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 1/2 wavelength antenna at approximately 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 :

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/, where 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 and Landing (V/STOL)
E	Electronic Surveillance		Q	Special mission		X	Experimental
F	Fighter		R	Reconnaissance		Y	Prototype
H	Helicopter		S	Anti Sub/Ship

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                     Naval Air Warfare Center Weapons Division
                        Code 454110E - Attn: Scott Hanssen
                             Point Mugu, CA, 93042
                             Phone (805) 989-4792
                         E-mail: HanssenJS@navair.navy.mil