What if the checklist doesn’t go to plan

Take off popham

As a pilot and certainly a new pilot, every time we fly we repeat the checklist ritual.

“Fuel tap on, check oil temperature in the green … ” hang one, wait, what if the temperature isn’t in the green? What if the temperature is way over the green? What does it mean that it is in the green?

What if the checklist doesn’t go to plan?

I got together with on of Airbourne’s instructors Ben Hilton to ask him some questions about the checklist and what to do when things didn’t go wrong. Ultimately, if something doesn’t look right, sound right or smell right – stop the engine. Make the aircraft safe and go and tell someone about the problems. Never go flying if you think there’s a problem. That’s not official advice, it’s just common sense!

When the fuel pump goes on, why do we do so for 5 seconds?

What you’re listening out for is that the electric fuel pump is working. The C42 specifically has 2 pumps; an electric fuel pump and a mechanical fuel pump. The reason we put the electric pump on during critical stages of flight is in case the mechanical one fails.

When listening to the fuel pump over those 5 seconds you can also start to hear the sound of dripping. This is the fuel being pumped and returned to the top of the fuel tank. This is a good sign that the pump is working.

When checking temperatures, what if they’re outside limits during pre-flight actions?

temperature and pressure limits to look for? What if they’re outside of that during pre-flight actions?

Oil Pressure and oil temperature are linked to one another. If the oil in the engine is too cool then it will be rather thick or viscous. 50°C is what we are looking for before we increase the RPM above 2500 RPM. If we do, the oil will be too thick to circulate the engine and perform it’s cooling action efficiently. If the oil is too cold you will be forcing a thicker fluid around the engine. This will result in a higher oil pressure. As the temperature of the oil increases, you should see a decrease in the oil pressure.

If the oil temperature is not rising or rising rather quickly you have to take into account the conditions outside. You don’t want cool air over cooling the oil or warmer air heating the oil. This is why in the winter you might see metallic strips put over the oil radiator.

The danger of over cooling an engine especially in a descent is due to the risk of shock cooling. This may result in cracks to the engine.

Always pay attention to the oil temperature on a decent!

What if the mag drops are more than the 200 RPM outlined in the checklist?

If you see the RPM drop more than the recommended 200 RPM there could be an issue that needs looking at. A mag may have failed and is positioned in the ground position, this would require mechanical skills to put right.

What if at idle the engine is rough running during pre-flight?

It’s not unusual for the engine to run rough for the first 5 minutes or so when starting up. Outside air temperature, choke and several other factors all play a part in this. It’s likely that the engine is rough running because it’s cold. Wait a few minutes and watch the temperature increase. As it does, you should notice the engine starting to run more smoothly at 2000 RPM.

What if the engine stops and then starts fine again on restart?

Sometimes, we start the engine and the it stops after what seems like a perfectly good start. When we try again, it starts fine and remains so as if nothing had happened!

The carburettors have two outlets for fuel, idle jets and the main fuel jets.

When the Throttle is all the way back fuel is only passing through the idle jet which is significantly smaller than the main jet. The idle jet might be blocked or dirty which would explain why the engine initially stopped. If the engine continues to stop when in idle during pre-flight checks, taxiing or similar then it is best to get the aeroplane checked before going flying.

What if an instrument isn’t working

ASI (Airspeed Indicator) – This instrument compares static pressure with dynamic pressure (If the static port is blocked, the dynamic port drives the readings. If that’s the case, then the ASI will over read in a climb and under read on a descent). If the dynamic port is blocked, you will not get a reading and your airspeed will read ‘0’ knots. This usually happens if a bug has jammed themselves inside the pitot. Or if the pitot cover has been left on. If your ASI is not functioning as it should be, you are not legally allowed to fly the aircraft.

VSI (Vertical Speed Indicator) – This instrument has a bellow which expands and contracts however there is a calibrated leak which slowly equalises the pressure to the outside pressure through a Static air port. If that static gets blocked then the VSI will return to ‘0’ and stay there. If that happens you can legally continue your flight but we recommend returning the aircraft and reporting the problem.

Altimeter- This instrument has a sealed bellow at a fixed pressure. As you climb and descend this bellow expands and contracts like a tied up balloon. The outside air pressure enters through a static port. If the static port is blocked then the altimeter will freeze at whatever the last reading was. You can usually tell if the altimeter is working or not as you taxi if the airfield is not at the same level. If the altimeter is not working, you are not legally allowed to fly.

RPM and engine gauges – These gauges are driven by electrical sensors and components in the engine. If these are not working it’s likely there is a lose connection or possibly a fuse popped or lose. Check the fuses, if it’s not these then stop the engine and report the problem. Although not a legal requirement, not having that information during flight can be potentially dangerous.

How do you check the fuses?

Depending on the aircraft, the fuses are easier to understand more so than others. In some aircraft, you can see that the fuse has ‘popped’ out of position. Simply push it back in, check the problem is fixed. However, some aircraft it is not as easy to check the fuses. In that case, don’t try checking them yourself, stop the engine and report the problem.

Anything else you’re wondering about with regards to the checklist? Let us know and we can add it here. 

Disclaimer: This article was written for information only and was up to date at the time of writing. Please always ask a qualified instructor for more information and discuss airfield operations and the use of aircraft equipment with a suitably qualified person.