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Implementation of an LDA/DME
Approach to Runway 16R in Lieu of a Third Runway at Sea-Tac
I. INTRODUCTION
The April 1995 Seattle-Tacoma International Airport Master Plan
Update Draft
Environmental Impact Statement, (DEIS, Chapter 11 ), identifies
seven alternatives to
"Improve the Poor Weather Airfield Capability In A Manner That
Accommodates
Aircraft Activity With An Acceptable Level of Aircraft Delay."
The alternatives are:
a. Use of other modes of Transportation
b. Use of other Airports or Construction of a New
Airport
c. Activity Demand Management
d. Runway Development at Sea-Tac
e. Use of Technology
f. Blended Alternative (Combination of other
modes, use of existing airports, and activity
demand management).
g. Do-Nothing/No-Build
The DEIS concludes that the preferable alternative to improve
"poor weather" airfield capability is to construct an 8500 foot
runway 2500 feet West of Runway 16L/34R. The DEIS infers that an
LDA Approach to Sea-Tac is not viable due to the frequency of
"poor weather". The Port attributes this conclusion based on the
poor weather conditions they claim exist 44% of the year.
LDA has and will be referred to many times in this report
therefore; following is a definition of the term LDA. The
Localizer Directional Aid (LDA) is an electronic beam used to
guide aircraft to a specific point in space. It works similar to
the localizer beam of an Instrument Landing System (ILS). Unlike
an ILS the LDA is not aligned with a runway. The beam is used as
guidance through the clouds. After descending clear of the clouds
the pilot then abandons the course guidance and executes a side-
step type of maneuver to the runway of intended landing. In the
case of Sea-Tac the landing runway would be 16R.
This report refutes the DEIS analysis of "poor weather" and its
impact on the airports ability to accommodate the aircraft
activity forecast in the year 2020.
This report supports the following conclusions:
Detailed analysis of SEA-TAC weather (years 1993 and
1994), refutes the Port's claim that 44% of the
time, weather conditions limit the airport to
single flow operations. Detailed analysis reduces
that period of time to approximately 17% annually.
An LDA/DME approach procedure to runway 16R is
feasible, and will reduce the capacity forecast
delay for the year 2020 to an acceptable level.
With the installation of an LDA runway 16R the year
2020 annual forecast and dally hourly demand
identified in the DEIS can be accommodated in an
orderly fashion negating the need to construct a
third runway.
II. DETAILED WEATHER ANALYSIS.
To understand the significance of such detailed weather, when it
existed, and how airfield capacity demands can be influenced by
bad weather etc., it is necessary to understand the definitions of
the weather conditions at Sea-Tac:
Visual Flight Rule 1 (VFR-1). Ceiling (height of cloud
base above the ground) is at least 5,000 feet and
visibility at least 5 miles.
Visual Flight Rule 2 (VFR-2). Ceiling is between 2,500
feet and 4,999 feet and visibility is more than 3 miles.
Instrument Flight Rule 1 (IFR-1). Ceiling is above 800
feet and less than 2,499 feet and or the visibility is
less than 3 miles.
Instrument Flight Rule 2 (IFR-2), and (IFR-3), and (IFR-
4). Ceilings from zero to less than 800 feet and
Visibility zero to 2 miles. IFR-4 is the worst ceiling
and visibility weather condition.
The DEIS states that 10 years of weather was reviewed 1 and
concludes a third runway is required at Sea-Tac. That review of
the weather data resulted in a determination that 44% of the year
weather conditions exist that prevent air traffic control from
utilizing dual arrival flows. Delays occur when hourly traffic
demands exceed single arrival flow capacity. The DEIS contends
that the excess operations are delayed beyond a reasonable time
and that the costs to the airlines and the traveling public are
not acceptable. The conclusion is that a third runway constructed
at Sea-Tac will allow dual arrival streams during inclement
weather conditions and that the increase in hourly airport
capacity will reduce the remaining delays to an acceptable level.
To determine if the DEIS weather analysis was correct, two years
of hourly airport weather observations were obtained from the
National Weather Service (I 993 and 1994). The data is the exact
hourly weather reported 24 hours per day each day of each month
for the two year period. This detailed weather was analyzed with
the confidence that It depicted exactly what the weather
conditions were any given hour of any day or month during the two
year period.
