By Kevin Price, EAA Lifetime 1476265
Last year I had a close call with carbon monoxide (CO) on a flight from Chattanooga, Tennessee to Xenia, Ohio. We had recently installed a new exhaust pipe on our airplane and it broke during this flight at the flange weld. The exhaust pipe remained aligned with the engine cylinder exhaust port and as a result there was no noticeable change in the engine noise.
Even though our aircraft is a pusher with the engine in the rear, a very dangerous CO level of 400 parts per million (ppm) developed and made its way into the cockpit within 10 minutes after takeoff. That level can result in incapacitation in 1 to 2 hours; I was on a planned 2-hour flight. I think the level would have increased to much greater than 400 ppm which would have meant I had perhaps only a few minutes of useful consciousness remaining. A fire could also have resulted from the hot exhaust gas leaking into the engine compartment, so the CO alert may have helped prevent more than one serious problem.
Well, the good news is that I was flying with an electronic CO detector — a Sentry ADS-B device paired with ForeFlight. I got an alert of 75 ppm which I at first questioned. How could I have CO in a pusher?
I also had a Forensics portable CO detector with me that I had just bought at EAA AirVenture. When I pulled it out, it was in full alert mode: the red light was flashing and the digital readout was showing a CO level of 400 ppm! I recognized I was faced with a very serious emergency and landed uneventfully shortly afterward at the nearest airport.
I learned a few things from this:
1) ALL aircraft powered by an internal combustion engine are susceptible to CO — even pushers.
2) Aviation risk from CO is not just associated with cockpit heat usage; and
3) Fly with a CO detector (or two) — always!
I strongly recommend you use an electronic CO detector versus the plastic ones with the center dot that changes to a dark color in the presence of CO. Electronic CO detectors are quite affordable and offer better and more noticeable alerts through the use of flashing lights, digital readouts, and audible annunciations Portable electronic CO detectors such as the Forensics unit I make it easy to take along with you in any aircraft you fly. (I use Velcro to attach mine in the various aircraft I fly as a CFI.) It is important that you place an electronic CO detector in a prominent location where you will easily be able to note the digital readout and/or flashing lights. Do not rely solely on an audible alert as cockpit noise combined with ANR headsets can make the beeps impossible to hear.
NOTE: Some CO can be expected during ground ops and slow flight. As a reference, new aircraft can be certified with a CO level of 50 ppm per (CFR) 23.831) . If the level goes above 50 ppm and remains there or increases, you’ll want to pay attention to that and take appropriate action. See the table below.