Flash in the Sky

Sausalito is north of San Francisco.  On a clear evening in early 1953, a small group gathered for cocktails at a publisher's home, which commanded a sweeping view of the Bay.  In awhile, the party would convoy across the Golden Gate Bridge and convene at the Mark Hopkins to help Heinz Haber (1913-1990) celebrate the publication of his book, Man in Space.  For Dr. Haber, the night would produce, not untypically, a new idea.

Heinz Haber, a slender man of forty with graying blond hair and cyan eyes, held a post as a research physicist at UCLA's Institute of Transportation and Traffic Engineering (ITTE).  Space exploration lay entirely in the future.  Haber's visionary work on space flight did not go unnoticed.  His distinguished German accent -- and Walt Disney -- made him a children's celebrity on television.

Amid the chatter and clinking glasses, Dr. Haber took idle notice of the lights atop the Oakland Bay Bridge in the distance.  He could see four of them.  To most people, the lights would appear simply to flash without order.  Haber saw a repeating sequence: 2-1-4-3-pause, 2-1-4-3-pause.

The pattern continued and so did the arrival of guests.  Later, while the other celebrants were donning coats in preparation for departure, Haber checked the lights again: 2-1-4-3-pause, the same pattern as seen an hour ago.

"Hmm," Heinz Haber must have mused to himself.  Those lights are not flashing; they are rotating beacons.  They are driven, most likely, by induction motors, which, while not exactly synchronous, are nevertheless loaded equally, which explains their constancy.  He put on his coat.

As guest of honor, Heinz Haber, yielded to the demands of surrounding conversations and forewent his meditations upon beacons -- but only until the party was ensconced at the "Top of the Mark."  For, there, through the window, Dr. Haber once again observed the lights of the Oakland Bay Bridge.  But the pattern was different!

The new sequence was 2-4-1-3-pause.  Lights 1 and 4 had curiously become interchanged.  Haber sketched on a napkin.

 "Aha!" he must have thought.  In their rotations, the two light beams from the opposite ends of the bridge must pass across each other somewhere out in the middle of the Bay.  The viewing point in Sausalito was many miles farther from the bridge -- no doubt beyond the intersection of the light beams.  From there, one would see the order 4-1.  Here in downtown San Francisco, we must be inside the point where the light beams meet, which causes an apparent reversal in the order of the flashes to 1-4.

And what of the middle two light beams, 2 and 3?  They merely diverge, Haber speculated, thereby presenting the same sequence to both vantage points.

There is information, he concluded, in the sequence of light flashes.  Information possibly useful in reckoning an observer's position.  Here was a solution in need of a problem. Heinz Haber did not have long to wait for the latter to appear.

Dan Gerlough, the canonical engineer, replete with pocket protector and sliderule dangling from his belt, introduced me to Heinz Haber in the latter's office at UCLA. Gerlough was recruiting me for a position in the ITTE laboratory.  Dr. Haber turned at once to his blackboard.

 "Zis is ze glide slope, yah?" intoned Dr. Haber, pointing at a slanting chalk line.  He was wearing a tweed jacket with elbow patches and a narrow, nondescript tie tucked into his trousers.  "Ve haff zis aircraft descending, you see.  Guided by radio beam toward ze touch-down zone."

Haber sketched a cloud layer and an airplane emerging below it.  He explained that a critical moment occurs, in which the pilot must transition from reliance on electronically deflected needles inside the cockpit to visual reference outside. The pilot is compelled to make out objects on the ground -- in particular the runway -- and to determine instantly that a safe landing can be achieved.  Otherwise the approach must be aborted without hesitation.

"Ve come now to my proposal," Haber continued.  "Four beacons, like so -- rotating in ze vertical plane. All light beams intersecting on ze glide slope, yah?"

The sketch now had four additional slanting lines. Each was drawn upward from separate points at intervals on the ground in front of the runway.  They all met at a point.  Haber superimposed a representation of the pilot's eye looking toward the runway.

"From zis place, all four beams appear to flash in unison -- at ze same time, yah?"  Haber turned toward Dan and me, pausing for dramatic effect.  "But above or below, not so!"

An audible gasp accompanied my sudden comprehension.  Haber clicked his heels and nodded smartly. He described the lightbeams as appearing to flash in a rapid forward sequence, 1-2-3-4, whenever the plane was too low and in reverse order, 4-3-2-1, if the plane were above the glide slope.

" 'Fly up, fly up,' ze light beams say," said Haber, gesturing at the diagram.  "Or else, 'fly down, fly down,' yah?"

Harry Matthewson, ITTE's founding director, had joined our small meeting unnoticed.  He shook my hand, then praised Haber for his great invention.

"A major contribution to aviation safety, Heinz," he exulted.  Matthewson clapped Dan Gerlough across his shoulders. "When are you going to assign someone to carry out the requisite experimental work?"

Gerlough and I exchanged grins.

There can be no doubt that joining the staff of ITTE in 1953 was the best decision in my career.  The next two years were filled with achievements for a dozen scientists and engineers. Much of their work strongly influenced transportation systems in the decades since.  Over those seminal years, filled with crashing cars and anthropomorphic dummies for testing seatbelts, with cable barriers and radar speedmeters, with computer programs and vehicle metering -- oh yes -- and classroom lectures and long commutes -- in between and amongst them all, I labored earnestly on Haber's beacon system.  It alone involved airplanes.

