Minutes of the hearing of Professor Scholz on the operation of air conditioning in aircaft cabins and the associated air quality

Abstract

Aim: This hearing is to gather some information on: How ventilation/air conditioning/filtration works in aircraft, the regulation of ventilation/air conditioning/filtration, the incidents from the air system in aircraft called "fume events", the factors influencing the chemical contamination of the cabins according to the phases and operating modes of flights, the perspectives with the solutions which might be under study or testing.

Findings: The air from the outside goes in the engine core, then it is compressed and at the end, the bleed air is taken. In the bearing, the oil is supposed to stay in the wet cavity, but oil can also be in the dry cavity, since a drain is foreseen. Engines leak small amounts of oil by design. Having metal nano-particles in the oil is normal. Metal particles go to the bleed air. It was found that these metal particles can be in the human fatty tissue of aviation employees. The bleed air is also used to pressurize the potable water. The bleed air can contaminate the water. The last water extracted from the tank before it is empty is black, probably from engine oil residue. Evidence of contamination as seen in the ducts (observed on old parts of planes collected at dismantling sites): Brown or black stains (probably from oil) in the bleed air duct vs the clean fan air duct (with fan air coming from the engine bypass). The inlet of the water extractor is covered with black oily residue. The inside of air distribution duct in the cabin is black from contaminated bleed. Flow limiters clogged from pyrolysed oil in ducts of the air conditioning system. Black residues, which is not only dust, on top of overhead bins. Oily black soft substance covering the face of the recirculation fan.