L-1011 Navigation: Inertial Navigation System (34-43-6/7)

The INUs are located in the forward electronic service center against the forward bulkhead. The batteries are located in the left-hand equipment rack. These areas are all accessible while in flight.

The MSUs are located on the Pilot's Overhead Pane, and the CDUs are located on the center console. CDU No. 1 is forward of the throttles on the Captain's side; CDU No. 2 is on the First Officer's side forward of the throttles; and CDU No. 3 is center aft of the throttles. 

L-1011 Navigation: Inertial Navigation System (34-43-5)

The INS system hardware consists of for components:

• The Inertial Navigation Unit (INU), which contains the platform and computer. 
• The Control Display Unit (CDU), which is essentially a remote terminal by which the crew communicates with the computer. 
• The mode selector (MSU), is a function switch for the computer.
• The final item is a battery capable of powering the system for up to 15 minutes in case of loss of ship's power.

L-1011 Navigation: Inertial Navigation System (34-43-4)

Once alignment is complete and the aircraft starts moving, the computer converts acceleration signals to a series of vectors. By algebraically summing the vector, the computer measures distance traveled in north-south and east-west directions. The computer upgrades position extremely rapidly (in terms of microseconds) and is therefore capable of detaching very small variations in velocity.
In the short term, INS computers are very accurate. OVer the long term, however, the computer accumulates computations errors. The magnitude of these errors becomes progressively greater with time. When two or more INSs are operations, the crew can observe the present positions slowly drift apart. Since the computers do drift, there is a built-in compensation circuit. When the INS is shutdown, the position is recorded. When the set is next aligned, the difference between shutdown position and alignment position is measured and an appropriate correction favor is then applied to further computations. 

L-1011 Navigation: Inertial Navigation System (INS) (34-43-3)

Before the INS can begin operation, the platform must be aligned to true north. When power is applied and the gyros come up to speed, the playroom is erected just as a conventional attitude gyre is erected. Once the platform is erect, the accelerometers sense the earth's rotation. The computer determines the direction of motion caused by the earth's rotation relative to the platform axis. In doing so, the computer determines the orientation oft he platform to true north. It is useful to remember that all computer computations are in reference to true north.

After orientation to true north, the computer measures the rate of earth rotation. By comparing the measured earth rate to earth rate data stored in the computer's memory, the computer can determine its latitude. However, the INS cannot determine its longitude. Before navigation can commence, the crew must insert the coordinates at which the platform is erected into the computer's memory.  

L-1011 Navigation: Inertial Navigation System (34-43)

The next few postings will cover an interesting system of the L-1011 which is the Delco Carousel Inertial Navigation System. This system was not only used on the L-1011, however, most long range 1011s ended up equipped with the Delco Carousel system. The Delos Carousel system also has a really neat old computer interface. 

In general, however, Inertial Navigation Systems (INS) are a spin off of the ballistic missile. They are highly compact, accurate, reliable and virtually automatic. The heart of the system is a cluster of accelerometers mounted on a gyro-stabilized platform. Acceleration signals are fed to a specialized computer that converts the signals to vectors in both north-south and east-west directions.

L-1011 Navigation: Radar Control Panel (34-19.20.21)

The switches across the top of the radar control panel have the following functions:

• OFF - both radar systems are off. 
• STBY - the selected RT entered a three minute warmup period. 
• NORM - narrow beam scan for selected radar. The other radar is off. If NORM is selected immediately, the card will still go through its three minute warmup operation. 
• CONT - [Contrast] blanks out returns of maximum intensity weather. 
• MAP - provides expanded beam for ground mapping.
• TEST - projects a test pattern on scopes and illuminates all the control lights. The selected system also starts the warmup period. 

The antenna is capable of stabilizing with the aircraft attitude of 25º roll and 15º pitch. Manual pitch tilting is permitted with the UP/DN pitch control knob on the right hand side of the panel.

The variable gain control switch on the left hand side of the panel allows amplification (gain up) of the radar return signal on the scopes. When in the AUTO position, the gain is automatically controlled.

L-1011 Navigation: Radar Control Head (34-17)

The radar control head is located on the aft center console. The radar scoops are mounted on the opposite ends of the Capt. and F/O's instrument panels.

