L-1011 Design Concept Notes - from Lockheed Flight Crew Study and Training Guide

General Design Concepts

In the subsequent sections concerning component design, some of the more notable improvements and design criteria will be discussed. Detailed system descriptions and their functions are functions are thorougly discussed in the flight operating manual and the L-1011 ground school.

Fuselage Design

The fuselage [of the L-1011] is of semi-monocoque shell construction, having a constant cross section diameter of 235 inches. for a major portion of its length. A typical barrel section was chosen which uses tapered frames and thick skins - without stringers - in the sidewalls of the main cabin area, rather than the more conventional constant section frames, skins, and stringers. This new design aprpaoch increased the usable cabin space, in addition to improving fatigue and corrosion resistance, by eliminating the need for many fasteners and faying surfaces. Trade-off studies made on other barrel designs also indicated that the selected design provided lower weight and was best suited to attenuate low-frequency noise, which resulted in reduced vibration. The L-1011 uses extensive structural adhesive bonding of doublers, triplers, and lapped skin panels into large panel assemblies up to 15 feet by 35 feet.

The L-1011 primary structure is designed to be fail safe. In general, the L-1011 design criteria is more stringent than FAA regulations require. A fail-safe structure is defined as one which is designed to preclude adverse effects on an aircraft's flight characteristics in the event of a failure or partial failure of any one structural member.

The curved windshield and cockpit enclosure has been designed to provide maximum visibility, with optimum instrument panel arrangement, and to reduce aerodynamic drag and flight station noise.

Wing Design

The wing design was optimized to provide minimum cost cruise speed at Mach 0.85. To optimize performance of both the high and low speed ends of the envelope, a combination of Supercritical and Conventional airfoil shapes were combined. The Supercritical airfoil was used inboard of the wing engines where the wing is thickest. As the wing tapers toward the tip, outbaord of the engines, several conventional airfoil sections were used. The purpose for all of this was to delay the effect of Mach Drag rise with the onset of shock wave formation. This allows the L-1011 to cruise at higher Mach numbers more efficiently than previous designs. To overcome the Supercritical airfoil's lower lift coefficient at slow speeds, the wing was twisted. That is, at any given fuselage angle of attack, the wing root has a higher angle of attack than the wing tip. The wing airfoil shape, taper, aspect ratio, and area were selected based on the results of an optimization analysis which considered the following operational and design constraints:

1. FAR takeoff field length less than 10,000 feet on 90ºF day at Sea Level and MTOW.
2. Initial cruise altitude of 31,000 feet minimum.
3. Approach speed at normal landing weight less than 140 knots.
   
4. Transcontinental range capability at 0.85 Mach number against winter winds (2650 nautical miles equivalent still air range).
5. Payload at design range of approximately 56,000 pounds.
   

Margins are provided between normal operating conditions and buffet boundary to allow for maneuvers or gust load factors of 2.5g maximum (flaps retracted). The wing geometry chosen provides full-span, leading edge devices and double-slotted, trailing-edge flaps. These design features, coupled with nominal wing area which is larger than that required for cruise conditions, resulted in a configuration that provides short filed capability, low approach and landing speed, and excellent cruise efficiency. The wing geometry and placement of the wing engines also provides the compatibility for incorporating the most efficient flap system. The large inboard flaps utilize the more efficient inboard portion of the wing for providing lift, where the wing chord is greatest and the flap pitching moment contributions are smallest. Furthermore, the engine pylons are far enough outboard to act as efficient fences in reducing the span-wise flow, thereby eliminating any pitch-up tendency.

L-1011 Door Controller

Since there really is no consumer grade software, like xPlane, that provides door management controls, I went ahead and wrote myself a little controller that allows me to set the door status on the L-1011 simulator. The controller also sets the shared memory region for the physical device controller that connects to the Annunciator Panel on the Second Officer Station.

The first image above shows the door controls for the passenger doors, the emergency exits and the cockpit hatch.

The second panel allows me to control the cargo doors and the service center doors.


The the third panel I have designed to control the gear doors and the warning indicators for the S-Duct.


The code is written Obj-C and also controls a number of xPlane data refs for gear retraction and pressurization.

Avionics Bending: Attitude Director Indicator - ADI (Analysis and Pinout)

First power up of the two pilot side instruments. Without the ARINC 429 data the flags will not clear, however, the measurements on the power supplies show that they are intact. I am really curious to see if the instruments will work after being on the line for over 6800 hours, having been parked in the Arizona desert for 10+ years and being rough handled during de-install ... we will see over the next few weeks. The next step here will be to write the ARINC bridge between xPlane and the avionics buses.

