Date: 201501
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Cruise
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Exhaust Manifold
Reporter organization: FBO
Reporter function: Instructor
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Flight Instructor
Human factors: Distraction
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: My student and I had just completed practicing engine failure procedures during a simulated engine failure northeast of our home airport. While climbing out at the end of the practice procedure; at around 500 AGL; I was talking to the student about ELT operations when I noticed the indicator on our portable carbon monoxide detector was indicating the presence of carbon monoxide inside the cabin. I told my student 'We might have carbon monoxide in here;' and my student immediately replied he was feeling lightheaded. I immediately turned off our cabin heat and window defroster; which had been turned on to a low setting at the beginning of the flight; and instructed the student to open his window. I resumed control of the aircraft. At around 2;000 feet MSL I began to experience lightheadedness as well; which subsided after about a minute thanks to the fresh air coming through the window. We were 10 miles northeast of ZZZ at this time; inbound towards the airport; so I increased power to maintain best forward airspeed; listened to the ZZZ ATIS; and then called ZZZ ATCT. I advised the controller that we had a possible carbon monoxide issue inside the aircraft. The controller provided us with our pattern entry instructions and asked if we would like equipment standing by; to which I responded negative. By this time the student and I felt normal again; so I offered him the controls again; and he resumed control. When on the midfield right downwind to RWY 5 at ZZZ; I again began experiencing some intermittent lightheadedness; as did he. I resumed control of the airplane and kept us fairly close to the runway so that we didn't spend more time than we needed to in the air. Upon landing; I immediately opened the cabin door to allow more fresh air inside the cabin; and both the student and I experienced relief once again. In retrospect it would have been a good idea to have a medic meet us at the ramp. I had not expected our symptoms to return after my student and I initially started feeling better. I am grateful to my company for installing the portable carbon monoxide detectors; as they aid in detecting potential carbon monoxide prior to the onset of severe physiological symptoms. My symptoms and those of my student were not severe enough to prevent us from maintaining control of the aircraft.

Callback: Reporter stated he was flying a Piper PA-28 Warrior with the standard Lycoming O-320-A engine. The aircraft had a stock heater; not an add-on or combustion type heater. There is a tab; a small handle for selecting defrost and cabin heat; but no fan. A tube with a small flapper controls the heat coming from the engine. Reporter stated their Chief Instructor informed him that Maintenance had done extensive troubleshooting and could not locate any cracks in the engine's exhaust manifold system. Two test flights were also performed; trying to find any indication of carbon monoxide or a possible source. Their Maintenance technicians are very professional; but were somewhat frustrated in not finding the cause for the carbon monoxide. He has since flown the same aircraft 8-10 hours a week and has not experienced any further carbon monoxide poisoning. He again noted the benefits of the portable carbon monoxide detectors for alerting flight crews to a serious hazard.



Synopsis: A flight instructor reports about the benefits of having a portable carbon monoxide detector that alerted them to the presence of carbon monoxide in the cabin of their Piper PA-28 Warrior aircraft. A feeling of intermittent lightheadedness was experienced twice prior to landing.