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If the engine on airliners has for example, an oil leak, can the oil or other substances contaminate the air on the passenger cabin? How would this situation be avoided?

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    $\begingroup$ Traditionally, an engine failure means it stops spinning... not that it is working incorrectly. I believe the term for what you're describing is usually a malfunction. $\endgroup$ – abelenky Mar 25 '16 at 21:02
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    $\begingroup$ Just watched an NTSB program on tv the other day where a Cessna had an incorrectly installed exhaust system. The cockpit filled with carbon monoxide. The pilot became incapacitated and crashed $\endgroup$ – TomMcW Mar 25 '16 at 21:12
  • $\begingroup$ Or read this carbon monoxide incident - avweb.com/news/news/182437-1.html $\endgroup$ – DJohnM Mar 25 '16 at 21:36
  • $\begingroup$ So both of those examples are for smaller GA planes... is this question about those types, or airliners? $\endgroup$ – fooot Mar 25 '16 at 21:44
  • $\begingroup$ It can happen on airliners as well, yes. $\endgroup$ – Zach Lipton Mar 25 '16 at 21:45
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Yes, it is possible for contaminated air to enter the cabin. The air pressurization is provided by the "packs" (air conditioners), which are in turn powered by the bleed air (hot air extracted from low stages of the turbine) of the engine: enter image description here


To avoid the problem, bleed air is shut when engine trouble is confirmed or suspected. For example, the Engine Fire checklist for the Boeing 737 calls for:

  • [Autothrottle]...Disengage
  • [Thrust lever]...Confirm...Close
  • [Engine start lever]...Confirm...CUTOFF
  • ...
  • [ISOLATION VALVE]...CLOSE
  • [PACK switch]...OFF

With one engine out, the cabin air is provided by the bleed air of the other good engine. With a dual bleed shutoff (or failure), you better get down right away.

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Yes, an malfunction in a jet engine can cause contaminated air to reach the passenger cabin. It is a rare occurrence, but it does happen.

One of the most famous cases was British Midland Flight 92 on Jan 8th 1989 in Kegworth England.

Kegworth air disaster

"After taking off from Heathrow at 7:52 p.m., Flight BD 092 was climbing through 28,300 feet to reach its cruising altitude of 35,000 feet when a blade detached from the fan of the port (left) CFM International CFM56 engine. While the pilots did not know the source of the problem, a pounding noise was suddenly heard, accompanied by severe vibrations. In addition, smoke poured into the cabin through the ventilation system and a burning smell entered the plane".

In addition to contamination from engine failures, there is a much more public debate over contamination due to perceived weaknesses in the design of the aircraft cabin air systems. These weaknesses have not been positively identified but many believe it is due to faulty engine seals and/or air conditioning packs. There are numerous reports of pilots, flight attendants, and passengers feeling ill from "toxic air" on aircraft.

The name "Aerotoxic Syndrome" is also used to describe the problem of bad air in aircraft. More information here: Aerotoxic syndrome

Here is a website dedicated to Toxic Cabin Air. Toxic Cabin Air

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    $\begingroup$ Just an aside. The crew had recently transitioned to the 734 from previous "steam gauge" versions. On the aircraft they were familiar with, bleed air for the cabin was only taken from no 2 so the presence of smoke in the cabin added to their mistaken diagnosis that the problem was with that engine although the 734 takes cabin bleed from both engines. The second problem was that the vibration indication moved in the opposite sense to the steam gauge which reinforced the diagnosis and led to shutting down no 2. As usual, a lot of holes in the cheese lined up in that disaster. $\endgroup$ – Simon Apr 3 '16 at 19:28
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Jet engines on airliners take some relatively low pressure bleed air from the front stages of the compressor in order to feed compressed fresh air to the cabin and to power other items. This air is as fresh as the outdoor air.

Note that when a commercial airline starts engines on the ground at an airport with a significant tailwind then the engine can ingest some of its own exhaust and therefore upon occasion as a passenger you can smell the odor of kerosene.

If an engine is shut down in the air for some reason then no pressure is generated and other engines on the plane will supply the compressed air to the cabin.

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    $\begingroup$ It happens reasonably frequently. $\endgroup$ – Mark Mar 26 '16 at 0:45
  • $\begingroup$ The problem is more about lubricant or hydraulic fluid leaking and reaching high temperatures and then decomposed into toxic or carcinogenic elements. $\endgroup$ – mins Mar 26 '16 at 11:16
  • $\begingroup$ @Mark Thanks. I edited my answer to remove the last paragraph. $\endgroup$ – Craig K Mar 26 '16 at 16:58

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