Razbam Simulations
6 h ·
Here are the INS alignment procedures available for the AV-8B NA. This is a draft document and some steps can be added/modified/deleted.
AV-8B N/A INS Alignment Procedures:
1. There are four alignment modes:
a. SEA
b. GND
c. IFA (GPS)
d. GYRO
2. There are three alignment sub-modes:
a. Stored Heading: Available for GND
b. Manual SEA align: Available for SEA
c. GPS airborne align: Available for IFA
3. The main alignment sequence is the same for all modes & sub-modes:
a. Cage (3 seconds): INS is aligned with aircraft fuselage.
b. Warm-Up (time depends on ambient temperature): Gyros and accelerometers are heated to its operational temperature (175ºF) at a rate of 2.5ºF per second.
c. Spin (13 seconds): Gyros are spun up to 22,500 rpm.
d. Level (9 seconds): INS platform is leveled with respect of local vertical.
e. Wide Angle Gyrocompass (time depends on alignment mode/sub-mode): INS determines True North.
f. Small Angle Alignment (time unknown): INS eliminate platform bias for maximum precision.
Total alignment time can be between 4 to12 minutes long.
How to do an INS alignment (all modes):
1. Make sure that the INS mode selector knob is in the OFF position.
2. Select EHSD on the MPCD (Left or Right).
3. Select DATA on the MPCD
4. Select AC on the MPCD.
a. Aircraft present position will be shown.
b. UFC/ODU will enter into Aircraft Position mode.
c. ODU options are:
i. Option 1: POS (Lat/Lon position coordinates).
ii. Option 2: MVAR (Local magnetic variation).
iii. Option 3: WIND (Wind Direction and speed).
iv. Option 4: BLANK
v. Option 5: BLANK
5. Enter AC present position (lat/lon).
6. Enter local magnetic variation (MVAR) if the value shown is 0
7. Place the INS mode selector knob in the selected alignment mode: SEA, GND, IFA or GYRO. The alignment process will start immediately IF THE REQUIRED INFORMATION IS PRESENT.
8. When alignment is finished, place the INS mode selector knob either in NAV or IFA (for GPS coupled navigation).
SEA Alignment:
SEA alignment can only be performed aboard a carrier.
SINS
The main SEA alignment mode is the Ship Inertial Navigation System (SINS) mode. In this mode, the aircraft connects to the ship’s INS and use it to achieve INS precision.
SINS and IFA are the only modes in which aircraft present position is not required to be entered by the pilot.
The aircraft connects itself to the ship’s INS via deck cable or by using either COM1 or COM2 radios. The ODU displays the following:
a. Option 1: DECK. A semicolon is shown if the deck cable is connected to the aircraft and it is being used for data transfer.
b. Option 2: COM1: A semicolon is show if the COM1 radio is used for data transfer. Selecting COM1 will display the SINS radio frequency in the UFC for confirmation or editing.
c. Option 3: COM2: A semicolon is show if the COM2 radio is used for data transfer. Selecting COM2 will display the SINS radio frequency in the UFC for confirmation or editing. This is the default selection when the deck cable is not connected.
d. Option 4: SEA: Unknown functionality.
MANUAL SEA ALIGNMENT
MANUAL SEA alignment is a sub-mode of the SEA alignment and used when SINS is not available. MANUAL and SINS are mutually exclusive. Selecting MANUAL will deselect and disable SINS. To return to SINS, the INS mode selector knob must be changed to another mode and then back to SEA.
In MANUAL SEA alignment the following data is required:
1. Aircraft present position.
2. Ship’s heading and speed.
3. Aircraft’s TRUE heading.
4. Local magnetic variation if it does not exist in the system.
To select MANUAL:
1. Click on the MAN option pushbutton in the EHSD page.
2. MAN option will be boxed
3. SINS option will be unboxed and removed from the screen.
4. The UFC/ODU will be placed in MANUAL SEA mode for data entry.
5. Input the required data so the process can start.
GND Alignment
GND (Ground) alignment is performed with the aircraft on land. If the parking brake is released, the alignment process enter into hold mode. If the aircraft moves too far from its present position the INS caution light will turn on indicating an invalid INS present position and entire process must be restarted.
STORED HEADING ALIGNMENT
The Stored Head alignment’s purpose is to reduce total align time by bypassing the Wide Angle Gyrocompass step.
This procedure can be performed when:
1. The aircraft is parked and parking brake is set.
2. A complete INS ground alignment has been previously performed.
3. The aircraft has not moved since the alignment.
4. NAV has not been selected in the INS mode selector knob.
Stored Heading alignment availability is indicated by the presence of the SHDG pushbutton on the upper left corner of the ground align display.
To select Stored Heading alignment, click on the SHDG pushbutton.
The SHDG pushbutton will be removed when the alignment process enters into Wide Angle Gyrocompass, at which point the stored heading will be deleted from the system.
In-Flight-Alignment (IFA)
IFA uses the GPS to continuously update the INS.
If IFA is selected without an aligned INS, the GPS data will be used to align the INS. This is the only mode that allows INS alignment while the aircraft is moving. Aircraft present position is not required to be entered by the pilot since it is provided by the GPS.
The alignment process will enter in hold mode when:
1. Aircraft roll exceeds 30 degrees, or
2. Aircraft pitch is greater than 15 or less than -5 degrees.
If the aircraft is moving, INS alignment can take as much as 10 minutes.
The INS will automatically enter into coupled navigation mode as soon as the IFA alignment process ends.
When the INS is in IFA mode, INS position update is not required.
GYRO Alignment.
This mode provides a quick 33 seconds alignment process. If used aboard a ship it can take 45 seconds.
Present position data is not available in GYRO.
GYRO mode is the least accurate navigation mode and full inertial navigation mode cannot be achieved in flight after using GYRO, even if the INS mode selector is changed to NAV. To obtain full inertial navigation an IFA alignment must be performed (10 minutes process).
GYRO mode is susceptible to precession errors and large errors (greater than 5 degrees) in both heading and attitude are possible.
ATTENTION
The alignment process will not start if the required information is not present:
1. Valid aircraft Present Position (Not required for SEA SINS and IFA).
2. Local magnetic variation (Not required for SEA SINS and IFA).
3. CV's heading and speed (SEA Manual mode only).
4. Aircraft True Heading (SEA Manual model only).
Taking off with the INS in the OFF position can result in unit damage due to acceleration forces.
INS alignment is under development/testing and will soon be available.
