FACTORS; CONDITIONS; EVENTS cnecx | [seconany ] [privany
. Vv OUTAGE OUTAGE
- _ TIME TIME

8.4.5 Flooding
8.4.6 Other:
9.0 Confirmation/Certification

9.1 Retest incorrectly confirmed that repair was satisfactory

9.2 Retest not run

9.3 Retest set-up incorrectly

9.4 Retest run incorrectly

9.5 Technician misinterpreted retest findings

9.6 Did not certify repair

10.0 Recertification - Flight Inspection

10.1 Decision concerning whether or not to recertify
10.1.1 Did not initiate process (timely manner)
10.1.2 Performed process unnecessarily

10.2 Scheduled delay of Flight Inspection (FI) Aircraft
10.2.1 Limited availability of FI aircraft
10.2.2 Weather-related delays
10.2.3 Scheduling delays at busy airports

10.3 Flight Inspection (Duration)
10.3.1 Poor communications between AF and FI
10.3.2 Poor technical coordination between AF and FI
10.3.3 Process frequently interrupted but completed
10.3.4 Process incomplete; required rescheduling

11.0 Return Facility to Service/Reporting (Log Entry)

11.1 Improper operational set-up

11.2 Did not remove NOTAM

11.3 Did not report equipment operational

11.4 Log entry incorrect

11.5 Unable to contact facility control point

TOTAL OUTAGE DURATION

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AIRWAY FACILITIES

OUTAGE ASSESSMENT INVENTORY - FORM A (GNAS)

FACTORS; CONDITIONS; EVENTS CHECK SECONDARY PRIMARY
Vv OUTAGE OUTAGE
TIME TIME

1.0 Outage Causes (Coordinate With Cause Codes)

11

1.2

1.3

1.4
1.5
1.6
1.7

1.8
1.9

Equipment malfunction/failure

1.1.1 Hardware malfunction/failure

1.1.2 Software problem

1.1.3 Monitor alarm/shutdown

Interruption of commercial (leased) services
1.2.1 Commercial power failure

1.2.2 Commercial telephone service failure

Interruption of agency-provided services
1.3.1 Power

1.3.1.1 Prime
1.3.1.2 Standby
1.3.2 Landlines/Communications
1.3.2.1 Landline
1.3.2.2 Microwave

Outage related to transient or intermittent condition
Outage related to weather/storm (lightning strike)

Outage related to vehicle collision or interference

Outage related to previous maintenance action

1.7.1 Outage related to authorized equipment modification

1.7.2 Other:

=

Interruption of another facility/service

Interference due to atmospheric conditions

1.10 Contractor-induced outage

1.10.1 During equipment installation
1.10.2 During scheduled maintenance
1.10.3 During corrective maintenance
1.10.4 During airport improvement project
1.10.5 Other:

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No. Cause Code Duration (Hrs.) Facility/Service

10 80 0.90 TRAD

The outage occurred due to routine equipment failure. ATC reported the outage and restoration codes were
used in scheduling restore action. A qualified watchstander was available at the failed facility. Troubleshoot-
ing involved 0.50 hours, with 0.35 hours required to restore the system. Confirmation test involved 0.03
hours, with 0.02 hours necessary to return the facility to service.

W 80 2.10 ALS

The outage, which was detected by ATC, occurred due to commercial power failure. Use of FAA restoration
codes caused a 0.17 hours schedule delay of maintenance action. Travel time to the site took 0.25 hours.
Preparation for corrective maintenance involved 0.20 hours, with 0.05 hours needed to obtain technical data,
0.03 hours needed to obtain test equipment, 0.03 hours needed to check test equipment, and 0.09 hours
needed to obtain access to the suspected equipment area. Fault diagnosis required 1.00 hours. Fault correc-
tion took 0.25 hours due to the fact that the technician obtained the spares at the site and then replaced the
part/module. Confirmation/certification took 0.17 hours. Returning the facility to service/reporting required
0.06 hours.

12 80 4.00 ARSR

The outage, which was detected by AFS, occurred due to equipment failure. Locating and assigning a techni-
cian required 0.03 hours, while travel time to the remote site required 0.33 hours. Preparation for corrective
maintenance took 0.42 hours, with 0.25 hours needed to obtain technical data, 0.08 hours needed to check
the test equipment, and 0.09 hours needed to obtain access to the suspected equipment area. Fault diagnosis
took 2.50 hours. Fault correction (restoring the system) required 0.50 hours. The facility was returned to
service/reporting in 0.22 hours.

13 Bg*** 4.00 LDA

The outage was related to vehicle/aircraft damage or interference. The airport manager detected the outage.
The need to coordinate with the local power company delayed maintenance action for 1.17 hours. Locating
and assigning a technician required 0.25 hours since the watch stander was at the sector field office. Travel-
ling to the remote site in a government vehicle took 1.50 hours. Troubleshooting required 0.50 hours, as did
fault correction (system restoration), which required 0.50 hours. Confirmation/certification occupied 0.08
hours.

BS


HUMAN FACTORS IN AIRWAY FACILITYES MAINTENANCE:
DEVELOPMENT OF A PROTOTYPE
OUTAGE ASSESSMENT INVENTORY — FORM A

PURPOSE

There is continued interest within the airway facili-
ties (AF) maintenance community in identifying ways
of reducing both the incidence of equipment failure
and the time required to restore equipment to opera-
tional status following a failure. The result is improved
availability of the airways navigation and control sys-
tem, with the attendant enhancement of aviation safety.
Within the National Airspace System (NAS), AF main-
tenance duties are performed by two types of organiza-
tions, the General NAS (GNAS) Airway Facilities
Sector (AFS) and the Air Route Traffic Control Center
(ARTCC) AFS Sector. The two organizations are
similar in that they essentially perform the same types
of maintenance duties, including fault diagnosis
(troubleshooting), repairing or replacing equipment/
parts, confirmation (retest), recertification, and re-
porting the failed facility as operational. There are,
however, two major differences between the GNAS
and the ARTCC. The main difference between the two
organizations is that all of the facilities for which the
GNAS is responsible are out in the field or remote
from the sector building, whereas all of the facilities for
which the ARTCC is responsible are in the same
building. Thus, the GNAS is a field operation, while
the ARTCC is a more central (localized) operation.
The second difference between the two organizations
is that the GNAS provides the ARTCC with system
status data on the radar operability. The ARTCC uses
these data from the field sectors to manage Center
equipment resources. Important to the goal of en-
hanced system availability is thorough consideration
of human factors issues that may, in some fashion,
influence performance of the maintenance function.
An important philosophical consideration is that
this problem must be perceived from a maintenance
system viewpoint and not limited to scrutiny of any
one component as a sole contributor to system
downtime.

