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OCR for page 19
Type Certification
and Rule Making
As stated in the introduction, the processes by which
the FAA seeks to assure the inherent safety or airwor-
thiness of aircraft are type certification and rule
making. Type certification, handled primarily in an FAA
regional office, involves assuring that the manufac-
turer's new design for a particular type of aircraft
complies with the statute and all applicable rules and
standards. Rule making, conducted at the agency's head-
quarters in Washington, D.C., involves establishing the
regulations and technical standards that must be met by
the manufacturers and airlines in the course of design-
ing, producing, operating, and maintaining the aircraft.
Within each regional office, the group that reviews
and approves each new aircraft design is the Type Certi-
fication Board. Usually chaired by the director of the
office's engineering and manufacturing section, the "Type
Board" is composed of the senior managers for various
technical specialties. The board functions as a manage-
ment or steering group for all certification projects
within the region and acts as a reviewer and arbiter of
major technical issues. It provides a point for appeal
by the applicants and serves as an overall advisory group
to its chairman, who issues the Type Certificate. The
day-to-day interactions with the applicant are handled
by an assigned project manager, supported by staff
members of a project engineering team.
A typical certification project for a new type of
airplane involves a process of interaction and iteration
19
OCR for page 20
IMPROVING AIRCRAFT SAFETY/20
between the FAA regional office and the manufacturer
over a number of years. It begins when the FAA receives
an application from the manufacturer for type and
production certificates. The process is characterized by
a progression of design and testing activities conducted
by the applicant and reviews for compliance by the FAA
project team, punctuated by a small number of meetings
--perhaps four to six--of the Type Board at critical
decision-making points. Once the FAA project team has
familiarized itself with the application, the board holds
a preliminary meeting, attended by the FAA team and its
applicant counterparts, to make an initial evaluation
and to identify the pertinent design certification cri-
teria, including the regulations, standards, and criteria
that the applicant must meet, and the means by which the
applicant must demonstrate compliance.
An interim meeting is held two to three years after
the initial meeting to review the general progress and
to settle any additional requirements. In the meantime,
the applicant may undertake steps that rely on informal,
interim decisions concerning Special Conditions that may
be imposed. It does this because manufacturers are com-
mitted far in advance to aircraft delivery dates. Not
to do so would run the risk of delaying the project to
await the final approval.
The penultimate milestone is a preflight meeting of
the Type Board at which, in addition to reviewing the
overall progress of the project and identifying items
that remain to be resolved, the board issues a Type
Inspection Authorization. This document authorizes the
FAA pilots to begin test flights to determine if the
work has been accomplished. At the final meeting, in
confirmation that all requirements have been met, the
Type Certificate is issued.
FAA Personnel and Organization
Rule making and type certification call for engineers
and scientists--airworthiness professionals--of high
technical competence. The organizational and technical
qualities that are desirable for rule-making personnel
are similar to those required for making the critical
governmental judgments in applying the rules and stan-
dards to the certification process for a new type design.
OCR for page 21
21/Type Certification and Rule Making
The assurance of acceptable airworthiness rules and
standards must proceed from a knowledgeable FAA staff of
sufficient capability and depth to provide leadership
and, when necessary, to challenge the industry. Simi-
larly, the type certification system presumes a high
level of quality on the part of the government certifi-
cation staff in assessing the work of the manufacturer
in designing a new aircraft. While much smaller in
numbers than the manufacturer's staff, the FAA staff
must be capable of holding the company to appropriate
standards of design and proof, of going beyond the let-
ter of the standard to provide interpretation and to ask
the right questions, and, with the aid of company-
employed Designated Engineering Representatives, of
painstakingly checking the company's work to assure
compliance.
The attributes of technical expertise, assertive
judgment and independent initiative within the FAA are
critical to its success. Although there are many moti-
vated and dedicated members of the FAA's airworthiness
engineering staffs, based on its discussions with FAA
and industry engineers involved in certification and
other processes, the committee found a greater technical
competence and state of the art currency on the part of
personnel in the aircraft industry than in the FAA.
In particular, the committee found that this
situation existed with respect to type certification.
While this difference cannot reasonably be expected to
be otherwise at the detailed design level, in order for
the FAA to be effective in making significant judgments,
there is a need for more qualified, critical, and
analytical oversight by the senior FAA staff than is
presently exercised.