So, just like the HSI from yesterday's post, the SFENA (Thales Group) ADI is a truly awesome instrument and shows some very clever mechanical engineering. Both the N32 and the N33 are very much a complete computer in a box that does both the ARINC 429 handling as well as all of the servo channel handling.

The main subsystems of the ADI are:

1. Input Processor
2. Central Processing Unit
3. A/D Converter
4. Attitude Servo Channels
5. Pointer and Command Bar Servomechanism
6. Failure Warning Indicators
7. Output Processor
8. Power Supply / Lighting

The ADI actually ingests fewer ARING 429 labels than the HSI does. The N33 HSI receives data on 8 ARINC buses, while the N32 ADI only receives data on 5 of the ARINC avionics buses. Here is a list of the buses and the respective ARINC lablels:

Bus 1 - FAST/SLOW (Label 142)
Bus 2 - Not used
Bus 3 - Localizer (Label 173), Glideslope (Label 174)
Bus 4 - Reciprocal ADI - Sin/Cos Recopy (Label 325), Sin/Cos Recopy (Label 324)
Bus 5 - Roll Angle (Label 325) and Pitch Angel (Label 324)
Bus 6 - Flight Director Commands - Roll Command (Label 141), Pitch Command (Label 140) and Yaw Command (Label 143)

All of the buses above run either at 12 Kb/s or 100 Kb/s ... Bus1 and Bus4 are 100 Kb/s buses.

Here is the pin-out for the SFENA N32 ADI J1 connector:

q	Remote Test	Switch Input
A	115V 400 Hz	Power
B	115V 400 Hz	Power
P	BUS 1	ARINC 429
R	BUS 1	ARINC 429
y	BUS 3	ARINC 429
w	BUS 3	ARINC 429
a	BUS 4	ARINC 429
b	BUS 4	ARINC 429
T	BUS 5 Primary	ARINC 429
U	BUS 5 Primary	ARINC 429
X	BUS 5 Alternate	ARINC 429
Y	BUS 5 Alternate	ARINC 429
V	Bus 5 Alternate and Primary Switch	Switch Input
K	BUS 6 - Flight Director Channel 1	ARINC 429
L	BUS 6 - Flight Director Channel 1	ARINC 429
G	BUS 6 - Flight Director Channel 2	ARINC 429
H	BUS 6 - Flight Director Channel 2	ARINC 429
FF	Pin Program CPT/FO	Logic
M	FD/A Flag	Logic
HH	F/S Flag	Logic
AA	G/S Flag	Logic
GG	LOC Flag	Logic
EE	FD Flag	Logic
z	Monitor Bus - Reciproacl ADI	ARINC 429
y	Monitor Bus - Reciproacl ADI	ARINC 429
e	Decision Height Warning Light
f	Decision Height Warning Light
D	Integral Ligthing	5V
E	Integral Ligthing	5V
g	Validity Output Glideslope
h	Validity Output Flight Director
m	Validity Output Fast/Slow

To see the ADI in check this blog posting: SFENA ADI Working with XPlane

Avionics Bending: Horizontal Situation Indicator - HSI (Analysis and Pinout)

Thanks to some very kind people at Thales (the company that acquired Sextant which acquired SFENA a long time ago) I have been able to do a lot more research around the SFENA ADIs and HSIs that I intend on using for the project.

The instruments I have are from the early 1980s. The design of the ADI and HSI is truly amazing and shows just how much attention to detail and quality went into the engineering of them. The ADI and the HSI are based on ARINC 429 which is by far the most common avionics bus standard in use today (however, it is slowly being replaced by more modern standards).

Both the SFENA N33 (HSI) and N32 (ADI) instruments are based on a rather simple 8bit microprocessor made by RCA … namely the 1802RCA. The instruments are actually somewhat multi-processor systems because they are split into an input processors, handling the ARINC 429 communications, and a central processor handling all of the data transformations and the servo motor control. In order to reduce space needed by the electronics and to reduce the need for expensive resources, many of the functions in the instruments are multiplexed and use the same subsystems.

Specifically on the HSI, there are a number of subsystems that make up the entire electronics complex:

1. Input Processors

2. Central Processing Unit

3. A/D Converter

4. Servo Channels and Controller

5. Pointer Servomechanism Channels

6. Flags and Annunciator Subsystem

7. Magnetic Wheel Drivers

8. Data Output Processor

9. Power Supply and Lighting

The data used by the HSI would have been produced by a number of systems on-board and delivered to the instrument of several ARINC 429 buses. To be exact, the instrument receives data from a total of 8 data buses.