One should note that the AF maintenance commu-
nity uses the terms “downtime” and “time-to-restore”
synonymously. The term “outage” is used to mean (1)
the onset of an equipment failure (or out-of-tolerance
situation) or (2) the duration of time which elapsed
before the equipment or facility was restored. Hence,
“outage” may mean “failure,” “time-to-restore,” or
“downtime.” An outage begins when a detection agent
(AFS, Pilot, Air Traffic Control [ATC], Flight Service
Station [FSS]) reports an operational failure. An out-
age ends when the facility is properly returned to
service and all required reporting is accomplished.

There are many components of downtime or con-
tributors to the duration of a particular outage. These
could vary from test equipment availability, physical
accessibility of the failed facility, current weather,
availability of useful technical data, availability of
replacement parts, and so forth. Of course, availability
and capability of assignable maintenance technicians
is also an important factor. The point is that responsive
treatment of the problem of facility outages cannot rest
solely with attention to but one or two components:
the attempt must be made to provide a structure by
which all major classes of components or contributors
can be identified. It may not be possible to precisely
quantify their relative contributions, but their poten-
tial role in influencing downtime must be identified.
Therefore, the primary objective of this study was to
develop a technique or tool that identifies and maps
within a “systems” structure all potentially-significant
contributors to AF maintenance downtime. Further-
more, this technique should facilitate (a) the collection
of maintenance-related data at the required level of
detail during system restoration (including the assign-
ment of outage time values as they actually occur); (b)
the entry of those data into a data base; and (c) the
analysis of the data base for purposes of identifying
causal relationships. Ultimately, the technique should


APPENDIX B

NARRATIVE REPORT ON OUTAGE ASSESSMENT INVENTORY - FORM A

INITIAL APPLICATIONS

Bl


No. Cause Code Duration (Hrs.) * Facility/Service

05 82** 1.60 cD

This outage was due to a commercial power failure and was related to a transient or intermittent condition.
Failure was reported by AFS with restore action scheduling guided by restoration codes, A watchstander was
available at the facility who was qualified to certify the equipment operational. Environmental conditions at
the site added 0.60 hours to downtime. Troubleshooting involved 0.70 hours, which included some amount
of additional time since the technician overlooked or misinterpreted certain symptoms, and used incomplete
or wrong diagnostic information. Once the fault was isolated, correction required 0.10 hours. Confirmation
test required another 0.10 hours and returning the facility to service also involved 0.10 hours.

06 80 6.85 cD

This outage was due to routine equipment failure and was detected by AFS. Restoration codes guided restore
action scheduling. A watchstander was located at the facility who was qualified to certify the equipment as
operational. The fault required the use of specialized test equipment which was found to read inaccurately,
resulting in 2.00 hours additional in obtaining proper readings. Troubleshooting required an additional 2.15
hours, with 1.00 hours needed to repair the fault. Retest and recertification required 1.50 hours, with 0.20
hours needed to report the facility as operational.

07 80 0.05 ARSR

This equipment failure was routine and was detected by AFS, Restoration codes guided restore action sched-
uling. A watchstander was available at the facilicy with a proper position description to certify the equipment
operational. Fault diagnosis required 0.02 hours, with 0.02 hours needed to correct the fault. The facility was
returned to service in an additional 0.01 hours.

08 82 0.30 ATCRB

The fault, which resulted in the loss of commercial power, was induced by an AFS technician. ATC detected
the outage and restore action scheduling was guided by restoration codes. A qualified watchstander was
located at the SFO. Travel to the facility required 0.19 hours, with 0.05 hours required for fault diagnosis.
The system was reset in 0.02 hours, with 0.02 hours required for confirmation test. The facility was returned
to service in 0.02 hours.

09 80 0.20 ARTS

The failure was induced by AFS technician during performance of corrective maintenance. The outage was
detected by AFS and the restoration codes guided restore action scheduling. A technician qualified to certify
the equipment operational was located at the facility. Troubleshooting required 0.02 hours, with 0.16 hours
required to reset the system. Confirmation test involved 0.02 hours and the system was returned to service.

B4


FACTORS; CONDITIONS; EVENTS CHECK | | SECONDARY PRIMARY
v OUTAGE OUTAGE
TIME TIME

6.5.4 High winds
6.5.5 Flooding
6.5.6 Other:

7.0 Fault Diagnosis
7.1 Read/understood technical data

7.1.1 Did not read/understand technical data
7.1.2. Partially read/partially understood technical data
7.1.3 Misinterpreted/misused technical data

7.2 Used test support equipment

7.2.1 Used wrong test points

7.2.2 Used wrong electronic standards/tolerances
7.2.3 Used wrong test equipment set-up

7.2.4 Specialized test equipment inaccurate

7.3 Diagnosed fault (troubleshooting)

7.3.1 Used random approachiillogical reasoning

7.3.2 Overlooked/misinterpreted symptoms

7.3.3 Used wrong information/incorrect logic

7.3.4 Used incomplete information

7.3.5 Incorrectly diagnosed fault as "unknown"

7.3.6 Spares not available for troubleshooting purposes
7.3.7 Diagnostic incapable of determining problem

7.4 Additional diagnostic time due to environmental conditions

7.4.1 Snow/sleet/hail
7.4.2 Heavy rain

7.4.3 Extreme temperatures
7.4.4 High winds

7.4.5 Flooding

7.4.6 Other:

8.0 Fault Correction (Repair or Replace Equipment/Parts)
8.1 Obtained spares

8.1.1 At site

A7



“IB

Human Factors in Airway Facilities Maintenance

restore time cost. This was accomplished by using the
overall outage time obtained from SFO reporting data.
That value was apportioned among all factors identi-
fied as contributing to a given outage using SMEs with
direct knowledge of the outage to be assessed. Total
outage time currently is the only quantitative record
kept of the duration of a particular outage.