A selector is provided to select either the No.1 or No.2 radar system. With the No.1 selected the No.1 REC/TRANS and No.1 VG/INS are being used to align the antenna and produce the radar scope images.  With the No.2 selected, the No.2 REC/TRANS and No.2 VG/INS are being used. Again, both scope would now show radar images from the No.2 system. On the L-1011 it is not possible to operate the two radar scopes on opposite systems.

The VG/INS provides stabilization to the radar antenna.

L-1011 Navigation: Transponder (34-15)

In the Lockheed L-1011 cockpit the transponder is located on the center console. A three-position transponder select switch is provider in most cases:

• #1, #1 transponder is being used, #2 Standby 
• Standby, both transponders are warmed up (as long as power on aircraft) but neither is operating. 
• #2, #3 transponder is being used, #1 in Standby 

The mode select switch determines  whether A domestic or B international coding is being used. (More modern devices include other modes as well as TCAS).

A three-position altitude reporting switch is provided:

• #1, ADC #1 is being used for altitude reporting 
• OFF ... the system is off 
• #2, ADC #2 is being used for altitude reporting 

The fault light indicates a fault within the selected system (amber). This should prompt the pilots to select the other transponder. The IDENT button provides an additional pulse reply. IDENT pulse lasts for 20 seconds after IDENT button is release.

Pushing the test button also illuminates the REPLY light. 

L-1011 Navigation: 12 Hour Clock (34-14)

There are two 12-hour electric clocks, one on the Captains instrument panel and one on the first officers' instrument panel. On some Lockheed L-1011's a digital type clock was installed in place of the 12 hour clocks. In most cases the clock installed on the flight engineer station was either a digital style clock or a 24h clock. The clock is set normally with the SET or GMT knob. The SWP knob on the 12h clock has the following functions:

• Press first time up to 12 minutes of sweep
• Press second time to reset the sweep time

L-1011 Navigation: Marker Beacon Lights (34-13)

Marker Beacon Lights are tested by pushing each light individually. The light s are labeled and color coded for the Outer, Middle and Airways marker.

Holding the TEST switch on the associated radio head will sequentially test the marker beacon lights. AIRWAYS comes on then goes out, then MIDDLE comes on then goes out and lastly OUTER comes on then goes out. As each light ones on, it's associated identification tone is also heard. 

L-1011 Navigation: ADF (34-12)

The dual ADF panel is located on the center console. Besides the triple frequency selector there are switches for BFO (Beat Frequency Oscillator) and a selector switch for ANT - OFF - ADF. 

L-1011 Navigation: RDDMI (34-7)

A DME failure will cause a fail flag to appear in the DME window (arrow 1). A VHF failure will cause the appropriate VOR1 or VOR2 fail flag to appear (arrow 2). 

L-1011 Navigation: RDDMI (34-6)

The RDDMI's are located on the Captain and F/O's instrument panels. They display the following NAV data:

• NAV 1 DME
• NAV 2 DME
• And a combination of VOR and ADF directional information, depending on pilot selection.

The VOR and ADF source selection is made with the black switches on the bottom left and bottom right of the instrument. A flag right above the switch shows which NAV source is being displayed by which needle. 

L-1011 Navigation: HSI Fail Flags (34-4)

A VOR or localizer failure or power failure will cause the NAV fail flags to come into view, depending on frequency selection.

A glideslope or V/NAV failure will cause the glideslope flag to appear. 

L-1011 Navigation: HSI Location (34-3)

The primary navigation display in the L-1011 cockpit is the Horizontal Situation Indicator (HSI). Here are the basic function elements of the HSI:

• The deviation bar works the same as on other HSI's or CDI's
• The type of radios at a is displayed in the small windows (NAV data source indicators) which are VOR 1, VOR 2, ILS 1 and ILS 2
• The cursor arrow is controlled by the two course knobs on the autopilot NAV MODE panel. 
• Triangular VOR indications are provided when the HSI is in VOR mode. 
• Glideslope display is provided when turned to an ILS. While using VOR, the glideslope display is shuttered. 
• The ALERT 1 Minute from R-NAV Waypoint is also used in conjunction with the INS and NAV equipment.

