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Preflight: Step 3 – Fuel

Fuel Pumps

Kiril Havezov

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:

  1. Fuel Amount
  2. Fuel Quality
  3. 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:

  1. 80/87 Octane
  2. 100/130 Octane
  3. 100LL (low-lead)
  4. Jet A

Each of these fuels is color-coded:

  1. 80/87 is colored RED
  2. 100/130 is colored GREEN
  3. 100LL is colored BLUE
  4. 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.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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Preflight: Step 2 – Exterior (Engine)

Engine Cowling & Propeller

Last post, we left you finishing the preflight of the tail, or empennage, section of the plane. We checked the vertical and horizontal stabilizers as well as the rudder, elevators, trim tab, and all the hinge bolts.  We also checked the antennaes, and then moved forward on the right side of the plane to check the right wing, the same as we did when we preflighted the left wing.  This puts us at the front of the plane, ready to check the cowling, engine, and propeller.

NOTE: the specifics in this series apply to Cessna 172 aircraft, as that is what I instruct in most – in any case, always use the Pilot Operating Handbook (POH) for your aircraft to confirm that you have not missed anything on your preflight!

Now for the right side of the engine cowling and the front of the plane.

On the right side of the cowling, there is an access door where you can check the engine's oil level - open this up and unscrew the dipstick. Different engines have different oil capacities, so check with an instructor and read the POH for your particular plane. Add oil if necessary - make sure you add the right oil type. Check with your instructor or a mechanic if you are unsure.  While you are in here, take a look at the hoses and wires you can see, and make sure a mechanic didn't accidentally leave a tool or rag in there somewhere!

Duck down at this point to look at the nose gear. You should see a few inches of silver on the strut - too little brings the propeller too close to the ground and is dangerous. I tell my students to look for 3-4 finger-widths of strut to be showing. Look also at the shimmy-dampener (this looks like a small shock absorber mounted sideways), and look at the strut's "scissors" and collar for cracks or broken bolts. If these look broken, the plane should not be flown.  While under here, do you see any fresh oil on the ground? If so, the engine may be leaking - that's a no-go situation.

Moving to the front of the plane, run your hand along the edge of the propeller, looking for any dings or cracks that could weaken the prop. Grab the propeller at the base (near the middle, on both sides of the spinner) and tug. There should be no give. Check the crews in the spinner itself for any missing ones. Look inside the cowling at the engine itself - are the cooling vanes broken? Are there plates in front of the engine that are cracked and loose, or do they all look secure? Has a bird built a nest in the front of the cowling? Look for the alternator belt and reach in and tug lightly on it - it should give just a little, but be pretty taut in general, and not be worn or frayed.  You should also be looking here for tools or rags that may have been left inadvertently if the plane came out of maintenance recently.

The air filter (bottom front of the cowling) should be relatively clean and not blocked by anything.

Look at the nose gear from the front to get a different perspective on it.  Again, check the collars and scissors from this angle for cracks.

Now move back to the right side of the cowling (where we started). Take another look at the static port (it never hurts to check twice), and then look at the nose gear from this side as well for issues with the collars and scissors and bolts.

If all is well, the exterior check should only take a few minutes. 10-15 minutes is not unreasonable when you are learning a new airplane, but you'll get faster as you get more familiar with the make and model of plane you are flying.

Once the exterior preflight is complete, we can move on to checking the fuel quality.  This is the last step before you fire up the engine and show gravity who's boss!


Do you do anything different on this part of the preflight? Add your tips to the comments!

Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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Preflight: Step 2 – Exterior (Tail)

Small Airplane Tail

Last post, we began working through the exterior part of the preflight, and we had checked the glareshield, static port, and left wing including the leading edge, trailing edge, aileron, and flap, and the  left main gear and brake.  This left us under the wing, ready to move on to the tail.

NOTE: the specifics in this series apply to Cessna 172 aircraft, as that is what I instruct in most – in any case, always use the Pilot Operating Handbook (POH) for your aircraft to confirm that you have not missed anything on your preflight!

From under the wing, after checking the left main gear, lightly knock on the fuselage as you make your way to the tail. When you get to the cargo door, check to make sure it is closed, latched, and locked. Keep knocking the rest of the way back. You are listening for a rattling noise that would indicate a loose screw or rivet. If a rivet starts coming loose it might start vibrating and creating aluminum dust, which trails back as the plane moves through the air, making it look like smoke is coming from the rivet; this is known as a "smoking rivet" and is a good reason NOT to fly a plane. Also watch for missing access panels.

Once you have reached the tail, look for dents and issues on its leading edge and on top, as well as missing or smoking rivets or lost access panels, and move around to the back where you can lift the elevator. Lift the elevator up on the left side, and check the elevator on the right side - it should also go up. Check the yokes (if possible) - they should move toward the back of the plane (aft) when the elevator is up, and toward the front of the plane (forward) when the elevator moves down. With the elevator down, check the hinge bolts to make sure they are secure and have safety wire.

