AN INVESTIGATION OF EME AS A POTENTIAL CAUSE OF FUEL TANK IGNITION

Re-Distributed by http://www.tpub.com

AN INVESTIGATION OF EME AS A POTENTIAL CAUSE OF FUEL TANK

IGNITION

Jay J. Ely, Truong X. Nguyen, Kenneth L. Dudley, Stephen A. Scearce, Fred B. Beck, Manohar D.

Deshpande and C. R. Cockrell: NASA Langley Research Center, Hampton, Virginia

sources. The electromagnetic environment

surrounding TWA-800 was rather complex, and

Abstract

included numerous ground-based, shipboard, and

NASA researchers were tasked to study the

airborne radio frequency (RF) transmitters, some

potential for radio signals to excite an aircraft fuel

being classified by the military. As a result, the

quantity indication system (FQIS) enough to cause

Department of Defense (DoD) Joint Spectrum

arcing, sparking or excessive heating within a fuel

Center (JSC) was contracted to perform a detailed

tank. Computational techniques were used to

analysis of the TWA-800 electromagnetic

determine the threat from external high intensity

environment. Their report was published in January

radiated field (HIRF) transmitters nearby, like

1999, and incorporated into the NTSB TWA Flight

shipboard and airborne RADAR systems.

800 Public Hearing Exhibit Items as Exhibit 9A,

Experimental methods were used to determine the

Addendum 2 [2]. The JSC reported that all

threat from Portable Electronic Devices (PEDs)

dominant, external RF emitters were pulsed

carried aboard by passengers. To support this work,

sources, applying peak field intensities of up to 32.6

unique electromagnetic coupling measurements

V/m to the airspace of TWA-800.

were performed on a retired Boeing 747 aircraft,

and new test and analysis methods were developed

Alternatively, it can be demonstrated that a

that may be applied to other FQIS designs as well

portable radio transmitting about 5 W may generate

as other aircraft electronic systems.

field levels in excess of 100 V/m very close to its

antenna. When used inside an aircraft, portable

electronic devices (PEDs) can be placed within

Introduction

inches of aircraft wiring, and their emissions are not

On July 17, 1996, the Trans World Airlines

subject to airframe attenuation as are outside HIRF

Flight 800 (TWA-800) Boeing 747 Series 100 (B-

sources. NASA's Aviation Safety Reporting

747-100) aircraft exploded and crashed into the

System (ASRS) documents numerous occurrences

Atlantic Ocean. The flight had departed 14 minutes

of suspected PED interference with aircraft

earlier, traveling from New York's John F.

systems.

Kennedy airport to Paris. To date, it is believed that

Very little quantitative information is available

a fuel vapor ignition occurred in the center wing

regarding specific frequency-power-temperature-

fuel tank (CWT). The cause of this ignition is still

pressure combinations required for hazardous

unresolved.

conditions with aviation fuels. The DoD has

During the first year of the investigation, some

documented the threat to fuel and ordinance from

consideration had been applied to the possibility of

hand-held transmitters with output power

man-made electromagnetic interference as a factor

capabilities of as little as 1 W [3].

in the crash. Later, in April, 1998, a special

Because of the known volatile state of CWT

supplement entitled "The Fall of TWA 800: The

fuel vapor, the complex RF environment, and

Possibility of Electromagnetic Interference" was

minimal degree of RF shielding on the FQIS wiring

published in The New York Review of Books, by

of Classic Boeing 747-100 aircraft, the NTSB

Harvard professor Elaine Scarry [1]. This report,

decided to investigate the potential for man-made

along with continued dialog between Ms. Scarry

electromagnetic environment (EME) to cause the

and NTSB Chairman Jim Hall, prefaced an

TWA-800 fuel tank ignition.

increased desire to quantify the actual threat from

external high intensity radiated field (HIRF)