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What's going on in the flight deck before departure?

Nov. 02, 2019
14 min read
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Sitting in the gate area waiting to board your flight, the big windows of the terminal building often let you peer down through the flight deck windows. Inside, the two figures seem to be calmly going about their work, maybe taking a sip of something hot from a mug, chatting away.

As you make your way onto the aircraft, you may catch a glimpse through the open flight deck door. An array of buttons and lights seem to fill the entire space. The pilots pressing some, ignoring others. Sharing the mystery contents of an iPad screen with each other. However, before you can absorb what’s really going on, you’re bundled down the aisle toward your seat.

So what really is happening in the flight deck before departure? Which buttons are being pressed and what exactly are the pilots saying to each other? This is your behind the scenes tour.

Who's doing what?

On a long-haul aircraft like the 787 Dreamliner, we will usually arrive on the flight deck around 45 minutes before the Scheduled Departure Time (STD). The initial briefing to discuss the weather and fuel requirements will have been carried out in the Crew Briefing Center, or at the gate if away from main base.

Two pilots at work during departure of Dallas Fort Worth Airport in United States of America. The view from the flight deck with high workload the beginning night through the wind shield
The roles of the pilots are divided into Pilot Flying (PF) and Pilot Monitoring (PM).

We will also have decided who is going to be "doing the sector" – the pilot, be it the captain or first officer, who will be responsible for flying the aircraft and managing the flight. This role is known as the "Pilot Flying," or PF. The other pilot, by default, becomes the Pilot Monitoring, or PM. It is their job to talk to ATC, manage checklists and monitor what the PF is doing. The predeparture process is complex, so just like when airborne, there is a set of Standard Operating Procedures (SOPs), which split the tasks between the PF and PM.

Read more: How the 787 uses electricity to maximize efficiency

The Maintenance Log

Once we have stored our jackets and hats, the first job is to review the Aircraft Maintenance Log (AML). Legally, every aircraft must have a logbook that not only details any defects with the aircraft, but more importantly, what work engineers have carried out to rectify them. On most aircraft this is a paper document but on the 787, it’s electronic — known as the eLog.

Very rarely do aircraft depart with a 100% clean bill of health. Aircraft manufacturers know that systems will develop faults, so they have contingency systems and procedures. In order to keep the show on the road when a technical fault occurs, engineers check the Minimum Equipment List (MEL) to see if the aircraft is safe and legal to fly with that fault.

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The whole point of the MEL is to minimize the impact on the punctuality of flights, without degrading flight safety.

The MEL details exactly which systems the aircraft can safely depart without and any permutations of this condition. It also defines the period within which the fault must be properly repaired.

Most commonly, this will be items in the cabin: broken toilet seats, blocked drains, damaged carpets — items that need fixing at some point, but not worth delaying the next flight for. With these low priority items, engineers can defer them to be fixed within the time period specified in the MEL.

From a technical point of view, a common MEL item on the 787 is the wheel brake system. There are eight wheel brake systems installed — one for each main wheel. However, after extensive testing by Boeing during the developmental stage, it was deemed that the aircraft can safely depart with some of these not working.

MEL entry 32-45-01 — Wheel brake systems. Eight installed, six required. (Image courtesy of FAA)

By cross-checking the reference number in the eLog against the entry in the MEL, we can determine exactly how many brake units can be unserviceable (two) and any operational changes that we may have to make to keep the flight safe.

For example, with an inoperative wheel brake system, we have to leave the gear down for two minutes after takeoff. This allows the wheel to spin down naturally before being retracted into the belly of the aircraft. So next time you see a 787 leaving its gear down after take off, this is most probably why.

Read more: How pilots handle an in-flight engine shut down

Flight Management Computer set up

Once both pilots have digested the contents of the eLog and how they will affect the departure, it’s time to set up the flight deck up. This is where the SOPs come into their own.

With a lot of work to be done in a short space of time, the SOPs give the PF and PM different tasks. For the most part, the PF is responsible for loading the flight plan into the Flight Management Computer (FMC) and the PM is responsible for setting up all the other aircraft systems. With both of these procedures carried out correctly, the aircraft will almost be ready for flight.

As the PF will be doing the flying, it's their responsibility to ensure that the route and numbers in the FMC reflect exactly what they expect the aircraft to do in flight. Incorrect information in results in incorrect actions out.

The flight plan is requested from the airline's servers by entering the flight number. Once this has downloaded, the PF then enters the departure runway and initial routing. They then go through all the waypoints along the route to ensure that they match the route on the paperwork from the briefing.

Downloading the flight plan on a 787 Dreamliner.

On longer routes, there can easily be 30 pages to work through. However, it's imperative that each point is checked as this is the route that the Autopilot will follow.

Whilst the PF is setting up the FMC, the PM is tasked with ensuring all the aircraft systems are ready for push back and engine start. With so many systems to configure, there is a set flow to ensure that nothing is missed.

The overhead panel may look like a mess of buttons and switches, but it's actually organized into several columns. Starting at the top left and working top to bottom, left to right, the game is to extinguish as many lights as possible.

The overhead panel may look complicated but it's surprisingly well structured.