The analysis concluded that weather conditions requiring single
stream flow at SeaTac is not 44% as claimed in the DEIS. Instead
the 1993 and 1994 "Poor weather' that requires single stream
arrivals after implementing an LDA procedure is approximately 17%.
That is a significant difference from the DEIS conclusions,
especially when airport efficiency is at Issue.
At Sea-Tac during VFR-2 and all IFR weather conditions, the DEIS
claims arriving aircraft are limited to a single stream. This is
the result of only one runway being equipped with an ILS and the
capacity constraints that result from such an arrival
configuration. The DEIS states that during VFR-1 conditions the
maximum hourly arrival acceptance rate is 60. VFR-2 is 48, IFR-1
36, and IFR-2, 3, and 4 Is 24. In the DEIS weather analysis, no
consideration is given to what time of day poor weather conditions
exist. The DEIS 44% VFR-2 and IFR-1, 2, 3. 4 weather is spread
evenly throughout the day which supports the claims of excessive
delay and subsequent cost to the airlines and flying public.
Logic would say that some of that poor weather had to occur during
off-peak hours and therefore, did not cause delays due to a single
flow arrival stream. If the proportion of the 'poor weather' is
higher during off peak hours, the delays due to a single flow
arrival stream are less.
To properly analyze the actual weather conditions rather than
assuming overages during critical delay calculations, hourly
observations had to be examined. Only then could a proper weather
impact on delay be developed.
The first analysis was of VFR-1 and VFR-2 weather conditions
validating the actual hours these conditions existed. The same
analysis was conducted for the hourly IFR1. 2, 3, 4 weather
reports. After determining the actual weather conditions that
existed, an analysis was performed to determine It any VFR-2 or
IFR-1 weather conditions met or exceeded the criteria established
by the Federal Aviation Administration (FAA) when they approved
LDA approach procedures at other air carrier airports. Spread
sheets were developed to depict hourly weather conditions for VFR-
1, IFR-l and VFR-2 that meet and do not moot FAA LDA weather
criteria for the years of 1993 and 1994. 2
After analyzing the hourly VFR-2 and IFR-1 weather, It became
obvious there was a significant number of hours that met or
exceeded the FAA's weather criteria that has been used in
establishing LDA approaches. The In depth hourly analysis
confirmed the percent of weather conditions that currently
restrict dual flow operations at SeaTac is over-stated in the
DEIS. To present a true picture of Sea-Tac weather, and
demonstrate how dual flow hours within the existing 2 runway
configuration can be increased, the VFR-2 and IFR-1 weather
reports for each hour were sorted and identified into two new
categories, IFR-1 good (IFR-1 G) and IFR-1 bad (IFR-1B).
They are defined as:
IFR-1G. VFR-2 and IFR-1 weather where the ceiling
is between 2,200 feet and 4,999 feet and visibility
6 miles or more. This weather exceeds FAA LDA
weather criteria approved for SFO and STL airports.
IFR-1B. The remaining VFR-2 and IFR-1 weather where
ceilings are less than 2,199 feet and or visibility
less than 6 miles down to and including IFR-2, 3, and
4 weather conditions. These weather conditions
were determined not suitable for LDA approaches at
Sea-Tac even though FAA has approved lower ceiling
and visibility requirements at STL than has been
defined for IFR-1 G in this study. An interesting
side note, due to the apparent acceptance of LDA
approaches, FAA is considering reducing ceiling and
visibility criteria for LDA approaches. The new
weather criteria, if approved, would increase the
number of hours that dual stream arrival flows
could be conducted at Sea-Tac beyond what is
identified in this report, resulting in even less
delay.
IFR-1 G weather (IFR-1 and VFR-2 that meets FAA LDA weather
criteria) was combined with the VFR-L weather conditions when
analyzing dual stream potential. Our hourly analysis confirmed
that VFR-1 weather conditions exist approximately 66% of the year.
