A320 Dual Hydraulic Failure: Why the PTU Will Not Save You

What happens when an A320 loses both GREEN and YELLOW hydraulic systems?

The HYD G+Y SYS LO PR alert triggers when both 𝗚𝗥𝗘𝗘𝗡 and 𝗬𝗘𝗟𝗟𝗢𝗪 system pressures fall to or below 1,450 psi[cite: 30]. ECAM directs 𝗟𝗔𝗡𝗗 𝗔𝗦𝗔𝗣, 𝗣𝗧𝗨 𝗢𝗙𝗙, and the affected pumps OFF[cite: 31].

𝗦𝗟𝗔𝗧𝗦 operate at 𝗦𝗟𝗢𝗪 speed[cite: 33]. The 𝗕𝗟𝗨𝗘 system remains and is normally pressurized by the BLUE electric pump if AC power is available[cite: 33, 50].

Does the A320 PTU work in a dual hydraulic failure?

No[cite: 35]. The 𝗣𝗧𝗨 runs automatically when the 𝗚𝗥𝗘𝗘𝗡/𝗬𝗘𝗟𝗟𝗢𝗪 differential pressure exceeds 500 psi[cite: 35]. It is a power transfer device, not a fluid transfer device — it requires one system at normal pressure to drive the other[cite: 36, 40]. In a dual 𝗚𝗥𝗘𝗘𝗡 + 𝗬𝗘𝗟𝗟𝗢𝗪 low-pressure condition, there is no source side, so the 𝗣𝗧𝗨 cannot recover the failure[cite: 37].

Why does ECAM direct PTU OFF in a dual GREEN and YELLOW failure?

Two reasons[cite: 40]. First, with both systems below pressure the 𝗣𝗧𝗨 has no driving source and cannot restore either system — hydraulic fluid is not transferred between systems, only power[cite: 40]. Second, leaving the 𝗣𝗧𝗨 running in this condition risks 𝗣𝗧𝗨 overheat and potential loss of the remaining hydraulic circuit[cite: 41]. Selecting 𝗣𝗧𝗨 𝗢𝗙𝗙 is a protective action commanded by the HYD G+Y SYS LO PR procedure[cite: 42].

Which flight controls remain after a dual hydraulic failure on the A320?

There is no fixed memory list of surviving surfaces — read the 𝗙/𝗖𝗧𝗟 𝗦𝗗 page to confirm actual actuator and surface status[cite: 44]. What the HYD G+Y SYS LO PR procedure does tell you is that F/CTL PROT, STABILIZER, SPLR 1+2+4+5, and FLAPS are inoperative, and SLATS operate at SLOW speed[cite: 45]. Aileron and elevator availability depends on which 𝗕𝗟𝗨𝗘-powered servojacks remain — ailerons, for example, are powered by 𝗚𝗥𝗘𝗘𝗡/𝗕𝗟𝗨𝗘 servojack pairs, so 𝗕𝗟𝗨𝗘 keeps them in play[cite: 46].

What is the role of the BLUE hydraulic system in an A320 dual failure?

After 𝗚𝗥𝗘𝗘𝗡 + 𝗬𝗘𝗟𝗟𝗢𝗪 loss, 𝗕𝗟𝗨𝗘 is the remaining hydraulic system[cite: 49]. It is normally pressurized by the 𝗕𝗟𝗨𝗘 electric pump when AC power is available in flight[cite: 50]. If electrical power is also degraded, the RAT drops out automatically and a hydraulic pump coupled to the RAT pressurizes 𝗕𝗟𝗨𝗘[cite: 51].

When does the RAT deploy on an A320 with dual hydraulic failure?

The odor 𝗥𝗔𝗧 does not deploy automatically on a hydraulic failure alone[cite: 54]. It deploys automatically when both AC BUS 1 and AC BUS 2 are lost — typically a dual engine failure or major electrical disruption[cite: 55]. A drop-out 𝗥𝗔𝗧 coupled to a hydraulic pump then pressurizes the 𝗕𝗟𝗨𝗘 system[cite: 56]. The crew can also deploy the 𝗥𝗔𝗧 manually if the situation calls for it[cite: 57].

