Propellers are unsung mechanical heroes of GA. Jets are wonderful, but for those of us who pay our own expenses chances are good that a prop is the driving force. Few such high performance items on an aircraft perform so reliably with so little attention. Even when abused they often perform beyond the call of duty—but then perhaps a Darwin Award is in the offing.
A young CFI was asked to drop the owner of a fixed-gear Cherokee off at his destination and fly back solo. On preflight he noted that the owner had invested in a Q-tip prop, the kind that is bent back at the tip about an inch to improve performance and reduce noise.
Shortly after takeoff it became apparent that this particular engine, prop, and airframe arrangement was not quite optimal. The best climb they could get was about 100 feet per minute despite being far from the aircraft service ceiling. Being on an IFR flight plan, ATC was not happy.
Upon landing, the CFI asked the owner about lack of performance—this was the slowest climbing airplane he’d ever seen. Then came the admission about a really hard landing—somewhat on the nose wheel—but not to worry, everything seemed to be in order. The CFI flew the aircraft back to the departure point under VFR. Seems the Q-tip “configuration” came about as a result of the nose-first landing. How the gear didn’t collapse or the firewall avoided buckling is anyone’s guess. Later, the CFI admitted that it probably wasn’t the smartest thing he’d ever done.
Another instructor, whom I know really well, was asked to give an instrument proficiency check to a Beech Sierra owner. The CFI, having not flown the aircraft before, gave it a very thorough preflight and noted a significant ding in the prop about four inches from the tip. It had been dressed out and was smooth in all facets. The owner said the aircraft had been through several annual inspections and that there had been no problem whatsoever.
The IPC went smoothly, but on the owner’s very next flight with his wife aboard, the prop tip separated and they had to set down in a corn field. The aircraft was written off. Fortunately, there were only minor injuries. It could have been a lot worse. To this day, I should have listened to that inner voice that said, “Wait a minute…this doesn’t feel right!,” and rejected the aircraft. Whether it would have made a difference to the owner is open for discussion.
When a prop tip separates the rotational forces instantly become more unbalanced than the Federal budget. We’re talking literally tons of force. If the engine is not shut down immediately there is a very good chance that it will break the mounts and quite possibly depart the aircraft.”Losing an engine” takes on a whole new meaning. Devoid of engine and any sort of balance—well, you get the idea.
When pilots forget to put the gear down it sometimes results in a prop modification as shown on this Aerostar. The mishap was caught on video as the pilot landed gear up, but he aborted the landing and returned to home base. Rumor has it the aircraft was put up for sale immediately with the caveat of “some prop damage.” Q-tipping your own props is not an approved owner-performed maintenance procedure for obvious reasons.
At the risk of stating the obvious, any prop strike calls for a mandatory engine teardown and complete inspection. Crankshafts may suffer hidden damage and are often replaced rather than chance a catastrophic failure that may occur immediately or not for years. The risk just isn’t worth it.
To avoid the dings that caught my Sierra pilot, avoid run-ups anywhere there’s gravel or even sand. If the airport doesn’t do a good job of dealing with FOD ( foreign object debris) you may get FOD—Foreign Object Damage.
Rolling takeoffs aren’t a bad idea IF runway length allows it and there’s enough fuel on board to avoid unporting a tank. It’s less likely to abrade the prop tips. There’s always a trade off.
Periodic prop overhaul and balancing are more than just good ideas and they deserve just a little more respect. The Air Safety Institute has a great free online course that covers both engines and props.