Initially, we believed that 0.10 hour (6 minutes)
would be sufficient as the smallest apportionable unit.
However, initial trials quickly indicated that a smaller
unit was required. Consequently, 0.0167 hours (1.0
minutes) was finally accepted as the smallest
apportionable or assignable unit of time. Outage value
assignment or apportionment to contributing compo-
nents is widely variable, ranging from a matter of days
in some instances (for example, awaiting a part or the
availability of a FI aircraft), to a matter of seconds (for
example, in checking settings on a piece of test support
equipment for correctness). .

Outage time values are not assigned or apportioned
to all first-order functions. Function 1.0 deals with
onset of the outage and any related inducing factors,
while Function 2.0 concerns the circumstances sur-
rounding the detection of the outage. Assignment or
apportionment of outage time values is initiated with
Function 3.0, Schedule Delay of Maintenance Action.

During the apportionment process, SMEs were

essentially asked to reconstruct the circumstances of a
particular outage from memory using available report-
ing materials and to apportion completion time values
to those components contributing to the outage.
AF supervisors who had been directly involved with
the restoration of a particular outage served as SMEs
and performed the apportionment task. Supervisors
were felt to have the broadest knowledge base and level
of comprehension concerning the circumstances sur-
rounding a given outage within their area of responsi-
bility. For the most part, comprehensive knowledge of
a given outage was limited to the supervisor and
perhaps the technician who performed the mainte-
nance; hence, it was not possible to obtain measures on
a given outage for more than one SME.

SMEs were encouraged to review their actions and
make whatever changes, reappraisals, or reapportion-
ments they desired. Objectives were to obtain (1) as
thorough a representation as possible in the OAI -

Form A of the circumstances and conditions surround-
ing a given GNAS outage; and (2) to obtain a reason-
ably accurate apportionment of the total duration time
of the outage to contributing components of the main-
tenance system, also identified in the OAI - Form A.
SMEs were instructed to perform the apportionment
step in hierarchical order, beginning with the higher-
order categories, and penetrating to progressively lower-
order (more detailed) factors and components. A useful
technique was for the SME to ask the following ques-
tion when considering each factor: “Did this factor or
outcome cost additional outage time?” The concept of
“outage time cost” seemed to facilitate the apportion-
ment process,

Results

All 14 GNAS initial-application outages were ana-
lyzed using the inventory. SMEs had little difficulty
reconstructing the circumstances and events surround-
ing a given outage. This process seemed to have been
greatly facilitated by the detailed structure of the
inventory. SME completion time for each of the 14
outages varied from five to 30 minutes, with an average
time of 12 minutes. All SMEs expressed a high confi-
dence level in their time apportionments and indicated
that the inventory added significantly to their under-
standing of the system components that contributed at
varying levels to overall outage time. Many com-
mented on the thoroughness of the inventory, and
were surprised at the exceedingly large number of
factors, conditions, and events that could influence
downtime.

A narrative description of each of the 14 outages
analyzed is included in Appendix B. At some future
point, software could be developed to generate much
more definitive descriptions of outage restoration ac-
tivities from the data collected by the OAI. Also,
statistical analysis software could be employed to sum-
marize and test various trends and relationships in the
data obtained.

During the apportioning process, additional in-
sights were obtained, which resulted in further revi-
sions and modifications to the component structure of
the OAI - Form A. One significant problem noted with
the approach was that, due to the remoteness of many
of the equipment facilities under a GNAS, several of


2. Personnel factors
Training and experience levels
Skills, knowledges, abilities
Personnel availability
Personnel assignability
Staffing levels
Shift scheduling
. Management
3. System/Equipment Design Factors
a. Equipment reliability (Failure rate)
b. Internal accessibility

emo aoe

c, Level (if any) of built-in-test

d. Level of automation

c. Test point availability

f. Degree of automatic switching
(redundancy)

4. Logistic Factors
a. Maintenance philosophy (repair/replace)
b. Parts sparing philosophy and location
c. Part availability (repair pipelines)
d. Quality/availability of technical manuals,
data
e. Availability of job performance aids (JPAs)
f. Availability and operability of test support
equipment
5. Physical Environment Factors
a. Geographic distance
b. Temperature
c. Illumination
d. Wind
¢. Physical impediments

From an overall systems’ viewpoint, the above-
listed factors (among others) could act singly or in
combination to limit or impede the process of correc-
tive maintenance (outage reduction).

Functional Framework

The above-listed corrective maintenance factors are
general to most corrective maintenance applications.
To be of use in the present application, these factors
needed to be represented in a functional framework
describing the AF maintenance process at the GNAS.
To provide that structure, a functional framework,
composed of 11 first-order functions, was devised that

Human Factors in Airway Facilities Maintenance

was bounded by the sequential progression of events,
beginning at the onset of a facility outage, and ending
when the facility is returned to service.

A taxonomy for classifying types of human errors
was developed and embedded in the functional frame-
work as First-Order Categories 6.0, 7.0, 8.0, and 9.0.
The work of Drury (1987), in developing task-based
frameworks, and that of Rouse (1990), in accounting
for sources of human error, was considered in this task.
Drury’s (1991) attempt to develop a task and error
taxonomy for aircraft inspection was also reviewed for
possible use. The first-order functional categories se-
lected to define the inventory are reported below.

1.0 Outage Causes (Coordinate With Cause
Codes)

2.0 Outage Detection

3.0 Schedule Delay of Maintenance Action

4.0 Locate and Assign Technician

5.0 Travel Time to Site

6.0 Preparation for Corrective Maintenance

7.0 Fault Diagnosis

8.0 Fault Correction (Repair or Replace
Equipment/Parts)

9.0 Confirmation/Certification

10.0 Recertification - Flight Inspection

11.0 Return Facility to Service/Reporting (Log
Entry)

Development of the Outage Assessment Inventory
(OAD

Utilizing the above-noted maintenance factors and
functional framework, various experimental forms of
an outage assessment device were developed and tested.
GNAS facility managers and technical personnel at the
Oklahoma City (OKC) GNAS Sector Field Office
(SFO) and the Memphis GNAS were consulted, and
available maintenance reporting data were reviewed.
Through this iterative process, the basic inventory was
evolved, extended, and refined. This resulted in a
preliminary form of an assessment device, which was
labeled, Outage Assessment Inventory (OAI) - Form
A. Heading information for this preliminary form of
the OAI (which is included in Appendix A) includes
(a) Facility/Service; (b) Ident. code; (c) Duration (of
the outage); (d) Open Date (of the outage); (e) Cause


Human Factors in Airway Facilities Maintenance

provide for the identification of alternatives or cost-
effective “countermeasures” for reducing restore times,
with the attendant gains in system availability. It was
also important that the’ technique have immediate
usefulness and value to the AF community, and be
adaptable as AF operations become increasingly more
automated and centralized in the future. A secondary
objective of the study, which was consistent with the
immediate-usefulness goal noted above, was to be able
to make use of past outage data as a means for building
the data base by determining whether overall outage
time values can be apportioned among the contribu-
tors to downtime using subject matter experts (SMEs)
who were intimately involved in restoring a given
outage. Thus, the apportionment process would in-
volve post hoc, after-the-fact analysis of outages.