Like most modern airliners, the 787 operates a 'dark cockpit' philosophy. If there are no lights or switches illuminated, then things are as they should be. The illumination of a switch draws your attention to it, asking the pilot if they really mean for it to be in that position. The navigation system, electrics, hydraulics, external lights, fuel, air conditioning and pressurization all get configured at this stage.

The PM will then reset the Electronic Checklist (ECL) system and obtain the latest weather for the airfield. Once the PF has entered the route into the FMC, the PM will also check this. With such important data as the route, two checks are always better than one.

Read more: How pilots stay alert on ultra-long-range flights

External Safety Check

Before each flight, in addition to the checks performed by the engineers, one pilot must also check the outside of the aircraft. This is normally done by the PF, but if an extra pilot is carried as part of an augmented crew, then they will carry out the external check.

This walk-round is mainly to check items visible to the naked eye. The condition of the tires and engines are inspected and the leading edges of the wings are checked for any damage, normally from bird strikes. The condition of external probes is also checked.

If any anomalies are spotted, engineering will be called and the issue investigated further.

The inspection route of an external safety check on a 787 Dreamliner. (Image courtesy of Boeing)

Critical Data Procedure

Once the PF and PM have completed their individual jobs, it's time to come together and focus on the most safety critical part of the predeparture process.

For each and every flight, the pilots are given a loadsheet by the ground staff. This details the weight of the passengers, bags, cargo and fuel and shows where on the aircraft they have all been loaded. By entering the weights into the FMC, we are telling the systems how heavy the aircraft is. This is then used to calculate a whole range of data such as expected climb rates, estimated times of arrival and, as you'll see below, the takeoff performance. Transferring the data accurately from the loadsheet to the FMC is critical to ensure a safe takeoff, hence the name of the procedure. Aviation is littered with incidents where the crew have entered the weights incorrectly and then failed to get airborne at the end of the runway. This is why a good crew will not allow themselves to be distracted by other tasks or people whilst they are carrying out the critical data procedure.

The first officer will check these details on the loadsheet and then the captain will do the same, finally signing one of the copies to certify that they are happy with its contents. The signed copy must leave the aircraft with the ground staff and the other copy stays with the pilots.

Perf Init page being prepared for the Critical Data entry.

Takeoff performance

The next step is to calculate the performance required for takeoff. Aircraft don’t just get airborne by luck. We know exactly how much runway is needed, how much engine power to use and what speed to lift off at. To calculate this, we use the Onboard Performance Tool (OPT).

The OPT enables us to enter the airfield weather information and, using the TOW entered earlier, calculate our takeoff performance. This is one of the most critical stages of the flight. An error here could have serious consequences on the takeoff run.

Once the performance figures have been checked by both pilots and transferred to the FMC, the preflight procedure is complete.

Read more: The science behind a beautiful aircraft takeoff

Departure brief

Whilst the aircraft is now ready to depart, flying is a team effort, so each member of the crew needs to be aware of how exactly they expect the departure to proceed. To do this, before every flight we will conduct a departure briefing.

A good brief is exactly that — brief. It should be to the point and draw attention to the major factors of the day, commonly referred to as the 'threats'. What's going to cause us issues on this particular departure? Is there bad weather? Are the taxiways particularly confusing? Is there snow or ice on the wings?

Once the threats have been discussed and how we plan to deal with them, we will then run through the departure in chronological order. We will check items such as the fuel on board and clearance from ATC and discuss how they will affect the flight. At the end of a good brief, all the pilots in the flight deck should have a clear picture in their mind how each of them expects the departure to evolve.

Emergency brief

Not only will the departure brief cover items that we expect to happen, it should also cover events that could happen — also known as an emergency brief.

Non-normal situations like engine failures rarely happen. Most pilots will go an entire career and never experience one. However, the possibility is always there so we will always plan for that possibility.

By talking through what exactly we will do should a certain emergency occur, if it does happen for real, the drills will be fresh in our minds. This often includes carrying out touch drills whereas we discuss which buttons and switches we will move, the pilot actually puts their fingers on that switch. This reinforces the muscle memory to connect the movement of that hand to the selection of that particular switch.

Preflight checklist

Once the departure and emergency brief is complete, it's time to wrap everything up and carry out the preflight checklist. This is conducted in a "challenge and respond" fashion. The PM reads the checklist item as a challenge and the PF checks the status of that item and responds accordingly. Each time the item is answered correctly, the PM ticks off the line using the cursor. With the checklist complete, the aircraft is ready for departure.

Bottom line

Setting up an airliner is a complex task. Multiple systems have to be checked and configured in the correct way. With so many tasks to completed in a short space of time, the tasks are divided between the two pilots.

When entering the critical data, total concentration and attention to detail is essential. Sometimes, with lots of distractions about, a good crew may even shut the flight deck door to increase the focus.

However, setting up the aircraft is only half the job. The entire crew needs to be on the same page as each other. They need to know how they expect the departure to proceed and who will be doing what. An effective brief keeps things to the point, drawing particular attention to the relevant threats.

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Featured image by In Pictures via Getty Images

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