L-1011 Trainer Installation: Glare Shield Replacement

L-1011 Trainer - Glare Shield - Autopilot

The L-1011 trainer that we got from Delta did not come with any real instrumentation. All of the instruments you have been seeing as part of the blog postings are instruments we replaced with real flight hardware used on actual L-1011s. Today, we replaced the last photo mock up on the simulator ... the glare shield autopilot and radio components. In the image below you can see the image that was pasted onto a plate and mounted in place of the autopilot under the glare shield. This has now been replaced with a custom made plate and with the actual control components:

Before

L-1011 Trainer - Original Autopilot Photo Replica

After

The glare shield is not only home to the autopilot components, but also holds the VHF NAV 1 and VHF NAV 2 radio as well as the RADIO/NAV selector for the HSIs, a ENGINE 2 warning light and a FIRE warning light.

L-1011 Glare Shield

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 Autoflight: Autopilot Warnings (22-14)

The AFCS WARNING annunciators show changes in autopilot status resulting from failures detected by the autopilot monitors. The example above shows an alert created be the autopilot state transition from "engaged" to "disconnected".

L-1011 Autoflight: Verification of Command Mode Engagement (22-12)

Each time a command mode is selected, both autopilot computers will respond by displaying the selected mode on the respective AFCS MODES annunciator. Each autopilot computer has an AFCS MODES annunciator located on the main instrument panel. In the example above, autopilot A is in the command position and vertical speed has been selected as a pitch command mode. The "VS" light on the Pitch Panel indicates mode selection, verification of both autopilot computers operating in the "VS" pitch mode is accomplished by observing the "VS" message in both AFCS MODES annunciators.

"VS" is also displayed int he PITCH Panel window (digital autopilot system only) along with the actual vertical with the actual vertical speed at the time of engagement.

L-1011 Autoflight: Command Modes (22-10)

Once an autopilot lever has been placed in CMD or or command, it continues to act as if it were in control wheel steering until pitch or roll command modes are engaged.

Command modes are selected by pressing the switchlights along the top of the autopilot panels. Only one pitch mode and one roll mode can be selected at a time. Selection of a second pitch or roll mode will automatically disengage the first pitch or roll mode. Selection of a command mode will cause both autopilot computers to operate in that mode even though only one computer is engaged.

The switchlight for each mode will illuminate to show positive mode selection.

L-1011 Autoflight: Control Wheel Steering (22-9)

There are two basic modes of operation that an autopilot can be engaged in, control wheel steering (CWS) or command (CMD mode. In control wheel steering, the autopilot receives its pitch and roll inputs from the control wheel. The aircraft will remain where you put it. If you move the control wheel with a force of four pounds or more, the aircraft will respond. When you release the controls, the aircraft stays where you put it. Remember, only one autopilot can be engaged at a time.

When an engage lever is moved to CWS, it is held in that position electrically after the autopilot/flight director computer determines that the system is working properly. Anytime the signals are not valid, the lever will automatically drop to the OFF position.

L-1011 Autoflight: Flight Director Command Bars (22-8)

As you already know, each flight director switch connects its respective autopilot/flight director computer to command bars on the same side. Autopilot A to the Captain's command bars, autopilot B to the First Officer's command bars. Either or both flight directors may be selected simultaneously and are independent of autopilot engagement. With the flight director switch off, the command bars are biased out of view as shown on the First Officer's side. Placing the flight director switch to ON will bring the command bars into view as shown on the Captain's side.

In the pictured example:

Autopilot/flight director computer A will now provide steering information to the Captain since both autopilot autopilot levers are off, but the FD for the Captain's side is on. With Autopilot lever A on, autopilot A would fly the aircraft in pitch and roll and the flight director command bars would indicate to the Captain what the autopilot is doing.

L-1011 Autoflight: Engage Levers (22-7)

Autopilot A has an FD switch to engage the Captain's flight director (APFD Engage Panel) and a lever to engage one side of the dual pitch and roll autopilot servos. Both the Captain's flight director and one side of the autopilot servos can be driven by autopilot/flight director computer A. The First Officer's side does the same thing with autopilot B.

Either autopilot is capable of flying the aircraft in pitch and roll. Yaw is automatic in pitch and roll and will be discussed in a later blog posting.

Both flight directors may be on at the same time, each using individual autopilot computers. Only one autopilot may be engaged at a time. The second autopilot is electro-mechanically locked in the OFF position. A normal configuration is to have one autopilot engaged and both flight directors on. The only exception for both autopilots to be engaged is when the approach/land mode is engaged.

L-1011 Autoflight: Two Independet Autopilots (22-6)

The autoflight system contains two independent dual-channel autopilot/flight director computers that are always on and synchronized with the aircraft attitude. An autopilot/flight director system engage panel, located in the center of the pilot's glareshield, is used to engage either a flight director, an autopilot servo or both with the autopilot/flight director computers. The autopilot/flight director system engage panel is effectively divided in half. The left side is for autopilot A and the right side is for autopilot B.

