The Straight Dope

Cecil, you are my hero. My ultimate goal in life is to be the polymath you are. My question concerns a mythical "chicken gun" used for testing jet engines. I have heard tales of store-bought poultry being shot out of a gun at 500 mph into a running jet engine to test the engine's mettle should a pigeon or some other fowl have the misfortune to cross paths with a 747. Does this gun exist, and if so, how does it shoot a roasting hen at that speed without said bird disintegrating? -- Nora Patric, via AOL

One problem with researching this question is that everyone thinks he has to tell you the chicken joke. Seems the French borrowed the chicken gun from an American aircraft company to test the windshields of their high-speed trains. After the first test, they called the aircraft engineers and said, "Sacrebleu, ze chicken destroy ze windshield and dent ze back wall! What gives?" Having asked a few questions, the engineers replied, "Next time let the chicken thaw first." Talked to two different guys who swore this really happened. Bet they believe in the $250 Mrs. Field's cookie recipe, too.

One of the main users of the chicken gun (also known as the chicken cannon or turkey gun) is Pratt & Whitney, the jet engine manufacturer. The "chicken ingestion test," as it's called, is one of a series of stress tests required by the Federal Aviation Administration before a new engine design can be certified. The tests take place in a concrete building large enough to enclose an entire jet engine. With the engine operating at full speed, the cannon uses compressed air to shoot chicken (or sometimes duck or turkey) carcasses into the turbine at 180 (not 500) mph. This is the approximate speed a plane would be traveling if it encountered a bird during takeoff or landing, when most such incidents occur. The chickens are bought not from the corner grocery but from a game farm; the engineers apparently figure that for maximum realism they'd better use birds with feathers. Bird disintegration occurs only after the chick hits the fan. If the turbine disintegrates too, or if the engine can't be operated safely for another twenty minutes after impact, the design fails the test.

Other stress tests involve water and ice. The most pyrotechnic test of all requires that dynamite charges be strapped to the turbine blades and detonated while the engine is going full blast. (Needless to say this is the last test of the day.) If the exploding turbine blades aren't completely contained by the fan case, it's back to the drawing board. Better to have pieces of turbine embedded in the concrete walls of the test building than in some poor passenger's skull.

Less Filling, Lose Weight
This letter is in response to the guy who thinks one can stay thin by drinking beer [October 3]. It's true that if a person were to drink, say, 100 grams of beer at approximately 32 degrees Fahrenheit (0 degrees Celsius), it would take about 3600 calories to bring it up to body temperature. Unfortunately what the U.S. mistakenly calls a calorie, i.e., the unit of food energy, is actually a kilocalorie, or 1000 calories. So warming up 100 grams of cold beer in a human body takes only 3.6 kcal, which isn't going to compensate for the 150 kcal of Bud Light. -- Dr. John Hoekstra, Osaka National Research Institute, Japan

Got a pile of mail about this, including notes from a couple of knuckleheads who thought Cecil didn't know the difference between food calories (kilocalories) and calorie calories. Come on, that's one of the few things from tenth-grade health class I remember. (The "miracle of childbirth" film also made an indelible impression.) Somewhat disconcerting was the fact that, while everyone grasped the nub of the answer -- i.e., Mister Beer Lover's calorie calculations were off by a factor of 1000 -- everybody who tried to figure out how many calories you would burn off came up with a different number. The correct answer, based on 110 kilocalories per 355-milliliter (12-ounce) can of ice-cold (0 degrees Celsius) Bud Light: 13 kilocalories.

But there is a way to stay thin drinking beer. Just wash down that Bud with 2620 milliliters (not quite three quarts) of ice water. Not only would warming up the ice water burn off the rest of the beer calories, but you might lose the calories from lunch, too.

Is there something you need to get straight? Cecil Adams can deliver the Straight Dope on any topic. Write Cecil Adams at the Chicago Reader, 11 E. Illinois, Chicago, IL 60611; e-mail him at cecil@chireader.com; or visit the Straight Dope area at America Online, keyword: Straight Dope.

 
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