House Aviation Subcommittee Hears Testimony On Aircraft Icing
By Mike Mitchell
February 28, 2010
- NTSB Chairman Deborah Hersman on Wednesday gave testimony before the
House Aviation Subcommittee, Committee on Transportation and
Infrastructure, discussed the dangers of aircraft flying in icing
conditions and highlighted longstanding Safety Board recommendations
that have yet to be adopted by the Federal Aviation Administration to
address the issue.
Reducing the dangers of flying in icing conditions has been on the NTSB's Most Wanted List of Transportation Safety Improvements since 1997. Last week, the NTSB voted to keep the issue area, along with its four open recommendations to the FAA, on the 2010 Most Wanted List with a "red" classification. The red classification indicates an unacceptable response by the FAA.
"Although the NTSB relies on others to implement these recommendations, we have worked to educate the pilot community about some of the hazards associated with icing conditions through our Safety Alerts," Hersman said.
In 1981, the NTSB published a report titled "Aircraft Icing Avoidance and Protection" and recommended the FAA review icing certification criteria. The special study followed a series of icing-related accidents where aircraft operating in icing conditions and the varying consequences that ice accretion had on different types of aircraft raised concern,
In the 1990s
the NTSB re-examined the issue of airframe structural icing and
concluded that the icing certification process continues to be
The Board also became concerned about airplanes that fly in supercooled large droplet conditions and that used pneumatic boots to deice the aircraft in flight. In the last decade, the Board has investigated more than 50 accidents involving aircraft icing, resulting in over 200 fatalities and it continues to investigate accidents where icing is a factor.
In the last few
years, the FAA has addressed some of the recommendations related to
icing by issuing a number of final and proposed regulations.
However, not all of the NTSB's recommendations on icing have been
See Below For Full
Text of Chairman Hersman's Testimony
Mr. Petri, and Members of the Subcommittee: Thank you for the
opportunity to join the discussion today regarding the safety of
aircraft in icing conditions. This is an issue of great concern to the
National Transportation Safety Board (NTSB), and we appreciate the
opportunity to offer our viewpoint.
The NTSB is an
independent Federal agency chartered by Congress with investigating
every civil aviation accident in the
inception in 1990, the Most Wanted List represents a group of safety
recommendations selected for intensive follow-up.
The recommendations are combined into issue areas, such as
in-flight structural aircraft icing.
These recommendations are selected because they will benefit or
enhance the safety of the national transportation system; have a high
level of public visibility or interest; or will benefit from this
special form of encouragement and heightened attention.
From 1998 to 2007,
the NTSB has investigated fifty Part 121 and 135, and 214 General
Aviation accidents involving airplane icing, resulting in 202
fatalities. The accidents have involved aircraft, powerplants, aircraft
systems (excluding carbureter icing) and/or runway and surface
conditions. During that
same period of ti me, the NTSB has issued 48 recommendations addressing
various safety issues that, if addressed, would improve aviation safety.
While the NTSB relies on others to implement our recommendations,
we have worked to educate the pilot community about some of the hazards
associated with icing conditions through Safety Alerts (Ground Aircraft
Icing – December 2006; De-ice Boot Activation – December 2008).
tables represent the range of investigations and recommendations that
the NTSB has addressed between 1998 and 2007.
However, my testimony today will focus on the areas addressed in
our Most Wanted List.
The NTSB has long
been concerned about aircraft operating in icing conditions.
In September 1981, the NTSB published a report entitled “Aircraft
Icing Avoidance and Protection,” which recommended that the FAA review
the icing certification criteria. The report was the result of a special
study following a series of icing-related accidents in which the NTSB
identified concerns about aircraft operations in icing conditions and
the varying consequences that ice accretions had on different aircraft
As a result of two
accidents during the 1990s, the NTSB became concerned about airplanes
that fly in supercooled large droplet (SLD) conditions, and that use
pneumatic boots to deice the aircraft in flight. These aircraft are
typically, but not exclusively, turbo-prop aircraft that use pneumatic
boots and fly at altitudes where they are more likely to encounter SLD
icing accident occurred in 1994 in
of operating an airplane in icing conditions without first having
thoroughly demonstrated adequate handling/controllability
characteristics in those conditions are sufficiently severe that they
warrant a thorough certification test program, including application of
revised standards to airplanes currently certificated for flight in
On January 9,
1997, a Comair Embraer EMB-120 departed controlled flight and crashed in
icing conditions over
In both the
Roselawn and Monroe accidents, the pilots were using the autopilot
before the icing-induced upset began.
Because the pilots were not manually flying the aircraft, they
were not aware that the autopilot was having increasing difficulty
maintaining stable flight until the autopilot suddenly disconnected, and
the airplane entered an uncontrollable flight regime.
recommendations stemming from the Roselawn and the Monroe accidents
called on the FAA to use current research on freezing rain and SLD to
revise the way aircraft are designed and approved for flight in icing
conditions; to apply revised icing requirements to currently
certificated aircraft; and to require the pilots of airplanes with
pneumatic deice boots to activate the boots as soon as the airplane
enters icing conditions.