The present quality of aircraft designs is satisfac-
tory largely because of the proficiency of the companies
and the designee system. Although FAA staff members have
raised apt and constructive questions, their contribution
stems largely from the process itself. Systematic educa-
tion and briefing by company engineers of the FAA staff
provide a useful checklist against which the applicant
can gain increased assurance that it has not overlooked
important matters. While this role is by no means a
trivial contribution to the design and ultimate airwor-
thiness of the aircraft, it is not a sufficient one.
OCR for page 22
IMPROVING AI RCRAFT SAFETY/2 2
At one time, the FAA staff included senior recognized
experts and authoritative sources in the field of aero-
nautics. One of the earliest books on aircraft flutter,
for instance, was written
by FAA employees Scanlan and
Rosenbaum.' The agency's ability to perform its air-
worthiness mission credibly, and to command the respect
. . . . . . . .
aviation community, depends on its regaining such
recognizable expertise.
The present situation with regard to the quality of
FAA personnel can be traced in part to the current
organizational structure which, as described below, does
not foster an environment that attracts the best people.
It is also a function of the history of the aviation
industry. When aviation was a newer field of endeavor,
opportunities were greater and challenges broader. As
aircraft become more complex, those who oversee them
become specialists in particular areas. Many government
engineers and inspectors grew with the industry and de-
veloped seasoned judgment from involvement in a variety
of new designs and a rapidly growing enterprise. As
these people now begin to retire and are succeeded by
another generation, the newer FAA staff expect to enjoy
fewer fundamental challenges and opportunities for inno-
vation than were experienced by their predecessors.
Although aviation continues to present many challenges,
this problem is endemic to the FAA's present age and
that of many other established regulatory agencies.
A factor contributing to the lack of initiative by
FAA staff, both engineers and inspectors, is their ex-
pressed concern that if they attempt to go beyond the
precise letter of the regulation in overseeing the
industry they will not be supported by their supervisors
or by the Washington headquarters staff. Yet in making
judgments about the safety of aircraft, some interpreta-
tion is necessary.
The current FAA organizational structure, which
allocates type certification activities for the various
categories of aircraft among several regional offices,
results in a superficial level of technical oversight.
The structure accounts, in part at least, for frag-
menting the work of engineering specialists among many
different functions, inconsistent interpretations of
regulations from one regional office to another, and a
lack of communication among personnel in the regional
and headquarters offices on matters of common interest
OCR for page 23
23/Type Certification and Rule Making
and experience. It also contributes to the agency's
evident difficulty in attracting a sufficiently capable
corps of engineering experts and specialists.
In the Western and Northwest Regional Offices, where
certification of new domestic transport aircraft is con-
centrated, the work assignments of the engineering staffs
are not limited to the certification of new aircraft
types. The amount of time devoted to other functions
varies according to specialties and the phase of design
and test work in which the transport manufacturer is
engaged. The two regions reported that their personnel
devote, on the average, 60 to 75 percent of their time
to such "other" related activities as the certification
of modifications to existing jet transports, to business
jets, and, perhaps primarily, to the review of service
difficulty reports, service bulletins, and other kinds
of in-service surveillance and remedial action. The
regional engineers are also occupied by a variety of
administrative tasks. Accordingly, they are stretched
beyond their capacities of both expertise and time by
bulges in the workload caused by new type certification,
supplemental type certification, or special assignments.
Problems due in part to the regional structure are
demonstrated also by inconsistencies in the application
of standards between the Western and Northwest Regional
Offices. For example, while one region proposes to apply
to one manufacturer, retroactively, the amendment to the
rules relating to "accelerate-stop distances," (the min-
imum allowable runway lengths for an airplane to accel-
erate and stop safely, depending on its gross weight,
speed, prevailing weather and runway conditions) the
other office chose not to do so with other manufacturers
during approximately the same period.*
An example of inadequate exchange of knowledge
between regions is the fact that nine months after the
Chicago accident, as this committee was informed, the
engineering staff of the Northwest Regional Office had
*According to FAA personnel, Boeing, in the Northwest
Region, is resisting the accelerate-stop rule because it
claims that the 757 therefore will be at some competitive
disadvantage when compared to the DC-9-80. Douglas, in
the Western Region, is resisting the same rule because
it claims that the DC-9-80 will be at a competitive
disadvantage to the 737.
