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RV-10: Fuel Smell When Turning

Geico266

Well Known Member
This has been happening for as long as I have had the plane. Seems to happen when I am turning sharp like pattern work. There is a moderate smell of fuel. Sometimes when decending rapidly.

Is the fuel coming from the overflow vents and he fumes come back in though the tail area? That does not make sense as the cabin should be pressurized, but maybe turning creates negative pressure? No leaks that I can find in the cabin tunnel, wing root.

Just looking for others wih the same observation or tips on how to cure.

Any thoughts?
 
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This is interesting--

I assume that this -10 has plans build vents? I wonder if somehow the fumes are collecting in the lower panels through the spar hole, or the flap rod hole, and settling in the cabin? The reason for my question is that if seems that several -10s have this issue.
Any thoughts from the 10 guys?
Tom
 
Seal off around vent/snap bushing with proseal. Seal off spar openings. Install aileron pushrod boot.

When you are turning the vent line fills with fuel on the lowered wing side. When leveling off it empties due to dihedral/gravity. Positive pres underneath and neg pres on top allows fuel to enter either at vent tube or aft end of lower fairing.

That is my best guess for now. Keep us posted what works.
 
How quickly does the smell come on when you turn and how quickly does it go away when you level off?
 
This has been happening for as long as I have had the plane. Seems to happen when I am turning sharp like pattern work. There is a moderate smell of fuel. Sometimes when decending rapidly.

Is the fuel coming from the overflow vents and he fumes come back in though the tail area? That does not make sense as the cabin should be pressurized, but maybe turning creates negative pressure? No leaks that I can find in the cabin tunnel, wing root.

Just looking for others wih the same observation or tips on how to cure.

Any thoughts?

I have wondered MANY times if this is what contributed to my explosion. I put the plane into a sharp turn and an extreme slip for before landing.
 
I have wondered MANY times if this is what contributed to my explosion. I put the plane into a sharp turn and an extreme slip for before landing.

Todd, before the incident did you ever notice the smell of fuel when you were in the pattern?

How full were your tanks?

Was the "official" cause ever figured out?

How are you doing with recovery?
 
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Todd, before the incident did you ever notice the smell of fuel when you were in the pattern?

How full were your tanks?

Was the "official" cause ever figured out?

How are you doing with recovery?

What was different than normal was the week before for the Race to Ridgeland I had sealed up all the gaps between the fuselage and wing. I have wondered if that had changed the way fumes were dissipated from the wing area. Both tanks were half empty.

No official cause. Which I doubt there ever will be one.

I have been at 100% for a year now. Ankles sting every once in a while but I don't even notice anymore. And thanks for asking.
 
Larry,

I don?t know anything about -10 construction, however, would this trouble shooting procedure work??? Connect some plastic tubing to the end of each fuel vent. Run each line of tubing down the fuselage centerline and past the trailing edge of the wing. Mount the tubing with speed tape or equivalent. Conduct a test flight.
 
What was different than normal was the week before for the Race to Ridgeland I had sealed up all the gaps between the fuselage and wing. I have wondered if that had changed the way fumes were dissipated from the wing area. Both tanks were half empty.

No official cause. Which I doubt there ever will be one.

I have been at 100% for a year now. Ankles sting every once in a while but I don't even notice anymore. And thanks for asking.

Since you sealed up the wing gaps can i assume you were smelling fuel? Or was it just to block cold air? Mine runs warm so there is no reason to seal it.

How is your daughter doing?
 
Larry,

I don’t know anything about -10 construction, however, would this trouble shooting procedure work??? Connect some plastic tubing to the end of each fuel vent. Run each line of tubing down the fuselage centerline and past the trailing edge of the wing. Mount the tubing with speed tape or equivalent. Conduct a test flight.

That is an interesting test. Thanks.
 
Larry,

I don?t know anything about -10 construction, however, would this trouble shooting procedure work??? Connect some plastic tubing to the end of each fuel vent. Run each line of tubing down the fuselage centerline and past the trailing edge of the wing. Mount the tubing with speed tape or equivalent. Conduct a test flight.

If you do this, keep in mind the stock fuel vent has a slash cut to face into the airstream, thus creating a slight pressure in the vent line.

Tubing taped to the fuse C/L could easily create a low pressure in the tubing, depending on how the end of the tube is facing.
 
If you do this, keep in mind the stock fuel vent has a slash cut to face into the airstream, thus creating a slight pressure in the vent line.

Tubing taped to the fuse C/L could easily create a low pressure in the tubing, depending on how the end of the tube is facing.

Good point.
 
