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kissell
Joined: 05 Dec 2006
Posts: 18
Location: Beavercreek, Ohio
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 Posted: Sat Sep 27, 2008 1:58 pm Post subject: Fuel Tests |
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Hi Group,
Here are the test results of my fuel test as promised.
I have a CH701 with dual factory wing tanks that are connected together by the gascolator. The are no fuel valves to manage fuel flow, only a fuel cut off valve that is common to both tanks.
Today I clamped the fuel line and drained the right fuel tank completely. After warm up and an extra long engine run up I climbed to 1500 feet. After reaching cruise and staying close to the airport I released the clamp on the fuel line. This created an instant empty tank in the fuel system. This should be no different than if I had run one tank dry in flight. Once the clamp was released I continued to fly around the airport for 20 minutes. I then replaced the clamp in flight and landed. During the flight the engine performed perfectly normal with no sign of fuel problems. I ran the engine at 5000 RPM during this test. After landing and shutdown at the hangar I removed the tank drain fitting and drained 1 quart of fuel from the previously empty tank. This indicates that during flight fuel was consumed from the left tank and some fuel also flowed from the left into the empty right tank. I would think that given time the two tanks would even out and fuel would then flow from both.
From my flight test I am convinced that running one tank dry will not create a safety of flight problem. Fuel will continue to flow from the other tank. The only caveat is that both tanks must have nearly the same pressure above the fuel. By nearly I mean less than 0.2 PSI difference. I think I have that with the snorkle vents I installed.
While I had the right tank drained I calibrated my DIP tube. If any of you have the Zenith factory tanks installed and are or plan on using the J-AIR Universal FuelHawk fuel gauge, here is the relationship I have found. The dip tube has a scale from 1 to 14 along the length of the tube. The first gallon in the tank will not show on the gauge, the second gallon will indicate one (1) on the scale. As you add each additional gallon the indication will go up one (1). When you get to 9 gallons the gauge will indicate 8, when 10 gallons are in the tank it will indicate 9 3/4 . When filled to the bottom of the filler neck the gauge will indicate 13 and you will have 11 gallons in the tank. The Zenith tanks can collectively hold 22 gallons, of course not all of that is useable. I consider the last gallon off limits in each tank, so I will continue to plan with 20 gallon.
In simple terms the amount of fuel in the tank is the dip number + 1 gallon, so long as the number is at or below 8. Then 9 3/4 is 10 gallons and 13 is 11 gallons. The tank design has a sloped top which accounts for the non linear behavior at the nearly full point.
Happy flying,
Bob Kissell N701UB
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lgold(at)quantum-associat
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| Posted: Sat Sep 27, 2008 2:18 pm Post subject: Fuel Tests |
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Bob,
Thanks for sharing this very valuable info with the group.
My engineering background led me to believe all-along that, unless the empty tank (for some unimaginable reason) had a vacuum pulling fuel up, an empty tank could not stop fuel from flowing from the full one.
Thanks again,
Les
[quote] From: owner-zenith701801-list-server(at)matronics.com [mailto:owner-zenith701801-list-server(at)matronics.com] On Behalf Of bob
Sent: Saturday, September 27, 2008 2:59 PM
To: zenith701801-list(at)matronics.com
Subject: Fuel Tests
Hi Group,
Here are the test results of my fuel test as promised.
I have a CH701 with dual factory wing tanks that are connected together by the gascolator. The are no fuel valves to manage fuel flow, only a fuel cut off valve that is common to both tanks.
Today I clamped the fuel line and drained the right fuel tank completely. After warm up and an extra long engine run up I climbed to 1500 feet. After reaching cruise and staying close to the airport I released the clamp on the fuel line. This created an instant empty tank in the fuel system. This should be no different than if I had run one tank dry in flight. Once the clamp was released I continued to fly around the airport for 20 minutes. I then replaced the clamp in flight and landed. During the flight the engine performed perfectly normal with no sign of fuel problems. I ran the engine at 5000 RPM during this test. After landing and shutdown at the hangar I removed the tank drain fitting and drained 1 quart of fuel from the previously empty tank. This indicates that during flight fuel was consumed from the left tank and some fuel also flowed from the left into the empty right tank. I would think that given time the two tanks would even out and fuel would then flow from both.
From my flight test I am convinced that running one tank dry will not create a safety of flight problem. Fuel will continue to flow from the other tank. The only caveat is that both tanks must have nearly the same pressure above the fuel. By nearly I mean less than 0.2 PSI difference. I think I have that with the snorkle vents I installed.
While I had the right tank drained I calibrated my DIP tube. If any of you have the Zenith factory tanks installed and are or plan on using the J-AIR Universal FuelHawk fuel gauge, here is the relationship I have found. The dip tube has a scale from 1 to 14 along the length of the tube. The first gallon in the tank will not show on the gauge, the second gallon will indicate one (1) on the scale. As you add each additional gallon the indication will go up one (1). When you get to 9 gallons the gauge will indicate 8, when 10 gallons are in the tank it will indicate 9 3/4 . When filled to the bottom of the filler neck the gauge will indicate 13 and you will have 11 gallons in the tank. The Zenith tanks can collectively hold 22 gallons, of course not all of that is useable. I consider the last gallon off limits in each tank, so I will continue to plan with 20 gallon.
In simple terms the amount of fuel in the tank is the dip number + 1 gallon, so long as the number is at or below 8. Then 9 3/4 is 10 gallons and 13 is 11 gallons. The tank design has a sloped top which accounts for the non linear behavior at the nearly full point.
Happy flying,
Bob Kissell N701UB
| Quote: |
href="http://www.matronics.com/Navigator?Zenith701801-List">http://www.matronics.com/Navigator?Zenith701801-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
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[b]
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georgerace
Joined: 25 Oct 2006
Posts: 788
Location: Albion, MI
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| Posted: Sat Sep 27, 2008 3:41 pm Post subject: Fuel Tests |
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Thanks Bob, I have the exact same setup as you do and have been concerned since the subject was raised.
Your research and test has put this concern to rest once and for all.
Thanks again,
George
N73EX - FLYING
From: owner-zenith701801-list-server(at)matronics.com [mailto:owner-zenith701801-list-server(at)matronics.com] On Behalf Of bob
Sent: Saturday, September 27, 2008 5:59 PM
To: zenith701801-list(at)matronics.com
Subject: Fuel Tests
Hi Group,
Here are the test results of my fuel test as promised.
I have a CH701 with dual factory wing tanks that are connected together by the gascolator. The are no fuel valves to manage fuel flow, only a fuel cut off valve that is common to both tanks.
Happy flying,
Bob Kissell N701UB
[quote]
href="http://www.matronics.com/Navigator?Zenith701801-List">http://www.matronics.com/Navigator?Zenith701801-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
| | - The Matronics Zenith701801-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith701801-List |
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Check out my CH-701 project at:
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