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[63.208.148.254]) by mx.google.com with ESMTPS id oq8sm2993371pbb.13.2012.08.16.09.41.35 (version=SSLv3 cipher=OTHER); Thu, 16 Aug 2012 09:41:37 -0700 (PDT) Message-ID: <502D22BC.3010806@medialantern.com> Date: Thu, 16 Aug 2012 12:41:32 -0400 From: Chad Robinson User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: Rotary motors in aircraft CC: Chris Barber Subject: Re: [FlyRotary] Re: fuel pump replaced References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------070806090301000804020607" X-Gm-Message-State: ALoCoQkL7aRiLt4stf7nHGbQ8r8aJK2ALpKOysUdy1IlZIp8YF4SmmXAy0jAy8ECRoIr5lYSi2S5 This is a multi-part message in MIME format. --------------070806090301000804020607 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I guess it depends what you're flying. The Cozy is designed such that each tank has a small armpit sump because this guarantees that you always have a low-point drain, and gives you a small reserve against fuel sloshing forward during descents. I'm not sure what other levels you'd draw from here because the drain is already at the bottom. Al may correct me if I'm wrong, but based on his past posts I believe he's based his sump strategy on using "wet" pumps, which are designed to be cooled by immersion in fuel. This is a fine plan and the automakers use it with high reliability. I wouldn't use a "wet" pump dry - it would never last. But there are definitely pumps (which I think you have, Tracy sells, and are available in lots of places as "inline" pumps) designed to run dry and their reliability is also very good. Any pump can clog, and we're not talking about your pump overheating here. I chose a dual-pump, dual-tank configuration (with a return solenoid) for two reasons: 1. My fuel is isolated between each tank. Contamination in one doesn't necessarily contaminate the other. 2. I have cross-feed capability controlled by a switch under a safety cover. I can isolate a tank when filling (possibly transfer remaining fuel from tank A to tank B) and fill only tank B. I can then take off on tank A, which is known-good gas, known-good pump, no contamination, no clogs, no water. (I just flew on it...) If fueling contaminates tank B, loosens debris, clogs a pump, etc., I can be at altitude and prepared to deal with it when I switch over. (Leave your hand on the switch when switching for 10 seconds or so. Any hiccups, switch back immediately.) Al would probably caution us to design against statistics and testing data, rather than designing against fear. It's probably good advice. But I fear bad-fuel situations and wanted something to help deal with it. YMMV. On 8/16/2012 12:04 PM, Chris Barber wrote: > > I am using two fuel pumps. The Aux was always quieter. Now they > sound about the same. I guess since, IIRC, the primary was always > louder I "assumed" it was normal and was just limited to the > individual pump. > > I was just reviewing Al Wick's sight. He hates the rotary (ok, that > may be too strong, but he is not a fan). He is using a Subaru. I was > looking at his sump tank. He is using in the tank pumps, which I do > not wish to do as of right now. However, something he did which I > did kinda like was that he had his pumps drawing from different levels > in the tank, like my motorcycle does for it reserve. That way, if the > primary pumps runs dry, you can switch to the second pump and have a > bit more fuel....hopefully at least enough to pull your head out and > get on the ground. This seems pretty easy, especially with inline > pumps, to do and like a good idea. Seems as if you would just have to > have one pump out location higher than the other and you have a bit of > a reserve. Yeah, you should be paying attention to fuel management > but this seems like some cheap back up. However, I could be > missing something as currently I am feeding both pumps from the same > outlet. Thoughts? > > --------------070806090301000804020607 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
I guess it depends what you're flying. The Cozy is designed such that each tank has a small armpit sump because this guarantees that you always have a low-point drain, and gives you a small reserve against fuel sloshing forward during descents. I'm not sure what other levels you'd draw from here because the drain is already at the bottom.

Al may correct me if I'm wrong, but based on his past posts I believe he's based his sump strategy on using "wet" pumps, which are designed to be cooled by immersion in fuel. This is a fine plan and the automakers use it with high reliability. I wouldn't use a "wet" pump dry - it would never last. But there are definitely pumps (which I think you have, Tracy sells, and are available in lots of places as "inline" pumps) designed to run dry and their reliability is also very good. Any pump can clog, and we're not talking about your pump overheating here.

I chose a dual-pump, dual-tank configuration (with a return solenoid) for two reasons:

1. My fuel is isolated between each tank. Contamination in one doesn't necessarily contaminate the other.

2. I have cross-feed capability controlled by a switch under a safety cover. I can isolate a tank when filling (possibly transfer remaining fuel from tank A to tank B) and fill only tank B.  I can then take off on tank A, which is known-good gas, known-good pump, no contamination, no clogs, no water. (I just flew on it...) If fueling contaminates tank B, loosens debris, clogs a pump, etc.,  I can be at altitude and prepared to deal with it when I switch over. (Leave your hand on the switch when switching for 10 seconds or so. Any hiccups, switch back immediately.)

Al would probably caution us to design against statistics and testing data, rather than designing against fear. It's probably good advice. But I fear bad-fuel situations and wanted something to help deal with it. YMMV.

On 8/16/2012 12:04 PM, Chris Barber wrote:

I am using two fuel pumps.  The Aux was always quieter.  Now they sound about the same.  I guess since, IIRC, the primary was always louder I "assumed" it was normal and was just limited to the individual pump.

 

I was just reviewing Al Wick's sight. He hates the rotary (ok, that may be too strong, but he is not a fan).  He is using a Subaru.  I was looking at his sump tank.  He is using in the tank pumps, which I do not wish to do as of right now.  However, something he did which I did kinda like was that he had his pumps drawing from different levels in the tank, like my motorcycle does for it reserve.  That way, if the primary pumps runs dry, you can switch to the second pump and have a bit more fuel....hopefully at least enough to pull your head out and get on the ground.  This seems pretty easy, especially with inline pumps, to do and like a good idea. Seems as if you would just have to have one pump out location higher than the other and you have a bit of a reserve.  Yeah, you should be paying attention to fuel management but this seems like some cheap back up. However, I could be missing something as currently I am feeding both pumps from the same outlet. Thoughts?



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