A Harmless Prank

After the stop in Dallas, the airplane took off a little before dawn and climbed to its cruising altitude of 8,000 feet msl, or about 4,000 feet above ground level. Captain Charles Sisto was in the left seat, but after leveling off he relinquished it to Captain John Beck, who had come along to familiarize himself with the DC-4. In the right seat was Captain Melvin Logan, flying as copilot. Captain Sisto now took the jumpseat, which was behind and between the two pilots’ seats.

Almost two hours after takeoff, a little west of El Paso, Beck noticed that the airplane had begun to climb. He rolled in some nose-down trim, but the climb persisted. He rolled in more trim, and, to his surprise, the rate of climb increased. Puzzled by the failure of pitch trim to produce the expected result, he turned to Sisto and asked him whether the automatic pilot was on. Sisto replied that it was not. Beck then considered the possibility that the gust lock, which was actuated from inside the airplane, had inadvertently become engaged. He began to roll the trim back to its neutral position, but before he could do so, the airplane pitched violently downward.

Beck and Sisto, who did not have their seat belts fastened, were thrown to the cockpit ceiling. On their way up, one of them accidentally struck the prop controls, feathering both propellers on the left side of the airplane and the outboard one on the right. Logan, whose belt was fastened and held him in his seat, perceived that the airplane had performed a half outside loop and was now flying inverted a few hundred feet above the ground. He half-rolled it to the left—aided by the functioning number 3 engine—unfeathered the other propellers, turned around and headed for El Paso, where the airplane landed uneventfully 15 minutes later. Remarkably, while 30 of 49 passengers and five of the six crew received minor injuries from being thrown around, no one was seriously hurt.

In initial statements made the following day to the Civil Aeronautics Board, which investigated the bizarre incident (the National Transportation Safety Board did not yet exist), the three pilots said that the autopilot had been engaged just before the upset. CAB investigators accordingly examined the autopilot on the ground, and, finding nothing wrong with it, bravely took the airplane up for a test flight. No malfunction or evidence of demonic possession was found in the autopilot or any other part of the airplane.

A week later, the pilots, presumably having worked out what happened among themselves, withdrew their previous testimony. It now appeared that the autopilot had not been in use at all. What had happened was that Sisto, perhaps intending to test the alertness of Beck or maybe just because he was fun-loving, had silently engaged the elevator gust lock. After Beck asked him whether the autopilot was engaged, but before Beck had time to neutralize the trim, Sisto released the lock. The elevator trim tabs, still deflected upward, forced the elevators down, and the airplane tucked. The accidental feathering of the propellers, which removed thrust from three engines, was fortuitous—the CAB was of the opinion that if the engines had all continued to deliver cruising power, the airplane would certainly have struck the ground.

The mechanics of what happened are straight forward but maybe not obvious except in retrospect. The unexpected initial climb was probably a random effect of the engagement of the gust lock, which must have slightly changed the elevator incidence. When Beck trimmed the airplane nose down, the elevator trim tabs deflected upward. Normally, the tabs would push the elevators downward, but with the elevators locked, the tabs became ersatz elevators and pushed the entire tail down instead, causing the airplane to climb. Releasing the control lock restored the normal function of the tabs, which were now trimmed for a steep dive. It was perhaps thanks to the period of climbing before the upset, as well as to the accidentally feathered props, that the airplane avoided hitting the ground. Finally, the same powerful nose-down pitch trim that caused the bunt in the first place held the airplane’s nose up when it was inverted, and gave Logan time to assess the situation and see the way out of it.

The CAB’s report does not mention Beck pushing the controls forward to arrest the climb, but probably when he asked Sisto whether the autopilot was engaged it was because he had tried to apply a nose-down correction and found that he could not move the wheel. When Sisto said that the autopilot was not on, Beck’s thoughts turned next to the gust lock. We don’t know whether he visually checked the gust lock handle, but we do know that he realized that if the gust lock were engaged, he would have to neutralize the pitch trim before disengaging it.

Evidently, the same thought did not occur to Sisto.

This bizarre incident occurred before airplanes carried flight data recorders, and the reconstruction of the accident was based on the testimony of the pilots. The CAB commended Logan for “his immediate recognition of the situation and for taking proper corrective action so promptly.” Beck emerged blameless. However, the misadventure ended the airline career of Charles Sisto. In a decision handed down a year after the incident, the CAB found that he had “demonstrated a disregard for the principles of air safety [and] lacked the discretion and good judgment necessary for the holder of an airman certificate with an airline transport pilot or commercial rating...” Sisto’s commercial certificate was revoked, but he eventually regained his private one. My friend and fellow scribbler Peter Lert, who called my attention to this curious story, heard it from Sisto himself sometime in the 1970s, when Sisto had a hangar at Santa Paula in southern California.

It’s a rare Aftermath that ends without at least one fatality. I’m not sure what edifying lessons can be drawnfrom this story, but I thought it was too good to leave untold. And it does equip us with a bit of aviation trivia that may come in handy on some rainy afternoon in a hangar. Q: How much space does a DC-4 require for a diving outside loop? A: Less than 4,000 feet.

This article is based on the Civil Aeronautics Board’s report of the incident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.

This article was originally published in the April 2023, Issue 936 of  FLYING.