GPWS Response / Terrain Avoidance

한 줄 요약: GPWS Warning (PULL UP / TERRAIN TERRAIN PULL UP) → “PULL UP MAX THRUST” call → A/P·A/T off, Max thrust, Wings level, 20° pitch, Speedbrakes retract, Gear/Flap 유지 until terrain separation assured

Trigger (POM 8.3)

GPWS CAUTION — 아래 aural alert 중 하나 (POM 8.3)

• CAUTION OBSTACLE
• CAUTION TERRAIN
• SINK RATE
• TERRAIN
• DON’T SINK
• TOO LOW FLAPS
• TOO LOW GEAR
• TOO LOW TERRAIN
• GLIDESLOPE
• BANK ANGLE

Note: As installed, some repeat (POM 8.3, Note 1)

GPWS WARNING — 아래 aural alert 또는 조건 (POM 8.3)

HL7775 – HL8284

• “PULL UP”
• “OBSTACLE OBSTACLE PULL UP”
• “TERRAIN TERRAIN PULL UP”

HL7700 – HL7756

• “PULL UP”
• “TERRAIN TERRAIN PULL UP”
• 기타 unacceptable flight toward terrain 상황

🚨 LIMITATION

QRH에는 “GPWS” 전용 Non-Normal Checklist 없음. Warning 발생 시 즉시 Terrain Avoidance maneuver 수행 (FCTM 7.14). Reference: POM 8.3 Memory Item.

Memory Items 🔴 (POM 8.3 — GPWS Warning 시)

🚨 MEMORY ITEMS — GPWS WARNING 발생 시 즉시 수행

PF:

1. Call “PULL UP MAX THRUST”
2. Disconnect autopilot
3. Aggressively apply maximum thrust
4. Simultaneously roll wings level and rotate to an initial pitch attitude of 20°
5. Retract speedbrakes
6. If terrain remains a threat, continue rotation up to the pitch limit indicator or stick shaker or initial buffet
7. Do not change gear or flap configuration until terrain separation is assured

PM:

1. Call “MAX THRUST, SPEEDBRAKES DOWN”
2. Disconnect autothrottle(s)
3. Assure maximum thrust is set and speedbrakes are retracted
4. Verify all required actions have been completed and call out any omissions
5. Monitor vertical speed and altitude (radio altitude for terrain clearance, barometric altitude for minimum safe altitude)
6. Monitor radio altimeter for sustained or increasing terrain separation
7. Call out any trend toward terrain contact (e.g. “RA INCREASING / DECREASING”)

흐름 요약 (POM 8.3)

flowchart TD
    A[GPWS Alert 발생] --> B{Alert 유형?}
    B -- "CAUTION (SINK RATE / TERRAIN / TOO LOW GEAR·FLAPS / GLIDESLOPE / BANK ANGLE 등)" --> C{고도?}
    B -- "WARNING (PULL UP / TERRAIN TERRAIN PULL UP / OBSTACLE OBSTACLE PULL UP)" --> W[Terrain Avoidance Maneuver 즉시 수행]
    C -- "Stabilized Approach Criteria 초과 (IMC >1000 HAT, VMC >500 HAT)" --> D[Correct flight path 또는 Go-Around]
    C -- "Stabilized Approach Criteria 이하 (IMC ≤1000 HAT, VMC ≤500 HAT)" --> E[Go-Around 즉시 개시]
    C -- "TOO LOW FLAPS·GEAR at final approach" --> F[🚨 Go-Around 필수]
    C -- "GLIDESLOPE at·below Stabilized Approach Criteria" --> F
    W --> G["PF: PULL UP MAX THRUST call, A/P off, Max thrust, Wings level, 20° pitch, Speedbrakes retract"]
    G --> H{Terrain still threat?}
    H -- Yes --> I[Continue rotation up to PLI / stick shaker / initial buffet]
    H -- No --> J[Gear·Flap 유지 until terrain separation assured]
    I --> J
    J --> K{Clear of terrain?}
    K -- "GPWS Warning stops + safe flight assured" --> L[Slowly decrease pitch, accelerate, Clean up aircraft as required]

Reference Steps — GPWS CAUTION (POM 8.3)

