HUD
HEAD-UP DISPLAY
The HUD consists of computerized flight, targeting and weapons information projected on an eye-level sheet of specially coated glass at the front of the cockpit. It's designed to keep the pilot from having to constantly look at his instruments (hence the name "Head-Up) for flight and combat information. it is good thing to have when locked in a wild dogfight.
Basic HUD Symbology
The basic HUD symbology is common to all three master Modes.
Heading Scale: Displays your current heading. The heading Scale is basically a digital compass laid out on horizontal tape. North is 000, East is 090, South is 180 and West is 270 degrees. The heading numbers are displayed every 10 degrees over large tick mark. a A total of 30 degrees is displayed a one time on the moving tape.
Airspeed: Displays your current indicated airspeed in knots (kts)
Angle of Attack: Displays your current AoA in degrees.
Mach Number: Displays your current mach number.
Aircraft G: Displays the number of Gs you're current pulling.
Peak Aircraft G: Displays the maximum attainable G the aircraft is allowed to generate based on correct weight and the G-override limiter.
Flaps Mode: The current Flap mode (Auto, Full, or Half) is displayed here.
Pitch Ladder: The Pitch Ladder lines are drawn every five degrees and angle in towards the horizon at an angle half that of the flight path angle. For example, in a 40° climb, the pitch lines arc angled 20° toward the horizon. Positive pitch lines arc solid, and negative pitch lines are dashed. Each line is numbered, and numbers rotate whit roll that inverted Flight is easy recognized.
Velocity Vector: The velocity vector (also called the flight path indicator) points to the actual direction the aircraft is flying. For example, with heavy rudder use, the nose of the aircraft may point in one direction while the aircraft side-slips In another direction. The velocity vector is limited to an 8° radius circle, so if it reaches this limit during flight it flashes rapidly denoting it is no longer accurately indicating the flight path.
Selected Waypoint: Displays the currently selected waypoint.
Distance to Waypoint: Displays the current distance, in nautical miles, to the currently selected waypoint.
Altitude: Displays either the barometric or radar altitude depending on the setting of the ALT switch on the HUD control panel. When the switch is in the BARO position, barometric altitude displays; in the RDR position, radar altitude displays and is indicated by an R next to the altitude. RDR is only valid at or below 5,000 feet AGL. If the radar altitude is or becomes invalid when selected For display, barometric altitude displays and a "B" flashes next to the altitude indicated that barometric, altitude is displaying rather than radar altitude.
The current Vertical Velocity, in feel per minute, displays above the altitude box only in NAV Master Mode. Negative values indicate descent.
Heading Bug: The heading bug indicates the bearing to the currently selected waypoint, target, or TACAN station, depending upon which steering mode is selected on the HSI.
Landing HUD Symbology
With the NAV Master Mode set and the landing gear down, the HUD displays the landing information. The Mach Number, Aircraft Gs and Peak Gs are deleted. The steering information can display on the basic or landing HUD formats. The current steering mode is selected on the HSI page.
Horizon Bar: Extends across the HUD.
Angle-of-Attack (AOA) Bracket: The AOA Bracket displays adjacent to the left of the Velocity Vector. Its in addition to the normal digital AOA. The center of the bracket represents the optimum approach angle-of-attack (8.1° true). The length of the bracket is about ± 1.2°. The bracket moves lower than the Velocity Vector as AOA increases and higher as AOA decreases.
Bank Angle Scale: Indicates your current bank angle in degrees from the horizontal.
ILS Glideslope Bar: It's a "Fly-to" symbol linked to the Velocity Vector that displays aircraft position above, on or below the Glideslope when landing. The ILS Glideslope bar is displayed when the ILS is turned on.
Distance to Carrier: When ACL s steering is selected, the distance to your home aircraft carrier in nautical miles is displayed here.
Steering Mode: The current steering mode selected on the HSI is displayed here.
Autopilot Mode: If the autopilot is engaged, the current autopilot mode selected on the UFC is displayed here.
HUD Data Link & Advisory Massages: HUD date link advisory messages can appear on the HUD when ACL steering is selected in NAV master mode. These messages are:
NOT CMD: Indicates you're not within in the ACL control area or your aircraft is not capable of ACL landings (probably as a result of battle damage).
LND CHK: Indicates you're within the ACL control area but not configured For landing(gear and hook down).
ACL RDY: Indicates you're within the ACL control box, configured for landing, and ready to be coupled (via the autopilot).
CMD CONT: Indicates the ACL system is in control of your aircraft.
