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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT HSS REPORT

0201-20-2327

January 19, 1954

3046

Visual Landing Aids

Field Service Operation

Progress Report

For the Period

December 1, 1952 to November 30, 1953

Prepared By

C. A. Douglas

J. W. Simeroth

J. E. Davis

Photometry and Colorimetry Section

Optics and Rfetrology Division

To

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

Washington 25, D. C.

NAer Order No. 01400

Project No. TED NBS AE-10011

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, rep Approved for public release by the

unless permission is Director of the National Institute of

25 ,d.c, Suchpem Standards and Technology (NIST)

cally prepared If th on October 9, 2015

n part, Is prohibited

ndards, Washington

iort has been speclflport for Its own use,
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TABLE OF CONTENTS

Paragraph Page

ABSTRACT 1

1 INTRODUCTION AMD CHRONOLOGICAL BACKGROUND 1

2 FACTORS AFFECTING THE CHOICE OF LOCATION 2

2.1 Facilities Needed for Flight Testing 2

2.2 Facilities Needed for Tests From the Ground 3

2.3 General Requirements 3

3 FACILITIES AVAILABLE AT ARCATA AIRPORT 3

3.1 General 3

3.2 Laboratory and Shop Space 3

3.3 Other Space and Facilities 4

3.4 Living Quarters 4

3.5 INSAC Station 4

3.6 Instrument Runway 4

3.7 Visual Landing Aids 5

3.8 Electronic Aids 5

3.9 Construction and Service Facilities Offered 6

by Areata Airport

3.10 Weather Conditions 6

4 INSTRUMENTATION 7

4.1 Transmissometers 7

4.2 Visibility Test Site 7

4.3 Miscellaneous Instrumentation 7

5 WORK IN PROGRESS 8

5.1 Introduction 8

5.2 Field Survey of Visual Landing Aids Systems 8

5.3 Tests of Cable Fault Locating Equipment 11

5.4 Tests of Approach Beacons 11

5.5 Measurements of Photometric Brightness and 14

Illumination

5.6 Comparative Visual Ranges 15

5.7. Atmospheric Transmissometry 16

5.8. Study of Factors Affecting the Determination 17

of Visual Guidance

5.9 Runway Markings 18

6 SUMMARY 18

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TABLE OF CONTENTS (cont.)

*

Page

References

Table 1

Table 2

Appendix 1

Appendix 2

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Hourly Rates for Services Performed by

Humboldt County Department of Aviation

Tests in Fog

Report of ILS Approach

Questionnaire on Runway Marking Configuration at Areata Airport

AERIAL VIEW OF ARCATA AIRPORT

FIELD CABLING AND INSTALLATIONS AT ARCATA

AIRPORT

EXAMPLES OF TRANSMISSOMETER INSTALLATIONS

VISIBILITY TEST SITE

DETAILS OF VISIBILITY TEST 'SITE

DETAILS OF EXPERIMENTAL APPROACH BEACON

TRANSMISSOMETER INSTALLATION FOR SCATTERED

LIGHT TEST

RUNWAY MARKING SYSTEM ARCATA AIRPORT

19

20

21

24

28

ii
Visual Landing Aids

Field Service Operation

Progress Report

December 1, 1952 to November 3Q, 1953

ABSTRACT

This report reviews the progress in the establishment of the

Visual Landing Aids Field Operation and in the testing program con- ducted by that Operation during the period December 1, 1952 to

November 30, 1953,

1, INTRODUCTION AND CHRONOLOGICAL BACKGROUND

In the development and testing of visual landing aids and in

the study of the effects of restrictions to visibility upon the

performance of visual landing aids, there has been a recurring need

for field facilities at which tests and experiments can be conducted

under all visibility conditions. Accordingly, the Airborne Equipment

Division, Bureau of Aeronautics, in their letter of 20 May 1952,

Serial No. 71105, requested the National Bureau of Standards to study

the feasibility of conducting such an operation. Following several

conferences with members of the Visual Landing Aids Section, the

National Bureau of Standards in their letter of June 6, 1952 submitted an estimated cost and personnel breakdown of the contemplated

