R

rvdave

Well Known Member
I've been flying my 6 for approximatley 200 hours so far and have been trying to figure out where the exhaust smell is coming from during a slow down and descent while coming in to the pattern. I've heard some think it's coming from the tail area others from the aileron bellcrank, or the flap rod hole? Are any of you experiencing this, have you found a solution?

Dave Ford
RV6 N516D
Lake City, MI
 
You're not alone

My friend Dave (another RV-6 Dave, imagine that) has the same problem with his RV-6. Except sometimes it seems to smell more like avgas than exhaust. It does not happen every flight but is common. I put a carbon monoxide detector on the panel and it has never shown a carbon monoxide induced color change. The smell can actually be nauseating. It's kind of unnerving too. Someone suggested that he should put a bright light in front of the firewall inside a dark hangar and look for leaks. If you figure it out I would like to hear your solution. Good luck.
 
We also had this problem ... we found when we deployed the flaps and hadn't burned fuel out of a full tank, that tanks vent would draw a 1/2 gallon or so of fuel out.
 
arffguy said:
My friend Dave (another RV-6 Dave, imagine that) has the same problem with his RV-6. Except sometimes it seems to smell more like avgas than exhaust. It does not happen every flight but is common. I put a carbon monoxide detector on the panel and it has never shown a carbon monoxide induced color change. The smell can actually be nauseating. It's kind of unnerving too. Someone suggested that he should put a bright light in front of the firewall inside a dark hangar and look for leaks. If you figure it out I would like to hear your solution. Good luck.
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Get a *real* CO detector, you can pick up a cheap one from Home Depot/Lowes or get one of the digital ones from AeroMedix. Either way, that paper element, if it wasn't *brand new*, probably was in effective. The "nausea" you described is your body telling you that there is CO in the area.... A typical first sign, one that some people don't always suffer from. I do and I now carry a digital CO detector with me all the time...

Be careful, that stuff is scary if not taken care of... Even the fuel smell, could be in the exhaust. You mixtures could be set *way* too rich and low power or idle could be shipping unburt fuel out the exhaust.
 
Yeah, the nausea is also what he does to me because he likes to do endless steep turns (unnnounced alot of the time) so sometimes I am nauseated anyway. The smell comes and goes so quickly I am not sure if a CO detector would register it or not.
 
arffguy said:
Yeah, the nausea is also what he does to me because he likes to do endless steep turns (unnnounced alot of the time) so sometimes I am nauseated anyway. The smell comes and goes so quickly I am not sure if a CO detector would register it or not.
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Well, CO *isn't* smell detectable. What you are most likely smelling is exhaust gas byproducts that were not consumed in the combustion event. Mind you, all exhausts will smell, but back to the original topic. CO isn't smell detectable.

So, you could have lots of it and not know it. It also doesn't dissapate quickly, so if you have it, you'll know with a detector. Spruce also sells one that is made by CO Guardian that just plugs in a 12V power port.

Either way, if you can smell something, that just isn't right as you know.

I've heard that a low pressure can be created around the canopy (of any airplane), and if the seals aren't good, the low pressure will draw *thru* the cockpit area if there are leak areas. This could also be happening.
 
Smelling exhaust in an RV during slow speed flight isn't unusual. When the plane is at a relatively high angle of attack, the exhaust may spill out from under the belly and get in any number of places. I smell some from time to time when at high angles of attack, and most I know around here have the same experience. Get a CO detector if you want to convince yourself that there isn't something else going on.
 
aadamson said:
I've heard that a low pressure can be created around the canopy (of any airplane), and if the seals aren't good, the low pressure will draw *thru* the cockpit area if there are leak areas. This could also be happening.
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You know, he had some pretty significant gaps in his canopy and now has added some seals to it and I didn't notice anything last time. I will have to ask him if he still notices it. The gaps also gave a squealing noise in the headsets that drove me nuts. A huge difference.

Originally we thought we smelled exhaust (hence the Quantum Eye CO detector I put on the panel). Then on a later flight we thought we smelled fuel.

I figure that if I am smelling "exhaust" then I probably am getting CO too--wouldn't you think?

I think the real reason I got nauseous lately is that we been flying in the ungodly heat of late too. We got back to the hangar the other day, it must have been 100 degrees already and the high hit 109 degrees. RV's are great but they get very warm inside.
 
I'd suggest you/he has a cockpit leak somewhere. Both of those two smells would suggest that. Fuel could be either unburned if the throttle were pulled back, and well, exhaust we know where that is coming from.

Check everything is the obvious... next time up, take a piece of white ruled paper and put it against the seals of the canopy, if there is suction, it will stick at the seals.
 
It occurs to me that while CO would be a big safety issue, the smell of raw fuel could be even more significant (think fire). I'd be looking real close at every hose, tube, gasget, selector and fitting in that fuel system. The fact that the smell gets worse at low speed could be due to reduced rpm, rich mix, or high AOA, but it could also be due to a decrease in fresh cockpit ventilation. Small fuel leaks can be very tricky to detect since the fuel will evaporate off as its leaking, and never actually look wet. Keep us posted on what you find.
 
Fuel will come from the vents during a rapid climb or aerobatic maneuvering involving a climb with a full tank(s). This fuel then can get on the belly and find its way in. In this case, it is a transient. No big deal.
 
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