"Persistence of vision plays no part," Haber proclaimed.  I followed him across the parking lot on his way to a speaking engagement.  I had expressed doubt about the accuracy of the beacon system.  Haber shook his head.  "The light from each source strikes ze pilot's retina at a different place," he continued. "Ze appearance vill be as a brilliant streak moving toward ze aerodrome -- or avay."  He gestured with his hands and arms.  "A brilliant streak, yah?"

The door on Haber's Hillman protested with a squeak.  "Discrimination by flash sequence," said he, "makes use of 'ze minimum interval of human perception'."

"But," I said, "each beacon must be driven precisely..."

"Haff you never heard of a 'sel-syn'?" asked Haber.

"How do you spell it?"

It was a typical encounter, short but instructive.  By the time I saw Heinz Haber again, I had dug up the specifications for self-synchronizing motors.

"A sel-syn has position errors of several degrees," I told him.  "And that assumes a constant speed and torque."  I went on to explain that to make the beams track the glide-slope, we needed a variable-phase power source.  "The angular speed will be anything but constant."

Haber shook his head.  "Haff you never heard of a cam?" he asked with mock derision.  "It is spelled c-a-m."

Whatever soaring pride I felt in my other work at ITTE, these intermittent encounters with Heinz Haber restored my humility to ground level.  Another week and I caught Haber just before one of his classes.  I showed him my drawings for the cams that would move the beacons, then complained about the need for slip-rings.

"Slip-rings?" asked Haber.  "Vhy ve need slip-rings?"

"To supply power to the lamps, Dr. Haber," said I, momentarily astonished at my mentor's naivete. "Inside the rotating beacons, you see.  But slip-rings have a tendency to wear out -- "

"Haff you never heard of mirrors?"

I nodded and picked up my drawings.  The next design had stationary lamps, their beams reflected by rotating mirrors.

In a later installment, Haber asked me why I had assumed the mirrors to be flat.  Back to the drawing board, there to discover that individually shaped mirrors no longer required cams.  The sel-syn motors would operate at a constant speed after all, minimizing their angular errors.

"For experimentation," Dr. Haber told me in passing, "it is utmost importance to control all variables.  Ve need like a 'vind tunnel' for zis system."

All right, I thought to myself, it is time to start building something.  But what?  It would take months to design the optics and fixtures for a mockup.  Determined to make a contribution to the effort, I came up with the design for a simulator based on gas discharge tubes.  Simple.  No moving parts.

The technology was taken from the strobe lights I had used for spark timing in my previous job at the service station.  I waited with mild trepidation for Haber to return from a conference in the East.  He stood over my drawing board with head tilted back for a bifocal view.

"Flashing lights!" exclaimed Dr. Haber.

I nodded tentatively.  "That way we can control precisely the frequency, sequence, and phasing of -- "

My intercom buzzer interrupted.  It was for Haber.

"Yah, of course," he said into the phone.  Haber covered the mouthpiece and concluded our conversation.  "Ve must bring in students from ze school of psychology as subjects and actually measure 'minimum interval of human perception.'  From zat ve estimate aircraft positioning error."  Hah, my idea was accepted.

Dan Gerlough helped me round up the parts.  I visited the Engineering Library and boned up on the "stroboscope."  The first approach-light simulator was a "breadboard."  It used a row of six small neon bulbs mounted on a piece of plywood painted flat black.  Each was fired by an electronic pulse, which was delayed by a controllable offset from its neighbor.  I spent a week learning multivibrators, blocking oscillators, and one-shots.  The circuitry worked.  The redesigned simulator began taking shape, 10 feet long and festooned with xenon flash tubes.  In another week, it would be ready for power-up.

Dr. Haber dropped into the lab for a surprise visit.  I showed him the breadboard and the flashing neon lights.

"Too dim," said he, while twiddling with the control panel. "Haff you never heard of Edgerton?"

"The stroboscope Edgerton, you mean." It was all I could do to suppress a chuckle.

"You need xenon flash tubes here," he said.

I pointed across the lab.  "Perhaps like those?"

If Dr. Haber was pleased, he concealed it from me.

Dr. Haber spent his lunch-hours scarfing a sandwich over a chessboard with Al Berg, whom he routinely vanquished  "Hah-hah!" he would exclaim.  Once when Al was not available, I volunteered to be beaten and got lucky with a disclosed capture of his rook in the middle game.  Haber's face darkened, and about that moment I awkwardly kicked over the chessboard.  It was an accident, but Haber took it as a patronizing gesture.  Without hesitation, he set up the board again, placing all of the pieces from memory.  "Your moof," he said.  Thirty minutes later, the game ended in a draw.  "Hah-hah!" said Haber, offering me his hand.

By that time, I was well into my senior year, and the pressure to complete my own undergraduate thesis precluded my working on Haber's project for many days.

Still, aviation was never far from my mind. All of my commuting time was devoted to thinking about the approach-light problem.

