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VFR into IMC leads to in-flight breakupVFR into IMC leads to in-flight breakup

(NYC06FA215)(NYC06FA215)

Air Safety InstituteVFR-only pilots who succumb to spatial disorientation during encounters with instrument conditions often fall prey to the so-called “graveyard spiral”—a descending turn that only gets tighter and steeper as the pilot pulls back on the yoke in a misguided attempt to stop the descent. In this scenario, ground impact is typically what destroys the airplane. But unusual attitudes can put tremendous strain on an airframe, and a panicked pilot lost in the soup can push an aircraft literally to the breaking point.

On Sept. 4, 2006, the noninstrument-rated pilot of a Cessna 150 became spatially disoriented when he flew into instrument meteorological conditions (IMC) near Penhook, Va. The aircraft entered an unusual attitude so extreme that the wings were torn from the airplane in flight. The pilot and his passenger were killed.

The flight left Smith Mountain Lake Airport in Moneta, Va., about 11:20 a.m., destined for Florence Regional Airport in Florence, S.C. Marginal VFR conditions prevailed at the time of departure. The pilot did not obtain an official weather briefing from either flight service or DUATS, although a relative later reported that the pilot said he checked the weather and that it “looked okay above 2,500 [feet].” No flight plan was filed.

Shortly after takeoff, the pilot contacted Roanoke approach control and requested VFR flight following. Seven minutes later, he asked the controller for information regarding cloud tops and ceiling height. At 11:31 a.m., the pilot asked ATC for a radar vector. When queried about the request, the pilot responded, “We’re kinda lost in some fog here.” The controller asked him to state his present heading, to which he replied, “I can’t tell—I think we’re upside down.” The controller instructed the pilot to turn right, and 18 seconds later told the pilot to stop the turn. During this time the airplane had actually completed a left turn and its altitude varied between 4,500 and 4,700 feet.

About 10 seconds later, at 11:32 a.m., the pilot announced, “We can’t see! We can’t see! We can’t see!” followed by an unintelligible transmission. The controller advised the pilot to stay calm and not to climb or descend. No further transmissions were received from the pilot, and radar contact was lost shortly thereafter.

A witness near the accident site reported that he heard “a loud pop.” When he looked up, he saw the airplane’s fuselage crash into nearby woods, then observed the wings “floating” down to the ground. Another witness said she heard the airplane, stepped outside her home, and saw the wings “twirling in the air.” Examination of the wreckage revealed that both wings had folded upward near the roots before separating from the fuselage. Fracture surfaces and control cable breaks were consistent with in-flight overload.

Weather conditions at reporting stations near the accident site included visibility of two to three miles in rain and mist and overcast ceilings as low as 700 feet agl. Airmets for IFR conditions and mountain obscuration had been issued about one and a half hours before the accident airplane departed.

The NTSB determined that the accident resulted from the pilot’s failure to maintain aircraft control, which led to G forces in excess of the airplane’s design stress limits and, eventually, an in-flight breakup. Contributing factors were the pilot’s continued VFR flight into IMC and his spatial disorientation.

When it comes to accident statistics, low ceilings and visibilities rank as the greatest weather hazard to the VFR pilot. Thunderstorms, icing, high winds, turbulence—none of these more dramatic, higher-profile threats comes close to killing as many pilots as simple, condensed water vapor.

The reason is simple: Most noninstrument-rated pilots have only a few hours of hood time in their logbooks, and these skills quickly atrophy after the private checkride. Caught in IMC and deprived of visual references, the VFR pilot begins to rely on the body’s motion- and gravity-sensing organs—a system that is prone to illusion. In the battle of trust between instinct and instruments, the gauges typically lose.

The best way to avoid a VFR-into-IMC accident is to get an instrument rating and keep it current. Short of that, the key is understanding and respecting the weather. Always get a thorough preflight briefing, especially if conditions along the route are questionable. And remember that water vapor is fickle: Ceilings can drop quickly, fog can materialize rapidly, and the clear air between cloud layers can close in with little warning. Give yourself plenty of wiggle room, have a Plan B set to go, and don’t hesitate to divert at the first sign of trouble.