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All you need to know about the pre-flight 'walk-around'

Dec. 05, 2020
12 min read
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As pilots, your safety is our first, second and third priority. Come to think of it, it's probably our fourth priority, too. With that in mind, we take the physical condition of the aircraft extremely seriously.

Before each flight, in addition to the checks the engineers complete, one of the pilots will always conduct an exterior "walk-around" of the aircraft to ensure that they are happy with its condition.

If you're a private pilot, you may be surprised to see just how similar the preflight exterior inspection on the 787 Dreamliner is to your light aircraft.

Tires, engines, hatches and lights all come under close scrutiny before we will accept the aircraft for the flight. After all, when your own life depends on it, you have a vested interest in ensuring that it is safe.

Probes, sensors, ports and vents

Pitot tubes and static ports

The exterior inspection on the 787 Dreamliner begins at the front left of the aircraft, just underneath the L1 door and works around in a methodical, clockwise route. Some of the most important probes and sensors on the aircraft are located in this area so it is important that we pay close attention to these.

The pitot tube faces into the oncoming air and is used to determine the speed of the aircraft. As a result, it's a fairly important piece of kit. Also in this area are the static ports, used to sense the outside air pressure and from this deduce the aircraft's altitude.

As part of the check, we make sure that they have not been damaged and are free from any obstructions or blockages. If they were to be blocked, it would result in erroneous airspeed or altitude indications in the flight deck.

Read more: Singapore to New York: How pilots fly this epic 18-hour journey

Overnight ice on a pitot tube. (Photo by Charlie Page/TPG)

On most days, the chances of finding a pitot blockage are quite low. However, during the winter, if the aircraft has been shut down overnight, there's a chance that the tubes will become iced up -- like in the photo above. Fortunately, they are heated to stop this from happening in flight so once the aircraft is powered up, this should melt off. However, this is why we perform a visual inspection to ensure that this has indeed happened.

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However, with the number of aircraft currently being wrapped up for long term storage, these checks are particularly important at the moment. When an aircraft comes back from storage, there's always a chance that dirt or insects have found their way into the tubes. Engineers will conduct thorough checks before the aircraft returns to service but it always pays to make extra sure yourself.

Outflow valves

The 787 has two outflow vents as part of the pressurization system, one at the front and one at the rear. In-flight, these open and close to regulate the amount of air leaving the aircraft. They are also used strategically in the case of smoke in the cabin.

Depending on the location of the smoke in the cabin, we can close one of these outflow valves to expedite the removal of the smoke. For example, if the majority of the smoke is at the rear of the aircraft, we close the forward outflow valve. This stops the smoke from moving forwards in the aircraft and forces it out of the rear outflow valve.

As part of the preflight check, we ensure that the door is not damaged and that nothing is blocking the vent.


I love the shape of the nose on the 787, but the drooping design and radome serve more of a purpose than pure aesthetics. Hidden behind that nose cone is the weather radar system which we use to detect thunderstorms and large build-ups of cloud and rain.

As part of the check, we make sure that there is no damage to the radome and that all the latches are secured. The video below shows how the latches look when they are not secure and also gives you a sneak peek at what the weather radar system looks like.

Read more: Why pilots don’t have to wear masks when flying

Nose wheel

The nose wheel assembly of the 787 is what allows us to steer on the ground and also provides some illumination for the taxiway ahead. When approaching the nose gear, we take a look at the tires to make sure that there is no damage and that the tread has not been worn away. We also inspect the taxi lights, making sure that they are clean and that the glass is not cracked.

When we retract the gear after takeoff, the gear bay doors open to allow the gear to move up inside the aircraft (on the 787-9 and -10, the nose gear doors automatically open up just after liftoff, even before we have selected the gear lever up in the flight deck. This allows for a quicker gear retraction). We take a look at the doors to ensure that they are not damaged.

We also take a look up inside the gear bay itself.

The nose wheel bay is a prime location for stowaways. (Photo by Simon Dawson/Bloomberg via Getty Images)

Sadly, in parts of the world where opportunities are hard to come by, some people see stowing away on an aircraft as a good way to make their way to a new country to start a new life. However, this almost always ends in tragedy.

The gear bays are plenty big enough for a person to climb up into and hide. As a result, we always check this space for anyone who shouldn't be there.

Lights and pack inlets

The right-hand side of the nose is very similar to the left-hand side. Like almost all aircraft systems, each probe has a backup. In the case of the pitot and static systems, the aircraft looks at data from multiple inputs to confirm that the information is indeed correct. As a result, the right-hand side of the aircraft has many of the same probes and ports as the left-hand side.

Wing root

The wing root contains some important equipment that needs careful examination.