I have this issue on my RV-10

Typically smell it when the tanks are very fully and I am turning and descending at the same time (ie base to final).

Definitely related to how much fuel is in the tanks since it only happens with full tanks.
 
Fuel smell

Has anyone found a cure for the fuel smell on landing?
About 33 hours into phase one, I have noticed the fuel smell upon entering the pattern most of the time. It is very faint and mostly with the tanks near full.
Glad I new about it from this thread as it was somewhat disconcerting
when I got my first whiff of fuel while landing.
 
No fuel smell on mine

I have tested uncoordinated/steep turns and -.5 G's with 25+ gallons fuel.

I have sealed spar pass throughs with foil tape. Sealed aileron pushrod with Abby's boots. Prosealed bottom skin to side skin joint. Prosealed bottom wing root fairing, as it does not need to be removed for inspections. Prosealed around snap bushing at vents.

Cabin is always under negative pressure unless front and rear vents are wide open on mine. Any fuel leaks from firewall to tanks will end up in the cabin.
 
I can't help but think this contributed to Todd's incident.

Sure would be nice to find a cure.

Ideas -10 drivers?
 
As Wayne stated, the cabin has negative pressure and will suck anything inside that is close, such a raw gas and fumes. Maybe the vents need to be relocated outboard of the tank. That's where they are on my Archer. Alternatively, extending the vent into the slipstream more by extending them an inch or so may help.
Those who notice this problem report it when turning or descending, could this imply that the vent pickup is to low in the tank and is easily submersed? I purchased the QB wings, so I am not intimately familiar with the placement, or the builders flexibility with the placement of the vent inside the tank.
Has anyone with this issue spoken to Vans?
 
I ran my 1/4" vent as close to top of tank as possible by putting a bend in the end. If my tanks over flow from expansion you don't want to remove caps as the fuel is near the outside of filler necks. Just drain a little from quick drains.

I think with tubing running from outboard to inboard this helps keep fuel in the tank during a slipping or skidding turns. If the vent was exiting outboard more fuel would be lost during slipping turns, but it would exit at a more favorable location. I like the idea of extending it another inch.

With all of the precautions I have taken after hearing of this problem not just with the -10, I have no fuel vapors entering the cabin. I also ran my combustible gas leak detector during initial test flights.
 
I can only suspect the vents since I have no fuel leaks anywhere.
Happens with full tanks only.

Taping all the openings seems like a good fix.
Relocating the vents would be a true solution.
Maybe route them outboard to the first inboard inspection bay?
Don't want to make my passengers nervous.

Flew 3 hours today and returned to the airport with 10 gallons total, no smell.:)
 
Fuel smell gone!

After flying passengers and having all of them tell me they smell fuel upon entering downwind, I could no longer ignore the problem. The smell was always present during initial flap lowering and slowing down on downwind.
I did have the vents installed per plans and I still don't understand how some
RV-10s don't have any smell in the cabin.

Here is what I did:

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I used JD airparts http://www.jdair.com/rv-10/ and positioned these on the outer side of the center wing inspection plate. Routing the vent lines required
7/16 holes in the spar webs to accomodate plastic bushings. Drilling a single hole in the wingspar web only, would have been preferable but no way to access that part for drilling. The aluminum vent tube will have to be removed in order to remove the wing, something you don't normally have to do during the life of an airplane.
I flight tested today by climbing to altitude and then descending into the pattern as usual, slowing down and applying flaps abeam the numbers.
I did approaches with extreme forward and side slips, both for extended periods as well as rapid back and forth from side slip to forward slip.
I detected no smell of fuel at any point during these maneuvers.
One thing I noticed was the almost full fuel tank (50Gallon total) showed
less than 5 gallons during side slipping, telling me that at least some fuel must have reached the vent opening inside the tank and subsequently spilled out the vents. Again, I noticed no smell anymore whatsoever..
I did consider locating the vents on the fuselage belly but knowing how fumes find their way into the cabin I decided to keep them as far out in the wing as possible.
 
Ernst,

Glad you got it fixed.

We got our first smell of fuel on final while kicking the crab out a few weeks ago. Full tank on right, 25 in left. Even with all of the wing root sealing, :cool:vapors made it through. I am going to run mine inboard and out fuse bottom beneath seats. I did notice evidence of fuel running back to rear edge of lower wing root fairing. It then flows up and back forward into fuse openings due to lower cabin pressure.

I will try to post results too.
 
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Ernst,
When you were looking for ways to route the lines, if the wings were not on the fuse, did you see a preferred way to get the line over to the other side of the tank where you ultimately mounted the vent,without drilling the spar web? I am considering doing a similar mounting, but just have not gotten around to it yet.
 