L-1011 Navigation: VHF NAF (34-1/2)

The Lockheed L-1011 as two in depended VHF NAV systems. The control heads are not located as part of the center console, but are part of the glare shield (see image above). A four-position DME control switch is also provided (outlined). The DME control switch has the following functions:

1. STBY - permits audio reception but no search display 
2. NORM - permits reception of up to 200 NM 
3. OVRD - permits reception of up to 400 NM
4. TEST - provides the following interactions on the RDDMI within a 9 second period after pushing the spring loaded switch to TEST: a) DME fail flag, b) Four dashes followed by c) Four zeros 

L-1011 Landing Gear and Brakes: Nose Wheel Steering (32-27/28)

The nose wheel steering control wheel is located on the Captain's and First Officer's side console.

Rudder pedal steering is only available when the nose landing gear strut is compressed. If rudder input is being used at that time, the nose wheel will automatically go to the rudder position. The amount of nose wheel steering applied will be proportional tot he amount of rudder applied. The rudder pedal can be used up to plus or minus 12º of steering.

Control wheel steering is active anytime down hydraulic pressure is available to the nose landing gear. It has priority over rudder pedal steering and will override at any time. Control wheel steering will turn the nose gear plus or minus 64º. 

L-1011 Landing Gear and Brakes: Brake Temperature Panel (32-25)

The brake temperature panel is located in the upper right hand corner of the Flight Engineer's panel. There is also a brake temperature light on the pilots' caution and warning panel on the center instrument panel. This panel can monitor all eight brakes and show the respective brake temperature on a vertical temperature gauge. 

L-1011 Landing Gear and Brake: Automatic Braking Control Panel (32-23)

The Automatic Braking System (ABS) automatically applies the aircraft brakes promptly and smoothly on landing or a rejected takeoff. Using this system lessens tire and brake wear, enhances passenger comfort and reduces Pilot workload.

The autobraking panel is located on the Pilot's overhead panel and contains a momentary on switch light with the split legends ARMED and FAIL and a six position rotary mode selector. The six positions are INOP, OFF, MIN, MED, MAX and TAKEOFF. There are four preselected deceleration rates that can be used with he ABS system. They are:

MODE      PSI/SEC RAMP RATE     DECEL RATE
MIN          650                4.0 FT/SEC/SEC
MED          650                6.0 FT/SEC/SEC
MAX        1,300                MAX (3000 PSI)
TAKEOFF   15,000                MAX (3000 PSI)

Brake pressure is automatically controlled to compensate for use of spoilers, reverse thrust and other decelerating forces to maintain a constant deceleration. 

L-1011 Flight Controls and Brakes: Anti-Skid System (32-22)

The anti-skid panel is located in the Pilot's overhead panel. Anti-skid is available with both the normal and alternate brake system. Which brake system the anti-skid is working with is determined by the position of the brake select switch. Located on the Pilot's caution and warning panel is an anti-skid light which will illuminate under following conditions:

1. If the Gear is down and the anti-skid is off
2. If the anti-skid is on and the parking brakes are set

L-1011 Landing Gear and Brake: Parking Brake Handle (32-21)

The parking brake pull knob is located on the center console just below the gear horn cutout switch. To set the parking brakes, apply brake pressure with the toe brakes, pull the parking brake knob and release the toe brakes. A red light next to the parking brake knob for the Captain, and a red light only at the First Officer's position will illuminate indicating the parking brakes are set and pressure is present at the brakes. 

L-1011 Landing Gear and Brakes: Brakes System Indicators (32-20)

Located below the gear switch and position lights is the brake pressure gauge which reads "B" or "C" system accumulator pressure. Below the brake pressure gauge is the brake select switch. This switch selects which hydraulic system will be used for braking. "B" system is used for alternate. "B" and "C" system brake accumulator low pressure lights are located on the Flight Engineer's annunciator panel. The Pilot's caution and warning panel will display a LOW BRAKE PRESSURE light should either accumulator light be illuminated. 

L-1011 Landing Gear and Brakes: Mechanical Brakes (32-19)

The Lockheed L-1011 uses hydraulically actuated multiple disk type brakes. The brakes are self-adjusting and incorporate direct mechanical wear indicators at the disk.

