Published in August 2016 issue
In the beginning, there was only the light, the sunlight that beamed softly on the clouds below.
By John Marshall
There was a reluctance to descend into the white darkness beneath, into the undercast that hovered somewhere above the earth down below. The instruments of the day were, by today’s standards, an oxcart in the time of thoroughbreds. Consider the instrument approach in the days of the flying boats—the magnificent ocean-spanning airplanes of that gentle era of refined travel before the Second World War changed everything. The successful accomplishment of an instrument approach aboard one of those airplanes was a marvel of coordination and mastery of a primitive piece of radio equipment. It took the efforts of three men—by turns the Radio Operator, the Navigator, and finally the Captain—to bring it all together.
Picture, if you will, the flight deck of a giant flying boat, most likely a Boeing 314 Clipper, approaching its destination after an ocean crossing that had consumed many hours and several stops. Now, at the end, the Marine Terminal at New York’s LaGuardia Airport lies under a lowering cover of cloud. The only way in is via an instrument approach. It will be a Radio Compass Approach, utilizing the bearing off a low frequency station at Bridgeport, Connecticut, some 20 miles away. The essential crew is all topside, in the spacious flight deck overlooking the great bow of the Boeing. Overhead, the muffled roar of the four Wright Double Cyclone engines pulls the ship along. It is a big round engine sound that soothes and comforts. Soon, the fun will begin.
On the instruments of the day—a vacuumdriven gyro horizon and a directional gyro— the Captain begins letting down into the murk. The beacon at Bridgeport comes in loud and clear, and the needle on the radio compass card points faithfully. The card does not rotate like the RMIs (Radio Magnetic Indicators) of today; the big N for North is always at the top. This is a relatively simple procedure, but it involves the intricate cooperation and coordination of the crew. The radio operator reads the constantly changing bearing from the station, and passes the information forward to the Navigator. He, in turn, translates the data to the Captain, the final link in this delicate chain, in the form of a compass heading to fly. If the airspeeds were any greater than 90kt or so, the exercise would have been impossible. But they weren’t, so it wasn’t. Slowly, ponderously, the huge airplane flies the procedure and finally bursts from the bottom of the cloud, with LaGuardia and its harbor hopefully filling the windscreen dead ahead.
Soon after came the Low Frequency Radio Range, a station that utilized the same low frequency band as the Radio Compass stations, but with some new and unique features. The station broadcast two Morse code identifiers, an A, or dit-dah, and an N, just the opposite at dah-dit. Each letter was aired into a 90° arc, and at the four points where they merged, the result was a solid tone; they were called ‘legs’, each roughly 90° apart. Once you were on a leg and had properly identified which of the four you were on, you knew with some certainty where you were. The trick was precisely identifying which leg was making the loud hum in the headset, and there was a long and tortuous procedure to do just that. In an airplane moving at something less than 150mph (knots came later), flying the entire range orientation procedure could take the better part of half an hour.
With frequencies hovering around the low edge of the kHz band, the signals were always susceptible to electrical interference; if there was a thunderstorm anywhere in the same state, it would crackle and pop in the headset, and just make life generally miserable.
I had to shoot a low-frequency range approach for real only once, and it was memorable. It was during the winter, flying an ancient bomber into an airport located in the great plains of west Texas, and it was snowing. It was a busted forecast of the first order; we had planned for nothing this serious, and fuel was a major consideration. The minimums for a range approach were 500 and 1 and, as we approached, I was in anxious contact with the weather facility at the field. The current report was one-half mile visibility and an indefinite ceiling.
By rights, we had no business even beginning the approach, but the situation was dire, and I told the weather chap as much. He volunteered to take another observation while we waited anxiously, droning into the white silence. In a moment, he returned and passed up the news. The field was now officially reporting 500 and 1. It was a miracle that I intended to repay with a nice bottle of Scotch for the weatherman after we had landed, provided we had landed. The range frequency was tuned in, and I squinted in concentration trying to pick out the signal from the snow static, all the while flying the airplane. We crossed over the station and the Cone of Silence, directly overhead now, and went out for the procedure turn. The volume turned up to keep the signal, my head pounded between the cups of the old headset. Once again over the station, and let down now to the minimum altitude, me mentally thanking God for the flat plains of west Texas. I knew that the highest obstacle in 50 miles was a grain elevator that I didn’t have to worry about. Below everything was white, white until, suddenly, ahead was the black smudge of the runway and, with full flaps, props full forward, bleed off the speed, and crunch! we were down. How we managed in those days was really miraculous.
After the war, the newfangled Instrument Landing System, or ILS, came into common use, a wonder of technology that I wished we had installed in the bomber that snowy day in Texas. The ILS was a marvel of modern precision. The course deviation indicator pivoted from the top of the instrument case, blue on one side and yellow on the other. Glideslope needles mysteriously appeared from beneath some tantalizing mask, and if you were fortunate enough to keep everything crossed, lo and behold, at the daring and courageous height of 200ft above the planet, with God’s grace, you broke out of whatever you were flying in, saw the runway ahead, and landed. It took great skill and precision to make the tiny corrections necessary to keep those devilish needles crossed; the fact that airspeeds (and, more importantly, ground speeds,) were a fraction of those turned in by today’s jets made the task somewhat easier.