There is only one route and it's through the spar web.
The preferred route would be the spar web only, just below the aileron
bell crank tube.In this location you only have to drill the spar web but it is not accessible without having the wings removed. This location would also allow you to keep the tubing in place for wing removal.
One the other hand, drilling through the center section web and the spar web
was a simple task starting from the rear and using a standard size drill.
I am not concerned about a nice round hole 7/16th in diameter in the center of an 8" web.
The fuel smells however were a real concern to me and reading the previous posts, I can't help but agree with Todd that his explosion could have been the result of fuel vapors migrating from the vents into the cabin.
I guess we'll never know but I have done what I felt needed to be done
to help prevent another accident like his.
 
Nice work Earnst, looks like a great fix.

This might be a dumb idea, but what about putting a check valve of some kind on the vent tube? The design is for air to enter the line, pressurize the tank in flight, and allow for air to escape when the air expands in the tank on the ground. Certainly, failure would be a problem.

Any thoughts? :confused:
 
A check valve with a tee works great for ice/bug blockage. A check valve would not work in the vent line by itself as you have flow in both directions.
 
A check valve with a tee works great for ice/bug blockage. A check valve would not work in the vent line by itself as you have flow in both directions.

I am probably inventing something that does not exist, but can you have check valve that would allow air to flow both ways, but not liquid? :confused:
 
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Ernst,
I think I am going the way you did from the start. My wings are still sitting un-attached and I agree, a 7/16" hole should not be an issue.
 
Food for thought...

How about a small expansion volume in the vent line to catch liquid fuel overflow? The line from the tank would come into or near the bottom, the line to external vent would come out of or near the top. You will still get vapor out the vent, but no liquid. I don't have a good feel for how large it would have to be*(quart, gallon(s)?, or where it should be placed (wing root; under the wing walk; outboard leading edge?)

*A 6" cube holds almost a gallon; an 8" cube holds well over 2.
 
I would guess the 6' x 1/4" vent line probably holds a couple oz fuel. Maybe a brake resorvoir with two 1/8" npt-1/4" flare fittings would work with tank coming in side and overboard out top. Kind of like some install on their crankcase breather. We use same thing on heat pumps to boil excess liquid refrigerant off before entering compressor. One drawback is if it filled up with water on a flight through rain then froze it could split open. It is good to look at all the possibilities.
 
Fuel Vents

Our Saratoga has the fuel vents in the bottom of the wing about half way down the wing. I really like the idea of Venting the highest point of the tank out the bottom of the wing. Drilling a clean 7/16 hole in the wing spar web for a AN bulkhead fitting would work real well then you would have no issues if the wing had to come off for any reason. Running the Vent line up thru a a lightning hols with a bracket that had a clamp to hold the vent line secure then to a fitting just outboard the access panel would be a no brainer at all.

Well looks like i have a plan of attack now. I am also going to install a screened vent in the tunnel so that any fluids or fumes in the tunnel will have a place to escape to the out side of the fuselage prior to the area where the flap motor is.

I am also thinking about a boot the close up the opening where the elevator push rod goes thru the bulkhead near the flap motor. This sealing the tunnel off from any possible fumes getting to the flap motor.

Just a few thoughts.
 
The high wing Cessnas do have a check valve (of sorts) in their vent lines. In flight the valve opens (pressure from outside). Sitting on the ramp in the sun, the fuel and air want to expand and run out the vent. The check valve is closed but it has a very small hole in it to let the pressure out, the premise being the pressure will only build slowly so a small hole is all you need. So you can get a very slow drip but not fuel running wildly out. When you see a Cessna tied down with fuel pouring out the vent it means this check valve needs to be replaced.

I'm sure you can buy the part from Cessna ($$$) and try it out.
 
I don't intend to hijack the thread, but this makes me wonder if the standard tank vent is the cause of the problem venting fuel from the key slot on the Newton fuel caps that Van's sells. I was looking at a very nice Harmon Rocket a few days ago and noticed he had the Newton caps. I asked if his siphoned fuel out when the tanks were full. He said he filled his to the top regularly and never lost a bit of fuel out of the slots. He also confirmed that these were the caps sold by Van's. Well, everybody I know that installed the Newton caps (sold by Van's) on an RV-10 has this problem. Could it be the tank vents?:confused:
 
David,
I don't understand how the tank cap has anything to do with the vent
and I am not exactly sure what you mean by key slot.
Standard tank caps from Vans don't have key slots.
I really don't think there is anything wrong with the vent system in the tanks.
The tube inside the tanks ends about a 1/4" from the top skin and half an inch away from the outboard tank rib, there is no better place for the vent opening, its the highest point in the tank.
A little fuel spilling out of the vents is also pretty normal in all airplanes both in uncoordinated flight and when heat expansion forces fuel out from an overfilled tank.
The crux of the problem is the location of the vent opening to the atmosphere just outside of the cabin and in very close proximity to the opening for aileron push rods.
The vent installation is very simple and should be kept as
simple as possible. Routing an extension out to the wing was the simplest thing I could think of.
 