조건	PF	PM
Stabilized Approach Criteria 초과 (IMC: >1000 ft HAT, VMC: >500 ft HAT)에서 caution 발생	Correct flight path 또는 Initiate go-around	—
Stabilized Approach Criteria 이하 (IMC: ≤1000 ft HAT, VMC: ≤500 ft HAT)에서 caution 발생	Initiate go-around	—

🚨 LIMITATION

“TOO LOW FLAPS” 또는 “TOO LOW GEAR” caution이 final approach segment에서 발생 → 반드시 go-around (POM 8.3)

🚨 LIMITATION

“GLIDESLOPE” caution이 Stabilized Approach Criteria 이하에서 발생 → 반드시 go-around. 500 ft HAT (visual approach 최저치) 이하라도 적용 (POM 8.3)

Note: “SINK RATE” caution이 Stabilized Approach Criteria 이하에서 일시적 descent rate 이탈로 발생 시, VMC에서 captain이 모든 운항 요소 평가하여 이탈이 즉각·안전하게 보정됨을 판단하면 접근 계속 가능 (POM 8.3, Note 2)

Glideslope Deviation Alert — 취소·억제 가능 조건 (POM 8.3)

아래 조건에서는 below G/S deviation alert 취소·억제 가능 (POM 8.3):

• Localizer approach
• Circling approach from an ILS
• Deliberate approach below glideslope이 요구되는 조건
• Unreliable glideslope signal

Nuisance Alert 판정 — Terrain/Obstacle Caution (POM 8.3)

재접근 중 GPWS terrain/obstacle caution이 이전과 동일하게 반복되고 아래 두 조건 모두 충족 시 nuisance alert로 간주하여 접근 계속 가능 (POM 8.3):

• Daylight VMC에서 지형·장애물 위험 없음을 positive visual verification
• 항공기가 instrument approach의 published lateral/vertical path에 위치

Reference Steps — GPWS WARNING (POM 8.3)

Terrain Avoidance Maneuver — PF/PM Callout (POM 8.3)

When GPWS Warning Alert begins or encountering situations resulting in unacceptable flight toward terrain:

PF	PM
Call “PULL UP MAX THRUST”	Call “MAX THRUST, SPEEDBRAKES DOWN”
Disconnect autopilot	Disconnect autothrottle(s)
Aggressively apply maximum thrust	Assure maximum thrust is set and speedbrakes are retracted
Simultaneously roll wings level and rotate to an initial pitch attitude of 20°	Verify all required actions have been completed and call out any omissions
Retract speedbrakes	Monitor vertical speed and altitude (radio altitude for terrain clearance and barometric altitude for a minimum safe altitude)
If terrain remains a threat, continue rotation up to the pitch limit indicator or stick shaker or initial buffet	Monitor radio altimeter for sustained or increasing terrain separation
Do not change gear or flap configuration until terrain separation is assured	Call out any trend toward terrain contact (e.g. “RA INCREASING / DECREASING”)

When clear of terrain (GPWS Warning Alert stops and safe flight is assured):

• Slowly decrease pitch attitude and accelerate
• Clean up aircraft, as required

💡 PITCH LIMIT

“Aft control column force increases as the airspeed decreases. In all cases, the pitch attitude that results in intermittent stick shaker or initial buffet is the upper pitch attitude limit. Flight at intermittent stick shaker may be required to obtain positive terrain separation. Smooth, steady control avoids a pitch attitude overshoot and stall.” (POM 8.3)

Note: Do not use flight director commands (POM 8.3)

Note: Maximum thrust can be obtained by advancing the thrust levers full forward if the EECs are in the normal mode. If terrain contact is imminent, advance thrust levers full forward. (POM 8.3, Note 3)

Nuisance Alert 판정 — GPWS Warning (POM 8.3)

재접근 중 GPWS warning이 이전과 동일하게 반복되고 아래 두 조건 모두 충족 시에만 nuisance로 간주 가능 (POM 8.3):

• Daylight VMC에서 지형·장애물 위험 없음을 positive visual verification
• 항공기가 instrument approach의 published lateral/vertical path에 위치

