Page 38 - World Airnews Magazine May 2020 Edition

TECHNICAL

DAMAGE FROM

TURBULENCE, UPSETS CAN

EVADE INSPECTIONS

By Patrick Veillette (Ph.D)

had moved east of the departure airport, and the TOD and destina-
tion airport remained clear of the turbulence box.

evere turbulence is an ongoing reality and problem. Ac- The flight release also contained a single pilot report of severe turbu-

Scording to “Turbulence Related Accidents & Incidents” by lence from a Boeing 737 at FL 240, within the defined area of turbu-

Donald Eick, senior meteorologist in the NTSB’s Office of Aviation lence. Prior to departure, but after the flight release was signed by the

Safety, airline pilots report 5,500 severe or greater turbulence pilot, the release was updated again, this time with SIGMET Whiskey 10.
encounters annually - that’s 15 per day - and they are tough on The turbulence box moved farther east to cover the TOD and

crews, their passengers and the airframe. In addition, flight control destination airport. Nearing his destination, the pilot descended
system failures, upsets and pilot-induced manoeuvres also can into the turbulence box.

produce excessive stress. The airplane was not equipped with an aircraft communications

These inflight events should be followed by a logbook entry by addressing and reporting system (ACARS). Rather, weather updates
the captain and a proper inspection by a maintenance technician. were accomplished by direct radio contact between the dispatcher

Nevertheless, the NTSB has discovered the resulting structural and pilots, or by the pilots accessing FAA facilities while en route.

aircraft damage can be substantial and yet evade post-flight visual Although the operator had about 100 flights operating in the

inspections by pilots and maintenance technicians, thus allowing turbulence box, none were cancelled due to forecast turbulence,

unairworthy aircraft to fly again. or reported to have encountered severe turbulence.

On Nov. 17, 2002, a Canadair CL-600---2B19 operated by Comair The pilot turned on the seat belt sign, asked the flight attendant
from Atlanta to Washington, encountered severe turbulence during to be seated, and made an announcement for the passengers to re-

its descent near Rockville, Virginia. About three hours before main seated as they were within 30 min. of the destination airport.

takeoff, the dispatcher approved the flight release, which contained While descending through 17,800 ft., the flight encountered

SIGMET Whiskey 8 for occasional severe turbulence from 14,000 ft. heavy turbulence. Fortunately, there were no injuries to the crew
to FL 280. The turbulence box overlaid the departure airport and or passengers. Upon landing, the jet was visually inspected for

planned en route climb to altitude; however, the top of descent damage in accordance with the Canadair Regional Jet (CRJ) Aircraft

(TOD) and destination airport were clear of the turbulence. Maintenance Manual (AMM) and returned to service.

When the pilot later printed the flight release, SIGMET Whiskey One of the certification criteria for transport aircraft dealing with

8 had been replaced with SIGMET Whiskey 9. The turbulence box structural integrity is 14 CFR 25.301(a), which states, “The structure
World Airnews | May 2020
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