Embraer E-Jet Engines and APU

Every Embraer E-Jet has two turbofan engines. The first generation, the E1, uses General Electric CF34 engines; the E2 generation uses Pratt & Whitney PW1900G geared turbofans. On the first-generation E190 (E190 E1) and the E190-E2, the two aircraft this article mostly describes, each engine is run by a full authority digital engine control (FADEC), and an auxiliary power unit (APU) supplies AC power and bleed air. The start sequence, the thrust ratings, the limits and several indications change with the engine, so the model behind each figure is named.

Electrical generation and hydraulics are covered in E-Jet electrical system and E-Jet hydraulic system, and engine and APU fire protection in E-Jet fire protection and oxygen. The principles are in FADEC and engine fuel control, gas turbine engine starting and auxiliary power unit (APU).

The engines

The EASA type-certificate data sheets approve these engines, two per aircraft:

The E190 E1 described here has the CF34-10E5A1, a twin-spool turbofan. Its 24-blade fan is driven by a four-stage low-pressure turbine on the N1 spool, and its nine-stage high-pressure compressor by a single-stage high-pressure turbine on the N2 spool.

The E2 engines are high-bypass geared turbofans: the fan is driven through a gearbox, while the low-pressure compressor is linked to the low-pressure turbine. The E190-E2 described here has the PW1919G and the E195-E2 the PW1921G. The geared turbofan idea is explained with the A220's engine in Airbus A220 engines.

On the E190-E2 each engine's air turbine starter (ATS) is housed in the accessory gearbox (AGB). Driven by pneumatic air, it turns the N2 spool through the radial drive shaft. The AGB also drives the permanent magnet alternator (PMA) that powers the FADEC. Among the differences that Transport Canada's operational evaluation report lists for the E190-E2 and E195-E2 are a single dual-channel ignition exciter supplied from the DC essential buses and an ignition selector position renamed from OVRD to ON.

FADEC and thrust levers

On the E190-E2 each engine's FADEC has two channels: one controls the engine and the other stands by, and they swap roles at every engine start. The FADEC runs on aircraft DC power at first; once N2 exceeds 50 %, the engine's own PMA becomes its normal source.

Besides holding the requested N1, the E190-E2 FADEC protects the N1 limit, runs the automatic take-off thrust control system (ATTCS) and protects against N2 overspeed: it shuts the engine down if N2 reaches 102 % or more three times within 30 seconds.

Idle is scheduled too. On the E190-E2, flight idle and approach idle are raised in icing conditions, but final approach idle, below 1,200 ft AGL in the landing configuration, is not. Because the autothrottle does not take into account the minimum N1 needed for anti-icing, the pilot must watch the cyan minimum N1 mark.

The E190-E2 thrust levers travel through 81.5° and have five detents:

View full schematic

Thrust ratings, ATTCS and flex

Take-off ratings have one value with all engines operating (AEO) and one with an engine inoperative (OEI):

On the E190 E1, TO-2 gives 17.1 klbf AEO and 18.5 klbf OEI, the same pair as the go-around rating, and the continuous rating (CON) is 16.3 klbf. On the E190-E2, TO-2 gives 19.8 klbf OEI. On the E195-E2, TO-2 gives 19.8 klbf AEO and 21.7 klbf OEI, and CON 20.3 klbf in both cases.

The ATTCS is controlled by the FADEC. On the E190-E2 it supplies reserve (RSV) thrust: with the thrust levers at TO/GA, it applies RSV thrust when the N1 difference, ΔN1, exceeds 15 %, as after an engine failure during take-off or go-around, and the crew can also activate it by moving the thrust levers to MAX. It is selected on the ground through the MCDU and defaults to on. There is no ATTCS on/off switch, and the EASA data sheet records an equivalent safety finding for its absence (E2/E-34).

On the E190-E2, a flex take-off uses an assumed temperature higher than the ambient one. It is available with TO-1, TO-2 and TO-3, with ATTCS on or off, but not on a contaminated runway or when windshear is expected. The E190-E2 rejects the take-off data, with ENG NO TAKEOFF DATA, if the measured OAT and the entered take-off temperature differ by more than 5 °C; the E190 E1 threshold is 12 °C. See reduced and derated take-off thrust.

After take-off on the E190-E2, CLB-1 is the default climb rating unless it would be higher than the selected take-off thrust, in which case CLB-2 becomes the default; in AUTO mode either can still be selected. With the flight directors on, the rating changes from take-off to climb once the gear is retracted, the aircraft is above 400 ft AGL and a vertical mode change occurs. With them off, it changes once the gear is retracted and the aircraft is above 3,000 ft AGL and below the ASEL altitude.

