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What is that CFE738 Ugly Engine Cabin Odor?

June 2024

Falcon-2000-CFE738.jpgWe recently received this question from an operator out of South America about unpleasant cabin odors.


Our crew aboard a Falcon 2000 has reported an ugly odor in the cabin on the last three or four flights during start, climb, and descent. I’m having trouble isolating the source of this odor.

Any suggestions?

Thank you

DOM, South America

Here is our answer. 


Great question. 

You state the odor is noticeable during start-up, climb, and descent. This indicates the smell could be coming from the APU or either engine. Begin by troubleshooting the APU.

Check For An APU Compressor Seal Leak

If the smell begins while the bleed air is on after starting the APU and before the engines are in operation, then the APU may be the cause. Perform a borescope inspection to see if the compressor seal is leaking. Another option is to disconnect the bleed duct from the 12 o'clock area of the APU plenum located just aft of the APU inlet. Use a flashlight and look for evidence of oil or oil coking. If you find oil, this would contaminate the bleed ducts, and an ugly odor would be evident when the engines are operating. If no oil is found from the APU, troubleshoot the engines.

Check For Engine Carbon Seal Leaks

Cabin air comes from the LP system of the engine. Visually inspect both engine fan rotor blades for evidence of oil where the fan blade and fan disc connect. There could be oil on the aft side of the fan blades if the #1 carbon seal is leaking. The #3 carbon seal could also be leaking. Inspect behind the fan rotor assembly and look for evidence of oil wetting at the 6 o'clock position of the fan bypass stator vanes, possibly oil puddled at the bottom of the fan bypass stator vanes. If the #3 carbon seal is leaking, oil would usually be evident right after engine shutdown. Both the #1 and #3 carbon seals, if leaking, would allow oil to be present in the compressor section and would flow through the LP bleed air system.

Isolate The Bleed Systems

Another check to isolate the smell is to shut down one bleed system at a time during different flight conditions. For a couple of minutes each, alternate the passenger or crew air conditioning off to determine which engine could be producing the smell. Do this check during the climb, cruise, and descent conditions.

Reach out to Duncan Aviation

If for some reason the odor persists, feel free to reach out to our technical experts to help you trouble shoot. Or you can bring the aircraft in! We can work on finding the problem in one of our three US full-service locations. Start the process by getting a quote.