The brake system uses a dual cable run from the brake pedals back to the dual brake valve located in the hydraulic service center. The Captain's cable run controls system "B" dual brake valve and the First Officer's control system "C". Both dual brake valves are mechanically linked together. Either operator exercises both brake valves simultaneously. A bunge system is incorporated outboard of each brake valve to protect against possible jams. 

L-1011 Landing Gear and Brakes: NLG Visual Downlock (32-14)

Located on the jury brace assembly of then nose gear attached two red rods which align themselves when the jury brace goes over center. On the aft wall of the forward electronic service center is located a viewer. Access to the forward electronic service center for visual inspection of the alignment rods is possible from the flight station. 

L-1011 Landing Gear and Brakes: MLG Visual Downlock

The L-1011 has a rather interesting way of indicating main landing gear down lock. Located on the top of each wing directly over the main gear is a circular pop-up indicator. When the main gear is down and locked, a mechanical linkage pops up this indicator about 1/2" oboe the wing surface. The linkage is driven by the jury brace actuator rod end. 

L-1011 Landing Gear and Brakes: MLG and NLG Up-lock (32-11/12)

With the landing ear in the retracted position, the main landing gear is healed by resting on the triangular door beam, not the actual door.  The gear door lock and the gear up-lock are one and the same. With the gear switch placed in the neutral position, all hydraulic power is removed from the gear and it rides between two shock absorbing snubbers. 

The nose landing gear is held in the retracted position mechanically by the up-lock device on the aft wall of the nose gear wheel well. The two pairs of doors are mechanically sequenced closed by the retracting action of the gear. 

L-1011 Landing Gear and Brakes: Gear or Door Lights (32-10)

There are three GEAR or DOOR lights located on the second officers panel which are used to determine which gear or door is causing a problem.

With the gear down and locked as indicated by the three green lights and the DOOR and IN TRANS lights on, the GAR or DOOR lights on the Send Officer's panel indicates the problem is with the left and right main dear doors. 

L-1011 Landing Gear and Brakes: Gear Switch and Position Lights (32-6)

The Gear Switch and position lights are located on the Pilot's center instrument panel. The three green lights on top are the congenital down and locked indication. The red IN TRANS light is a total disagreement light concerning everything in the gear system. The red DOOR light is a disagreement light dealing only with the doors. The amber TRUCK light illuminates anytime the truck is not level +/- 2 1/2º degrees of tilt. All of these position lights receive their information from the proximity system. The gear switch is a three-position switch which incorporates a down lock release button. 

L-1011 Landing Gear and Brakes: Overview (32-1/2/3)

The Lockheed L-1011 aircraft landing gear uses a tricycle type configuration and is of conventional design and construction. It is electrically controlled and hydraulically operated using "C" system hydraulic pressure.

Because of the four wheel bogie, dual tandem arrangement, the pavement stress is less than most other jet transport type aircraft. As you can see, the gear is quite large (see below) when compared to an average height person. The inboard Main Landing Gear Doors also use "C" system hydraulic pressure.

L-1011 Flight Instruments: Instrument Difference Warnings (Comparator) (31-33/37)

The instrument comparator monitors for instrument differences. If an instrument difference occurs, the appropriate warning flag will appear in the Captain and F/O's instrument comparator panel. 

A difference of 6 knots to 10 knots between the IAS indicators will cause the AIRSPEED instrument comparator flag to appear. An IAS fail flag might also appear in the IAS indicator, but not necessarily. The higher the indicated speed, the grater the error must be to get a comparison flag. At 200 knots, a 6 knot difference will trip the comparator. A 10 knot difference required at 450 knots. 

After an initial VG/ISS failure, a difference in attitude indications exceeding 5º will cause an ATTITUDE comparison flag to appear on both instrument comparator panels.  an ATT flag may appear on the ADI, but not necessarily. 

A difference of altitude indications of between 100 and 240 feet will cause the ALTITUDE comparison flags to appear. 

• The difference required to get a warning increases with altitude. Approximately 100 feet at sea level will increase to 240 feet at 40,000 feet. 

