View Full Version : How did they cross the ocean?

June 26th, 2009, 04:16
I'm wondering how the navigation across the ocean would be done in 1949?

I'm interrested in arriving on destination accurately for two legs in particular: Lisbon - Tenerife, Dakar - Recife

Several parts to my question:
- How did they calculate wind drift correction without a fixed refernce on the ground on which to orient?
Is a drift meter like that directly indicates wind drift (like Driftmeter gauge by Glen Copeland - twidgau.zip) realistic to use? Did anything like that exist in 1949?
Or did they only have driftmeters that need a fixed ground reference like the one by Dave Blitzer - drift7.zip?

- How to adjust course to follow the great circle route?
I believe to have read somewhere that for crossing the atlantic from Dakar to Brazil the changes in magnetic deviation almost exactly compensate for the necessary changes in course. And in fact on an accelerated test flight with constant heading (no wind) I arrived pretty close to Recife.
But what is the generic procedure to adjust course? (for the Lisbon - Tenerife leg for example)

- Would be happy for any further insight on how the atlantic crossings were done in those days...



June 26th, 2009, 08:10
Wooo.. this could be the beginning of a long, involved discussion :icon_lol:

First, the real-world aviators had things we don't have: proper navigation charts, reports from ships on wind and sea conditions, long range communications (via Morse), in later years ( the 1940's and beyond) Ocean Ships with weather observers and onboard NDB's at fixed locations and most of all, a navigator to handle the chores including celestial navigation. On a ten hour flight the Nav. worked constantly to update position -including use of a drift meter ( the real-world ocean has waves that often clearly show wind direction not available in Flight Sim) and a sextant. Pre-flight planning often took an hour or more for each leg and was drawn on those big charts the same as used on board ships.

In addition, the expectation was different. We get used to the GPS crutch which gets us to a point within a mile or so. Then it was expected to arrive at/near a reference point and then adjust course as better data became available - radio aids, surface landmarks, etc.

During WWII other aids came along - GEE, LORAN, DECCA that further reduced error or provided more info.

So a lot of our problem is that the sim just isn't built for representing navigation in 1949.

here are some basic references:

Most of this isn't really 'ancient' history.... the first production installation of Inertial Navigation Systems in a commercial aircraft wasn't until the B-747; early Sat-Nav systems didn't get used until the late 1980's- military installations were, of course earlier but the U.S. Air Force and U.S. Navy continued instructing military aviators on Celestial Nav until 1997.

June 26th, 2009, 09:47
Another thing we don’t have that real flight crews had, even in the early 1940s, was the ability to “ADF” radio stations at very long ranges. Not just ADF stations, but civil broadcast stations. I read that when there was to be a flight of B-17s from the West Coast to Hawaii (about 2200 miles) the radio stations at Honolulu would stay on all night to allow the Fortresses to DF on them from quite a ways out. It would be cool to have this sort of ability in FS.

Highmike came up with a rather clever and simple procedure for great circle navigation:

Say I'm flying from Easter Island to Santiago, the flight planner tells me I should head in a 095 direction for 458 minutes! When I enter the reverse course it tells me I should head in a 267 direction, so there's an 8 degree difference between my departure heading and the compass point opposite my heading for the reverse course, namely 95 - 87 = 8. I may leave Easter Island heading 095, but I should arrive at Santiago heading 087, and I should adjust my heading one degree every 458 / 8 = 57 minutes.
This does not compensate for magnetic variation, however. I plan to test this method on my two long legs coming up soon…

June 26th, 2009, 12:03
Well I'm not going to give you any instructions on doing it myself truth is I am likely to get lost my self.

I will however offer this

Its a map of intercontinetal routes based on routes from the 1930s

If they could do it in 1930 you can do it in 1949 :applause:


Source: adapted from B. Graham (1995) Geography of Air Transport, Chichester: Wiley.

