Controlling Altitude
Before we put it all together and discuss the Stabilized Approach there is one more aviation concept to understand and this is the least understood and the most controversial concept in aviation. What controls up and down altitude changes in the aircraft? The wrong and most common answer is the elevator. The correct answer is POWER controls altitude and the elevator controls PITCH. Take a moment and think about this concept. To prove my point put you aircraft on the ground and give it full up, did it hop off the ground? I think not. The results with the engine running are similar, in flight with the aircraft trimmed for straight and level flight and the throttle set at full power, once you pull the power back you can apply as much elevator as you desire but you are still coming down. Still think the elevator controls up and down? The navy always had it right, even non pilots on carriers understood the concept. Think about any movie with aircraft carriers and aircraft landing. Somewhere in the movie there is always an aircraft approaching too low. Do the yell “Up, Up” or “Elevator, Elevator” over the radio? Never, it’s always “Power, Power.”
Here is an experiment to try next time you fly and this is a simple and real good technique to learn. Trim the aircraft to fly straight and level at ½ to ¾ throttle. This should put the aircraft in a flight attitude slightly slower then full power trimmed with a slightly nose high attitude to maintain level flight. Without touching the elevators add and decrease power and with each change in power the aircraft will climb and descend accordingly. Now to end the exercise, see if you can adjust the THROTTLE ONLY to reestablish straight and level flight. This is the basics to a Stabilized Approach. It is also a good practice to trim and fly your aircraft at a slightly lower power setting then flat out. First it will use less fuel, run cooler and having some reserve power is essential for proper aerobatics. You will find most proficient pilots never fly their aircraft at full power when in straight and level flight with the exception of a high speed fly by.
While we are on power settings lets discuss throttle set up. I learned to build and fly in the old school before computer radios with engine cut off switches and still prefer this method of throttle set up. I set all my aircraft up so at closed throttle and full down trim the carb is completely shut and the engine will not run. At ½ trim the engine is at low idle and I can make minor adjustments in the trim to maintain a satisfactory low idle. Also on the newer radios you will find the throttle trim is disabled once the throttle is moved above ½ throttle. This means that with the trim set at ½ and the throttle full open the trim will be inactive and the carb will be fully open with the throttle only. Drop the throttle below ½ throttle and the trim becomes active. This feature makes my set up even more effective and easier. In the old days I used to have to move the trim full on to achieve full throttle, now I don’t have to touch the trim until I want to shut down the engine.
Take some time this month and get you aircraft set up with the trim capable of being the engine cut off and also trimmed for straight and level flight at a slightly reduced power setting. If you need some help with any of this please give me a call, I will be glad to help you
OK, we are almost there. Next Month we tie it all together and fly the Stabilized Approach
This is #6 in a series of 7 total articles submitted by Joe Papasso
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