C172 Fuel Management

[wishiwasupthere]

Howdy all. Have recently started flying Cessnas after doing most of my flying to now in low wing aircraft. In low wing aircraft I switch between tanks every 30 mins. Whats the deal with Cessnas? Leave the selector on 'BOTH' or switch between tanks every 30 mins as per low wing aircraft?

Interested in your thoughts.

[Wanderin_dave]

Leave it on 'both'. Simple! :ok:

Oh and keep the ball in the middle or the fuel will head 'downhill'

Oh and if you park it on a slope with full tanks don't expect the tanks to be full in the morning (fuel transfer itself to the down hill tank and out of the vent (there's a wee little pipe between the tanks to allow to the fuel to move between the two tanks)).

My 2 cents.

[Alex 009]

With a 172 it is very simple: just leave on both. But as previously mentioned, keep the ball in the middle!

[wishiwasupthere]

Thanks gents. Just as I thought. Just out of interest is it pretty much the same for other Cessna singles (182, 200's)?

[Alex 009]

Can only really talk of the 185, and that doesn't have selectors for the tanks.

[kongdong]

Our company has a few 210's and they can vary. One has the fuel selector mod with a 'both' position, the others just have left or right. Curiously, even though in the fuel system schematic there isn't any crossfeed pipe between the tanks, the fuel still seems to find it's way from one tank to the other if you leave it on a slope, despite the fuel selector being off :} If anyone can correct me please do so, it has me very confused!!

[goldypilot]

unless ur flyin a 206 or what ever that has OFF, LEFT or RIGHT. there isn't a both. so yer do your thing(30min or 20min on each tank) what ever works for you.

Keep the shinny side up
GP

[Capt Fathom]

Whats the deal with Cessnas? Leave the selector on 'BOTH' or switch between tanks every 30 mins

Doesn't anyone read the POH anymore?

[Peter Fanelli]

Curiously, even though in the fuel system schematic there isn't any crossfeed pipe between the tanks, the fuel still seems to find it's way from one tank to the other if you leave it on a slope, despite the fuel selector being off


On a Cessna with a "both" position when selected OFF the two tanks are connected through the fuel selector itself. Imagine a T shaped pipe with the engine at the bottom of the T and each tank on one side of the top of the T. Rotate the whole T 180 degrees and the engine is now isolated from the tanks, but the tanks are still connected together, just at the opposite sides of the T.
That's why the 182 checklist calls for selecting the right tank when securing the aircraft, it disconnects the two tanks.

[The Green Goblin]

With a pretty complex fuel system like a C172 you really need to be on the ball. It has a myriad of different fuel settings and if you cock it up the aircraft does not glide very well so your options become somewhat limited.

I suggest at least gaining 1000 hours in a similar aircraft such as a 152 until you get on top of the fuel systems complexities before you tackle something like the 172.

You should then at least do 10 hours dual with an instructor to complete the C172 type endorsement and some duel cross country time focusing specifically on fuel management before you even suggest taking off as PIC.

It is also pretty easy to get behind the aircraft due to its excessive speed and the difficulty an aviator has in slowing it down enough to extend the flaps in the circuit. The last thing you need to be doing is worrying about the fuel system in such a complex high speed aircraft. :E

In all honesty leave it on Both convert the tank contents to minutes and log your "on time" and every 30 or so minutes reduce the endurance by that amount!

Safe flying!

[FL170]

Thank god your not flying a Tobago, where the little frenchies at SOCATA decided to position OFF between LEFT and RIGHT on the fuel selector, with no detent to know if you have selected your desired setting.

When it comes time to switch tanks my method is this; FUEL PUMP -- ON, FIELD -- SIGHTED, BREATHE -- DEEP, TANKS -- CHANGE EXPEDITIOUSLY

And hope for the best..:ugh:

After saying that, how many hours should one accumulate before attempting such a complex system GG?? :p

[D-J]

After saying that, how many hours should one accumulate before attempting such a complex system

Errr it's French, if you have more than one your over qualified..... :rolleyes:

[eeper23]

Is this a wind up? Just put in full tanks and dont fly for more than 5 hours. :uhoh::\

[The Green Goblin]

I prefer to fill the tanks that are already in the aeroplane as opposed to putting in a set of full tanks. They are pretty heavy eeper and Mr cessna made it pretty hard to open the wing!