There is some other text I did not want to copy you know copywrite laws but you can read it here

:guinness: (http://people.hofstra.edu/geotrans/eng/ch3en/conc3en/earlyairnetworks.html) <------ Click

Best of luck and Well keep the search and rescue crews on stand by. :icon_lol:


Funny now that I embeded the image here and posted the link the page seems to be down.

Anyway there should be a picture there that I did not want to post here for possible copy write violations. Maybe later it will be up.

June 26th, 2009, 14:01
Or you could do like I do. Use the wind drift gauge and pray a lot. ;)

June 27th, 2009, 05:54
It’s interesting to look at how FSX calculates the courses compared to Super Flight Planner. In preparing for the first long leg, NTGJ – SCIP, I plotted the track in both SFP and FSX and the result is shown below.

I’m wondering what accounts for this difference. Over 1,400 miles, two degrees could mean the difference between landing at SCIP or going whereever Amelia Earhart went… On the other hand, both could be correct, but one (SFP) just describes a "straighter" line (on a mercator projection.) But if that were the case, then the calculated distances would be different as well, but they’re not. They both come out to 1402.3 NM exactly. I think I’ll go with FSX’s plot, since that’s the universe I’ll actually be flying in!

July 1st, 2009, 01:14
Wow, the immersion factor for the 1949 event just went up a notch! :applause:

sr, Paul, Willy, Dave,
thanks for the very interesting insights.

Wooo.. this could be the beginning of a long, involved discussion.
Then keep it coming... This is very interresting stuff in the links you sent! Amazing what info can be found on Wiki.

My two practical questions have been clearly answered
-I'll have no more second thoughts about using Glen Copela's Driftmeter gauge. If they had all that additional help, I can use that gauge. 1949 navigation is for wussies - they should try if they can do it in Flight simulator...
- Highmike's great circle method - excellent!

Thanks again.

July 1st, 2009, 03:20
In the early 70s we used full-time navigators, with sextants and drift meters for flights out of Guam to Japan, the Philippines, Hawaii, etc.

The aircraft we flew did not have INS systems. Only the largest had LORAN which was the best electronic method for tracking position on long over water flights.

My cousin flew El Toro to Chu Lai in the back seat of an F-4 Phantom in 1967. For the leg Midway to Wake, the pathfinder KC-135 was cancelled, so the flight of 8 Phantoms was on their own.

He still has the shakes and sweat beading up on his forehead as he describes getting down to 10% fuel - none of the eight able to pick up the Wake TACAN - four navigators saying the flight had flown past Wake and was south, two saying they were east and two including Josh saying they were west.

Turned out Josh was right, they had to back track and landed with 4% fuel.

We had an A-3 Skywarrior take off from Guam in Sept 1973 and got lost on the way to the Philippines. They lost the electronic compass, the wet compass came off the card. The sextant did not have a bubble, they had the wrong year Air Almanac. They departed Guam at 1000 local and were due at Subic about 1300 local. The sun was not in a position to be a reference until they were well overdue.

The USAF HF-DF net in the Pacific had loaded new software the night before and kept putting the aircraft position as over the Philippines. The pilot's comment was that he was at 32,000 feet in completely clear skies and could not see any !%%@# land.

Only in the last hour before fuel starvation was the aircraft position located as 800 miles north of their course and too far from land to make it.

Luckly they bailed out over the only ship in the Japanese Maritime Self Defense Force with an embarked helicopter.

But it came very close to an airplane flying off and disappearing with the entire crew. Too close.

July 1st, 2009, 04:16
Not really usable info for this trek, but very interesting to see how the Poynesians got around in the Pacific Ocean hundreds of years ago in boats made out of trees with no instruments at all.

Have a look around this site if you have time, pretty incredible.

"Ignorace is bliss and genius is pain" ....they must have had a little of both not to mention gonads and a lot of confidence.

That usually gets folks in trouble...LOL



July 1st, 2009, 07:33
1949 navigation is for wussies - they should try if they can do it in Flight simulator... ;) ;) ;) Forgot those smileys - I really should have edited and put it. :kilroy: I forget that we have outstanding people here who have done that stuff... Thanks Reggie for sharing.

