Flap System *** Flashcards
How many Flap Control Units (FCUs) are provided?
• Three
What are the basic functions of the FCUs?
- Primary control
- Secondary control
- Indication and annunciation
How many groups of leading flaps are provided, and how are they normally powered?
- Three groups on each wing: outboard, midspan, and inboard section.
- Normally pneumatically powered from the bleed air duct.
What are the two groups of trailing edge flaps, and how are they powered?
- Inboard and outboard
* Inboard powered by hydraulic system 1 and outboard by system 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
How do of the FLAPS operate when the FCUs in primary mode.
- LEF are driven pneumatically to the selected position.
* TEF are driven hydraulically to the selected position.
How do of the FLAPS operate when 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 midspan leading edge flap group?
What EICAS message will be displayed
• Both groups switch to secondary mode
EICAS “Flaps Primary”
What happens if a failure occurs in a leading edge flap group on one Wing?
• The flap groups on both wings change to secondary mode after a short
time delay.
• The non-affected side completes movement before changing to
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 lever 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 leading edge flaps
- All flap positions are displayed
- White box outline shows LEF group retracted
- White crosshatch shows LEF 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 trailing edge flaps.
- 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 the 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 lever 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?
- Outboard leading edge flap groups extend.
* Trailing edge flaps move to Flaps 5 position.
What flap sequencing occurs when using alternate flaps?
• During extension, all LEF and TEF groups extend immediately.
• TEF extend to a maximum 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, the flaps retract to
25.
• If airspeed is excessive at flaps 25, the 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 seconds
What is the affect on the flap system during engine reverse thrust operation?
• Inboard and midspan leading edge flaps retract automatically
How are trailing edge flaps powered?
HYD SYS 1 and 4
4_1 || 1_4
Why does FCU switch to secondary mode and how do flaps function while in it?
How are flaps commanded to extend/retract in secondary mode?
If any group fails in primary mode, the FCUs switch to secondary mode for the related group, driving the group through electric motors.
Still commanded with the Flap Lever.
LEF white box outline?
Retracted
LEF white crosshatch?
In transit
LEF solid green box?
Extended
LEF amber box outline, crosshatch, or solid box?
Drive unit inop
What does amber “X” mean on expanded flap display?
Position sensor inop
ALTN Flaps Selector to EXT?
- LEF and TEF extend electrically
- Max extension is Flaps 25
ALTN Flaps Selector RET?
- TEF and LEF flaps retract electrically
EICAS FLAPS CONTROL?
- All 3 FCUs have failed - or-
- Alternate flaps ARM switch in ALTN
EICAS FLAPS DRIVE?
One or more flap groups have failed to drive in secondary mode or an asymmetry condition is detected.
EICAS FLAPS PRIMARY?
One or more flap groups operating in secondary mode.
How does Flap Load Relief work?
If airspeed limit is exceeded for FLAPS 30, they are retracted to 25. If airspeed is still excessive, they are further retracted to FLAPS 20.
Similarly, if FLAPS 25 speed is exceeded, they retract to FLAPS 20.
Where are the mechanical flap gates?
FLAPS 1 (LEF Inadvertent Retraction)
FLAPS 20 (Go Around)
Secondary flap extension from FLAPS 1 to FLAPS 5 takes approx how long?
4 minutes