... One drawback is if it filled up with water on a flight through rain then froze it could split open. It is good to look at all the possibilities.

Is there any more possibility of water collecting there than there is of it collecting in the vent line anyway? The "volume" is essentially a wide spot in the line.
 
I dont know anything about this, other than listening to you guys. Todd's 10, I am familiar with. (Hey Todd). I do think that you guys are on to something with the vents. Might it be possible to re-route the vents to the wingtips, ans exit to the rear? Yep---dumb question
Tom
 
David,
I don't understand how the tank cap has anything to do with the vent
and I am not exactly sure what you mean by key slot.
Standard tank caps from Vans don't have key slots.
I really don't think there is anything wrong with the vent system in the tanks.
The tube inside the tanks ends about a 1/4" from the top skin and half an inch away from the outboard tank rib, there is no better place for the vent opening, its the highest point in the tank.
A little fuel spilling out of the vents is also pretty normal in all airplanes both in uncoordinated flight and when heat expansion forces fuel out from an overfilled tank.
The crux of the problem is the location of the vent opening to the atmosphere just outside of the cabin and in very close proximity to the opening for aileron push rods.
The vent installation is very simple and should be kept as
simple as possible. Routing an extension out to the wing was the simplest thing I could think of.

Ernst, I am referring to the retrofit locking caps that Van's sells here. Several RV-10's have installed these caps and they all have the fuel venting through the key slot problem when the tanks are full. My question was why would this be the case on the RV-10 and not on a Harmon Rocket. The Rocket tank is certainly vented, but probably not like the stock Van's vent. I was simply curious if the Van's tank vent was pressurizing the tank more than another design might, or something like that. FWIW, I have never had the fuel smell problem that is the heart of this thread. So is the reason I don't have the smell because the key slot is relieving pressure in the tank?? I am hoping someone smarter than me might have some ideas about this.
 
David,

That's a logical assumption. The area above the wing is lower pressure as long as the plane is flying right side up, so, if the fuel cap isn't tightly sealed, the natural tendency would be for air (and fuel, if in the line) to flow from the vent opening back into the tank, then out the fuel cap.
 
David,

I bought the deluxe locking caps from Van's and don't have any leakage from key slot. I always top off to within 1/2" of top skin or 1/4" up on cap flange, so pretty full unless temps are warming up then I leave it down some for expansion room. Maybe the "pitot" pressure inside the tank cannot build with a leaking key slot. As you turn in the pattern the pressure on that angled cut keeps fuel from coming out due to air moving towards tank.

Thinking back to my flight the other day...I fueled with cold fuel, it warmed up some during the flight back home at 140 kts. As I slowed to about 80 kts and cross controlled on final is when I smelled it. I immediately opened all four fresh air intakes. It cleared in seconds. I did not touch flaps until parked and the family was out.(Yes Todd, we learned from your experience) Look at top tank skin between ribs during flight, it is bowed up. Partially due to bernoulli? and partially to the "pitot" pressure. Upon slowing down the skins go down due to both pressure loss inside and pressure increase outside. This forces fuel out the vents. Also probably had something to do with the 25 kt direct xw and me using almost full left rudder. At any rate, this is a great discussion guys.
 
Wayne, I remember the conversation we had about fuel caps when you were in New Smyrna Beach. My wings were QB, so the only option available at the time for locking fuel caps were the Newton caps that Van's sells. It is pretty clear that the design of those caps allows fuel to vent through the key slot if the fuel level in the tank is up to the bottom of the cap, and the tank is pressurized via the vent. I think that is possibly the reason I don't have the fuel smell in the cabin that others are reporting. I know that virtually everybody that installed the Newton locking caps on their RV-10 reports the same issue with fuel venting through the key slot. I am curious to know if any of those owners have the fuel smell problem. Perhaps I should take a look at the tank vents on the Harmon Rocket I saw, since he reports no venting at all with the Newton caps.
I guess I would prefer having to deal with the venting when the tanks are filled to the top versus the fuel smell in the cabin.
 
