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Yesterday, a day to remember, took us to Mexico City. At one time it was the largest city on the Earth, and it still may be so... 30,000,000 plus folks living in a valley between two 12,000 foot peaks. The airport elevation is 7,600 feet above sea level; only a few hundred feet beneath the maximum take-off and landing altitude for most airliners. As we descended, very carefully, into the Mexico City area, I was struck, once again, about how massive this place really is; think about it... 30,000,000 + people living here, most in poverty. The initial approach fix is crossed at 12,000 feet above sea level at a right angle to the runway! Unreal, and that's putting it mildly. The air pollution is so bad, that you can actually taste it, smell it, and feel it on your skin. The landing visibility usually hangs around four miles, on a clear day. Crossing the runway threshold at 7,800 feet yields a higher groundspeed than, say, landing at Seattle. The air is thinner here, so the aircraft has to move faster to capture the same airspeed requirements. Hence, the runway is a 12,000 foot long piece of rough concrete. The engines and brakes work harder than normal to get the weight slowed to taxi speed. Taxiing to the gate, we were watched by hundreds of people that live on the perimeter of the airport in cardboard (literally) shanty towns, complete with laundry flapping in the yellow breeze.

The employees at the Mexico City station do an outstanding job of turning our aircraft around for the northbound flight. They truly love their jobs, as they are coveted. Hating management is not an option down here. The weight and balance is done long hand with a hand calculator. The numerical entries, via pencil, are always clear, concise and correct. Quite impressive. Fifty minutes later we were punching through the pollution layer into clean sky. Before take-off, I sucked 100% oxygen to clear any potential pollution caused stupid molecules running around in my feeble brain.

A few hours later, Redondo Beach sand was between my toes as we overnighted in LAX.

That was yesterday... Today, it's 25 degrees Fahrenheit in Anchorage with sunny skies. No pollution here, that you can see or smell, anyway. Riding in the crew van enroute to the hotel, a cow moose was blocking our path, until she slowly ambled into the trees.

We crossed the jet stream in the vicinity of Sandspit (YZP) at 32,000 feet. The wind velocity peaked at 203 m.p.h., 70 degrees left of our nose. Maintaining course required upwards of 25 degrees correction into the wind. The wind tunnel was about 30 miles in diameter and no turbulence was associated with it. Truly amazing... Imagine the nights before inertial navigation or global positioning magic; then throw in an undercast. Navigators had their hands full dealing with winds like these.

Finally, after six hours, we descended into Anchorage airspace, turned final approach over Fire Island and made a passable landing, mine. I would rate it about 80% on a scale of 1-100.

Day three of a four day...The adventure continues.

Andruha
3/18/2013 05:45:13

Some story of inertial navigation history

http://www.virtualpilots.fi/hist/WW2History-JarlArnkilEnglish.html#tupolevit

Inertial navigation
Then I could tell something about inertia. In the summer of 1966 there was an important America-conference of western airlines in Otaniemi. This time Leiviskä was one of the organizers. A guy called Mr. Partrich was representing his factory in the conference and called the flight department asking if we could negotiate. Our chief pilot said: "Kille, why don't you go to both." Partrich told that Sperry was building an inertial navigator, which would fit into an airplane. Inertial navigators had previously been built for US Navy, for submarines navigating under the polar ice cap. That device was awfully big. Now the factory had smaller devices, which would fit to an airplane. Puhakka and I went to Sperry factory to see these devices. They wouldn't show us much, but they told us that two of them would fit to a DC-8. We agreed that we would put in a reservation, but we would wait for FAA approval of reliability and accuracy. We would buy the inertia if it was approved.

Pan Am had made a conditional reservation too, and we thought that we could also jump on board but we would not pay anything yet. We negotiated with the chief of Pan Am's navigational department and he told us about the pros and cons of the device. In the end the factory notified us that they had not got the FAA approval and that Pan Am had withdrawn their order. They asked if we would like to retract our order too. I felt that it was an honest move from the factory and we told them that we would pull out too. It was quite a contraption too, if you could only fit two of them to a plane.

Then I called Reynolds, the chief of Pan Am's navigational department, again and asked for other vendors. There was a firm called AC Spark Plugs in Santa Monica. The name later changed to AC electronics. They had also started designing an inertial navigator named Carousel, because the gyroscopes and acceleration sensors were rotating at a certain speed. The gyroscopes and acceleration sensors were fitted on a rotating disc. World co-ordinate system was stored in a computer. We examined the thing and they told us about the flight test results and so on. Then we heard from somewhere that there was also another company, Litton, making inertial navigators. It was right beside the first factory we visited. Jussi and I visited that place a couple of times too, but we were a bit late. They were talking more about AC's Carousel than Litton's navigator - all bad of course. Typical American sales pitch, bad-mouthing the competitor's product in every turn. Litton's system also seemed inferior to AC's and that's what I told Finland. We should buy AC's product.

Well, we could buy them if we had the money. They cost $100.000 a piece. Jussi and I sent a lot of memos and calculations to head office, to Korhonen who was the CEO at that time. Of course we talked only about AC, that we should buy their inertial navigator. Praising the inertial navigator finally took us to a point where Korhonen called us to head office. Korhonen was sitting on the other side of the table with our technical director, Stude, and the head of flight operations, Puhakka. I was sitting on the other side with Leiviskä. We discussed the matter and kept praising the inertial navigator.

Well, then we talked about other matters and Korhonen lit a little cigar, took a couple of breaths and said that we would take Loran C. I could not hold my mouth shut and told him: "That's too bad, because it will be a big mistake. The future is in inertial navigation." Korhonen took the cigar in his hand, looked me straight in the eye and asked if that was really true. I said I was positive. After that Korhonen said that we would buy the inertial navigator.

We had to fly one hundred flights across the Atlantic ocean with navigator on board. After that we got the official approval that this device alone would be sufficient for crossing the Atlantic. The only time we had to deviate from the direction inertia gave us was when we flew from west to east. The navigator said that I should turn right 10 degrees, because we were heading to the wrong approach corridor. I turned 10 degrees and after that the radar controller asked why we had turned, because the previous heading had been right. The human navigator wasn't exactly accurate but the inertial navigator was just right. The inertial navigator worked according to a principle that when it knew the true speed, it used the acceleration sensor data calculate the ground speed. It also measured the drift angle and we got the wind direction, speed and the time to next waypoint, which could be located anywhere in the world. You could enter the starting point and nine waypoints. It stored the waypoints in numerical order with fine, precise manner and if you did not enter additional waypoints it turned back to point one, turned 180 deg

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