L-1011 Trainer Installation: Integral Instrument Lighting - Glare Shield

L-1011 Trainer Build-Out

Jim Blasco and myself are slowly working our way with the instrument lighting from left to right. Today we started putting cabling in place for the glare shield components. The Lockheed L-1011 glare shield is home to the controls for the Autoflight system as well as the navigation radios. In the image below you can see the initial state of the light plate illumination for the Thrust, Pitch and Heading module as well as a partial light up of the Autopilot/Flight Director engage panel. 

The Micro Fiche that we received from Paul Talbot a few months ago has proven absolutely vital to the project because it has allowed us to attempt to re-create the original L-1011 cabling as close as we can. The APFD System on the L-1011 relies heavily on Synchros ... so getting the AP to work close to the real thing will be an interesting challenge, however, I have been cooking on a rather unconventional synchro solution that I will show you guys at a later point.

L-1011 Glare Shield Lighting

Avionics Bending: APFDS Engage Panel - Part 1

L-1011 APFDS Engage Panel

The next component of the Lockheed L-1011 Autoflight system is the APFDS Engage panel. This panel is located in the middle of the L-1011 Glare Shield (see below)

The panel has switches for the Autopilot A and B as well as the Left and Right Flight Director (FD). The Autopilot of the L-1011 as both a Control Wheel Steering (CSW) modes as well as a full Command (CMD) mode. Both the A and the B system of the auto flight systems work independent unless the aircraft is in Approach/Land (A/L) mode during which both automatic flight systems are required. 

The panel that I am using for this demo and the test integration with X-Plane is one of several APFDS Engage panels we have at the museum. This particular panel is a little beaten up, but, it makes for a great test instrument. The switches on the panel have long extensions and are frequently called "bat-switches". The flight director switches are normal toggle switches with the SYNC position having a spring return. The autopilot swathes are magnetic latch switches that will be held in certain positions by solenoids. For example, if the the autopilot system is not ready, the switches can not be moved out of the OFF position, or, if engaged and the pilot presses the A/P Disengage switch on the control wheel ... the bat switches will return to the OFF position. Below is a short video showing the action of the switches as well as a schematic of the panel taken from the WDM fiche.

APFDS Engage Schematic - From L-1011 WDM

Avionics Bending: L-1011 Autopilot - Pitch Mode and Heading Panel

The Avionic Flight Control System (AFCS) on the L-1011 is controlled via a number of panels located on the L-1011 glare shield. Most commonly these panels are referred to as the "autopilot" control panel. The autopilot on the L-1011 is a digital system that had analog inputs ... as you can see in the image above and the images following below. The later L-1011-500s had a digital AFCS panel also located on the glare shield. The digital version of the AFCS panel is not easy to find and there was one on eBay a few weeks ago and someone snatched it right from under my nose ... i am still sore about that one.

Anyway, in this posting I show you the status of my work with one of the panels ... the Heading/Pitch Mode Panel. The panel is located on the left hand side of the autopilot panel assembly and came in two version; one version that is like the one shown above and another that combined the Thrust and the Heading/Pitch Mode panel together (as seen below).

The right hand side of the panel has an engage button for heading control ("HDG") as well as a turn knob and a display for the selected heading. This side of the panel directly controls the L-1011's Roll Computer. In the image below the Roll Computer is engaged and the heading is set to 93º.

The left hand side of the same panel has the inputs for the aircraft's Pitch Mode. The L-1011 can pitch for 4 different modes:

• Vertical Speed (VS)
• Altitude 
• Indicated Airspeed 
• Mach Speed

The image below shows the Vertical Speed mode set on the L-1011's Pitch Computer and a target vertical speed for 1500 feet per minute climb.

There Vertical Speed controls on the panel are quite interesting. But more about them when I show you the schematic for the instrument later on. The ALT mode, when engaged holds the aircraft altitude at the moment of engaging the autopilot. The pitch for Indicated Airspeed and Mach is pretty self explanatory.

In the image below we would be holding the current altitude with the autopilot as well as the aircraft's heading. In other words, both the L-1011's Pitch and Roll Computers are engaged and, when the AFCS system is set to CMD will control the aircraft pitch and roll axis.

So now a few words about the VERT SPEED windows and the DN/UP switch. Prior to engagement of the VS mode, the tape in the the VERT SPEED window shows the aircrafts vertical speed. So in other words, unless "VS" is lit up, the VERT SPEED window will show the same indication as the vertical speed indicator. Once the VS mode is engaged the motor for the tape disengages and vertical speed adjustments can be made with the thumbwheel.

