Carbon Monoxide in Cabin

M

moodyav

New member
I fly a 1973 8KCAB and noticed feeling bad after flying, my students also noticed feeling tired after flights in the airplane. I put in a CO detector and sure enough after about 30 minutes it had turned dark. I've re-sealed all the holes where control cables, etc. go through the firewall, sealed the boot cowl seam and the gap at the back. Also pressure tested the exhaust system and checked all the scat tubing, no problems found. The level is down substantially, but the detector still turns green.

Did sra-tony or morris figure out the source of the problem from the Aug. 2006 thread?

Also, on the dual muffler Decathlons where do the exhaust tips sit in relation to the bottom of the firewall? On this one the right side is a bit above the bottom of the firewall without putting the slip joint at a big angle. The left is just a little below the firewall.

Thanks for any thoughts!
 
I also have a 1973 Decathlon. It is a new aircraft to me and have only flown it three or four times. I have though of putting a CO detector in for the same reasons you mentioned. I seem to get tired quickly and also have a slight headache if flown for any length of time. I also seem to notice the smell of gas or exhaust in the aircraft. Both of my exhaust stacks are below the cowl and even. But, I do notice the slip joints are quite sloppy, is this normal? The original owner installed a clamp on each stack with safety wire to pull them to their inboard limits. This eliminates the problem of a stack moving to it's outboard limit and vibrating against the lower cowl. Still I smell something and have wondered if the stacks should extend lower. Shuld those slip joints be tight. I am also experiencing a vibration once airborn. I do not think it is the engine. It runs like a sewing machine and has only 100 hrs on it. I believe it could be a fabric vibrating or is it possible it is exhaust hitting the underbelly. This vibration can only be felt in the front seat. It would appear to be under the belly. I would be interested any possible answers to either situation. I believe I will also put a CO monitor in and see what happens.
 
My slip joints were loose when I bought mine.7kcab. It wasn't long before I had muffler separate from the exhaust stack when it cracked the exhaust at the clamp dowel hole, and it wasn't that loose beforehand. I've since had them reworked at an approved welding facility that specializes in approved aircraft exhaust systems. They are now a snug fit.
 
Thanks nite-owl. Prior to this aircraft I had an M4 Maule with a Franklin. Ths exhausts on that aricraft tend ot be loose with the concept that they will not crack. It seemed to work. Because of that experience I thought the slip joints on the decathalon might also be somewhat loose. I guess not. I will look into them again and have them reworked. They are quite loose and the location hole pins elongated. Looks like a likely place for failure. Thanks again
Ken
 
So, we've gotten the CO down to about 160 PPM (we have a CO sniffer) at the end of a one hour flight, enough to get the detector to turn only slightly green. We plugged the gaps where the landing gear joins the fuselage and the inspection panels on the belly, also took out the side vents near the pilot's knees and taped the holes shut. Can't think of anything else to plug so would be interested to hear results if kpin puts dector in his plane.

Thanks!
 
I bought a battery operated CO detector and flew the Decathlon yesterday. The detector was intended to be used in a house. I felt if there was some CO it would give some indication. The result: no CO. Regardless, I could smell something. I believe I am smelling exhaust gases, or possibly I was smelling gas from a leak somewhere in the fuel lines. I have not yet checked but I did find that the smell does not exits when the aircraft is not running. Also, when in the hanger and door closed I do not seem to get the smell. I will check that more carefully today. I do know the previous owner installed heavy clamps and tightened them to the point that the slip joints did not seem to move as much. He felt it reduced the problem. I also know that the material I used trying to seal the slip joints I could smell when heated up. This to me would indicate that any gases coming form the area of the slip joints will find its way into the cabin. I am going to remove the exhaust manifolds and muffelers and send to a repair shop for inspection. I will be retesting with reworked exhaust system and exhaust gaskets somewhere around April 10th. I will report the results.

Ken
 
I went back to the airport today to confirm the lack of smell after the aircraft has been closed up and sitting. The gas etc. smell does not exist. I removed the exhaust manifold and muffelers. The slip joints were definately leaking as well as the head to exhaust manifold gaskets. I am sending the complete exaust system to Dawley for rebuild / repair. I believe this will eliminate the smell.

Ken
 
It doesn't take much of a hole in the fabric to allow CO2 to enter the cabin. When I first bought my Champ I smelled exhaust and my son, who normally sits in the back stated it was bad in back. I found a small cut in the bottom of the fuselage and repaired it...BIG difference. Stopped the smell and headaches.
 
I received the report on the muffelers and exhaust system I sent to Dawley. I was surprised to find they discovered a number of cracks in the exhaust system. I had inspected the system and did not see the cracks. I was also told they could not see them until the system was cleaned first with a re media blast and second with a glass bead blast. I was told this is common. My exhaust system inspections will be much more extensive in the future, possibly including a blasting operation. It will be interesting to see if the exhaust smell is gone once the repaired system is installed.

Ken
 
I notice this subject was on the most popular list and that I had made a number of comments when first entered. At this time, after having the exhaust pipes rebuilt, I no longer have any smell in the cabin. The exaust stacks extend about 2 inches below the fusalage and are very even. I have blocked off the front seat heater. This eliminated some of what I would call a heat smell. The shutter valve did not do an good job of blocking hot air when closed. The aircraft is now extremely comfortable.

Ken
 
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