Sierra Pattern A320 -
| Scenario | Why Sierra? | Example |
| :--- | :--- | :--- |
| Noise Abatement (RNAV Arrival) | Keep aircraft high and slow over populated areas before a steep descent into a valley airport. | KASE (Aspen): Sierra at DODGE at 15,000ft before dropping into Roaring Fork Valley. |
| ATC Flow / Sequencing | Absorb time and lateral distance without descending into lower airspace occupied by departures. | Arrival into LHR or JFK: Level segment at 8,000ft for 15 NM. |
| Step-Down Approach (VOR/NDB) | Precisely meet a step-down fix altitude while managing speed for flap extension. | VOR/DME approach: Sierra at FAF altitude before final glidepath. |
| Engine Anti-Ice / Performance | Avoid prolonged idle descent (which can cool engines too much). Level segment warms engines. | Icing conditions (TAT < 10°C). |
In Airbus A320 pilot training, the "Sierra Pattern" (often abbreviated as the SRS/GA TRK mode) refers to the specific, automatic lateral and vertical guidance logic that engages the moment a Go-Around (GA) is initiated.
Why "Sierra"?
Unlike Boeing aircraft, which require the pilot to hand-fly the missed approach path initially, the Airbus automatically flies a predefined "pattern in the sky" to ensure terrain clearance and obstacle protection. sierra pattern a320
To understand the Sierra Pattern, one must first accept a hard truth: the A320, without engines, has the glide ratio of a safe. At idle thrust, a typical airliner achieves a glide ratio between 15:1 and 20:1 (losing 1 nm of altitude for every 15-20 nm forward). An A320 at engine failure? Closer to 9:1 or 10:1.
With both engines windmilling (creating drag) or stopped (creating even less hydraulic pressure), the aircraft sinks at roughly 3,000–4,000 feet per minute. From a cruise altitude of 35,000 feet, the pilot has less than 10 minutes of glide time to diagnose the problem, restart the engines, and—if that fails—find a survivable landing zone.
The Sierra Pattern is the checklist for when engine restarts fail. | Scenario | Why Sierra
Let’s assume you are on final approach to Runway 27L at a busy airport. You call "Go-around" at 200 feet AGL.
The term "Sierra" is the NATO phonetic alphabet for the letter "S." In Airbus emergency procedures, the Sierra Pattern refers to a specific, high-altitude holding pattern flown under dual-engine failure conditions.
It is formally titled: "PROC-V - DUAL ENG FAILURE" with the sub-procedure "Holding pattern (Sierra pattern)." Unlike Boeing aircraft, which require the pilot to
The goal is singular: Maximize total energy (kinetic + potential) to keep the engines spooling for a windmill restart attempt.
The pattern is defined by three parameters:
| Feature | Sierra Pattern (A320) | Conventional (e.g., Boeing 737) | | :--- | :--- | :--- | | Initial lateral mode | GA TRK (holds existing track) | TO/GA (wings level or runway heading) | | Initial vertical mode | SRS (maintains V2) | Pitch hold or MCP selected | | Pilot workload | Low (monitoring) | Higher (immediate pitch/thrust setting) | | Obstacle protection | Automatic (via FMGC) | Pilot-managed |
| Feature | Sierra Pattern | Echo Pattern | Delta Pattern |
| :--- | :--- | :--- | :--- |
| Vertical Profile | Level segment | Continuous idle descent | Climb segment |
| Thrust | Idle -> Thrust -> Idle | Idle | TOGA -> Thrust -> Idle |
| FMS Symbol | S | (no symbol, default) | E or D |
| Primary Use | Meet altitude constraints with energy loss | Fuel-efficient descent | Terrain/ATC climb requirement |
| Fuel Burn | Moderate (increased) | Minimum | High |