Preflighting an airplane is the only way you can be reasonably sure that the plane is safe to fly. One of the critical things that must be checked before you climb into an airplane to fly is the fuel.
There is one obvious reason to check the fuel – to find out if there IS any! Have you ever run out of gas in your car? That’s always a bummer. It is decidedly more inconvenient in an airplane, since there is no way to just “pull off the road.” So one of the first things we did when we walked out to the airplane and started our preflight in the first place was to take a look in the fuel tanks on the wings and see if we needed fuel. That way, if we did need the tanks filled, we could call for the fuel truck, and that could all be happening while we did the rest of our preflight.
Here’s the thing about fuel level for flying: According to the Aircraft Owners and Pilots Association (AOPA), an average of two accidents PER WEEK happen due to fuel mismanagement. This is absolutely unacceptable, because it is completely preventable! know how much fuel you have on board, how much time that give you (yes, TIME, not distance), and plan on twice the reserve the FAA requires. For goodness sake, people, this one is EASY.
Setting down my soapbox on fuel exhaustion for a moment, there are a couple other reasons and ways that we check the fuel on an airplane, and the amount of fuel on board is only one of these reasons.
Reason number two is to make sure there aren’t any contaminants in the fuel that could clog up the system or otherwise cause fuel starvation. Fuel starvation is a situation when there is fuel in the tanks, but it can’t get to the engine for some reason.
And then reason number three to check your fuel is to make sure that the correct fuel is in the tanks! In your car, this is not really thought about much – most cars run on unleaded gasoline, and as long as that is what you put in it, the octane or additives don’t really matter much. Not so in a plane.
So let’s walk through this a step at a time:
- Fuel Amount
- Fuel Quality
- Fuel Type
Fuel amount is easy, simply open the lid to the fuel tank and peek in, right? Kind of. If your tanks are completely full, you’ll easily see this, but what if they aren’t? There are a couple of ways you can find out. Some airplanes have a “fuel tab” or “collar” that indicates a certain amount of fuel in the tank. Your Pilot’s Operating Handbook (POH) will tell you if this is the case for your airplane, as well as how much fuel you have if your tanks are filled to this tab or collar.
Another – better – way to tell how much fuel is on board is to have a simple tool that will tell you how many gallons of fuel you have on board. These tools are made for specific aircraft types and models, and are easy to use – in fact, they operate on a principle that you’ve been using since you were a kid, when you put your finger on top of your straw and pulled it out of your drink. The level of drink in your straw stayed in there – and if you use one of these, so will your fuel level. The markings on the tube tell you exactly how much gas is in the tank. Add together the amounts in each tank and you have your total amount of fuel currently on board. They make a universal one that you can calibrate for pretty much any plane. Just don’t drop them in the tank! No, seriously, don’t.
Speaking of dropping things in the fuel tank – let’s talk about fuel quality now. Using other tools, like this GATS Jar or some other fuel testing device, you will sump the fuel tanks to see if your fuel has “floaties” or water in it. I hate it when I have floaties in my drink when I go out to dinner (it always seems to happen to me). I hate it worse when I have floaties in my fuel tank. Depending on the plane you fly, you’ll have anywhere from 1 or 2 up to 13 or more sump locations to check. Sump enough fuel to make sure that there are no contaminants or water from each sump. If the fuel is clean (and you have the above mentioned GATS Jar), you can put the fuel back in the tank – saving you hundreds or thousands of dollars over time. If there are contaminants, though, dispose of the fuel.
How will you be able to tell if there is water in the tank? Well, aviation fuel is colored (we’ll talk about that presently when we talk about fuel type), so if you sump clear fluid from the tank, it’s not fuel. Or at least not the right fuel. Keep sumping. If you see clear at the bottom and a color above (in two layers), that’s water at the bottom. Dump the fuel and sump again until there is no more water coming out of the tank. If you keep sumping and sumping and it feels like the water or contaminants are never going to end, it’s time for a mechanic… the tank may need to be drained and the source of the water or other contaminants needs to be found. Don’t fly!
Now, let’s talk about fuel type. For aviation, there are four main types of fuel:
- 80/87 Octane
- 100/130 Octane
- 100LL (low-lead)
- Jet A
Each of these fuels is color-coded:
- 80/87 is colored RED
- 100/130 is colored GREEN
- 100LL is colored BLUE
- Jet A is “straw-colored”
It is critical to know what kind of fuel your airplane uses, and NEVER use a lower octane fuel in your tanks.
Today, you are very unlikely to ever see anything except 100LL and Jet A at any airport you fly out of. You can always burn higher octane fuel (so if your plane calls for 80/87, you can use 100LL), but never lower, and NEVER use Jet A (or any other jet fuel) in an engine that calls for gasoline. Believe it or not, Jet A is lower octane than all the others. It is essentially kerosene, though cleaner and better refined.
By the way – 100LL (or any of the other non-jet fuels above) is referred to as “Av-Gas.” Some aircraft are allowed (through a process of approval by the FAA called Supplemental Type Certification (STC)) to burn regular automotive gasoline (called “Mo-Gas” in aviation parlance). Again – know your airplane. Mo-Gas will not be colored like Av-Gas is.
So that is pretty much your preflight! If you started with us late in the series, there is a list below of the entire process, 3 steps (over 5 posts) walking through the walk-around and preflight process. Hopefully this series has been helpful for you – I know it always helps me to get it out of my head and written somewhere!
Do you have anything to add to the fuel part of the preflight series? Drain your brain in the comments to tell us anything I might have missed or tips and tricks you’ve picked up along the way!
Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.