L-1011 Autoflight: ADI and HSI (22-5)

Autopilot operation can be monitored on the attitude indicator and horizontal situation indicator (HSI). The attitude director indicator (ADI) has flight director (FD) command bars that come into view when the respective flight director is engaged. Command bars provide steering information to the pilot when the aircraft is being flown manually. For automatic flight, the command bars provide the pilot with a visual indication of what the autopilot is doing.

L-1011 Autoflight: Features and Controls (22-3/4)

The autopilot and flight director controls are located in the center of the pilots' glareshield. some of the features provided by the L-1011 autopilot are:

• Two independent autopilots that are always synchronized to the aircraft attitude.
• One set of autopilot controls.
• Flight directors that use autopilot computers and controls.
  
• Roll and pitch attitude hold when using control wheel steering.
• Automatic landing for Category IIIb (CAT IIIb) operations.
• Takeoff guidance using the flight directors.
• Automatic go-around using the autopilot and
• Turbulence smoothing.
  

L-1011 Autoflight: Flight Profile and Category Chart (22-1)

The autoflight system provides manual and automatic guidance and control of the aircraft throughout the total flight profile from takeoff through the landing profile.

The L-1011 is certified for Category 3B (CAT IIIb).

Original Flight Hardware: Heading/Pitch Mode Panel

I finally added the last panel for the autopilot of the Lockheed L-1011. The panel that completed my set is the HEADING/PITCH MODE panel. It's actually a really neat device, it has a vertical speed dial that is synchronized to the vertical speed of the aircraft and can also be overridden with the dial to the right of it. The idea is that in control wheel steering the pilot would pitch the aircraft to the correct vertical speed and then engage the autopilot. The panel also has the heading input for the automatic flight system.

Below is a picture of the complete autopilot of the Lockheed L-1011. This one is completely analog, the -500 models also had a digital version.


The other switch elements on the panel are:

• VS ... Vertical Speed (Hold)
• ALT ... Altitude (Arm / Hold)
• IAS ... Indicated Airspeed (Arm / Hold)
• MACH ... Mach Speed (Arm/Hold)
• HDG ... Heading (Arm/Hold0

The various modes will be indicated on the AFCS Mode Indicators.


Panel Location

Avionics Bending: AFCS Warning Panel (Analysis)

The AFCS WARNING panel is the last of three panels for the AFCS system that we will examine for the Lockheed L-1011 cockpit. In previous postings we looked at the AFCS MODE panel and the INSTRUMENT COMPARATOR panel. Like the other two panels, the AFC WARNING panel uses solenoid driven flags to indicate warning messages.

This particular unit was made COLLINS AVIONICS and goes hand in hand with the AFCS Mode display.



Whenever a flag is raised on the panel, the ALERT button will blink until the ALERT button has been pressed. Pressing the button for a 2nd time resets the flag(s). The large print board on top of the instrument implements the former described feature.

Top View


Right hand side view. Here you can see the typical push solenoids used for the flags.


Bottom View.


Left hand view.


The two test switches, one in the top left and top right corner of the instrument, will show two different warning states each flag can be in.


Test 1 Button: AP DISC (Autopilot Disconnect), ATS DISC (Auto Throttle System Disconnect), AP LIMIT (Approach with Limited functions), NO FLARE (Automatic Flare not possible)


Test 2 Button: NO DUAL (No dual autopilot information for auto-land), NO GA (No automated go-around available). NO ALIGN (The Yaw Stability Augmentation System can not align the aircraft with the localizer), CMD DISC (Autopilot Command Mode not available).

Avionics Bending: NAV Mode Select Panel (Analysis)

We looked at the NAV MODE Panel in an earlier posting, so I am not going to go to deep into the detail as to how it works in combination with the autopilot on the Lockheed L-1011. The autopilot modules for the L-1011 were built by Collins Radio Company.


Besides the mode switches on top and the bearing selectors (one for NAV1 and one for NAV2) the NAV Mode panel has a rather interesting rotary switch. The switch has a SPLIT, 1 and 2 setting. SPLIT allows the captains and the First Officers NAV to be sourced independent. The "1" setting uses NAV1 for both inputs, and "2" uses NAV2 for both input. There is an electromechanical release element that automatically returns the switch back to "SPLIT" (see last picture in this posting).

The instrument is greatly dominated by a total 8 synchro devices used for angular encoding of the Course Selector.

Top View


Right Hand Side View


Bottom View


Left Hand Side View


The top of the instrument has two large Synchro Resolvers, one for each of the course selectors.


On each side of the instrument are two Control Transformers (CT) and one Differential (CD) for each course selector.


We will talk about the interaction of Control Transmitters, Control Transformers, Differential Resolvers, Resolvers and Transolvers in a later posting. If you are, however, interested in how they work, I would recommend you take a look at MIL-HDBK-225A (it's a great primer).


The image above shows the digit tapes ... they are like little conveyor belts with numbers printed on them. The course selector knob rotates the tapes.

Below is the rotary switch release mechanism. It is basically a solenoid that lifts pressure off the rotary disk an allows it to snap back into the "SPLIT" position, which is the top of the 3 position on the rotary switch.