Field Service Operation. The establishment of the Field Service

Operation was authorized by Bureau of Aeronautics Order NAer 01400

dated September 30, 1952. The project was approved by the National

Bureau of Standards Program Review Board on November 26, 1952,

Immediately after the project was approved, attention was given

to obtaining space and personnel for the Operation. After a study

of possible locations, Areata, California, was selected as the site
for the Operation. On February 2, 1953 a lease with the Department

of Airports, Humboldt County, California, for space at Areata Airport was approved. Personnel actions were started as soon as the

location of the Operation was reasonably firm and were completed in

March 1953, The new personnel reported for duty in late March and

early April 1953. The month of April was devoted to indoctrination

and training of the personnel end to supplying and equipping the

field laboratory. On May 2 all personnel except Mr. Davis left

Washington for Areata, During the latter part of April and early

May, Mr. Davis made a survey of airfield lighting facilities at

eleven Naval and Marine Air Stations.

On May 20 a truck load of instruments, equipment and supplies

from the National Bureau of Standards and the Naval Air Test Center

was shipped to Areata.

On May 25 the Field Operation was activated,

2. FACTORS AFFECTING THE CHOICE CF LOCATION

The following conditions and facilities at the site of the Field

Operation were considered essential.

2.1 Facilities Needed for Flight Testing

Although an extensive flight test program is not planned, the

following features were considered essential in order that the necessary flight testing could be accomplished.

a. A small airport where traffic conditions into and over the

field are sufficiently light to oermit ready installation of test

equipment on the field and to allow flight testing without undue

delays or restrictions because of traffic.

b. Periods where the probability of low visibility is sufficiently great to warrant the assembly of test crews.

c. A radio range station.

d. An instrument runway at least 5090 feet long and 150

feet wide.

e. High intensity approach- and runway-lighting systems.

f. A system of electronic landing aids, preferably both ILS

end GCA.

g.

Refueling and minor repair facilities and hangar space
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2.2 Facilities Needed for Tests From the Ground

a. A location with a high frequency of fogs and restricted

visibility.

b. A level visibility range from which lights and marks can

be viewed* at least 5000 feet in length and preferably much longer.

The range should not deviate from a plane surface by more than three

or four feet. For distances less than 5000 feet, the observation

distance should be continuously variable. For distances greater

than this, continuously variable observation distances are not as necessary and a number of discrete observation stations may be used.

2.3 General Requirements

a. A location with living quarters for the personnel of the

group sufficiently near the test site so that weather conditions at

the site may be readily observed and so that tests may be called at

any time of the day or night with a minimum of time spent in travel.

b. Equipment and personnel available to do by contract the

installation and construction work which cannot be readily done by

personnel of the group.

c. Ready access to the location by commercial transportation.

3. FACILITIES AVAILABLE AT ARCATA AIRPORT

3.1 General

Areata Airport is located approximately 7 miles north of

Areata and 14 miles north of Eureka, California, between D. S.

Highway 101 and the Pacific Ocean. It was the site of the former

Landing Aids Experiment Station. It is now being operated as a commercial airport by the Department of Airports, County of Humboldt, under Revocable Permit NO/ (R) -45432. Figure 1 is an aerial

view of the airport. This airport was selected as the location of

the Field Service Operation because of the unique combination of

available facilities and weather conditions.

3.2 Laboratory and Shop Space

(See figure 2)

The lease with the Department ~f Airports provides for approximately 1000 square feet of office, laboratory, and shop space;
400 feet of warehouse space; garage space for two trucks; a variable

amount of space on the airfield; heat, light, and electric power up

to 3000 kilowatt hours per month. The charge for these facilities is

$250.00 a month. Since the electric power rates are unusually high

in the Areata area, this charge is approximately equal to the cost

of heat, light, and power.

