Head Up Display

Head-Up Display
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Cockpit art courtesy of Cockpits.nl

The Head Up Display (HUD) is a glass window at the front of the cockpit which superimposes important flight data and weapon information over the pilot's view. It is used to provide important information to the pilot without requiring him to look down into the cockpit, improving situational awareness. The information displayed includes the aircraft's attitude, airspeed, and altitude, navigational information, and weapon targeting information.

The aircraft's cockpit contains a CRT embedded in the front of the cockpit underneath the HUD. This display projects the information upwards onto the glass screen of the HUD, which reflects the information into the pilot's field of view. The "screen" of the HUD contains no electronics, it is simply a glass reflector.

Most of the weapon systems in Falcon 4 (and in real life) have their own HUD presentations, which are discussed under the pages for those weapons. This page will only discuss common features and the basic navigational display.

Basic Symbology

The HUD packs a lot of information into a very small space. It is important to be able to quickly isolate and read the data that you are looking for, and this requires a good working knowledge of the HUD's basic layout. The following image (from the F-16 MLU avionics manual) shows an overview of the information displayed on the HUD. For simplicity, the discussion of the HUD symbology is separated into left, right, and center portions. NOTE: this image shows the HUD in the NAV master mode. A-A, A-G, and the various master and override modes have different symbology, which is discussed on the page for that specific weapon or mode.

Head-Up Display Schematic
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Airspeed Scale

The airspeed tape is located on the left side of the HUD. It contains a readout of your aircraft's current speed, as well as a moving "tape". The notch underneath the C points to your aircraft's current airspeed (in this case, 597 knots). The "tape" has notches at 10-knot intervals, and is labeled every 50 knots (except that the label closest to your current airspeed is not shown).

The C indicates that the airspeed tape is currently displaying calibrated airspeed. However, the tape is also capable of displaying true airspeed (in which case a "T" is displayed) or your ground speed (in which case a "G" is displayed). See below for details on how to select this. The number immediately beneath the airspeed tape is your current Mach number. This page describes the different types of airspeeds.

Steerpoint Caret

The "caret" or V shape on the right side of the airspeed tape (it's not specifically labeled in this diagram) points to the airspeed you need to maintain in order to get to the selected steerpoint by the time-on-station specified in your flight plan. This adjusts itself so that it is correct regardless of the airspeed type you have selected. If you keep the caret aligned with the airspeed notch, you will arrive at your selected steerpoint exactly on schedule.

G Forces

Immediately above the airspeed tape is the current G force on the aircraft. This is 1.0 when you are straight and level flight, but will increase when you turn or do other flight maneuvers. The maximum G force the aircraft has experienced since it started is displayed underneath the Mach number (in this case, it is 2.6). This is used for maintenance, and also so you can check the maximum G force you pulled in a turn (in case you were distracted or missed it).

SOI Symbol

An asterisk is displayed above the airspeed scale when the HUD is the currently selected sensor of interest. This only applies to certain types of weapons such as the AGM-65 Maverick which can be visually aimed using the HUD.

Current Mode/Weapon Status Indication

The current armed state of your weapons is displayed directly beneath the airspeed scale. If the master arm switch is set to "armed", ARM will be displayed here. If it is set to "sim", SIM will be displayed, and if the weapons are set to "safe", nothing will be displayed.

The current HUD mode is displayed underneath the maximum G-force indicator (in this case it is "NAV" for navigation mode). NAV is the default mode, which is used for general navigation with no weapon system selected. There are a large number of HUD modes, most of which are tied to particular aircraft weapon systems.

Altitude Scale

The current altitude of the aircraft is displayed on the right side of the HUD. This is similar to the "tape" used by the airspeed indicator. The pointer points to your current altitude on the tape, and also displays it as a number (rounded to the nearest 10 feet). The tape is labeled every 500 feet in multiples of 100 feet, and has unlabeled tick marks every 500 feet.

By default, the altitude indicator toggles between barometric altitude and radar altitude based on your altitude (it transitions from radar to baro when you climb above 1500 feet, and transitions from baro to radar when you descend below 1200 feet). It can also be forced to use baro or radar altitude regardless of the altitude - see below for more details. Note that when radar altitude is displayed, the tape uses a fixed scale from 0 to 1500 feet - instead of the tape moving, the pointer will move up and down the scale.

The radar altitude is displayed in a box beneath the altitude scale when baro altitude is selected.

Altitude Low Setting

The currently selected ALOW setting is displayed immediately beneath the radar altitude. The ALOW setting is the radar altitude at which the VMS will start complaining because you're flying too low. In this case, it is set to 200 feet above ground, so if you are lower than 200 feet with your landing gear up you will hear a continuous "Altitude, Altitude" warning.

Steerpoint Information

Some basic navigational information is displayed in the lower right corner of the HUD. The slant range to the currently selected steerpoint is displayed beneath the ALOW setting - B018.7 means that the aircraft is exactly 18.7 nautical miles from the steerpoint. In the real aircraft, this takes into account the aircraft's altitude - if you are directly over the steerpoint at an altitude of 2 nautical miles, it will display B002.0. However, different versions of Falcon 4 may or may not simulate this.

