Sierra Pattern A320 'link'

Sierra Pattern (A320) — Quick Guide

9. Conclusion: A Memorial to Lost Energy

The Sierra Pattern is not a normal procedure. It is an emergency procedure for the failure of the emergency procedure. It is the A320's final argument against gravity.

For the pilot, flying a Sierra Pattern means ignoring the screaming altitude alert, ignoring the instinct to pitch for best glide (which is 180 knots, not 220), and instead deliberately flying a series of inefficient, G-loaded turns at 25,000 feet while the cabin altitude climbs past 15,000 feet.

It is a maneuver designed by test pilots in a simulator at Toulouse, validated by engineers who calculated the exact phugoid frequency of a swept-wing transport category aircraft. It works—on paper. In the real world, it buys time. And in a dual-engine flameout, time is the only currency that matters.

The next time you fly on an A320, look at the overhead panel. Notice the RAT door, the APU fire test button, and the engine master switches. Behind them, in the software logic, lives the ghost of the Sierra Pattern—a silent, desperate dance with physics that you hope you will never, ever need to perform.

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3. Pilot Technique: Flying the Sierra Pattern

Do not attempt to fly a continuous idle descent. You must actively manage the level segment. sierra pattern a320

6. The Outcome: Three Possible Ends

Executing the Sierra Pattern leads to one of three outcomes:

1. Successful Restart (Best Case): The energy pumping works. N2 crosses 15%, fuel is injected, and a glorious "bang" signals engine light-off. You recover, declare an emergency, and land. This has happened twice in A320 history (both due to total fuel starvation followed by successful windmill restarts using the Sierra principle).

2. Controlled Ditching (Survivable): You cannot restart. You glide down to 10,000 feet, and using the remaining Blue hydraulics, you perform a "Sierra Ditching" procedure. You aim for flat water, 10° nose-up, landing gear up. The A320 has a ditching rating of "survivable." (Notable: US Airways 1549 was not a dual-engine failure at altitude; it was a bird strike at low altitude. The Sierra Pattern doesn't apply there.)

3. Controlled Flight Into Terrain (Worst Case): You run out of altitude before solving the problem. The A320 becomes a hole in the ground. This is why the Sierra Pattern is a procedure of last resort—it acknowledges that without energy management, this is the default outcome.

6. Recommendations

To mitigate the risks associated with non-standard or high-energy "Sierra" patterns, the following actions are recommended for A320 flight crews: Sierra Pattern (A320) — Quick Guide 9

1. Early Stabilization: Aim to be fully configured (Landing Conf, Gear Down, Vapp set) by

Here is comprehensive educational content on the Sierra Pattern as it applies to the Airbus A320.

This content is structured for a pilot training manual, a blog post, or a fleet briefing document.

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2. How the FMS Calculates the Sierra Pattern

The FMS uses a 3D predictive algorithm. For a given waypoint (WPT B) with a constraint AT OR BELOW 10000:

1. Geometric Path: The FMS builds a descent path backwards from the runway threshold (or final approach fix) using idle thrust and a default descent speed (e.g., 280kts / Mach 0.78).
2. Constraint Check: If the idle path from cruise passes through 10000 at a point after WPT B (i.e., too high), the FMS cannot meet the constraint with a pure idle descent.
3. Sierra Activation: The FMS inserts a level segment (thrust > idle) starting before WPT B to lose excess energy or time. This segment is computed as:
   • Distance to decelerate from DES SPD to Level SPD
   • Distance to fly level at constraint altitude
   • Distance to accelerate back to DES SPD

Key FMS Page Indicators:

• VERT REV (LAT REV) at WPT B: The altitude line shows 10000 S (S = Sierra = Level segment required).
• PROG Page: The vertical deviation scale may show a "flat" section.
• F-PLN Page: The waypoint altitude will be underlined with a small "S" or displayed as 10000S.

3. Step-by-Step Execution (Condensed from FCOM)

Assuming both engines have failed, windmill restart attempts (Procedure "A") have failed, and you are above FL 250. End of Article

Step 1: Establish Clean Configuration

• Gear: UP
• Flaps: 0
• Speed brake: RETRACTED (critical—drag is your enemy)

Step 2: Target Speed

• Set target speed to 220 knots (Green Dot speed for max lift/drag ratio + buffer).

Step 3: Enter the Sierra Pattern

• Fly a holding pattern at the current position (if over safe terrain) or offset towards a suitable airfield.
• Leg length: 10 NM.

Step 4: The Energy Pump (The "S")

• On the downwind leg, allow speed to increase to 230-240 kts (descend 200-300 fpm faster).
• Initiate a 180° turn towards the inbound leg. During the turn, increase bank to 30°-35°. This increases load factor (G). The increased G-force pushes fuel to the bottom of the tanks and increases relative wind over the fan blades.
• As you roll out on the inbound leg, pitch up gently to trade speed (240 kts) back to 220 kts, gaining 200-300 feet in the process.
• Repeat on the next circuit.

Step 5: Restart Attempts

• Every 2 minutes, attempt a restart (engine master switches OFF, then ON).
• Monitor N2. You need >12% for a successful windmill light-off.