Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain BAE Systems (Operations) Limited Model BAe 146 and Avro 146-RJ series airplanes. This proposed AD would require modifying the auxiliary power unit (APU) exhaust duct in the environmental control system (ECS) bay; installing new, improved insulation on this APU exhaust duct; and replacing the existing drain pipe with a new exhaust drain pipe blank. This proposed AD is prompted by a determination that the temperature of the skin of the APU exhaust duct in the ECS bay is higher than the certificated maximum temperature for this area. We are proposing this AD to prevent the potential for ignition of fuel or hydraulic fluid, which could leak from pipes running through the ECS bay. Ignition of these flammable fluids could result in a fire in the ECS bay.