OCR for page 24
IMPROVI NG A I RCRAFT SAFETY/ 2 4
received no formal briefings on the relevant technical
issues by representatives of the companies, by the
Western Region's type certification team for the DC-10,
or by the investigators of the accident.
The committee observed an especially important
problem of the FAA's attenuated organizational structure:
the pool of engineering talent is so shallow that many
senior positions have remained vacant for several months.
The Western Regional Office, whose airworthiness juris-
diction extends to Douglas, Lockheed, and a number of
airlines, which is in the process of certificating the
DC-9-80 and has just finished the certification of the
L-1011-500, provides the most dramatic example. The
office has operated for nearly a year with many vacant
positions, including those of regional director, deputy
director, and chief
engineer would serve
Certification Board.
engineer. If on board, the chief
as chairman of the regional Type
addition to organizational structure, the
committee identified a number of other factors that may
contribute to the FAA's present inadequate level of
technical currency and competence:
· Inadequate and ambiguous direction, supervision,
.
.
and support ot stats, resulting in confusion
about priorities, reluctance to assert govern-
mental prerogatives, and low morale.
Cumbersome Civil Service and personnnel regula-
tions and artificial career barriers that have,
for instance, blocked adequate advancement and
recognition of nonsupervisory technical
specialists.
Difficulties in attracting and hiring new grad-
uate and experienced engineers, particularly in
the Los Angeles region where living costs are
unusually high.
Lack of a stimulating atmosphere and peer asso-
ciation, which is essential for a-thriving
technical organization.
Lack of resources and incentives for continuing
education of technical personnel as well as a
systemwide failure to provide adequate oppor-
tunities for essential training in new areas of
aviation technology.
Competition in the allocating of new positions
from operational components of the agency, such
as air traffic control.
.
OCR for page 25
25/Type Certification and Rule Making
While the functions of rule making and type certifi-
cation are similar and call for equivalent expertise and
judgment, they are not congruent with the function of
day-to-day reviews to assure compliance with established
standards. Rule making and type certification require
personnel of high technical competence, able to address
the right questions about new technological features,
including those for which guidelines have yet to be
established. No less vital, but decidedly different,
are the technical audit and surveillance functions which
require personnel generally familiar with the state of
the art and with production and maintenance techniques
and procedures, rather than with evolving technologies.
The administrator has recognized and taken steps
recently to deal with some of these concerns. In October
1979 he announced the intention to recruit a number of
"national resource specialists" in such technical dis-
ciplines as aeroelasticity, advanced materials, special
manufacturing processes, and airline maintenance tech-
niques.8 In April 1980, he advised our committee that
he was exploring the merits of selecting either the
Western or Northwest Regional Office as a "lead region"
to coordinate type certification activities for transport
aircraft. The "lead region" concept is already being
employed for such other aspects of FAA certification
responsibility as engines and helicopters.
The committee's recommendation goes even further.
In the committee's view, the availability of outstand-
ingly qualified airworthiness specialists is the sine
qua non of the FAA's airworthiness activities, and spe-
cialists of high calibre are not being attracted to the
current organization. The committee, therefore, re~om-
mends that the FAA establish a oentraZ engineering
organization, staffed with teohnioaZ personnel of the
highest competence, responsible for type oertifioation-
ond portioipation in rule making.
Located in an appropriate environment, possibly
adjacent to a government center of aeronautical research
and under the leadership of a-recognized authority in
aeronautical engineering, the proposed central engineer-
ing organization would be charged, ultimately, with the
following tasks: (i) the accomplishment of rule making
in relation to airworthiness matters, including the
interpretation of existing regulations and the identifi-
cation of related research needs; (ii) the reponsibility
OCR for page 26
IMPROVING AIRCRAFT SAFETY/2 6
for the key governmental decisions affecting design phi-
losophy and criteria involved in the type certification
of new aircraft and Supplemental Type Certificates, thus
assuming the functions of the Type Certification Boards
but not replacing the regional offices' project teams
that work, on a day-to-day basis, with the applicants
and the designees; and (iii) other related matters call-
ing for combining specialized and expert technical
knowledge with experienced judgment.
Members of the centralized organization would thus
be available as needed to all FAA offices throughout the
country, and would have the advantages of the mutual
reinforcement and common experiences gained from working
on many of the same types of problems as they arise from
rule making and certification activities. By regular
and frequent participation in design reviews and similar
functions, the team members would be continuously in-
formed about new technologies and other innovations.