VFR-2, and IFR-1, 2, 3, and 4 account for the remaining 34 % of the
annual weather at Sea-Tac. IFR-1G accounts for approximately 17 %
of the 'poor weather" conditions, with IFR-1B, (which does not
meet the FAA LDA weather criteria) the remaining 17%.
III. FEASIBILITY OF AN LDA APPROACH PROCEDURE AT SEA-
TAC.
The main thrust of this study is to determine if an LDA approach
to runway 16R will allow dual stream arrivals during some of the
44% of poor weather conditions claimed by the DEIS. If LDA
approaches can be conducted a sufficient number of hours per day,
and reduce delays to an acceptable level, construction of a third
runway is not necessary. To determine the actual number of hours
that LDA approaches could be conducted, this study compared IFR-1
G and IFR-1 B weather criteria to the hourly forecast demand
identified in the DEIS. 3
VFR-1 weather exceeds FAA weather requirements for establishing an
LDA approach procedure. Hourly VFR-2 and IFR-1 conditions of the
1993 and 1994 weather data was analyzed and separated into IFR-1G
and IFR-1B, as defined earlier in this report. IFR-1G criteria
was developed by equaling or exceeding the weather criteria
required by the FAA when procedures were approved at San Francisco
International (SFO) and Lambert Field St. Louis International
(STL) airports. Minimum weather requirements for SFO are 2,100
foot ceiling and 6 miles visibility. STL weather requirements are
1,200 foot ceiling and 5 miles Visibility. Instead of utilizing
the weather criteria approved for STL, the IFR-1G weather criteria
was designed to exceed the SFO criteria. Therefore the IFR-1G
weather criteria of a ceiling minimum of 2,200 feet and 6 miles
visibility is more conservative than what has been approved by the
FAA for either SFO or STL.
IFR-1G weather (by definition meets LDA weather criteria),added to
VFR-1 meets or exceeds LDA weather criteria and accounts for
approximately 83% of the year. The remaining 17% of the year only
a single arrival stream can be used in the LDA 16R and ILS 16L
scenario. Later in this study the resulting impact on airport
capacity of the remaining 17% is discussed in detail. Clearly an
LDA approach to 16R plus the planned ILS approach to 16L is a
viable alternative to constructing a third runway at Sea-Tac. It
reduces the 44% of single arrival stream time claimed by the DEIS
to 17%.
The unanswered question is, without a third runway, can Sea-Tac
accommodate the year 2020 forecast utilizing a dual stream LDA
approach 83% of the year.
IV. YEAR 2020 ANNUAL FORECAST AND HOURLY DEMAND.
An hourly analysis of the DEIS 2020 arrival and departure forecast
was conducted. The arrival and departure peaks do not occur in
the same hours. The arrival peak hours significantly exceed the
number of departure peak hours, therefore; arrivals were selected
for detailed analysis. 4 The 2020 arrival forecast concludes that
38% of the time, the arrival demand is less than 24 operations per
hour. The DEIS has identified 1 0 minutes as the 'maximum
tolerable level of total all-weather delay per operation." It
concludes this maximum delay will allow Sea-Tac to maintain an
efficient and profitable air service. The stated goal is to
operate the airport in such a fashion that average delays do not
exceed 6 to 7 minutes per operation. The DEIS claims this reduced
delay goal is desirable and will minimize airline operating costs
and passenger inconvenience.
Using the DEIS acceptable delay factor as a guide the 2020 fleet
mix and forecast volume was exposed to an airport operational
scenario consisting of the two existing runways and dual arrival
streams using ILS 16L and LDA 16R procedures. The airport arrival
operating capacity data identified in the Draft EIS is: VFR-1 with
an hourly arrival maximum of 60, VFR-2 with a 48 per hour arrival
maximum, IFR-1 with a 36 per hour arrival maximum, and IFR-2, 3,
and 4 with a maximum hourly arrival rate of 24.
