1966 Air New Zealand DC-8 crash

1966 Air New Zealand DC-8 crash

The accident aircraft involved during its delivery flight in 1965
Accident
Date	4 July 1966
Summary	Crashed due to reverse thrust deployment during takeoff
Site	Auckland International Airport, Auckland, New Zealand 37°00′36″S 174°47′29″E
Aircraft
Aircraft type	Douglas DC-8-52
Operator	Air New Zealand
Registration	ZK-NZB
Flight origin	Auckland International Airport
Destination	Auckland International Airport
Crew	5
Fatalities	2
Injuries	3
Survivors	3

On 4 July 1966, an Air New Zealand Douglas DC-8-52 crashed on takeoff from Auckland International Airport on a training flight, killing 2 out of the 5 crew members on board. The crash was the first fatal crash in the history of Air New Zealand and the only crash to date of a commercial jetliner in New Zealand. The investigation concluded that during the captain's attempt to simulate an engine failure, the captain accidentally deployed the thrust reverser on the number four engine. This resulted in the aircraft's speed falling below the minimum control speed, which resulted in the aircraft become uncontrollable and the eventual crash.

Aircraft

The aircraft involved in the accident was a one-year-old Douglas DC-8-52, registration ZK-NZB and manufacturer's serial number 45751. The aircraft had four Pratt and Whitney JT3D-3B turbofan engines. The aircraft had a total of 2,275 airframe hours, with the last maintenance check occurring on 1 July 1966.

Crew

There were five crew members on board the flight. In command of the flight was 46-year-old Captain Donal McLachlan, who had 1,788 flight hours, 497 of which on the DC-8. He was serving as an instructor for 29-year-old trainee First Officer Brian Ruffell. He had 4,200 hours of flying time, although only 21 of which were on the DC-8. The flight engineer of the flight was 33-year-old Gordon Tonkin, who 4,250 flight hours. The other two crew members of the flight were Captain Bernard Wyatt and First Officer Kenneth Sawyer, who had no official flying duties. First Officer Ruffel was sitting in the left seat in the cockpit while Captain McLachlan was sitting in the right seat.

Background

An overview of the thrust levers in the DC-8 cockpit, with the spoiler disarm extension rod on the side of the number four thrust lever

The aircraft was conducting a training flight, with Captain McLachlan serving as an instructor for First Officer Ruffell. The captain would be training the first officer on touch-and-go landings and simulated engine failures after V₁ speed. V₁ speed is the maximum airspeed where a flight crew can safely preform a rejected takeoff. On this flight, soon after reaching V₁ speed, Captain McLachlan would pull back the power on an engine thrust lever, and First Officer Ruffel would have to identify the simulated failed engine, use the rudder to keep the aircraft flying straight, and keep the airspeed increasing.

Captain McLachlan had been involved in a previous flight training incident involving the accident aircraft. During that incident flight, he was training a trainee first officer on engine failures during touch-and-go landings. When the captain tried to pull back the thrust lever for the number four engine, instead of using his whole hand, he used only his thumb and index finger on the knob of the lever. He pulled back the thrust lever of the engine with such speed that the inertia caused the thrust brakes to enter the reverse detent. The aircraft rolled sharply to the right, and the first officer, who was the pilot flying, was unable to maintain directional control even when applying full left rudder. Captain McLachlan managed to stow the reverser and conduct a three-engine climb.

The investigation believed that this switched McLachlan's method of simulating an engine failure on the number four engine. Instead of using the aforementioned technique to reduce power on the engine, he used the spoiler disarm extension, a rod attached to the number four thrust lever. The intended use of the rod is to retract the spoilers when the thrust levers were advanced to high power. It is not intended to be used as a handle.

Accident

The flight crew started up the aircraft engines at 15:50 NZST and four minutes later, air traffic control cleared ZK-NZB to the holding position at the threshold of runway 23. At 15:59, the aircraft was cleared for takeoff from the runway. Fourteen seconds after the start of the takeoff roll, the aircraft reached V₁ speed. At this moment, Captain McLachlan used the spoiler disarm extension to reduce power on the number four engine. However, this caused the engine thrust reversers to activate. First Officer Ruffell was initially able to correct yaw that the asymmetrical thrust that the engine produced. Three seconds later, the DC-8 reached V_R speed, the speed where the aircraft under normal conditions can safely start rotation. The first officer pulled back on the control column, but the aircraft rotated much steeper than usual, and he felt significant drag on the right side of the aircraft. He attempted to counteract it with full left rudder, but this did not stop the yawing motion.

The airspeed peaked at 124.5 kn (230.6 km/h; 143.3 mph) 20 seconds after the beginning of the takeoff roll. The aircraft started to roll to the right while just 100 ft (30 m) above the ground. Three and a half seconds later, the right wingtip impacted the ground near the edge of the runway while the aircraft was rolled nearly 50° to the right. The rest of the DC-8 soon impacted the ground, causing the number one, three, and four engines to be torn off of the wings. The nose section of the aircraft separated from the rest of the fuselage and became inverted. Leaking fuel tanks set both parts of the aircraft on fire. Inside the cockpit, all crew members survived the impact but were seriously injured. By the time rescue services reached them, Captain McLachlan and Flight Engineer Tonkin were dead. First Officer Ruffell, Captain Wyatt, and First Officer Sawyer were all brought to hospital.

Cause

The crash was due to reverse thrust applied during a simulated failure of no.4 engine on takeoff. The situation occurred when very rapid rearward movement of the power lever caused the associated thrust brake lever to enter the reverse idle position. After take-off, minimum control speed (M_CS) required to overcome this abnormal state of thrust imbalance was never achieved. The condition was recognised by the pilots and rectified but there was not enough time nor altitude available to allow the aircraft to recover.