They would be required to maintain a high level of tech-
nical skill. By continuous interaction with several
companies and associations, these airworthiness spec-
ialists would be able to function as an inter-industry
forum. While taking care to safeguard proprietary
information, the specialists could work as a team to
transfer from one type certification experience to
another the safety principles learned.
Once it is fully organized, the central organization
should comprise one-half to three-quarters of the FAA's
present complement of 318 aerospace engineers and 50
flight test pilots, and take responsibility for most of
the airworthiness engineering functions related to rule
making and aircraft design. A comparatively small num-
ber of engineers would remain in the regional offices
for day-to-day operations, to provide sign-offs and spot-
checks of the work of the type certificate applicants,
and to continue to oversee the remaining important
regional activities involving the certification and
surveillance of production, maintenance, continuing air-
worthiness, and responses to service difficulties. These
functions are best served from regional offices close to
the production and maintenance facilities. The functions
and location of the present staff would be changed under
the proposed plan, though no significant increase in the
number of positions is expected.
OCR for page 27
27/Type Certification and Rule Making
This reorganization cannot be accomplished all at
once. Initially, a cadre of 20 to 30 specialists should
be put in place to undertake the rule-making functions
and to assume the more limited responsibilities of the
Type Certification Boards. A five-to-seven-year
transition period would probably be required to reach
the ultimate goals of the proposed reorganization.
An improved and centralized engineering organization
is, in the committee's judgment, a prerequisite to up-
grading the quality of the FAA staff. The agency needs
to devise a means for attracting more experienced spe-
cialists than it presently has--a difficulty the commit-
tee recognizes is neither unique to the FAA nor easily
remedied in any government agency. Even working within
the constraints of the Civil Service System, however,
the FAA should be able to find the relatively small
number of experienced specialists required in private
industry, other federal agencies, and universities.
Certainly, the FAA would have to pursue a vigorous
recruiting campaign to attract the engineers and scien-
tists best suited to the central engineering organiza-
tion; and the challenges and rewards of such an organi-
zation would have to be made sufficiently attractive to
induce experienced professionals to make career changes
to become airworthiness professionals for the FAA.
The possibility of building and nurturing a technical
organization of high competence and esprit de corps by
centralizing technical functions has ample precedent in
The early National Advisory Committee for
government.
Aeronautics (NACA) and the Department of Defense's
weapons systems programs (e.g., the nuclear-powered
submarine, the SAGE network, and the ballistic missile
program) all stimulated the enthusiasm of the engineering
and scientific communities and attracted highly qualified
experts into government service to manage and implement
the efforts. Less visible examples of continuing acti-
vities that also attract highly motivated and capable
people include the Air Force's Materials Laboratory, its
Arnold Engineering Development Center, and NASA's
numerous specialized programs in aerodynamics, materials
and structures, avionics, propulsion, aircraft operating
problems, and flight tests carried out at a number of
facilities throughout the country.
These programs confirm the committee's judgment that
some of the United States' best engineering talent can
OCR for page 28
IMPROVING AIRCRAFT SAFETY/28
and should be attracted into the FAA's airworthiness
organization. To do that, the organization needs:
· Recognition that aviation safety provides an
important and challenging assignment.
Outstanding professional leadership that will
attract good engineers seeking positions under
experts in their respective fields.
Substantive responsibility and influence over
project elements.
Association with colleagues of high qualifica-
tions to provide a stimulating internal atmos-
phere.
Opportunities for career advancement that reward
merit and expertise as well as supervisory
responsibilities.
A stimulating environment that provides oppor-
tunities for associations with nearby universi-
ties and research establishments.
Opportunities for further study and professional
growth.
With regard to the last point, it is important to
note that, while individuals with a science or technology
orientation need to be exposed frequently to the state
of the art and emerging technological possibilities, it
is not necessary or desirable for the FAA itself to
manage such recurrent educational programs. There are
litany people oucs~ae One ~ AA who can teach new technolo-
gies as well as those who want to learn about them. It
is presumed that such programs could be arranged to meet
the needs of the FAA and of others at the same time.
Organized and structured continuing education is not
the only means by which the technological currency of
FAA personnel can be maintained. For example, the FAA
might consider a rotation or exchange program for its
personnel to spend Perhaps a year or more attached to
either public or private, in the
United States or abroad, at such places as NASA, Air
Force laboratories, research establishments, manufac-
turers, and universities.
