What was that noise?
Aircraft and plastic do not mix
By Dr. James Hernandez
It was a wonderful day to fly in Long Island, New York. I reached out to my instructor and scheduled a flight in the early afternoon. I was a couple of flights before checkride in a Robinson R22. At this point, I was just polishing maneuvers.
What happened
I checked the METARs and TAF earlier and both stated promising weather conditions. But by the time I got to the school, the METAR showed winds from 120 degrees at 13 gusting to 19 knots. We decided to go ahead with the flight but to keep it inside the airport’s airspace. Apparently, everybody had the same idea and the pattern was crowded. The tower was busy. We started the flight with normal procedures and worked our way through the practical test tasks.
The weather turned on us with greater winds and a significant drop in temperature. We decided to hover-taxi back to the hangar from a designated area in the middle of the airport runways, called the SOD (training area). We noted a lot of debris around the area. While waiting for clearance to taxi back to the hangar area, we discussed the flight.
That’s when stuff hit the fan. Literally. As a student pilot you are trained in the recognition of certain sounds and vibrations. A low-frequency vibration will, most likely, indicate a main rotor system issue, whereas medium and high frequency vibrations will indicate an engine or tail rotor system issue. In half a heartbeat, the helicopter started to make a distinct sound with accompanying vibrations. These were in no way comparable to the sounds I was trained to recognize, not to mention the vibrations that were not within the scope of my training.
Something was not right. It was one of those moments when you and your instructor look at each other wondering first, what was that? and next, what did you do? We could hear and feel the main rotor system being off balance. We told tower we needed to shut down and inspect the rotor system. After the rotor stopped, my instructor went outside to check. He came back with a piece of what remained of a black plastic bag, no bigger than two square inches, that was on the leading edge of one of the rotor blades
That is all it takes to throw the whole system out of sync. The sound and the vibrations were enough to rock the whole airframe and rattle both of us.
While debriefing we discussed the mishap. We had noted debris at the SOD but did not think much of it at the time because these were very small pieces of trash. We never expected one whole black plastic bag to be sucked into the rotor system. We fared better than the plastic bag where only two square inches of it survived. However, this happened at the airport while hovering three feet above ground. I can only imagine what would have happened if this had taken place at altitude. At Islip MacArthur Airport (ISP) we are always vigilant about birds because of our proximity to the ocean and the variety of species flying in close to the airport. Now I will be looking out for flying debris as well.
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