By Rob Finfrock
Though the calendar maintains that winter is still a few days away, cold weather has already made its way across continental United States. Blustery winds and freezing temperatures are already being felt on airport ramps from coast to coast, chilling both aircraft and their pilots in equal measure.
Should you need to leave your Citation on a cold ramp instead of inside a warm hangar, it’s important to secure the airplane as if there’s going to be a major storm. That includes using the recommended gust locks and controls… which should be your standard practice, anyway.
It may also be helpful to review wintertime practices in your aircraft’s operating handbook, including what fluids should be topped off, and how to adjust tire pressures.
A number of engine covers are also available to keep the frigid air – and wildlife, looking for a warm nesting spot – out of your Citation’s nacelles. Wing covers are another good idea to keep frost and ice off the wing skin and moisture from seeping in to the structure.
Similar covers are available to shield cabin windows, and in some cases most of the fuselage; while they can be pretty expensive, they’re worth the cost if you do a lot of winter flying.
Cold Weather Operations
It’s especially important to amend your operating practices in consideration of wintertime conditions when taxiing out, and upon taking the runway.
If utilizing deicing services, operators should review the FAA’s Holdover Times and Allowance Guidance, an important advisory regarding the estimated period for which various anti-icing or deicing fluids will prevent the accumulation of ice, snow or frost on the aircraft. The guidance, which is frequently updated by the agency, is available here.
Additionally, pilots should be especially cautious when determining surface contamination on the aircraft’s control surfaces. Even a small amount of frost, snow, or ice can seriously disrupt airflow over the wings and empennage surfaces, leading to a potentially life-threatening situation when attempting to take off.
And, of course, pilots must take runway contamination into account when deciding to take flight. Even a well-plowed runway may still have numerous slick spots from melting snow, significantly adding to takeoff distances. A slippery runway may be especially problematic when you must also deal with a significant crosswind, or even a tailwind.
These considerations are also key when it comes time to land. According to a report by the Flight Safety Foundation, runway overruns accounted for fully half of all excursion accidents between 1995 and 2008, with many of those cases involving an aircraft that departed the runway surface due to a lack of adequate deceleration on rollout. That makes it important for pilots to understand how braking action reports are conducted.
Braking Action Reports May Be Friend and Foe
The coefficient of friction between a landing gear tire and a paved runway surface is often defined by the Greek term Mu (pronounced “mew) in determining the level of runway braking action available.
Braking action measurements are typically expressed through four terms – good, medium (or fair,) poor, and nil – with “medium” representing a slight reduction in braking and/or directional control, and “poor” a significant reduction. The most severe conditions are often included in the field’s ATIS recording, or published as a NOTAM.
How an airport may arrive at those figures, however, can be a bit nebulous. Some larger airfields have the necessary continuous friction measuring equipment (CFME) to determining runway braking action, but these reports are not always accurate due to differences between the weight of the vehicle (usually a small car or truck) and a landing aircraft. CFME reports are often taken along a relatively small section of the runway surface, as well, not the entire area available for landing.
That said, many GA airports rely solely on pilot reports for braking action information, leaving arriving aircraft beholden to the reporting skills of prior crews… or, being placed in the uncomfortable role of test pilot, if no other planes have used the runway in the past hour or so.
With some foresight and relatively minor planning, however, the hardest part about cold weather flying may be the walk from a warm FBO to the door of your Citation.