[Federal Register Volume 64, Number 136 (Friday, July 16, 1999)]
[Proposed Rules]
[Pages 38362-38365]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-17537]
[[Page 38362]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-152-AD]
RIN 2120-AA64
Airworthiness Directives; Bombardier Model DHC-7 and DHC-8 Series
Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Bombardier Model DHC-7 and
DHC-8 series airplanes. This proposal would require revising the
Airplane Flight Manual (AFM) to include requirements for activation of
the airframe pneumatic deicing boots. This proposal is prompted by
reports of inflight incidents and an accident that occurred in icing
conditions where the airframe pneumatic deicing boots were not
activated. The actions specified by the proposed AD are intended to
ensure that flightcrews activate the pneumatic wing and tail deicing
boots at the first signs of ice accumulation. This action will prevent
reduced controllability of the aircraft due to adverse aerodynamic
effects of ice adhering to the airplane prior to the first deicing
cycle.
DATES: Comments must be received by August 16, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-152-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT: Norman Martenson, Aerospace Engineer,
Manager, International Branch, ANM-116, FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056;
telephone (425) 227-2110; fax (425) 227-1149.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed rule by submitting such written data, views, or arguments as
they may desire. Communications shall identify the Rules Docket number
and be submitted in triplicate to the address specified above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals contained in this notice may be changed in
light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed rule. All
comments submitted will be available, both before and after the closing
date for comments, in the Rules Docket for examination by interested
persons. A report summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 99-NM-152-AD.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules
Docket 99-NM-152-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056.
Discussion
On January 9, 1997, an Empresa Brazileira de Aeronautica, S.A.
(EMBRAER) Model EMB-120RT series airplane was involved in an
uncommanded roll excursion and consequent rapid descent that resulted
in an accident near Monroe, Michigan. The post-accident investigation
conducted by the National Transportation Safety Board (NTSB) concluded
that the airplane had accumulated a thin, rough layer of ice on its
lifting surfaces. That accumulation of ice, in combination with the
slowing of the airplane to an airspeed inappropriate for the icing
conditions in which the airplane was flying, resulted in loss of
control that was not corrected before the airplane impacted the ground.
The NTSB also concluded that the flight crew did not activate the wing
and tail pneumatic deicing boots. An NTSB recommendation related to
this accident requested that the FAA mandate that pneumatic deicing
boots be turned on as soon as the airplane enters icing conditions.
The FAA has reviewed the icing-related incident history of certain
airplanes, and has determined that icing incidents may have occurred
because pneumatic deicing boots were not activated at the first
evidence of ice accretion. As a result, the handling qualities or the
controllability of the airplane may have been reduced due to the
accumulated ice. That factor was present in the accident discussed
previously and, as such, constitutes an unsafe condition.
Request for Information
On October 1, 1998, the FAA sent letters to certain manufacturers
of airplanes certified in accordance with part 25 of the Federal
Aviation Regulations (14 CFR part 25). The letters requested certain
icing system design information and operational procedures applicable
to their airplanes concerning flight during icing conditions. The
letters also requested that manufacturers provide data showing that the
aircraft has safe operating characteristics with ice accreted on the
protected surfaces (boots). The manufacturers were asked to provide
data using the following assumptions: The most adverse ice accumulation
possible during operation in the icing envelope specified in part 25,
Appendix C of the Federal Aviation Regulations (14 CFR part 25), and
that recommended procedures for deicing boot operation were used.
Additionally, the manufacturers were asked to provide information
related to operation of the autopilot during icing conditions, and for
information related to appropriate operating speeds for icing
operations.
No information received, as a result of that request, has caused
the FAA to reconsider the previous conclusion that an unsafe condition
may exist.
Public Meeting
Subsequent to the collection of those design and operational data,
the FAA held an international conference on ``Inflight Operations in
Icing Conditions'', in Washington, DC, on February 2-4, 1999. The
purpose of the conference was to discuss the status of the FAA Icing
Plan and other related efforts. Additionally, the conference provided a
forum for representatives of industry to express their viewpoints on
current information related to activation of deicing boots, minimum
airspeeds, autopilot operation in icing conditions, flightcrew
information needs, and flightcrew training. Certain information
presented at that meeting is discussed in this proposed rule in the
following section.
[[Page 38363]]
Delayed Activation of Pneumatic Deicing Boots
In accordance with manufacturer instructions and FAA-approved
airplane flight manual (AFM) procedures, the flightcrews of most
airplanes equipped with pneumatic deicing boots delay the initial
activation of the boots until a certain quantity of ice has accumulated
on the protected surfaces (boots). Some crews routinely wait for \1/4\
to \1/2\ inch of ice to accumulate, and at least one airplane type is
routinely flown with up to 1\1/2\ inches of ice on the protected
surfaces before the initial activation of the deicing boots.
Ice Bridging
In the past, concern about ``ice bridging'' on early pneumatic
deicing boot designs resulted in the common practice of delaying
activation of ice protection. Ice bridging of pneumatic deicing boots
occurred when a thin layer of ice is sufficiently plastic to deform to
the shape of the inflated deicing boot tube without being fractured and
shed during the ensuing tube deflation. As the deformed ice hardens and
accretes additional ice, the deicing boot becomes ineffective in
shedding the ``sheath'' of ice. However, ice accumulation resulting
from delayed activation may pose an unsafe condition due to the
resultant adverse aerodynamic effects on the airplane's performance or
handling qualities.