The FAA referred
this work to an Aviation Rulemaking Advisory Committee (ARAC) more than
10 years ago. Six years
later, the ARAC approved a concept to revise the icing design
requirements for new airplanes.
In December 2005, the ARAC completed its final report and
recommended appropriate revisions to the design and operational
requirements for flight in icing conditions.
In the more than four years since that report, the FAA has yet to
issue a notice of proposed rulemaking (NPRM) to require consideration of
more realistic icing conditions.
In the last few years the FAA has issued a number of final and proposed rules; some of those actions have been responsive to NTSB recommendations. On August 3, 2007, the FAA issued a final rule that revised the certification standards for the handling and controllability characteristics of newly designed Part 25 aircraft in icing conditions; however the rule did not include revisions to reflect SLD conditions, a particularly dangerous flight environment that the NTSB asked the FAA to address.
On August 3, 2009,
the FAA issued a final rule regarding the activation of ice protection
systems on newly designed Part 25 aircraft certified for flight in icing
conditions. On November 23,
2009, the FAA issued an NPRM regarding activation of the ice protection
system on aircraft operated under Part 121.
The NTSB has commented on the NPRM which does not address other
categories of aircraft such as business aircraft and Part 135 air-taxi
operations or those aircraft weighing over 60,000 pounds, effectively
exempting some aircraft types operating in regional airline operations
such as the Bombardier DHC-8, Q-400.
In addition, the NTSB recommendation that prompted this NPRM
resulted from the
While the FAA’s
rules have addressed some of the recommendations relating to deice boot
operations, not all of the NTSB recommendations have been fully
addressed. In particular,
the NTSB has recommended that the FAA use a full range of icing
conditions, including SLD, for icing certification testing.
This would include freezing rain, freezing drizzle, and freezing
NTSB continues to investigate accidents and incidents in which in-flight
icing has been a factor.
Each of the following incidents or accidents reinforces the need for the
FAA to address SLD in icing certification:
On March 19, 2001, an Embraer EMB-120, operated by Comair
Airlines, Inc., as flight 5054, encountered icing conditions while in
cruise flight at 17,000 feet and departed controlled flight, descending
to an altitude of about 10,000 feet. The pilots recovered control of the
airplane and diverted to
On February 16, 2005, a Cessna Citation 560, operated by
Martinair, Inc., for Circuit City Stores, Inc., crashed about 4 nautical
miles east of
In January 2006, an American Eagle flight 3008, a Saab-Scania AB
SF340B+, departed from San Luis County Regional Airport (SBP),
Finally, the NTSB
is investigating an accident that occurred in January 2009, in
This investigation is ongoing, but it suggests, as did the accidents in the early 1990s, that flightcrews are encountering icing conditions for which their aircraft are not suitably designed to handle, and for which their training is inadequate. Although the FAA received a proposal from the ARAC for an expanded icing envelope to include SLD in 2005, the publication of an NPRM has been delayed numerous times, and the FAA now expects to issue an NPRM in June of this year.
While there has
been progress on the part of the FAA, the NTSB is concerned that the
process for incorporating these recommended changes is slow.
In March 2009, 13 years after the NTSB issued the recommendations
regarding expansion of icing conditions considered when certifying an
aircraft, the FAA decided to form an advisory committee for Part 23
aircraft. Part 23 airplanes
tend to be smaller aircraft such as are used in business jet and air
taxi operations. As of our
most recent update at the end of 2009, this advisory committee had not
yet been formed or met. At
the current rate, we would not expect these regulatory changes to be in
place until almost 20 years after the Roselawn accident.
Although not an
in-flight aircraft icing recommendation, the Safety Board has been
concerned with the broader issue of excursions due to runway
landing distance assessments, which assure an adequate safety margin for
landing, is another important issue included on the Safety Board’s Most
Wanted List. The
recommendation asks the FAA to require operators to incorporate a 15
percent safety margin for landing on contaminated runways and was issued
as a result of the NTSB’s investigation of a fatal runway excursion
involving Southwest Airlines at
When the NTSB issues a safety recommendation with an “urgent” designation, it expects that the action can be completed within one year after the recommendation is issued. However, in this case, the FAA has only issued guidance and encouraged operators to conduct a landing distance assessment. The FAA has not made this a requirement and recent investigations have revealed that some of the FAA’s inspectors are not aware the guidance exists. Since the guidance was issued, the Safety Board has investigated several accidents involving runway overruns on wet or contaminated runways, including Shuttle America flight 6448 in Cleveland; Pinnacle Airlines flight 4712 in Traverse City, Michigan; a Hawker Beechcraft Part 135 flight in Owatonna, Minnesota; and, we are supporting the Jamaican authorities as they investigate the recent American Airlines runway excursion that occurred on December 22, 2009, in Kingston.
Mr. Chairman, this concludes my testimony. I look forward to answering any questions that you and the members of the Subcommittee may have.
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