Why do airline pilots walk around the aircraft before takeoff?
You probably noticed sometimes, when boarding an aeroplane as a passenger, the pilot is outside walking around the aircraft. The pilot is more apparent at night as they would carry a torch and aim it towards various aircraft parts.
The Walk-Around:
The procedure is called: “Walk-around” (Definitely an unexpected name!).
Why do Pilots Walk-Around?
Pilots walk around the aircraft to ensure that the aircraft’s exterior is safe and secure. Pilots are looking for various problems such as:
- Loose parts.
- Fluid Leaks, such as hydraulic or fuel.
- Worn Tires.
- Debris.
- Dents on the airframe.
- Check if the probes, sensors and valves are blocked.
Engineers also do the Walk-Around:
You probably spotted pilots doing walk-around in your flights, but an engineer would’ve already checked the aircraft upon landing before the pilots do.
As engineers do the walk-around first, they are more likely to spot a defect, if any, well before; this way, they can ensure the aircraft is fixed before starting the next operation to minimise delays.
Also, when the aircraft lands, if it has any problems already, pilots would’ve informed engineers by radio so they know exactly what they are looking for when doing the Walk-Around.
If the Engineers do it, then why do airline pilots walk around the aircraft before takeoff then?
Good question! Let’s talk about the swiss cheese model.
Swiss Cheese Model:
The model represents accidents causation. Each “cheese” is a barrier against failure or an accident. The more unaligned barriers you have, the less chance of failure.
For our context, we have two barriers (Engineers & Pilots); both do the walk around, and if the first one misses, then the second one would probably not.
You have to remember that pilots are the last barrier to a swiss cheese model. No one checks after them. If they miss, they will need to deal with a failure caused by a series of preceding misses. That’s why the walk-around procedure is vital.
What do pilots check for during the walk-around? Boeing 737NG example:
Every aircraft has a specific procedure as the systems are different. As I fly the Boeing 737NG, I will very briefly describe how the walk-around is done.
We start by the left forward fuselage checking the probes & sensors, then move to the nose where we check the radome, then the nose wheel well to check the tires, gear strut and the nosewheel steering assembly.
After that, we move to the aircraft’s right side, where we check the other set of probes, sensors and ports; Ram air door, lights and flaps. Check the engine for any visible damages, and check the fan blades and panels.
Verify the fuel tank vent, static discharge wicks, the main gear hydraulic lines and gear strut and actuators. Move to the tail and check the tail skid, APU cooling air inlet and exhaust inlet.
You do the same thing on the left side of the aircraft.
As I mentioned, the check is quite long, and I only gave a concise overview as a taste test. If you are interested in what we check exactly on the Boeing 737NG during the walkaround, send me a msg on Instagram, and I will make sure to write an article about it.
I hope this short post has given you an insight into why airline pilots walk around the aircraft before take-off.
References:
James Reason HF model. SKYbrary Aviation Safety. (2021, October 26). Retrieved May 2022, from https://skybrary.aero/articles/james-reason-hf-model
The Boeing Company. (2005). Flight Crew Operations Manual. Retrieved March 2022, from http://www.737ng.co.uk/737NG%20POH.pdf
Davidmack. (n.d.). Swiss cheese model of accident causation. Wikimedia Commons. Retrieved from https://upload.wikimedia.org/wikipedia/commons/e/e8/Swiss_cheese_model_of_accident_causation.png
