Don’t Touch That Prop!

The title gives this one away, but it is still worth explaining how it happened, so you can avoid having a similar problem in your life. This is the tale of two friends and their favorite airplane, a pristine, beautiful Cessna 140, and an equally nice Beech V35B Bonanza. Both were co-located in the same heated community hangar at a local airport, and both received care, attention, and a regular regimen of flight from their doting owners.

THE DAY WAS CLEAR, without a cloud in the sky. The two partners decided to take a flight in the Cessna 140, since it was cool and clear, for a ride to a local airport. Their destination had an excellent breakfast waiting, so they wasted no time and completed their preflight.

UNFORTUNATELY… The priming line had vibrated loose from the fitting, and had fallen off the cylinder of the Cessna 140. The plane was pulled out of the hangar, primed as usual, and several attempts to start the plane were made. Without the primer, the usually reliable Cessna 140 refused to start. Dejected, our partners pushed it back into the hangar and began troubleshooting.

THE PROBLEM BECAME APPARENT after removing the cowl. The AWOL primer line was found and connected, but so much time had gone by that the decision was made to forgo the flight for another day. With the cowling back in place and the plane in the hangar, one of the owners moved the prop into the best position to avoid damage by the movement of planes in the community hangar. The movement was no more than a few inches of arc, but they were critical inches…

VROOM! THE 140s ENGINE ROARED INTO LIFE! The startled owner — the one who had just moved the prop — fell backwards, thankfully, away from the now running plane as it carried 30 or 40% power. The 140 started to move forward … with only the V35B Bonanza in its path.

THE PROP OF THE 140 MADE FAST WORK OF THE SIDE OF THE BONANZA as it cut into the aluminum. Pieces of the Bonanza went flying in all directions, getting stuck in the ceiling and walls of the hangar. Finally, the second owner was able to shut down the engine and bring an end to the carnage.

IN THE AFTERMATH, it was found that the magneto switches had been left ON and the throttle in a starting position after the starts had proved unsuccessful. With the primer connected, some fuel flowed into the cylinder. The prop had been in the perfect place, as the owner moved it slightly forward to avoid hitting another plane, he moved the magneto just enough to fire the impulse coupling. The combination of fuel and a spark started the engine, and the ensuing destruction.

BOTH PLANES TOOK A BEATING IN THIS EVENT — The Cessna 140 prop was mangled by its work on the Bonanza, and the Bonanza had a gaping hole chewed into its side. Believe it or not, both were eventually repaired and returned to service.

THIS DIDN’T NEED TO HAPPEN. When you have problems with your airplane on the ground, always place the plane in a safe and stable condition before you take any further actions. Had our pilots closed the throttle and verified that the magneto switches were off, this event would likely not have taken the course it did.

ALWAYS CONSIDER THE PROP HOT — While our owner got lucky and fell away from the prop, he could have just as easily fallen in to the spinning blades, and been chopped into cat food in no time flat.

Inside Information: The only SAFE WAY to move a prop is BACKWARDS, since a loose or broken P-lead can cause the magnetos on the engine to be hot at any time.

NOTE: Some owners are afraid they will damage their vacuum pump by turning their prop (and engine) backwards. The choice here is to risk your life and save your vacuum pump – which is no choice – Your Life Wins.

BOTTOM LINE: By using your head, you should be able to avoid any “Pac-Man” like situations with the airplanes you fly. In the end, your insurance carrier and fellow aircraft owners will probably never appreciate your courtesy and attention to safety, but your adrenal gland and heart will!