Tu-154B ABSU
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ABSU
Automated on-board control system, ABSU - this autopilot TU-154. This is a fairly complicated set that has an important effect on the movement of aircraft. Required characteristics of stability and controllability is not possible to obtain only the aerodynamic design, without the help of the automatic control.
ABSU gets information about the spatial position of the aircraft from a variety of gyroscopic sensors, acceleration sensors, radio and navigation systems. Not all of these sources are modeled in detail, but to retain the principle of action and the main features of the system as a whole.
ABSU manages aircraft at the rate, roll and pitch in manual control, stabilization or automatic (armed) mode.
TU-154 is an irreversible hydraulic control system. Control efforts of yoke and the pedals is transmitted through a system of rods to the front hydraulic swing (booster) and have the output rod booster resulted in movement of the aero surface. To create a force on column apply spring.
Output signals of ABSU served to electrically controlled hydraulic units, RA-56, which is included through the differential lever into connecting rods. Thus, the autopilot continuously connected in parallel yoke and pedals. In automatic mode, automatic effect on the draft through the executive units, on steering wheel is not transmitted due to friction in the wiring and the efforts of spring. In manual control, ABSU affects traction in parallel with the pilot, providing in this case, the optimal control law.
Units RA-56 has triple redundancy, and protection from lock, each unit is powered by three hydraulic systems.
ABSU structurally divided into the longitudinal channel (pitch) and side-channel (roll and heading). Each channel can operate completely independently of the other. Can manual control in one channel, and automatic - in another.
ABSU operates in the following modes:
Manual control. In this mode the autopilot creates the desired control law, "helping" pilot.
Stabilize mode, bank and pitch. Autopilot keeps a given rate, and roll, perhaps the management handles "pitch" and "turn."
Automatic control of altitude, air speed or Mach by change pitch.
Automatic control of the course ("ZK" mode)
Flight of the beacon signals of VOR ("AZ-I", "AZ-II")
Flight signals for the navigation system NVU ("NVU" mode)
Automatic approach signal ILS (mode "Zahod")
Automatic flight glidepath signal ILS (mode "Gliss")
Automatic go-around ("Uhod")
Automatic approach ( "Zahod", "Gliss") enable the automatic flight on glidepath, on signals ILS, prior to a decision height (typically 60 m). Further descending and flare to be done in manual control mode.
In an automatic AP modes, you can use automatic control of speed changes in the engine throttle (autothrottle). Autothrottle prohibited from use in other modes of flight, for example in manual control.
The longitudinal channel, and MET
Longitudinal channel ABSU, automatically stabilizes the angle of pitch, as well as the assignment of aircraft trajectory in the vertical plane of the instrument speed sensors, the number of M and barometric altitude and in an automatic entry - on the glideslope beacon signals by ILS.
In addition to the automatic mode, the longitudinal channel ABSU contributes to piloting an aircraft in manual control. In all modes, the longitudinal channel ABSU has pitch damper, providing the necessary characteristics of stability.
Let's look in more detail the work of the longitudinal channel ABSU in manual control. For a comfortable flight, the aircraft must respond to the motion yoke about the same, to the fullest possible range of speeds and CoG position. Autopilot, affecting the traction control, adjusts the effectiveness of longitudinal control and thus facilitates the piloting. But where AP receives information about value of desired correction? To answer this question, you need to understand how aircraft trimmed.
Tu-154 has no separate surfaces for trimming. Instead, the mechanism of trim effect MET. MET is controlled by electrical signals and move yoke from the central position, thus relieving the efforts of the column. Yoke is equipped with position sensors MET, with these sensors in the AP receives information about the current situation of balancing position of yoke.
It is information about the situation of balancing MET pitch and is the source of the required amount of correction for manual control. It works so well. Pilot trim aircraft pitch and ABSU, depending on the situation of balancing yoke position calculates the desired level of correction. Characteristics of chosen such that in a wide range of operating speeds and CoG remained roughly constant overload one movement of yoke.
Proper work of improving the controllability of the longitudinal channel is possible only if the aircraft has trimmed.
In automatic mode, the longitudinal channel MET disconnected from the buttons on the yoke and the autopilot is connected to the exit through a special amplifier with a threshold characteristic. This allows for continuous trimmed plane in automatic mode and improve the manageability of the system. When the longitudinal channel autopilot is switched from automatic mode to the manual control, the aircraft remains trimmed.
