Por que apenas o aileron externo (“baixa velocidade”) cai quando não há pressão hidráulica no 747-8?

O Boeing 747-8 (diferente do 777) não é uma aeronave completa, mas alguns controles foram adicionados ao projeto original do 747. Os ailerons internos são mecanicamente conectados aos controles de vôo, enquanto os ailerons externos não são. Isso permite que eles caiam sem energia hidráulica.

No Boeing 747-8 FCOM (controles de vôo 9.20.6 - Descrição do sistema):

Roll Control

Inboard ailerons are mechanically controlled and hydraulically powered. Outboard ailerons and all spoilers are electronically controlled and hydraulically powered.

Aileron and Spoiler Roll Control

Rotating either control wheel positions ailerons and spoilers. Above approximately 258 knots/.53 Mach, the outboard ailerons are commanded to the neutral position to prevent overcontrolling. The outboard ailerons become operational at lower airspeeds. Inboard aileron deflection is limited when flaps are extended beyond 10.

To improve takeoff performance and reduce noise, the outboard aileron is deflected down for flap detent positions 10 and 20. The downward deflection is removed if the angle of attack is above stick shaker. The inboard aileron is deflected down when the flaps are selected to 10 or greater.

All spoiler panels operate with the ailerons. Spoiler panels are deflected up or down based on Speedbrake lever and control wheel inputs.

A imagem a seguir de modernairliners.com mostra todos os novos recursos da ala 747-8, incluindo o Aileron droop.