BOEING 707 circa 1970 - Inertial Navigation System

Introduction

The Inertial Navigation System in this panel is typical of the waypoint navigation systems in use in the 60s and 70s. The system can store up to 9 waypoints at any one time. It is similar in most respects to the CIVA INS unit, but has been slightly simplified for ease of use.

The Mode Selector Unit (MSU)

Introduction

Mode Selector Unit

The MSU, located on the overhead panel, has controls used to prepare the INS for use before take-off. This panel loads up with the INS ready to use if the saved flight has the engines running. Otherwise the INS will be switched off, and must be prepared before use while parked on the ground.

The Mode Selector Knob

When moving between OFF/STBY and ALIGN/NAV, or to/from ATT mode, the mouse button must be held down for about 2 seconds before the switch moves. This simulates pulling the knob above its mechanical stops.

The Ready Nav Light

When the Mode Selector is in ALIGN mode, the Ready Nav light illuminates when the gyroscopes are aligned and the unit is ready to be switched to NAV mode.

The Control and Display Unit (CDU)

Introduction

Inertial Navigation System

Most operations are carried out using the CDU (displayed above), which is located above the pedestal, and is accessed by clicking the pedestal button or by pressing pressing SHIFT + Keypad 5 (with NUM LOCK off).

Waypoint Switch

This switch, below the HOLD and REMOTE buttons, is used to select a waypoint to be edited in WPT mode.

From-To Display

This displays the numbers of the FROM and TO waypoints of the current leg (except in WPT mode, where the waypoint selected by the waypoint switch is displayed - flashing if it is part of the current leg). The WPT CHG button is used to change the current leg (for example to travel from waypoint 3 to waypoint 5, enter [WPT CHG][3][5][INSERT]).

Auto/Man Selector Switch

This switches between automatic and manual waypoint switching. The switch has a button on it which illuminates all lights on the CDU and MSU while pressed (for testing purposes) unless there is an error condition in the INS (see under WARN below for the button's operation in this case).

Buttons

CDU Data Selector

The CDU data selector knob selects the data displayed by the CDU:

Setting up the INS for use

If a flight is loaded with the aircraft parked and the engines stopped, the INS will be switched off. The following procedure should be followed to get the INS working.

WARNING: The aircraft must not be moved until the setup procedure is complete and the aircraft is in NAV mode. Otherwise, error 04-57 will be generated and the setup procedure must be restarted.

  1. Switch the MSU to STBY mode.
  2. Switch the CDU to POS mode, and enter your current latitude and longitude (For example, the co-ordinates N051°28'6 W000°29'3 would be entered using the keypresses [N][5][1][2][8][6][INSERT][W][2][9][3][INSERT] ). This may cause error condition 06-41. If the entered position is correct, this error can be cleared by pressing TEST twice.
  3. Switch the CDU to DSTRK/STS mode MSU to ALIGN mode. Alignment takes about half an hour. You may switch the CDU to WPT mode in order to enter waypoint data during this time (using the same format as for setting the initial position). Also a hidden switch at the top-right of the MSU permits alignment within a few seconds (though this is not realistic).
  4. Once the accuracy required performance index has decreased to 5 or less, the MSU green light will come on, indicating that the gyroscopes are now aligned. Switch the MSU to NAV mode.

Error Codes

The WARN light illuminates if an error is encountered. To view the error code move the CDU switch to DSTRK/STS. The first half of the error code is immediately visible in the second and third digits of the display, while pressing the TEST button (on the AUTO/MAN waypoint change switch) displays the second half of the error.

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