APPROACH

Meeting the above objectives meant developing an
instrument that was sufficiently sensitive to the AF

maintenance process to identify human: factors and .

system variables that may contribute significantly to
system downtime. What was needed first was a means
for mapping the components of downtime operation-
ally based on a “systems” structure that would allow all
possible (or most) potential contributors and their
interrelationships to be identified. Further, it was
important to be able to apportion to those components
their specific shares of downtime; that is, to be able to
apportion a “cost level” to their contribution. Such
data would be important in assessing a particular
outage (or series of outages) with respect to causal
factors and their interactions. Finally, by having a
thorough understanding of most (if not all) factors
involved in a given outage, it would be possible to
identify cost-effective alternatives to reduce failure
rates and restore times, and improve availability.

Emphasis in the study was devoted to the GNAS. As
indicated above, the technical approach followed the
“systems” viewpoint to allow attention to conditions
and circumstances surrounding maintenance perfor-
mance involving equipment design, technical data,
support and work environments, and logistical sup-
port, as well as the human maintainer.

Electronics Maintenance System Performance
Factors :

The literature on models and structures for apprais-
ing electronics maintenance performance from a “sys-
tems” viewpoint was reviewed. Elapsed time required
to restore (correct) equipment (system, suite, unit,
facility) to operational status was adopted as the mea-
sure of performance. The early work of Rigby and
Cooper (1961) was considered for general guidance in
assessing maintainability. Other approaches for assess-
ing maintainer performance were obtained from
Towne, Johnson 8& Corwin (1983). Literature derived
from studies conducted on military systems was scru-
tinized particularly to identify a useful process/event
model for detailing linear functions in corrective main-
tenance. In this regard, information on kinds of main-
tenance errors committed on military systems was
located in the work of Orlansky & String (1981). The
following well-established corrective maintenance func-
tions were extracted from the literature for use in this
study: (a) fault detection; (b) fault recognition; (c)
fault localization; (d) fault isolation (troubleshoot-
ing); (e) fault correction; and (f) confirmation test.

Parker and Dick (1985) performed research rel-
evant to this study in identifying factors found to be
contributors to downtime in complex Navy electron-
ics systems. These factors were organized into catego-
ties useful in developing the assessment instrument, as
outlined below. Note that some categories relate di-
rectly to quality of maintainer performance while
others involve hardware design factors, logistical fac-
tors, impediments due to geographic location, diffi-
culty in obtaining physical access to equipment, and
corrective maintenance factors such as test equipment
operability and replacement part availability.

Corrective Maintenance Factors
1. Human behavioral processes

a. Information sensing, collection,
interpretation

b.  Specific/general knowledge base of
electronics

c. Deductive/inductive problem solving

d. Planning and strategy formulation

e. Action-taking/decision-making

f. Reevaluation and assessment



FACTORS; CONDITIONS; EVENTS

8.2 Restored system
8.2.1 Repaired/modified part/module
8.2.1.1 Did not repair/modify part/module
8.2.1.2 Repaired/modified non-failed part/module
8.2.1.3 Induced new fault
8.2.1.4 Proprietary module (could not access)
8.2.2 Replaced part/module
8.2.2.1 Did not replace part/module
8.2.2.2 Replaced wrong part/module
8.2.2.3 Induced new fault
8.2.2.4 Correct part/module unavailable
8.2.3 Reset system
8.2.3.1 Improperly reset system
8.2.3.2 Did not reset system
8.3 Coordination with non-AFS activities
8.4 Additional restore time due to environmental conditions
8.4.1 Snow/sleet/hail
8.4.2 Heavy rain
8.4.3 Extreme temperatures
8.4.4 High winds

A8&

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—sDwdorteaoiic OSTM”

8.1.3 Within sector

8.1.4 By order from supplier

8.1.5 Part(s) in repair pipeline

8.1.6 From prime equipment manufacturer

8.1.7 Purchased locally

8.1.8 Correct part(s) not available from any source

8.1.9 Available spares not serviceable

8.1.10 Ordered wrong parts due to misdiagnosis

8.1.11 Did not order any parts due to misdiagnosis

SECONDARY PRIMARY | |
OUTAGE outace |}.
TIME TIME



Human Factors in Airway Facilities Maintenance

Table 1. Test Outages Used in Initial Applications of OAI - Form A.

No. Cause Code

Duration (Hrs.)

Facility/Service

o1 80*
02 80
03 80
04 80
05 82**
06 80
07 80
08 82
09 80
10 80
1 80
12 80
13 gee
14 80

2.05 RCAG
50.80 VOR
8.46 MALSR
5.40 ARSR
1.60 cD
6.85 cD
0.05 ARSR
0.30 ATCRB
0.20 ARTS
0.90 TRAD
2.10 ALS
4.00 ARSR
4.00 LDA
7.25 VOR

*80 = Equipment Failure
**82 = Prime Power Failure
***89 = “Other”

contained in a given outage. The secondary objective
was addressed by determining the facility with which
SMEs could apportion a time duration value for a
particular outage to all contributing components.

Selection of Test Outages

GNAS sector managers and supervisors were con-
sulted, along with available maintenance reporting
data to identify candidate outages for the test. An
attempt was made to represent facilities with relatively
wide ranges of outage records and also to represent
various types of equipment (e.g., radar, power, com-
munications). Using this procedure, 10 previous OKC
GNAS equipment outages and four previous Memphis
GNAS equipment outages were selected for analysis.
Outages varied from .05 hours to 50.80 hours, with 10
different types of facilities represented. Table 1 sum-
marizes the details of the test outages.

