Beech B99 accident at Grottoes, Virginia, 23 Sept 1985

Accident narrative

On September 23, 1985, Henson Airlines Flight 1517, a Beech B99, crashed into the southwest face of Hall Mountain near Grottoes, Virginia, while on an instrument approach to the Shenandoah Valley Airport. The scheduled domestic passenger flight was operating in instrument meteorological conditions. Both crewmembers and all 12 passengers were fatally injured, and the airplane was demolished by impact forces and a postcrash fire.

### The flight

Flight 1517 originated at Baltimore-Washington International Airport with a destination of Shenandoah Valley Airport in Weyers Cave, Virginia.

The captain had 3,447 hours of total flight time, including 301 hours in the Beech B99. He had upgraded to captain the month before the accident. The first officer had 3,329 hours of total flight time, with 283 hours in multiengine airplanes and 119 hours in the Beech B99. She had been assigned as a first officer six weeks before the accident.

### The sequence of events

The flight was cleared for takeoff at 0922. Air traffic control handling was routine, and the flight was cleared for an instrument approach to Shenandoah Valley Airport at 0959. Radar service was terminated at 1003.

About 1005, the flightcrew made an in-range call to the Henson station agent, reporting the passenger count and requesting fuel. Shortly after, they contacted the airport UNICOM and received the 0945 weather observation, which reported an overcast ceiling at 1,000 feet and visibility of 2 miles in fog.

At 1011, radar recorded the airplane crossing the localizer for runway 4 eastbound on a magnetic track of about 075 degrees. The last recorded radar return was at 1011:55, showing the airplane at 2,700 feet.

At 1014:18, the radar controller asked the flight for its position. The captain replied, "...we're showin a little west of course the inbound course here," and added at 1014:25, "...we're turn inbound now." The captain then acknowledged an instruction to report passing the locator at the outer marker.

At 1015:55, the captain asked if the center controller showed the aircraft east of course. The controller advised that radar contact was lost. At 1017:49, the controller suggested a missed approach if the airplane was not established on the localizer course. There was no response.

The wreckage was located about 1842, approximately 6 miles east of the airport at an elevation of 2,400 feet.

### What the investigation found

The Board found no evidence of in-flight structural failure, fire, or malfunction of the airplane's flight controls or instruments. Damage to the trees and the wreckage indicated the airplane struck the trees in a wings-level, fuselage-level attitude with the landing gear and flaps retracted. Both engines were operating at impact, and the propellers were in low pitch.

The investigation examined the airplane's three VHF navigation radios. The No. 1 radio was found tuned to 110.5 MHz, and the No. 2 radio was tuned to either 109.5 MHz (the correct localizer frequency) or 110.5 MHz. The No. 3 radio, located on the first officer's panel, was severely damaged but could have been tuned to 110.5, 110.05, 115.5, or 115.05 MHz. The Board concluded that the frequencies found in the control heads were not necessarily those selected by the pilots, as impact forces were sufficient to move the tuning shafts.

The Board believed that the most credible explanation for the navigational error was that the flightcrew navigated using the 045-degree radial of the Montebello VOR instead of the Shenandoah ILS. A flight demonstration showed that the 045-degree radial of the Montebello VOR led almost directly to the accident site. The Board noted that several factors should have discouraged the crew from using the VOR radial, including an incorrect aural identification, a glideslope flag, and an automatic direction finder (ADF) needle indicating the airplane was east of course.

The investigation identified several operational and human performance elements that contributed to the accident. The Board noted that the first officer had limited multiengine and instrument flying experience, and both pilots were relatively inexperienced in their respective positions. The airline's Beech B99 fleet featured nonstandardized navigational radio systems, and the first officer's independent navigation radio lacked audio capability for positive facility identification.

Cockpit noise was also evaluated. The Beech B99 had high ambient noise levels and lacked a crew interphone system. The pilots wore noise-attenuating headsets, which the Board believed interfered with proper and timely crew coordination.

The Board also reviewed the pilots' training and personal lives. Henson Airlines trained pilots to proficiency without using a view-limiting device for instrument training, instead lowering the pilot's seat to restrict forward vision. Additionally, both pilots were experiencing stress-inducing life events. The captain was recently engaged and had an airline interview scheduled for the next day. The first officer had financial concerns and unresolved medical issues, and toxicological tests found a therapeutic dosage of a diet drug she took to stay awake.

Finally, the Board found that the Federal Aviation Administration's surveillance of the airline was inadequate. The principal operations inspector's time had been consumed by the introduction of a new airplane to the fleet, resulting in almost no surveillance of Beech B99 operations in the three months before the accident.

### Probable cause

The National Transportation Safety Board determined that the probable cause of this accident was "a navigational error by the flightcrew resulting from their use of the incorrect navigational facility and their failure to adequately monitor the flight instruments."

The Board determined that factors contributing to the flightcrew's errors were: "the nonstandardized navigational radio systems installed in the airline's Beech 99 fleet; intra-cockpit communications difficulties associated with high ambient noise levels in the airplane; inadequate training of the pilots by the airline; the first officer's limited multiengine and instrument flying experience; the pilots' limited experience in their positions in the Beech 99; and stress-inducing events in the lives of the pilots." The Board also found that "contributing to the accident was the inadequate surveillance of the airline by the Federal Aviation Administration which failed to detect the deficiencies which led to the accident."