In November 1997, the FAA and the National Aeronautics and Space
Administration (NASA) co-sponsored an international workshop on
aircraft deicing boot ice bridging. The objective of the workshop was
to provide an open forum for investigating the existence of deicing
boot bridging and other concerns related to activating ice protection
systems at the initial detection of inflight icing. Sixty-seven
representatives from airframe and deicing boot manufacturers, various
airlines, the pilot community, NASA, the National Transportation Safety
Board, non-US civil aviation authorities, and the FAA participated. At
the workshop no evidence was presented to substantiate that aircraft
with modern deicing boot designs experience ice bridging. The general
consensus of the workshop participants was that ice bridging is not a
problem for modern pneumatic deicing boot designs due to the use of
higher air supply pressures, faster boot inflation and deflation
cycles, and smaller boot chambers. Icing wind tunnel and flight testing
of these newer design features with automatic cycling have demonstrated
successful shedding of ice when activated at the onset of ice
accretion, with ice not shed on the initial deicing boot cycle
continuing to increase in thickness and being shed during subsequent
cycles.
During the previously discussed November 1997 international
workshop, the inability of flightcrews to accurately gauge wing and
control surfaces ice accretion thickness before activating the deicing
boots was recognized. Also, increased airplane drag resulting from ice
accretion was recognized as a potential contributing cause of
inadvertent airspeed loss that characterized most in-flight icing
related accidents and incidents. Two airframe manufacturers, whose
products comprise a substantial percentage of the turbopropeller
transport fleet, reported that, because of these concerns they
recommend activating the automatic airframe deicing system at first
onset of airframe icing. Those manufacturers have received no reports
of deicing boot ice bridging events for these airplanes.
The FAA considers that ice accumulation on protected surfaces due
to delayed boot activation constitutes a potential safety concern.
However, the FAA recognizes that not all airplanes may be equipped with
``modern'' deicing boots (as that term is used in this NPRM). The FAA
specifically invites the submission of comments and other data
regarding the effects of this proposed AD on airplanes equipped with
older pneumatic deicing boots, including arguments for the retention of
existing activation delays for these older-style deicing boots.
Residual Ice
During the February conference, the attendees agreed that the
airplane is at risk while the airplane is accreting ice, and that the
airplane must be adequately protected to ensure that no adverse
handling and performance characteristics develop. An additional concern
discussed at the conference was the possibility that early activation
of the ice protection system might degrade the ice shedding
effectiveness of the deicing boots, resulting in increased residual
ice, i.e., there would be more ice fragments remaining on the deicing
boots than would exist if a more substantial quantity of ice was
allowed to form before the first ice shedding cycle. However, the FAA
does not concur. No data has been provided that shows that the presence
of residual ice following an earlier activation of the deicing boots is
more hazardous than delaying cycling of the boots until the ice
accretes to a larger, specific thickness. In fact, testing in icing
conditions has shown that residual ice remaining on the boots after the
initial boot cycle is removed during subsequent cycles.
As reported during the November 1997 international workshop,
manufacturers of a substantial percentage of the turbopropeller
transport fleet have reported satisfactory in-flight icing operations
of their products with recommended procedures to activate operation of
the deicing boots in the automatic mode at the onset of airframe icing.
Therefore, the FAA considers that the activation of pneumatic wing
and tail deicing boots at the first signs of ice accumulation is
warranted. The FAA specifically invites the submission of data to
substantiate that operating the deicing boots at the first sign of ice
accretions is more hazardous than delaying boot activation until a
specific thickness of ice has accumulated.
Other Considerations
The FAA recognizes that there may be some phases of flight during
which use of the deicing boots may be inappropriate. For example, a
deicing boot inflation cycle that begins immediately before or during
the landing flare or the takeoff rotation may cause unexpected loss of
lift or other adverse aerodynamic events. This proposed AD explicitly
does not supersede procedures in the AFM that specify not using deicing
boots for certain phases of flight (e.g., during take-off, final
approach, and landing).
The FAA specifically invites the submission of comments and other
data regarding adverse effects that may occur during specific phases of
flight, including takeoff, final approach, or landing. Any recommended
speed restrictions or other operational procedures that would be
necessary in order to mitigate any adverse aerodynamic effects of
deicing boot inflation during critical phases of flight should be fully
explained and documented.
FAA's Determinations
The FAA is aware that, based on previous procedures provided to
flightcrews of many airplanes equipped with deicing boots, an
historical precedent has been set that permits waiting to activate the
deicing equipment. In light of this information and based on reports
received, the FAA considers that certain procedures should be included
in the Limitations Section of the AFM for Bombardier Model DHC-7 and
DHC-8 series airplanes to require immediate activation of the ice
protection systems when any ice accumulation is detected on the
airplane.