The office and laboratory space consists of four rooms end a closet in the east wing on the first floor of the Operations Building. Sufficient conduit and cable runs are available here to permit

ready connection of control lines to instruments and equipment in the

field. The warehouse space is in one of the larger buildings, is

totally enclosed, and is readily accessible by truck. It has sufficient shelf and bin space for storage of equipment and sufficient

floor space so that shop work can be done on equipment too large for

the laboratory shop.

3.3

Other Space and Facilities

In addition, the Airport has made available to the Operation

photographic darkroom space in the former Administration Building

and all unused cable and duct runs, transmissometer stands, distribution transformers and lighting equipment.

3.4 Living Quarters

Living quarters for personnel of the group are available at the

Airport Apartments approximately a quarter mile from the office.

Those quarters are not government furnished but are rented directly

from the county by the field personnel.

3.5 INSAC Station

A CAA Interstate Airways Communication Station with personnel

on duty 24 hours a day is located in the control tower in the same building as the Bureau offices. The INSAC station makes hourly

weather observations. Weather sequence reports and forecasts are received by teletype. The station acts in an advisory capacity in

directing traffic on the field.

3.6

Instrument Runway

Runway 31 is used as the instrument runway. This runway is

153 feet wide and 6000 feet long. It was recently marked with a
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new system of runway markings. These markings are shown in figures

1 and 8.

3.7 Visual Landing Aids

The instrument runway is equipped with a slopeline approachlight system with transverse bars installed and maintained by the

Civil Aeronautics Administration. There is a high intensity runwaylight system using lights manufactured by the American Gas Accumulator

Company to meet CAA Specification L-819, a semiflush runway lighting

system, and a taxiway lighting system using the V-type gaseous-tube

units developed by the Technical Development and Evaluation Center

of the Civil Aeronautics Administration. The runway and taxiway

lights are maintained by the Airport. The controls for all the

lighting systems are located in the INSAC station and are operated

by that station upon request.

3.8 Electronic Aids

3.8,1 ILS System

The airport has an ILS system installed and maintained by the

CAA consisting of the following:

Localizer with voice .operating on 109.5 megacycles,

located 421 feet beyond the northwest end of

runway 31.

Glidepath with 3° slope, operating on 322,6 megacycles, located 380 feet to the right of the centerline of runway 31 and 1180 feet from the runway

threshold.

Middle-marker beacon, operating on 75 megacycles,

located 3500 feet from the threshold of runway 31.

Outer-marker beacon, operating on 75 megacycles,

located 4.67 miles from the threshold of runway 31.

Middle compass-locator, operating on 233.0 kilocycles,

located at the middle-marker site.

Outer compass-locator, operating on 257.0 kilocycles,

located at the outer-marker site.
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3 . 3.2 R?dio Hange Stations

There is a type MRL 1 ow-frequency range station, call letters

ACV, operating at 209.0 kilocycles, located 3.5 miles at 204° true

from the threshold of runway 31 .

A VOR range, call letters FOT, operating at 114.1 megacycles,

is located at Table Bluff, 22.0 miles from the airport at 901®

true from the threshold of runway 31 .

Both range stations have voice communication through the INSAC

station.

3.8.4 Maintenance of Electronic Aids

The CAA has a maintenance group of three technicians based

at the Airport who are responsible for the maintenance of these

electronic aids.

3.9 Construction and Service Facilities Offered by Areata Airport

In performing the tests and development work falling within the

scope of the Field Service Operation, there are occasional con- struction end installation jobs requiring construction and other

heavy equipment and the services of tradesmen. Because of the infrequent occurrence of this type of work, it is neither practical

nor economical to equip and staff the Field Operation so that the

work can be performed directly. Arrangements have been made to

hove work of this type requiring the use of skilled tradesmen and

special equipment performed by the Humboldt County Department of

Aviation at the rates listed in table 1. Charges are made to the

nearest one-half hour. Since the personnel and the equipment are based at the Areata Airport, the charges for moving to the

location of the work are minimized.