One morning, I discovered the fatal flaw.

My commuting trips took me daily along Aviation Boulevard, bordering Los Angeles International Airport just under the approach path.  Often I would pull off on the shoulder and listen for descending thunder in the sky.  I would jump out of my car to stare up at the belly of a silvery apparition with oil-smeared engine nacelles, passing so close I could make out the tread lines in the wheels.  The pilot's final power reduction made the engines pop and crackle in relaxation.  The plane would settle majestically onto the runway beyond the fence, where jackrabbits graze unconcerned.

Puffs of bluish smoke, the faint chirp of the tires -- the routine conclusion of yet another flight from... wherever.

Back into the car with a sigh.  Can't be late for class.

My idea of a big date was to take a co-ed named Doris on a Sunday drive in my '49 Ford to the same spot.  Los Angeles International Airport in the early fifties was scarcely more than a paved strip with corrugated metal hangars along one side and a handful of stucco buildings on the other.  Mike Lyman's delicatessen was located in the center of the complex.  I might spring for lunch there.  From its second-floor observation deck, Doris and I could watch the DC-3's and -6's taxi to the terminal just below.

Rumpled executives and rich people would disembark and walk along, glancing self-consciously at the gawkers.  Sometimes you could catch a glimpse of the pilot and copilot strolling across the tarmac, chatting about important flying stuff, no doubt. Little did they know that there was one fellow up there, munching a pastrami sandwich, who was actually working with Heinz Haber on the approach-light system of the future.

On a particular dark morning in November, 1954, low clouds covered the sky above Aviation Boulevard.  Visibility underneath was murky, a condition not uncommon in Southern California.  I stood beside my car, jacket buttoned against the damp chill, ear cocked toward the east.

The unmistakable throbbing of four engines reached my ears, probably a DC-6 approaching.  I tried to visualize a row of Haber's beacons spaced out along that vacant field with their synchronized mirrors whipping beams of light up into the sky.  The pilot would be watching for the tell-tale flashes: "fly-up" or "fly-down" --

Suddenly I remembered Haber's words:  "Ze appearance vill be as a brilliant streak toward ze aerodrome -- or avay, yah?"  What, I wondered to myself, would be the appearance of the light beams as they strike clouds?

Searchlights do exactly that.  You have seen how a bright spot forms and moves about the sky.  With your mind off guard, you might perceive the source of light as a phantasmic bulb racing around inside the cloud.  In such are UFOs likely reported.

While descending above or just inside the overcast, a pilot, with his eyes prying into the darkness ahead, would doubtless see this diffused brightness as a "brilliant streak" whipping along at the tip of the searchlight's beam.

For the case at hand, with Haber's approach-light system, there would be not one but a number of luminous blobs chasing each other along a line beneath the plane.  This would be so -- even if the plane were precisely on the glide slope!

Looking up, searching the sky that morning, I had a flash, so to speak, of insight.  No experiments in my laboratory were necessary.  I was certain that the sweeping beams would swamp the pilot's eyes with contradictory information -- at the worst possible moment.

Just then, I caught sight of the airliner's landing light.  DC-6, all right.  The plane was off course to the north -- wide to the right.  The pilot was already correcting, for I could see the landing light sweep through an arc, flashing into my eyes.  Still turning when it reached Aviation Boulevard, the giant airliner corrected abruptly to line up with the runway. Touchdown was otherwise uneventful.

How would Dr. Haber take the news? I wondered.

He smiled.

At first, I was not sure my explanation was clear.  I repeated the part about the searchlight shining on a cloud.  Heinz Haber sighed.  He leaned back in the chair behind his cluttered desk and told me the story of seeing the beacons across the Bay from Sausalito.  We both sat for a time.

Such an inventive leap, Dr. Haber must have thought.  Its usefulness, alas, so rudely dispelled by his young research associate.

Suddenly Heinz Haber sat up straight.  "Vhat is the problem?" he asked.

By then I should have known to be suspicious of any apparent lack of understanding on the part of Heinz Haber.

"The sweeping light beams," I said, "will cause confusion for the pilot, because -- "

"Never mind zat.  Haff you already forgotten ze problem?"

"Dr. Haber, I -- "

"Ze problem has not gone avay!"

I thought for a long moment.  "Oh!" I exclaimed.  "The original problem, you mean."

"Vhich is?"

"Transition from flying by instruments to, uh, ..."

Haber got up from his chair and reached for his tweed jacket.  "To ground references," he said with finality.  "From radio beams to light beams -- zat is the problem."  I followed him into the hallway.  He turned to lock onto my eyes.

"Vhat zen is your solution?" he asked.

"Give me a week," said I, stoked to the core.

Dr. Haber strode off down the hallway.

The solution, of course, was right under my nose.  The approach-light simulator in my lab at UCLA was really the prototype for what you see today -- decades later -- still in operation at all the major airports.  The official name for the system is HIRL for High Intensity Runway Lights -- a row of xenon flash tubes atop short towers, firing in rapid sequence, beckoning the pilot unambiguously toward the runway.

Little did I know in 1954 that a dozen years later, I would become the direct beneficiary of the HIRL.

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