BUCS

Question 1

BUCS Description

Answer 1

Emergency fly-by-wire backup control system which permits continued controlled flight in the event of a jam or severance in mechanical controls.

Question 2

ARDD

Answer 2

Automatic Roller Detent Device - provides means to physically disconnect crewstation from flight linkage

Question 3

LVDT

Answer 3

Linear Variable Displacement Transducers - Translates control motion into an electrical signal that is utilized by the FMC to provide SAS, CAS, BUCS, and hold mode functions.

Question 4

RVDT

Answer 4

Rotary Variable Displacement Transducers (RVDT) are used to sense a decoupling of the ARDDs

Question 5

What is needed to operate BUCS?

Answer 5

The primary hydraulic system and the FMC must be operational for BUCS to operate.

Question 6

Jammed control linkage

Answer 6

If a jam has occurred, the FMC will engage BUCS when one of the crewmembers disconnects the controls from the mechanical control linkage by decoupling via the ARDD.

Question 7

Failure of the primary hydraulic system results in?

Answer 7

In the loss of all FMC SCAS (SAS, CAS, and BUCS).

Question 8

How is BUCS controlled?

Answer 8

In the BUCS mode the mechanical controls are physically decoupled and control is now maintained through an electronic control loop consisting of the following components:
(a) FMC
(b) LVDT
(c) Electro-Hydraulic Valves
(d) Actuator Solenoids

Question 9

Severance

Answer 9

Upon sensing a control mistrack the LVDT will send a signal to the FMC which will engage BUCS

Question 10

BUCS FAIL (AXIS)

Answer 10

severance between crew stations.
Action: PLT TAKE CONTROL OF AIRCRAFT IMMEDIATELY
BUCS will not automatically engage and it is imperative for the PLT assume control. In order for the CPG to assume aircraft control, the CPG will need to create a mistrack while simultaneously squeezing the BUCS Select Switch.

Question 11

BUCS FAIL

Answer 11

FMC has determined that the BUCS is in a failed state and will not allow the system to activate.

Question 12

BUCS ON PLT (AXIS)

Answer 12

Severance aft of the crew stations
Action: EITHER CREWMEMBER CAN ASSUME AIRCRAFT CONTROL
There is still direct mechanical linkage between crew stations. BUCS is ON only in the affected axis. Once the mistrack is sensed full authority will be phased in over the next 1 second.

Question 13

BUCS ON (STATION)

Answer 13

Jam in one of the flight control axis’s
Action: CREWMEMBER WHO ROLLED THE ARDD HAS CONTROL IN THAT AXIS
One of the crewmembers must roll their ARDD in order for the FMC to activate BUCS. Once ARDD is rolled full authority will be phased in over the next 3 seconds.

Question 14

Answer 14

Bucs Fail (axis)

Question 15

Answer 15

BUCS ON PLT (AXIS)

Question 16

Answer 16

BUCS ON (STATION) (AXIS)