Turbulence and Ice Lead To Serious Control Loss
OK... this flight did NOT sound like a good time. But the double
combo of increasing turbulence and rime ice led up to a very
serious upset that ultimately culminated in structural damage to
the airframe. This could have gone a lot worse and the flight crew
apparently had their hands full getting this situation under
control.
NTSB Identification: ERA11LA344
14 CFR Part 91: General Aviation
Accident occurred Wednesday, June 15, 2011 in Gray, TN
Aircraft: BEECH A100, registration: N15L
Injuries: 2 Uninjured.
This is preliminary information, subject to change, and may
contain errors. Any errors in this report will be corrected when
the final report has been completed.
On June 15, 2011, about 1405 eastern daylight time, a Beech
A100, N15L, operated by Dynamic Avlease Inc., was substantially
damaged when it experienced an in-flight upset, while in cruise
flight near Gray, Tennessee. The two certificated commercial pilots
were not injured. Instrument meteorological conditions (IMC)
prevailed and an instrument flight rules flight plan had been filed
for the flight that departed Bridgewater Air Park (VBW),
Bridgewater, Virginia, destined for Mid-Continent Airport (ICT),
Wichita, Kansas. The positioning flight was conducted under the
provisions of 14 Code of Federal Regulations Part 91.
According to initial information obtained from the flight crew
and the Federal Aviation Administration (FAA), the airplane was
flying in smooth IMC conditions at Flight Level 200 (20,000 feet
msl), with an area of "moderate to heavy to extreme" precipitation
located about 30 miles to the northwest. As the airplane approached
20 miles from the weather, it began to experience moderate
turbulence and "several seconds of rime ice" on the windscreen. The
pilot flying deviated course 40-degrees to the south. Turbulence
increased further for about 10 seconds, and the airplane then
entered an uncommanded left roll and dive. The autopilot disengaged
and the pilot's electrically driven attitude indicator tumbled. The
flight crew reduced the engine power levers to idle and were able
to recover utilizing the copilot's vacuum driven attitude
indicator. The airplane was returned to straight and level flight
at an altitude of 8,000 feet; however, "flight control instability"
persisted. The flight crew subsequently diverted to Tri-Cities
Regional Airport (TRI), Blountville, Tennessee, and landed without
further incident.
Subsequent examination of the airplane by an FAA inspector
revealed that the outboard one-third of the left elevator separated
in flight, and the outboard right elevator was deformed downward.
In addition, the horizontal stabilizer bulkhead frame was fractured
and the aft portion of the airframe sustained several areas of
deformation.