The next innovation was the Zero Reader, a sort of repeater of the ILS raw signal that was supposed to amplify the data and present it in a form that supposedly made it easier to fly than the swinging yellow and blue. My first experience with the zero reader was on the DC-6B and, being only the Flight Engineer, I got virtually no hands-on experience with the device. I do remember that it was mounted square in the middle of the instrument panel so as to maximize the parallax.
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In the middle ’60s, we saw the introduction of the flight director as we know it today. It was a quantum leap in technology that enabled the Pilot to track not only an ILS signal with previously unheard-of precision, but also to fly and track a VOR (Visual Omni-Range) course, and even a selected heading in the absence of a radio signal. Our new Boeing 727s, that had replaced the venerable DC-6s in the corridors over Germany, presented us with a unique challenge. We had a new toy, one that took a bit of getting used to. The flick of a switch on the glare shield panel popped the two slim yellow needles out from behind the mask and into view on the ADI, or Attitude Deviation Indicator (we would also be learning an entirely new language as we dealt with instrument flight). One was horizontal, the other vertical. Selected to the heading of the airplane, it would lead you anywhere but, hopefully, to the extended centerline of the runway ahead, as personified by the localizer of the ILS.
Our Captains in Berlin, probably the most proficient instrument Pilots in the industry, exulted in the new toy. One favorite of mine, a gentle giant of a man, ponderous when shackled to the earth but a magician aloft, with the controls of a 727 in his massive paws, took great delight in playing with the new flight director. On days in which the weather didn’t matter, he would place a pillow on top of the glare shield, totally obliterating the view ahead, and head down in full concentration, fly the ILS with the flight director down to touchdown. He would brief his co-Pilots in gentle tones, “Now don’t let me hit anything except the runway.” It was always a moot statement. He was such a superb instrument Pilot that there was no question that he was going to split the centerline.
Soon came Category Two, or Cat II, as it was called. Now the electronic requirements became a bit more sophisticated. Not only did the rules call for specific autopilot and flight director configurations, but the equipment on the ground had to pass muster, too. Runway lights, touchdown zone lights, centerline lights—all played a role. A new term, Runway Visual Range, entered the lexicon. No longer did a weather observer poke his head out the window and estimate the visibility; now it was all done electronically by new-fangled devices called ‘transmissometers’. These couldn’t lie or fudge, and hard and fast values were required before one could shoot an approach. There was more than one autopilot, sometimes even three, each of them talking to the others, comparing notes. Everything had to agree to continue, and now we were going to 100ft above touchdown, then 50, and eventually to virtually nothing.
What had been a hard and fast altitude limit, below which you dared not venture without the runway firmly in sight, now became merely an advisory, or an ‘alert height’. The Pilots were passengers, systems monitors, and managers. Auto-land systems became so reliable that all the Pilots had to do after landing was to put the engines in reverse and remember to disconnect the autopilot so they could taxi to the gate.
This could be an interesting exercise at times. One foggy morning, at Paris Orly, we shot the Runway 26 ILS down to absolute minimums; surrounded by an envelope of milky white, my muscles were actually tensed to push up the throttles and go around when the First Officer yelled, “Runway lights! Dead ahead!” Sure enough, there they were, straight as an arrow, the touchdown zone glowing in the murk. In a few seconds, we were safely down and groping through the fog for a taxiway sign. In the space of a few hundred feet, everything had closed around us again; I could barely see the concrete beneath the nose of the aircraft. This was in the days before airport surface radar was commonplace, so we were virtually on our own. Orly Airport was confusing enough in broad daylight; now, it was impossible. We finally found the gate, but it took the better part of half an hour. My biggest fear was coming nose-to-nose with another airplane on the taxiway.
And so it went. In how little time technology has taken us from peering anxiously into ferocious weather, with our hands full of airplane, willing the cloud to part and reveal precious mother earth below, hopefully with a concrete expanse spread before us, beckoning, welcoming. Now we are systems managers, sitting calmly, with only the butterflies still doing rolls in our stomachs while managing the hundred-ton craft down the ethereal electronic path, doing it by the numbers, one, two, three. If they don’t add up, we bail. Instantly. All the components compare, connect, disconnect, display their relative health with little green enunciations, like the EKG trace in a hospital room.
All we have to remember is to put the engines in reverse after the electronic work is done, and dismiss the autopilot in order to turn off the runway: “Thank you, Mr. Autopilot, for saving my life and those of the hundreds of fortunates sitting behind me. Now back into your electronic cage until next time.”
Effective and safe? No question. More fun, more satisfying? Not by a long shot.