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View Full Version : whats the point of the fuel selector in c152?


fudgy2000
24th Mar 2004, 15:10
Whats the point of the fuel selector in C152s etc. Its always on the "both" selection anyway. Is there any time when you have to turn it to L or R tanks??

ferrydude
24th Mar 2004, 15:26
Is there a "both" position on the C-152? I seem to recall either on or off only. If you had an engine fire, you reckon that "off" position might come in handy?

HiSpeedTape
24th Mar 2004, 15:37
My C152 (II) only has on and off postions!

silentwitness
24th Mar 2004, 15:43
Is it not so you can check both tanks are working (eg taxying)? You might have both tanks full, but if only one works.......

maggioneato
24th Mar 2004, 15:54
Mine only has on and off. 172 I used to fly was how you describe, have never seen a 150 or 152 with that choice.

FlyingForFun
24th Mar 2004, 16:37
Notwithstanding the fact that no one here seems to have seen this on a C152, I'd venture that it can be useful on a C172, which does have a L and R option as well as a Both option. For example, a rough running engine might be cured by selecting L or R if the cause of the rough running is fuel contamination one tank only. Also, the POH recommends setting it to either L or R when parked - leaving it on Both will cause some cross-feeding due to gravity, and the tanks will not be balanced when you return to the aircraft (I don't know how, or if, this is avoided on a C152 which only has Both and Off positions?)

FFF
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fudgy2000
24th Mar 2004, 17:20
sorry guys it may be a c172 i am talking about!!!!


I recall someone telling me that if the fuel selector is in both position when you come to fill the tanks, the fuel drains in the other one, therefore your never going to get full tanks. not sure if this is correct??

RatherBeFlying
25th Mar 2004, 02:04
But it's easier to just refuel the lower tank first. After filling the upper tank and then filling the lower tank with the fuel selector on both-172 or on-150/2, the resulting fuel outflow from the lower filler outlet once the lower tank is filled will reinforce remembering the better procedure.

This phenomenon is very hard on smokers:E

If you leave the fuel selector off on a 172, the engine only runs for about 15 seconds -- did that once too:)

boofhead
25th Mar 2004, 02:39
Depending on the fuel cap and pressure relief, at high altitude and low power there might not be enough fuel flow to keep air flowing into the tanks which can cause a stoppage of the fuel to the engine. If you use one tank at a time the fuel flow from the single tank is greater and will allow for uninterrupted flow. Also another reason why you switch to one tank following engine failure, since if this was the reason it will restore fuel flow and therefore power. There used to be a warning on this in the POH.

Hudson
25th Mar 2004, 07:55
There is a design fault in the fuel valve selector in the C150/152 aircraft that you should be aware of. Unless the selector is exercised regularly by selecting OFF at the end of a flight, it eventually becomes stiffer to operate over several months and finally seizes up.

Most flying schools leave the fuel selector on at all times and thus the binding or jamming is not picked up. Then if an attempt is made to turn off the fuel selector as in an engine fire or engine failure, it stays jammed on with possible disasterous consequences.

From my experience this defect is rarely picked up during routine maintenance. Or if it is picked up, shoulders are shrugged and the owner refuses to have it rectified as it will cost money. The aircraft then continues to fly in an unairworthy condition.

Oktas8
25th Mar 2004, 09:34
Once flew for a while with one fuel cap off in a C172.

[Pause for inevitable insults.]

Putting the tank selector to one tank prevented all the fuel from both tanks from siphoning out of the open cap.

Happily, I lost no fuel apart from normal burn-off.

On another note, is the on-off valve of a 152 not downstream of the left-right tank junction? So selecting fuel off will not prevent fuel from going from upper to lower when parked on a slope.

O8

FatFlyer
26th Mar 2004, 03:57
If I remember rightly, the flight manual for a 150/152 says that for maximum fuelling it is necessary to fill one tank, then the other, and then top up both as fuel runs from one to the other.
Also the 172 manual syas above a certain alt ?6000ft to select either L or R and not both

SeldomFixit
26th Mar 2004, 09:11
No wonder they gave up producing those darned 4 seat C152's - wayyyyyyyyyyyyyyyyyyyyyyyy too complicated :ok: