onsdag 20 mars 2019

Design Flaw of 737 Max vs Computational Simulation

Is the reason for the two fatal 737 Max accidents a flaw in the design of the airplane, making it prone to stall (see PS2 below), which was compensated by a possibly over-reacting control system, which the pilots could not turn off? Did FAA authorise the plane without proper safety evaluation?   Questions are piling upFBI is joining criminal investigationWikipedia,  Boeing,  New York TimesPilot training, Stability, Aviation expert, Kludge, Aviationcv, Pilots view.

Computational software used by developers of airplanes do not seem to allow simulation of the dynamics of stall and so the impact of stall on aircraft design and safety assessment must be done solely by expensive and time-consuming experiments in flight, and then also the design of the apparently needed control system. This may show to have been insufficient to make the plane safe, something which FAA did not have the capacity to check.

With our new technology of Automated Computational Mathematical Modeling with references here, the full flight of an airplane, like the 737 Max, including the full dynamics of stall, can accurately be computationally simulated as a unique capability shown in the HighLiftPW-3 Workshop, see also front page of Icarus Simulation. Such advanced technology could allow airplane makers better and faster simulations to design aircraft and assess their safety.

PS1 The Jas 39 Gripen is a fighter airplane designed and manufactured by the Swedish aerospace company Sabb, which is inherently unstable (relaxed stability) to allow quick turns and thus needs to be stabilized by automatic active control of small canards (wings) ahead of the main wings. The plane crashed twice from pilot-induced oscillations with a the pilot seeking to compensate an over-reacting control system, in 1989 during landing and in 1993 over central Stockholm.  A commercial aircraft is not designed to be unstable, but to be positively stable.

PS2 Stall means that when the inclination of a wing vs forward motion (angle of attack) is too large (around 20 degrees for a common wing), then the lift to drag ratio suddenly drops from 15 before stall to 2 after stall and the wing drastically loses functionality. The Maneuvering Characteristics Augmentation System (MCAS) was developed for the 737 MAX to prevent stalls in flaps-retracted, low-speed, nose-up flight.

PS3 Boeing is working on an update of MCAS to get 737 Max approved by FAA to fly again, but the problem may be bigger than just a software update asking for a redesign of the airplane, see here.

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