An interlude with reality!

The most difficult inertia to overcome is human inertia. We like to do things the way we have always done them. I once had a student who was a tool designer for a large company. He was visiting a shop where several machines he had designed were in operation. He noticed that one of the machine operators was using a lathe incorrectly. When he pointed this out, the workman replied "Son, I've been running this lathe for ten years so I don't think I need any advice from you." As it turned out, my student had designed that lathe about 15 years prior. True, the workman had lots of experience operating the machine, but he was operating it incorrectly. He was getting the job done, but not near as well as he could have. Just because you have been doing something a certain way for a long time does not mean it is the only way, or even the best way to get the job done. The value of experience is not in question, however experience in doing something the wrong way can form bad habits that are hard to break.  FYI, it takes 7 times as long to replace a bad habit with a good one, as it takes to learn a good one in the first place.

I would like to discuss some of the realities of flying an airplane. Aviation, like other endeavors, has it's share of old wise tales and outdated procedures. One of these is the misconception that Pitch controls Airspeed and Power controls altitude. Many were taught to fly this way, as I was when I learned to fly in the late 1960's. The concept conflicted with some of the things I had learned in Physics classes, but who was I to argue with 60 years of flying tradition. I flew the airplane like my instructor told me, and things worked out all right.

After returning from a year in a tropical paradise, (food, clothing, weapons and accommodations provided by the US Army) I had to deal with the fact that my CFI was about to expire. The FAA was conducting a flight instructor revalidation clinic. I jumped at the chance to attend.

The chief instructor asked the class of about 100 people "What controls airspeed and what controls altitude?". Of course everyone answered "Pitch controls airspeed and power controls altitude." He did not agree with our answer. As a matter of fact, after thinking in terms of the physics I spent so much time with in school, I did not agree with our answer either! Now that my mind was open about the subject, I listened to what the man had to say. Nobody wants to engage in a discussion where they and the person about to grant them certification have a difference of opinion. Knowing this, the FAA Inspector asked us to try just 5 ILS approaches using pitch attitude to control the glidepath, and power to control airspeed. We were then free to make up our own minds

I did not like the first approach. After the second, I said to myself "This will work, but I like the old way better." The third approach convinced me that the way the FAA man suggested worked just as well as the way I was doing it before. After the 5th ILS, I was sold. Controlling the rate of sink with the pitch and the airspeed with power was easier and more accurate. Another advantage of the "new way" is that works the same in all airplanes.

The old way (pitch to airspeed & power to altitude) does get the job done, but only works in airplanes where power application causes the nose to rise and power reduction will cause it to fall. Many jets have engines mounted above the center of gravity with the inlets pointed slightly up to align with the airflow pattern created by the wing. This causes the aircraft to pitch down when thrust is increased, and up when thrust is reduced. So, if you are slightly below glidepath and add power to correct it, you wind up farther below going a bunch faster. Conversely, if we are above the glideslope and reduce power to correct, we wind up high and slow.

The following is a statement of the laws of physics, not just my own personal opinion.

"When power is Variable, Power controls airspeed."

"When power is fixed, Pitch controls airspeed."

In general, airplanes go where you point them, and go as fast as the power dictates. This is the easiest way to fly, and it works in all airplanes.

You may say, "Then why have I been able to control my glideslope with power and my airspeed with pitch all these years if I am so wrong?" Fact: On most airplanes, increasing the power increases the airflow over the tail surfaces. Since the horizontal stabilizer exerts a downward force, adding power causes the tail to drop and the nose to rise. A reduction in power causes the tail to rise and the nose to drop. There is the root of the old myth. Yes, you can make the myth work on some airplanes, but it is more difficult than doing it the proper way. The proper technique will work in any airplane.

One fine day, I was conducting an instrument flight test in a helicopter. The applicant did his before takeoff checklist, rose to a hover and promptly told the tower controller (not clearance delivery or ground) that he was "Ready to copy IFR to Orange County". The controller politely suggested that he set the helicopter down and contact ground control for his IFR clearance. Once we were back on the ground, I asked why he didn't contact ground in the first place, as our departure airport had no clearance delivery frequency. He replied "Well, that's the way we always did it in St. George!" I explained to him that there is an advantage in using the proper procedure for obtaining a clearance as outlined in the AIM. The advantage is that the proper procedure works at all airports, not just the one he is used to. My point here is, the proper flying techniques work in all airplanes. Airplanes fly pretty much the same. I am sure you have heard many old timers say; "If you can get it started, I can fly it." Many times they are right! Don't get me wrong, systems knowledge is essential to safe flight, but airplanes all fly about the same.

It takes energy to move the airplane through the air. The amount of energy it takes depends on desired speed, type of airplane, weight, and configuration. Since we can fly only one airplane at a time, and weight doesn't change very quickly in flight, configuration and power are the two variables we use the most. Flying is a matter of manipulating some simple variables.





You can perform any maneuver in an airplane by manipulating those four variables to achieve your goal. Sure, there is a little more to flying than just those four things, but that's all there is to manipulating the airplane. Systems, judgment, and flight planning are all required elements, but driving the airplane breaks down to those four basic variables.

The energy or power required to maintain a given airspeed remains constant. (Unless you change the configuration.) This energy can come from two sources. Converting fuel to energy, and converting the aircraft's potential energy (weight x height) into kinetic energy by losing altitude. The aircraft's speed is a function of how much energy is being used, not where the energy comes from. When you start descending you have three choices, reduce power, add drag, or gain airspeed. When you start a climb, you will add power, reduce drag or lose airspeed. Point it where you want it to go, and make the necessary power adjustments. If you reach idle or maximum power, you have reached the limit of your climb or descent angle at that airspeed.

When power is Variable, Power controls airspeed.

When power is fixed, Pitch controls airspeed.

Remember this and flying airplanes will be much easier.

Helicopters are another matter.