How does flight control law change after a dual hydraulic failure on the A320?

Normal Law and its protections are lost[cite: 59]. The aircraft transitions to 𝗔𝗹𝘁𝗲𝗿𝗻𝗮𝘁𝗲 𝗟𝗮𝘄 with reduced protections — load factor limitation remains similar to 𝗡𝗼𝗿𝗺𝗮𝗹 𝗟𝗮𝘄, but high angle of attack protection is replaced by low speed stability with stall warning, and bank angle protection is not provided[cite: 59]. Alpha floor is inoperative[cite: 60]. At landing gear extension the aircraft reverts to 𝗗𝗶𝗿𝗲𝗰𝘁 𝗟𝗮𝘄 in pitch and roll[cite: 60]. The trigger is explicit: WHEN L/G DN, DIRECT LAW[cite: 61].

What pressure does the BLUE system operate at on the electric pump versus the RAT?

Normal hydraulic system operating pressure is 3,000 psi. When the 𝗕𝗟𝗨𝗘 system is powered by the 𝗥𝗔𝗧, system pressure is 2,500 psi. The difference is published in the system description and is the verified number to teach.

What does the F/CTL ECAM page tell you in a dual hydraulic failure?

The 𝗙/𝗖𝗧𝗟 𝗦𝗗 page shows flight control surface and status indications: spoiler and speedbrake position, hydraulic pressure to each control, aileron and elevator actuator status, ELAC and SEC computer status, pitch trim, and yaw indications. Use it alongside ECAM STATUS to confirm aircraft state during the HYD G+Y SYS LO PR procedure.

What is the PTU Mirage trap in A320 dual hydraulic failure training?

The PTU Mirage is the assumption that the 𝗣𝗧𝗨 will somehow transfer pressure between 𝗚𝗥𝗘𝗘𝗡 and 𝗬𝗘𝗟𝗟𝗢𝗪 and restore lost flight controls during a dual failure. It cannot. The 𝗣𝗧𝗨 requires a healthy source side, and a dual failure leaves it with none. Recognizing the mirage early — and completing the published ECAM procedure — is the first job. For more detail, read our full A320 dual hydraulic failure breakdown.

Why must "USE MAN PITCH TRIM" be disregarded on an A320 dual hydraulic failure approach?

In the 𝗛𝗬𝗗 𝗚+𝗬 𝗦𝗬𝗦 𝗟𝗢 𝗣𝗥 condition, manual pitch trim is unusable[cite: 16]. The 𝗤𝗥𝗛 explicitly instructs the crew to disregard the "𝗨𝗦𝗘 𝗠𝗔𝗡 𝗣𝗜𝗧𝗖𝗛 𝗧𝗥 trim" message displayed on the PFD[cite: 17]. In 𝗔status𝗟𝗧𝗡 𝗟𝗔𝗪 the elevators provide automatic trim[cite: 18]. At landing gear extension, control reverts to 𝗗𝗜𝗥𝗘𝗖𝗧 𝗟𝗔𝗪 and the mean elevator position is memorized as the trim reference[cite: 18]. This is why stabilizing at 𝗩𝗔𝗣𝗽 before gear extension matters — it sets the trim reference that the aircraft will fly to the runway[cite: 19]. Many crews see the PFD message and reach for the trim wheel. The published procedure forbids it[cite: 20].

What landing configuration does the A320 dual hydraulic failure procedure call for?