To check the rudder, lift the elevator, and push the rudder away from you and pull it toward you, and take a look at the cables that pull the rudder for secure bolts and safety wire. You can also see the cables and bolts that move the elevator from this vantage point, so check them here as well. Also check any of the rudder hinge bolts you can reach (bottom and middle, most likely).

The right side of the tail has all the same checks as the left side with one major difference - the elevator trim tab is on this side of the elevator. Lift the elevator, and check the trim tab does not move very much. Check the bolt and safety wire on the trim tab pushrod. Then check the rudder from the right side and all the other elevator checks on the right elevator.

Once done with the tail itself, it is a good time to take a look at the antennae on the plane. You will probably see two antennae on the top of the vertical stabilizer, sticking out of each side of the tail at an angle, looking like the letter "V" laying on its back. These are the VOR antennae.

You will probably also see one or two antennae on the top of the wings, at an angle leaning toward the rear of the plane. These are communication antennae. You might see a "hockey puck" like antenna above the cockpit, near the comm antennae - this is a GPS antenna.

On the top of the fuselage is a thin, wiry antenna, just behind the rear window of the cabin - this is the antenna for the Emergency Locator Transmitter (ELT). You might see a "clothesline" wire from the top of the tail to above the cockpit. This is a Non-Directional Beacon (NDB) antenna (also called "Automatic Direction Finder" or ADF).

Under the fuselage are "fin" type antennae - these are antennae that belong to the transponder.

Move forward on the right side, knocking lightly on the fuselage, toward the wing, pretty much in reverse from what you did on the left side of the plane (see Preflight: Exterior - Part 2 (Wing) for a reminder!). Check the right wing just like you did the left wing, starting with the flap, then the aileron, wingtip, and leading edge. Once done, check the right main gear, just as you did the left main gear.

Once you've completed the right wing, it's time to check out the engine area and propeller - which we'll do in the next post!


Do you have anything to add to this part of the preflight? Add your tips to the comments!

Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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Preflight – Step 2: Exterior (Wing)

Piper Cherokee

In the first part of this series, Preflight: Step 1 - The Cockpit Check, we talked about starting your preflight in the cockpit.

But the exterior check in step 2 actually starts even before step one.  Confused?  Let me explain:

Every preflight really should begin as you are walking out to the plane.  Or - if you're lucky, as you enter your hangar, before you even touch the plane at all.

Is the plane leaning to one side or the other?  Does it look very tail-low or tail-high? Are there puddles of fluid under the engine cowling or at the main gear?  Are there stains on the wings or anything new that you never noticed before? Do you always lock the plane, but the door was open when you first look?  If you don't own your plane, some of the above things may not apply, but even if you rent, there are probably processes and patterns where if something is different, you'll notice.  If you ever have a question, grab a flight instructor and ask!

After this first look, do your cockpit check, and when that is complete, move on to the exterior check!  Because the exterior check is the longest part of the preflight, we'll break it up into 3 sections - wing, tail, and engine.

NOTE: the specifics in this series apply to Cessna 172 aircraft, as that is what I instruct in most – in any case, always use the Pilot Operating Handbook (POH) for your aircraft to confirm that you have not missed anything on your preflight!

I tell my students to step forward and out, putting them in front of the plane, to the left of the engine cowling.  From here, they can start by checking the cowling itself for loose or missing screws, checking the static port to make sure it is not blocked or covered by anything. This is also a good vantage point to look at the wind screen - is it dirty? Does it have bugs splattered all over it? Clean it before you go!

Now look up - at the leading edge of the wing at the wing root.  There is probably a vent here - check to make sure it is not blocked. Now run your hand along the leading edge of the left wing, looking for big dents that might change the wing's ability to create lift.  As you move from the wing root toward the wing tip, you'll run past the pitot tube - check all the openings/vents to make sure they are not blocked by anything (including a pitot tube cover).  Keep going to reach the stall warning opening - check to make sure it is not blocked.  If you have a suction tool, you can test whether it is working or not as well.  Keep moving toward the wing tip and check to make sure that the fuel tank vent is also not blocked, and the fairing for the wing strut is secure and in relatively good shape.  While checking all of this and the leading edge, you should also be checking the bottom of the wing for loose rivets or loose or missing inspection covers, or anything else out of the ordinary.

Once at the wingtip, just check the plastic tip cover for any major cracks (you may find small cracks that have been stop drilled, but those are okay), and make sure it is secure.  Now on to the trailing edge.

You removed the control lock during the cockpit check, right? If not - go remove it now, because we're going to check the ailerons.  First, push the left aileron up, and look over to the one on the right wing to make sure it is down. Also, if you can see it, check that the yoke turns toward the left while the left aileron is up (the yokes should always turn toward the up aileron).  Now push the left aileron down, and check the other aileron (which should be up now), and the yokes (which should be turned to the right now - toward the up aileron).

