Caravan 208B
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Situational Awareness; Physiological - Other; Troubleshooting; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action; General Physical Injury / Incapacitation
Human Factors; Environment - Non Weather Related; Company Policy; Aircraft; Procedure; Weather
While in flight with the TKS system operating in HI mode in icing for approximately 15 minutes during cruise flight and instrument approach and again after blocking in; I experienced separate sustained coughing events ('coughing fits') that led to my seeking treatment at the local hospital walk in clinic/ER for my symptoms. These symptoms included throat irritation; a burning sensation in my chest and an overall feeling of fatigue in addition to uncontrollable coughing.In response to the onset of coughing while in flight I immediately donned my personal O2 mask and began breathing 100% O2; noting that the coughing subsided quickly thereafter and did not further interfere with my flying the remainder of the flight. Prior to my 'coughing fit' I did not note the TKS alcohol smell in the cockpit with the TKS system operating in HI mode and with the cabin heat turned OFF. I did; however; smell alcohol after donning my personal O2 mask after I later turned ON the cockpit heat/defroster system while the TKS system was still operating during times when I needed to adjust my O2 mask away from my face in order communicate with ATC using my head set boom mic. After landing while securing my wet plane at the ramp with TKS fluid running off/draining to the ramp from it my coughing once again became uncontrollable. In response; I immediately donned the paint vapor mask that I use for all pre/post-flight activities outside of my plane during icing season whenever the TKS system must be ground-tested and/or the panels purged. Once wearing the vapor mask on the ramp my coughing gradually subsided; but not as quickly as it had from my breathing 100% O2 while in flight. After closing out the flight legs with Dispatch I informed the dispatcher of my condition and my intention to seek medical treatment then left the airport for the hospital clinic.At the hospital the attending MD interviewed me about my experience and my symptoms; listened to my lungs and diagnosed me as having 'chemical bronchitis'. The MD explained that the only treatment action to be taken was to have me continue to breathe fresh air away from the chemical fumes source (per the MSDS for the TKS fluid; a copy of which I provided to the ER staff). He also stated his concern that my lungs were very congested and prescribed a 6-day protocol of Prednisone to alleviate the inflammation. He then released me back to duty and told me that I was good to fly the PM legs back if I felt comfortable doing that. I assured him that I did then left the hospital early afternoon and contacted Dispatch with an update to my situation. I told the dispatcher that I felt good to fly the PM flight legs and that I planned to breathe O2 my entire time in flight back whether or not I used the TKS and/or cabin heat defrost systems. I also informed the dispatcher that after consulting with the Medical Certification Office about the implications of my flying with the Prednisone prescription; I would begin the protocol [for 6 days]; with my prescription levels being low enough by [in 5 days] for me to legally fly that day. The PM flight legs back were flown without incident with my being especially careful to wear the paint vapor face mask at all times when working outside the plane as well as my personal O2 mask while in the cockpit from engine start to engine shut down. While breathing 100% O2 with my personal mask during the PM flight legs I noted no adverse effects from TKS fumes even though I used the TKS system in HI mode on the flight leg for one leg and used the cabin heat/defrost system intermittently during both legs. As it was forecast to be an above-freezing night and I did not want to further expose myself to TKS fumes while securing my plane after blocking in at the ramp I did not perform the post-landing purge of the TKS panels/ops check of the system that pilots have been requested to perform on nights when the temperatures are forecast to be below freezing.This latest event isthe 5th such major fumes episode that I have experienced in the years that I have been operating TKS-equipped Caravans in icing conditions and my most severe to date. Three and a half years ago during my first fumes/vapors exposure episode I unknowingly breathed in TKS fluid fumes and raw fluid spray entering directly into the cockpit from behind the aircraft's instrument panel glare shield due to a faulty windshield spray bar installation. This episode was followed by 3 successive major cockpit fumes exposure events while flying during that caused symptoms similar to those that I experienced on this date. In addition; I have experienced numerous; subsequent less-serious fumes episodes since in the past three years while operating the TKS-equipped aircraft. As a result of my continued exposure to the TKS fluid's chemical vapors; I feel that I have developed a level of sensitivity to the fumes that has required me to continually escalate my efforts to protect myself from their effects. In addition; I have observed that my voice now sounds raspy when I talk (a symptom regularly reported by pilots suffering effects from the fumes); when this had not been the case previously and that my throat now constantly feels strained while I am engaged in normal-level talking.I flew in IMC during the flight legs for a total of 1.4 hours (out of 1.6 hrs flight time) and although I was in light icing conditions nearly the entire time I elected not to run the TKS system until necessary to prevent measurable ice buildup on the plane in order to preserve the amount of fluid on board and also to forestall my experiencing the negative effects of breathing the TKS fluid fumes. PLEASE NOTE: A point that is frequently overlooked when discussing the TKS system's operation; that is also contrary to what is published about it; is the fact that it will NOT keep ice from building up on the airframe/windshield even