Understanding why the wing and engine behave as they do has everything to do with air density and, in the case of engine performance, the proportional amount of oxygen (O2) available. The most important thing about DA is the density part. It behooves us to understand what it means since it affects the performance of multiple systems. ![]() While DA is a single number, an apparently simple answer to a multivariate problem, our thinking about it should not be one-dimensional. ![]() Finally it affects true airspeed so you will have a faster ground speed at landing and a longer ground roll to get up to speed on takeoff. We all know it affects the wing’s ability to generate lift, but it also reduces the propeller’s efficiency in generating thrust and the engine’s ability to find enough oxygen to produce power (particularly when humidity is involved). But thanks to DA posing multiple performance threats, it is the combination of all three that must be considered. “Just as beginner pilots can fixate on an instrument, it is easy for pilots to fixate on a single factor and neglect any others. There are three factors to consider in DA-the triple-whammy of temperature, pressure and humidity. Anyone who’s flown in the summertime, including from sea-level airports, has experienced some form of DA. High-altitude pilots just have a head start when it comes to familiarity with DA. In case you’re thinking density altitude (DA) is strictly something that concerns mountain-flying enthusiasts like me, you should know it is not a concept unique to the high country. The next one is if you land, can you make it out safely? Quite often there are good reasons to do neither, with perhaps the biggest single factor being density altitude, usually when trying to take off at the planned time. ![]() When considering landing on a runway with marginal length or a difficult or obstructed departure path, the first stage of aeronautical decision-making is deciding whether to land in the first place.
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