3.10 Weather Conditions

The Areata Airport is one of the foggiest airports in the

continental United States. Data from the Landing Aids Experiment

Station (1) show the following. There are approximately 700 hours

a year during which the visibility is below 1 mile and 1490 hoprs

& year during- which the'* visibility is between 1 and S' miles. The

ferg. season extends from June through November with the highest

Incidence during the months of September and October. The periods

of fog by day and by: night are approximately equal. Most of- the

daylight fogs occur in the early morning or the late evening.
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4. INSTRUMENTATION

4 0 1 Transmissometers

Transmissometers in the approach zone and touchdown zone had

been installed for operational use under the jurisdiction of the

Civil Aeronautics Administration. Arrangements were made to

transfer jurisdiction of these instruments to the Field Operation.

In addition, one transmissometer from the Naval Air Test Center

and one transmissometer and a number of spare components from the

NBS laboratory in Washington were shipped to the field location.

These instruments are now installed, as indicated on figure 2.

These instruments provide adquate measurements of atmospheric

transmission throughout the area in which visibility observations

are made. Use was made of permanent and portable transmissometer

stands already at the airport in making these installations.

Details of some of these installations are shown in figure 3. The

indicators were installed in the laboratory space in the Operations

Building. Two additional automatic sensitivity controls were constructed so that the sensitivity range of all indicators can be

controlled automatically. Signal lines between the field units

were obtained by using existing cable runs where possible and

installing lines where necessary.

4,2 Visibility Test Site

A visibility test site was established approximately 500 feet

from the northern end of the north-south taxiway (figure 4). A

2400-volt feeder and a 5-kva distribution transformer were installed to supply power to the site. An eight-foot-square visibility target and two 25-candle threshold lamps for use as test

controls were mounted at a height sufficient for observing over

the length of the taxiway (figure 5). Calibrated comparison lamps were installed for use in determining the apparent intensities of

flashing sources and for other intensity matches. Platforms were added to the stand to facilitate the installation of test equipment. An instrument shelter was installed at the base of the stand

to house the control equipment.

4.3 Miscellaneous Instrumentation

4.3.1 Brightness Meters

Three portable visual brightness meters, a Macbeth, a LuckieshTaylor, and an SEI, are used for photometric brightness measurements
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in the runway and approach areas* Existing towers in the approach

zone are used to bring the observer up to runway level.

4.3.2 Weather Instruments

The Field Operation has no weather instruments assigned to it.

Routine observations are made by the INSAC station and extra copies

of these observations are prepared for the Field Operation. Installation of recording anemometers, wind direction indicators, and

thermometers at the visibility test site and at other locations

along the visibility range is desirable but has not yet been accomplished.

4,3.3 Communication Equipment

Two-way radio communication is provided between the visibility

test site, the laboratory, and the two vehicles assigned to the

group on an assigned frequency of 164.025 megacycles. A microphone

and speaker from the laboratory station are installed in the INSAC

station so that direct communication may be obtained with that

office.

A tope recorder was obtained on loan from the Airport. It is

used to monitor the radio and other communication facilities during

tests.

5. WORK IN PROGRESS

5.1 Introduction

Because of the uncertainties in the funding and of the duration of this project which existed during the first part of fiscal

1954, the test program has been modified from that originally

planned. The following program was chosen as best adapted to the

circumstances.

The results given below are preliminary results only. Final

results cannot be given until after tests have been made under a wide range of conditions.

5.2 Field Survey of Visual Landing Aids Systems

In response to the request of the Bureau of Aeronautics, a survey of the visual landing aids systems of eleven Naval and

Marine Corps Air Stations on the kast Coast was made to obtain
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detailed data on systems as outlined in Bureau of Aeronautics letter

Aer-AE-lQl, *47164, dated 7 April 1953*. Preparation of a detailed

report has been delayed because of the work load at Areata during

the fog season. However, oral reports of the results of the survey were made to personnel of the Visual Landing Aids Section immediately after completion of the survey.

The findings are summarized as follows:

a. Installation and performance of earth-burial cables,

cable connectors and splices.

