The Su-25T has several operational modes. Some basic symbols displayed on the Heads-Up Display (HUD) are common across most modes.
2-53: Su-25T Basic HUD Symbols
· The aircraft datum in the center of the HUD rotates to indicate aircraft bank and roll.
· A heading tape appears at the top of the HUD. Tick marks are labeled in tens of degrees (e.g. the number “35” indicates a heading of 350 degrees).
· To the left of the heading tape is the indicated airspeed (IAS). The assigned airspeed for the next waypoint (depending on the operational sub-mode) is shown directly above the IAS.
· An accelerometer is displayed under the IAS in the form of a bar scale and triangular marker. A marker to the right of center indicates acceleration; to the left of center - deceleration.
· To the right of the heading tape is the current flight altitude in meters. At altitudes less than 1500 m above ground level (AGL), radar altitude is indicated with 1 m accuracy. Above 1500 m AGL, pressure altitude above sea level (ASL) is indicated with 10 m accuracy. The assigned altitude for the next waypoint (depending on the operational sub-mode) is shown directly above the current flight altitude.
· When the aircraft is on the assigned flight path, the director circle is aligned with the aircraft datum in the center of the HUD. When the aircraft flies away from the assigned flight path, the director circle indicates the direction to return to it.
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· To the right of the pitch tape is a vertical velocity indicator (VVI). Aircraft rate of ascent or descent between ±30 m/s is indicated by an arrow and a numeric value. The arrow stops at the VVI limit and the numeric value flashes with the vertical speed exceeds 30m/s.
· The current operational mode is indicated in the lower left corner of the HUD.
· The distance to the next waypoint in km is indicated at the bottom of the HUD.
The HUD provides navigation data enroute. There are three navigation sub-modes: МРШ (ENROUTE), ВЗВ (RETURN TO BASE), ПОС (LANDING). These submodes are selected automatically at appropriate points along the assigned flight path, and can also be cycled manually by pressing the [1] key.
· The МРШ (ENROUTE) sub-mode features a director circle displayed in the HUD. It indicates the direction to the next assigned waypoint.
· The assigned altitude and airspeed enroute to the next assigned waypoint are displayed above the current altitude and airspeed in the HUD.
· The next waypoint number is indicated in the lower right, below the pitch scale («3» in Fig. 2-54 below). The distance to the next waypoint is displayed at the bottom of the HUD. After arriving to the assigned waypoint is reached, the director circle automatically shows the direction to the one following, and the waypoint number in the lower right will advance.
2-54: МРШ (ENROUTE) Navigation Sub-Mode
· In the ВЗВ (RETURN) sub-mode, the director circle guides the pilot to intercept the runway approach glide-slope.
· The landing aerodrome can be cycled by pressing the [~] key. The aerodrome ID number is indicated in the lower right, below the vertical velocity scale indicator («9» in Fig. 2-55. The aerodrome control tower provides voice instructions when the aircraft approaches the runway.
· In the ПОС (LANDING) sub-mode, a glide slope error circle appears in the HUD. The aircraft is on the correct approach glide slope when the director and glide slope circles are both centered in the aircraft datum.
· The director circle guides the pilot to intercept the desired glide slope. The aircraft is on the correct approach glide slope when the director and glide slope circles are both centered in the aircraft datum.
· «К» and «Г» indicate the presence of localizer and glide slope beacons, respectively.
2-55: Landing Navigation Sub-Mode
Fi0 (Phi-Zero) is the Su-25T’s main “air-to-air” combat mode for use with infrared-homing (IRH) missiles. The aiming principle is very simple - upon activating this mode with the [2], [3] or [4] key, the available R-60 or R-73 IRH missiles are automatically selected for use, and the HUD appears as shown in Fig. 2-55. The missile seeker detects targets within a two degree conical field of view, centered directly ahead along the missile boresight axis. The center of the missile seeker field of view is indicated by the aiming cross in the HUD. The pilot aims by maneuvering the aircraft to place the cross over the target. Launch is authorized as soon as the missile seeker acquires the target, regardless whether it is in range. Since the missile seeker cannot measure the range to the target, the pilot must estimate the range visually before firing, to ensure the shot is within parameters (especially for pursuit intercepts, where the missile needs enough energy to run down the target). In a pursuit intercept against a target flying at a speed of 700 km/h, the R-60 can be fired from 1500-2000 meters range, the R-73 from 3000-4000 meters.