Mapping Outage Factors

Using the test outages listed in Table 1, the compo-
nent structure of the OAI - Form A was reviewed and
refined through an iterative process involving SMEs
from Oklahoma City and Memphis GNAS facilities.

The primary object of this step was to determine the
completeness and sensitivity of the OAI. It was impor-
tant that the component structure be thoroughly de-
scriptive of the possible contributors to downtime
without being redundant. Also, the hierarchical struc-
ture of the inventory was verified, ensuring that the
level of information was consistent throughout.
Through the continuing process of refinement, the
inventory was developed into a tightly-organized set of
potential components of downtime, which could be
used effectively in mapping the causal circumstances
of a given outage. The final, revised form is included in
Appendix A.

Apportioning Outage Time Values to Downtime
Components

In accordance with the study's main objective, when
actually used, the inventory would serve as a data
teporting and recording tool, and outage time values
would be assigned as they occurred, essentially in real
time. However, to meet the study’s second objective, it
was necessary to determine the ease with which outage
values could be apportioned to the components previ-
ously identified as contributors to downtime or to

so


No. Cause Code Duration (Hrs.) Facility/Service

14 80 7.25 VOR

The outage occurred due to equipment failure. The RMMS/MCC detected the outage. Locating and assign-
ing a technician required 0.25 hours, Travelling to the remote site in the technician’s personal vehicle
involved 1.00 hours. Preparation for corrective maintenance took 0.17 hours, while fault diagnosis took 3.00
hours (including 1.00 hours needed for using test support equipment and 2.00 hours needed for trouble-
shooting). Fault correction required 2.16 hours, with 1.84 hours needed to obtain spares at the sector field
office and 0.42 hours needed to replace the part/module and reset the system. Confirmation/certification
took 0.50 hours and the facility was returned to service/reporting after an additional 0.17 hours.

Cause Codes: *80 = Equipment Failure
**82 = Prime Power Failure

“89 = “Other”

Minimum outage duration unit = 0.0167 hours = 1.00 minutes

RUS. GOVERNMENT PRINTING OFFICE: 19m + Sepocs/eoin

B6


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Human Factors in Airway
Facilities Maintenance:
Development of a Prototype
Outage Assessment Inventory

REE

APR 191994
So

Robert E. Blanchard
Jennifer J. Vardaman

Civil Aeromedical Institute A
Federal Aviation Administration

Oklahoma City, Oklahoma 73125

February 1994

Final Report ‘

This document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22161.

@

U.S. Department
of Transportation

Federal Aviation
Administration

laos


Human Factors in Airway Facilities Maintenance

4. Design or identify techniques for analyzing
OAI data to identify cost-effective interventions for
treating specific components of the AF maintenance
process to effect overall gains in equipment availabil-
ity. Countermeasures to problems discovered could be
designed at any hierarchical level of the inventory,
depending upon potential payoffs judged possible in
improving facility availability. To be useful, data on a
minimum number of outages of a particular classifica-
tion would need to be collected. The technique could
be based on some type of prioritization scheme, by
which possible countermeasures could be assessed and
recommended for action on the basis of cost benefits or
payoffs in reducing facility downtime. This step also
might be taken at a local GNAS initially to explore and
test various possibilities.

5. Appreciate that for long term consideration,
highly-specialized data collection formats, like the
OAI, will require periodic review and revision as the
AF support system is expanded and new technology
added. Changes in functionality and increases in level
of automation, with attendant shifts in responsibility
between human and machine, will impact the struc-
ture of the OAI and will need to be considered to
maintain its usefulness.

REFERENCES

Department of Transportation/Federal Aviation Admin-
istration. Operational Requirements for the Remote
Maintenance Monitoring System (RMMS). Wash-
ington, D.C.: Federal Aviation Administration;
1984, FAA publication no. NAS-MD-792.

Department of Transportation/Federal Aviation Admin-
istration. Facility Operation and Administration.
Washington, D.C.: Federal Aviation Administra-
tion Air Traffic Operations Service; 1989. FAA
publication no. 7210.31.

Department of Transportation/Federal Aviation Admin-
istration. General Maintenance Handbook for Air-
way Facilities, Washington, D.C.: Federal Aviation
Administration Airway Facilities; 1991. FAA pub-
lication no. 6000.15B.

Department of Transportation/Federal Aviation Admin-
istration. National Airspace Performance Reporting
System, Washington, D.C.: Federal Aviation Ad-
ministration Systems Maintenance Service; 1991.
FAA publication no. 6040.15C.

Drury, C. G. (1991). Errors in Aviation Maintenance:
Taxonomy & Control. In Proceedings of the Human
Factors Society, 35th Annual Meeting, Santa Monica,
42-56.

Dnury, C. G. (1987). Task Analysis. In Salvendy, G.
(Ed.), Handbook of Human Factors (pp. 370-401).
New York: Wiley & Sons.

Orlansky, J., 8 String, J. (1981). Performance of Mainte-
nance Technicians on the Job. Institute for Defense
Analysis Paper P-1597, August.

Parker, E., & Dick, R. (1985). Factors Responsible for
Navy Electronic Equipment Downtime. Technical
Note 71-85-08, Navy Personnel Research and De-
velopment Center, May.

Rigby, L. V., 8& Cooper, J. I. (1961). Problems and
Procedures in Maintainability. ASD Technical Note
61-126. Aeronautical Systems Division, USAF,
October.

Rouse, W. B. (1990). Designing for Human Error. In
Booher, H. R., (Ed.), Manprint: An Approach to
Systems Integration (pp. 237-255). New York: Van
Nostrand Reinhold.

Towne, D. M., Johnson, M. C., & Corwin, W. H.
(1983). A Performance-Based Technique for Assess-
ing Equipment Maintainability. Technical Report
No. 102, Behavioral Technology Laboratory, USC,
August.


the maintenance actions are performed by a technician
without supervision. For example, 6.0 - Preparation
for Corrective Maintenance, 7.0 - Fault Diagnosis, 8.0
- Fault Correction, and 9.0 - Confirmation/Certifica-
tion are usually performed remotely by a single techni-
cian. Under such circumstances, there is no ready
source of “objective” data; the inventory becomes
essentially a “self-reporting” device. It seems unrealis-
tic to assume that a technician would essentially put
him or herself “on report,” so to speak, for an error or
errors committed that had contributed to downtime
associated with a particular outage.