.
an ~ _ ~ ~ _ ~ ~ a_ ~ _ _ . . ~ ~ ~ % ~1
other organizations,
on the resources devoted
An indispensable part of such a program is a suffi-
ciency of travel and other funds to support it. To skimp
_~ to building and maintaining a
requisite level of FAA staff competence places the sys-
tem's efficient operation in jeopardy over the long run
and threatens the agency's mandate to provide "the
highest degree of safety" in flight.
OCR for page 29
29/Type Certification and Rule Making
The collection of the FAA's engineering talent into
a single, coordinated unit should resolve many of the
problems of the current regional office structure, in-
cluding too close alliance with any one manufacturer,
and should result in a well-trained and technically qual-
ified staff that can provide improved interaction with
the manufacturers and their Designated Engineering Rep-
resentatives (DER). It should also eliminate many
inconsistencies in interpretation and application of
regulations.
It is the committee's view that this revised organi-
zational structure for airworthiness engineering, coupled
with a recommendation to improve the type certification
process (described later in the report) will result in a
significant improvement in the quality of airworthiness
certification and the overall effectiveness of the FAA.
Designated Engineering Representatives
About 370 FAA engineers are occupied with the certi-
fication of aircraft of all types. Half of these are in
the two regions with responsibility for Boeing, Douglas,
and Lockheed. The FAA regional project engineering and
flight test team certificating a new transport consists
of 20 to 30 professionals, most of whom also perform
other duties.
By contrast with the number of FAA engineers, Boeing
estimates it will concentrate about 4,000 engineers on
its new 767 transport at the peak of its design effort.
As a measure of the volume of work to be performed and
reviewed, Lockheed has reckoned that, in the course of
certificating a new wide-body aircraft, it would submit
approximately 300,000 engineering drawings and changes,
2,000 engineering reports, and 200 vendor reports. In
addition, it would subject the airplane to about 80 major
ground tests and 1,600 flight test hours. Throughout
this period, it would send some 1,500 letters to the
FAA.9
FAA engineers cannot review each of the thousands of
drawings, calculations, reports, and tests; yet the
agency must be certain that the design for a new airplane
meets all the regulatory requirements. The certifica-
tion process thus depends not only on a review of high
OCR for page 38
IMPROVING AIRCRAFT SAFETY/3 8
What is lacking is initiative--a systematic means
for determining where new rules are needed, the ranking
of priorities, and the development of the necessary
technical bases, where absent, for rule making. In light
of these findings, the committee recommends that the FAA
take more initiative in identifying the need for new
razes and in establishing objectives, priorities, peons,
and sokeduZes for rule making and that it sponsor onnuaZ
ruZe-making review conferences to support this activity.
To provide the means for problem identification, the
FAA should reinstate annual government-industry airwor-
thiness reviews. Such reviews were convened by the Civil
Aeronautics Board before rule-making functions were
transferred to the FAA in 1959, and were eminently suc-
ce~sful. Under that system, for example, the rules
necessary for certificating the initial fleet of jet
aircraft were developed in a timely manner, enabling the
United States to assume quickly a leading position in
commercial jet aviation.
The FAA attempted to revive this activity in 1974
with its all-embracing Airworthiness Review, the first
in a planned biennial series. However, the bulk and
comprehensive nature of the review, and the failure to
limit its agenda, swamped the capability of the FAA to
deal with the many recommendations. As a result, many
of the recommendations still await action. Examples
include:
or life limits on, Type Certificates;14 changes in
accelerate and stop distances;15 concern over regula-
tions dealing with failure analysis and numerical prob-
abilities;16 and such "key design elements" as "com-
partment fire protection, emergency exits, seats and
shoulder harnesses".17
Discussions with former FAA officials, and with in-
dustry personnel who participated in past reviews, have
convinced the committee that this process is a good one,
provided that the review is well organized, the agenda
is planned in advance, and the FAA follows through in a
, _
,
the desirability of requiring revalidation of,
~,
businesslike way. The same procedures should be used
for identifying the need for new standards, for discus-
sing their significance, and for determining the state
of the art necessary to write the rule.