Actually, Austin, tackling these navigation issues really gets one thinking.
These early navigators - the first galley leaving the shore in the mediterranean, irish monks and viking to Iceland, and polynesians, the first caravels across the atlantic, first long range pilots, ect, really had some balls...

Meanwhile I have done some more reading, and really am getting interested in doing the cross atlantic flight with onboard means - Sextant navigation does sound interresting and not too difficult. David Blitzer's article is like made for me
I'll have 2 weeks of vacation coming up away from the computer to read up on that. :naturesm: Let's see.

July 19th, 2009, 08:10
Well, here’s how these guys did it…

I’m reading a book called North Atlantic Cat, by Don McVicar (thanks for the recommendation, Rob!) McVicar was a civilian pilot attached to RAF Ferry Command in WW-II, and got to fly many different types of planes, making for some great “sea stories.”

So he’s taking an RAF Coastal Command PBY from Bermuda to Greenlock, UK, some 2800 miles. Estimated flight time: 25 hours! They would need at least a 10-knot tail wind component, or they wouldn’t have enough gas to make it, and so they had to wait for a favorable weather forecast.

They took off at 37,000 pounds; 7,000 pounds over max take off weight (I wonder if they got a penalty for that!)

They divided the flight into 500-mile segments, calculating the course to steer for each one, based on Great Circle nav headings, and magnetic variation changes, but they had charts for that. When the sun was out, during the first half of the first day, they took sun shots with the sextant. They calculated their true airspeed using a Dalton flight computer. They estimated drift by peering through a drift meter gauge at the ocean below, but if the sea was too smooth, this would not work. At one point, as they passed through a strong storm front at night, with ice building up everywhere, one crewman dropped flares into the sea while the captain watched them through the drift meter. This resulted in an estimated 25-degree drift, more than the Dalton flight computer could handle, so they calculated course to steer using pencil and paper!

They constantly checked fuel consumption against estimated time to empty, and for half of the flight they were calculated to run out of gas before they reached the UK, while they chased after that tail wind.

They made it!

July 19th, 2009, 10:04
yep. We dont know how good we have it. In 1991 I installed an early Apollo GPS/loran C in a T-28, the first ones I'd seen.We were blown away, and it still required you to interpet and plot on a map, if you wanted to 'see' where you were. It's amazing how fast LORAN fell into disuse, and that was the end all at that point. We actually had a sextant and drift in store in the late '90's, and the astro window and mount in some of our DC-6's. Tried out navigating the old way on a couple of cross country hauls. Even with ADF fixes, I was lost lost lost.I break out in a cold sweat at the idea of a pond hop with traditional navigation. It really is an art as well as a science. Thank Garmin for GPS! Though I allways run a plot on a map as backup, and as I am a firm believer in the demon Murphy(and have excurciatingly poor luck!), my hand held is allways on and every waypoint and divert field loaded.

addendum, Teson1 comments. I ran across an article on line about the Polynesian navigators. Apparently, the old methods are preserved and past on with official support. The artical was on a new sailingmaster being awarded his shingle after a years long apprenticeship under the Kahuna of Polynesian navigators. Very cool. I'll look for the artical and post a link if I can find it.

July 22nd, 2009, 04:21
At one time I was really in love with sailing, wet water boats.

I've read a lot of books by folks like Joshua Slocum, Miles and Beryl Smeeton, Eric and Susan Hiscock - people who helped define long range, around the world sailing in small boats.

Early navigators had big brass hairy ones, be they in the air or on a small boat.

Today, I can use a GPS to navigate within a 5M accuracy on a lake which is barely two miles across.

Back in 1979-82 when I lived on Antigua, I used to meet a lot of folks who sailed across the Atlantic, invited many to our home for a dryland meal and their first real shower, chance to do laundry after the voyage.

I often wonder what the stories are like today, because an amazing number of them landed on the wrong island. They were aiming for Barbados, Martinique, St Martin and Antigua was the first place they arrived.

Also always made me wonder how many each year went too far north and never hit land before their supplies and water ran out.