This problem is often encountered in human per-
formance measurement, where it may be possible to
develop measures of a certain type of performance, but
often quite a different matter to collect data on those
measures. However, in the initial application of the
OAI - Form A, there were several instances in which
the supervisor had information concerning procedures
used at the site, particularly Outage No. 05, in which
lack of proper information necessary for troubleshoot-
ing was noted. Outages are critical events to an SFO,
and to the various supervisors and organizations within
that office. Ina sense, each outage has its own personal-
ity composed of events, conditions, and circumstances
that cause it to be distinct from other outages. Indi-
viduals, such as the supervisors who participated in
this study, tend to have excellent recall of the circum-
stances of each individual outage, though some of the
outages used in this study were nearly two years old,
with the oldest one occurring four years earlier. Fur-
ther, supervisor awareness of the OAI will provide a
ready framework for recalling and organizing the events
of an outage when apportionment is done at some later
time,

In summary, it was found that the OAI - Form A was
a highly effective instrument for mapping the events,
circumstances, and conditions of a given GNAS out-
age necessary for use as an on-line data collection tool.
Further, if data cannot be recorded in real time during
the actual process of outage restoration, or if it is
desired to use historic data to build an outage compo-
nent data base, experienced maintenance supervisors
seem quite capable of apportioning the associated total
outage time to the various contributing factors.

Human Factors in Airway Facilities Maintenance

RECOMMENDATIONS

Form A of the OAI is at a prototype level of
development. Considerable additional work will be
required if the concept of a systems-based, compo-
nents-of-downtime approach to root-cause analysis of
AF outages is to be brought to fruition. Following are
some recommendations for future work.

1. Perform additional tests on Form A of the OAI
within the GNAS community. Further confirm, ex-
tend, and refine the classification and taxonomic struc-
ture of the preliminary inventory, as required.
Determine features, formats, and procedures that would
render the inventory most useful to the AF commu-
nity, with minimum requirements for additional ad-
ministration time. Identify approaches for collecting
data on maintenance activities performed at remote
sites where one technician is assigned. Explore the
possible use of any existing maintenance monitoring
and reporting systems as a source of supporting data
for the OAI.

2. Identify and evaluate possible avenues for in-
stalling and applying Form A of the OAI, such that it
can be completed coincident with the occurrence of an
outage by the various individuals involved. This would
require the cooperation of a GNAS interested in ex-
ploring the potential of the OAI for their facility. Form
A of the OAI would need to be installed along with
procedures for incorporating it as an integral part of
the outage restoration process. An evaluation would
need to be conducted depending upon frequency and
characteristics of outages occurring. Union support
may be required for this step.

3. Explore possibilities for introducing the data
collected by the OAI into the maintenance reporting
and analysis system maintained by the AF community.
At the very least, the OAI classification structure could
be used as a means for encoding data for entry into a
computer file. The results could be used to further
explicate the cause code system currently used to
classify outages. The results could also be used to
analyze conditions and factors across outages, and
within and between facilities to identify patterns of
events and outcomes and to perform trend analyses.



Human Factors in Airway Facilities Maintenance

Code (from Order #6040.15C); (f) Recorder (name of
person[s] who recorded the outage time values); (g)
Open Time (of the outage); (h) End Date (of the
outage); (i) End Time (of the outage); and (j) Remarks
(about the outage).

It became clear during this process that the geo-
graphic location of the responding technician had a
substantial impact on downtime; that is, whether the
technician was located at the site, at the SFO, or
elsewhere had a significant effect on downtime. In the
latter instance, travel time became’an important con-
tributor to downtime. At this juncture, it became
obvious that separate assessment inventories would
need to be tailored for the GNAS and the ARTCC, in
that the circumstances for responding and supporting
corrective maintenance activities differ significantly
between the two types of organizations, particularly in
proximity to the failed facility or system. Also, it
became apparent that the particular guidance followed
in scheduling restore action was of critical importance
in that ATC guidance on repair scheduling could
result in considerable additional downtime.

As indicated above, the OAI was to provide first for
mapping the specific circumstances (factors, condi-
tions, or events) involved in a particular outage, and
second for apportioning or assigning a downtime value
to each component contributing to an outage. Conse-
quently, application of the OAI would. require two
steps: (1) specific factors, conditions, or events rel-
evant to the outage occurrence and detection would be
identified and checked in the appropriate Check box;
and (2) a portion of total downtime considered appro-
priate for each factor, condition, or event identified in
Step 1 would be entered in the appropriate Outage
Time box.

The hierarchical nature of the OAI allows for level
of detail about any given outage to be determined by
the amount of information available for a particular
factor. The data recorder can penetrate quickly to that
level of specificity commensurate with the amount and
quality of information available. This protects against
the “all or none” basis of data collection in which
information on a factor is lost if not available at the
most specific level. For example, Factor 10 concerns

Flight Inspection (FI) recertification (if necessary)
after equipment restoration. The following levels of
analysis are available:

10.0 Recertification - Flight Inspection

10.1 Decision concerning whether or not to
recertify

10.1.1 Did not initiate process (timely manner)

10.1.2 Performed process unnecessarily

10.2 Scheduled delay of Flight Inspection (FI)
Aircraft

10.2.1 Limited availability of FI aircraft

10.2.2 Weather-related delays

10.2.3 Scheduling delays at busy airports

10.3 Flight Inspection (Duration)

10.3.1 Poor communications between AF and FI

10.3.2 Poor technical coordination between AF
and FI

10.3.3 Process frequently interrupted but
completed ’

10.3.4 Process incomplete; required rescheduling

At the highest order of detail, outage time data need
only be available for total time cost for recertification
(10.0). The next hierarchical level allows penetration
to time costs for decision - making (10.1), scheduling
Fl aircraft (10.2), and performing the flight inspection
(10.3). If additional data are available or can be ob-
tained, the analysis can penetrate to a third hierarchi-
cal level and identify costs due to (a) the specific nature
of the error in decision making (10.1.1-10.1.2); (b) the
specific reason for the time cost in scheduling FI
aircraft (10.2.1-10.2.3); and (c) specific causes for
extended duration of the flight inspection process
dealing predominately with AF/FI interaction and
interference at the site (10,3.1-10.3.4).