The Instrument Comparator threshold is doubled if the vertical speed exceeds 800 FPM. 

A difference of heading indications of between 6º and 15º will cause the HEADING comparison flags to appear. The difference required for the HEADING flag increases as the angle of bank increases. A HDG flag in the HSI could also be present, but not necessarily. 

L-1011 Flight Instruments: Heading Failures (31-32)

Any heading system failure will cause the heading Flag to appear on both the RDDMI as well as the HSI.  Here is how a heading failure would manifest itself:

The associated RDDMI compass card would have a heading flag and the card would freeze in place with the data from the last good heading. However, the VOR/ADF needles will show the relative bearing.

Heading flags will also be in view while slewing the compasses with the COMPASS panel controls.

The HSI compass cards also provide inputs to the instrument comparator system and any difference between the two cards will trigger the comparator error to be shown. If a difference of between 6º in level flight, and 15º in a 30º bank occurs between the two HSI's, a HEADING warning flag will appear on both comparator panels. 

L-1011 Dimensions (Part 4)

In this posting I am showing you the basic differences between the -1 and the -500 model aircraft. The second image is an interesting detail drawing of the gear door. The images are taken from an engineering publication released by Lockheed-California in the 1980s.

L-1011 Flight Instruments: Compass Control Panel (31-29)

When DG is elected on the COMPASS panel the following happens:

• DG is free of MAG inputs
• The directional gyro may be slewed to any position at two different speeds. 
• In this case, the SYNC operator does not work because the are not magnetic indicators to synchronize

When MAG is re-selected, the DG will align to magnetic north as received from the MAG Flux at a rapid rate. 

When operating in the DG mode, there is no indication of DG mode operation except for the DG light on the compass control panel. 

L-1011 Dimensions (Part 3)

The first two images show the L-1011-1 split into Fuselage Sections. Typically Fuselage Sections are measured in inches from the datum line. Click on the image to enlarge to see the full details.

The last image of this positing shows the door and landing gear dimensions for the L-1011-1.

L-1011 Flight Instruments: Standby Horizon (31-25)

The standby horizon is a completely self-contained unit and is located on the Pilot's center instrument panel. It is powered from the AC standby bus. The cage know may be used to erect the horizon. Flags on the instrument show when the gyro is caged or when power to the device is lost (depending on make or model of the standby horizon). Most standby horizons deployed on the L-1011 had been made by SFENA. 

L-1011 Flight Instruments: Heading Reference System (31-27/28)

The primary displays for the heading reference system are the Captain and F/O's HSI and RDDMI compass cards. 

Two compass control panels are located on the pilot's overhead. A selector switch for MAG or DG is provided. When MAG is selected the MAG light on the switch is on in this case:

• Gyro reference switches to Magnetic north.
• May be slewed but will realign to MAG north. 
• Sync indicator shows difference between indicated heading and MAG heading 

The DG's automatically align to MAG north at a rapid rate when electrical power is applied.

L-1011 Flight Instruments: ADI Failures (31-21)

The Captain's ADI on the L1011 has inputs from INS 1 and Vertical Gyro #3. The F/O's ADI has inputs from INS 2 and VG #3. The inputs are compared in the ADI instrument itself and outputs are then sent to the instrument comparator monitor which signals the appropriate attitude flag or the ATT 3 annunciator light on the center panel annunciator cluster.

Once a failure has been sensed, the remaining VG/INS's are monitored for validity only. Because there are only two remaining VG/INS's the comparator system can only warn of a difference between them. This is done by presenting an an attitude flag on both instrument comparators.

L-1011 Flight Instruments: Attitude Indicator Failures (31-19)

• The Attitude Flag appears with first INS failure or instrument failure. 
• The Speed Flag appears if there is a power failure. The speed command pointer will bias out of view with an invalid signal. 
• The expanded localizer deviation indicator is covered. The shutter appears if a localizer frequency is tuned and there is an invalid input or there is a power supply failure. Also when a VOR frequency is tuned. 
• Flight Director flags come into view with signal loss from APFDS computers, power failure or incompatible frequencies. 
• The Glideslope Flag shows when power is lost or the GS signal is too far out or out of range.