Most stations visited were either in the process of installing new cables and runway and taxi lighting systems or had just

completed the installation of new systems. Therefore, it was not

possible to determine trends or common faults in the new type 5000-

volt direct-burial cables. No cases of connector failures directly

attributable to the connectors were encountered. In isolated cases

there has been trouble with conventional splices. Most failures

in the 5000-volt cable were attributed to lightning or to faulty

installation. M.A.C.S. Cherry Point reported several cases where

the lead sheath of the old runway system had been attacked by

chemical action of the soil.

b. Methods of locating or repairing faults in cables.

The most common method of locating faults was by isolation. This method is satisfactory between lights along runways and

taxiways but is difficult and expensive in long feeder lines. Two

stations, NAS Patuxent River and NAS Oceana, used the Model OBB

Cable Detecting Equipment with good results, reporting that faults were located to within a few inches in cable runs over 5000 feet

long. Some experience and training is required before satisfactory

use can be made of the equipment. All stations had available, for

use by airfield lighting personnel, ohmmeters, ammeters (usually

clamp-on type), voltmeters, and "meggers" (500- or 1000-volt).

c. Difficulties encountered in the installation, maintenance,

and operation of equipment other than cables.

Reports of installation difficulties were not readily

available as most installations are made by outside contractors.

The operating difficulty reported most frequently was

the failure of the type M-l lights under jet or propellor blast.

These units are being blown off their mounting clips. In one
-loins tance where the cones were bolted to the clips, a cone collapsed

under jet blast.

Nearly all Operations Officers reported that on clear,

dark nights the type M-l taxiway lights were too bright.

Frequently difficulty in the obtaining of standard items was reported. Much of this difficulty appears to be in finding

the stock numbers for these items. It was apparent that available

current information was not reaching the maintenance personnel

level, A set of current ’’standard" drawings was left at each station to help alleviate this difficulty.

Several control tower operators were not satisfied with

the control panels now in use. They reported a need for a positive method of indicating when a section of the runway lights was inoperative and for a method of changing the taxiway light

pattern without stopping all traffic on the field and then turn- • ing off all taxiway lights so that the change in pattern can be made.

One station felt that the new "D*'-shaped vault should

have an emergency exit in the rear.

Difficulty was reported with 15-kilowatt regulators on new installations when the regulators are operating near full load.

The current regulation is affected by presence in the circuit of

isolating transformers with open secondaries so that the current

increases with the number of open-secondary transformers. The

result is that when about 20% of the lamps have burned out, the

current at the 100% setting is so great that the remainder of the

lamps will burn out.

d. Methods of installing, testing, and maintaining equipment.

Generally there has been no established method for testing and maintaining equipment. Except where one person is assigned

the responsibility of maintaining the airfield lighting system,

testing and maintenance is generally confined to work after a fault

has occurred. At those stations where preventive maintenance checks

are made, most potential faults are located before the fault occurs.

At NAS Oceana, ammeters have been installed in the output

circuit of each regulator. The current through each circuit is

checked daily with the output at the 100% setting. A current above

6.6 amperes in a circuit indicates that some lamps in that circuit

hove failed and that field checks are necessary.
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When the taxiway lighting system has many loops, an open

in the circuit of one loop will extinguish all taxiway lights until

the open loop has been found by a process of elimination and removed

from the circuit. To overcome this difficulty, NAS Quonset Point

has connected a "Thyrite" cutout across each loop so that, when the

loop opens, the "Thyrite" across the loop completes the circuit.

5.3 Tests of Cable Fault Locating Equipment

As requested by Bureau of Aeronautics latter of 24 March 1953,

file reference Aer-AE-191, *40158, a study was made of the feasibility of using the Model QBB Cable Detecting Equipment for locating

faults in airfield lighting cables.

