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Tank Vent problem

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Fred.Stucklen(at)UTCPower
Guest

Posted: Mon Jan 22, 2007 7:48 am Post subject: Tank Vent problem

Lister,   

  I'd like to share with you a tank vent problem I had last weekend (1/20/07). I flew a 30 minute IFR ride, in light/moderate snow,  from 44N to 7B6, landed, taxied to the hanger and parked the plane. As I was leaving the hanger, I happened to note that the left main tank area of the wing was deformed with notable inward scalloping….  Opening the tip tank cap, and allowing in some air, allowed the deformation to be reduced. I capped the tank prior to all the air being replaced, and then inserted some safety wire into the tip tank vent. This resulted in a "whoosh" of air into the tank. The vent was noticeable blocked with ice/snow…  The OAT at altitude was 11*F...  

  Fortunately, the main tank deformation was not serious, and removing the vacuum allowed the tank to return to its original shape.  

  The plane specifics are: RV-6A Tip-up with Jon Johansson tip tanks. The tip tank vent (located at the wing tip) is the ONLY vent for BOTH tanks on each wing. I have  3/8" tubing between the main and tip tank. The original Van's vent on the main tank has been capped.  

  This situation could have resulted in an in-flight engine failure. Fortunately, the right tank vent was clear (but it could just as easily have been blocked since it saw the same flying conditions). And, fortunately, it was a short trip…..  

  THIS IS A SINGLE POINT FAILURE ISSUE WAITING FOR AN ACCIDENT! Van's tank venting design is somewhat tolerant of in-flight blockage due to the fact they are located near the cowl warm air exits. But, even without the tips tank issue (with vents on the wing-tips) the same vent blockage problem could happen to a standard tank configuration.  

  In researching other certified IFR aircraft, I found that the tanks are usually vented in multiple ways. In addition to the main tank vents, Pipers and Cessna's have gas caps that will allow the air to go in, but will not allow gas to exit. A multiple point failure would have to happen to get a starved engine due to lack of tank venting.  

  I am going to try modifying my tank caps to have the same feature. I figure a #70 drill hole through the cap (both pieces) with a plastic "flapper" over the hole on the inside surface (glued in place with ProSeal) should do the trick (maybe even a larger hole)…..  

  Any comments?  

     

Fred Stucklen  

RV-6A  N926RV  703 Hrs     [quote][b]

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ronlee(at)pcisys.net
Guest

Posted: Mon Jan 22, 2007 8:36 am Post subject: Tank Vent problem

 	  Quote: 	
		  One nit.  I would call the possible result "fuel starvation" rather than engine failure. 	


 Why did you cap the original tank vents?



 Ron Lee



 



 

     [quote][b]

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phil(at)petrasoft.net
Guest

Posted: Mon Jan 22, 2007 9:44 am Post subject: Tank Vent problem

Okay, I'll bite. The little plastic flapper with Pro-seal idea makes me 

nervous. I can see a small piece of plastic winding up somewhere in the 

fuel system. If proper precautions are taken it might work okay, but be 

sure that the solution is not worse than the problem.



The holes in the caps are going to let water in too. You need to deal 

with that somehow.



Godspeed,



Phil Birkelbach - Houston Texas

RV-7 N727WB

http://www.myrv7.com



Stucklen, Frederic W UTPWR wrote:

 	  Quote: 	
		  

 Lister,



 I'd like to share with you a tank vent problem I had last weekend 

 (1/20/07). I flew a 30 minute IFR ride, in light/moderate snow, from 

 44N to 7B6, landed, taxied to the hanger and parked the plane. As I 

 was leaving the hanger, I happened to note that the left main tank 

 area of the wing was deformed with notable inward scalloping…. Opening 

 the tip tank cap, and allowing in some air, allowed the deformation to 

 be reduced. I capped the tank prior to all the air being replaced, and 

 then inserted some safety wire into the tip tank vent. This resulted 

 in a "whoosh" of air into the tank. The vent was noticeable blocked 

 with ice/snow… The OAT at altitude was 11*F...