W/O: Indicates you're to terminate the approach and go around. When this message is received, the ACL system uncouples from the autopilot, and control of the aircraft reverts back to you.
ILS Localiser Bar: It's a "fly-to" symbol linked to the Velocity Vector that displays aircraft position left of center, on centerline or right of center when landing. The ILS localiser bar is only displayed when the ILS is turned on.
WaterIine Symbol: The aircraft WaterIine position is indicated on the HUD (4° above the optical center) by displaying the flying W symbol. The waterline symbol is displayed when the landing gear is down.
Basic Air to Air HUD Symbology
The A/A HUD has it's own weapon independed symbology that is described here. This section is not intended to show all of the A/A HUD symbology rather, it is meant to give you a basic idea of what to expect in A/A Master Mode, In addition to this common A/A HUD symbology, radar target acquisition and weapon specific symbology can be displayed on the HUD. Weapons independent symbology is symbology that is common to all A/A missiles. The A/A HUD gun modes also use some of this symbology.
SHOOT Cue: Displays above the target designator (TD) box when all shoot conditions for the selected weapon are met. The shoot cue flashes when the target is within "no escape" range and weapon intercept is optimal.
Target Designator Box: The target designator (TD) box is a square that identifies the line of sight (LOS) to the Launch & Steering (L&S) target. The TD box flashes when the L&S target outside the HUD FOV. Targets identified as friendly will have an X through the center of the box.
Secondary Target Line-of-Sight Cue: In the Track-While-Scan radar mode, it is possible to track both a primary and secondary target at the same time. If a secondary (also known as a DT2 target) exists, a small X is displayed to represent the DT2 target LOS.
Normalised In-Range Display (NIRD) / Allowable Steering Error (ASE) circle: The NIRD/ASE circle consists of a 6° diameter circle centered at the aircraft waterline. The individual elements of the NIRD circle are described separately below. The NIRD circle will not appear unless there Is a L&S target.
Weapon Selected and Quantity Remaining: Indicates the currently selected weapon, followed by the number of the selected weapon remaining. When the gun is the selected weapon, the number of gun rounds remaining is displayed underneath the "GUN"' text. An X through the selected weapon indicates that Master Arm is set to SAFE.
Target Range: Target range displays whenever there is an L&S target. The target range is displayed to the nearest tenth of a nautical mile.
Target Range Rate: Target range rate (VC) in knots displays whenever there is an L&S target. A closing velocity (target getting closer to you) is in positive number and an opening velocity (target getting further- away from you) is a negative number.
Steering Dot: A steering dot displays whenever an A/A missile is selected, an L&S target is designated and is it located within 76° of aircraft boresight. The steering dot in conjunction with the NIRD circle, provides lead angle steering. Flying the aircraft so that the steering dot is inside the NIRD circle satisfies the lead angle computation. The steering dot flashes when the target is within 15° of the A/A radar azimuth limit of ±70° or within 5° of the elevation limit of ± 60°. When AIM-9 is selected and the AIM-9 is tracking a target other than the L&S, the steering dot is removed.
Relative Range Bar: The relative range of the target is displayed by the bar just inside the NIRD circle. It starts at the 12 o'clock position and rotates clockwise as target range increases. It's scaled relative to RAREO and RMIN.
Maximum Aerodynamic Rang a (RAERO): RAERO is the absolute maximum straight-line range of the missile. Hitting the target at this range is only possible if the target files completely straight and level during the entire time of flight of the missile.
Maximum Launch Range (RMAX): RMAX is the maximum range of the missile against a target that flies straight and level during most of the missiles time of flight, and then performs a terminal escape maneuver Just before the missile reaches it.
No Escape Range (RNE): The estimated no-escape range represents the optimal firing range against a. maneuvering target. You are much more likely to get a hit if you wait until the target is within this range.
Minimum Launch Range (RMIN): The minimum launch range for the missile; a missile fired within this range will probably not hit the target. Once the target is within RMIN a large flashing Breakaway X will appear on the HUD (and on the radar MDI).
Gun Maximum Range: When the radar is in STT, the gun RMAX tab displays on the NIRD circle to indicate the maximum effective range of the gun. The gun RMAX marker only displays when in STT, an A/A missile is selected, and target range is less than 12,000 ft,
Basic Air to Ground HUD Symbology
When the A/G Master Mode is selected, target location and weapon release cues are added to the HUD. Much of this symbology is common to all A/G weapons and is described here. Again this section is not intended to show all of the A/G HUD symbology; rather, it is meant to give you a basic of what to expect in A/G Master mode. Along whit this common A/G HUD symbology, additional weapons specific symbology can display on the HUD.

