L-1011 Flight Controls: Surface Hydraulic Systems (27-10)

The L-1011 has four (4) hydraulic systems that operate the individual surfaces. Hydraulic pressure is provided as follows:

• The Number 1 Engine drives the A hydraulic system.
• The Number 2 Engine drives the B and C hydraulic systems.
• The Number 3 Engine drives the D hydraulic system. 

The Rudder receives hydraulic pressure from three different systems: A, B and C
The Stabilizer receives hydraulic pressure from all four hydraulic systems: A, B, C, and D

The Ailerons are driven by different hydraulic systems depending on their location along the wing:

Inboard Ailerons us 3 systems. On the left hand side they use systems A, B and C and on the right hand side they use systems B, C and D. For the outboard ailerons on the left hand side we use system A and B and on the right hand side systems B and D.

The Flaps and Slats are powered by two systems: A and C

The hydraulic systems for the Spoilers are rather diverse:

• No.1 Spoiler Limiter System - B system.
• No.2 and 3 Spoiler Limiter System - D system.

Left Wing

• No. 1, 4 and 6 Spoiler - B system
• No. 2 Spoiler - A system
• No. 3, 4 and 5 Spoiler - C system

Right Wing

• No. 1, 4 and 6 Spoiler - B system
• No. 2 Spoiler - D system 
• No. 3 and 5 Spoiler - C system

Note that the No. 2 spoilers are the odd power sources relating to their wing engines.

L-1011 Flight Controls: Leading Edge Slats (27-8/9)

The L-1011 has a leading edge slats system with seven slat panels on each wing. Three inboard of the engine strut and four outboard. The Slats are driven by hydraulic motors called a slat power drive unit. The slats attach to torque tubes with ball screw actuators.

Above is an image of the wing chord with a conventional leading edge slat. 

L-1011 Flight Controls: Surfaces (27-4-8)

The L-1011 has a Flap with a Vain.

There are four panels on each wing of the L-1011 that make up the trailing edge flap system. These flaps are powered by hydraulic motors through torque tubes and ball actuators. 

The secondary Flight Controls are composed of the four double-slotted fowler-type flaps and the seven slats on each wing. 

Above is the Flying Stabilizer used on the L-1011 which is mechanically slaved to the elevator.

L-1011 Flight Controls: Primary Flight Controls Description (27-1)

The L-1011 Flight Controls are basically conventional surfaces which are fully hydraulic powered. There are no "tabs" on any surfaces. The primary flight controls are used to control or steer the aircraft; they are:

• Stabilizer
• Ailerons
• Spoilers
• Rudder

The secondary flight controls are used to improve slow speed performance by increasing lift and drag; they are:

• Flaps
• Slats

Here is a more detailed description of the primary and secondary flight control elements:

The Primary Flight Controls (PFC) consists of the movable surfaces that control the aircraft around the three control axes. These controls are fully hydraulic. Rudder and Aileron Trim is provided by a mechanical means. There are no external Trim Tabs used on any of the control surfaces on the L-1011.

Stabilizer/Elevator 

Pitch control is accomplished by positioning the movable flying horizontal stabilizer. The entire stabilizer and elevator move as a single control unit.

Ailerons 

Like other large jet aircraft, inboard and outboard ailerons are used. A difference is that all four ailerons are full time. The outboard ailerons do not lock out in cruise flight. This feature allows the use of Action Controls (ACS) whereby wing bending is reduced at higher weights by use of symmetrical outboard aileron inputs.

Spoilers 

The twelve Spoiler Panels, six on each wing, perform four functions: They act as speed brakes, augment roll, provide direct lift control (DLC) and serve as automatic ground spoilers.

Rudder 

The Rudder is a single control surface. It operates to provide YAW Stability Augmentation, Full Time Turn Coordination and Runway Alignment during automatic landings as well as the traditional rudder functions.

Avionics Bending: AFCS Warning (Pinout)

The AFCS Warning panel is similar to the AFCS Modes panel in the way that it also uses flags to indicate autopilot fault states. In addition to the flags, the AFCS modes panel has an ALERT switch that has to be pressed by the pilots in order to clear and acknowledge the alert flag. The instrument is typically powered from the 28V DC bus on the aircraft but works perfectly find from a 24V DC source.