2-56: Фи0 (Fi0) Longitudinal Aiming Mode
· Фи0 in the lower left corner corner indicates the longitudinal aiming mode.
· The pilot maneuvers the aircraft to put the target in the crosshairs.
· ПР indicates that the infrared-homing (IRH) missile seeker has locked the target.
· The selected weapon is indicated below pitch scale in the lower right: “60” for R-60 (AA-8 “Aphid”) missiles, “73” for R-73 (AA-11 “Archer”).
· Weapon availability and state of readiness are indicated along the bottom of the HUD. Fig. 2-56 illustrates R-60 missiles at weapon stations # 1 and 11, with the flashing rectangle around station 1 indicating that it is locked and ready for launch.
The Su-25T aircraft can employ numerous types of “air-to-surface” weapons. This arsenal includes iron bombs, cluster bombs (CBUs), guided bombs (GBUs), submunition dispensers, aerial rockets, and guided missiles. It is one of only a few aircraft in the Russian Air Force that can employ modern precision weapons such as “Vikhr” antitank missiles with laser beam-riding guidance, Kh-25ML, Kh-29L, and Kh-29T laser- and TV-homing missiles, KAB-500KR TV-guided bombs, and Kh-25MPU and Kh-58 anti-radiation missiles.
The category of ballistic-trajectory “free-fall” weapons includes all "iron" bombs, e.g. FAB-500, FAB-250, FAB-100, BetAB-500, and ODAB-500, RBK cluster bombs and KMGU dispensers, ZAB-500 incendiary bombs etc.
To employ free-fall weapons against ground targets, the pilot activates the ОПТ-ЗЕМЛЯ (GROUND) mode [7] and chooses the required free-fall bombs, cluster bombs or containers with the [D] key. Bombing symbology then appears in the HUD, including the “ОПТ-ЗЕМЛЯ” mode indicator in the lower left corner. The selected weapon is displayed in the lower right below the pitch scale, with all free-fall munitions designated as “АБ”. The aim and release procedure is effectively the same for all free-fall weapons: the pilot maneuvers the aircraft to superpose the continuously computed impact point (CCIP) pipper over the target and, when all release criteria are satisfied, pulls the trigger in response to the “Launch Authorized” signal displayed in the HUD.
2-57: Free-Fall Bombing Mode (CCIP)
· The continuously-computed impact point (CCIP) pipper indicates the impact point of the next bomb near the bottom of the HUD.
· The bomb fall line extending from the impact point indicates the vertical earth axis from the pipper origin.
· Free-fall ammunition is indicated by “АБ” below the pitch scale.
· “Launch Authorized” indicates that all the primary release conditions such as range, altitude and velocity are satisfied and the weapon can be safely released.
· “ОПТ ЗЕМЛЯ” in the lower left corner indicates the visual bombing mode.
· Weapon availability and state of readiness are indicated along the bottom of the HUD. Fig. 2-57 illustrates the display when aerial bombs are suspended from the 2nd, 3rd, 4th, 8th, 9th, and 10th hardpoints. The flashing square framing hardpoint 2 indicates the ready weapon.
High drag munitions and some cluster submunitions may follow a strongly curved trajectory that puts their impact point below the lower edge of the visible HUD at almost any angle of dive, so that the CCIP pipper can not be visibly placed onto the target. In this case the continuously-computed release point (CCRP) or "invisible zone" bombing mode is used instead of CCIP.
In the CCRP mode, the pipper is visible at the extreme lower edge of the HUD. The pilot maneuvers the aircraft to place the pipper over the target, pulls the trigger and holds it pressed. The pipper becomes a fixed diamond to mark target. A director circle appears in the upper half of the HUD part to help the pilot fly the aircraft to the release point. The tip of the “keel” of the aircraft datum symbol in the HUD should be kept aligned with the center of the director circle. The pilot flies the aircraft with the trigger held depressed until the bombs are automatically released.