The 2020 arrival forecast does not exceed the VFR-1 maximum hourly
acceptance capacity of 60 arrivals during any hour of the forecast
period. Therefore, it is assumed that during VFR-1 conditions
(66% of the year), additional arrival delays due to weather
constraints will not occur. Analysis of other weather conditions
such as IFR-1G (weather conditions that meet LDA requirements) was
conducted with the same results as that of VFR-1. That is, during
IFR-1 G dual arrival streams, no additional delays due to airport
arrival rates should be encountered. Further analysis was
conducted to determine the ability of the airfield to accommodate
future arrival demand during those periods of weather (IFR-1 B,
IFR-2, 3, and 4), when only single stream arrivals can be
conducted.
The DEIS indicates that from 1988 to 1993 delays at Sea-Tac have
been reduced from 48,000 hours to 26,000 hours, a delay reduction
of approximately 46%. The DEIS credits the reduction in delays to
several airport improvements and improved air traffic control
efficiency. This reduction in hours of delay was accomplished
even with an increase in annual operations. The annual operations
increased from 316,260 in 1988 to 353,052 in 1994. Examples of
airport improvements cited in the DEIS include: relocation of ILS
runway 16R aircraft hold lines, installation of runway centerline
lights on runway 16L, improved air traffic control monitoring of
traffic flows, improved lighting and signage, and a more
homogeneous fleet mix.
Upon analyzing weather conditions that have been the cause of
airport delays, namely reduced arrival capacity during single
stream arrival periods, it is obvious airport delays are
attributed to reduced capacity associated with poor weather.
Therefore the 46% reduction in delays should be in direct
proportion to improved airport acceptance rates during those
single stream arrival flows. The DEIS states that all the
improvements were directly related to enhancing airport efficiency
and mitigating the reduced arrival capacity associated with single
stream operations. Yet even with the improvements that reduced
the delays, the DEIS does not adjust the hourly arrival acceptance
rates in its current analysis from the arrival rates in 1988 prior
to the identified delay reduction of 46%.
When the DEIS uses the 1988 arrival rate for IFR-2+ in the 1996-
2020 analysis it ignores all of the improvements already made plus
any future improvements that may be implemented during the next 25
years.
The Sea-Tac single stream acceptance rate in 1988 was 24 arrivals
per hour. As previously stated since the airport improvements,
the reduction in delays equal 46%. Therefore; it is reasonable to
assume the single stream arrival rate increased proportionately.
24 operations increased by 46% (24 ops. X 46% = 35 ops.) which is
a substantial increase in hourly acceptance rates. One can
reasonably assume that the airfield will continue to operate in an
ever increasing efficient manner. Accordingly, runway acceptance
rates should increase. FAA Advisory Circular 150/5060, Airport
Capacity and Delay, identifies what hourly operations should be
expected for different runway configurations. The numbers below,
identified as runway capacity arrival expectations, parallel the
hourly runway arrival figures found in the FAA Advisory Circular.
The figures on the right (DEIS Runway Capacity: Arrival
Expectations) represent hourly arrival rates used in the DEIS
study encountered prior to all the airport operational
improvements cited since 1988. Those improvements are the basis
for the 46% reduction in delays. Obviously, the improvements
fostered increased hourly acceptance rates during bad weather.
Without increased acceptance rates, delay reductions of 46% could
not have been attained.
Conditions: Runway Capacity: DEIS Runway Capacity:
Good Weather Arrival Expectations Arrival Expectations
VFR-1 65 + 60
Poor Weather
VFR-2 52-55 48
IFR-1 48-50 36
IFR-2, 3, and 4 36-38 24
Analysis of dual stream capacity (LDA 16R and ILS 16L) concludes
delays can be kept to an acceptable level. Although 46% equals an
arrival rate of 35 per hour, this analysis is based on a single
stream capacity of 36 arrivals per hour which is within the
calculations of runway acceptance rates cited in the FAA Advisory
Circular. In keeping with the improving airport operating
efficiency described in the DEIS, a conservative 36 arrival rate
should easily be attained by the year 2020. When comparing the
airport arrival rate of 36 to the DEIS 2020 Hourly Arrival
Distribution data, those hours that did not exceed the arrival
capacity of 36 ( per the DEIS) were considered to not cause
additional delays and dropped from further review.
