Up and away: how load cells help airlines save fuel

At Alderney airport in the Channel Islands, travellers are often surprised as both they and their luggage are weighed ay check-in. What’s more, they will be seated in a specific place in the plane to even out the weight between the front and the back of the plane, especially if there is a heavy load of tomatoes or other fresh produce in the back!

The reason is simple; too much weight at the back, and the aircraft will fly nose up, which increases the amount of fuel it uses. The same principle applies to passenger and cargo planes; the weight of passengers or freight determines how much fuel is required.

How to weigh a plane

Needless to say, weighing a plane even as large as the new Dreamliners or A380s is a simple task when you have the right load cells! All planes are weighed at the point of delivery, and periodically during their lifespan. In the case of a European commercial airliner, for example, this is every four years, to comply with international law.

 

Roll onto these scales, please…

Empty aircraft can be weighed using platform scales equipped with load cells. The aircraft is simply pulled forward onto platforms that sit under each wheel, and the net weights from each scale are added together to give the total ‘basic empty weight’. The differences between the readings are used to calculate optimum weight distribution and to provide centre of gravity information.

Each plane will be weighed three times each session to ensure an accurate reading. There are more scales required than you might imagine: the A380 commercial airliner has no less than 22 wheels.

 

Aircraft can also be jacked off the ground and weighed by placing a load cells between the top of the jack and a fixed pint on the aircraft. These load cells are about the size of a tennis ball, and sit in a load-bearing cup with the sensor at the bottom. This method has been popular in the past as every airline has jacks for their aircraft, but has its own safety and logistical issues, and takes longer than using scales.

 

How much does a safety card weigh?

Once the empty weight is know, the weight of each and every item of content is added, from seats to carpets and even safety cards, as Michel Heese, Weight & Balance Engineer for Dutch airline KLM, explained in the KLM “Jessey Knows” blog.

“The weight of every item on the contents list is in our database. A safety card, for example, weighs 0.018 kilos and a Holland Herald (in-flight magazine) 0.306 kilos. Every month our colleagues at Inflight let us know the weight of the new issue.”

 

How much does a passenger weigh?

We may grumble about the weight restrictions for hold baggage, usually less than 25kgs for economy class but at least this is weighed at departure so the loadmasters responsible for the freight on board know how much to account for. The unknown quantity is the weight of the passengers, so airlines use an average weight for every population group, using figures from the European Aviation Safety Agency (EASA).

However, these figures were compiled eight years ago, and may not longer be accurate. The EASA figures on the standard weights of passengers give the average male weight at 84.6kg, a female at 66.5kg and an under-12 at, 30.7kg. However, populations vary in average size and weight. As of the start of November 2017, national carrier Finnair have started weighing passengers before they board flights in order to boost the limited data available on the Finnish population (and save fuel, of course).

 

Does what I wear really affect the weight of an airliner?

In short, yes, along with what time of year it is. EASA research shows there is a marked between winter and summer passenger weights, usually given as + 5kg to account for heavier winter coats and boots. Equally, there is a different average weight of checked baggage, but this time, the winter weight is lighter (an average of 16.9kg for summer as opposed to 16.6 for winter).

 

OK, how much does an airliner weigh?

If you’re wondering how much an empty airliner weighs:

• Airbus A330 = 120,000kg
• Boeing 747 =180,000kg
• Boeing 787-8 = 110,000kg

Once loaded, the Boeing 787-8 Dreamliner has a maximum takeoff weight of 219,540g. The larger Airbus A380 has a maximum takeoff weight of 560,000kg. Takeoff weighs can be affected by a number of factors, including the weather. Planes need to be de-iced in winter, and if temperatures soar, some planes can’t take off, as hot air is thinner than cold and affects the calculations relating weight to climb gradients.

 

Load cells for every task

Whether you’re weighing an airliner or the lightest of materials, we can help. We manufacture our own range of load cells and