“The Client Wants to Land Where?” | Flight Today | Air & Space Magazine
Avoiding the mountains looming over Paro focuses the mind wonderfully. (Poowin Bunyavejchewin)

“The Client Wants to Land Where?”

Could we fly a bizjet into a remote strip in the Himalayas?

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Managing a fractional ownership business like NetJets has been compared to maintaining an antique watch: Every cog, spring, and wheel must mesh perfectly. My particular cog is flight operations engineering, a field dedicated to solving the daily problems that most air travelers never consider: Our pilots can’t just gas up and take off. For each flight, we must answer fundamental questions. How much can we carry? Where’s the worst place to lose an engine? What happens next? Our job is to simplify the answers so pilots and dispatchers don’t have to dig too far into the flight manuals, pound away on calculators, or call the ops engineer at 3 a.m. The tables and charts they rely on for those can-we-do-it questions are the result of hours of research and calculations. Still, one 2008 trip required the most extensive research effort I’ve ever been part of.

Tucked away deep in a valley in the Himalayan country of Bhutan is the remote town of Paro. Of course, “remote” depends on one’s perspective: Considering that Paro hosts its country’s lone commercial airport, the place is a bustling metropolis. One of our charter clients, a television travel program, had requested a flight to Paro as the highlight of an already complex trip two months away.

In the on-demand charter business, two months is a luxury. And judging by our chief pilot’s reaction, this trip looked to be particularly exotic. Studying maps of the airport environment, we found it sat at 7,000 feet above sea level and was surrounded by mountains topping 18,000 feet. Adding to the challenge, Paro is a daytime-only airport that offers only Visual Flight Rules approaches, landings for aircraft in our category, and takeoffs. The crew would be flying into a granite bowl without a usable instrument approach, and we had no time to create customized procedures. The answer seemed to be: “No way we can do this.”

But then the pictures showed up. After doing his own research, our customer had found a story in Boeing’s Aero magazine about proving flights the company had made into Paro with a Boeing Business Jet, an executive-class 737-700—the very aircraft we’d be flying. Once we were faced with photographic evidence of an identical airplane at the same airport, “No way” became “Now what?”

Fortunately, we were able to contact the performance engineer who’d designed Boeing’s procedures, and the test pilot who made the flights. Both had their own perspectives and tales: While looking for Paro, it was reputedly easy to become disoriented and turn down the wrong valley. There had been reports of pilots flying to the edge of a stall to escape that very situation.

We were able to get remarkably detailed topographic maps created by the former Soviet Union and terrain data from NASA’s space shuttle radar topography mission. Charts, performance tables, and pencil in hand, my first crack at a departure plan would maximize the crew’s time climbing straight up the valley, but in the end bore a remarkable resemblance to a treble clef superimposed on a topographic chart.

“So that’s it?” chief pilot Rick Weeks asked after I presented the graphics.

“No, seriously, what have you got?” asked safety director Mark Atterbury.

“That’s it,” I replied. “You guys wanted to leave Paro with a nice, steady climb up out of the valley. That’s the only way I can find to do it.”

Which was true, but the departure we had jokingly named the Whifferdill had a critical weakness: The crew could indeed make a gentle climb straight up the valley and keep any turns within 15 degrees of bank angle, but that would eventually lead them into a blind turn around a mountain ridge—still below the peaks, with God-knows-what kind of weather in the next valley. There was plenty of maneuvering room, but they couldn’t risk flying into unseen weather around the bend with mountains still towering above them and no instrument references.

The weather itself presented another challenge. Though the airport would open at dawn, at that time of year it was usable only until about 10 in the morning, when the valley winds would begin howling up around the ridgelines. Each morning, our crew would have about a three-hour window to arrive and depart. We’d also learned Bhutan’s monsoon season was about to begin, so each passing day lessened the likelihood that we’d pull this off.

In the meantime, our customers were hurriedly finalizing their production schedule. Paro would be the center in a long line of dominoes. As we would be hopscotching the customer around the world, the most likely scenario would be that we’d land there just fine but be unable to depart the next day, thereby wrecking their fine-tuned plans. Fickle Himalayan weather guaranteed there’d be no sure way to know what was in store until we arrived.

While I continued designing elegant curves that fit the airplane’s performance within those nasty-looking terrain contours, Atterbury set off on a couple of road trips.

He and Weeks had contacted Bhutan’s national airline, Drukair, to glean insight from their counterparts on the other side of the world. Insights such as: We had literally been attacking this problem from the wrong direction. After flying in the jumpseat of a Drukair jet, Atterbury made an important observation. Just looking at maps, the obvious path out of Paro appeared to be southeast but without the dreaded Whifferdill. But when he stood on the runway, it became obvious they were better off going in the opposite direction—which pointed straight at the mountains. It was, in fact, Drukair’s preferred departure and a valuable illustration of the need for an experienced crew member on site.

From where I sat, it looked nuts: The crew would immediately have to bank right, pointing the nose at an imposing mountain, then honk it through a 270-degree climbing turn inside a box canyon to come out above the ridge and head back over the runway. On the plus side, from the runway, they’d be able to see everything inside the turning area. Nothing was hidden, which made it the best choice.

With three weeks to go, we still had to train our crew, chart the procedure, identify obstacles, develop weight and speed tables, and arrange for a Bhutanese safety pilot to ride shotgun. I paid for the custom charts and flight simulators on my company credit card, and our crew shipped off for Manchester, England, which had the only visual model of Paro in the Western Hemisphere.

Back home, I was still crunching numbers and seeing that valley in my sleep. It’s not enough to determine a crew’s ability to fly a given procedure. We also have to figure out how much of the runway they’ll use, flap settings, and critical speeds—all based, of course, on losing an engine—to arrive at the crucial number: How heavy can that airplane actually be?

The answer was “not very,” which introduced another limitation: Less weight equals less fuel equals less range. It could be a clear day in Bhutan, but if there were no usable airports within range, they’d be just as stuck.

As the departure date loomed, all those uncontrollable factors weighed heavily on us. As each day went by, we scrutinized conditions closely, repeatedly calculating winds and their effect on fuel consumption. Finally, the day arrived.

It didn’t help that all the critical events would happen when it was the middle of the night in the States. I went to bed that evening, anxious but hopeful, knowing that our dispatchers were keeping a close eye on every detail.

The next morning, I awoke to learn the weather had held off and they’d made it through just fine. In Atterbury’s words, the airplane climbed out of that valley “like a homesick angel.” And after so much work to see this project through, there was a unique benefit: flipping on the TV to see how it had paid off. My family and I watched the client’s travel program, so I could show them what had been keeping daddy up so late for the past two months.

Patrick Chiles has worked for NetJets since 1998 as a flight dispatch supervisor, performance engineer, and safety manager. His first novel, Perigee, is a techno-thriller set in the commercial spaceflight industry.

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