Lets Talk About Density Altitude
During your flight training you read or learned about density altitude, but do you really understand and respect it? I remember hearing the same thing over and over again from a few inexperienced pilots in Florida. “Yesterday I took off in the same plane, with the same weight and it was fine. So today I’ll be fine. No need to do the weight and balance again right?” WRONG. This is the way of thinking that will get you into trouble when you start to fly at higher elevations. Density altitude has a significant impact on aircraft and engine performance and it is effected by the 3 Hs: Height, Heat, and Humidity. I found this video that perfectly shows the effects of not doing proper performance calculations. The end is a bit gruesome but it’s still a great video to see how the plane, packed with 4 people, would not climb above the trees.
Understanding Density Altitude
For the sake of better understanding the discussion, lets quickly talk about what density altitude is, but for more information, visit my website for more in-depth details. Density altitude is mainly caused by 3 things: Heat, Humidity, and Height. All three of those things lower air density, which in turn raises the air density.
Heat: Hotter temperatures cause the air molecules to have a lot of energy and move further apart.
Humidity: With high humidity levels, water molecules displace air molecules.
Height: Lower atmospheric pressure (usually at higher elevations) causes air molecules to spread farther apart.
Put all 3 of those things together and imagine how your wings, engine, and propeller will perform with less dense air. It becomes a struggle to grip that “thinner” air.
Flying at High Density Altitudes
Pay attention to density altitude when doing your preflight preparation. In higher density airports, the density altitude will usually be given on the ATIS and advised by ATC when coming into the airport. However, don’t rely on that as your indicator, its best to find out density altitudes before even getting in the plane. You should use your E6B and POH to calculate density altitude and your planes performance. Higher density altitudes will increase your takeoff distance and decrease your climb rate. You will also see an increase in your GS (ground speed) and TAS (true airspeed) when flying your proper IAS.
Tips For Flying at High Density Altitudes
Keeping your plane as light as possible can help with getting better performance.
This one is pretty obvious if you’re a pilot. The less weight you have, the better the performance. However, just because you under the max gross weight, doesn’t mean you will have enough performance to takeoff. Do your performance calculations! (Maybe even just take one friend at a time instead of both of them.)
Determine your proper fuel/air mixture for takeoff.
This can be done by looking at your POH, the engine’s digital monitors, or a fuel flow gauge manual for optimum performance. One method you can use is, after your run-up, advance your throttle to takeoff power and lean the mixture for max RPM rise (make sure not to lean too much or you will actually have worse performance due to starving your engine of fuel). If you are flying to an airport of high density altitude, you can do the same thing in the air before you enter the traffic pattern. That way you know you have optimum performance incase you need to go around.
Make sure you are flying your IAS (indicated airspeeds).
Your stall speeds are based on IAS, so these are the speeds you should be flying. You will be showing a much faster ground speed than you are used to because at high density altitudes your ground speed will be higher than your equivalent indicated speed.
Make sure your runways are long enough.
When doing your performance calculations, make sure your runways isn’t just long enough, but you have a little bit of an extra buffer. The POH calculations are based on a new engine and airframe and you can't expect to see that same performance. A good rule of thumb is to reach at least 70% of your rotation speed by half of the runway length. If not obtained, abort the takeoff. So, if your rotation speed is 70knots, you should be at 49knots or faster by the time you hit that runway midpoint.
Use ground effect to your advantage.
Once your plane has lifted off the runway, pitch down and remain in ground effect to build up some speed, then use that extra speed to get a better climb rate. Sort of like you would do in a short friend takeoff, since well, this is a short field scenario due to density altitude requiring more runway for takeoff. Once you pitch up, your plane will start decelerating, catch your climb speed and hold that pitch.
Try to fly during times of the day when temperatures are lower.
This doesn’t need any explanation. Its pretty obvious why this is a tip. Although, I will say, keep monitoring current temperature because the temperature that you landed at might be different after you get fuel and grab a bite to eat. Maybe redo your calculations with whatever the current temperature is to make sure you’re still good to go.
Think you’re ready to go out and experience flying at higher density altitudes? Great, it’s actually a really cool thing to learn about and then visually see and feel how your plane performs differently. If you’re never experience it before, I suggest going up with either an instructor or an experienced pilot.
Don’t forget to leave a comment under the post and tell me about your experiences with flying in higher density altitudes. I’d love to here about them. Heck, I’m even open for any criticism. Did I miss something or explain it wrong? Let me know below.
But wait, before you go out and have some fun gaining experience, I found this great video from a youtuber that goes by FlightChops that I think you might want to watch. He helps explain that just cause the numbers say it can be done, doesn’t always mean it will or should be done. I’ve added it below.