Flight planning moment by moment, part 1/2

In the first part of my blog, I’ll focus on what happens before the captain steps onto the aircraft. In a later, continuation part I’ll move on to flight preparations that take place on the aircraft.

My clock rings before the cock crows. On my rostering list today is a morning flight to London departing at 8 a.m. I arrive in good time at our operating centre, located in the southwest end of the terminal building, and I report for the flight as the third member of the crew. The others will arrive no later than an hour before departure. I head for the clothing lockers to put on my “working gear”.

On my arrival at Flight Dispatch, the co-pilot has already printed out the flight papers. We both receive the log, namely a (today) seven-page operational flight plan, which has all the essential information about a preliminary flight plan prepared by the flight preparations office, better known as dispatch. The planned route runs south of the Åland Islands, across southern Sweden towards Aalborg in Denmark, then over the North Sea to the River Thames delta and London airspace.

Together we go through a 40-page stack of paper containing all the essential information about the flight. The CIS (Cockpit Information System) tells us that the aircraft is OH-LXK, i.e. an Airbus A320. It appears to have spent the night in Helsinki and is parked on stand 34. A total of 141 passengers have booked – so it’s almost a full flight. The aircraft’s zero fuel weight (ZFW) is 58,205 kilos, and the shortest onward connection from London is to Orlando, Florida, only an hour and 20 minutes after the scheduled arrival time.

The CIS also has contact information for the preparers of our load sheet in the centralised load control centre in Prague as well as for support functions, such as ground handling and passenger service, at our destination, London. We check the CIS for the latest flight deck computer updates, which should be in the aircraft computer. From the safety section, we receive a warning about a radio shadow in the northwest corner of Danish upper airspace, but our route today does not run so far north that it would bother our progress. From the navigation section, we see that our company is not restricted in terms of automatic landings at Heathrow. In the miscellaneous section, there is a note about swine flue. Finally, there’s the crew list. Today our flight has a normal size of cabin crew – four people, three female flight attendants and one male flight attendant.

A smooth flight in prospect

Then to weather information: the SWC (Significant Weather Chart) indicates fairly clear flying weather all the way to the British Isles. The headwind component is only four knots and dispatch has calculated our flight time to be 2 hours 35 minutes with the forecast wind. A jet stream from the north may possibly cause weak turbulence towards the end of the flight between flight level FL 370 (37,000 feet = 11,100 metres) and FL 240 (7,200 metres). This will not, however, interfere with the cabin crew’s serving of food and drinks.

On the return flight the jet stream will already be weaker and will probably not affect the flight. The tropopause (= the upper limit of the lower atmosphere, i.e. the troposphere) is smooth at an altitude of 10,500 metres on the route, slightly below our cruising level of FL 360 (10,800 metres) . A smooth tropopause also suggests a smooth flight.

London Heathrow’s corrected weather forecast predicts for our arrival time a weak northerly wind, visibility 8 kilometres and a few individual clouds at an altitude of 90 metres. With a 30 per cent probability, the visibility at arrival time will only be 400 metres: fog and a cloud base at 30 metres. What do those Brits care? Doesn’t it always rain there? The weather forecast is not below the operating minimum, so we need only one alternate airport. We choose London Gatwick. Its weather should have improved before our arrival time. The weather en route at Stockholm, Copenhagen and Amsterdam seems to be fine for flying.

A NOTAM (Notice To AirMen) states that there is a slight frost on Helsinki’s runways, but the braking coefficients are good. A few cranes are said to be located close to the airport. In London there is a warning about interference on the runway 27L instrument landing system, noise restrictions and a number of closed taxiways as well as an inoperative taxiway centre line light. The Gatwick list is a little shorter. With this flight time we would land 20 minutes before schedule. We have not yet been given any air-traffic control restriction, i.e. slot, but if visibility deteriorates, we may receive one. We therefore have no justifiable reason to change the cost index proposed by dispatch, which determines the least expensive possible flight speed taking into account variable costs according to flight time and the price of fuel – or not yet, at least.

Fuel in the tank

We decide not to fuel up for the return journey, because the price of fuel at Heathrow is not so expensive that it would be worth carrying it there from Finland. Every extra 1,000 kilos of fuel (or other extra weight) would increase, on this route and in these conditions, our fuel consumption by 111 kilos per hour. We check again with the dispatch service desk that no air-traffic control restrictions (slots) have been assigned to our flight. We decide, taking into account the above factors, to take 11,000 kilos of fuel onto our aircraft. On an aircraft, fuel consumption is determined in kilos, because the energy content of the fuel depends in fact on weight, not volume.

We plan that we will consume 200 kilos in taxiing and 7,300 kilos in flying. On top of consumption, 800 kilos is reserved for the alternate airport Gatwick and also, to fulfil official regulations, our flight plan requires a 300 kilo contingency reserve and a 1,200 kilo final reserve, which enables a 30 minute flight at the initial approach altitude. We also decide to take along another 1,200 kilos recommended by the fleet chief, because it is possible that the weather will deteriorate – in which case traffic can become congested very quickly. The cockpit information system tells us that the average holding time above London during the last month is 11 minutes.

With this amount of fuel, our departure weight is 69 tonnes and our operating time 4 hours and 17 minutes. If there is no delay, we would land in London with 61.5 tonnes – around four tonnes under the permitted landing weight. The co-pilot checks that the amount of fuel taken on board is logical – by entering the fuel figures into the flight dispatch computer, from where the data is transmitted to the refuelling company and the preparers of the load sheet in Prague. From the Capco system, I see that the frost that accumulated during the night has been removed from the aircraft’s wings.

We have spent 27 minutes on flight planning, leaving 33 minutes to departure. The co-pilot gathers the papers into a folder and we immediately walk towards the security check, from where a crew transfer will take us to the aircraft.

Jussi Ekman