Embraer E-Jet Flight Controls

The Embraer E190 and E190-E2 fly with conventional control columns, control wheels and rudder pedals, but behind them most of the flight controls are fly-by-wire. On the first-generation E190 the fly-by-wire system commands every power control unit (PCU) except those of the ailerons, which keep a conventional cable system. The E190-E2 is fly-by-wire in all axes, ailerons included. Hydraulic power for the PCUs comes from the three hydraulic systems (see E-Jet hydraulic system).

The system works in two modes: a normal mode, with the protection and compensation functions, and a direct mode, in which the surfaces follow the pilot's inputs without them. The A320 instead has normal, alternate and direct laws, and side-sticks where the E190 and E190-E2 keep a column and wheel. The general principles are covered in fly-by-wire. This article describes the E190 and the E190-E2 and names the model each figure belongs to; the other models are introduced in E-Jet family and flight deck.

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Primary flight controls

On the first-generation E190, the main surfaces are moved as follows:

The EASA data sheet describes the ailerons, flaps, spoilers, elevator and rudder of the ERJ 190-100 as composite structures.

Ailerons. If one aileron PCU fails, that aileron's force authority is halved and an AILERON LH (or RH) FAIL advisory appears; the aileron becomes inoperable only if both its hydraulic systems fail. A jammed aileron is handled with the aileron disconnect handle, a recall item; once pulled, the system can be reconnected only on the ground by maintenance. In roll, a small wheel input moves only the ailerons, and the multifunction spoilers join in as the wheel angle increases. With cables to hydraulic PCUs, the E190's ailerons are signalled like those of the 737 NG, while its spoilers are fly-by-wire.

Rudder. The E190's single rudder has two PCUs in an active and standby arrangement, each able to give full control; the standby PCU also acts as a hydraulic damper against flutter. If the rudder pedals jam, the flight control modules can still provide yaw damping and turn coordination through the rudder, but a jam at the rudder PCU itself locks the rudder hydraulically.

Fly-by-wire and control modes

On the first-generation E190, four flight control modules (FCM) compute functions such as elevator thrust compensation, yaw damping and turn coordination, and actuator control electronics (ACE) units control the surfaces: three P-ACEs, each connected to two PCUs, for the rudder and elevators, the SF-ACEs for the slats and flaps, the S-ACEs for the multifunction spoilers and the HS-ACE for the horizontal stabiliser. Its actuators work in an active and standby arrangement whose channels swap roles after the first ground power-up of each day; on the E190-E2 the actuators are all active in normal mode.

The first-generation E190 reverts to direct mode after the loss of data from all FCMs or multiple ACE failures, and the crew can select it on the FLIGHT CONTROLS MODE panel. Activation of the stick shaker does not cause it. A loss of airspeed data puts the elevator into direct mode: the pilot then controls the elevator directly, and elevator thrust compensation, tail strike avoidance, angle of attack limiting and the autopilot are lost, while the stick shaker, an AFCS function, still works. In direct mode the speedbrakes and ground spoilers are unavailable and the roll spoilers work with a fixed gain.

On the E190-E2, normal mode includes a normal flight envelope, which the operating manual lists as pitch attitude between -15° and +30°, bank up to 33°, the angle of attack shaker and VMO/MMO. The envelope functions are not available in direct mode, in which the elevator follows column position directly, with stability augmentation but without stall or envelope protection, and the autopilot is unavailable. The FLT CTRL N-MODE FAIL message puts all the flight controls into direct mode; the flight control synoptic page then shows all yellow, and a lower VMO applies. Unlike the first generation, the E2 keeps its multifunction spoilers in direct mode.

Two first-generation safeguards complete the picture. A fly-by-wire backup battery, a lead-acid unit charged from DC ESS bus 3, keeps the elevators and rudder controllable for 15 min when neither normal nor emergency electrical power is available (see E-Jet electrical system). And a hydraulic built-in test (PBIT) of the actuators runs on the ground when all three hydraulic systems are pressurised and the fluid is above 10 °C. It takes about 1 min, during which FLT CTRL TEST IN PROG is shown; moving the controls interrupts it, with the FLT CTRL NO DISP caution.

Pitch control and trim

Elevator thrust compensation (ETC) on the first-generation E190 applies elevator inputs of ±5° to reduce the pitching moment of a thrust change. The FCMs compute it from N1, Mach and pressure altitude; if one of its sensors fails, ETC is lost and ELEV THR COMP FAIL is displayed.