Longitudinal channel ABSU included tumblers 367 in the center console, and improving management system - toggle switch on the panel 550 flight engineer. Automatic stabilization activated by pressing a button-lamp "Stab" (363), and the lamp lights and modes on the panel lights up scoreboard "Stab prod" (139). On display modes ABSU longitudinal channel (358) appears "Stab". ABSU begins to stabilize a pitch angle, which was at the time of incorporation regime. Pitch can be changed through manual wheel 364.
When the longitudinal channel ABSU working mode of stabilization (the button is lit lamp (363), the inscription "Stab" on display 358), by pressing the lamp 359, 360, 361, you can choose to automatically stabilize the Mach, the air speed and barometric altitude, respectively. In the mode turns off "Stab prod" and turn "M" (142), "V" (141), "H" (140). Automatic mode switch back to the stabilization of pitch wheel 364. Shutting down the stabilization of the longitudinal channel made tumbler 367, the short tone sounds, the indicator 358 is a symbol of the yoke and if there was involved the stabilization of side-channel mode - turns off the lamp 363.
Bank channel
Roll and yaw controls are the bank channel of ABSU. The main administration is performed in a channel bank, channel course provides yaw damping (in all modes ABSU) and the removal of slip in carrying out a coordinated turn in the automatic mode lateral channel. The output unit is included in the roll channel rods of ailerons, yaw - in the rods of rudder.
And the channel bank and channel rate trimmed by the MET, but in contrast to the longitudinal channel, the system will improve the driveability is not available. MET just change the neutral position yoke \ pedals.
Bank Channel ABSU stabilize mode can make a coordinated turn from wheel retains a given course of TKS, leads the aircraft navigation signals to computer or ILS signals to landing.
The side channel includes tumblers "Bank (365), and click the button-lamps" Stab (363). The panel lights up scoreboard regimes "Stab bokov" (131), while the PN-5 - button-lamp reset "SBROS PROGRAM" (347). On a side-channel display modes ABSU (356) appears Stab. ABSU will begin to stabilize the bank, which at the time of incorporating regime shift was non-zero, autopilot eliminate bias.
In this mode you can control the plane handle "turn" (362), the turn will be coordinated, ie, feed rate will administer driving directions, eliminating the sideslip.
After switching on the stabilization regime can include ZK mode by pressing lamp "ZK" (345). The course introduces the left handle of HSI (PNP) (102-B) the captain or the second pilot, depending on the position of the switch modes 322. Lamp 130 will be light on.
While bank stabilize mode, you can also select one of the navigation computer: AZ-I (button-lamp 349), AZ-II (button-lamp 350), NVU (button-lamp 348). The first two - this is a flight to the beacon signals VOR, the last - flight of the NVU navigational unit. To enable this mode, you must include the navigation computer tumblers "PREPARATION NAVIGATION (351) and adjust the respective sets of course-IP, or to prepare for the work of the DDP. When selecting the navigation mode, the panel lights up scoreboard modes 132 or 133.
For proper management ABSU in flight beacons VOR, it is necessary to read the relevant section of Flight Manual.
You can press the button-lamps "PROGRAM RESET" (347) for turn off any automatic mode lateral channel. ABSU will switch to "Stab bokov" mode, button-lamps will off, panel lights up scoreboard regimes 131. To access the manual management of the bank channel must be turned off toggle switch "KREN" (365), on board a 356 character yoke and, if not on the channel pitch, the off green button-lamp Stab. Disabling the lateral canal is accompanied by a brief acoustic signal.
Automatic landing approach
ABSU have an important part of the system, enabling the movement of aircraft on a given path - the navigation calculator and calculator of landing. Despite the current name, any computer on a real plane, of course, no. All calculations are performed by analog means. Note that navigation calculator and calculator of landing can't work simultaneously, so at a time can be included or toggle switch 351, or 352, but not both. The navigation calculator provides regimes AZ-I, AZ-II, NVU, and the calculator of landing - an automatic approach to the ILS, the regimes "Zahod" and "GLISS".
Let's see how ABSU works in the performance approach in the automatic mode. In order to ensure the landing in this mode, the system works as follows equippment:
Navigation receiver Kurs-MP, the first set. The receiver should be set to the desired frequency ILS (445).
The compass system TKS must be properly adjusted, and the HSI (PKP) white needle should be set the right course of landing (102-D) by right handle of instrument.
At PN-5 must be enabled computer landing tumblers 352.
ABSU should be in a stabilizing mode (including tumbler 365, lit "Stab" (363))
Tumblers 354 can be included director of a needle at the ADI (PNP). The automatic entry, they mainly serve to control, but in the director are available when you piloting. To prepare, director of call, you need to perform the same operations with ABSU that call for automatic, but the mode of stabilization is not included (tumblers 365, 367 must be switched off). This will be the trajectory control system, in this case - to the ADI director arrows.