2-58: Free-Fall Bombing in the “Invisible zone” (“H3” or CCRP)
The range bar at the left side of the HUD becomes a time scale, indicating the number of seconds remaining before automatic bomb release. The arrow indicating the time remaining before release doesn’t begin moving until 10 seconds before release. Successful automatic release depends on strictly following the assigned flight path with the correct G-loading – the tip of the datum “keel” must be held at the center of the director circle. When the remaining time drops to zero, the bombs are released, and the pilot can let go of the trigger.
The phrase “aerial rocket” is usually used to describe any unguided rockets and missiles that lack sensors and are uncontrolled after launch. These include S-5 rockets carried in the UB-32 launcher, S-8 rockets in the B-8 launcher, S-13 rockets in the UB-13, and S-24 and S-25 heavy rockets. The Su-25T’s built-in NPPU-8 includes the GSh-20 30-mm twin-barrel cannon with a 200 round ammunition magazine.
Rockets are employed by activating the ЗЕМЛЯ (GROUND) mode [7] and selecting the desired rocket with the [D] key. The HUD appears as shown in Fig. 2-59:
2-59: Rocket Strafing Mode
· The strafing pipper below the aircraft datum symbol indicates the rocket impact point.
· The selected type of rocket will be displayed under the pitch scale. Fig. 2-59 illustrates the C5 symbol for the S-5 rocket.
· Available weapons of the selected type are indicated along the bottom of the HUD.
· ОПТ ЗЕМЛЯ (VISUAL GROUND) mode is displayed in the lower left corner.
To employ rockets, the pilot detects the target visually and maneuvers the aircraft into a shallow dive, placing the pipper onto the target. The maximum launch range is reached when the arrow in the range bar reaches the upper tick mark and “Launch Authorized” is displayed in the HUD.
Strafing with the built-in gun (internal cannon) is conducted by practically the same procedure. Guns are selected by activating the ОПТ ЗЕМЛЯ (VISUAL GROUND) mode [7] and the cannon [C]. The HUD display appears as shown in Fig. 2-60 below:
2-60: ВПУ (Internal Cannon) Cannon Strafing Mode
· The strafing pipper indicating the shell impact point appears under the aircraft datum.
· The remaining ammunition quantity in quarters is displayed beneath the pitch scale. A full magazine is indicated with “4”, the last 1/4th of remaining ammunition with “1”.
· “ВПУ” internal cannon mode is displayed in the lower left corner.
To use the internal cannon, the pilot detects the target visually and maneuvers the aircraft into a shallow dive, placing the pipper onto the target. The maximum firing range is reached when the arrow in the range bar reaches the upper tick mark and “Launch Authorized” is displayed in the HUD.
Precision “smart” weapons include “Vikhr” antitank guided missiles with laser beam-riding guidance, Kh-25ML and Kh-29L laser-homing missiles, Kh-29T TV-homing missiles and KAB-500KR TV-guided bombs. Bombs and missiles that employ TV guidance are considered “launch-and-leave” (“fire-and-forget”), since they home autonomously and do not require support from the launching aircraft after release. Laser-homing and laser beam-rider weapons require that the target be illuminated with the on-board laser during the weapon’s entire time of flight (TOF).
The use of precision weapons is made possible by the onboard I-251 “Shkval” (daytime-only TV) or podded “Mercury” (LLTV for night operations) targeting systems. The image from either system is displayed on the IT-23M TV display in the upper right corner of the Su-25T control panel.
Precision weapons are employed by selecting the ЗЕМЛЯ (GROUND) mode [7] and activating either the onboard “Shkval” [O] or podded “Mercury” [CTRL-O] system. The HUD will then appear as shown in Fig. 2-61 below:
2-61: “Shkval” or “Mercury” Targeting System HUD
· The circular laser cursor in the center of the HUD indicates the center of the optical field of view shown on the TV display, and can be slewed with the [,], [.], [/], and [;] keys.
· TB (TV) appears to the left of the range bar, indicating that the “Shkval” targeting system is active (НТВ (LLTV) indicates the “Mercury” system is active).
