Flap System - Question Bank Flashcards
How many Flap Control Units (FCUs) are provided?
3
What are the basic functions of the FCUs?
- Primary Control
- Secondary Control
- Indication & Annunciation
How many groups of leading edge flaps are provided?
How are they normally powered?
- 3 groups on each wing: inboard, midspan, and outboard
- Normally pneumatically powered from the bleed air duct
What are the two groups of trailing edge flaps?
How are they powered?
- Inboard & Outboard
- Inboard: Hyd Sys 1
- Outboard: Hyd Sys 4
How are opposite trailing edge flaps connected?
Mechanically in order to maintain symmetry
What protection features do FCUs provide for trailing edge flaps in primary mode?
- Asymmetry protection
- Flap load relief
- Flap position information to EICAS and other systems
What protection features do the FCUs provide for trailing edge flaps in secondary mode?
- Asymmetry protection
- Flap position information to EICAS and other systems
Describe the function of the FCUs in primary mode.
- LEF are driven pneumatically to the selected position
- TEF are driven hydraulically to the selected position
Describe the function of the FCUs in secondary mode.
- If any flap group fails to move to the commanded position, the FCUs switch to secondary mode for the related group
- The flap group is driven through electric motors
What happens if a primary control failure occurs in either the inboard or mid-span leading edge flap group?
Both groups switch to secondary mode
What happens if a failure occurs in a leading edge flap group on one wing?
- The flap groups on both wings change to the secondary mode after a short time delay
- The non-affected side completes movement before changing to the secondary mode, due to the rapid rate of primary mode flap movement
What happens immediately if a trailing edge asymmetry is detected?
- Primary mode is immediately shut down for the asymmetric group
- The FCUs do not use secondary mode
- FLAP DRIVE EICAS caution message
What EICAS advisory message displays if all three FCUs fail in their control function?
-“FLAPS CONTROL” EICAS Caution Message
How does the Flap Alternate Control Mode work?
- Bypasses the FCUs
- Can be manually selected
- All flaps are extended or retracted by electric motors
Is there any asymmetry protection in alternate flap mode?
No
State the actions that occur when the Alternate (ALTN) Flaps Arm switch is pushed.
- Arms flap alternate control mode
- Arms Alternate Flaps selector
- Shuts off primary and secondary mode operation
- Flap level inoperative
What is the maximum extension of the trailing edge flaps in alternate mode?
25
Describe the secondary mode or non-normal expanded flap position indication for LE flaps.
- All flap positions are displayed
- White box outline shows LEF group retracted
- White crosshatch shows LE group in transit
- Solid green box shows LEF group extended
- Amber border, crosshatch, or solid box- drive unit inop
- Indicator motion is continuous between flap detents
Describe the secondary mode or non-normal expanded flap position indication for TEF
- White - position of inboard and outboard TEF
- Amber - asymmetry or drive failure in related group
- Indicator is continuous between flap detents
What does an amber “X” mean on an expanded flap display?
Position sensor for respective flap has failed
Describe the Alternate Mode Expanded Flap Position indicator.
- All flap positions displayed
- Flap position index marks at 5 and 25
- Indicator motion is continuous between flap detents
Describe the flap position indication on EICAS if the standby bus is only powered AC bus.
- The left wing TEF sensors are not powered
- An amber X is displayed on the left outboard and inboard TEF indications
- An expanded indication is displayed
What flaps extend when the flap level is moved from Up to Flaps 1?
-Inboard and midspan leading edge flap groups
What flaps extend when the flap lever is moved from Flaps 1 to Flaps 5?
Trailing edge flaps move to Flaps 5
What flap sequencing occurs when using alternate flaps?
- During extension: all LEF and TEF groups extend immediately
- TEF extend to a max of 25
- During retraction: all LEF groups retract after inboard TEF are completely retracted
Describe flap load relief
If airspeed limit is exceeded:
- with flaps 30 selected- flaps retract to 35
- with flaps 25 selected- flaps retract to 20
-Flap load relief is not available in secondary or alternate mode
How long does the flap indication on primary EICAS remain displayed after all flaps are up?
10 secs
What is the affect on the flap system during engine reverse thrust operation?
Inboard and midspan LEF retract automatically