Has anyone considered routing the vents outboard, on the opposite wing? It's how my other airplane is plumbed and it would surely keep fumes out of the cockpit...
 
Fuel smell again

I really thought I had this problem solved.
After relocating my fuel vents and testing as described in an earlier post,
I really believed there was no more fuel smell during landing.
Guess what, I smell fuel again, not nearly as strong but it is definitley still there, just on landing about the time I lower the flaps and turn base.

I just returned from a trip to Disneyland that included 4 stops to get there and back. All 4 landings left no doubt about the fuel smell, it's not alarming
but extremely distracting both for me and my passengers.
I have no leaks anywhere that I am aware of.

I am out of ideas....
Anyone have any suggestions?
Where does the smell come from?
 
must be in the cabin?

I dont see how fuel smell can come from outside the cabin with so many critical fuel lines, pumps and filters in the tunnel. there is nothing on the firewall forward that would make a smell unless it is fuel overflow dumping in the FAB. you say it was associated with 4 landings, makes me want to suspect operation of the boost pump. We have no fuel smell in our RV10 burt did find small amount of leaking from fittings at the annual in Nov. 2011
 
It sounds like the boost pump is causing the issue. Not the pump itself necessarily, but the increased pressure. I assume you land with the boost pump on... You could try to leave the pump off during your next landing. I would open the tunnel and run the pump with the mixture set a lean and see if the back pressure causes a leak. Check for fuel stains everywhere.
 
I'll check everything.

Boost Pump: The boost pump is on for take off and I smell no fuel except on landing. I also turn the boost pump on somewhere about 10 miles out from landing and I can't smell anything until I get to downwind and extend the flaps.

4 landings:
I did about 10 hours of flying since I posted my test and thought I had no fuel smell. I detected an ever so slight smell soon afterward and more so when I carry passengers in the back.
The last 4 landings were quite fully loaded and I only pointed that out to show a difference between my tests and now.

I may not have all the firewall penetrations sealed up tight yet but there should be no fuel smell in front of the firewall either and why only for landing?

It's driving me nuts.
 
I agree with above posters...sounds like a leak between boost pump and fw ftg. With engine running and boost pump off there can be a slight negative fuel line pressure in that area which draws a small amount of air in. I had one before first flight just fwd of boost pump. One drip every 5 min with boost pump ON, engine OFF and mixture ICO. Barely noticed fuel smell sitting static and difficult to locate. Being an hvac guy, I went out and grabbed my combustible gas leak detector and homed right in on it. I flew the first 5 test flights with the detectors probe sniffing the tunnel. If you locate a leak, check for tightness, but also be sure to inspect flare with a 5 or 10X magnifier for any cracks or other defects. Which tubing do you have...Vans supplied 3003 or 5052? Good luck.
 
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Boost Pump: The boost pump is on for take off and I smell no fuel except on landing. I also turn the boost pump on somewhere about 10 miles out from landing and I can't smell anything until I get to downwind and extend the flaps.

I may not have all the firewall penetrations sealed up tight yet but there should be no fuel smell in front of the firewall either and why only for landing?

It's driving me nuts.

On landing, with flaps down and engine nearly idle...this means the boost pump is applying max pressure to fittings between bp outlet and mech pump inlet due to low fuel flow/low deck angle/slight vent tube "pitot" pressure on tanks. Coupled with that you have flaps coming down which changes cabin pressure as we have a huge opening that opens higher pressure air beneath wing to cabin through spar openings/aileron linkage. Any drips of fuel will immediately be pushed through flight control slots near seats/rudder cable openings/brake line opening. Thank goodness most times we can smell fuel before it gets to a rich enough mixture to ignite. I opened all fresh air intakes the one time I smelled it during 25 kt direct xw landing after kicking the crab out and it purged quickly right back out. I found fuel stains running back from vent then up into wing root area at rear.
 
What Wayne stated is why I suggested you run the pump on the ground with the mixture full lean. You need to get the pressure up in the lines, and that will do it. When you are landing, the pressure is the greatest in the lines, when you are taking off the pressure is the lowest it will be. That's got to be why you smell it on landing.

Try my experiment and then try landing without the pump on. If you are concerned about the lack of pump, then start high enough to glide to the airport.
As Wyane stated, it may take a while to notice any appreciable leak....
 
Boost Pump

The Boost pump scenario makes the most sense to me at this time.
I'll do a test flight and landing without the boost pump on, see what happens.
If that is in fact the case, the area of possible leaks would be confined to the fuel line between boost pump and mechanical pump.

Thanks, I'll report back.
 
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