in light icing conditions UNLESS the system is run in HI mode for a significant length of time and the windshield spray bar is used regularly. From my years of experience flying with the TKS system on the Caravan; operating it for as much as 18 flight hours per week in all types of icing conditions during a 6 - 8 month icing season and from the experiences of our other pilots as well; it is my contention that operating the system in the NORMAL mode prior to entering icing conditions in order to 'wet' the plane down to forestall ice buildup on the airframe (as recommended in the literature) accomplishes little except to use up precious fluid prematurely. From my experience with the system I have observed that operating it in HI mode or greater is the only effective way to control ice accumulation on the airframe in any conditions greater than 'very light icing'. Unfortunately; operating the TKS system in HI mode also yields a maximum of 80 minutes fluid duration; assuming that the aircraft is operating with a fully filled TKS fluid tank and that the quantity gauge is reasonably calibrated to the actual 'full' fluid level in the tank. Consequently I; and all of the pilots that I know who fly with the TKS system in ice daily; cycle between running it in Normal and High modes as well as turning the system OFF entirely for extended periods of time even when in the ice (while monitoring ice buildup and IAS closely) in order to preserve fluid for an event(s) when it REALLY may be needed; such as when needing to keep the windshield clear enough of ice to allow the pilot to see a snow-covered runway through an ice-free patch of windshield as small as 4' X 6' in size on a night approach to minimums with a strong crosswind and blowing snow. In addition; after turning on the TKS system in flight a pilot does not know exactly how much fluid remains in the fluid tank at any given time UNLESS he/she tracks the running time in each mode at the different fluid flow rates and then does the mental math in order to determine fluid used/remaining while alsoflying single-pilot in IMC in the ice; communicating with ATC and preparing for a possible night approach to minimums. The narrative of the previous paragraph goes to the reason why the operation of the TKS system in HI mode (or greater) for extended periods of time while in icing conditions with its subsequent effect on the ground and cockpit environments is important to understand. With the system's much higher fluid flow rate in HI mode compared to that of the NORMAL mode the wing; lift strut; tail surface panels and especially the prop slinger; weep/throw off a much greater volume of fluid into the airstream surrounding the plane in flight. The spray from the prop slinger; in addition to coating parts of the airframe with fluid also sprays fluid into the airstream surrounding the engine cowl and air intake where a significant amount of fluid is sucked past the Inertial Bypass; and is ingested by the engine where it vaporizes and becomes part of the bleed air that is used for cockpit heating/windshield defrosting system of the plane. This dynamic has been confirmed through random cockpit air sampling; the in-flight experiences of pilots and from observations by FAA personnel conducting operations and maintenance checks. It is my contention that the higher the TKS fluid flow rate(mode) required in order to mitigate airframe ice build-up; the greater the potential for high concentrations of TKS fluid fumes/mist entering the cockpit via the heating/defrost system and/or through possibly poorly-sealed windshields; wing and fuselage fresh air vents. I believe that these factors could help to explain; in part; the sometimes wide variations in the severity of cockpit fumes events experienced by pilots flying the same aircraft.The effect of the HI mode (or greater) TKS fluid flow rate being in use for extended periods of time while in icing conditions also manifests itself in greater fluid weepage/fluid drain-down/dripping from all 'wetted' surfaces with the wing/tail surface panels and all system fluid lines being above the level of the fuselage lift-strut attachment points and the prop slinger (no check valves appear to be present in the fluid lines). Once shut down; an aircraft that has had its TKS system in operation for an extended period of time in HI or greater mode will drain/weep fluid to the ramp surfaces around it continuously often for up to 24 hours after the plane has flown. Large puddles of fluid collect on the ground beneath the prop slinger and the fuselage lift-strut attachment points. Fluid also runs off the wet fuselage; wing and tail surfaces while the weeping panels aid in painting the aircraft's outline on the ramp with drained fluid that also drips constantly onto maintenance/ramp personnel working under and around the fuselage; wings and tail. If a post-flight TKS panel purge is also performed due to anticipated forecast sub-freezing overnight temperatures the amount of residual fluid present on the ramp round the plane is much greater. The normal cold-weather AM pre-flight system ground test required for flight into known icing conditions further adds to the amount of puddled TKS fluid present on the ramp surfaces. Due the large volume of TKS fluid drained on the ramp from up to 7 planes during periods of high system usage necessitated by widespread sustained in-flight and ground icing conditions it is often possible to smell the tell-tale TKS alcohol odor when exiting the ramp office building for the parked aircraft at a distance of well over 100 feet. As a result of this high concentration of airborne fluid vapors in the ramp areas; I often begin to involuntarily cough from the fumes shortly after leaving the ramp office for the ramp and before proceeding any further towards the parked aircraft have to don the paint vapor mask that I wear while conducting the aircraft Cold WX pre-flight and TKS system checks in order to walk to my plane without discomfort. I have also noted that if I do not wear my v
A C208 pilot diagnosed with chemical bronchitis described in depth his method of dealing with TKS fluid vapor exposure during ground and flight operations.