The process for planning and setting priorities,
once the need for a new or updated rule has been iden-
tified, should be managed and carried out by the FAA
OCR for page 39
39/Type Certification and Rule Making
staff. Probably it was at this stage that the 1974 Air-
worthiness Review failed. From discussions at the re-
view, from additional industry and public comments, and
from its own knowledge, FAA management and technical
staff should be able to determine a priority ranking for
its rule-making activity.
From such a ranking, it should be an easy matter to
develop a plan and schedule for rule making--in effect,
a calendar--in considerable detail for the following
year, and in lesser detail for the succeeding five years.
The calendar should take into account the available re-
sources, the need to obtain or develop the underlying
technology base, and the administrative process of writ-
ing, reviewing, and publishing the rule itself. The
calendar should also leave sufficient room, on a planned
basis, for reactive rule making--the requirement
quickly to a failure, an accident, or an unanticipated
technological need.
Generally, by the time a technology is advanced to
the point where it can be considered for incorporation
into an aircraft, the research and development necessary
to complete a rule should be capable of being scheduled.
In other words, the research generally is not of such an
advanced nature that its outcome is completely unknown
or its impact unforeseeable.
The research and development in support of FAA rule-
making activity can be carried out for the most part by
other government agencies (e.g., NASA and the Air Force),
by universities, and by private industry. The committee
has reviewed the existing relationship between the FAA
and NASA, and has found that, while the mechanisms for
coordination have been established, they are not being
used effectively.
Given NASA's statutory responsibility for aeronau-
tical research,18, the FAA should request that agency
to strengthen those research programs that lay the basi
for future rule making. A formal interagency agreement
between NASA and FAA could be established through which
FAA submits requirements to NASA in accordance with FAA
developed priorities and plans. NASA could perform the
necessary research and development on a predetermined
time scale. Such formal agreements should not take the
place of the many ongoing technical meetings and discus-
sions, but rather should reflect the outcome of these
discussions in a way that the FAA can incorporate in its
planning process.
to react
OCR for page 40
IMPROVING AIRCRAFT SAFETY/4 0
NASA is not the only possible source for research to
meet the FAA's rule-making needs. The Air Force, for
example, has done a great deal of research directly ap-
plicable to airworthiness matters. If other public or
private resources can assist the FAA with its research
needs, the FAA should enlist their aid.
The recommended central engineering organization
would play a significant role in this and all other
aspects of the rule-making process. If this organization
were to be located in proximity to an existing research
center, the coordination required for technology devel-
opment might be greatly facilitated.
The administrative process for rule making, as
recently modified by the FAA with its project team con-
cept, appears to be improving--although it is still too
early to tell just how much. As an additional task, the
FAA should develop a systematic approach to updating the
entire body of Federal Aviation Regulations. While
scheduled rule making and annual conferences can be
expected to address new standards reflecting advancements
in knowledge and new design practices, the systematic up-
dating of the regulations should result in revising or
deleting rules and criteria that have become obsolete.
Even if a small fraction of the regulations--perhaps 10
percent--were redone each year, such action would fulfill
within a decade the need that has been evident for at
least the same period. This task being never finished,
the FAA should perpetuate both the annual review and
updating of the regulations.
Flight After Failure--A Specific Rule
While the purpose of this study has been to evaluate
the procedures by which the FAA and industry together
assure airworthiness, the committee has been mindful
throughout its deliberations of the fact that the acid
test of a process lies in the substance it produces, not
in its organizational elegance. The substance of rule-
making and type certification procedures is thus properly
measured by the technical adequacy of the adopted stan-
dards or regulations and the quality of the judgments
and decisions reached in applying the standards to the
design of a new aircraft.
OCR for page 41
41/Type Certification and Rule Making
It is in the nature of every complex technological
system that all possible risks--even mechanical ones--
cannot be anticipated and prevented by the design. Most
safety standards have evolved from the experience of
previous errors and accidents. Airplanes built in ac-
cordance with current standards are therefore designed
essentially to avoid the kinds of problems that have
occurred in the past and to tolerate operational abuses
deemed likely to occur. The high safety performance of
the modern jet transport provides assurance that the
current standards, which address the risks we now recog-
nize, are sound.
