Fly-By-Wire System(FBWS) Flashcards
Primary flight controls are:
- Two ailerons
- Two elevators
- A rudder
Secondary flight controls are:
- A horizontal stabilizer(HSTAB)
- Eight Multifunction spoilers(MFSs)
- Two ground spoilers
- Four flaps
- Eight slats
FBWS controls all surfaces except:
Flaps and slats
*controlled from lever in cockpit.
All surfaces are hydraulically actuated except:
HSTAB, which is electromagnetically actuated.
Define FBWS in a nutshell!!!
FBWS replaces conventional cable flight controls with an electronic interface that translates pilot commands into aircraft surface positions.
Flight deck control inputs are digitized and then sent to:
Three PFCCs where they are converted to electronic commands.
After flight deck control inputs are converted to electronic commands:
Commands are then transmitted to 10 Remote Electronic Units(REUs) which position control surfaces through hydraulic actuators.
Three PFCCs electronically blend what?
Signals from the flight deck controls, air data and inertial reference inputs, aircraft configuration, and control surface feedback data.
*Commands are computed to operate the flight control surfaces within the aircraft flight envelope(Normal Mode).
An internal priority logic selects how many PFCCs to control FBWS?
One is selected; other two monitor in standby mode.
What are the two distinct operating modes for FBWS?
Normal and Direct
With all component functioning, the FBW system operates in normal mode. The mode is comprised of:
Various pitch, roll, and yaw protections and limits.
Depending on system degradation, direct mode is subdivided into:
PFCC direct
REU direct
AFCU direct
Normal ground mode is active with aircraft weight on wheels(w.o.w). Characteristics of Normal ground mode are:
- Direct full travel authority of elevator
- Pitch rate damping
- Yaw damping at 70kts and above
- Direct control of horizontal stab trim
- Automatic speed bug setting to V2+10. If an engine fails, the speed bug is automatically reset to V2
- Noseup pitch attitude limit is set to 17 degrees
- Sidestick shaker stall warning function active above 60kts
- When both thrust levers are advanced for takeoff, nose down elevator is automatically applied to increase the nose gear loading until speed reaches 90kts.
Explain Pitch Compensation!!!
Automatic noseup pitch compensation, to maintain level flight, is provided for bank angles up to 33 degrees. Beyond this bank angle, aft sidestick must be applied!!!!
What is trim speed and how is it depicted?
Speed that is adjusted with pitch trim switch on sidestick; it is depicted as an unfilled cyan triangle on the PFD Tape.
Normal mode provides longitudinal maneuvering protections which are classified as:
Soft and hard envelope protections
Soft envelope limit provides:
Tactile, and in most cases, visual or audio cues, at the edge of the operational envelope.
Example of tactile cues:
stick shaker
Progressive increase in required sidestick force, because there is a built in soft stop within the system, which helps counter continued deflection
The soft stop, in itself, is a cue and can be overcome with force.
Hard envelope limit provides:
Limited safe excursion outside the operational envelope, but not beyond the structural limitation of the aircraft.
In normal mode, in flight the noseup pitch attitude limit is set to:
30 degrees
*Approaching any of these limits, FBW pitch authority is reduced to prevent excessive pitch(like LSAS)
In normal mode Below 110kts, the pitch attitude limit is reduced from 30 degrees to:
20 degrees @ 85kts
*Approaching any of these limits, FBW pitch authority is reduced to prevent excessive pitch(like LSAS)
In normal mode, on the ground, the noseup pitch attitude limit is:
17 degrees
*Approaching any of these limits, FBW pitch authority is reduced to prevent excessive pitch(like LSAS)
The nose down pitch attitude is limited to:
- 20 degrees
* Approaching any of these limits, FBW pitch authority is reduced to prevent excessive pitch(like LSAS)
VAOA Soft is:
High angle-of-attack protection that ensures the operational AOA is not exceeded @ sidestick soft stop
VAOA Hard is:
High angle-of-attack protection that ensures the operational AOA is not exceeded @ sidestick hard stop
True or False
Overspeed protection is only active when slats/flaps are retracted?
True
FBW limits bank angle to a maximum of:
80 degrees
*This limit reduces when near the aircraft operational flight envelope.
During maneuvers exceeding 1.55 g, ailerons are positioned trailing edge up to prevent:
Wing root bending
On a failed engine, the aircraft automatically rolls into a bank and slip of:
20 degrees or less of bank and a sideslip angle of 5 degrees or less.
