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PostPosted: Fri Feb 02, 2018 4:57 am 
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Airman Basic

Joined: Fri Feb 02, 2018 4:26 am
Posts: 5
Hi there,

I'm a new (virtual) PA24-250 pilot and I have a question with regard to the fuel management during flight.
In general I simply would like to know what is the real-world best practice during the different flight stages and when should I use which fuel tank?

To be more specific about it:
1) Are there any balance or load limitation between:
* fuel quantity in the right vs the left main tanks
* fuel quantity in the right vs the left wing-tip tanks
* fuel quantity in the main tanks vs the wing-tip tanks

2) When exectly to use the electrical fuel pump?
* Should I turn it off after the engine is running? maybe only after take-off? another stage?

3) In which order should I use the fuel? Should I use the the tip-tanks first?

4) Should I use the tip-tanks also during: startup, taxi, take-off, landing?

5) Should I use the fuel selector in flight on "both" or is it better to use only 1 tank each time?


Thanks and lovely greetings

BlueThing


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PostPosted: Fri Feb 02, 2018 9:52 am 
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A2A General
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Joined: Wed Feb 11, 2004 12:55 pm
Posts: 14816
Location: USA
Hi Blue and welcome to our community,


1) Are there any balance or load limitation between:
* fuel quantity in the right vs the left main tanks
* fuel quantity in the right vs the left wing-tip tanks
* fuel quantity in the main tanks vs the wing-tip tanks

I am not aware of any limitations but in practice, it's at least recommended to burn your tip tanks first, then the mains. You also don't want to have a big load diff between left and right tanks to avoid having a heavy wing in flight. Some burn one tank at a time (and consider this the right way to manage fuel so you can verify fuel available) and others burn both left and right together. If my fuel was ever very low in the mains, however, I would resort to burning one tank at a time if not already, because if one goes dry it can prevent the other from feeding the engine if both (the dry and wet tank) are selected. Also, with the tip tanks, the fuel gauge roughly reads 2x how much fuel is available (F = 1/2, 1/2 = 1/4, 1/4 = 1/8, etc.). This is how it is in our Comanche 250 and since we modeled our airplane, it's like this in the sim. So, when a tip reads just below 1/4, I stop and then leave it as an emergency reserve.

2) When exectly to use the electrical fuel pump?
* Should I turn it off after the engine is running? maybe only after take-off? another stage?
As a general rule, I don't think "use the electric fuel pump on takeoff or landing" but rather "use the electric fuel pump whenever I am low and I can't glide to safety if my engine quits." I also think you are supposed to use the electric fuel pump when switching tanks.

3) In which order should I use the fuel? Should I use the the tip-tanks first?
Yes

4) Should I use the tip-tanks also during: startup, taxi, take-off, landing?
No

5) Should I use the fuel selector in flight on "both" or is it better to use only 1 tank each time?
I think I addressed this above. It's personal preference, but better practice is one at a time

Also, for whatever it's worth, when burning tips I burn like this:
15 min left, 30 min right, 30 min left, 30 min right, etc.

Scott.

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PostPosted: Sat Feb 03, 2018 6:37 am 
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Airman Basic

Joined: Fri Feb 02, 2018 4:26 am
Posts: 5
Dear Scott,

thank you very much for taking the time and writing a detailed explaination.
(I'm used to bigger planes, where fuel balance is critical and can be even deadly if not handled correctly)

One thing got me a bit confused:
"the fuel gauge roughly reads 2x how much fuel is available (F = 1/2, 1/2 = 1/4, 1/4 = 1/8, etc.)"
so just to confirm I got it right:
Needle on F (Full) = 15.00 galons (in both tip tanks together)
Needle on 1/2 = 7.50 galons (in both tip tanks together)
Needle on 1/4 = 3.75 galons (in both tip tanks together)
Needle on E

Is that what you meant?

Thanks again

BlueThing


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PostPosted: Thu Feb 08, 2018 2:15 pm 
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Senior Airman

Joined: Sat Dec 13, 2014 11:38 am
Posts: 216
Location: Vancouver, BC
Hello:

Regarding the tip tank question - the tip gauge shows the fuel remaining in the selected 15 US gal tip tank. If you are drawing both tanks together, and they are being drawn down equally, then the fuel gauge shows how much fuel is in either tank, regardless of which one it is switched too. However, your initial confusion here is one component of why I recommend that you draw fuel from one tank at a time.

I also draw each tank completely empty and do not leave a bit of fuel around as a reserve. In an emergency, you do not want to be switching around between tanks looking for a bit of fuel that might only last a few minutes before making you switch tanks again. Also, fuel in the tips isn't supposed to be used while maneuvering near the ground, which might be required in an emergency.

I find that it does not take much fuel imbalance in the tips to be irritating while flying. I tend to burn the tips first, and switch them frequently, as Scott suggested. 15 min initial on one side, and then 30 minutes alternating until empty. Sometimes more often if it is bugging me.

The POH and STC has recommendations/requirements on which tank to use. The STC for the tip tanks says they can be used in level flight only. For take off and landing the POH recommends that you use the fullest tank, or if they are the same (and I might be remembering this wrong) the left tank. I generally default to the left tank for takeoff as then I have one valve to check in an engine off situation, or one valve if I have to shut it off for a forced landing, and it is always the same one. No thinking or groping around on the floor when very distracted.

Use the electric pump before startup to prove it works and then shut it off. Startup, taxi, and run-up using the engine pump, on the left tank, and don't switch tanks on the ground. You now know you have 26 gallons of usable fuel in the left tank. Use the electric pump for takeoff and don't shut it off until you get high enough to return to the airfield if the engine quits when you shut off the electric pump. Or you are high enough to glide long enough for the engine to restart on its own if a vapor lock stopped the main fuel pump (or carburetor float bowl) from working. Switch between the remaining tanks soon during the cruise phase to ensure all four are feeding freely. The known and proven and feeding 26 gallons in the left tank can get you to an airfield if there are problems revealed during the cruise check.

Last tip: shut off the electric fuel pump without looking at the switch. Don't take your hand off the switch. If the engine coughs or splutters in the first few minutes you can switch it right back on instantly.

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PostPosted: Wed Feb 14, 2018 8:33 am 
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Senior Airman

Joined: Sat Sep 07, 2013 6:42 am
Posts: 142
Location: East Midlands
Absolutely best topic on the internet! I fly exactly like how Scott recommends and possibly fly's his real Comanche so that fills me with confidence that I'm as real as one can be.

I get a lot of questions regarding fuel pump and fuel management during my streams and people have questioned my reasoning. So now I have some more feedback :)

There is a real world pilots manual knocking about on the internet and I've used that for most of my flying.

Thanks for a superb response guys.
Jim

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