QRH — GPWS 관련 EICAS Messages (QRH 15.3, 15.6)

QRH에 GPWS 전용 non-normal checklist는 없음. 시스템 상태 관련 EICAS 메시지만 존재 (QRH 15.3, 15.6):

EICAS	의미	QRH
[ ] GND PROX SYS	A ground proximity warning system fault occurs.	QRH 15.3
TERR OVRD	The ground proximity terrain override switch is in OVRD.	QRH 15.6
[ ] TERR POS	Terrain position data is lost.	QRH 15.6

Note (GND PROX SYS): “Some or all ground proximity alerts are not available. Ground proximity alerts that occur are valid.” (QRH 15.3)

Note (TERR POS): “Position data for the ND terrain map and look-ahead terrain alerts are lost. Ground proximity alerts that occur are valid.” (QRH 15.6)

FCTM — Recommended Technique (FCTM 7.14, 7.15)

💡 TECHNIQUE

“The Ground Proximity Warning System (GPWS) PULL UP Warning occurs when an unsafe distance or closure rate is detected with terrain below the airplane. Look-ahead terrain alerting (as installed) also provides an aural warning when an unsafe distance is detected from terrain ahead of the airplane. Immediately do the Terrain Avoidance maneuver found in the non-normal maneuvers section in the QRH.” (FCTM 7.14)

“Look-ahead terrain alerting can be temporarily disabled when GPS can be verified as unreliable. Basic GPWS alerts are still available.” (FCTM 7.14)

“Do not attempt to engage the autopilot or autothrottle until terrain clearance is assured.” (FCTM 7.14)

GPWS Callout Acknowledgement (FCTM 1.19)

“The PF should acknowledge all GPWS voice callouts except altitude callouts during approach while below 500 feet AFE. No callout from the PM is necessary if the PF has already acknowledged the GPWS voice callout.” (FCTM 1.19)

RNAV (RNP) AR Operations — Terrain Avoidance (FCTM A.2.11)

“During RNAV (RNP) AR operations in close proximity to terrain on departure or approach, crews may experience occasional momentary terrain caution-level alerts. If these alerts are of short duration and have ceased, crews should verify they are on the required path and consider continuing the procedure using LNAV and VNAV. Depending upon where initiation occurs, the risks of terrain contact while executing a terrain avoidance maneuver may be higher than continuing on the required track.” (FCTM A.2.11)

“Terrain warning-level alerts always require immediate action. The most appropriate crew actions regarding airplane bank angle and track during a terrain avoidance maneuver depend on where the maneuver is initiated. Operators should determine the most appropriate course of action for each leg of the procedure, if necessary, so crews are prepared to react correctly at all times.” (FCTM A.2.11)

⚠️ GOTCHA — RNP AR

RNP AR 운용 중 caution-level alert는 경로 유지 vs terrain avoidance 기동 간 판단 필요. Warning level은 무조건 즉시 기동.

Company Policy (POM 8.3)

⚠️ Boeing vs Company Difference

Boeing (FCTM 7.14): Terrain Avoidance maneuver는 QRH non-normal maneuvers 섹션 참조. 초기 pitch attitude·PF/PM callout 등 세부는 Boeing QRH MAN 섹션에 정의. Asiana (POM 8.3): QRH 참조 대신 POM 8.3에 GPWS Response 전체 절차 통합 — GPWS CAUTION 대응 기준(Stabilized Approach Criteria)까지 명시. PF “PULL UP MAX THRUST” / PM “MAX THRUST, SPEEDBRAKES DOWN” call 고정.

Cross-References

• Windshear Escape Maneuver (POM 8.3) — Windshear alert 시 유사 구조 Memory Item maneuver — PF/PM call + Max thrust + 15° pitch. GPWS는 20° pitch, Windshear는 15° pitch. 동시 발생 가능성 인지.
• Crosswind Takeoff (FCTM 3.12) — 이륙 초기 저고도 단계에서 GPWS Warning 발생 시 측풍·terrain 복합 상황 고려
• Takeoff Phase Index — V1~1,000 ft AGL 비상 절차 전체 개요
• III Approach (POM) — CAT II/III 접근 중 GPWS alert 대응 기준