Boeing 787-787 is Boeing's latest wide body mid size aircraft, and the Boeing 787 series includes the 787-3 (cancelled due to lack of orders), 787-8, 787-9, and 787-10.

Taking the Boeing 787-8 as an example, the aircraft has a total length of 56.69 meters, a height of 17 meters, a wingspan of 60.17 meters, and a two-level cabin layout that can accommodate 242 people.

The size of 787 is slightly larger than 767 and smaller than 777, and its main competitors are Airbus A350 and A330NEO.

The Boeing 787 flight control system, based on the 777, fully adopts fly by wire control technology, integrating automatic flight, main flight control, and high lift.

The 787 introduced the concept of Remote Electronic Unit (REU) to position the REU as close as possible to the actuator PCU, reducing the amount of wires used and achieving the goal of aircraft weight reduction.

The ultimate backup form of 787 is similar to 777, but adopts the form of electric backup. In addition, the Boeing 787 can also achieve vertical gust reduction function through flaps and elevators, improving ride quality.

B787 flight control surface layout

The Boeing 787 Flight Control SystemRudder layoutAs shown in the following figure.

The rudder configuration of 787 and 777 is generally the same. 787 has adoptedTraditional exterior layout，Two wing cranesengine.

There are two wings arranged on both sidesA pair of outer aileronsTheA pair of flap flapsTheSeven pairs of spoilers, as well as high lift devices such as leading edge slats and trailing edge flaps.

The tail wing is arranged withA horizontal stabilizerTheA pair of elevatorsandA rudder.

Composition of B787 Flight Control System

Due to 787Fully adoptedThe fly by wire flight control technology, and even the ultimate backup, adopts the form of "electricity", so the power supply requirements for the flight control system are very strict.

787 is equipped with 4 power regulation modulesPCMThe Power Conditioning Module (PCM) is equipped with three AC/DC power supply margins (PMG, DC bus, and battery) to provide uninterrupted power supply for the flight control system.

Boeing 787 Flight Control SystemPhysical ArchitectureAs shown in the following figure.

The flight control system architecture scheme of 787 is similar to that of 777 (such as working mode, redundancy management, etc.). The relevant articles about 777 have already been introduced before, so we will not repeat them here.

Click to read: Introduction to the architecture of Boeing 777 fly by wire flight control system

In Boeing's system,ACEThe actuator control electronics is the core component of the entire flight control system.

After the flight control computer malfunctions, ACE can provide basic control capabilities. At the same time, ACE realizes data transmission between the cockpit control mechanism and the flight control computer.

B787 Final Backup

The backup form of the Boeing 787 flight control system inherits the characteristics of the 777 and choosesTwo pairs of spoilers(4 #, 5 #, 10 #, and 11 #) andHorizontal stabilizerHowever, it was adoptedElectric backupThe form

For the roll axis, the pilot controls the roll control dial on the joystick, and the backup system sends the corresponding RVDT signal directly to the electronic motor control unit (EMCU) of the four spoilers without going through ACE and FCM, thereby driving the movement of the spoilers.

For the pitch axis, the pilot operates the backup pitch balance switch on the central console, and the backup system sends the switch signal directly to the water safety surface without going through ACE and FCMElectronic motor control unit（EMCU）Thus driving the flat tail motion.

Taking into account the mechanical backup of the 777, it can be concluded that Boeing's ultimate backup system generally uses one or two pairs of spoilers to control roll and a horizontal stabilizer to control pitch.

Unlike Airbus A380, Boeing's backup system is difficult to achieve flight control systemMinimum acceptable control（MAC, Minimum Acceptable Control）The requirement cannot achieve sustained safe flight and landing.

But such a backup system can provide certain control capabilities in the event of a failure of the fly by wire flight control system, maintaining the aircraft's attitude for a short period of time and waiting for the system to restart.