The aircraft may control by ABSU in STAB mode (STAB H, ZK or any navigation mode). Using the automatic approach, you can turn the lamp "ЗАХОД" (353, 129 light board), or after the withdrawal of the aircraft on course, or during the flight to the base leg. In this case, ABSU fulfill the turn to the final leg in the automatic mode, the following algorithm:
If the aircraft has not yet entered the beam of ILS, ABSU deploy the machine in the course of planting, and will begin moving closer to the line of a given path at an angle of about 30 degrees. At this point ABSU will manage the aircraft on signals TKS, the desired angle counted from the arrows on HSI (PNP).
The plane will go down in the beam of ILS, ABSU will begin displaying the aircraft to line defined beam. After enter in the zone of ILS beam, autopilot switches to manage signals from ILS, a signal will be switched off from the compass control.
If the aircraft at the time of pressing the button-lamps "ЗАХОД" (353) have already crossed the glidepath, ABSU will conclude the aircraft landing at the course two coordinated turn.
During the approach, the longitudinal channel may be located in manual mode or in the stabilization of a given pitch angle, or in the "H". If the channel is in the longitudinal mode stability, and aircraft in the landing configuration, possibly auto-flight mode on glidepath "GLISS" (355). Mode is enabled automatically, and the light bulb button 355, when the slat provisions glidepath for an instrument HSI (PNP) (102-H) will be located in the center of the device, signaling to the intersection plane line glidepath. If the regime does not automatically, it can be turned on manually by pressing the lamp 355. When the automatic flight glidepath, light boards "GLISS (137) to cover treatment. The aircraft will perform a maneuver in the vertical plane, fits in glidepath and will continue to decline signals ILS.
During the flight on the glidepath, ABSU will change the settings of controls on autopilot signals radar altimeter RV-5, as well as on a real airplane.
ABSU TU-154 was not designed for automatic landing. At the height of a decision usually 60 m, but not less than 30 meters, automatic flight on ILS signals should be stopped and made the transition to manual piloting, disconnecting the autopilot. In the model, for these purposes, ideal trigger joystick that has already been recommended above.
Speed on the glidepath can be defined on tables in RLE, but for the convenience of a virtual pilot, in a model made tip. Tip is called by clicking on the hotspot on the positioner and stabilizer PB (309). It should be remembered that the tooltip shows the values of velocities (Vr and Vref) for the current configuration of the aircraft, and after deploing flaps, for example, the Vref speed will change.
Autothrottle and GoAround mode
ABSU has autothrottle subsystem. AT only works when the computer landing and should be applied only in the automatic approach.
Inclusion autothrottle made tumblers 373 and 374. After switching on, after about seven seconds, two-light lamp system availability of AT, and the system will move to the "alignment mode". Rolling index rate to 108 turns in the agreed terms and will follow the arrow speed.
The inclusion of the stabilization of the speed begin by pressing "C" (372). The button lamp lights, panel lights up scoreboard regimes "AT" (138). Autothrottle begin to stabilize the air speed, which was at the time of pressing the "C". Change the speed using the wheels of 375, given the speed will be displayed on a movable index of US gauge (108). Deviation of the current air speed of a given index can be controlled by the speed indicator on the device ADI (PKP) (101-B). In this model, there is a tips when use wheel 375.
Autothrottle controls the engines throttle. By default, all three are managed by the system. If necessary, one of the engines can be turned off of automatic control by pressing the lamp 377, 378, 379. Button-bulb engine lights disconnected. If more than one engine shut down, turned off the stabilization of the speed and autothrottle transferred to the alignment, the button lamp turns off the "C" and the board 138.
AT system can be switched off by tumblers 374, or the total autopilot disconnect button. In this model, after AT switching off, all throttles will be driven back from the joystick. This should be borne in mind and put throttle levers in the desired position before disconnecting AT.
If the automatic flight signals ILS (enabled "GLISS") to set the throttle levers to take-off mode, ABSU will begin to perform the automatic go-around. The bank channel will go to the bank stabilization, and the longitudinal channel will begin to control the angle of pitch by the go-around calculator. In the regimes extinguished board "rate", "GLISS", "AT" light boards "UHOD" (151). In real life, except for throttle levers, the go-around regime can include a button on the yoke, the model has this feature is not implemented.
In the "go-around" longitudinal channel ABSU will perform a set height, changing the pitch, depending on the speed and flaps situation. Off mode "go-around" can be the same as any automatic mode ABSU.
