UA 232 – Sioux City Hydraulic Failure

Date of Incident: July 19, 1989

Location: Sioux Gateway Airport, Iowa, USA

🧭 What Happened

United Airlines Flight 232, a McDonnell Douglas DC-10, suffered a catastrophic failure of its tail-mounted engine at cruising altitude. The disintegration of the fan disk severed all three hydraulic systems, rendering the aircraft uncontrollable by conventional means. The crew used differential thrust to guide the aircraft to Sioux City, where it crash-landed. Despite the severity, 184 of the 296 onboard survived.

✈️ Aircraft Details

Flight Number: UA232 / UAL232

Aircraft Type: McDonnell Douglas DC-10-10

Registration: N1819U

Departure: Denver Stapleton (DEN) → Chicago O'Hare (ORD)

Destination: Philadelphia International (PHL)

Fatalities: 112

Survivors: 184

🔍 Key Factors

The No. 2 engine’s fan disk fractured due to a hidden metallurgical defect. Debris severed hydraulic lines routed through the tail, eliminating control of ailerons, elevators, and rudder. The DC-10 was not designed to be flyable without hydraulics. The crew improvised control using asymmetric thrust from the wing-mounted engines.

📆 Timeline of Events

🎙️ Cockpit Voice & Flight Data

“We’re gonna have to do this visually.” — Captain Haynes
“I can’t control the airplane.” — First Officer Records

The CVR captured crew coordination, throttle manipulation, and emergency communications. The FDR showed erratic pitch and roll oscillations, with no hydraulic pressure in any system. The aircraft was flown manually using engine thrust alone.

📄 Read the Full CVR Transcript

⚙️ Aircraft Systems & Failures

🛡️ Aftermath and Reforms

📋 Sources