The designer seeks to anticipate and defend against
likely malfunctions and hazards that could defeat the
component being designed. However, many of the fatal
accidents that have occurred with airplanes manufactured
by companies visited by the committee have involved rare
and improbable combinations of mishaps, aspects of which
were outside the "design environment" of the components
in question, such as maintenance-induced damage, unde-
fined weather hazards, and damage sustained outside the
operating regimes. To comply with current FAA require-
ments, the designer of a new aircraft may establish that
structural components that are critical to safety comply
with the rules by either of two kinds of analyses. One
involves the concept of "safe-life," which means that a
structural component or assembly must be designed to
retain its strength and integrity throughout its useful
life. Landing gears, propeller blades, and engine fan
blades are examples of safe-life parts.
Whenever appropriate, structures may also be designed
to satisfy the concept of "fail-safe." Here, safety is
assured through the provision of redundancy. This means
that the designer must show, through a variety of
analyses of possible failure modes, that if the fail-
safe part is crippled, another redundant or backup part
is available to do its job sufficiently, at least to
permit a safe landing. For instance, a typical fuselage
Panel is designed with doubler strips that stop cracks
while the additional members of the
panel pick up the loads until the cracks can be detected
and repaired, usually at the next scheduled maintenance.
-
trom progresslnq
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IMPROVING AIRCRAFT SAFETY/4 2
FAA procedures do not normally require the designer
to take into account, by analyses, the hazard to one
component from the failure of some other component that
was designed to meet safe-life or fail-safe standards.
This has not been required because to do so would appear
to involve a contradiction of the definition of these
two structural design bases: why take into account a
failure that cannot occur?
These procedures, however, fail to take into account
an important consideration: structures designed not to
fail when subjected to conditions within the design
environment sometimes do fail, usually as a result of
hazardous conditions outside the design environment.
Examples of such hazardous conditions might include
maintenance-induced damage, hard impact by ground ser-
vicing equipment, cargo-induced damage, or perhaps even
faulty quality control during manufacturing. The simple
fact is that during the long life of many fleets of air-
craft, with millions of operations, one cannot guarantee
that such damage will not occur.
When one goes beyond matters of structure design to
consider similar design approaches to aircraft systems,
the problems can be compounded. Critical control sys-
tems, for instance, are designed so that the probability
of failing can be demonstrated to be "extremely remote."
The convention normally applied to this definition is a
calculation showing that the probability of failure is
one-in-one-billion (10-9) flights. However, critical
control systems also have failed from causes outside the
system design environment. The failure of a safe-life
or fail-safe structure that surrounds such systems is
currently not required to be considered within the sys-
tem~s design environment. Thus it is not taken into
account when analysing possible modes of systems failure.
The accident in Chicago* involved presumably incon-
ceivable combinations of events: the one-in-a-billion
failure of critical control systems caused by the im-
probable failure of a fail-safe component. That fail-
ure, in turn, resulted from maintenance-induced damage
not considered within the design environment of either
the structural or systems components.
In the committee's judgment aircraft design prin-
ciples should take into account the potential of struc-
tural damage caused by conditions outside the design
*See Appendix B.
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43/Type Certification and Rule Making
environment, and should seek to prevent catastrophic
effects resulting from such damage. Specifically, the
oo~ni~ttee re~orr~nends that the FAA develop a rule requir-
~ng assurance Chat an aircraft is designed to Continue
to fly after st~ot~raZ failure, unless that failure
itself prevents the aircraft from flying.
There are obviously some kinds of failure--a wing
torn off in a mid-air collision--that, by themselves,
prevent the aircraft from continuing to fly. In the
Chicago accident, however, a primary failure led to a
series of secondary failures of flight control systems
which, by making it impossible for the pilot to recover,
were the actual cause of the accident. It is this kind
of situation that justifies the need to go one step be-
yond the design assurances now required.
The recommendation would require that formal design
consideration be given systematically and routinely to
the consequences of the possible failure of critical
structure and systems, even though these can be shown by
analysis to meet design standards presumed to preclude
failure. Structural elements or systems that could be
rendered critical to continuing flight, because of the
initial failure of a primary structure, must be designed
to avoid or minimize being crippled or damaged by such
initial failures.
While the principle underlying this proposed rule
has not been generally applied, there are examples of
its application to specific cases, developed in response
to accidents that have occurred. One is the decompres-
sion venting of wide-body aircraft. The designer takes
into account unanticipated structural damage resulting,
for instance, from the inadvertent opening of a cargo
door or from a mid-air collision, which could cause floor
failure, and a secondary problem, such as the possible
interference with control cables. A second example is
the requirement that design consideration be given to
the trajectories of disintegrating engine parts, even
though such parts are designed to safe-life criteria.
