Air conditioning: Preventing ram air leakage at the mating surfaces of the dual heat exchanger, precooler, and ram air regulating valve
Effectivity: Challenger 300/350/3500 aircraft
ATA: 21
By: Costantino Raspa (CSE) Some operators have reported air leakage in various areas of the ram air passages, particularly at the mating flange surfaces of the dual heat exchanger, precooler, and ram air regulating valve, as highlighted in yellow in the illustration below:
In certain cases, the leakage was severe enough to trigger a bleed leak message due to hot air escaping and impinging on the bleed leak detection element.
Corrective action is now available on the Bombardier Portal. Operators can access the in-service modification by selecting Engineering Documents and searching for IS100-21-0003. This modification allows the application of a self-contouring silicone gasket at the following locations:
Both mating surfaces of the Precooler P/N 3737A020000 where it attaches to the Inlet Header P/N 1556A010000 and Outlet Header P/N 1558A010000.
Both mating surfaces of the Dual Heat Exchanger P/N GG670-95008-3 where it attaches to the Lower Ram Intake P/N 9773B010000 and the Plenum P/N GG431-2008-5.
The mating surfaces of the Ram Air Regulating Valve P/N 7084A010000 where it attaches to the Inlet Header P/N 1556A010000.
Improving the installation at the mating surfaces identified in areas (1), (2) and (3) will help to improve ram air cooling efficiency, as there will be minimal to no air loss escaping through the mating surfaces. This will eliminate bleed leak messages mitigating aircraft dispatchability.