High Hot and sometimes Heavy

As a Colorado based aircraft management/charter company we are no stranger to operating in and out of some of the world’s toughest airports. These scenic mountainous airports include Aspen/ Pitkin County, Vail Eagle County Regional, Telluride and Gunnison-Crested Butte. Leadville (just 26 miles east of Aspen) is North Americas highest airport sitting tall at 9,927 feet above sea level. With Denver International Airport over 100 miles away from most mountain towns these airports provide access to some of Colorado’s most desired ski resorts and beautiful vacation destinations. Private air travel cuts travel time from Denver into minutes but operating in and out during the summer months is a lot easier said than done.

Aircraft performance is the name of the game and Mother Nature is numero uno in what a plane can and can’t do even when there isn’t a cloud in sight. For mountainous region airports the term “Density Altitude” can sometimes be foremost in determining what a aircraft can and can’t do. It's hard for most people to understand something you can’t see nor touch but in order to understand aircraft performance you must first have a understanding of the negative effects density altitude can have on a flight. Because it can’t be visualized, D/A can be somewhat tricky to understand.

By definition, density altitude is “the pressure altitude adjusted for non-standard temperatures.” To simply put it, when increasing temperature at a given atmospheric pressure this will cause the air density at that given pressure to appear as though it resides at a higher physical altitude then it is. Pressure temperature and the humidity determine air density. On hot days, air is lighter or thinner, so the density is equal to the density at higher altitudes in standard atmosphere and thus the term “high density altitude. On a cold day the opposite occurs and the air becomes thick or heavy and the density becomes that of atmosphere lower than your altitude “low density altitude”. Density altitude is a index to the a aircrafts performance, so low density altitude increase performance where high density reduces performance. Performance reducing affects comes in three ways (1) It reduces power because the engines take in less combustible air (2) Jets have less mass of gases to spit out the exhaust (3) It reduces lift because the light air exerts less force on the airfoil or wings.

The results of high D/A lengthens the takeoff and landing rolls and can dramatically reduce the aircrafts ability to climb. Faster groundspeed is required in order to takeoff therefore the aircraft requires more runway. The true airspeed is faster which means the plane cover more distance and so you climb at a much shallower angle. This holds true for all aircraft.

Denver Colorado is already at a disadvantage at a elevation of 5500ft hints the name " Mile High City". With airports at high elevation, short runways, terrain and obstacles, high temperatures limit the ability to execute flights that typically are no problem during winter months and cooler temperatures. The result can be smaller passenger loads, less fuel which in turn reduces aircraft duration.

The effects of D/A are insidious but there are some good ways to fight back this hot high pain in the back side. First off, try to depart early or late in the day, any reduction in temperature helps. Vail, Eagle County is open 24hours a day and is controlled from 7am- 7pm. Aspen is limited to day light hours and opens for operations at 7AM daily. Second, use airports with more usable runway if possible, the longer the better. Third, pack light, the less weight the better performance and longer the range.