The DEIS 2020 Hourly Arrival Distribution chart identifies 8 hours
per day that forecast demand exceeds an arrival capacity of 36 per
hour. Those 8 hours were analyzed using the detailed 24 hour
weather data for December 1993 and February 1994. 5 The purpose
of this study is to prove that with proper instrumentation (LDA
16R and ILS 16L), Sea-Tac can operate in an efficient manner
without having to construct a third runway. To assure credibility
of conclusions formed as a result of this study, December 1993 and
February 1994, were selected for weather computations. December
and February recorded the lowest percentage dual stream weather
condition during the two years of detailed weather analyzed.
Following is a description of the analysis process used in the
forecast demand and detailed weather breakdown that was analyzed.
Detailed weather, December 1993:
9:00 AM Arrival demand is forecast to be 38 operations for
the 9:00 AM hour. For seven days th3 9:00 AM hourly arrival
rate is 36 per hour during the weather conditions that
require a single stream scenario. 2 operations exceed the
arrival capacity for those 7 days; or 14 operations (7 x 2),
have experienced additional delays at that hour during the
month of December, 1993. Using this calculation method the
excess hours of demand in December 1993, are listed below.
9:00 AM 14 operations exceed the monthly arrival rate for
that hour.
10:00 AM 104 operations exceed the monthly arrival rate for
that hour.
11:00 AM 42 operations exceed the monthly arrival rate for
that hour.
1:00 PM 6 operations exceed the monthly arrival rate for
that hour.
3:00 PM 6 operations exceed the monthly arrival rate for
that hour.
6:00 PM 50 operations exceed the monthly arrival rate for
that hour.
7:00 PM 36 operations exceed the monthly arrival rate for
that hour.
8:00 PM 18 operations exceed the monthly arrival rate for
that hour.
A total of 276 operations during that month exceed the 36 hourly
runway operation single flow capability.
Detailed weather, February 1994:
Using the same methodology as described for the December analysis,
the hours of excess demand for February 1994, are listed below.
9:00 AM 26 operations exceed the monthly arrival rate for
that hour.
10:00 AM 88 operations exceed the monthly arrival rate for
that hour. 9
11:00 AM 90 operations exceed the monthly arrival rate for
that hour.
1:00 PM 5 operations exceed the monthly arrival rate for
that hour.
3:00 PM 10 operations exceed the monthly arrival rate for
that hour.
6:00 PM 60 operations exceed the monthly arrival rate for
that hour.
7:00 PM 32 operations exceed the monthly arrival rate for
that hour.
8:00 PM 12 operations exceed the monthly arrival rate for
that hour.
A total of 323 operations during that month exceed the 36 hourly
runway operation
single flow capability.
In the year 2020 the DEIS forecasts annual operations to be
441,600, an average of 36,800 operations per month, or an average
of 18,400 arrivals. Of the 18,400 arrival operations forecast per
month, 276 operations or approximately 1.5% of the total December
arrival demand could encounter some additional delay due to a
single stream arrival flow. For the February arrival demand, the
percent of delay due to a single stream arrival flow is
approximately 1.80/o. When considering the possible inaccuracies
acceptable in long range forecasting, this delay of less than 2%,
is negligible. This low estimate of delay is because the DEIS
claims 44% weather where single stream is required, versus the 17%
identified in the detailed analysis conducted in this study.
Additionally, the DEIS underestimates the success of the past
airport and airspace improvements it identifies as the cause of
the 46% reduction in delays since 1988. Because the DEIS does not
properly credit their contribution to delay reduction the DEIS
underestimates the true hourly acceptance rates at Sea-Tac. When
the cited improvements are properly considered and single stream
arrival rates adjusted accordingly unwanted delays rapidly decline-
Unlike the DEIS conclusion this can be accomplished without the
addition of another runway. Finally, the 2020 arrival peak hours
have a smaller proportion of the 17% single flow arrival stream
weather than the off peak hours.
An annual average analysis was made for 1993 using acceptance
rates of 36 operations per hour for the expected case, and 24
operations per hour for the worst case during non LDA weather.
