Ditching — The DITCHING Pushbutton & Special Scenarios

This is ATA 21's only article on ditching. The DITCHING pushbutton — a guarded button on the cabin-pressure panel — closes five classes of opening with one press, sealing the cabin against water.

1. The DITCHING pushbutton — close five openings

To prepare for ditching, the flight crew must press the DITCHING pushbutton on the CABIN PRESS control panel to close the outflow valves, the emergency ram air inlet, the avionics ventilation overboard valve, and the pack flow control valves. DITCHING pb (guarded): ON: The outflow valves, emergency ram air inlet, avionics ventilation overboard valve, cargo compartment isolation valves and pack flow control valves close. The cargo extract fans stop automatically. — FCOM DSC-21-20-30 + DSC-21-20-40

[!important]- The five classes of opening (the full list)

Opening	ATA 21 part	Mode
Outflow valves (fwd + aft)	outflow valves	stepper motor closes
Emergency ram-air inlet	ram-air valve	electrically closed + does not respond to the RAM AIR pb
Avionics overboard valve	AEVC overboard valve	electrically closed
Pack flow control valves	PFCV 1 + 2	electrically closed (as OFF)
Cargo isolation valves	fwd + aft + bulk	electrically closed
(+) Cargo extract fans	cargo fans	stop automatically

The DITCHING pb is ATA 21's only "one press, many controls" button — it duplicates all the single buttons (PACK / RAM AIR / AVNCS VENT / CARGO ISOL) but closes them all at once.

2. The flotation line — the design philosophy

[!note]- Above vs below the flotation line — the DITCHING behaviour is opposite

The fuselage has a conceptual flotation line (the waterline when the aircraft floats). The rule: below-the-line parts close on DITCHING (keep water out); above-the-line parts keep working (keep ventilating for survival).

Below the line → DITCHING closes	Above the line → DITCHING leaves alone
Outflow valves / cargo isolation valves / AEVC overboard valve / cargo extract fans	the cabin itself (passenger breathing) / cockpit air
Emergency ram-air inlet / PFCV 1+2 (lower belly)	—

The reason: after a ditching the fuselage floats — any open below-the-line opening lets seawater into the cabin → the aircraft floods and sinks. Closed = buoyancy retained.

[!warning]- The DITCHING pb is an overriding priority

With DITCHING ON, all other ATA 21 buttons' "open" commands are inhibited: the PACK pb does not open the PFCV; the RAM AIR pb does not open the ram-air valve; the EXTRACT pb is disabled; the CARGO ISOL pb does not open the isolation valves; and CAB PR MODE SEL MAN + V/S CTL FULL UP does not open the outflow valves (unless they are already in manual control). A protection against panic mis-pressing — once ditching is decided, the system prevents re-opening anything to the water. The button is guarded against inadvertent operation. (CAUTION: on the ground, an inadvertent DITCHING ON stops the air-conditioning — reverse it to OFF to recover.)

3. The QRH DITCHING procedure

The QRH DITCHING procedure is in PRO-ABN-MISC (not PRO-ABN-AIR — ditching spans many chapters). The ATA-21-relevant core:

   ... (emergency-landing preparation)
   CABIN CREW ... NOTIFY FOR DITCHING
   DITCHING pb ... ON                      ← close the five openings
   [assess wind + sea at 500–1000 ft]
   At 500 ft AGL: BRACE FOR IMPACT [order]
   For flare: TOUCH DOWN AT MIN V/S; TARGET PITCH ATT 11°
   At touchdown: ALL ENG MASTERS ... OFF; APU MASTER sw ... OFF; EMER EVAC PROC ... APPLY

4. Wind & sea assessment

Wind direction: This may be determined by observation of the waves, which move and break downwind. Spray from wave tops is also a reliable indicator. Wind speed: A few white crests : 8-17 kt / Many white crests : 17-26 kt / Streaks of foam along water : 23-35 kt / Spray from waves : 35-43 kt. Sea state: This is best determined from a height of 500 ft to 1 000 ft. At lower height, the direction of the swell may be less obvious than the direction of the waves, even though the waves are much smaller. — FCOM PRO-ABN-MISC

[!tip]- Reading the wind speed from the foam — the visual estimate

Pilots rarely have precise low-level wind at sea — they estimate visually. The four foam states: a few white crests 8–17 kt; many white crests 17–26 kt; streaks of foam 23–35 kt; spray from the wave tops 35–43 kt. At 1000 ft, one glance at the sea estimates the wind band → choose the ditching direction.

[!important]- Swell vs wave, and the 500–1000 ft window

Wave (a few seconds, small, from the local wind) vs swell (10–20 s, large, from a distant storm). The main ditching risk is the swell (large, long-period) — ditch parallel to it to avoid a big drop. But waves are visually more obvious than swells, so flying too low you see only the waves, not the swell. 500–1000 ft is the highest-yet-lowest window where the swell is visible.

[!note]- Direction — drift > 10° requires into-wind

No swell → ditch into wind. Swell + drift ≤ 10° → parallel the swell + as into-wind as possible. Swell + drift > 10° → into-wind. Why: drift on touchdown = a large yaw → a possible severe roll → catastrophic. The FCTM: "The presence of drift on touchdown is not dangerous, but every effort should be made to minimize roll." Teaching line: a roll-over is the worst ditching outcome — avoid roll even at the cost of not paralleling the swell.