[flypy]

Yup 206 will need to be cycled, but 182s and 172s can be set and forget.

Green Goblin, cracked me right up mate.. 1000 hrs in a 152, wouldn't wish that on anybody.

[eeper23]

Sorry I should have explained better. I mod my wings and seal the fuel caps so I cant leave them off when I go flying. As a result, if I need to re-fill my tanks, I need to put in new tanks. Hope this helps. If you are interested in a c172 endorsement, let me know!

[j3pipercub]

eepr, how much for the type rating? I can get it pretty cheap out of Hawaii with the exchange rate...

[eeper23]

j3pipercub, from your lack of experience in high powered single engine aircraft, im going to quote you 25hours dual for the endorsement. My going rate is $400/hr + $50 for your logbook sticker.

[j3pipercub]

Not bad, but I can do it in the states by buying a box of wheaties...:}

hat, coat, door

[baron_beeza]

When it comes time to switch tanks my method is this; FUEL PUMP -- ON, FIELD -- SIGHTED, BREATHE -- DEEP, TANKS -- CHANGE EXPEDITIOUSLY

And hope for the best..

FL170 said it.... and I agree.

Changing tanks would have to be one of the riskiest manoeuvres in General Aviation.

I always need to have a very good reason to change in flight and even then with a suitable field in sight. (and I mean road access etc). As a LAME and CPL I have seen so many aircraft come to grief needlessly.
Some of these fuel cocks and the likes need continual maintenance... nothing can be taken for granted. All the more so on an aging aircraft.
Personally I think changing tanks every 30 mins is madness. At least look out the window before placing your hand on it.
So many pilots assume moving the selector will work flawlessly...... all the time.
More likely a lottery to engine failure in my eyes.

[A37575]

Some of these fuel cocks and the likes need continual maintenance... nothing can be taken for granted. All the more so on an aging aircraft

Through poor instruction or sheer laziness, most pilots never turn off the fuel valve on the Cessna 150/152. By leaving it ON at all times, the valve eventually jams itself solid and you can't turn it off without breaking the shaft. Shame if you can't turn it off if the engine catches fire or you have a forced landing. Try writing up that defect in the maintenance release and hear the screams of protest from the owner.

[baron_beeza]

Exactly.... the C150 is a classic.......
and the students are still taught fuel off on EFATO.
The last thing these guys will ever see will be their hand trying to force that lever.

fly the aeroplane..... save your life

pretty easy checklist

[PA39]

A little off track, but the answers always amazed me when i asked pilots of all levels to explain the difference between the POH and the FM. Soooo many didn't have a clue. gets back to the training....and personal interest. Guys and gals we had on line would come to me and ask a question about a certain aircraft, which was the easiest way out. I would always say "Go and find it in the book!". If you can't find it come back to me and we will both go through the book together, until you find it. Studying the POH and FM is an absolute MUST for each type/model of aircraft.

[goldypilot]

good call PA 39. that is the way

[Polymer Fox]

I've just moved from flying an Archer to C172s recently and I'm very glad that I don't have the misfortune of having to change tanks anymore. One of the scariest moments I've had would have been watching the fuel pressure slowly trickle down after swapping tanks just after take off from Goulburn.

However, on the other hand, fuel management awareness can dimish seeing that you don't have to monitor which tank you've been on and for how long. Never really did like the idea of "set and forget".

[The Green Goblin]

Never really did like the idea of "set and forget".

If you 'set and forget' you are begging for a fuel exhaustion scenario.

There is no difference between your previous type and the C172, every thirty or so minutes you still update your fuel log reducing your endurance by the appropriate amount. The only difference is you don't swap tanks in the process.

Safe Flying :cool:

[Indianzz]

One of the scariest moments I've had would have been watching the fuel pressure slowly trickle down after swapping tanks just after take off from Goulburn.

I have read this thread with increasing frustration and agree with all who state that the POH and FM are the correct sources for this information.