· The selected weapon is indicated below the pitch scale. Fig. 2-61 illustrates the 9А4172 “Vikhr” antitank missile selected. Kh-25ML (AS-10 “Karen”) missiles are indicated by 25МЛ, Kh-29L (AS-14 “Kedge”) by 29Л, Kh-29T (AS-14 “Kedge”) by 29Т, and KAB-500KR by 500Кр.
· Weapon availability and readiness state are indicated along the bottom of the HUD.
· ЗЕМЛЯ (GROUND) mode is displayed in the left lower corner.
After activating the targeting system, target acquisition is accomplished by slewing the optical sensor field of view (FOV) with [,], [.], [/], and [;] keys. The image is shown on the TV cockpit display. The laser cursor in the HUD will move together with the optical sensor FOV.
2-62: Active “Shkval” Targeting System HUD
Upon activating the targeting system, on the TV-indicator displays the image from the TV camera, together with targeting and attitude information:
2-63: IT-23M TV Display During Target Acquisition With Active “Shkval” System
· The TV cursor, the size of which depends on the expected target size, appears in the center of the display.
· The cursor size, corresponding to the expected target size in meters, is displayed in the upper left corner. In Fig. 2-63 the expected target size has been entered as 10 m. Armored vehicles are about 10 meters in size, aircraft may be from 10 to 60 meters, and ships and buildings usually require the 60 meter setting. The target is automatically locked only if the target in the cursor is within 5 meters of the expected target size, with the exception targets larger than 60 meters that can still be locked with the maximum setting of 60 m. The expected target size and cursor size are adjusted with [Ctrl-+] and [Ctrl--].
·
Along the top and extreme left edge of the
display are azimuth and elevation scales, respectively. The viewing direction
of the currently displayed image is indicated by triangu
· The aircraft pitch is displayed to the right of the view elevation scale.
· An aircraft datum similar to the one displayed on the HUD is duplicated at the center of the TV display. It informs the pilot about the aircraft bank while performing “heads-down” targeting tasks.
· The aircraft altitude above ground level (AGL) is indicated by the radio altimeter in the right upper corner of the display.
· KC at the top of the display, to the left of the radio altitude, indicates that the view steering is under manual control, and no target has yet been locked.
· The estimated missile time of flight (TOF) to the target in seconds is displayed in the lower right corner. After missile launch, this number indicates the time remaining until weapon impact.
· The slant range to the target in kilometers, as calculated with the radio altimeter, is displayed at the bottom of the display.
Upon spotting the target, the pilot moves the laser cursor over it, and the targeting system attempts an automatic lock. To aid in target identification, the TV camera field of view (FOV) can be magnified to 23x (0.73х0.97 degrees) or an intermediate value of 8x. View magnification is controlled with [+] and [-]keys in three steps.
After identifying the target to be attacked, the pilot selects the required weapon and observes the maximum launch range scale in the HUD. When the range to the target and other launch criteria are satisfied, the pilot either simply pulls the trigger for TV-guided weapons (e.g. Kh-29T missiles and KAB-500Kr bombs), or first actives the laser target illuminator for laser-guided weapons (e.g. Kh-25ML, Kh-29L and “Vikhr” missiles) by pressing [Shift-O].
The TV display appears as shown in Fig. 2-64 below:
2-64: The IT-23M TV Display; Target Locked With Active Onboard “Shkval” System
· The current magnification level in indicated in the upper left corner, next to the expected target size.
· AC at the top of the display, next to the radio altitude, indicates that a target has been locked. The targeting system automatically corrects the view direction within the gimbal limits of ±35 in azimuth and from +15 to –85 degrees elevation to keep it pointed at the target, compensating for target and aircraft motion. The boresight direction parallel to the aircraft longitudinal axis is indicated by a long tick mark on the graduated elevation scale and the central tick mark on the azimuth scale.
· With the laser range-finder active, indicated by ЛД (LASER), the slant range is shown at the bottom of the display.
· “Launch Authorized” is displayed above the slant range, near the bottom of the display.
After the laser-guided missiles have hit the target, it’s necessary to deactivate the laser for cooling. The laser generates high power in the target illumination mode and can only function in this mode for a limited time. The required cooling time is approximately equal to the time the laser was working to illuminate the target. The laser automatically switches off after reaching its maximum allowable temperature. It is not recommended to use the laser for more than 20 minutes total per flight, as exceeding this limit can damage it. The ЛД symbol flashes while the laser is still cooling.