There are two TEST switches that actuate the flags and the ALERT switch electronics. The ALERT switch itself is used to both clear the blinking ALERT warning and to also clear the fault flag. Watch the short video below if you are interested to see the AFCS Warning panel in action.

The individual flags can be actuated by pulling the associated pin to Ground. Below is the pinout for the AFCS Warning panel as used on the L-1011. 

Pin	#	Pin Assignment	Value
A	41	Power	28VDC
B	40
C	39	Instrument Test Switch	GND
D	38
E	37	NO DUAL (A) - no clear	GND
F	36	AP LIMIT (R) - reset enable	GND
G	35
H	34	NO ALIGN (A) - reset enable	GND
J	33
K	32	NO FLARE (A) - reset enable	GND
L	31	NO FLARE (A) - reset enable	GND
M	30	CMD DISC (A) - can be cleared	GND
N	29	CMD DISC (A) - can be cleared	GND
P	28
R	27
S	26
T	25
U	24
V	23
W	22	Instrument Lighting	GND
X	21	Instrument Lighting	5VDC
Y	20
Z	19
a	18	NO DUAL (A) - no clear	GND
b	17
c	16
d	15
e	14
f	13
g	12
h	11	ATS DISC (R) - can be cleared	GND
i	10
j	9
k	8
m	7
n	6	AP DISC (R) - has to trigger together with 1	GND
p	5	NO GA (A) - can be cleared	GND
q	4
r	3
s	2
t	1	AP DISC (R) - has to trigger together with 6	GND

L-1011 ECS: Cold Air Plenum (21-14)

Outputs from all three air conditioning packs discharge through a check valve and into a common chamber called the cold air plenum.

The cold air plenum is a rectangular box which receives air from the three air conditioning packs, then mixes and distributes the available air to the four aircraft zones. The plenum is decided down its whole length by a perforated baffle. The air from packs 2 and 3 and approximately 60% of pack No. 1 air is mixed together for distribution to the three cabin zones. The other 40% from pack No. 1 is diverted by another baffle which directs the supply towards the flight station outlet duct.

The plenum is located at the rear right hand side of the FESC.

Avionics Bending: AFCS Modes (Pinout)

Finished connecting the AFCS Modes displays to the relay boards. The AFCS MODES display is used to display the autopilot modes and to indicate state changes. For example from ALT ARM to ALT ... which indicates a change in autopilot state from altitude arm to altitude capture. I have a more detailed description of this instrument in several other blog postings such as: AFCS Training Manual Description, AFCS Modes Instrument Analysis and Localizer Capture Example. Here is what the instrument looks like:

And here is a short video of the instrument powered up and connected to the relay board backend. The instrument requires a power source between 24VDC and 28VDC and a 5VDC power source for instrument lighting. The individual flag solenoids are operated by pulling the respective pin to Ground.

The pinout below is for a an AFCS Modes panel used on an L-1011 with Thrust Management (TM). On AFCS Modes panels for L-1011s without TM, the THR MGT flag will simply say "TEST".

Pin	#	Pin Assignment	Value
A	32	Unused
B	31	Power	28VDC
C	30	A/L (W)	GND
D	29	A/L ARM (B)	GND
E	28	LOC (W)	GND
F	27	LOC ARM (B)	GND
G	26	GS (W)	GND
H	25	GS ARM (B)	GND
J	24	ALIGN (W)	GND
K	23	Instrument / Test Switch Ground	GND
L	22	ALIGN ARM (B)	GND
M	21	FLR ARM (B)	GND
N	20	VOR (W)	GND
P	19	THR MGT (W)	GND
R	18	Unused
S	17	Unused
T	16	Unused
U	15	Instrument Light
V	14	Instrument Light	GND
W	13	HDG SEL (W)	GND
X	12	TURB (W)	GND
Y	11	VS (W)	GND
Z	10	ALT (W)	GND
a	9	TO/GA (W)	GND
b	8	FLARE (W)	GND
c	7	ROLLOUT (W)	GND
d	6	VOR ARM (B)	GND
e	5	L NAV (W)	GND
f	4	ALT ARM (B)	GND
g	3	WINDSHR (W)	GND
h	2	IAS (W)	GND
j	1	VNAV (W)	GND