INITIAL APPLICATIONS

Preliminary test applications of the OAI - Form A
were conducted at both the OKC GNAS and the
Memphis GNAS, in which the two objectives of the
study were addressed. The primary objective was ad-
dressed by determining the degree to which the inven-
tory accounted for all identifiable, time-relevant factors



NARRATIVE REPORT ON ANALYSIS OF OUTAGES USED IN INITIAL
APPLICATIONS OF OAI - FORM A

No. Cause Code Duration (Hrs.) Facility/Service

01 80* 2.05 RCAG

Failure was induced by AFS technician during equipment installation which was related to a previous main-
tenance action. The outage was detected by ATC. Fault diagnosis required 1.20 hours, with 0.40 hours spent
using test support equipment and 0.80 hours spent in troubleshooting. Restoration required 0.10 hours to
repair a part or module, with 0.10 hours required to replace it once repaired. The system was retested,
requiring 0.65 hours and was then returned to service.

02 80 50.80 VOR

Failure occurred during routine system operation and was detected by ATC. ATC guidance in scheduling
maintenance delayed action for 44.80 hours. Distance to facility required 2.00 hours of travel time. Trouble
required 0.30 hours to isolate. Replacement module was proprietary equipment and not repairable, which
required an additional 2.00 hours to obtain new part from SFO. To install the part required 1.00 hours, with
retest requiring 0.50 hours. The facility was returned to service, involving 0.20 hours.

03 80 8.46 MALSR '

Failure occurred during routine operation and was detected by ATC, who requested a 1.50 hours delay in :
initiating maintenance action. Obtaining a AF technician with proper position description for the task

required 2.76 hours, with 0.60 hours travel time needed to reach the facility, where another 0.10 hours was

required to obtain access to facility. Severe environmental conditions at the site added 1.00 hours to the

restoration. Maintenance involved use of test support equipment not available at the site, adding 0.10 hours

to obtain equipment from truck. Obtaining access to suspected equipment area required 0.10 hours. Test

support equipment was used 0.30 hours, with 0.70 hours spent in troubleshooting, Spares to correct fault

were only available at the SFO, requiring 0.50 hours for delivery to site. Part/module replacement required

0.20 hours, with 0.50 hours needed for confirming by retest. Returning the facility to service required an

additional 0.10 hours.

04 80 5.40 ARSR

This outage occurred as a result of a transient or intermittent condition and was detected by AFS. Restore
action scheduling was guided by restoration codes. The technician available at the facility was not certified
for the task which required a qualified technician to be dispatched by the SFO, requiring 1.50 hours travel
time to the facility. Troubleshooting required 0.20 hours and with spares available at the site, the required
module/part was replaced in 2.00 hours. Confirmation retest needed 1.60 hours, with 0.10 hours required to
report the facility as restored for service.

B3


TABLE OF CONTENTS

Purpose

Approach
Electronics Maintenance System Performance Factol secessccssesseseessesee 2
Functional Framework ...c..scssssccsssessssesssescsseessssssssssssucesuecssucssasssssecsssense 3
Development of the Outage Assessment INVENTOLY «oe eecscessetseeeeseees 3

Initial Applications .......cesssesssecsssssssescsssesssessssssssssesssssssuscsssscssssesssssssssassusstseceuscess 4
Selection of Test Outages ....cccscccssscecessesssesserescsesssesssscststsesssssscscsteeseess 5
Mapping Outage Factors ........cccsssssesssssssessssssssssssrsesstssesacsecsesscessucecsssavece 5
Apportioning Outage Time Values to Downtime Components ............ 5
Results

Recommendations

References... essscsesesssssessessssesseesseessees
Appendix A: Outage Assessment Inventory - FOrm A uu. eesecccseseseeeees Al

Appendix B: Narrative Report on Outage Assessment Inventory -

Form A - Initial Applications .........cccsscsssssssssssssssssecsscsessessessessessessesssee B1



OUTAGE OUTAGE
TIME TIME

FACTORS; CONDITIONS; EVENTS — CHECK “rt | ES

1.11 AFS-induced outage
.11.1 During equipment installation
-11.2 During scheduled maintenance

1

1

1.11.3 During corrective maintenance
1.11.4 Did not switch to standby equipment
1.11.5 Did not go to back-up
1
1
1

.11.6 Inadvertent shutdown

.11.7. Maintenance Control Console (MCC)
-11.8 Other:
1.12 ATC-induced outage
1.12.1 Did not go to back-up

1.12.2 Inadvertent shutdown
1.12.3 Selected use of out-of-service standby equipment
1.12.4 Other:

Outage Detection

2.1 AFS (Non-RMMS)

2.2 AFS-RMMS/MCC

2.3 Pilot

2.4 Airport managers or other personnel
2.5 Air Traffic Control (ATC)

2.6 Flight Service Station (FSS)

2.7 Other:

Schedule Delay of Maintenance Action

1 10) WI

3.1 Repair scheduling priority considerations
3.1.1 FAA restoration codes
3.1.2 ATC guidance
3.1.3 Criticality of need vs. cost
3.1.4 Other:
Locate and Assign Technician

} WI

4.1 Technician availability/assignability
4.1.1 Watch stander at failed facility

A4



FACTORS; CONDITIONS; EVENTS CHECK SECONDARY PRIMARY
v OUTAGE OUTAGE
TIME TIME

6.1.2 Technical data incorrect
6.1.3 Technical data incomplete
6.1.4 Technical data not usable (level)
6.1.5 Technical data difficult to access
6.1.6 Did not obtain technical data
6.1.7 Obtained/used incorrect technical data
6.2 Obtained test equipment
6.2.1 Proper test equipment.not available
6.2.1.1 Not available at site
6.2.1.2 Not available at sector field office
6.2.1.3 Not available in sector
6.2.1.4 Not available in region
6.2.2 Test equipment not appropriate (suitable)
6.2.3 Test equipment incomplete
6.2.4 Test equipment not working
6.2.5 Test equipment out of calibration window
6.3 Checked/set-up test equipment
6.3.1 Did not check test equipment
6.3.2 Checked or set-up test equipment incorrectly
6.3.3 Test equipment internal checks/set-ups not working
6.4 Obtained access to suspected equipment area
6.4.1 Removed wrong access cover, subassemblies
6.4.2 Equipment area not accessible
6.4.3 Suspected assembly/LRU not physically accessible
6.4.4 Necessary test points not available
6.4.5 Necessary test points not accessible
6.4.6 Necessary test points not clearly marked
6.5 Additional preparation time due to site conditions
6.5.1 Snow/sleet/hail
6.5.2 Heavy rain
6.5.3 Extreme temperatures

AG

e_—_—



ACKNOWLEDGMENTS

This project was sponsored originally by ASM-200 with direction and support provided by Mr.
Cogan Marshall (ASM-201). Later, sponsorship was assumed by ANS 3.1 with Ms. Brenda Boone as
point-of-contact. Program managership was provided by Mr. John Wiley, ACD-350, FAA-Technical
Center.

