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#11
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Tony Cox wrote:
"Koopas Ly" wrote in message om... The only time that fuel is set to one particular tank is on the ground. I've never used fuel from only one tank in flight. Why would someone do that? Some models of 172 *require* you to select a single tank above 5000', due (supposedly) to vapor lock problems. Check your POH. No 'supposedly' about it. Ours locked at 7500' on a humid day because one of my partners didn't believe it could happen and didn't follow the procedure. Fortunately an airport was within glide range. Strangely enough, by the time he landed the engine was running fine again.... -- Frank....H |
#12
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"COUGARNFW" wrote:
Amazing...all those answers by 172 owners and no one of them went to the net to find the "truth". The question is why is the selector placed in the "BOTH" position for landing, not why is the selector placed in some other position above a certain altitude for certain models. |
#13
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With regards to fuel tanks in a C172, why does the takeoff and landing
checklists both call for the fuel selector handle to be in the "both tanks" position? The only time that fuel is set to one particular tank is on the ground. I've never used fuel from only one tank in flight. Why would someone do that? Not really related to 172's, but our RV-6 has no "both" position... either left, right, or off. You just have to remember to switch them occasionally. Also, IIRC the 150 has just "on" and "off". |
#14
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"Bob Martin" wrote in message ... With regards to fuel tanks in a C172, why does the takeoff and landing checklists both call for the fuel selector handle to be in the "both tanks" position? The only time that fuel is set to one particular tank is on the ground. I've never used fuel from only one tank in flight. Why would someone do that? Not really related to 172's, but our RV-6 has no "both" position... either left, right, or off. You just have to remember to switch them occasionally. Also, IIRC the 150 has just "on" and "off". There is a significant difference here between low wing, and high wing designs. If you have a low wing aircraft, and have a 'both' selector, if one goes empty, air is sucked into the system by the fuel pump, and fuel delivery stops. Hence low wing aircraft with a 'both' position, have to have a central 'sump' from which the fuel is drawn. On high wing aircraft, where the fuel is delivered by gravity, if one tank goes dry in the both position, fuel will still feed from the other. Hence 'both', is relatively unusual on low wing designs, but more common on high wing planes. This is why your RV6, doesn't have a 'both'. Best Wishes |
#15
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Koopas Ly wrote: With regards to fuel tanks in a C172, why does the takeoff and landing checklists both call for the fuel selector handle to be in the "both tanks" position? It's basically to ensure that you will have fuel through the entire takeoff. The reason it's done for landing is in case you need to go around. The idea is that, even if one tank goes empty or has some other problem, you will have a steady supply of fuel. The only time that fuel is set to one particular tank is on the ground. Then you don't have to worry too much about it, do you? I've never used fuel from only one tank in flight. Why would someone do that? I do it in my Maule to equalize fuel burn. It will draw down the left tank more rapidly than the right if I don't. I believe most Cessnas are worse in this regard than my aircraft; my 150 certainly was. Also, why is the fuel selector set to one tank during refueling? Is it to minimize crossfeeding? Yep. In my Maule, the lower tank will overflow through the vents if this is not done. My 150 (which didn't have the option of selecting tanks) would do the same if the vented tank was the lower one. Note that my Maule will do this even if the selector is set to "off". Dunno if that's the case with a Cessna. George Patterson Some people think they hear a call to the priesthood when what they really hear is a tiny voice whispering "It's indoor work with no heavy lifting". |
#16
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#17
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On Thu, 04 Dec 2003 18:58:52 -0500, "Jay Somerset"
wrote: On 04 Dec 2003 14:50:32 GMT, (COUGARNFW) wrote: Amazing...all those answers by 172 owners and no one of them went to the net to find the "truth". If you go to Google and fill in "Airworthiness Directive for 172 fuel system", you will get a string of answers and some really foolish conclusions (like this string) that are worth reading. Just tried that -- the only one that came up was your post. Are you guys talking about AD 72-07-02? The text is he http://www.airweb.faa.gov/Regulatory...D?OpenDocument Don |
#18
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"Tony Cox" wrote in message thlink.net...
"Koopas Ly" wrote in message om... The only time that fuel is set to one particular tank is on the ground. I've never used fuel from only one tank in flight. Why would someone do that? Some models of 172 *require* you to select a single tank above 5000', due (supposedly) to vapor lock problems. Check your POH. Lots of old pilots didn't trust fuel gauges, which is still a wise attitude. They'd sometimes fly on one tank until it ran dry and the engine quit, then switch to the other and know exactly how much they had left and how much they'd burned. This doesn't work well if the tanks are very far off the airplane's centreline, as the imbalance can require increases aileron input, causing more drag and tiring the pilot. It can also panic passengers and create unpleasant cabin odors and extra janitorial work after the flight. Dan |
#19
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Lots of old pilots didn't trust fuel gauges, which is still a
wise attitude. They'd sometimes fly on one tank until it ran dry and the engine quit, then switch to the other and know exactly how much they had left and how much they'd burned. I'm an old pilot, don't trust fuel gauges and purposely ran a tank dry...only once...scared the hell out of me and my wife. Never did that again. :-) (Longer story, but that's the short version.) |
#20
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Not really related to 172's, but our RV-6 has no "both" position...
either left, right, or off. You just have to remember to switch them occasionally. Also, IIRC the 150 has just "on" and "off". There is a significant difference here between low wing, and high wing designs. If you have a low wing aircraft, and have a 'both' selector, if one goes empty, air is sucked into the system by the fuel pump, and fuel delivery stops. Hence low wing aircraft with a 'both' position, have to have a central 'sump' from which the fuel is drawn. On high wing aircraft, where the fuel is delivered by gravity, if one tank goes dry in the both position, fuel will still feed from the other. Hence 'both', is relatively unusual on low wing designs, but more common on high wing planes. This is why your RV6, doesn't have a 'both'. Ok, that makes sense now... thanks |
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