Bus 1 – Primary Attitude and Heading Reference System (AHRS)

Bus 2 – Automatic Flight Control System (AFCS)

Bus 3 – Instrument Landing System (ILS)

Bus 4 – ADF 1

Bus 5 – Flight Management Computer or GPS

Bus 6 – ADF 2

Bus 7 – Reciprocal HSI

Bus 8 – VOR

The above listed buses all feed a number of ARINC 429 labels to the HSI. Here is a list of labels on each of the buses:

Bus 1 – Magnetic Heading (Label 320), Drift (Label 321) and Ground Speed (Label 012)

Bus 2 – Heading Select (Label 101)

Bus 3 – Localizer (Label 173), Glide Slope (Label 174) and QFU (Label 105)

Bus 4 – ADF 1 (Label 162)

Bus 5 – True Heading (Label 314), Drift (Label 321), NAV Course (Label 114), Cross Track Distance (Label 116), NAV Vertical Deviation (Label 117), Ground Speed (Label 012), Distance-To-Go (Label 001), Alert (Label 270) and TO-FROM (also Label 270 but different bit)

Bus 6 – ADF 2 (Label 162)

Bus 7 – MAG (sin, cos recopy) (Label 320) and TRU (sin, cos recopy) (Label 314)

Most of the busses above run ARINC 429 Low Speed (12Kb/s) … however Bus 1 and Bus 7 require the faster 100 Kb/s ARINC 429 bus speed. Besides the ARINC 429 data,. The instrument also has a number of logic inputs that control the flags and other elements. The discrete inputs are:

· Normal / Alernate Switching for AHRS ….. 0V Normal, 28V Alternate

· True-Mag Selection …. 0V MAG, 28V TRUE

· HDG Select/Drift Selection … 0V HDG SEL, 28V DRIFT

· Sensor Number …. 0V … 1, 28V … 2

· Mode Selection … has two ports (pins) to encode the mode

• 0V 0V ….. VOR
• 28V 0V …. ILS
• 28V 28V …. NAV/FMC
• 0V 28V …. NAV/GPS

· HDG SEL / Drift Flag …. 0V Normal, 28V Pointer to 180 degree

· Vertical Deviation Flag …. 0V Normal, 28V Flag Retracted

· Selection of Bus for Drift Angle …. 0V AHRS/IRS, 28V FMC/OMEGA

· Selection of Bus giving Ground Speed …. 0V AHRS, 28V FMC/OMEGA

Here is the J1 connector pin-out for the SFENA N33 HSI:

Pin	SFENA Description	Notes
A	115V 400HZ	POWER INPUT
B	115V 400HZ	POWER INPUT
T	AHRS IRS Normal	ARINC 429 Input
U	AHRS IRS Normal	ARINC 429 Input
X	AHRS IRS Alternate	ARINC 429 Input
Y	AHRS IRS Alternate	ARINC 429 Input
a	Reciprocal HSI	ARINC 429 Input
b	Reciproacl HSI	ARINC 429 Input
M	ILS	ARINC 429 Input
N	ILS	ARINC 429 Input
J	VOR	ARINC 429 Input
K	VOR	ARINC 429 Input
L	ILS/VOR	Switch Input
P	AFCS Controller	ARINC 429 Input
R	AFCS Controller	ARINC 429 Input
DD	True/Magnetic Heading Switch	Switch Input
G	FMC or OMEGA	ARINC 429 Input
H	FMC or OMEGA	ARINC 429 Input
EE	NAV Source Switching	Switch Input
t	ADF 1	ARINC 429 Input
u	ADF 1	ARINC 429 Input
V	ADF 2	ARINC 429 Input
W	ADF 2	ARINC 429 Input
BB	Vertical Deviation	Logic Signal
AA	Heading Select	Logic Signal
FF	Sensor Identifier	Logic Signal
m	Ground Speed Source	Logic Signal
k	Drift Source	Logic Signal
CC	HDG SEL/DRIFT	Logic Signal
z	Reciproacl HSI	ARINC 429 Output
y	Reciproacl HSI	ARINC 429 Output
D	5V Integral Lighting	POWER INPUT
E	5V Integral Lighting	POWER INPUT
g	Validity Output
n	Validity Output
f	Validity Output
p	Comparison Warning Output