14.2 Boeing EICAS — Engine Indicating and Crew Alerting System

14.2 Boeing EICAS — Engine Indicating and Crew Alerting System

Current EASA Part-66 topic 5.15 supplies only the broad Typical electronic / digital aircraft systems heading at level 1 for every licence category. The pre-12 June 2024 detailed description listed EICAS alongside ECAM and called for general arrangement plus associated BITE; this section uses that former detail as study scope. EICAS means Engine Indicating and Crew Alerting System. It is the Boeing-family solution to the same problem Airbus solves with ECAM: put engine parameters, exceedances and crew-alert messages on glass displays driven by redundant digital computers, and keep a degraded but usable picture after a display or computer failure. Typical classroom types are the 747-400, 757, 767 and 777 families. Not every Boeing aeroplane uses this architecture — many 737 variants use a different engine-instrument arrangement — so the Module 5 candidate learns the EICAS pattern, not a claim that all Boeings are EICAS. Electronic checklists on later types are a separate crew-procedure function and must not be confused with EICAS engine indication. This section does not teach type-course non-normal drills.

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Typical Computer and Display Arrangement

A widely taught EICAS installation uses two EICAS computers (left and right, or similarly named channels) and two display units stacked on the centre instrument panel. Each computer can format both the primary and the secondary image. The computers receive engine data from the EEC/FADEC channels, airframe system discretes and analogue sensors, and they drive the displays, the master-warning and master-caution lights, and the aural-warning path. Associated BITE in those computers records faults for maintenance readout, often through a central maintenance computer.

The two computers monitor each other. If one fails, the remaining computer continues to supply both displays. That is computer reversion. Display-unit reversion is a different path: it produces the compact format described below. Mixing those two ideas is a common examination trap.

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Primary Engine Indication

On a typical EICAS primary display the crew always has the parameters used to set and protect thrust, plus the message field. Primary parameters in standard teaching are N1 (fan speed) or EPR (engine pressure ratio), whichever is the certified thrust-setting parameter for that engine type, and EGT (exhaust gas temperature), the usual limiting temperature during start and take-off. Those values appear as analogue-style tapes or round dials with digital readouts, red-line marks, and amber operating bands where the engine has a time-limited region. An exceedance changes the colour of the readout and is typically recorded for later maintenance interrogation — a BITE-related behaviour that does not require the crew to capture the peak on paper. Total fuel, TAT, thrust-mode information and configuration reminders often share the primary page so that the take-off and go-around picture lives on one display. Later types may show additional digital columns on the primary format. The familiarisation rule is still: whatever the crew uses to set thrust and to see the alert list is primary; oil, vibration and extra rotor speeds are secondary unless that type has moved them onto the primary compact column.

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Secondary Engine Indication, Status and Synoptics

The lower display is the secondary engine and systems window. Typical secondary parameters are N2 and, on three-spool engines, N3; fuel flow; oil pressure, oil temperature and oil quantity; and vibration. On older EICAS types the lower display is called up for secondary engines, for status, or for a limited set of system schematics. On later wide-body types the same surface also carries full synoptic pages (air, hydraulics, electrics, fuel, doors and similar). Status messages are not the same as cautions. They are non-time-critical items — often dispatch or maintenance information — presented in white on a status page when the crew or the system calls STATUS. A status cue on the primary display tells the crew that the status page has content; it does not chime like a caution. Engine secondary parameters can usually be displayed on demand (for example during start, when oil and N2 matter) and then removed to declutter cruise. Automatic presentation during start is typical teaching; exact timing is type-specific.

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Alert Messages: Warning, Caution, Advisory, Status, Communication

EICAS crew alerting is a ranked message list on the primary display, not a set of labelled caption lights for every system.

Priority runs warning, then caution, then advisory, then communication. Within a level, newer messages typically appear at the top of that block. The indent on advisories is a deliberate visual code: if the amber text is inset, it is an advisory, not a master-caution event. Candidates who ignore indent mix up caution and advisory and then cannot explain why the master-caution lights stayed out. Warnings are kept short. Cautions may be numerous after a cascade of system effects; the crew uses CANCEL to walk the list. Communication messages must not be allowed to look like engine warnings — hence the different colour and aural.

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Compact Display Format

Display-unit failure is expected and is designed around. If the lower unit fails, the remaining upper unit typically changes to a compact format: primary N1/EPR and EGT remain, the alert-message field remains, and selected secondary parameters (N2, fuel flow, oil, vibration as space allows) are condensed onto the same screen. If the upper unit fails, the primary picture — including the message field — transfers to the lower unit, again in compact form if needed. The operational rule is that the crew must not lose thrust-setting parameters and alerting because one display surface has failed.

Compact is therefore a display reversion, not an engine degraded mode. FADEC channels continue to run the engine. Compact can coexist with an EICAS computer failure only if the remaining computer can still drive the remaining display — which is why dual computers and dual displays are both required in the general arrangement. Standby analogue engine instruments, where still fitted, are a last-resort path, not the normal compact mode.

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CANCEL, RECALL and Inhibit

A long amber list would cover itself. CANCEL (sometimes labelled CANC) removes displayed caution and advisory messages from the primary field so that messages underneath become visible. RECALL redisplays the cancelled messages that are still true. Red warnings are not cancelled in the same way; they remain until the condition is cleared or until a type-specific warning-inhibit action is used. A fire-bell silence after the fire handle has been treated, for example, is an operational type-course action, not the Module 5 CANCEL function.

EICAS also uses take-off inhibit and landing inhibit, conceptually the same idea as ECAM flight-phase inhibit: selected cautions and advisories are deferred from a high taxi speed through rotation to a safe height, and again around landing, so that the crew is not chimed with amber nuisances at the worst moment. Warnings generally remain available. After the window, parked messages appear. Exact speeds and radio altitudes are type-course data.

[!NOTE] Exceedance recording is a BITE cousin of alerting. When EGT or N1 crosses a limit, the display changes colour and the peak is typically stored for maintenance. Clearing the crew message does not wipe that recorded exceedance. Engineers interrogate it through EICAS maintenance pages or the central maintenance computer.

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Associated BITE and Maintenance Picture

Each EICAS computer runs power-up BITE and continuous monitoring. Faults are isolated toward LRUs: the EICAS computer itself, a display unit, a sensor, an EEC channel, an aural-warning unit. In flight, the crew sees operational warnings and cautions. On the ground, maintenance pages and status messages expose classed faults that never deserved a red warning. As with ECAM, the primary message list is not the wiring diagram. If both displays are dark but standby instruments live, suspect display power or both DUs rather than no engines. If compact has appeared, record which DU failed before cycling power. If CANCEL has emptied the amber list, use RECALL before declaring the system healthy. Module 5 stops at that general arrangement; pushing STATUS through a particular maintenance page is type training.