Release Cue: The release cue is a small line perpendicular to and centered on the Azimuth Steering Line (ASL). It displays when a target is designated in the AUTO bomb mode. Initially, the release cue appears on the ASL above the velocity vector. As the weapon release point is approached, the release cue moves with the ASL. When the release cue intersects the velocity vector, which is positioned on the ASL through aircraft steering maneuvers, and the pickle button is depressed, automatic weapon release is initiated. If steering error exceeds 20°, the release cue is blanked and release is inhibited in the AUTO mode.
Azimuth Steering Line (ASL): The ASL provides a steering cue to the designated target. The ASL displays after target designation in the AUTO mode. The ASL always displays perpendicular to the horizon and provides an azimuth steering reference with respect to the velocity vector.
Target Designator (TD) Diamond: The TD diamond is used to identify target line of sight in all A/G weapon delivery modes. It contains a piper in its center as an aiming reference whenever the TDC is assigned. The TD diamond is used in conjunction with the TDC to designate targets and is movable over the total HUD field of view. After designation, this symbol displays the computed position of the A/G designated target. The initial HUD TD designation is performed by assigning the TDC to the HUD, moving the TDC to the desired position on the HUD, and selecting the designate key function.
If the computed line of sight to the designated target lies outside the HUD field of view, the TD diamond is limited on the HUD along the edge to the designated target and flashes indicating the limit condition. The TD diamond is blanked when the bearing to the designated target exceeds 90°.
Range to Target: When there is an Air-to-Ground designated target and TGT steering is selected, the range-to the target is displayed here.
Frag Cue: The frag cue represents the edge of the predicted fragmentation envelope for the selected weapon. To avoid the fragmentation envelope (and the possibility of severe aircraft damage), make sure this line is below the velocity vector when the weapon detonates. During low altitude weapon deliveries, you may be below the frag cue when you release your weapons. In this Case, make sure you are flying very fast (above 600 knots is a good) or get above that altitude before the weapon goes off.
Release Time-To-Go (REL): When a target is designated in AUTO mode this two- digit readout indicates the number of seconds remaining until weapon release occurs (## REL). REL is blanked when the steering error exceeds 20° in AUTO mode. For guided weapons such as Walleye and Maverick, the Time To Maximum Range (##TTMK.) Is displayed instead of TTG.
If the computed TTMR exceeds 99 seconds, the display is limeted until the TTMR becomes less than this value.
In the A/G gun and rocket modes, the number of rounds remaining displays in this location rather than the TTG or TTMR (GUN ### or RKT ###).
Mode / Weapon Indication: When any weapon except Walleye, Maverick, Harpoon, HARM, SLAM, JSOW, or JDAM is selected, the selected delivery mode (AUTO, CCIP, or MAN) indicates on the HUD. When a Walleye. Maverick, Harpoon. HARM, SLAM, JSOW. or JDAM is selected, the MDI weapon abbreviation identifying the weapon is displayed in this location, For the AGM-65 Laser Maverick, an additional indication displays when it is locked on (MAV LKD).
Displayed Impact Line (DIL) (CCIP bombing mode only): The solid line DIL displays in CCIP bombing mode. The DIL extends between the velocity vector and the center of the CCIP. It provides a steering reference to aid you in maneuvering the aircraft to position the CCIP cross on the target. If the CCIP cross is not present, the DIL extends to the HUD FOV.
Continuously Computed Impact Point (CCIP) (CCIP bombing mode only): This symbol displays only in the CCIP bombing mode. It indicates the impact point of the selected weapon if the weapon button were immediately pressed. If the current weapon impact point is not in the HUD FOV, the CCIP cross is not displayed, and a reflected cue displays on the DIL. In this case, the DIL displays to the HUD FOV limit in the direction of the computed impact point, and reflected cue displays. The reflected cue is a line displayed along the DIL at the same distance above the bottom of the DIL (HUD limit point) as the actual distance the CCIP is below the HUD limit point.
If the flight profile is flown so as to keep the target above the reflected cue, then a solution is ensured. During a dive, the reflected cue moves down the DIL and is blanked when the CCIP cross appears. If the actual CCIP is so far below the HUD that the reflected cue would be at or above the velocity vector, then the reflected cue is blanked from the display.
For learning more about HUD please look at Jane's F/A-18 Flight manual.
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