I have not gotten that tape motor part to work yet, however, it shouldn't be too hard to do. Below is the schematic for the VERT SPEED and DN/UP thumbwheel:

And a more enlarged view of the same schematic showing the ADC and Pitch Computer schematics as well:

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: Go-Around Mode (22-54)

If the takeoff/go-around switch is pressed while on the approach, the speed command system will agin shift into alpha mode for a go-around. the speed command system will cause the autopilot/flight director computers to react to a missed approach and a go-around. The autopilot engaged will pitch the nose of the airplane to provide for 1.25Vs minimum speed or 17.5º climb, whichever produces the higher airspeed. The pilot must provide the throttle movement.

L-1011 Autoflight: Thrust Management Mode (22-50)

In the trust management mode, commands from the thrust management system control the throttles to regulate engine power in climb, and descent. Thrust information is also displayed on the attitude director indicator FAST/SLOW needle.

Verification of mode selection is accomplished by checking the thrust management message on both AFCS modes annunciators. The fast/slow needle will now display thrust information.

Thrust management will also disengage when turbulence or go-around mode is selected, flaps are set to greater than 30 degrees, turning off both ATS systems on the FCES panel or pressing the throttle disconnect switch.

L-1011 Autoflight: Speed Command System (22-47/48)

The speed command system is independent of autopilot operation, but may be used with the autopilot.

The speed command system provides automatic control of the throttles and control of the FAST/SLOW speed deviation pointer on both attitude director indicators. The auto throttles and FAST/SLOW pointers are controlled from the Thrust/Heading/Pitch mode panel located on the left edge of the pilots' glare shield. Autothrottle system computer switches are located on the flight control electronics system panel in the pilots' overhead.

the ATS 1 and ATS 2 switches, on the flight control electronics system (FCES) panel, control the output of each speed command computer channel. The switches are normally latched and dark. To turn the system off, unlatch both switches.

With both switches latched and dark, the speed command is indicated fully time by the FAST/SLOW pointer on each attitude director indicator.

L-1011 Autoflight: Altitude Alert (22-46)

The altitude alert lights are located on the Captain's and First Officer's instrument panel. When the aircraft is within 750 ft. of the selected altitude the steady amber ALTITUDE light will illuminate and an audio C-Cord alert will sound.

When the aircraft is within 25 ft. of the selected altitude, the altitude light will go out. The altitude light will remain extinguished as long as the aircraft remains within 250 ft. of the selected altitude.

If the aircraft leaves a selected altitude without resetting he altitude warning, you will get a flashing altitude light and audio alert when the aircraft departs more than 250ft from the assigned altitude.

L-1011 Autoflight: Altitude Capture (22-27)

In the example above (sorry for the poor image quality) our aircraft is using vertical speed as pre-capture guidance for altitude select. Notice at the bottom of the climb that VS was selected and is engaged and the aircraft is climbing at 800 feet per minute. The selected altitude is 5,000 feet, ALT SELECT has been selected by dialing in the new altitude and the computers have been armed.

At capture, the VS light would extinguish. Because of the different closure rates the capture point changes. At a vertical speed of one thousand feet per minute, the capture point would be approximately two hundred and sixteen feet, or approximately 10 seconds from the selected altitude. A smooth, asymptotic capture is possible because the computer senses the altitude error and the rate of closure on the selected altitude, and initiates the required pitch maneuver sufficiently in advance to perform the capture maneuver without imposing an excessive change in the flight load factor (g).

At eight feet from the selected altitude, track is established and the ALT light will illuminate and the ALT ARM message on the AFCS modes annunciations will change to ALT.

An automatic capture can also be made in CWS, provided that a flight director is on (the system cannot be armed in CWS alone), but the capture will not be asymptotic unless flight director guidance is followed. In a "hands off" FD/CWS capture, the capture maneuvering is not inititated until the the selected altitude is passed through, so that there will be some overshoot. On reaching the selected altitude, CWS/FD is the same as WMD or CMD/FD in that the APFDS automatically engages the ALT Hold mode.

The Altitude Select knob performs two services simultaneously. Not only does it select an altitude to be captured, but it also selects the reference altitude for the altitude alert system which will be discussed later.

The desired altitude can be selected and the mode armed for capture at any time, even before takeoff. It will remain armed until the altitude selected is being traced, or until it is disarmed by a second actuation of the ARM switch, by selection of TURB, by selection of a difference altitude, or by switching off both flight directors and both autopilots. Interim altitudes can be captured, held, and released by appropriate actuation of the ALT switch without disarming the ALT Select mode. When this id done, there will be simultaneous annunciation of the Altitude Hold and Altitude Select modes.

