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An aircraft flying in the vicinity of an electromagnetic pulse (EMP) acts like a receiving antenna and picks up EMP radiation in relation to size like a dipole (or half-wavelength dipole). | EMP AIRCRAFT DIMENSIONS An aircraft flying in the vicinity of an electromagnetic pulse EMP acts like a receiving antenna and picks up EMP radiation in relation to size like a dipole or half-wavelength dipole . The electromagnetic pulse spectrum decreases above 1 MHz as shown in Figure 1 so an F-14 aircraft that is an optimum A wavelength antenna at .8 MHz will pick up less EMP voltage than a B-52 or an aircraft with a trailing wire antenna. A rule of thumb for the voltage picked up is Vemp 8.1 volts ft times the maximum dimension of the aircraft in feet This rule of thumb was generated because a single linear relationship between voltage and aperture seemed to exist and compared favorably with more complex calculations for voltage picked up by various aircraft when subjected to EMP. Table 1 shows various aircraft and the frequencies they would be most susceptible to using f c 8 where 8 matches the selected aircraft dimension for maximum antenna reception effect . This should be a design consideration when trying to screen onboard avionics from the effects of EMP. The following is a partial listing of aircraft types vs identifying prefix letters several are used in Table 1 A Attack K Tanker T Trainer B Bomber O Observation U Utility C Cargo P Patrol V Vertical or Short Takeoff E Electronic Surveillance Q Special mission and Landing V STOL F Fighter R Reconnaissance X Experimental H Helicopter S Anti Sub Ship Y Prototype Frequenc Figure 1. EMP as a Function of Frequency 8-4.1 Table 1. AIRCRAFT DIMENSIONS AND EQUIVALENT ANTENNA APERTURE MISSION AIRCRAFT TYPE HEIGHT ft. FREQUENCY MHz LENGTH ft. FREQUENCY MHz WING SPAN ft. FREQUENCY MHz A f f 2 A f f 2 A f f 2 ATTACK A-6C 15.58 63.16 31.58 54.58 18.03 9.02 53.0 18.57 9.29 A-7E 16.00 61.50 30.75 46.07 21.36 10.68 38.73 25.41 12.71 A-10 14.66 67.05 33.52 53.33 18.43 9.21 57.5 17.1 8.55 ELECTRONIC EA-6B 16.50 59.64 29.82 59.34 16.58 8.29 53.0 18.57 9.29 WARFARE FIGHTER F-4J 16.3 60.37 30.19 58.2 16.91 8.46 38.4 25.63 12.82