𝗙𝗢𝗥 𝗟𝗗𝗚: 𝗙𝗟𝗔𝗣 𝗟𝗩𝗥 𝟯[cite: 22]. With 𝗙𝗟𝗔𝗣𝗦 𝗝𝗔𝗠𝗠𝗘𝗗 and 𝗦𝗟𝗔𝗧𝗦 𝗦𝗟𝗢𝗪, the procedure is to select 𝗙𝗟𝗔𝗣 𝗟𝗩𝗥 𝟯, decelerate to the calculated 𝗩𝗔𝗣𝗽, and stabilize at 𝗖𝗢𝗡𝗙 𝟯 and 𝗩𝗔𝗣𝗽 before applying 𝗟/𝗚 𝗚𝗥𝗩𝗧𝗬 𝗘𝗫𝗧𝗡[cite: 22]. The sequencing is deliberate. Stabilizing the approach before gravity gear extension allows the elevators to settle at the trim reference position that will be memorized when the law degrades to 𝗗𝗜𝗥𝗘𝗖𝗧 𝗟𝗔𝗪[cite: 23]. Drop the gear early and the trim reference is set for an aircraft that is not yet at landing configuration[cite: 24].

How is landing distance calculated after an A320 dual hydraulic failure?

𝗟𝗗𝗚 𝗗𝗜𝗦𝗧 𝗣𝗥𝗢𝗖: 𝗔𝗣𝗣𝗟𝗬[cite: 26]. The 𝗤𝗥𝗛 and 𝗙𝗖𝗢𝗠 direct the crew to use the 𝗘𝗙𝗕 performance application for landing distance assessment in this configuration[cite: 26]. Generic multipliers are not the authorized method — the actual numbers depend on the integrated effects of 𝗖𝗢𝗡𝗙 𝟯, jammed flaps, accumulator-only braking with a 𝟭,𝟬𝟬𝟬 𝗽𝘀𝗶 brake pressure limit, no anti-skid, and the seven brake applications available[cite: 27]. The 𝗘𝗙𝗕 integrates these factors against runway condition and aircraft weight. A long, dry runway is preferred[cite: 28].

What are the go-around limitations on an A320 with HYD G+Y SYS LO PR?

The published go-around limits for this condition are 𝗠𝗔𝗫 𝗣𝗜𝗧𝗖𝗛 𝟭𝟱° and a 𝗧𝗢𝗚𝗔 𝘁𝗵𝗲𝗻 𝗠𝗖𝗧 thrust schedule[cite: 30]. The landing gear cannot be retracted, so fuel consumption increases significantly during any go-around and the aircraft remains in a high-drag configuration[cite: 31]. This is why the procedure emphasizes stabilizing the approach before gear extension and treating the first approach as the landing approach[cite: 32]. A second attempt is operationally expensive and aerodynamically degraded[cite: 33].

Is nose wheel steering available after an A320 dual hydraulic failure?

No[cite: 35]. Nose wheel steering is 𝗚𝗥𝗘𝗘𝗡-powered and inoperative for 𝗛𝗬𝗗 𝗚+𝗬 𝗦𝗬𝗦 𝗟𝗢 𝗣𝗥[cite: 35]. The aircraft cannot self-taxi off the runway after landing[cite: 36]. ATC should be advised early so ground assistance or a tow is arranged before touchdown[cite: 36]. During rollout, directional control is by rudder while rudder authority remains, then by differential braking within the 𝟭,𝟬𝟬𝟬 𝗽𝘀𝗶 accumulator pressure limit[cite: 37].

Are all spoilers lost in an A320 dual hydraulic failure?

No[cite: 39]. One spoiler per wing remains active[cite: 39]. 𝗦批𝗟𝗥 𝟭, 𝟮, 𝟰, and 𝟱 are inoperative; 𝗦𝗣𝗟𝗥 𝟯 is 𝗕𝗟𝗨Ｅ-powered and remains available[cite: 39, 40]. Roll authority is degraded — there is no aerodynamic ground braking on rollout — but the ailerons combined with the single remaining spoiler per wing preserve roll responsiveness on approach[cite: 40]. The common misconception that "all spoilers are lost" mistrains crews to expect ailerons-only roll control[cite: 41]. That is not the surviving configuration[cite: 42].