“Vikhr” missiles can be launched in pairs with a short delay between each missile, increasing the probability of hitting the target. The supersonic speed of “Vikhr” missiles can also allow multiple targets to be attacked in a single pass.
“Vikhr” missile can be also used against non-maneuvering aircraft such as helicopters and airplanes during target take-off and landing. The procedure for target acquisition is the same for aerial targets as for ground targets, taking into account that the kill probability is much lower.
The Su-25T aircraft can employ Kh-25MPU and Kh-58 antiradiation missiles (ARMs) against a variety of radio transmitter targets including surface-to-air missile (SAM) search, tracking, and target illumination radars. Since radio transmitters operate over a wide band of frequencies, not all transmitters can be targeted by all ARMs. For example, most antiradiation missiles are not designed for use against mobile anti-aircraft artillery (AAA) which use high frequency radars with short range. For more detailed information on ARM characteristics and targets against which they can be employed, see Chapter 6, “Russian Air Force Air-to-Surface Weapons.”
Antiradar missiles require the Su-25T to carry the L-081 “Fantasmagoria” ARM control pod under the aircraft centerline (hardpoint #6).
Antiradiation missiles are employed by selecting the ЗЕМЛЯ (GROUND) mode [7] and activating passive radar detection with the [I] key. The pilot follows indications on the SPO-15 «Beryoza» radar warning receiver (RWR) display to steer the aircraft toward the target emitter. When the target enters the ±30 degree scan zone, a diamond target marker appears in the HUD. If the currently selected weapon is to lock and attack the detected target, a type indicator appears below the target diamond. The HUD appears as shown in Fig. 2-65 below:
2-65: Suppression of Enemy Air Defenses (SEAD) Anti-Radar Mode HUD
· The square-shaped antiradiation missile (ARM) cursor below the aircraft datum can be slewed over the desired target with the [,], [.], [/], [;] control keys.
· The chosen weapon (58 means Kh-58) is indicated below the pitch scale.
· SEAD mode (ПРГ for “anti-radiation seeker”) is indicated in the lower left.
· Targets are indicated as diamond markers in the HUD. Targets that can be locked and attacked by the currently selected weapon are displayed with a type indicator – P for “Patriot” SAM radar, H50 - for “HAWK” SAM radar, etc.
2-66: SEAD HUD With ARM Locked Target
When target markers are visible in the HUD, the pilot designates the intended target to be attacked. The ARM cursor is moved over the intended target with the [,], [.], [/], and [;] keys. The
target is then locked by pressing [TAB]. The target diamond then becomes a circular marker. The range bar displays an arrow indicating the current range to the target and a tick mark indicating the maximum launch range.
· The maximum weapon launch range is indicated as a tick mark on the range bar.
· An arrow indicating the current range to the target moves along the range bar at the left side of the display.
· When an emitting target has been selected, the diamond target marker becomes a circle.
· When all launch criteria have been satisfied, the “Launch Authorized” command is displayed.
· A flashing rectangle around weapon station # 5 indicates that missile is ready for launch.
When all launch criteria have been satisfied, “Launch Authorized” appears, and the pilot pulls the trigger to launch the weapon.
The “grid” is a backup mode, usually used for strafing when the main targeting system is damaged or accurate range data is unavailable. The grid has calibrated scales along two axes. It is used for aiming together with previously tested and known ballistic characteristics of the selected weapon and the current flight parameters. The center of the grid is aligned with the aircraft longitudinal axis.
The fixed or “static” grid can be called up from any combat mode by pressing the [8] key. The current mode will be preserved, but the HUD will be replaced by the static grid. The pilot can toggle the grid on and off with the [8] key.
Aiming corrections in the grid mode are made by the pilot maneuvering the aircraft to place the expected weapon impact point over the intended target. The cross hairs are positioned above the target by the required angle. Barrage rocket or cannon fire is employed at ranges of 200-400 meters.
2-67: Fixed (Static) Grid Sight