Why You Should Always Carry a Knife in an Airplane

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When I saw these photos–kindly sent to me by long-time reader Art Friedman–I immediately thought what a great real-world example they would be to illustrate Charles Law for a high school physics class. Or is it Boyle’s Law? Maybe both.

It’s also a grim reminder of the value of always having a knife near at hand in the airplane, especially if you’re carrying a life raft. They’ve been known to go awry from time to time. After Art sent the photos, I tracked down the owner of the airplane, David Pflum of Roscommon, Michigan. The incident occurred on Labor Day, when Pflum, who’s in the Coast Guard Auxiliary, was asked to transport a raft back from Waukegan, Illinois to the Traverse City, Michigan CG station because one of the helos didn’t need it.

“Just as we were about ready to close the door, we had it all loaded, it went off. It inflated and it had no place to go so it was out the side of my airplane,” Pflum told me. And that’s no little four-man raft, either. Pflum said he wasn’t certain of the size, but it’s the sort of raft tossed out by the Coasties when a ship or ferry is in extremis. He thought bigger than a 20-man, but less than a 50-man. The inflation cylinder is a little smaller than a scuba tank. That’s a lot of volume.

And obviously, all that CO2 did a lot of damage in its quest for equilibrium. It took the Cherokee’s baggage door right off its hinges and peeled back a section of the cabin roof like a sardine can. It did not, however, impinge into the cockpit area leading Pflum and I to wonder if the airplane would have been flyable if this had occurred in flight. My guess is it would have been, although it would have been no fun trying to land it. The larger danger is a raft on the backseat or co-pilot seat impinging on the controls during an unintended inflation, forcing an uncommanded and maybe unrecoverable pitch down. Thus the advisability of having a knife handy. In a pinch, a suitably adrenalized pilot could probably use a pen to deflate a raft, but a knife is preferable.

Spontaneous inflations of rafts aren’t everyday events, but they’re far from unknown, either. Pflum told me the Coast Guard has had these rafts self-inflate before and their new policy is that they can’t be shipped without the inflation mechanism being removed. Many inflations are due to an accidental snag of the lanyard, but that wasn’t the case here. The lanyard was stowed and the inflator appeared intact, not intentionally pierced.

As I’ve probably mentioned before, when I carry a raft, I wear my helicopter lifevest with a strobe, radio, dye and a knife in one of the pockets, with just this eventuality in mind. Compressed gas is nothing to trifle with. I once armed myself with two knives, one in the vest and one in my pants pocket. That’s was because I was carrying 14 rafts, I think, ferrying them between Grand Cayman and Key West when we were organizing the Cayman Caravan. I don’t think rafts are subject to chain reaction, but I figured even if spontaneous inflation is a long shot, I was tempting fate. (Fate actually bit. South of Havana in a convective rain shower, the Mooney’s door popped open in turbulence and I couldn’t get it shut on account of rafts being in the way. I landed in Havana to sort that out, much to the consternation of pre-911 U.S. Customs.)

Pflum had a happier experience with the government. Because he was on a USCG mission, the government’s insurance will pay for the repairs. So this turns out to be a relatively cheap lesson from which we can all benefit.

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