The first-generation E190 trims in pitch with the horizontal stabiliser, moved by the HS-ACE. The control wheel pitch trim switch cuts out after 3 s of continuous operation in flight, or 5 s on the ground, with both halves pressed; holding only one half for 7 s deactivates the switch until maintenance acts. In electrical emergency or after a loss of airspeed data, only HS-ACE channel 2 is enabled, and manual and autopilot trim run at half rate. Mach trim counters Mach tuck with the autopilot disengaged, above M 0.70, and with no manual trim, no A/P disconnect press and no other trim command; Transport Canada lists it among the E190's flight control differences from the E170 and E175.

The E190-E2 changed the trim philosophy. Trim inputs act primarily through the elevator, and the stabiliser moves only secondarily, to reduce the elevator load; on the ground, trim moves the stabiliser directly. There is therefore no pitch trim runaway procedure on the E2, and the operating manual gives only the FLT CTRL HSTAB FAIL caution. The quick disconnect button on the control wheel disconnects only the autopilot. The E2 also has no trim backdrive: the wheel and rudder pedals do not move when roll or yaw trim is used, whereas on the E1 roll and rudder trim move their neutral feel position.

After an engine failure in the climb (see E-Jet engines and APU), the E190-E2's best beta function applies about 75 % of the rudder needed and shows a cyan sideslip target for the best climb performance. Yaw trim is disabled while it acts, so the E2 has no yaw trim after an engine failure.

Spoilers and speedbrakes

Each wing of the first-generation E190 has five spoiler panels. Panels 1 and 2, inboard, are ground spoilers only. Panels 3 to 5, outboard, are multifunction spoilers (MFS), used for roll, as speedbrakes, as ground spoilers and in the steep approach mode. The E190-E2 adds a fourth pair of multifunction spoilers, on hydraulic system 2, for eight MFS panels in all. On the first-generation E190:

• Speedbrakes. In flight only the multifunction spoilers act as speedbrakes, up to 30°. They retract automatically with flaps 2 or more, or with the thrust levers above 70° thrust lever angle (TLA) in a go-around, with the SPDBRK LEVER DISAG caution.
• Ground spoilers. After touchdown they deploy with weight on wheels, TLA below 26° and either wheel speed above 45 kt or airspeed above 60 kt. They retract when wheel speed has stayed below 45 kt for 5 s, or when TLA exceeds 35° after landing.
• Steep approach. Only the outboard panels 4 and 5 are used, at 10° with the column neutral, varying from 18° at -4° of column to 0° at +4°.

Slats and flaps

The slats and flaps of the first-generation E190 are controlled by the SF-ACEs and driven by power drive units (PDU), each with two DC motors. With one motor or one ACE failed, or in electrical emergency, the surfaces move at half rate with a FLAP LO RATE or SLAT LO RATE advisory; FLAP FAIL or SLAT FAIL appears only when both have failed. In flight, positions 5 and FULL are available only with the landing gear down and locked (see E-Jet landing gear, brakes and steering); on the ground the interlock is disabled. The QRH electrical emergency procedure uses flaps 3 for landing, with a higher approach speed and no autoland.

The two generations use different angles at the end of the range: at FULL the E190-E2 sets slats 25° and flaps 35°, the E1 slats 25° and flaps 37°, and positions 4 and 5 on the E2 both set slats 25° and flaps 25°. The E2 also has a fifth pair of slat panels. Its limits are:

The maximum altitude with flaps extended on the E190-E2 is 20,000 ft, and the AFM advises a 10 kt margin to VFE when selecting a setting. The load factor limits are -1 g to +2.5 g with flaps 0, and 0 g to +2 g with any flaps extended.

Protections and degraded modes

The first-generation E190's protections are these:

• Angle of attack limiting. When the AFCS activates the stick shaker, the nose-up authority of the column is progressively reduced. AOA limiting takes priority over tail strike avoidance, there is no stick pusher, and the HS-ACE does not respond to trim while the shaker is active.
• Tail strike avoidance (TSA). On landing it uses two radio altimeters and works below 70 ft with flaps 5 or FULL; on take-off a 20 ft figure applies, with the height estimated from vertical speed. There is no cockpit indication when TSA acts.
• Elevator thrust compensation. Described above, it is lost with a sensor failure or a loss of airspeed data.

On the E190-E2 the equivalent protection is the normal flight envelope described above, whose functions are not available in direct mode.

Degraded operation follows from the architecture. A loss of airspeed data on the E190 puts the elevator in direct mode and halves the trim rate; an electrical emergency halves the slat and flap rate; a jammed aileron is disconnected; and if both normal and emergency power are lost, the backup battery keeps the elevators and rudder working for 15 min. On the E190-E2, the FLT CTRL N-MODE FAIL message and an all-yellow flight control synoptic page mark the change from normal to direct mode. The spoiler and high-lift theory behind these systems is in spoilers and speed brakes and high-lift devices, and the other E-Jet systems, from fuel to ice and rain protection, have their own articles.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.