The annual results also indicate that the acceptance rate is
exceeded less than 1% of the year for the "expected case" and less
than 2% for the "worst case'. The analysis of 1994 weather should
produce similar results. 6
The purpose of this study was to evaluate methods of satisfying
forecast demand versus the airport acceptance capability. During
the preliminary analysis it became obvious that three key issues
drove the focus of this study. The need to analyze the weather in
greater detail to determine specific weather conditions i.e., VFR,
IFR, etc., and when that occurs by hour. Predicated on the
outcome of the detailed weather analysis, could dual stream
arrivals using LDA 16R and ILS 16L with the existing two runway
configuration be a viable solution to demand forecasts. Lastly,
the third and probably most crucial issue was, is the above
mentioned airport configuration compatible with the forecast
demands and possible delays. As in the DEIS an important goal of
this study was to limit delays to an acceptable level.
Without doubt the extensive analysis of the three key issues and
secondary concerns that surfaced all validated the following
conclusions and recommendations.
The DEIS claims to have analyzed ten years of Sea-Tac hourly
weather observations. Upon a review of the conclusions and
assumptions it is obvious that the analysis was not in sufficient
detail to identify when and how often weather conditions really
limit the arrival flow to single stream. A detailed analysis
identifies what hours of the day or night that certain weather
conditions exist. This is especially important when the purpose
of the DEIS is to determine if the airport can accommodate the
year 2020 forecasts with or without the need for a third runway.
The DEIS weather analysis was not detailed enough to give credit
for off peak hours when weather is poor. 7 That oversight
erroneously leads one to believe demand will suffer due to "poor
weather" even though a large portion of inclement weather occurs
during low or non demand periods. This study refutes the DEIS
conclusion regarding the percentage of 'poor weather' and the
ability to conduct dual stream approaches to accommodate forecast
operations.
Those peak hours when arrivals exceed 36 per hour significantly
exceed the number of hours when departures would not be
accommodated without unacceptable delays. Arrivals are exposed
the most delay and are the main thrust of this study.
The detailed analysis of the 1993 and 1994 Sea-Tac annual weather
concludes that the ceiling and visibility impact on single stream
arrivals is only approximately 17% of the year. Annual weather in
the Seattle area is such that ceiling and visibility conditions
that will support LDA criteria equals or exceeds FAA requirements
approximately 83% of the year. This means that dual stream
arrival flows can be utilized to satisfy nearly all the airports
forecast hourly demand. This includes the long range forecast
period of 2020 and the 441,600 annual operations and approximately
38.2 million passengers.
The DEIS annual hourly demand forecast was analyzed with special
emphasis on the following issues.
a. Actual detailed hourly weather observations
b. The Port's runway use plan, and fleet mix, cited in
the DEIS
c. Dual flow capabilities of an LDA 16R and an ILS 16L
arrival plan
d. The impact of single flow when dual streams can not
be used
e. Keeping the airport runway layout at two runways
only
The sum of the analysis of these issues concludes, constructing a
new third runway is unnecessary to reasonably accommodate current
and future (year 2020) operations. The recent airport and air
traffic control improvements have resulted in an significant
reduction in delays and subsequent costs to the airlines and
flying public. There is no reason to think that this efficiency
will not continue and even increase over the years. If all these
gains have been accomplished with the current airport
configuration, then increasing dual flow operational periods by
use of an LDA approach should accommodate the DEIS forecast for
the year 2020.
With weather conditions that equal or exceed LDA criteria (83% of
the year) all that is required is to get the aircraft below the
clouds in an efficient and orderly manner. This can be done.
When aircraft are below the clouds the airport can reasonably
accommodate the volume, including the long range forecasts, with
the current two runway configuration.
V. CONCLUSION
Detailed analysis indicates that a third runway is unnecessary,
and that the DEIS conclusions are based on faulty assumptions.
The Port has not exhausted all alternatives including LDA approach
procedures in an effort to resolve future capacity problems
without constructing a third runway. Equipping the airport in its
present configuration with LDA capability to an existing runway
can reasonably accommodate the activity forecast for the year
2020. LDA approach procedures have implemented at San Francisco
and St. Louis and soon will be at Charlottesville. It proves that
implementing LDA procedures can be accomplished quicker and
cheaper than building an additional runway.