Numerous individuals within the Oklahoma City Airway Facilities Sector, Bethany, Oklahoma, and
the Memphis Airway Facilities Sector, Memphis, Tennessee, provided support by supplying technical
information and guidance, and by serving as subject matter experts during the process of designing and
testing the Outage Assessment Inventory - Form A. Within the Oklahoma city Airway Facilities Sector,
the valuable support and guidance provided by Mr. Jack Oxford, Sector Manager, and Mr. Ernie Hosack,
Assistant Sector Manager, is gratefully acknowledged. In addition, the efforts of Mr. Vince Preston,
Sector Manager, Jacksonville Airway Facilities Sector, Jacksonville, Florida, were of considerable value
in reviewing draft editions of the inventory. Finally, the efforts of many of the staff of the Oklahoma
City Airway Facilities Sector were vital to the review and initial operational test of the inventory, as
follows:

Mr. Bill Jessee, Manager, Will Rogers NAVCOM Sector Field Office
Mr. Ray Carter, Manager, Will Rogers Airport Radar Sector Field Office
Mr. Charlie Youngblood, Proficiency Development Specialist

Mr. Dennis Rice, Assistant Manager for Technical Support

Mr. Jeff Lyons, Technical Support Staff

Mr. Chris Dumesnil, Technical Support Staff

Within the Memphis Airway Facilities Sector, Mr. Jim Sanford, Sector Manager, and Mr. Ted
Stratton, Manager, Memphis Sector Field Office, were particularly helpful. The assistance provided by
others on staff at the Memphis Airway Facilities Sector is gratefully acknowledged, as follows:

Mr. Gerald Vowell, MCC Supervisor
Mr. Bill Willard, Supervisor, NAVCOM Unit
Mr. Bill Strickland, Supervisor, Radar Unit

Mr. Larry Morrow, Supervisor, Environmental Support Unit

ii


Technical Report Documentation Page

1. Report No. 2, Government Accession No. 3. Recipient's Catalog No.
DOT/FAA/AM-94/5
4, Title and Subtitle 5. Report Date

Human Factors in Airway Facilities Maintenance: Development of | February 1994
a Prototype Outage Assessment Inventory - Form A

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.
Robert E. Blanchard and Jennifer J. Vardaman
9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aeromedical Institute
P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered

Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W.
Washington, DC 20591

14. Sponsoring Agency Code

15. Supplemental Notes

Prepared for: Program Office, Human Factors in Airway Facilities Maintenance, FAA Technical Center,
Atlantic City, NJ.

16. Abstract

‘The airway facilities (AF) maintenance community is concerned with identifying ways of reducing both the incidence of
equipment failure and the amount of time required to restore equipment to operational status following a failure. It is vitally
important to identify the many components of downtime and contributors to a particular outage (equipment failure). Thus, the
primary objective of this study was to develop a technique or tool with which to identify and map within a "systems" structure all
potentially-significant contributors to AF maintenance downtime. The technique was designed to facilitate (a) the collection of
maintenance-related data during an actual outage; (b) the entry of this data into a data base; and (c) the analysis of the data base in
order to identify causal relationships. The secondary objective was to be able to make use of past outage data as a means for
building the data base by determining whether overall outage time values can be apportioned among the contributors to
downtime using subject matter experts (SMEs) who were intimately involved in restoring a given outage, SMEs from the
Oklahoma City (OKC) General National Airspace System (GNAS) Airway Facilities Sector (AFS) and the Memphis GNAS
AFS assisted in the iterative design and review process that produced the Airway Facilities Outage Assessment Inventor) . Form A
(AFOAN). Ten previous OKC GNAS outages and four previous Memphis GNAS outages were analyzed using the AFCAI - Form
A, thus confirming that the inventory is a useful tool in identifying specific contributors to AF maintenance downtime.
Recommendations were to continue to refine the format of the AFOAI and to install it on a trial basis to test its usefulness in
collecting and analyzing data on factors and conditions contributing to facility outages.

17. Key Words 18. Distribution Statement

*Airway Facilities *Data bases “Corrective maintenance | Document is available to the public through the

*Human factors *Quantification *Maintenance reporting National Technical Information Service,
Springfield, Virginia 22161.

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 26

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized


APPENDIX A

OUTAGE ASSESSMENT INVENTORY (OAI)
FORM A - GNAS

Al


FACTORS; CONDITIONS; EVENTS

CHECK

PRIMARY
OUTAGE
TIME

4.1.2 Watch stander at sector field office (SFO)
4.1.3 Unable to contact technician on callback
4.1.4 Certified technician unavailable
4.1.5 Technician reassigned en route
4.1.6 Technician assigned inappropriate for site
5.0 Travel Time to Site
5.1 Conditions/circumstances
5.1.1 Picked up vehicle or materials at SFO
5.1.2 Additional travel time due to weather en route
5.1.2.1 Snow/sleet
5.1.2.2 Heavy rain
5.1.2.3 Limited visibility/fog
5.1.2.4 Flooding
5.1.2.5 Other:
5.1.3 Remote site
5.1.4 Limited accessibility to site

5.2 Travel policies in effect
5.2.1 Use of government vehicles
5.2.2 Use of personal vehicle
5.2.3 Overnight stay
5.2.4 Limited travel funds
5.3 Mode of transportation
5.3.1 Government car/truck
5.3.2 Boat
5.3.3 Aircraft
5.3.4 Off-road vehicle
5.3.5 Snow cat
5.3.6 Private vehicle (POV)
6.0 Preparation for Corrective Maintenance
6.1 Obtained technical data
6.1.1 Necessary technical data not available

AS

SECONDARY
OUTAGE
TIME