Lockheed L-188C accident at US, 18 Nov 1979

Accident narrative

On November 18, 1979, at 0456 mountain standard time, Transamerica Airlines Logair Flight 3N18, a Lockheed L-188C Electra, disintegrated in flight and crashed on an abandoned airport about 4 nautical miles south of Salt Lake City International Airport. The three crewmembers were killed, and the aircraft was destroyed. The flight had experienced a progressive electrical failure while climbing in night instrument meteorological conditions.

### The flight

Flight 3N18 was an instrument flight rules cargo flight from Hill Air Force Base in Ogden, Utah, to Nellis Air Force Base, Nevada. The aircraft carried 27,552 pounds of cargo. The crew consisted of Captain Marvin U. Dick, First Officer Harry H. Gardiner, and Second Officer Jack M. Johnston. All were properly certificated and qualified.

The local weather was estimated as a 2,500-foot broken ceiling and a 6,000-foot overcast, with 15 miles visibility. The Hill Air Force Base tower advised the crew of light rime icing from nine thousand feet to flight level 200.

### Sequence of events

The flight was cleared for takeoff at 0445. Shortly after liftoff, the crew contacted Salt Lake City departure control and was cleared to climb to flight level 200. At 0452:43, the flight reported leaving 11,000 feet, and the controller asked the crew to turn left to a heading of 160 degrees.

At 0453:34, the cockpit voice recorder captured the sounds of a power interruption. Two seconds later, the captain said, "lost everything." The captain and first officer discussed the loss of an electrical bus, and the first officer stated he did not have any heading reference at all. The captain indicated he also had no heading reference.

At 0454, the captain asked for a flashlight, which the first officer provided. At 0454:10, the first officer noted they had lost flight control hydraulic boost. The captain commanded, "go needle, ball, airspeed." The first officer transmitted to departure control that the aircraft had lost all electrical power.

The flight reported descending through 12,000 feet at 0454:43. Around the same time, the second officer made a statement that sounded like "...we've still got B," referring to an electrical bus. The controller advised the flight to maintain 11,000 feet for terrain clearance.

At 0455:05, the first officer told the captain, "no, you're in a right turn." The captain responded, "you help me, help me, help me fly the airplane." The first officer replied, "okay," and read out "300 on the heading." The controller then advised the flight to descend at the pilot's discretion and maintain 8,000 feet. The crew requested vectors toward visual flight rules weather.

At 0455:43, the captain said, "okay help me, I'm climbing." The controller offered to vector the flight north of Salt Lake. The crew's final transmission at 0455:58 was "Descending..." One second later, the cockpit voice recorder captured the sounds of the aircraft breaking apart. The Salt Lake City tower controller observed a glow in the sky, heard an explosion, and saw two fireballs descend out of the overcast.

### What the investigation found

The wreckage was scattered along a 1 1/2-mile path. The outboard wing sections and portions of the tail had separated in flight. The fuselage struck the ground inverted at a near 30-degree nosedown attitude. Examination of the engines and propellers disclosed no evidence of preimpact distress.

The investigation focused on the aircraft's electrical system, which utilized three engine-driven generators to power priority bus A, priority bus B, and an essential alternating current (a.c.) bus. The Board concluded that a definite electrical malfunction occurred at 0453:34, when power to the cockpit voice recorder was interrupted for about one second. Because the flight data recorder and voice recorder continued to function after this interruption, the Board concluded the essential a.c. bus remained powered, apparently by the No. 2 generator through priority bus B.

The Board concluded that priority bus A was locked out by a system malfunction. This failure rendered the first officer's horizon flight director, pictorial deviation indicator, and gyrosyn compass indicator inoperative, and disabled the integral lights in the pilots' flight instruments. However, the captain's horizon flight director, gyrosyn compass indicator, and turn-and-bank indicator remained operative. The captain's horizon flight director was recovered indicating an inverted, 30-degree nosedown attitude, closely matching the aircraft's impact attitude, which indicated it was functioning properly.

The Board believed that erratic behavior of the radar and VOR systems early in the flight, caused by a progressive voltage decay, probably created a state of mind that made it difficult for the crew to rely on their flight instruments. Following the lockout of priority bus A, the captain's operative instruments likely displayed warning flags related to their flight director and VOR functions. These displays, combined with the sudden loss of integral instrument lighting in night instrument meteorological conditions, probably caused the captain to believe his instruments were also inoperative or unreliable.

The Board concluded that the first officer was illuminating the captain's instruments with a flashlight and reading the heading from the captain's compass indicator. The captain obviously became spatially disoriented and lost control of the aircraft. Flight data recorder traces showed the aircraft descending at about 12,500 feet per minute with increasing airspeed and high aerodynamic forces just before the captain stated he was climbing. The aircraft's structural design loads and maximum airspeed were exceeded, causing it to break apart about 3,000 feet above the ground.

The aircraft was not equipped, nor was it required to be, with an independently powered standby attitude indicator. The Board believed the accident probably would have been avoided if one had been installed.

### Probable cause

The National Transportation Safety Board determined that the probable cause of this accident was "a progressive failure in the aircraft's electrical system leading to the disabling or erratic performance of some critical flight instruments and flight instrument lighting while the flight was operating in night instrument meteorological conditions. As a result of these conditions, the flightcrew could not resolve the instrumentation anomalies to determine proper aircraft attitude reference, and became disoriented and lost control of the aircraft. The crew's efforts to regain control of the aircraft imposed aerodynamic loads which exceeded design limits of the aircraft and caused it to break up in flight."