Summary
We propose to adopt a new airworthiness directive (AD) for all McDonnell Douglas Model MD-90-30 airplanes. This proposed AD would require installing new fire handle shutoff system wiring. This proposed AD was prompted by a possible latent failure in the fire handle shutoff relay circuit due to a lack of separation between engine wires. We are proposing this AD to minimize the possibility of a multiple engine shutdown due to single fire handle activation.