During walkaround inspection, coloration can be observed on A320neo LEAP-1A pylon AFT pylon fairing lateral panel on INB and OUTB side.
Two types of colorations are observed:
Black residue:
The black residue is composed by particle of fuel combustion. This “pollution” is due to a circulation of gas from the engine exhaust to inside and outside the AFT Pylon Fairing.
Metal coloration (Iridescence):
This coloration is an oxidation of the external surface of the parts due to high temperature of the gas from engine exhaust.
This coloration could be reported after black residue removal (cleaning).
Following thermodynamic investigation, it was observed that the lower area of the external surface of the APF lateral panels is covered by a limited volume of engine exhaust gas due to pressure gradients between exhaust nozzle and APF lateral panels.
This high temperature exposure develops a fine thickness of oxidation on the external surface of the APF lateral panels and the exhaust nozzle.
An additional suction effect generated by negative steps of IFS (inner fixed structure of thrust reverser) to Pylon interface leads to a circulation of engine exhaust gas between the APF lower surface and the exhaust nozzle.
There is no airworthiness effect on aircraft due to this, and Airbus says, it can be left un-attended.
Author – Sushant Singh