The time until reaching the steerpoint is displayed directly beneath the slant range. Beneath the ETA is another indication which shows the "geographical" (i.e., non-slant range) distance to the steerpoint, as well as the number of the currently selected steerpoint. In this case, steerpoint 3 is selected, and the aircraft is 18 nautical miles away.

Aircraft Attitude and Heading

There are several items in the center of the HUD which show the aircraft's current attitude and heading. The pitch ladder is the horizontal lines displayed at 5 degree increments up the center of the HUD. The position of the gun cross relative to the pitch ladder shows the aircraft's pitch attitude - for example, if you put the gun cross on the 10 degree line, the aircraft has a pitch attitude of 10 degrees. Note that the ladder bars for negative pitch attitudes are dashed, and may be differently shaped.

Depending on the current HUD mode, one of two roll indicators will be displayed - the BAI (Bank Attitude Indicator) is a small scale which rotates around the flight path marker, showing the current bank angle. The roll indicator is located at the bottom of the HUD, and looks like a larger mirror image of the BAI. The roll indicator has tick marks at 10, 20, 30, and 45 degrees, while the BAI has tick marks at 10, 20, 30, and 60 degrees.

The aircraft's heading is displayed as a tape, which may be located at the top or bottom of the HUD, depending on the mode. The concept is similar to the airspeed and altitude tapes, only it is horizontal instead of vertical. There is a caret or notch located above the heading tape, which denotes the heading to fly to the currently selected steerpoint. In the real aircraft, this displays magnetic heading, however Falcon 4 displays true heading.

Gun Cross

The gun cross is the "gun sight" of the aircraft - it is the point towards which the aircraft's M61 cannon is aimed. More importantly, it represents the point at which the aircraft's nose is pointed. This contrasts with the flight path marker, which displays the path the aircraft is actually flying.

Flight Path Marker

The flight path marker is the circle with three tick marks arranged around it - notice how it sort of looks like an aircraft from behind. The FPM is used to display the direction the aircraft is actually traveling, as opposed to the direction the nose is pointed in. If you put the FPM at a point on the ground and hold it there, that will be the point where you impact the terrain. The FPM also has several other uses, including determining angle of attack, and for navigating the aircraft to the next steerpoint. See the angle of attack and steerpoint pages for more information.

Steerpoint Information

The "tadpole" and steerpoint diamond symbology is used to help navigate your flight plan. See the steerpoint page for more information.

HUD Control

The HUD has controls in two places: the Integrated Control Panel and the right console of the cockpit.

ICP Controls

The ICP has several controls which affect the HUD display. The SYM knob, at the top left corner of the ICP, is used to control the brightness of the HUD. This is useful for night flight, when you want to dim cockpit lighting to preserve your night vision. The drift cutout switch on the HUD is used to control the position of the pitch ladder. If it is set to normal, then the pitch ladder will always be centered around the flight path marker. If it is set to DRIFT C/O, the pitch ladder will always be displayed at the center of the HUD, regardless of the position of the FPM. See the ICP page for more details.

HUD Panel on Right Console

The HUD control panel is located on the right console, between the sensor power panel and the interior lighting panel. It consists of eight switches which are used to control the amount and type of information displayed on the HUD.

HUD Control Panel
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The scales switch is used to control which data is displayed as a "tape" on the HUD. The default is VAH, in which case your altitude, airspeed, and heading will be displayed as tapes, and you will see the roll indicator instead of the BAI. VV/VAH mode is the same as VAH, except that a vertical velocity scale is added immediately to the left of the altitude tape. When the switch is set to OFF, the altitude, airspeed, and heading tapes are removed (although the numeric indication is still displayed), and the BAI is displayed instead of the roll indicator.

The FPM switch is used to control the display of the pitch ladder and flight path marker. The default is ATT/FPM, in which case both will be displayed. If set to FPM, only the flight path marker will be displayed, and if set to OFF, neither the pitch ladder nor the FPM will be displayed.

The DED data switch is used to control the display of DED data on the HUD. If the switch is flipped to up, the DED display will be copied to the lower portion of the HUD. This is useful if your DED is damaged or if you want to have access to DED data without looking down into the cockpit.

The depressible reticle switch may not be modeled in all versions of Falcon 4. When Modeled, this switch is used to place a large circular, stationary reticle in the HUD. Use of the knob at the upper right corner of the UFD to set the circle's vertical position. This Reticle is used for manual bombing modes (non-computer calculated.) Used in bombing competitions, and when equipment failures knock out computer assisted bombing reticles.

The velocity switch is used to control which type of airspeed is displayed. The available options are CAS (calibrated/indicated airspeed), TAS (true airspeed), and ground speed.

The altitude switch controls which altitude unit is displayed. You can select radar altitude, barometric altitude, or auto. If the switch is set to auto, radar altitude will be used until you are more than 1500 feet above the ground, at which point it will automatically switch to baro altitude. When you descend, it will switch from baro to radar altitude at 1200 feet.

The brightness control switch selects the brightness mode of the display. If set to "night", the maximum brightness of the HUD will be approximately half of the maximum "day" brightness. If the switch is set to auto, the HUD will automatically select its brightness mode using the system time. Note that you can also change the brightness of the HUD using the SYM knob on the ICP.

The test step switch is used to display various test patterns on the HUD. It is not modeled in Falcon 4.

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