Caravan 208B
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
General None Reported / Taken
Aircraft
Prior to aircraft loading I performed a Cold Weather preflight including ground test of the TKS system. Ground temp at Ramp departure was +02C with a ceiling of 600 ft overcast. I departed the Ramp with the aircraft's cargo compartment completely full from floor to ceiling. I turned the TKS system ON Hi during my taxi to the departure runway so that the wing would be 'wetted' prior to entering the clouds after takeoff. After takeoff while climbing to 5000 ft MSL with the TKS system now ON Normal I turned on the Cabin Heat /Defrost and immediately smelled the telltale TKS alcohol odor. Wanting to avoid the throat and eye irritation that I have experienced in the past from TKS fumes in the cockpit I promptly turned OFF the cabin heat while leaving the TKS system ON until I topped the cloud layer. After exiting the clouds I turned the TKS system OFF and tried the cabin heat again. Once again; I immediately smelled the alcohol smell. When I turned OFF the cabin heat the alcohol odor was no longer present. To avoid breathing the TKS fumes while using the cabin heat I donned my mask and breathed O2 for the next 30 minutes until the alcohol smell was no longer detectable with cabin heat. TKS system total AM run time with ground test plus taxi out to topping the cloud layer was less than 10 minutes. It is my opinion that TKS fluid mist shed by the prop slinger was being drawn into the cockpit from the air stream surrounding the aircraft nacelle via the aircraft bleed air system. I believe that the fact that the alcohol odor in the cockpit dissipated each time that I turned the cabin heat OFF while the TKS system was in use and later; after the TKS system had been turned OFF; until the prop slinger supply lines had sufficiently drained down in flight supports my position. This episode is a reminder of the necessity for pilots to have available and; when needed; to use supplemental O2 any time that the TKS system is used in flight when the Cabin Heat/Defrost is also used. This action will minimize the potential for pilot physical symptoms and/or possible mental impairment. As of yet there is no effective way to prevent TKS fumes from entering the cockpit under this and similar flight in icing scenarios.
Cessna Caravan pilot reported TKS fumes in the cockpit inhibiting the use of the cabin heater unless the oxygen mask is used.