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Electronic Warfare and Radar Systems Engineering Handbook - EMP / Aircraft Dimensions -

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 ½ 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   AttackB   BomberC   CargoE   Electronic Surveillance F   FighterH   Helicopter K   Tanker O   ObservationP   PatrolQ  Special missionR   ReconnaissanceS   Anti Sub/Ship T   TrainerU   UtilityV   Vertical or Short Takeoff     and Landing (V/STOL)X   ExperimentalY   Prototype

Figure 1. EMP as a Function of Frequency

Table 1. AIRCRAFT DIMENSIONS AND EQUIVALENT ANTENNA APERTURE