 Fortunately, the main tank deformation was not serious, and removing 

 the vacuum allowed the tank to return to its original shape.



 The plane specifics are: RV-6A Tip-up with Jon Johansson tip tanks. 

 The tip tank vent (located at the wing tip) is the ONLY vent for BOTH 

 tanks on each wing. I have 3/8" tubing between the main and tip tank. 

 The original Van's vent on the main tank has been capped.



 This situation could have resulted in an in-flight engine failure. 

 Fortunately, the right tank vent was clear (but it could just as 

 easily have been blocked since it saw the same flying conditions). 

 And, fortunately, it was a short trip…..



 THIS IS A SINGLE POINT FAILURE ISSUE WAITING FOR AN ACCIDENT! Van's 

 tank venting design is somewhat tolerant of in-flight blockage due to 

 the fact they are located near the cowl warm air exits. But, even 

 without the tips tank issue (with vents on the wing-tips) the same 

 vent blockage problem could happen to a standard tank configuration.



 In researching other certified IFR aircraft, I found that the tanks 

 are usually vented in multiple ways. In addition to the main tank 

 vents, Pipers and Cessna's have gas caps that will allow the air to go 

 in, but will not allow gas to exit. A multiple point failure would 

 have to happen to get a starved engine due to lack of tank venting.



 I am going to try modifying my tank caps to have the same feature. I 

 figure a #70 drill hole through the cap (both pieces) with a plastic 

 "flapper" over the hole on the inside surface (glued in place with 

 ProSeal) should do the trick (maybe even a larger hole)…..



 Any comments?



 *Fred Stucklen*

 *RV-6A N926RV 703 Hrs*



 *

 *

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sisson(at)consolidated.ne
Guest

Posted: Mon Jan 22, 2007 11:47 am Post subject: Tank Vent problem

Just keep in mind that tank vents should not inhibit the ex-hale requirements of the air volume in the tank. My vents are close to static (perpendicular to longitudinal axis), No real need to point them forward as they very often are because they need to breath out when climbing. (Pitt’s point them backwards to keep bugs and debris from entering the vent system). If tanks are, let’s say half full of fuel and you are climbing, there is a lot of air expansion taking place and the vents are exhaling a lot of air.  

   

Just things to keep in mind. The tanks need to breathe in when coming down and they need to breathe out when climbing. The fuller the tank will mean less air has to escape but as fuel is used up the air volume   

Increases and so the greater need for a good vent.  

   

My situation is like most RV’s. Low wing,  pumped fuel.   

Gravity flow systems will need its own study.  

   

Just my own ideas.  

   

Phil in Illinois  

         

  

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Stucklen, Frederic W UTPWR

 Sent: Monday, January 22, 2007 9:47 AM

 To: RV-List(at)matronics.com

 Subject: Tank Vent problem  

  

   

Lister,   

  I'd like to share with you a tank vent problem I had last weekend (1/20/07). I flew a 30 minute IFR ride, in light/moderate snow,  from 44N to 7B6, landed, taxied to the hanger and parked the plane. As I was leaving the hanger, I happened to note that the left main tank area of the wing was deformed with notable inward scalloping….  Opening the tip tank cap, and allowing in some air, allowed the deformation to be reduced. I capped the tank prior to all the air being replaced, and then inserted some safety wire into the tip tank vent. This resulted in a "whoosh" of air into the tank. The vent was noticeable blocked with ice/snow…  The OAT at altitude was 11*F...  

  Fortunately, the main tank deformation was not serious, and removing the vacuum allowed the tank to return to its original shape.  

  The plane specifics are: RV-6A Tip-up with Jon Johansson tip tanks. The tip tank vent (located at the wing tip) is the ONLY vent for BOTH tanks on each wing. I have  3/8" tubing between the main and tip tank. The original Van's vent on the main tank has been capped.  

  This situation could have resulted in an in-flight engine failure. Fortunately, the right tank vent was clear (but it could just as easily have been blocked since it saw the same flying conditions). And, fortunately, it was a short trip…..  

