Jumpseat: Deviation Woes

Thunderstorm avoidance in an airliner isn't always a piece of cake.

Jumpseat Buenos Aires

Jumpseat Buenos Aires

Route and weather to Buenos Aires.

Hovering over a counter in Operations, I tapped at my iPad screen. I was reviewing WSI weather information for our flight south from JFK to Buenos Aires, Argentina. The satellite picture indicated a wispy but clearly defined line of cloud cover that stretched in a curved path from the Florida Keys all the way to Canada's Newfoundland. The curve extended into an area over the Western Atlantic where our flight would apparently be routed by ATC.

The evil cold front that had slithered its way across the country from the Midwest to the East Coast had shifted its sinister energy out to sea. A red hexagonal shape from within the WSI map image of the cold front highlighted a narrow area of convective activity.

No big deal. The data was almost an hour old. Our flight wouldn't be in the vicinity for at least another hour. Cold fronts have the personality of being fast movers; this particular one was traveling northeast. We were filed for Flight Level 350, a respectable altitude that usually avoided the really bad stuff. And we were flying a robust 777, a 648,000-pound max gross weight airliner, one of the most sophisticated airplanes in the world. What could possibly go wrong?

Having a cavalier attitude isn't part of my job description. The convective picture was a concern. A thunderstorm system is a dynamic event. When questioning our dispatchers regarding the wisdom of routing that aimed directly at the weather, the actual flight proved their planning to be appropriate. On the majority of occasions, the storm moves away. It's a strategy used by water-skiers. What do I mean exactly? If a water-skier is towed near the shoreline on one side of a flat, calm lake, the tactic is to return back to the same side for the reverse run after a minute or two. The reasoning is that the wake will travel to the opposite side of the lake, dissipating from the original side first. In that regard, a line of thunderstorms will move its wake away from the flight route by the time the airplane arrives. If the water-skiing strategy proves wrong, it is rare that a break in a line of thunderstorms can't be found. A modest deviation would be all that is required. In our circumstance, extra fuel had been added for just such a contingency.

At approximately 22:30 we roared into a black sky from JFK's Runway 13R, the takeoff defining the last moment of a normal routine. Just prior to reaching cruise altitude, shortly after the exit from the cockpit of our relief copilot, it was becoming apparent that the original routing would not be a prudent decision. My copilot advised ATC that a deviation to the west would be required before entry into New York Oceanic Airspace. The fun began.

As I would discover upon our return home three days later, the cold front had begun to stall, making a transformation into an annoying stationary front. We were unaware this process was occurring as we traveled south to Buenos Aires, and the line of convection moved little as we approached.

Alas, a glimmer of hope appeared in the form of a small gap that would fit a 777. I don't like gaps. They are alluring. But gaps will close, sometimes with alarming speed. In addition, gaps may still contain areas of turbulence left over from the various stages of developing thunderstorm cells. Unless I can navigate through a gap visually, or no other option is available, I choose to avoid gaps altogether. It was a very dark night. The cloud-to-cloud lightning was picturesque but not luminesque. In other words, visual avoidance was not an option. If I committed to the gap, an escape route would not be possible.

That being said, my copilot expressed an inclination to give the gap a chance. If we chose to deviate instead, another airway would have to be assigned by ATC — an unknown factor that would require reference to an old-fashioned, high-altitude en route chart. Having entered New York Oceanic Airspace at this point, communication would eventually involve the often low fidelity of a static-infused high frequency radio in order to make the appropriate deviation request. The controller-pilot data-link communications system was available, but airborne text messaging can be tedious for such circumstances.

Although my copilot's tone conveyed resistance, he understood my unstated professional trepidations and resigned to negotiate a new routing with ATC. It didn't lend credence to my decision that a company flight behind us traveling to São Paulo had opted for the gap. I'm willing to place bets that a handful of chardonnay glasses were spilled on that flight, but as of this writing I have no verification.

Our reroute was offered without issues. New York Oceanic was prompt and accommodating, allowing us to deviate as necessary with ample opportunity to rejoin the new airway. Untypical for the flight, we flew nearer the U.S. coastline, altering our course almost 200 miles from our original dispatched plan. Unfortunately this large deviation would require a new strategic decision process, a fact that I had considered before the weather avoidance began.

The new strategy revolved around a simple concept: fuel. We would have less than anticipated for the remaining nine hours of the en route portion of our flight, notwithstanding our arrival and alternate contingency. So far, the computer's calculation and my estimate indicated more than the legal requirements. But would it be enough?

While we were still to the north of Puerto Rico and most of the Caribbean, the thought crossed my mind that perhaps we should consider a refueling stop in San Juan. South America, especially the vast remoteness of Brazil, didn't have much to offer in that regard. But as I contemplated an unscheduled stop, it appeared that our fuel consumption difference between planned and actual was indicating a steady decrease. Good news. Our early climb to FL 390 was helping. I silently opted to continue.

We weren't out of the woods just yet. The forecast for Buenos Aires and the surrounding area offered the real possibility that reduced visibility in the form of fog may be in our future. This was typical for the time of year. The fact that the evening metars were confirming this trend was not reassuring. I left the cockpit for my rest break with this thought, instructing my copilots not to allow any further weather deterioration. They nodded their heads in patronizing unison.

When I returned to the cockpit, it was apparent that Mother Nature was in command. The weather was now being reported in RVR. Not a good sign. Fortunately, our destination had a Cat III procedure, allowing us the ability to land with 600 feet of visibility. But the procedure wouldn't be the issue. The issue would lie with our sequence for the approach. Our arrival time coincided with many other airline arrivals. If we were required to delay in a holding pattern for other traffic, our fuel endurance would not allow much more than about 15 minutes before we would have to initiate the approach or proceed to an alternate airport.

Our nearest alternate, Montevideo, Uruguay, just across the River Plate north of Buenos Aires, was the most accommodating. It was a destination airport for my airline. But Montevideo's weather was also deteriorating. The alternate with the best weather was Cordoba, Argentina, approximately 375 miles to the northwest.

I formulated a strategy. If we were required to hold, we would only do so for 15 minutes. If weather forced a go-around, we would proceed directly to Montevideo provided the weather was acceptable. If the weather was unacceptable, we would fly to Cordoba. When my copilot returned to the cockpit from his rest break, I verbalized the plan. He endorsed the plan with a simple "Sounds good." We briefed the Cat III approach, setting the appropriate speed and altitude bugs.

Analogous to bringing an umbrella so that rain doesn't fall, my methodical preparation had the same effect. As we descended through 18,000 feet, I peered over the glareshield. Almost 50 miles away, I caught sight of the open area that defined the Buenos Aires airport. The fog was no longer. A few moments later, I clicked the autopilot disconnect button on the yoke and smiled. I was going to hand-fly a 777 today. Thunderstorm deviation? Piece of cake.

_This column was published in Flying's November 2014 issue. _

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