The design phase for a new aircraft is a long process that can span several years. Materials and technologies evolve during the lifespan of the design, so Airbus needs to monitor the aircraft weight (status mass) at each milestone review and to estimate what the aircraft will weigh (weight outlook) throughout the process. The introduction of new materials and new technologies, and changes in standards and regulations, are all factors that may affect the aircraft weight; each needs to be carefully considered and modelled in estimating the weight outlook.
Airbus wished to review the weight estimation methods for an aircraft during the design phase and to ensure that the derivation of weight estimates and their associated uncertainties are underpinned by sound mathematical and statistical methods.
The Smith Institute organised and ran an initial one-day workshop at Airbus premises in Filton with members of the Airbus Mass Estimation and Control Team, to explore their use of statistics and mathematics in modelling mass properties. Through the use of examples, Airbus staff described their objectives and their application of statistical methods to weight estimation, so enabling the Smith Institute to review them and to explore component weight trades and sensitivities.
The Smith Institute proposed new methods and established the feasibility of their application by direct discussion with Airbus staff. In the course of the workshop, we considered the following:
- the interaction between components;
- sensitivity analysis – prioritisation;
- uncertainty estimation methods;
- aggregation – Monte Carlo simulations, and
- Bayesian methods for obtaining weight and parameter estimates and their uncertainties.
After the workshop, we articulated enhancements, and proposed new methods for weight estimation and its communication to the design team. These findings were discussed with Airbus in a second one-day workshop and were presented in a report of our review and recommendations for enhancing Airbus weight estimation methods.
The Smith Institute provided an independent analysis of the weight estimation methods and helped Airbus enhance the rationale behind the methods currently used.
We provided different ways of looking at the weight estimation process, introducing the Airbus team to alternative methods of data fitting, of goodness of fit evaluation, and of ways of presenting uncertainties in data.
By working on practical examples based on Airbus models, the Airbus team and the Smith Institute were able to discuss the methods in great detail, highlighting opportunities to refine and improve the Airbus weight estimation process.
The Smith Institute took the time to understand the processes used and issues faced by us today. After several exchanges, both remotely and face to face, they came back to us with some interesting proposals which previously we had not considered as well as some confidence boosting remarks on an approach we had recently developed encouraging us that we had a sound mathematical base for a newly formed process we had developed.
I very much appreciated the time taken, the patience shown and the ability of the team to explain things in simple enough terms using examples so we were not bamboozled by the maths.Judi CheesemanAirbus Operations Ltd