Flooding is not the only mischief Mother Nature has visited on the Wood River Valley this month. Pranks with winds and warm weather have created turmoil for aircraft operations at Friedman Memorial Airport in Hailey.
During several hours in afternoons, the combination of tail winds, higher temperatures, strict aircraft performance requirements and the shortened usable length of the one runway have worked to prevent some aircraft from takeoffs and landings Others have been forced to reduce their loads.
Takeoffs are permitted only to the south.
SkyWest Airlines station manager Roger Southerland confirmed that one or two passengers on average have been denied boarding to reduce takeoff weight of afternoon flights of the twin-engine 30-passenger Embraer Brasilia aircraft. He said they're given various compensations for the inconvenience.
Horizon Air's station manager, Chad Hastie, could not be reached immediately to determine his air carrier's experiences.
At Sun Valley Aviation, Friedman's only service and maintenance operation, general manager Melidee Wright said that some corporate jets also have reduced their takeoff weight to accommodate the afternoon weather conditions. For example, she said pilots might take on only a third of a full fuel load.
Takeoff and landing performance of all aircraft are affected by airport altitude (Friedman is 5,320 feet), temperatures, humidity and wind. When computed together, they generally add up to "density altitude" that affects aircraft lift. Pilots then calculate how much runway is needed and at what aircraft weight for their aircraft's performance.
In addition to performance parameters specific for each aircraft, owners add their own margins for safety.
Steven Garman, chief pilot of Sun Valley Air charter service, says that he operates at even higher standards. Using a "factored landing distance" chart, Garman explained he must be able to land without thrust reversers of his Learjet 60, the most powerful of the line, stop only with brakes and add 66 percent to that distance.
Like most state-of-the-art jets, Garman's Lear has an onboard computer system that calculates landing and takeoff distances using an array of factors.
Friedman manager Rick Baird explained that construction crews are continuing to build a 600-foot paved safety zone at the south end of the 6,952-foot runway.
This is a separate project from the lighting and drainage construction that required Friedman to be closed from April 24 to May 10.
During this work phase, 1,000 feet of the runway has been closed because of workmen and equipment at the end, and designated as an emergency "accelerate-and-stop" area for aircraft that might abort takeoffs, Baird said.
So, the useable length of the runway has been cut to about 5,900 feet.
Baird said this information has been widely distributed to aircraft operators and will be in effect for 30 to 35 days.
Friedman will be closed again in September to allow for final touches on the safety zone work.
He added that aircraft encounter the same problems in the summer with the full runway in use.
If and when a new airport is built, perhaps by 2017, it will operate a runway of at least 8,000 feet.