Factors That Affect Aircraft Availability, Part 1

Business executives expect timely performance from their expensive aviation assets. Perhaps the CEO has an important meeting with the board of directors, needs to inspect a factory firsthand or is set to testify before Congress. Possibly the destination has a curfew that does not allow landings after a time limit in the evening, or the FAA’s approaches are not approved for night operations. These are just a few of the instances in which arriving on time is a necessity.

Advanced planning is a necessary element to prevent undesirable delays arising. While some delay-inducing factors can be readily predicted, others can occur without warning. What follows is a compilation of reasons that have stranded business aircraft in the past, much to the consternation of business executives.

Topography And Wind Effects
Let’s be honest: The primary weather parameters that pilots quickly assess to determine whether to launch to an airport are the ceiling and visibility. A weather forecast of clear ceiling and unrestricted visibility would normally give little pause to pilots.

There are, however, some "gotchas" within the weather forecast, that can limit one’s ability to safely operate. This is especially the case at topographically confined airports. Winds will be funneled up or down the bottoms of canyons, effectively limiting “one-way-in, one-way-out” airports such as Aspen and Sun Valley.

Let’s consider a forecast of a greater-than-20-kt. headwind for landing on Aspen’s Runway 15 on a summer afternoon. This provides a positive effect of reducing the landing distance as well as the ground speed at touchdown, all of which lessen the energy absorbed by the wheel assembly and reduce brake temperatures. However, if the schedulers expect you to drop your client, quickly refuel the aircraft and blast off to another destination, a takeoff with that tailwind is not possible.

The maximum certification tailwind limit for takeoff operations in a transport category aircraft is 10 kt. Furthermore, even if the tailwinds are just within the certification limit, the aircraft may not have the takeoff distance available under the combination of wind and hot-and-high conditions.

The winds caused by the diurnal warming and cooling pattern are easy to predict at airports confined in canyons. Nighttime cooling in the elevated terrain will cause a downhill flow of breeze through the canyons. Hence, on typical summer mornings, it is normal to experience the refreshing cooler “down-canyon” winds at these airports.  

A prime example of this effect occurs regularly at Freidman Memorial Airport (KSUN) in Hailey, Idaho. Since many mountain airports already sit at relatively high elevations, the morning tailwinds create additional limiting constraints.

If an atmospheric pressure gradient is creating the stronger winds, then the winds flowing through the canyon terrain can last for days. This can prevent the departure of aircraft at one-way-in, one-way-out airports until the winds subside.

If you are motivated to maximize the utility of your executive's aircraft, then a preemptive warning of, “Hey boss, once we land at Aspen, we won’t be able to depart for several days due to the adverse winds,” would give your boss a heads-up about this restriction and perhaps facilitate proactive changes in the schedule.

Ice Protection
One of the advantages of business aircraft is the ability to fly into lesser-traveled airports to place clients closer to their destinations. The downside of these locations can be the lack of services we normally expect from a large fixed-base operator (FBO) at a busy destination.  

The FBOs at smaller locations may not have sufficient supplies of necessary fluids for the re-launch of your aircraft. This is especially applicable if your aircraft requires TKS fluid, Prist, de-icing fluids or oxygen servicing.

An avid reader got “stuck” in Jackson, Wyoming, for nearly an entire week during inclement weather due to a lack of availability of de-icing fluid. According to this colleague, Air Force Two was sitting on the equivalent of “hot reserve” on the ramp and needed to be ready for an expeditious launch. A large quantity of de-icing and anti-icing fluids had been used by the Air Force flight crews, and this depleted the supply of de-icing fluids available for the civilian aircraft. Worse yet, the wintry road conditions had severely limited road access into Jackson, and thus the FBO was unable to receive its resupply of de-icing fluids.  

When flying internationally, fuel availability differs from within the U.S., and that can make it difficult to determine whether the locally available fuel contains the mandatory additives required by your aircraft. Something as simple as determining if the local fuel contains Prist can be hindered by a language barrier.  

Overnight Hangars
Being able to place your aircraft in a hangar if the overnight conditions are going to be excessively cold and/or include freezing precipitation makes a significant difference to the workload and timeliness of departure. In fact, a large fractional operator learned long ago that the ability to place its aircraft into hangars in Rocky Mountain destinations was a key element to minimize excessive delays and proactively negotiate contracts for hangar storage for the winter season.

If an aircraft sits outside overnight and is exposed to freezing precipitation, your workload is multiplied for the next morning’s departure. Chipping away at ice simply to get your key into the lock for the main entry door is a foreboding prediction of the misery involved in prepping your aircraft for launch.

If the wintry precipitation is excessive, either a massive amount of Type I heated de-icing fluid would be needed to remove the frozen precipitation, or else hauling your aircraft into a heated hangar (if one is available) will be necessary. This will significantly delay the availability of your aircraft.

Proactive communications with clients is a prudent move. But there is one advantage to delays at sky destinations such as Aspen or Bozemn: Your clients can take advantage of an extra day of skiing fresh powder.

Monitoring the engine start process after a period of freezing precipitation is important to prevent damage, in Part 2 of this article.