Issue 161
March 2021

SO WHAT IS DENSITY ALTITUDE? As altitude and temperature increase, density altitude increases along with it. Humidity is also a factor with density altitude, although its effect is much less significant than temperature and altitude. In terms of aviation, density altitude is how the airplane "feels" like it's flying. The aircraft performs less than normal, engine power is reduced and runway required is extended...often greatly.

For example, airplane acceleration is slow going down the runway on a hot and humid day. The plane also needs to move faster and climbs slower when density altitude is high. With this key knowledge in mind, pilots can make smart decisions when it comes to takeoff, flying, and landing airplanes.

Thin air at high density altitudes reduces force on the lift because it applies less force on the wings. It also reduces the engine's power because there is less air to mix with fuel. This combination often results in dramatically lower engine performance than in environments without thin air.

When it comes to flying in thin air, one major influence that will impact airplane performance is horsepower. Density altitude is known for reducing horsepower in aircraft engines. For example, a normally-powered airplane will lose 3.5% of its horsepower for every 1,000-foot increase in altitude. This decrease in horsepower will force the pilot to consider the number of people flying in the airplane as well as the amount of fuel.

While it's clear that density altitude has a significant impact in the world of aviation, how do you measure it to ensure a stress-free flight experience? There are quite easy to use DA Apps for Smart Phones available.. or one for PC users.

http://www.pilotfriend.com/pilot_resources/density.htm

They can give you a better insight into density altitude and any complications that may associate with it. It can prepare you to help make decisions such as:

• Flying early in the morning or later in the evening when temperatures are lower.
• Ensuring the aircraft's weight is at <90% of the gross maximum weight of flying in high-density altitude conditions.
• Don't fill the tank to the top.
• Make extra fuel stops.
• Take shorter flights.

Remember: No one has ever collided with the sky.

Cheers

 Ian McDonald

PS - do you have any questions or points of interest you'd like me to discuss or investigate. Drop me a note.
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