Flight Controls - Flaps and Slats

Question 1

Flight Controls - Flaps and Slats

What kind of flaps does the 787 have ?

Answer 1

• Regular trailing edge drooping flaps

* Krueger flaps on the leading edge, above the engines.

Question 2

Flight Controls - Flaps and Slats

How many modes of the Flap and Slat are there ?

Answer 2

3
• Primary
• Secondary
• Alternate

Question 3

Flight Controls - Flaps and Slats

In Primary mode, what hydraulic system powers the Flaps and Slats ?

Answer 3

The CENTER hydraulic system.

Question 4

Flight Controls - Flaps and Slats

What automatically triggers the Secondary mode ?

Answer 4

Any of the following occurence:
• Center hydraulic system failure,
• Control surfaces travel at less than 50% of the normal rate,
• Flap or Slat disagree is detected,
• Flap or Slat primary control failure,
• Primary mode fails to move the Flaps or Slats to their selected position,
• An uncommanded Flap or Slat motion is detected.

Question 5

Flight Controls - Flaps and Slats

Is Flap and Slat operation time the same in all 3 modes (primary, secondary and alternate) ?

Answer 5

No, it is greatly increased in secondary and alternate modes.

Question 6

Flight Controls - Flaps and Slats

Can the ALTN mode be automatically triggered ?

Answer 6

NO

The ALTN mode has to be manually selected.

Question 7

Flight Controls - Flaps and Slats

What happens when the ALTN FLAPS arm switch is pushed ?

Answer 7

• The alternate flight control mode is armed
• The alternate Flaps selector is armed
• Primary and Secondary modes are disabled
• Protections are no longer available (asymmetry/skew, uncommand motion etc)
• The Flap lever is disabled.

Question 8

Flight Controls - Flaps and Slats

In ALTN mode, how far do the flaps and slats extend ?

Answer 8

Slats ➝ middle position

Flaps ➝ 20

Question 9

Flight Controls - Flaps and Slats

In ALTN mode, in which sequence do the flaps and slats retract ?

Answer 9

Flaps first, then Slats.

Question 10

Flight Controls - Flaps and Slats

With the Flap lever in position 1, how are the Flaps/Slats positioned ?

Answer 10

Slats ➝ middle position
Flaps ➝ 0
0 / half Slats / 1 / Flaps only / 20 / Full Slats / 25 / Full Flaps / 30

Question 11

Flight Controls - Flaps and Slats

At which Flap lever position are the Slats fully extended ?

Answer 11

25

0 - half Slats - 1 - Flaps only - 20 - Full Slats - 25 - Full Flaps - 30

Question 12

Flight Controls - Flaps and Slats

On the ground, can Flaps be moved with only 2 hydraulic systems pressurized ?

Answer 12

NO
On the ground, all 3 hydraulic systems must be pressurized before flaps will move in order to avoid contact with an unpowered (drooping) spoiler.

Question 13

Flight Controls - Flaps and Slats

Between which Flap positions will the Flap load relief system function ?

Answer 13

15 to 30 position.

Load relief retraction is limited to Flaps 5.

Question 14

Flight Controls - Flaps and Slats

Is the Flap load relief system operative in Secondary or Alternate mode ?

Answer 14

NO, only in Primary mode.

Question 15

Flight Controls - Flaps and Slats

Between which airspeeds does the Slat relief load system operate ?

Answer 15

Above 240 kts ➝ Slats retract to middle position

Below 225 kts ➝ Slats re-extend to their selected position

Question 16

Flight Controls - Flaps and Slats

What is the Autogap function ?

Answer 16

At a high AOA, autogap fully extends the slats to increase the wing camber, thus increasing the lift and margin to stall.
The slats return to the middle position after the AOA decreases.

Question 17

Flight Controls - Flaps and Slats

When is the autogap function available ?

Answer 17

• In Primary mode
• Slats in the middle position (Flap lever between 1 and 20)
• Airspeed < 240 kts

Question 18

Flight Controls - Flaps and Slats

Is the autogap function available in Secondary mode ?

Answer 18

NO,
In Secondary mode, the system is too slow to respond to autogap requests.
The PREGAP function is used.

Question 19

Flight Controls - Flaps and Slats

What is the Pregap function ?

Answer 19

It replaces the Autogap function in Secondary mode :
The slats will automatically move to the fully extended position from the middle position when :
• Flap lever is NOT UP and,
• Airspeed < 240 kts

Question 20

Flight Controls - Flaps and Slats

When is the Cruise Flaps system available ?

Answer 20

• Primary mode
• Altitude > 25 000 ft
• 0.53 < Mach < 0.87

Question 21

Flight Controls - Flaps and Slats

What does the Cruise Flaps system do ?

Answer 21

Cruise Flaps improve the airplane’s cruise performance by symmetrically moving the flaps, ailerons, flaperons and spoilers based on aircraft parameters (weight, airspeed and altitude).

Question 22

Flight Controls - Flaps and Slats

When is the Assymetry/Skew protection available ?

Answer 22

In Primary and Secondary modes.

Question 23

Flight Controls - Flaps and Slats

When is the Uncommanded motion protection available ?

Answer 23

In Primary and Secondary modes.

Question 24

Flight Controls - Flaps and Slats

What is a “Disagree” condition ?

Answer 24

A disagree is detected when, after a commanded input, the Flaps or Slats :
• Do not move or,
• move too slowly (less than half the normal rate).

Only available in Primary and Secondary modes.

Question 25

Flight Controls - Flaps and Slats

Above what altitude is Flap extension inhibited ?

Answer 25

20 000 ft

It is also inhibited if Speed > 260 kts

Question 26

Flight Controls - Flaps and Slats

Above what Speed is Flap extension inhibited ?

Answer 26

260 kts

It is also inhibited if Altitude > 20 000 ft

Question 27

Flight Controls - Flaps and Slats

What will automatically happen if a Flap or Slat asymmetry is detected ?

Answer 27

The system will shut down.