Power-Off 180s

Energy management. That's what Power-Off 180s are all about. For those of you who don't know a Power-Off 180 is a simulated engine failure to landing. On downwind abeam your touchdown point you pull the power to idle and try to land with in a certain distance from your touchdown point. While many people do this maneuver for their Private Pilot training it isn't actually required for you to pass a check ride.

To pass your Commercial check ride you need to do a Power-Off 180 Accuracy approach and landing. The key word here is accuracy. What does accuracy mean? From the PTS "touches down in a normal landing attitude, at or within 200 feet beyond a specified touchdown point."

Why is this so difficult for students? Again I'm going to say energy management. Thinking back to your long days studying physics you obviously remember that there are two types of energy, Potential and Kinetic.

The bare bones description of potential energy is energy that is stored within an object, energy that can be converted to other forms of energy. Kinetic energy is the energy that an object has due to its motion. A good way to think about this is altitude above the ground is stored energy, potential, which can be traded for airspeed, kinetic.

Back to the maneuver at hand. Depending on the airplane you need to time your turn to base depending on your sink rate. I'll use the C172 and Piper arrow as my two examples. Both of these aircraft start the same way, pull the power abeam your touchdown point and start pitching for your best glide speed. When you pull the power on the C172 you need to keep going on your downwind leg for a bit, however on the Piper Arrow you need to almost always start your turn to base right away.

Base leg is the most important part of this maneuver. This is where you determine if you have the right amount of energy. If you are going be high you square off your base turn to final turn, if your low you are going need to turn towards the runway and shorten your pattern.

So why is this difficult? Well most students don't understand that you aren't judging whether you are high or low but rather judging your sink rate. Do you have enough energy to make it to the runway? Do I have enough potential energy, altitude, that I can trade for airspeed to make it to my landing point?

If you are too high there are a few things you can do, slip the airplane, square off your base turn, or add flaps. However the one that not a lot of people know about is slowing the aircraft up to below best glide speed. If you pitch down to loose altitude you are going to gain airspeed, kinetic energy, and float past your landing point. However, if you pitch back, you increase your induced drag(drag due to lift and AOA) . Because of this increase in drag you will now be able to descend faster.

This is a very difficult maneuver to perfect but a very important one. In a real engine failure emergency you don't want to miss your only landing area by floating long or coming up short.
Link to a youtube video: http://www.youtube.com/watch?v=2nCDyL3toEg&feature=related