BUT what astounds me about the above comment is why on earth would you want to even think about changing tanks "just after takeoff" - unless of course you were suffering a possible fuel related engine problem - but Polymer's post does not indicate this.

I'm not trying to be a smart ass here but this thread does suggest some pretty poor training or at least comprehension of basic airmanship and tech knowledge.

Indianzz

[Ex FSO GRIFFO]

G'Day Indian,

On some aircraft I have flown, the 'taught' procedure was to T/O on "Both", then, when at a safe altitude, change to either the left or right tank for 'fuel management' and 'trim' purposes.

In early Bonanzas, beware the fuel return system from the fuel distributor valve - it was returned to the LEFT tank only....so if you selected the right tank for engine use, the 'excess' was returned to the left, until it was FULL again, and then it 'conveniently' drained out over the side via the underwing vent - just where it would not be noticed.....
So, obviously the 'trick' there was to use the left tank for a 'good hour or so', then use the right tank for an hour, and 'lo and behold' the LEFT was almost full again!!

But of course, as we had all 'been endorsed on type' in dem dere days, we knew this - it was 'drummed' into us - and, it was in the book!;)

They've fixed that little anomoly now, so you don't have to worry about it anymore....:D

Cheers:):)

[glekichi]

Some suggest that you should switch tanks every 30 so that if one was to become unusable for any reason, then you find out about it while you still have plenty in the other tank. The theory goes that if running on 'both' you wouldn't know until the good one ran out of fuel.

So, has anyone actually every heard of a C172 tank becoming blocked, etc.?

[The Green Goblin]

The theory goes that if running on 'both' you wouldn't know until the good one ran out of fuel.

You'd soon know with a large split in the fuel gauges and a wing low tendency :ok:

[glekichi]

Typical C172 fuel gauge:
LEFT ---- RIGHT
http://madsenworld.dk/anigif/music/vu_meter.gifhttp://madsenworld.dk/anigif/music/vu_meter.gif

C172s that fly straight?
:}

[Indianzz]

Ok my final 2 cents worth on this thread.

Too many years ago when learning to fly the very forgiving PA28-140 the fuel management was this - and a confession - I cannot tell you what the POH says because this it what the instructors drummed into me!

Always start the engine off the tank with the lesser quantity of fuel - if applicable.

After start change to the highest (or other tank) - the idea being that for take off you were using the tank with the most fuel and if there was a blockage or flow problem it would manifest itself prior to takeoff.

After that change tanks every 30 minutes - fuel pump on - change tanks - record change in flight log - fuel pump off.

Did this VFR or IFR - for IFR it was "mandatory" in so much as it was part of the regular cruise checks.

Never suffered a fuel related problem which of course was a combination of good luck (no mechanical pump failures etc) and good fuel management.

Safe flying.

Indianzz

[SM227]

When I learnt in the 140, it was fullest tank for take off and landing, change tank 30 min after take off and then every hour after that. When its only using 30lph (22kg) their really isnt much point changing evey 30min, never any balance issues, and like the others have said, its less times your changing tanks in-flight and risking a problem arising. I too never saw its POH (I now know thier value :ok:), anyone know what piper reccomend?

[baron_beeza]

Some suggest that you should switch tanks every 30 so that if one was to become unusable for any reason, then you find out about it while you still have plenty in the other tank

The reason the fuel is unusable will be because the cock has jammed, fractured, sheared off........it really is the weak point in the fuel system. Well the gascolator is of major concern also of course. - they literally are hanging in there by a thread...... and a very sloppy one these days. These items are all that a seperating you from a fuel starvation issue.

change tank 30 min after take off and then every hour after that. When its only using 30lph (22kg) their really isnt much point changing every 30min, never any balance issues,

I do basically that. fly until the end of the good terrain on the right tank (20 or 30 mins), change at the last landing point..... and then fly the remainder on the left tank.

On a Tomahawk that is 2 1/2 hours flying.... changing only once, no imbalance issues and I know that the 2 plus hours in the right tank is still there.

Crossing any large body of water requires a little planning, I plan the fuel management about that. Basically doing the change to the full tank at least 5 minutes prior to leaving land...... and touching nothing until reaching land again.