  THIS IS A SINGLE POINT FAILURE ISSUE WAITING FOR AN ACCIDENT! Van's tank venting design is somewhat tolerant of in-flight blockage due to the fact they are located near the cowl warm air exits. But, even without the tips tank issue (with vents on the wing-tips) the same vent blockage problem could happen to a standard tank configuration.  

  In researching other certified IFR aircraft, I found that the tanks are usually vented in multiple ways. In addition to the main tank vents, Pipers and Cessna's have gas caps that will allow the air to go in, but will not allow gas to exit. A multiple point failure would have to happen to get a starved engine due to lack of tank venting.  

  I am going to try modifying my tank caps to have the same feature. I figure a #70 drill hole through the cap (both pieces) with a plastic "flapper" over the hole on the inside surface (glued in place with ProSeal) should do the trick (maybe even a larger hole)…..  

  Any comments? 

    

 Fred Stucklen 

 RV-6A  N926RV  703 Hrs    	  Quote: 	
		    http://www.matronics.com/Navigator?RV-List 	
0 	  Quote: 	
		   	
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       [quote][b]

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rv9jim(at)juno.com
Guest

Posted: Mon Jan 22, 2007 11:52 am Post subject: Tank Vent problem

Fred,

        I built an Europa several years back and we also had a vent that

could be blocked with a bug (or mud dobber or-)or---  So the company had

the vent line drilled in the rear of the fitting with a .070 drill.  this

way if the main vent got plugged, the rear facing drilled hole would

allow the tank to work with out stopping fuel.  We had a single tank

inside the fuselage and it was important to keep it functioning.  I am

going to back drill the fittings on my "9-A" so that should not happen to

me.

Jim Nelson

RV9-A   FWF

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Fred.Stucklen(at)UTCPower
Guest

Posted: Tue Jan 23, 2007 5:00 am Post subject: Tank Vent problem

Done properly, there is little chance that the plastic flapper idea

 on the gas can would result in something else  ending up in the

 fuel system. Even if it did fall off, there is  little chance that it would 

 make it past the strainers in both the tip tank  pickup or the main tank

 pickup. And the hole would be to small (and  restricted by the flapper)

 to allow water in.

     An examination of the Piper gas  caps, and their lack of problems

 might make you feel better about this  idea....



 Fred Stucklen

 RV-6A  N926RV 703  Hrs

  

      

       Okay, I'll bite. The little plastic flapper with Pro-seal idea makes me  

      nervous. I can see a small piece of plastic  winding up somewhere in the 

      fuel system. If  proper precautions are taken it might work okay, but be  

      sure that the solution is not worse than the  problem.

      

       The holes in the caps are going to let water in too. You need to deal  

      with that  somehow.

      

       Godspeed,

      

       Phil Birkelbach - Houston Texas

      RV-7  N727WB

      http://www.myrv7.com



  [quote][b]

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Fred.Stucklen(at)UTCPower
Guest

Posted: Tue Jan 23, 2007 5:08 am Post subject: Tank Vent problem

Good  points. 



 Fred Stucklen

 RV-6A  N926RV 703  hrs

  

 

      Just keep in mind that tank vents should not  inhibit the ex-hale

      requirements of the air  volume in the tank. My vents are close to  static

      (perpendicular to longitudinal axis),  No real need to point them forward as

      they  very often are because they need to breath out when climbing.  (Pitt's

      point them backwards to keep bugs and  debris from entering the vent system).

      If  tanks are, let's say half full of fuel and you are climbing, there is  a

      lot of air expansion taking place and the  vents are exhaling a lot of  air.

      

       Just things to keep in mind. The tanks need to breathe in when coming  down

      and they need to breathe out when  climbing. The fuller the tank will mean

      less  air has to escape but as fuel is used up the air volume  

      

      Increases  and so the greater need for a good  vent.

         

       My situation is like most RV's. Low wing,  pumped fuel.  

      

      Gravity  flow systems will need its own  study.

      

       Just my own  ideas.

      

       Phil in Illinois

  [quote][b]

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