Dancing in the wind

Conway-Horry County Airport (HYW) in South Carolina had been a planned overnight stop on the way home from the Bahamas. Based on reported winds (260 at 19 knots gusting to 26), landing Conway’s Runway 22 would be challenging, but routine. Surprised by wind shear, it took a couple of bumpy orbits in the vicinity for me to settle on a diversion to nearby Grand Strand Airport (CRE). There, the flying day ended happily, the price of diversion being a few gallons of avgas and a longer cab ride to our hotel.

The personal operations specification

Personal minimums have been part of my general aviation flight bag since the mid-1990s. Back then, flying my young family around in the same Twin Comanche had highlighted a sharp contrast between decision making in two different flying worlds. There was a moon-launch intensity to personal flying decisions that was not at all present in airline flying. Around this time, a couple of senseless general aviation accidents took the lives of fellow airline pilots, proving again (if proof were ever needed) that skill and experience are no protection against poor decision making. Establishing personal minimums recognized that most airline decisions were made within clearly prescribed boundaries.

An airline’s FAA approved operations specification describes all kinds of limits and boundaries of an airline’s operation, establishing a confidence envelope that routinizes as much of pilot decision making as possible. Inside the envelope, operations are routine. There is still plenty of anomaly in airline operations—think Chesley “Sully” Sullenberger and the 2009 “miracle on the Hudson”—but creative response is reserved for the truly unpredictable. GA personal minimums are not nearly as comprehensive as the airline operations specification, but they derive their value from the same effect. The idea is to create, adhere to, and maintain an operational envelope that defines normal.

When it comes to crosswinds, setting personal minimums, anticipating the variables that can affect them, and planning an out can prepare pilots to handle circumstances that push their limits. The consideration that usually governs crosswind limits is a single number or limit value of crosswind component that includes steady state wind value plus any gust. One simply compares their own limit to the crosswind component of the reported wind. This limit represents an assessment of pilot/aircraft ability to maintain control through the approach, touchdown, and rollout. What this looks and feels like in a manageable-but-gusty crosswind landing is a kind of a dance—a very satisfying dance—when it turns out well.

The consideration that usually governs crosswind limits is a single number or limit value of crosswind component that includes steady state wind value plus any gust. One simply compares their own limit to the crosswind component of the reported wind.Control inputs continuously counter the dynamic effect of wind, arresting drift and recovering from float or sudden settling. Success comes at a point when the repeated dance of wind and correction reaches a condition of stasis—a condition of no drift and no sink—ideally at the time of runway contact. This single number limit, however, presumes that reported winds reflect what a pilot will experience on approach.

Airport selection

Airline operations are far more restrictive than general aviation operations in an important way. Airlines define which airports the airline will operate from, and even which airports may be used as alternates. This limitation stands in sharp contrast to the wonderful freedom of general aviation, which allows the Part 91 pilot to utilize any airport and conduct almost any type of operation with few explicit limitations.

Where surface winds are considered, airport selection is critical because many general aviation airports present topographical peculiarities that affect how winds are experienced. Local topography, which includes hangars and other obstructions often close to runways, dictates how a reported wind will be experienced. Knowledge of these conditions may abide in local pilots but is typically unknown to the visitor. By contrast, an air carrier airport is usually familiar to its pilots and presents a topographical sterility that permits a more consistent experience of reported winds.

Runway length, width, and surface contamination

The dance of the crosswind landing can take time and runway. Thus, longer, wider runways offer more opportunity to get things right than shorter, narrower ones. Also, normal crosswind limits are conditioned on dry, uncontaminated runways. These factors go beyond the single-number crosswind limit. My own crosswind limits already reflected this, reducing allowable crosswind for short or narrow runways and acknowledging that runway contamination must be considered. My personal minimums, however, did not contemplate a wind shear event.

Nature has the upper hand

The successful crosswind landing presumes continuous uninterrupted control, and here is the problem that cannot be assessed by reported winds and usual crosswind limits. Nature rejects the idea of being codified in an ASOS report. Without apology, it can wrest control from the pilot, threatening something basic and necessary to safe arrival.

Of course, a pilot’s protection from a wind shear event on approach is altitude. Early recognition allows altitude for recovery. Recognition, however, can begin long before approach.

Warning preceded our Conway arrival. Two cold fronts had passed through the East Coast in the preceding 36 hours, leaving a deep low stalled over the northeast.

Surface winds shifted and intensified during our flight northward. Descent out of cruise greeted moderate turbulence, and forecast winds would exceed my crosswind limits within hours of our arrival time. All these things suggested preparedness for diversion. The corrective action: having an alternate in mind for any single runway destination seems prudent, especially in windy months. The final protection is immediate recognition of wind shear, which can occur even when the wind is right down the runway.

What about takeoffs?

All the foregoing factors are pertinent to crosswind takeoffs with one important distinction. On the transition through ground effect, an aircraft is extremely vulnerable to a wind shear event whose possibilities can only be recognized in preflight assessment.

Planning ahead

On the return flight to our home base, single-runway York Airport (THV) in Pennsylvania, the forecast predicted 30-knot winds directly across the runway. En route reports upheld the forecast. So, a diversion to our filed alternate was fully expected. Then, listening to the York ASOS produced a surprise. Winds, still strong, had subsided and shifted. Approach began with the benefit of local knowledge. A steep descent (above the PAPI) would avoid an expected sinker caused by a wooded knoll to the west of the runway.

Arriving in ground effect, pilot and airplane entered the dance: gust, counter, float, counter, sink, counter, repeat. The left main was on, then right, then nose; slowing now, we were safely home. Prebriefed on the likelihood of diversion, my wife and longtime co-pilot considered me a hero for what was just a normal approach.

Chris Burns is a retired airline captain with 18,700 hours of flight time and is the owner of a Piper Twin Comanche.