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Carbon Monoxide

Carbon Monoxide (CO) is an ever-present risk for all light aircraft. A number of Bearhawk builders have reported difficulty in preventing CO from entering the cabin. All aircraft are required to carry an approved CO monitor. Many install a simple "card" type indicator to comply with this regulation.

The following points have been observed by a number of builders:

  1. Having an air outlet at the rear of the cabin to allow fresh airflow may actually draw CO into the front of the cabin.

  2. Keeping the exhaust pipes tucked in close to the fuselage (to minimize drag) in some cases increased CO readings.

  3. A number of builders reported that CO was more prevalent during a climb or at higher AOA.

  4. When operating Lean of Peak (LOP) there is little or no CO emission, so it can give a false negative reading when testing for the presence of CO.

  5. Lowering the exhaust pipes away from the fuselage in a number of cases resolved the issue completely.

  6. Some builders reported that the installation of turned down exhaust tips also improved or resolved the issue.

  7. In addition to the regulatory CO indicator, many builders have installed an RV type CO alarm. These are relatively inexpensive, and provide a loud audible alarm when limits are exceeded. Many of them also display the CO level in PPM (parts per million) and can be very helpful during Phase One flying.


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