurately found on the Real Time downloaded weather links.) If that be true, "In the no-wind world of FS, you might be able to overfly the airport!" as a response doesn't apply.

 

Rupert

Being an old chopper guy I usually fly low and slow.
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It's real easy.

You can fly to the destination in a straight line as well, it works just fine.

 

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Thing is, magneic variation has an effect.

 

Flight planning:

Before the flight, open Plan-G, and move the map to Los angeles.

Right click on KLAX---select "QDM range and bearing"

Zoom out, and move the mouse to Hawai.

I used the center of the group of Islands, PHOG, and found bearing 244.

 

Now do the same in reverse.

Click in the centre of Hawai, select QDM range and bearing, and move mouse to KLAX.

I found 050. The reverse of 050 is 230.

 

The course you need to fly will be between 244 and 230.

237 is a good estimate.

It may be slightly off, but no more then a degree, and you will find Hawai without issue.

 

The plan I made was for KLAX to PHOG. Flying a contant heading of 237 I ended up within 40 NM of PHOG.

 

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[sIGPIC][/sIGPIC]
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INS is an older system. The subs we had in the Pacific in WWII had it. I think the German subs did too. Problems with the older INS is they depended on spinning gyros, which drift. It's called Earth Rate Precession.

Since a gyro remains still in space once it's spun up to speed, and uncaged, and since the Earth moves through space in several directions, IE: It rotates about it's center, it orbits about the sun's center, it moves through the Universe, orbiting the Universe's central black hole, all at the same time. Thus, the gyro seems to drift. It's not really, it's environment does, but the effect is there.

INS systems need to be corrected every so often to compensate for ERP. The ones on planes have a magnetic sensor, and every so many minutes, seconds, whatever, the system compares the sensor's output to the gyro's, and corrects the system. I don't know just how subs do it, but it's probably similar. Plane's systems have to be told just what their latitude is, so they can apply the right correction. I wager newer systems use GPS to update the INS system once in a while.

Even "solid state", or laser ring gyros, have the drift problem. Same reason. Once they turned on, they sense the Earth's movements, as well as their platform's.

When a missile is launched, the system is corrected at the last second before launch. It won't drift signifigantly prior to impact. But even solid state gyros have the drift. It's inherent in the system. After all, even solid state gyros sense the various movements the Earth makes, in addition to their platform's movement.

 

I think all that is why the preferred method of navigation is GPS. No drift. INS is used as a backup, in case the GPS's electronics go wonky for some reason.

 

Sorry, I ramble...

Pat☺

 

Incorrect. INS did not appear in submarines until well after WWII. Subs in WWII relied on dead reckoning, aided by (in a rough sense) a hydro-acoustic map. Otherwise it was conventional ships navigation - US submarines in the Pacific in WWII spent as much as 90% of their time on the surface and their sub-surface range was never more than about 60 nautical miles, so little in the way of compound errors in that short distance. The ONLY enhancement of WWII was the advent of the widespread use of the gyro-compass, aided by radio navigation from long-range, shore-based stations - something the Germans made a lot of use of.

 

Post-war submarine technology led to longer underwater endurance, and the loss of the old visual navigation systems. First step was to enhance shooting of star, moon and sunshots via a periscope-mounted sextant, but the increasing accuracy and resolution of radar meant this was risky.

 

With the advent of the Nuclear submarine (and almost permanent submerged operation) and cruise (and later ballistic) missiles the need arose for an INS system and (token aviation reference) North American derived the N6A-1 system from the Navaho cruise missile for use by the USS Nautilus.

The Nautilus wasn't launched until January 1954. The SM64 Navaho project wasn't even instigated until 1946 and ran until 1958.

 

Again, misinformation does not assist this topic at all. And our OP does not wish to use an INS, so a pointless post requiring more pointless posting to debunk.

 

At this point I do think the topic has run its course. Celestial navigation aided by radio and in-flight calculation using bearings, maps and whatever other tools carried is the answer.

The solution was a good navigator. On long over-water trips run by flying boats for example, the navigator was often paid more than any other crew member, INCLUDING the captain, all of whom were highly trained.

 

Read https://en.wikipedia.org/wiki/Boeing_314_Clipper for details of the skills needed.

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Just for the challenge, I'd like to fly from LAX to Hawaii (or maybe even a smaller island like Fiji) without using GPS.

 

Is dead reckoning the only practical way to do it within FSX? It seems like any course error could cause a miss and I'm not sure island based VOR's have the range to give you any location info until your relatively close.

 

How do you do it?

 

Check out this thread. I think it’s possible, and even with ded reconing, you can still get close enough. https://www.avsim.com/forums/topic/406483-celestial-navigation/

 

I thought no it’d be pretty awesome!

 

Ive recently used celestial navigation at sea and the fixes were generally within about 10nm. Close enough to catch a recognizable landmark from the air.

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As long as you can keep a heading of 237 you'll get there. Doesn't matter what plane.

 

NO! It doesn't work that way. The Skyvector great circle ("straight line")route shows an overall heading change of 18 degrees in 2,200 miles, from 249 to 231.

 

I flew a Lockheed Constellation around the world (see: https://www.flightsim.com/vbfs/content.php?17742-Around-the-World-in-Style) using a drift sight (and dead reckoning when I couldn't see the surface) over water and got within beacon range of my target every time.

[sIGPIC][/sIGPIC]
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The great-circle is not a straight line.

It is the shortest distance, over a earth the is flatter at the poles. But not a straight line.

237 is a straight line. And takes you straight to it.

 

Stop just saying what you are used to saying for years and actually think about it.

Or just try it out. You just may learn something new.

[sIGPIC][/sIGPIC]
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The great-circle is not a straight line.

It is the shortest distance, over a earth the is flatter at the poles. But not a straight line.

237 is a straight line. And takes you straight to it.

 

Stop just saying what you are used to saying for years and actually think about it.

Or just try it out. You just may learn something new.

 

Not with ANY element of a crosswind. Trying it out will learn anyone nothing.

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Okay, just for fun. Started at KLAX, turned off all winds, flew a constant heading of 238 degrees magnetic. This was derived from the loxodromic true heading of 249 degrees (google rhumline calculator), corrected for 11 degrees for the average magnetic declination between LAX (11.5 degrees) and Honololu (9.5 degrees). Set up a direct-to PHOG (Honolulu) on the GPS as a cross-reference. I flew it on 16x normal speed, so taking about an hour in real time in the Aerosoft Twin Otter (with magic fuel tanks!)

 

The autopilot steered a constant heading and the aircraft wandered first left of the GPS planned track, then right. Unfortunately FSX crashed about 150 miles out. But it looks pretty close to me...

 

xlax.jpg

MarkH

 

C0TtlQd.jpg

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