[[Page 38364]]
This proposed action is one of a number of proposed ADs being
issued on airplanes that have been determined to be subject to the same
identified unsafe conditions. Additionally, certain other airplanes are
also being reviewed by the Small Airplane Directorate to determine
specifically which airplanes may be subject to the identified unsafe
condition. Currently proposed AD's for other airplanes that are
equipped with pneumatic deicing boots address the following airplanes:
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Airplane models Docket No.
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Cessna Aircraft Company, Models 500, 550, 99-NM-136-AD.
and 560 Series Airplanes.
Sabreliner Corporation, Models 40, 60, 70, 99-NM-137-AD.
and 80 Series Airplanes.
Gulfstream Aerospace, Model G-159 Series 99-NM-138-AD.
Airplanes.
McDonnell Douglas, Models DC-3 and DC-4 99-NM-139-AD.
Series Airplanes.
Mitsubishi Heavy Industries, Model YS-11 and 99-NM-140-AD.
YS-11A Series Airplanes.
Frakes Aviation, Model G-73 (Mallard) and G- 99-NM-141-AD.
73T Series Airplanes.
Lockheed, Models L-14 and L-18 Series 99-NM-142-AD.
Airplanes.
Fairchild, Models F27 and FH227 Series 99-NM-143-AD.
Airplanes.
Aerospatiale, Models ATR-42/ATR-72 Series... 99-NM-144-AD.
Jetstream, Model BAe ATP Airplanes.......... 99-NM-145-AD.
Jetstream, Model 4101 Airplanes............. 99-NM-146-AD.
British Aerospace, Model HS 748 Series 99-NM-147-AD.
Airplanes.
Saab, Model SF340A/SAAB 340B/SAAB 2000 99-NM-148-AD.
Series Airplanes.
CASA, Model C-212/CN-235 Series Airplanes... 99-NM-149-AD.
Dornier, Model 328-100 Series Airplanes..... 99-NM-150-AD.
Lockheed, Model 1329-23 and 1329-25 99-NM-151-AD.
(Lockheed Jetstar) Series Airplanes
de Havilland, Model DHC-7/DHC-8 Series 99-NM-152-AD.
Airplanes.
Fokker, Model F27 Mark 100/200/300/400/500/ 99-NM-153-AD.
600/700/050 Series Airplanes.
Short Brothers, Model SD3-30/SD3-60/SD3- 99-NM-154-AD.
SHERPA Airplanes.
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Explanation of Requirements of Proposed Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would require revising the Limitations Section of the AFM
to include requirements for activation of pneumatic deicing boots at
the first indication of ice accumulation on the airplane.
Cost Impact
The FAA estimates that 183 airplanes of U.S. registry would be
affected by this proposed AD.
The FAA estimates that it would take approximately 1 work hour per
airplane to accomplish the proposed AFM revisions, at the average labor
rate of $60 per work hour. Based on these figures, the cost impact of
the proposed AD on U.S. operators is estimated to be $10,980, or $60
per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the proposed requirements
of this AD action, and that no operator would accomplish those actions
in the future if this AD were not adopted.
Regulatory Impact
The regulations proposed herein would not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, will not have a significant economic impact,
positive or negative, on a substantial number of small entities under
the criteria of the Regulatory Flexibility Act. A copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting the Rules
Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation
[[Page 38365]]
Administration proposes to amend part 39 of the Federal Aviation
Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Bombardier, Inc. (Formerly de Havilland, Inc.): Docket 99-NM-152-AD.
Applicability: Model DHC-7 and DHC-8 series airplanes equipped
with pneumatic deicing boots, certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To ensure that flightcrews activate the wing and tail pneumatic
deicing boots at the first signs of ice accumulation on the
airplane, accomplish the following:
(a) Within 10 days after the effective date of this AD: Revise
the Limitations Section of the FAA-approved Airplane Flight Manual
(AFM) to include the following requirements for activation of the
ice protection systems. This may be accomplished by inserting a copy
of this AD in the AFM.
`` Except for certain phases of flight where the AFM
specifies that deicing boots should not be used (e.g., take-off,
final approach, and landing), compliance with the following is
required.
Wing and Tail Leading Edge Pneumatic Deicing Boot
System, if installed, must be activated:
--At the first sign of ice formation anywhere on the aircraft, or
upon annunciation from an ice detector system, whichever occurs
first; and
--The system must either be continued to be operated in the
automatic cycling mode, if available; or the system must be manually
cycled as needed to minimize the ice accretions on the airframe.
The wing and tail leading edge pneumatic deicing boot
system may be deactivated only after leaving icing conditions and
after the airplane is determined to be clear of ice.''
(b) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Manager, International Branch, ANM-
116, FAA, Transport Airplane Directorate. The request shall be
forwarded through an appropriate FAA Operations Inspector, who may
add comments and then send it to the Manager, International Branch,
ANM-116 ACO.
Note 1: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the International Branch, ANM-116 ACO.
(c) Special flight permits may be issued in accordance with
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR
21.197 and 21.199) to operate the airplane to a location where the
requirements of this AD can be accomplished.
Issued in Renton, Washington, on June 30, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-17537 Filed 7-15-99; 8:45 am]
BILLING CODE 4910-13-P