Sierra Pattern A320 [portable] File
The Sierra Pattern: The A320’s Critical Defense Against Dual-Engine Flameout
In the world of commercial aviation, few events trigger an immediate, high-stakes response like a dual-engine flameout. Suddenly, a sophisticated jetliner becomes a heavy glider. For pilots of the Airbus A320, the memory aid for handling this precise emergency is the "Sierra Pattern." While not a secret, it is a rarely-discussed, high-angle, high-risk maneuver that lives in the deepest files of the Flight Crew Operating Manual (FCOM).
This article deconstructs the Sierra Pattern: what it is, why it exists, the physics of unpowered flight in an A320, and the terrifyingly narrow window of success it provides.
Do NOT engage the Autopilot too early.
If you engage the AP below the minimum engagement altitude (typically 100 feet RA on takeoff, but 400-500 feet for GA), you risk the AP fighting your manual turn. The A320's Flight Director (FD) in GA mode will command wings level on initial climb. To fly the Sierra Pattern, you must temporarily disregard the FD or change the FD mode. sierra pattern a320
4. Step-by-Step: Flying the Sierra Pattern
| Phase | Pilot Action | FMA (Flight Mode Annunciator) |
| :--- | :--- | :--- |
| 1. Decision | "Go Around, Flaps" (Select TO/GA detent) | LVR CLB flashes; SRS | GA TRK |
| 2. Positive Climb | Call "Positive Rate" → Gear Up | SRS | GA TRK |
| 3. Acceleration | At Thrust Reduction Alt (e.g., 1000’ AAL):
- Check LVR CLB blue → Pull thrust to CL detent. | THR CLB | SRS | GA TRK |
| 4. Transition | At Acceleration Alt (e.g., 1500’ AAL):
- SRS automatically disconnects.
- Select NAV or HDG as needed.
- Retract flaps on schedule. | OP CLB | NAV (or HDG) |
3. Pilot Technique: Flying the Sierra Pattern
Do not attempt to fly a continuous idle descent. You must actively manage the level segment. The Sierra Pattern: The A320’s Critical Defense Against
Missed approach / leaving the hold
- If hold is published on approach with a missed approach procedure, brief the missed approach segment and altitudes.
- When cleared to leave the hold IFR, confirm new clearance and reprogram FMS as needed.
1. Core Definition: What is a "Sierra Pattern"?
In Airbus FMS logic (Honeywell or Thales), flight plans are built with lateral waypoints (Lat/Long) and vertical constraints (ALT or ALT AT). A standard descent uses a continuous idle path.
The Sierra Pattern occurs when the FMS calculates that the aircraft must fly level (or nearly level) at an intermediate altitude before continuing the descent to meet a subsequent crossing restriction. If hold is published on approach with a
Visual Representation:
Cruise FL350 ---> Idle Descent ---> [Sierra Pattern: Level segment at 10,000ft] ---> Idle Descent ---> IAF at 3,000ft
In the MCDU (Multipurpose Control and Display Unit), the vertical revision page for the affected waypoint will show a "Sierra" symbol (S) next to the altitude constraint, indicating a "Hard" or "Step" constraint requiring a level segment.
Sierra Pattern in the Flight Simulator (Microsoft Flight Simulator / X-Plane)
For virtual A320 pilots (using the FlyByWire A32NX or Fenix A320), the Sierra Pattern is fully simulated. Here is how to practice:
- Setup: Start a short final approach at 1000 feet.
- Program the MCDU: Ensure your missed approach procedure (MISSED APP) is loaded in the F-PLN page. The S-waypoint will appear.
- Execute: At 500 feet, press TO/GA. Advance throttles.
- Watch the magic: Pull the HDG knob. Watch the ND draw the magenta "S" line. The aircraft will fly the exact published procedure.
- Debrief: Use the replay tool to check if you maintained the 15° pitch and never stalled.
Pro Tip: Practice a "Windy Sierra Pattern." Crosswinds can push you off the magenta line. Do not hand-fly aggressively; let the autopilot (if engaged) or FD guide you.