The propellers on most military planes at that time were primarily constructed of aluminum and were very sophisticated. All the blades on each single propeller could be rotated simultaneously on their shafts by the pilot while in flight to obtain the desired blade angle or pitch for maximum performance and efficiency... Also, a hydraulic governor maintained the propeller's revolutions per minute (RPMs) set by the pilot. So what's this got to do with propeller feathering? Vella yusta minuten anna Ima gonna told you. Sometimes while in flight a pilot could "lose" an engine. For whatever reason the engine would cease to function or the governor would go awry and allow the engine RPMs to increase so dangerously high that the engine could be destroyed. In most cases, the engine was then of little or no use and had to be shut down. But the useless propeller would still be spinning around like a windmill thus creating a tremendous amount of drag. So what could the pilot do about that? Well, we finally got to it! He could "Feather the Propeller!" How about that? Feathering the propeller forced each blade to rotate on its shaft beyond the limits of the governor so that the leading edge of each blade pointed directly into the wind and stopped rotating, thus eliminating all wind-milling drag. To do this, the pilot simply pressed a large red button located over the windshield and labeled "FEATHER" which would immediately activate a special high-powered pump... that forced the prop blades to move very rapidly to the feathered position... Using the feathering button was considered to be an emergency, and feathering a useless and wind-milling propeller could mean the difference between remaining airborne or going down. I remember using the feathering button one time but for a slightly different reason, unknown to most pilots, which got me out of a tight position. It was in Alaska around 1954 or 1955 and I was flying a C-47 twin-engine cargo plane one winter night from Anchorage to McGrath and was passing just to the south of Mt. McKinley heading west. It was extremely cold with light snow falling. Now snow is OK since the moisture is already frozen and is nothing to worry about. But at my cruising altitude and because of a temperature inversion, the moisture was now freezing rain and not snow. Knowing my plane would ice up, I turned on my wing de-icing boots and the prop anti-icers which sprayed a form of alcohol on the spinning props so they supposedly would not ice up and become just spinning clubs and lose their effectiveness. But in spite of the anti-icing spray the propellers were still icing up heavily and I started losing airspeed. There was only one other thing I could do. I moved the propeller controls to maximum RPMs to throw the ice off the prop blades by sheer centrifugal force, which they did. Chunks of ice slammed against the fuselage just to our rear as it was hurled off the props and caused my inexperienced co-pilot quite some concern and alarm. After the banging stopped, I moved both prop controls to normal cruising RPMs. The left engine returned to normal but the right engine stayed at maximum RPMs and nothing worked to return the RPMs to normal. Apparently the hydraulic oil became so cold that the prop governor could not handle it. So what to do? Return to Anchorage? Continue to McGrath? Let the engine burn itself out which it would at that RPM? I didn't want to shut it down because I needed what little power it had. The whole plane was now picking up ice and one engine couldn't hold my altitude. I decided to let the right engine destroy itself and return to Anchorage even though I was closer to McGrath because McGrath was a small remote station with practically no facilities and no emergency equipment. Then a thought struck me! If I pressed the feathering button, the powerful feathering pump would take over and force the blades to go rapidly from their flat, maximum RPM position to the feathered position. En route the blades would have to pass through the angle that I wanted for cruising. At that instant, if I immediately pulled the feathering button out to stop the feathering process, would the prop blade angles and RPMs stay there? What is there to lose? I'm in trouble. So I tried it and yes! It worked! And surprisingly, the prop governor worked OK now and I was able to control the RPMs normally. So I continued on and landed at McGrath without further incident. This trick of using the feathering button to reduce RPMs to arrive at the desired prop pitch or blade angle was a novel innovation and I was called upon to spread the word to the other pilots. The only reason the thought came to me in the first place was because I used to be an airplane mechanic during my enlisted days and was familiar with all aspects of an airplane. This knowledge could possibly have kept me from busting my ass on this occasion. At the very least, it most certainly got me out of a most uncomfortable situation. This story was edited slightly for clarity and brevity... -L.Y. |