Let’s say you work for Lufthansa and you’re planning a Boeing 747-8 transatlantic flight. Do you try to plan the fastest trip so the plane can arrive early? Or might you conserve as much fuel as possible, thus saving the company money. Perhaps you can do a little bit of both.
I recently visited Lufthansa’s Operations Control Center in Frankurt. To learn how the carrier plans its international flights, I sat with Marcus Pabst, “Senior Flugdienstberater,” as he decided the best route for Lufthansa Flight 456 from Frankfurt to Los Angeles.
How does the process start?
We start with the passenger and cargo figures. Depending on the weight from the aircraft and the weight from the complete payload, we are going to calculate the fuel for the flight.
How can you calculate weight for passengers?
For us, we have roughly 100 kilos per passenger, including the baggage weight. For the passenger, we have 84 kilograms as an average, and 16 for baggage, including hand baggage. (100 kilograms is about 220 pounds)
What happens next?
I put that information in the system. And then the first thing the computer checks for me is weather for our destinations and for alternates. We always have at least one alternate. In case of bad weather at the destination, we have to plan a second alternate.
And where could the flight divert to today?
It’s San Diego. All of the airlines try as much as possible to choose an alternate as close as possible to the destination to save, obviously, fuel. If the distance is so close that weather is going to impact both of the airports, you take into account a more separated alternate. But for today, in LA, we have only one. We have a picture here. (He points to a monitor.) And you can see, no clouds. No rain. No fog. Good weather. The next Lufthansa station would be San Francisco. But as the weather is very good in LA, we don’t need to use San Francisco as an alternate.
What’s the next step in the process?
The departure runway, because of the wind, is going to be Runway 07C, heading 70 degrees to the east. Departure shall be – but not must be – toward the wind to get more lift under the wings. To L.A., it should be faster to take off to the west. But because of the wind and the traffic situation, we are not going to get an exemption just to save two or three minutes on our departure route. After takeoff we make a left turn and may proceed to the west, heading to L.A.
How did we calculate the fuel needed for today’s flight?
Today, we have 39,600 kilograms as payload. Adding t
otal payload plus the weight of the aircraft, we have our total zero fuel weight, or ZFW. For this ZFW, the pilot took 121 metric tons of fuel. He took 2,500 kilograms more than the minimum take off fuel calculated by the flight dispatcher. For that aircraft, the fuel flow per hour is 10 tons.
So the 747-8 always burns 10 tons per hour?
It depends on the route. If you have a longer route, with higher weight, you need more fuel. It can be up to 12 tons per hour. But the average is 10 tons.
What about the earlier model of the same plane, the Boeing 747-400? Does it use more fuel?
It’s almost the same. The big difference is the performance. For the new one, the engines are better with bigger wings – some two meters longer each side – and also the airplane is some seven meters longer, so we can transport more weight. As a consequence, the aircraft is heavier. It means for a very similar amount of fuel, you can transport 40 passengers more. Obviously you gain more money if you can sell more tickets. But from the average fuel, it’s almost the same.
When you plan your flight, what options does the computer system give you?
Usually, we have either a minimum fuel track and a minimum cost track. To save fuel or to save costs. For costs here, we include the fuel price and also overflight costs. Depending on the country and how long you fly through an airspace we have to pay an overflight charge (to the government).
What countries will this flight fly over?
We start over Germany. Then we have to fly until we leave Germany, into the Netherlands into the United Kingdom. The routing is via Glasglow into Scotland. Then Ireland because Irish airspace covers halfway through the North Atlantic. Then we have Iceland, and then we have Canada. (In all, Pabst tells me Lufthansa will pay about $8,500 to governments for the right to fly into airspace. Among major countries, Pabst says, Russia has the highest overflight charges.)
You have to pay the Irish even though the plane does not actually go over the Island?
We are not flying over the country Ireland. It’s interesting. You see here is the island, Ireland. But the airspace controlled by the Irish is that big one here. (He points to a region from Ireland into the North Atlantic.) And we are flying that corner here, until 20 degrees west. That’s why we have to pay something to Ireland.
How do you decide the altitude for the flight?
It increases with the consumption of fuel. Because the aircraft is going to be lighter, it means I can make some step climbs. The goal is to fly as high as possible, saving fuel. At higher altitudes the airplane has a lower fuel flow, or fuel consumption per hour at an aircraft. I started here near Frankfurt at 32,000 feet. Then over the Atlantic at 34,000. Then later over Canada at 36,000. Then two hours before arrival 38,000.
What does it cost Lufthansa to make this flight to Los Angeles?
For L.A. today, we paid almost $140,000 in fuel and overflight charges. (That price does not include a whole bunch of other costs, like landing fees, catering costs and crew costs.)
Is it about the same every day?
It’s similar because the amount of fuel is maybe five tons more or five tons less, and the countries that we fly over are almost the same every day.
Does the computer always pick the fastest route?
It depends on what I have preselected. I have four options. I can tell the computer, give me a minimum cost track, including the overflight charges. Or I can ask for a minimum fuel track only considering the fuel burn. Or I can ask for a minimum time track. I would use that if I duty time problems from the crew (crew are permitted to only work so many hours per day) or most of the passengers are transit passengers and have to pick up their next flight, and we are arriving so late that if I have to send 50 passengers to the hotel or to another airline we are going to have to pay more money. The fourth option is the minimum distance track – the shortest distance between two points.
If a flight is going to be on-time, do you always pick the cheapest option?
Yes, of course. You see I can have a gain of seven minutes if I choose the fastest option. But look at the fuel. It would cost $10,000 more. It doesn’t make sense.
Looking at the map of the flight, it doesn’t necessary look like it’s the fastest route. Is it really quickest to fly over northern Canada and then drop down into the United States around Montana?
For our flight, you look at this graphic and you think, ‘Oh, it’s not the optimal route.’ Because the optimal route should be a straight line. But to LA we are almost flying the minimum fuel track. And this fuel track differs every day depending on the upper air winds enroute.