Now, hold the aileron up with one hand, and duck under the wing and turn around so you can look between the wing and aileron at the following:

  1. There should be three counterweights on the outside of the aileron, securely attached
  2. Three hinges, all of which should have secure bolts and safety wires, and none of which should be cracked or broken in any way.
  3. A pushrod, which will rotate a little, but the bolt should be secure - it should not be loosened or turned by your fingers.

Make sure you hold the aileron up with one hand and do these checks with the other! Even if the aileron seems to stay up on its own, even a slight wind could push it down and pinch your fingers - consider this the voice of experience telling you that THIS HURTS. Avoid this by learning from my mistake and holding the aileron up with one hand anytime you have your fingers in the gap between the wing and aileron!

You may also see one or two wires coming out of the back of the aileron - these are called static wicks, and they help protect the airplane and its electronics from static electricity and/or lightning strikes.  Just make sure that if the plane has any, that they are all there, secure, and in good shape.

Now continue moving inboard to check the left flap.  Push on it - it will give a little - maybe an inch or so.  Too much is a cause for concern.  If you are in doubt, ask your instructor or a mechanic.  Check the tracks - there will be two (one on each side of the flap).  Look at the rollers for cracking, wear, or other issues (including being gone completely!).  The tracks should have a little grease on them - not necessarily sopping in grease, but enough to let the rollers move smoothly.  Check the pushrod on the flap just like you did with the aileron.

Now that we've completed the left wing, let's check the left main gear.  Is it fully inflated? Are there bald or flat spots or belts showing from excessive wear?  Now roll the plane forward or back to see under the tire, too.  What about the brakes? Is there fluid leaking? Check the rotor for wear, and both pads (each pad should be at least as thick as two quarters pressed together).  Check the brake line for security, and the "bolt" to make sure it is not loose.

Once you are done checking the main gear, it's time to move back toward the empennage (tail). We'll talk about the tail in the next post in the series!


Do you have anything to add to the preflight series so far? Add your tips to the checklist by leaving a comment below!

Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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Preflight – Step 1: The Cockpit Check

I teach students to do preflight in 3 steps:

                    1. cockpit
                    2. exterior
                    3. fuel

Preflight should actually begin as you are walking out to the plane - does it look right? Is it leaning to one side, or sitting funny on the ramp? Do you see any fluid under the engine cowling or by the main landing gear? Then immediately upon reaching the plane, check fuel levels - that way you can call for fuel and they can come and fuel it up while you do the rest of the preflight.

NOTE: the specifics in this series apply to Cessna 172 aircraft, as that is what I instruct in most - in any case, always use the Pilot Operating Handbook (POH) for your aircraft to confirm that you have not missed anything on your preflight!

Step 1 really starts after that. Turn on just the battery side of the master switch, and listen for the electric turn coordinator gyro to start spinning up... it will sound like a computer fan. Then turn on all the electric switches (taxi light, landing light, nav lights, strobe lights, beacon, and pitot heat). Check your ammeter or load meter (load meter should show a definite load, and ammeter should show a discharge and your "low voltage" light should be on, if you have one.

Now do a quick walk around, checking all these lights. Yes, even if you are flying during the day. This is part safety and part courtesy. Even during the day, these lights can make you easier to see for traffic avoidance, so you will want to know whether they are working or not. Courtesy-wise, you'll want to "squawk" any light that isn't working so that any pilot who has that plane scheduled to fly at night can be notified or can be switched to a different plane - one that is "legal" for night flight with all the lights working. I know I would be unhappy as a renter if I showed up to fly at night and no one had checked the lights all day. I've been in exactly this situation, and I would have rather stayed home than made the trip to the airport just to not be able to fly that night.

The last check at this point is the pitot heat. CAREFULLY touch the pitot tube after your walk-around... It should be getting warm. You should always be careful here, because the pitot heat gets HOT if it is working, and could be very hot depending on the length of time your walk-around took.

Once pitot heat is confirmed, turn off all the switches in the cockpit except the master battery. Turn ON the avionics master switch, and listen for the heat fan (if equipped). Wait for any GPS or other electronics to go through their full "boot up" before turning the avionics master back off.

Now drop the flaps, check the fuel gauges to make sure they are working, and once the flaps are fully deployed, turn off the master battery switch and take out the control lock.

Make note of anything that isn't working, and talk to your instructor about whether (and how) you can still fly legally and safely with inoperative equipment.

Don't forget to check for AROW (these things are required for the plane to be considered airworthy):

A - Airworthiness Certificate
R - Registration
O - Operating Limitations (Pilot's Operating Handbook [POH] & placards)
W - Weight & Balance (should be in the aircraft-specific POH in the plane)

Stay tuned for step 2 of the preflight - exterior!


What would you add to the interior / cockpit check? Check it off your list by adding a comment below!

Andrew Hartley is a certificated flight instructor in Columbus, Ohio.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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