FOR IMMEDIATE RELEASE: April 2, 1996 SB-10B/6405B
NTSB URGES HIGHER STANDARDS AFTER SPECIAL HELICOPTER PROBE
(Washington, DC) -- Calling for permanent special pilot training and
tougher operating standards for helicopters with sensitive flight controls,
the National Transportation Safety Board reported that the cause of a series
of Robinson Helicopter R22 accidents "most likely stems" from
big and sudden pilot movements of the aircraft's highly-responsive flight
controls. The NTSB said it found no mechanical failure or other defect
behind the crashes.
In a special investigation report, the Safety Board focused mainly on
accidents resulting from the loss of main rotor control and covered 31
crashes of the two-seat R22 and three accidents involving the R44, a larger
version. Common to these accidents was the loss of control from rotor blades
striking the fuselage or tailboom, resulting in in-flight breakups that
killed a total of 58 persons since 1981.
The Safety Board previously had issued numerous recommendations to address
the problem, prompting the Federal Aviation Administration (FAA) to implement
several operational changes. These primarily were designed to ensure better
training and proficiency for pilots and flight instructors and restricted
R22 flights in certain adverse conditions.
There have been no loss of main rotor control R22 accidents in the U.S.
since the changes were implemented more than a year ago, according to NTSB.
The aircraft has had a history of such mishaps much greater than other
helicopters.
The Safety Board said that because the R22 is more responsive to cyclic
control inputs than other helicopters used by students or low-time pilots
special training requirements are needed. The cyclic controls the tilt
of the main rotor system and directs the course of flight.
"Flight instructors probably do not have sufficient time to react
to R22 students' large, abrupt flight control inputs," said the Board.
"Therefore, they must guard the cyclic closely to prevent such inputs."
Computer modeling has been done at the Georgia Institute of Technology
to better understand the R22. The Safety Board said the work "suggests
that large, abrupt cyclic control inputs may result in mast bumping or
blade angles-of-attacks greater than the stall angle; however, the mathematical
model was not developed sufficiently to demonstrate that flight control
inputs would lead to loss of control of the main rotor. "The Board
said it hoped more work would be done in this effort.
During its special investigation, the NTSB said it found that FAA staff
made several internal recommendations related to the R22 accidents and
the special certification reviews conducted by that agency.
"Based on documents provided by the FAA, under (NTSB) subpoena,
the Safety Board could not conclusively determine what action, if any in
some cases, the FAA initiated as a result of these internal recommendations,
but it concluded that little action resulted from the(m)...," said
the Board's report.
The Safety Board recommended that FAA make permanent the special training
and operational requirements that were put in place for the R22, and in
certifying future lightweight highly-responsive helicopters, that similar
measures be considered.
The NTSB also called for more research into lightweight helicopter behavior.
Such a step should be undertaken by FAA and NASA to "create a national
resource tool that would aid in the certification of future helicopter
models, especially those that are lightweight and highly responsive,"
said the Board.
The Safety Board's complete printed report, PB96-917003, will be available
from the national Technical Information Service, 5285 Port Royal Road,
Springfield, VA. 22161. The telephone number is (703) 487-4650.
Media contact: Mike Benson 202 314-6100
NTSB Home | Contact Us | Search | About the NTSB | Policies and Notices | Related Sites