L-1011 Autoflight: Altitude Select Mode (22-26)

Altitude select mode provides the capability of selecting a desired altitude to be captured. It can be used for either autopilot control or flight director guidance and is compatible with any roll axis mode.

Engagement of altitude select is accomplished by entering the desired altitude in the altitude select window using the altitude select knob. Below 10,000 feet a twenty-foot change in altitude will automatically arm the altitude select mode. Above 10,000 feet, a 100-foot altitude change is required. Any altitude between 0 and 59,000 feet may be selected.

Verification of mode engagement is accomplished by observing the ALT ARM message on both AFCS MODES annunciators.

The mode may be manually released by disengaging both flight directors and disconnecting the autopilot from the command (CMD) configuration. It will be automatically released if a required interlock function is lost or, if after initiation of the altitude capture maneuver, a superseding pitch axis mode is selected.

If an autopilot is not engaged in CMD, and the ALT Select Flight Director Guidance Commands are followed, the altitude capture maneuver will be asymptotic, with subsequent automatic engagement of the ALT Hold mode for flight director guidance only.

L-1011 Autoflight: Altitude Hold Overshoot (22-25)

Altitude hold is a command mode which provides automatic control of barometric altitude. When altitude hold is engaged, the aircraft will maintain the selected altitude with one autopilot engaged in command or control wheel steering, and provides flight director guidance to maintain altitude when in manual control with a flight director engaged.

Altitude hold maintains the selected altitude by means of pitch control and therefore is not compatible with any other pitch mode. Altitude hold is compatible with the autothrottle system and with all heading and navigation modes until glideslope capture occurs.

The barometric pressure reference for the altitude hold mode is the instantaneous pressure existing at the time the ALT switch is pressed or the mode is engaged. When the aircraft is climbing or descending at the time of manual engagement, an overshoot will occur but the airplane will return to and capture the engagement altitude whether in command or control wheel steering. Any flight director guidance mode can be engaged while in control wheel steering.

L-1011 Autoflight: Vertical Speed Engagement (22-24)

In this example, the aircraft is climbing at 1,000 feet per minute. The vertical speed window indicates 1,000 feet per minute and the thumb-wheel has no effect. When vertical speed is selected by pressing the "VS" switch, the VS light will illuminate indicating mode selection. Remember, verification of mode selection con only be made by checking for the VS message displayed in both AFCS MODES annunciators. The vertical speed thumb-wheel is now active and is adjusted to a new vertical speed of 800 feet of climb per minute. The aircraft will automatically pitch over and maintain a vertical speed of 800 feet per minute.

L-1011 Autoflight: Turbulence Mode (22-20)

Turbulence mode provides pilot-assisted, constant attitude flight through turbulent air. The autopilot control authority is reduced in order to soften its response to attitude changes caused by the turbulence.

Turbulence is an autopilot mode only and cannot be selected unless an autopilot is engaged. The TURB mode may be selected any time either autopilot is in CWS or CMD and A/L TRACK or GO AROUND is not established. The TURB light will illuminated indicating mode selection. Verification of mode engagement is accomplished by checking for TURB legend on in both AFCS MODES annunciators. When turbulence is selected while the autopilot engage lever is in the CMD position, the solenoid held lever drops from CMD to CWS. This action essentially cancels all other modes.

No other mode can be selected while the turbulence mode is engaged. The turbulence mode can only be released by pressing the TURB switch a second time or by disengaging the autopilot. Either of these actions then, is a prerequisite to resuming normal autopilot-controlled flight after a turbulence encounter.

If a flight director is also on when turbulence is selected, its command bars will be biased out of view but no FD warning flag will appear. When TURB is canceled, the command bars will return if the FD switch was left on but it will have a new reference. The new reference is the attitude existing at the time of TURB cancellation since all previous modes were canceled when TURB was selected.

L-1011 Autoflight: DUAL A/L NOT AVAIL LIGHT (22-15)

The DUAL A/L NOT AVAIL light (A/L .. Autoland), located on the Pilot's caution and warning panel, serves as a cruise monitor that forewarns of the unavailability of dual A/L whenever it detects a failure that may preclude achievement of dual A/L track status. Its activation is not dependent upon prior selection of A/L. Its purpose is to allow ample time to refile if the destination forecast would require dual A/L.

This warning can be reset and will remain out until the landing roll, when it will be recalled automatically as the airspeed passes through 90 knots. The recall serves as a reminder for postflight logbook entry and as an advisory message for maintenance personnel and for the next flight crew, if not corrected.

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: AFCS Mode Annunciators (22-11)

Verification of mode engagement is accomplished by observing the message on both AFCS MODES annunciators. An AFCS MODES annunciator is located on the top of each pilot's instrument panel.

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.