The committee believes, moreover, that, with the
acceptance of this recommendation, the FAA should examine
currently certificated type designs to determine if they
substantially and reasonably comply with the rule that
would result from this recommendation. In cases where
they do not, it should consider issuing appropriate
Airworthiness Directives to accomplish changes that can
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IMPROVING AIRCRAFT SAFETY/4 4
reasonably be made or to permit exemptions for any
special circumstances that may exist.
The Issue of Public Access
The special issue just cited is one example of a
rule-related problem that is often first identified in
the course of type certification decisions. Other rule-
making issues also arise during the certification process
in the regional office. Several of these, including
cockpit design, the interpretation of cabin safety, and
the methods for determining crew complement, affect in a
direct way other parties as well as the manufacturers
and airlines with which the regional offices customarily
deal. Some could later affect other manufacturers, such
as the proposed retroactive imposition of an amendment
to the regulations dealing with accelerate-stop
distances.
The committee has heard many proposals for "openness"
in the certification process, especially with respect to
the issues raised in this study. We find that much of
the debate on the subject of openness involves a con-
fusion between the right of the public to be heard in
setting new standards (which is a formal rule-making
function in which the public clearly has the right to
participate) and the desire of the public to appear be-
fore, or even become voting members of, the Type Certi-
fication Board. The board is a decision-making body
only of FAA employees, in whose ultimate decisions the
public should not participate. FAA practices may inad-
vertently have added to the confusion in that certain
rule-making decisions--Special Conditions, exemptions,
or the retroactive application of amendments to the
regulations--are usually made in the course of type cer-
tification without providing the normal period for notice
and comment characteristic of formal rule making.
The committee recognizes that, in the course of
reaching formal decisions in these respects, there is a
vital element of negotiation that is best accomplished
by the parties most concerned--i.e., the FAA and the
applicant manufacturer. Moreover, there are instances
in which proprietary information is justifiably held in
confidence. Even so, the committee recognizes the right
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45/Type Certification and Rule Making
of the public to be heard in rule-making decisions, es-
pecially in the case of parties who are both knowledge-
able and interested in the consequences of such deci-
sions. Therefore, the committee recommends that the FAA
publish, as a notice in the Federal Register, the avaiZ-
abiZity of the FAA-approved preliminary regulatory and
certification bases for new aircraft type design, With
subsequent puLZioation of Changes thereto, to permit
time by review and comment by the pubZio and response
from the FAA.
In making this recommendation, we seek to accommodate
two equally important objectives: (i) consistent with
the Administrative Procedures Act, the public should be
given notice of rule-making decisions that are being
contemplated, and the FAA should receive and take into
account all pertinent information or recommendations
prior to making its final decision; and (ii) consistent
with the statute, any manufacturer may apply to the FAA
and hold confidential any information provided to the
FAA that would adversely affect the company's interest,
as long as the information "is not required in the
interest of the public.''l9
In practice, we are recommending that the regional
offices, through their respective Type Certification
Boards, increase the observance of rule-making formali-
ties with respect to their special rule-making decisions
--just as they now do in issuing Airworthiness Direc-
tives when time permits in nonemergency cases. The com-
mittee envisions the situation where, subsequent to
providing notice concerning the regulatory and certifi-
cation bases, the Type Certification Board would invite
all interested parties to make formal submissions for
review at one of its early meetings. Thereafter, within
a reasonable specified period of, say, 30 to 60 days,
the board, on behalf of the FAA, would be required to
make a formal, written, and public response to the issues
raised, addressing their merits and providing available
supporting data.*
*The relationship of the public to the activities of the
Type Certification Board is also being reviewed in the
Congress. At least one bill relating to the matter,
S. 11433 (95th Congress, 1st Session), is being con-
sidered in the Senate Committee on Commerce, Science,
and Transportation. A companion bill, H.R. 4679, also
has been introduced in the House of Representatives.
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IMPROVING AI RCRAFT SAFETY/4 6
The procedure contemplated should in no way restrict
the type board or design certification project engineers
from also seeking additional technical advice and counsel
from such appropriate sources as other government
agencies and individual specialists and consultants,
paid or volunteer, from industrial and academic set-
tings.
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Representative terms from entire chapter:
faa staff
