Re: Answer to Ed's Chaff Question

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Comments:: : Ed: You pose some very interesting questions in your post on the Mighty Eighth Message Board. : : : : 1. I was always wondering about the technique used to drop radar jamming devices during WW Was this done by the lead planes of the formations or smaller amounts by all ships ? : : Chaff (or Window if Brit or Duppel if German) was dropped in every conceivable fashion during the war, but it soon became apparent by mid 1943 that lead planes in a formation were the most effective at jamming gun laying radar. (Flak fell at the rate of 300 to 400 feet per second.) Lead elements of the lead groups would start dispensing Chaff about 30 minutes prior to Bombs Away (since that is where the heaviest concentrations of flak were encountered) and 30 minutes after Bombs Away. During D-Day, the 8th used B-17s to fly a circular route over the English Channel to dispense Chaff to confuse enemy radar operators from seeing the vast air armada heading to the Cotentin Peninsula. : : 2. Did chaff come in packages which burst open after they were ejected? : : Chaff came in bundles of 2,200. Initially, the 8th AF dispensed Chaff out of the waist windows, but modifications were soon made where chutes were added in the radio rooms and Chaff was then dispensed from there. See Roger Freeman’s Mighty Eighth War Manual for a good picture of a Chaff Chute and a somewhat thorough explanation of Chaff. : : 3. What was the reason that different types of chaff was used (very narrow tinsel with one side white and a much wider version with one side black, also a very fine wire type)? : : This from my first book: : : It had been known for years masses of metal foil strips cut to the proper size - preferably half the wavelength of the radar to be jammed - would swamp the enemy's receivers with false echoes. Window could have been introduced as early as the spring of 1942, but an initial decision to use it had been reversed when some warned the Germans in turn would use it to render Britain's defenses ineffectual. (In fact, the Germans were well aware of the effectiveness of Window, which they called Duppel, but withheld it for the same reason!) Harris was uninterested in pushing its use. During April 1943, the decision was reconsidered, but it was found the strips being produced were of the wrong size. The introduction of Window was delayed again until after the Allies landed in Sicily, when after a final argument, its use was authorized for the Battle of Hamburg. Bundles of 2,200 paper strips with aluminum foil on one side, each strip 26.5 centimeters long, designed to interfere with Wurzburg and Lichtenstein, were delivered to each bomber. Until automatic launchers were available, a man would have to hurl them out, one bundle a minute, for one hour before and one hour after bombing the target. Bomber Command also had another new countermeasure, Cigar, a jammer designed to interfere with enemy VHF transmissions to night fighters. In June, a more active measure against the enemy's defenses had been introduced: Serrate night fighter support. These Beaufighters carried both their own radar and a device called Serrate, which could home in on the Lichtenstein radar. But, the Beaufighters were too slow to deal with the German fighters, and their operations were not very successful.12 : : 4. Why were these dropped even in clear weather when altitude, number of aircraft and course were known to ground observers ? : : The Germans had interconnected radar with flak batteries – confuse the radar and flak would be ineffective – even on clear weather bombing missions. : : Electronics and electronic countermeasures are the least written about subjects from the air war and it is absolutely fascinating how quickly they evolved in a wartime economy. Every wonder how the microwave oven got it start? Ever hear of H2S or H2X? Yep, microwaves originated from radar sets used to bomb targets by PFF. : : I hope this helps. : : Kevin M. Pearson : : Vice President, Economic Development : : Wichita Falls Board of Commerce and Industry : : 900 8th Street, Suite 218 : : P.O. Box 1860 : : Wichita Falls, TX 76307 : : Phone: 940.723.2741 : : Cell: 940.782.6285 : : Fax: 940.723.8773 : : : : www.wichitafallscommerce.com : Ed ,Kevin. : There is one countermeasure that the tracking radar can use to see through the chaff-- to eliminate returns that are static (this technique is still used by ATC radars to eliminate ground obstructions)Chaff slows down pretty quickly (small mass, high drag0, so if chaff is to be effctive you have to continually dispense it.In modern combat aircraft this is done automatically using radar illumination sensor in the aircraft at risk

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