5. Touchdown — TARGET PITCH ATT 11°

For flare: TOUCH DOWN AT MIN V/S, TARGET PITCH ATT 11°. — FCOM PRO-ABN-MISC

[!important]- 11° pitch — the A330 ditching design parameter

Unlike a land touchdown (flat, matching the runway), a ditching is tail-first (11° pitch) — the aft fuselage + rear engines absorb the impact energy. The engineering: a high pitch loads the wing root evenly (minimum wing impact); the aft fuselage touches first (the engine cowls do not hit the water directly); the nose does not bury (no water surging into the cockpit). With TOUCH DOWN AT MIN V/S (minimum rate, not max speed) → minimum energy.

   At touchdown:
   ALL ENG MASTERS ... OFF   (isolate the fuel system; reduce the electrical load)
   APU MASTER sw ... OFF     (the APU plenum is low — water ingress → shut it off)
   EMER EVAC PROC ... APPLY

6. The ALL ENG FAILURE approach speeds

The ALL ENGINES FAILURE VAPP varies with weight (from the FCOM PRO-ABN-MISC table):

[!note]- VAPP and the ditching speed

An all-engine failure usually precedes a ditching (e.g. a well-known river ditching after a dual-engine flameout). The final-phase VAPP = the touchdown speed. The A330 ditching speed varies widely with weight (120 t → 150 kt vs 240 t → 180 kt) — choose the VAPP for the current fuel + payload.

7. Special / stacked scenarios

[!important]- High-altitude depressurisation + cabin fire + cargo fire — three at once

One of the hardest simulator scenarios — three L3 red warnings together. The priority: (1) CAB PR EXCESS CAB ALT (ata-21-24) → the emergency-descent memory items at once; (2) in parallel the SMOKE/FUMES procedure; (3) in parallel the CARGO SMOKE procedure (usually auto-isolation + auto agent on some aircraft). Task split: PF flies + the descent; PM the SMOKE + CARGO procedures + ATC + PA; the cabin crew assist + monitor the smoke spread.

[!warning]- All bleed lost — emergency ventilation gone (no packs + no RAM AIR)

An extreme case: packs 1+2 failed + APU bleed failed + a bleed leak, and RAM AIR cannot open (ΔP > 1 PSI or ditching selected). The recourse: descend below FL 100 → RAM AIR ON (if ditching not selected); or cabin masks + continuously monitor the cabin altitude (if no RAM AIR). The A330 has no second backup ventilation (the design assumes the simultaneous total loss of packs + APU + RAM AIR is extremely improbable) — the most anxious training scenario.

8. Operations

When to press the DITCHING pushbutton

   Press: all-engine failure over water; uncontrollable fire + no airport over water;
          severe structural damage + water (no reachable airport); a sudden uncontrollable emergency, water the only option
   Do not press: pressurisation not lost; the aircraft can keep flying to a land runway;
          on the ground before takeoff (inadvertent → return to OFF, per the FCOM CAUTION)

The cabin after DITCHING ON

The CAB FANS (recirculation) still work; the cabin lights / PA are not ATA 21 (ATA 23/33).

Combinations

Self-test

[!note]- Q1. Which five openings does the DITCHING pushbutton close?

The outflow valves (fwd + aft), the emergency ram-air inlet, the avionics overboard valve, the cargo isolation valves (fwd + aft + bulk), and the pack flow control valves (PFCV 1+2); the cargo extract fans also stop automatically. The principle: close all below-the-flotation-line openings to keep water out.

[!note]- Q2. With DITCHING ON, can the pilot open RAM AIR with the RAM AIR pb?

No. DITCHING ON inhibits every single button's "open" command — RAM AIR is forced closed regardless of the pb. A protection against panic mis-pressing once ditching is decided. To recover: return the DITCHING pb to OFF, releasing the inhibits.

[!note]- Q3. At 1000 ft you see streaks of foam along the water — the wind speed?

23–35 kt (Beaufort 6–7). The four bands: a few white crests 8–17 kt; many white crests 17–26 kt; streaks of foam 23–35 kt; spray from the wave tops 35–43 kt.

[!note]- Q4. A large swell + ~15° drift — which ditching direction?

Into-wind (drift > 10° requires into-wind). Even with a large swell, paralleling it with 15° drift means a large sideslip → severe roll → roll-over risk. The 10° drift threshold — above it, into-wind takes priority. A roll-over is the worst ditching outcome — avoid roll, even at the cost of not paralleling the swell.

[!note]- Q5. What is the A330 ditching target pitch, and why?

11°. The engineering: tail-first → the aft fuselage absorbs the impact; a high pitch loads the wing root evenly; the engine cowls do not hit the water directly; the nose does not bury. With TOUCH DOWN AT MIN V/S (minimum rate) → minimum energy.

Key takeaways

Common misconceptions

Scope — what this article covers and defers

References

A330 specifics per FCOM DSC-21-20-30 / DSC-21-20-40 (the DITCHING pushbutton closing the outflow valves, the emergency ram-air inlet, the avionics overboard valve, the cargo isolation valves and the pack flow control valves, with the cargo extract fans stopping automatically, and the guarded button with its ground CAUTION) and FCOM PRO-ABN-MISC (the QRH DITCHING procedure — CABIN CREW NOTIFY, DITCHING pb ON, the wind/sea assessment with the foam-state speed bands and the 500–1000 ft window, BRACE FOR IMPACT, the 11° flare and minimum-V/S touchdown, ALL ENG MASTERS OFF / APU MASTER OFF / EMER EVAC; and the ALL ENG FAILURE VAPP table). The flotation-line above/below philosophy, the override-priority list, the swell-vs-wave reasoning, and the 11°-pitch engineering are integrative syntheses. The well-known river ditching is cited generically without an operator name. The EMER EVAC and ALL ENG FAILURE detail is deferred to ATA 25 / 22-24. All engineering detail is from the A330 knowledge base; no cross-type comparison is made, and no fleet tail numbers appear.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.