TABLE OF CONTENTS AND SOURCE DOCUMENTS
CONTENTS
Executive Summary
Detailed Study
Glossary
Exhibits
Source Documents
GLOSSARY
Sea-Tac Seattle Tacoma International Airport.
SFO San Francisco International Airport.
STL Lambert Field St. Louis International Airport.
16L The easterly of the 2 parallel runways, south flow.
16R The westerly of the 2 parallel runways, south flow.
DME Distance Measuring Equipment.
EIS Environmental Impact Statement.
DEIS Draft EIS.
ILS Instrument Landing System.
LDA Localizer Directional Aid.
Ops Operations.
Wx Weather Report.
TERPS FAA Handbook, Terminal Instrument Procedures. Visual
Flight Rule Conditions.
IFR Instrument Flight Rule conditions.
VFR-1 Local definition of VFR (ceiling at least 5,000
feet and visibility 5 miles or more).
VFR-2 Local definition of VFR (ceiling between 2,500 feet
and 4,999 feet and visibility 3 miles or more).
IFR-1 Local definition of IFR (ceiling above 800 feet and
less than 2,499 feet and or visibility is less than 3
miles).
IFR-2 All three of these categories. Ceilings from less
than 800 feet down to zero and IFR-3 visibility 2 miles
down to zero. IFR-4 is the worst weather condition.
IFR-4
IFR-1G Weather defined for this study. A combination Of VFR-2
and IFR-1 where the ceiling is 2,200 feet to 4,999 feet
and the visibility is 6 miles or more.
IFR-1B Weather defined for this study. A combination Of VFR-2
and IFR-1, or worse, with a ceiling of 2,199 feet or
less and the visibility is less than 6 miles.
EXHIBITS
2 Sea-Tac Airport LDA Weather Conditions 1993 - (pg
3).
3 a- Sea-Tac Airport Weather Conditions 1993 - (pg 3).
3 b- Sea-Tac Airport Weather Conditions 1993 - (pg 3).
3 c- Sea-Tac Airport Weather Conditions 1994 - (pg 3).
3 d- Sea-Tac Airport Weather Conditions 1994 - (pg 3).
4 Hourly Arrival Distribution, Average Day, Year 2020
- (pg 4).
5 Hourly Arrival and Departure Distribution, Average
Day, Year 2020 - (pg 5).
6 a- Non-LDA Weather Conditions, by Hour of Day,
December 1993 - (pg 7).
6b- Non-LDA Weather Conditions, by Hour of Day,
February 1994 - (pg 7).
7 Annual Operations Exceeding Hourly Acceptance Rate,
Non-LDA Weather Conditions, 1993 - (pg 9).
8 Non-LDA Weather Conditions, by Hour of Day,
January to December 1993 - (pg 10).
SOURCE DOCUMENTS
Sea-Tac Airport Master Plan Update Draft EIS Apr.1995 (select
sections).
U.S. Weather Bureau Service Hourly Surface Weather Observations
Sea-Tac Airport 1993 and 1994.
FAA Technical Center - Sea-Tac Capacity Enhancement Plan Update
Data Package # 1 1 -
FAA approved LDA Procedures - SFO and STL International Airports.
FAA Advisory Circular - Airport Design.
FAA Advisory Circular - Airport Capacity and Delay.
FAA Handbook - Airspace Procedures.
FAA Handbook - National Airspace System Plan.
FAA Handbook - Aviation Capacity Enhancement Plan.
FAA APO 80 - Terminal Area Forecasts.
United States Standards for Terminal Procedures (TERPS).
_______________________________
1 pg. 54-58 Expert Arbitration Panel Transcript dated 5/4/95.
2 Exhibit - a,b,c,d, weather conditions 1993 and 1994.
3 Exhibit - hourly arrival distribution average day year 2020.
4 Exhibit - hourly arrival and departure distribution average day,
year 2020.
5 Exhibit - a,b. non- LDA weather conditions by hour of day Dec.
1993, Feb. 1994.
6 Exhibit - expected case, worst case, annual ops analysis 1993.
7 Exhibit - non-LDA weather conditions by hour of day Jan. to Dec.
1993