NTSB Incident Report on the Cessna 150 at Chesterfield, MO (CHI95IA030)

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NTSB Identification: CHI95IA030.
The docket is stored in the (offline) NTSBImaging System.

Incident occurred OCT-26-94 at CHESTERFIELD, MO
Aircraft: CESSNA 150, registration: N7XC
Injuries: 1 Minor.

THE STUDENT SOLO PILOT RETURNED FROM A CROSS COUNTRY FLIGHT COMPLAINING OF HEADACHE,NAUSEA, AND DIFFICULTY WALKING. THE PILOT STATED THAT SHE HAD SMELLED EXHAUST FUMES, WASNOT TAUGHT OF A POTENTIAL CONNECTION BETWEEN EXHAUST SMELLS AND CARBON MONOXIDE POISONING,AND CONTINUED THE FLIGHT. MEDICAL TESTS REVEALED ELEVATED CARBON MONOXIDE, WHICH REQUIRED5 1/2 HOURS OF 100% OXYGEN TO REDUCE TO NORMAL LEVELS. POST-FLIGHT INSPECTION REVEALED ACRACK IN THE REPAIRED MUFFLER WHICH HAD BEEN INSTALLED 18 HOURS EARLIER. THE PRIVATE PILOTPRACTICAL TEST STANDARDS REQUIRE THAT AN APPLICANT EXHIBIT KNOWLEDGE OF SYMPTOMS, EFFECTS,AND CORRECTIVE ACTIONS FOR CARBON MONOXIDE POISONING.

Probable Cause
the cracked heater exhaust muffler which resulted from an improper repair. Factors werethe physical impairment of the solo flight student as a result of her inadequate trainingconcerning carbon monoxide hazards.

On October 26, 1994, at 1800 central daylight time, a student pilot returned from asolo cross country in a Cessna 150, N7XC, operated as a 14 CFR Part 91 training flight byWeiss Aviation of Chesterfield, Missouri. The student complained she was nauseous, aboutto pass out, and had difficulty walking, but drove herself home. Four hours later, afterdiscovering an exhaust muffler crack (the repaired muffler had accumulated 18 hours inservice since installation), the operator contacted the student and recommended she obtainmedical attention. Medical testing revealed an elevated blood level of Carbon Monoxide(17.5%). After 5 1/2 hours of 100% Oxygen treatment, the CO concentration had reduced to1.5% and the pilot was released.

The pilot stated that she had smelled fumes during the flight, was not taught of apotential hazard or connection between the smell and Carbon Monoxide poisoning, andcontinued the flight.

AC-61-21A, the Federal Aviation Administration Flight Training Handbook, discusses thehazards of Carbon Monoxide poisoning and faulty heater systems as a cause. FAA-S-8081, thePrivate Pilot Practical Test Standards, requires under “Aeromedical Factors”that an applicant exhibits knowledge of symtoms, effects, and corrective action of carbonmonoxide poisoning.

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