Some aircraft have notoriously unreliable fuel systems...... I have seen guys setting off on ferry flights in the likes of an Islander and returning because the tip tank valves didn't operate. Sure the little electric switch clicked up.....

I was thinking about all the flying instructors I have met or flown with..... and then judged their knowledge of the fuel system. I suspect there was one that knew his aircraft.....
Don't start me on some of the others. A schematic in a POH is exactly that...a schematic, simplified, - and still some would struggle with it.

I have yet to meet a 'bad' pilot.... could it also be that 'good' fuel management is actually not that CRASH hot also.

I do know I got a got deal on an aircraft purchase after a PPL showed his proficiency in fuel mismanagement and precautionary landing techniques.....
Brilliant.

[Capt Fathom]

33 responses on how to manage the C172 Fuel System!

Sheez! You people need a real fuel system to mull over!

C310/400 series with 6 tanks? Queenair with 4?
Beaver? MU-2?

That should keep the debate running! :ouch:

[A37575]

Sheez! You people need a real fuel system to mull over!


The real nasty is the Partenavia. The fuel valve has several selections and even with a new aircraft the valve operation is abnormally stiff to operate. Eventually it seizes and the problem is in the linkage at the engine end. Because few pilots turned the fuel valve off, the inevitable jamming in the linkage goes unnoticed. Then it becomes impossible to select fuel off or crossfeed.
During the servicing of one Partenavia in Melbourne the LAME attempted to turn off the fuel valve of each engine . It was impossible. The defect was reported to CASA who issued an AD which basically said pilots must write up the defect if the fuel valve was abnormally stiff to operate as it would steadily get worse. In addition the fuel valve must be checked for normal operation at each 100 hourly. Either the LAME's use both hands to turn the valve (and then say it is serviceable) or they just tick the box, I can't say. But the prevalence of seriously jammed fuel valves in the cockpit of Partenavias is proof that some pilots and engineers are ignoring the point of the AD.

In UK, a female pilot had an engine failure in a Partenavia while over the sea. She was unable to move the fuel valve because it was jammed so badly. She was forced to ditch and two passengers lost their lives.

[Polymer Fox]

One of the scariest moments I've had would have been watching the fuel pressure slowly trickle down after swapping tanks just after take off from Goulburn.

I have read this thread with increasing frustration and agree with all who state that the POH and FM are the correct sources for this information.

BUT what astounds me about the above comment is why on earth would you want to even think about changing tanks "just after takeoff" - unless of course you were suffering a possible fuel related engine problem - but Polymer's post does not indicate this.

I'm not trying to be a smart ass here but this thread does suggest some pretty poor training or at least comprehension of basic airmanship and tech knowledge.

Indianzz

No apologies for being a smartarse required. You're quite right about the fuel issue. I've not really worded my response properly and that can mean dire things on an aviation forum as I've now found out.

I was established at the cruising level after take-off and completed the fuel swap during my top of climb checks.

[PA39]

Scareostar with belly tank and twin comanche with tips.....oh the fun of it all !

[j3pipercub]

You'd be the right person to ask PA39,

But in the Twin Catastrophe the tip selectors are electric are they not? and once selected, if and electrical failure occurs you are stuck out on the tips?

[goldypilot]

My remote control cessna 172. (model of course...) is battery operated. what should i do? it doesnt have left right or both coz its battery. arrrrrhhhhhhhh Please PM me if u have an answer. after reading this i might have to call casa or my old instructor and ask for help???? After flying it years ago i need HELP

[baron_beeza]

Yep, we may laugh but I get to see many pilots during the working day ....
with the C172 many have no idea on venting, cross feeding and uneven fuel supply.

What really concerns me is the willingness to accept the aircraft as fit to fly during the pre-flight inspection.

Sure all the info is in the books, - it is the interpretation and judgement that concerns me.


You then talk to an instructor and it is soon apparent why.

I really do believe we need to factor in some modern thinking and take into consideration these books were written over 30 years ago, - and the aircraft are no longer new.

I am sure many of the guys that have been in the industry for a while can all recall aircraft, and friends, that are no longer about.... often due to some basic or fundamental flaw.