Engine start

A normal E190-E2 start runs in three steps:

1. The engine is motored automatically at 8 to 11 % N2, to counter rotor bow. Transport Canada notes that this dry-motoring cycle gives the E2 a longer start cycle.
2. Ignition and fuel come in at 18 % N2.
3. Above 50 % N2 the PMA takes over the FADEC's power supply.

The whole start takes 30 to 78 seconds. On the ground, the crew abort the start if there is no oil pressure within 10 seconds of N2 rising, no N1 rotation by 45 % N2, an ITT above the start limit, oil pressure below the engine limits, or an electrical, pneumatic or starter malfunction before the starter disengages. The starter is limited to 4 minutes, with at most three attempts, followed by a 30-minute cool-down. The E190 E1 uses a cycle table instead: for the first two attempts on the ground, for example, 90 seconds on and then 10 seconds off.

On the E190-E2, with a ground air cart, engine 2 is preferably started first. The cart is parked on the left side, but its connection joins the duct on the right side of the crossbleed valve, so the left engine would see less pressure. With the APU inoperative, the minimum recommended bleed duct pressure before a start is 40 psi minus 0.5 psi per 1,000 ft of aerodrome elevation, before a temperature correction: 38 psi at a 4,000 ft aerodrome.

On the E190 E1 the starter control valve (SCV) closes at 50 % N2 as the engine accelerates to ground idle; if it stays open, the ENG 1 (2) START VLV OPEN caution appears. A thrust lever not at idle for a start or shutdown gives the ENG 1 (2) TLA NOT IDLE advisory. On the ground the E1 FADEC protects against a hot start, with ITT above 740 °C, a hung start and no light-off. In flight it gives no start protection, and the crew must abort the start if there is no light-off within 30 seconds.

The E190-E2 may not use take-off thrust until the oil reaches 24 °C: during ENG WARM UP take-off thrust is not allowed, and using it brings the OIL LO TEMP caution. On the E190 E1 the minimum oil temperature for engine start is minus 40 °C, and thermal stabilisation takes 2 minutes at idle. After landing, the E190-E2 needs 3 minutes from nosewheel touchdown before engine shutdown, 5 minutes being recommended, while the E190 E1's cool-down is 2 minutes at or near idle.

Engine indications and limits

On the E190-E2 the N1 scale carries four marks: a green tick for the maximum N1 allowed in the current mode and conditions, a red tick for the N1 red line, a cyan tick for the minimum N1, and a hollow sector for the difference between actual and requested N1.

Some E190-E2 engine messages, shown on EICAS:

Thrust reversers

On the E190-E2 the thrust reversers are hydraulically actuated and work on the ground only. When reverse is selected, a FADEC interlock holds the engine at idle until the reverser is fully deployed, shown by the green REV label. With one reverser inoperative, selecting MAX REV on both thrust levers gives only MIN REV thrust from the working reverser; to get MAX REV thrust from it, the crew select MAX REV on that engine alone. The principles are in thrust reversers and reverse thrust.

The APU

The E190-E2's APU is a Pratt & Whitney APS2600E with an air inlet door; the EASA data sheet lists it as the Pratt & Whitney Rzeszów APS2600[E] for both E2 models. The E190 E1's APU is the APS2300. The E190-E2 APU burns about 90 to 100 kg/h, drawn from the right-hand fuel tank (see E-Jet fuel system).

The E190-E2 APU is a constant-speed gas turbine that governs its own turbine speed, so its AC generator needs no integrated drive generator (IDG); only the engine-driven generators have IDGs. Engine bleed air has priority: whenever it is being delivered, the APU bleed valve closes so that air cannot flow back into the APU. APU bleed is never used for anti-icing.

On the E190 E1 the APU may supply AC power up to 33,000 ft.

Selecting OFF on the E190-E2 displays the APU SHUTTING DOWN status message, closes the bleed valve and takes the generator off line. The APU then runs a 2-minute cool-down before its fuel shutoff valve closes and the message clears; reselecting ON in the meantime cancels the shutdown. The APU FADEC loses power 2.5 minutes after OFF is selected.

The E190-E2 APU also shuts itself down. On the ground it does so for high EGT, high oil temperature, low oil pressure, an APU fire or a sensor failure, as well as for overspeed, underspeed or a critical FADEC failure; in flight only those last three stop it. APU FAIL, a caution, means the APU has shut down automatically: the crew select OFF and do not restart it, unless the shutdown happened during the start. APU FAULT, also a caution, reports an abnormality; in flight, the automatic shutdown is inhibited.

For comparison with other types, see A320 engines and FADEC and B737 APU.

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.