Whilst the outflow valve mentioned above forms the end of the pressurization system, the start of it begins in the wing root with the pack and CAC (cabin air compressor) inlets.

The landing light can be seen where the wing meets the fuselage with the pack and CAC inlets below it. (Photo by NOAH SEELAM / AFP) (Photo by NOAH SEELAM/AFP via Getty Images)

Here, two aerodynamically designed inlets allow fresh air to flow from the outside environment, into the air-conditioning system and then into the cabin. It's this unique system that makes the air on the 787 fresher than any other aircraft.

To protect these inlets when on the ground, there are deflector doors which we must make sure are free from damage and obstruction.

Where the wing meets the fuselage is the site of the brightest lights on the aircraft, the landing lights. Used at night to illuminate the runway on takeoff and landing, they also serve as a "see-and-be-seen" system.

Some airports require aircraft to "backtrack" (taxi) along a runway before either turning around to take off or vacating at a taxiway further down. As part of good airmanship, anytime we are on an active runway, we will turn on the landing lights, even during the day.

This makes us more visible to any other aircraft which may be trying to land or take-off.

Due to the location of the landing lights on the front edge of the wing, they are too high up for a close inspection. As a result, we visually inspect them to make sure that they are clean and not cracked or damaged.

Right engine

One of the most obvious items to check, there's very little more than superficial details that we can actually examine. Most of the workings of the engine are hidden away in the core, accessible only to engineers. As a result, they complete regular checks of the inner workings of the engine with a boroscope, allowing them to examine important fittings without having to take the whole engine apart.

The preflight inspection of the engine which the pilots conduct focuses on the hatches, probes, sensors, fan blades and the spinner.

Pressure sensors, one at the front of the engine and one at the rear, are used to determine the turbine power setting known as TPR -- turbine pressure ratio. Like with the pitot tubes, these could get iced up in cold weather so we must make sure that they are clear from ice and other obstructions.

Read more: Smashed windshield — how pilots deal with cracked glass

Ensuring all hatches on the engine are closed is part of the pre-flight check. (Photo by Patrick T. Fallon/The Points Guy). The front fan blades are what starts the process of air being sucked into the engine and are finely balanced pieces of art. Any damage to one of these, from a bird or large stone, could result in significant engine vibration which could lead to further engine problems. The spinner, in the center of the front fan, needs checking for ice build-ups, too. Some engines on certain aircraft types have a rubber spinner which is easily bendable by hand. Whilst this seems flimsy for such an important structure, the flimsiness is what makes it so efficient. If ice builds up on the spinner when the engine is running, there is likely to be more ice in one area than another. As it is spinning at such high speeds, this extra weight will cause the spinner to bend, breaking off the ice in the process. A simple solution to a potentially massive problem.

Right wing

With the engine inspected, we continue walking out along the 60-meter wingspan, checking the front and underside for any damage and ensuring that all the inspection panels are closed. Around the wingtip, we make sure that the navigation lights are working (green on the right-wing, red on the left).

Along the trailing edge of the wing, we make sure that all the static discharge wicks are in place. Any missing wicks could indicate that the aircraft has been struck by lightning and would then require further checks by an engineer.

Right Main Gear

The part of the aircraft which takes the most punishment on a daily basis, the main landing gear is built strong enough to take the impact of heavy landings, but lightweight enough to help keep fuel burn to a minimum.

Each main landing gear assembly has four wheels, each with its own braking unit. Like the nose wheel, the tires are checked for damage and the tread is inspected to ensure that it is deep enough to deal with rain, slush and snow. If the tread is too low, the tire must be changed before the flight.

The condition of the brakes must also be checked, the brake wear indicator providing an easy way to check this. Once again, if they are too worn down, they must either be changed before the flight or declared inactive.

Tail and the rest of the aircraft

Being so high up, there's little on the tail which we can really inspect so closely. Once again it comes down to checking for any obvious damage to the leading edge of the horizontal stabilizer and the tailfin itself. The APU exhaust is also checked for any fuel leaks and the rear-facing navigation lights are checked in the same manner as other lights.

From here on, the left-hand side of the aircraft is exactly the same as the right-hand side. The left main gear, engine and wing must all be checked with the same scrutiny as the right-hand side. In total, a thorough walk- around will take around 10 minutes before it's time to head back up the flight deck and finalize the aircraft for departure.

Bottom line

The pre-flight walk-around is a key part of ensuring that the aircraft is safe for flight. Whilst engineers perform a certain number of checks before each flight, there are certain elements that the pilots must also check. Not only is double-checking something always a good idea but when it's your own life at stake, it also gives you added peace of mind seeing things with your own eyes.