As reported in paragraph 5.2, this equipment is now being used

with good results at NAS Patuxent River and NAS Oceana. The equipment from NAS Patuxent River was taken to all fields visited during

the survey of visual landing aids and demonstrated to the maintenance personnel. All who tried the equipment felt that it would be

very useful and not unduly difficult to operate. The equipment was also used extensively with good results at Areata after the NBS

Operation was established to locate and trouble-shoot the existing

cable runs on the field. Laboratory tests were made of the sensitivity, frequency response, and noise level of the equipment from

NAS'r ,P£TtUxent RiVer. \ On the basis of the field experience and

laboratory tests, modifications to Specification MIL-C-16163

(Ships) covering this equipment were forwarded to the Bureau of

Aeronautics in NBS letters of May 13 and July 2 , 1953.

5.4 Tests of Approach Beacons

5.4.1 Historical Background

It has been shown that under low sun or twilight conditions

the distance at which a runway can be seen may be much less than

the reported visibility. At the same time the brightness of

the background is so high that the runway or approach lights cannot be seen unless the pilot is within the main beam of these

lights. In addition, during periods of darkness when there are moderate restrictions to visibility, the intensity settings of the

approach- and runway-light systems must be low so that the main

beams of the lights will not be glaring. This reduction in the

intensity setting of the system will reduce the light outside the

main beam to an intensity too low to be useful in circling or off-axis approaches. Thus, although the visibility is above the
minimum at which circling approaches are permitted, the pilot may not

find the runway or the lighting system in time to make the correction

required and will miss the approach. These considerations indicated

a need for marking the axis of the runway in such a way that it can

be located and identified from distances at least ns great as the

reported visibility from the time a pilot comes abreast of the system

on the downwind leg of the approach until he lines up with the runway.

To accomplish this we proposed in .1947 the installation of two or three approach beacons along the extended centerline of the runway

at distances of 1090 to 5000 feet from the threshold. The beacons

wore to have a horizontal coverage of at least 180° and a flash

repetition rate sufficiently rapid to provide adequate guidance.

Following this, using design data supplied by the National Bureau of

Standards, the Naval Air Test Center constructed and flight tested

experimental approach beacons. Their tests indicated that the concept was a useful one. ^

The approach beacons were then sent to

the Landing Aids Experiment Station for further development. However, the station was closed before this work was completed.

5.4.2 Field Tests

The following are now being investigated:

a. Optimum Flash Duration and Frequency.

It has been shown that the maximum visual range of a light of constant flux is obtained when the beam spread of the

light in the plane of rotation is a minimum. On the other hand,

under these conditions the flash duration is generally so short in

comparison to the interval between flashes that the guidance furnished by the beacon is decreased. The problem then is to determine the best compromise between flash duration, flash frequency,

apparent intensity, and power consumption. A secondary problem is

the determination of the number of approach beacons and the distances from the runway threshold that they should be located to

provide adequate guidance and freedom from glare.

b. Effects of Glare.

The distance at which the approach beacon becomes

glaring is a function of the vertical angle at which the unit is

viewed, the visibility, and the sky brightness. Knowledge of the

minimum distance at which the light can be viewed without undue

glare is required for determining the minimum distance from the

runway threshold at which a unit may be installed, and in determining whether intensity control is required.
1

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c. Comparative Visual Range.

The visual range of the approach beacon compared with that

of black objects and 25-candle threshold lamps, and with comparison

lamps of known intensity, is required in ardor to determine the

effectiveness of the beacon.

5.4.3 Field Installation

A test approach beacon was constructed by using the base of a beacon and installing on it a turntable with provision for 12 lamps

(figure 6). Lamp holders were obtained for fixtures of the multirow system which had been left at Areata when the Landing Aids Experiment Station was closed. These holders provide a means of adjusting the elevation of the lamps. Power is fed to the turntable

through the slip rings of the beacon base at 120 volts and reduced

to the voltage of the lamps being used by the transformers mounted

on the turntable. A continuously variable autotransformer in the

input to the beacon is used to control the voltage. A system of

relays mounted on the turntable provides for rapid selection of 1,

2, 3, 4, 6, or 12 operating lamps, thus providing flash frequencies

of 12, 24, 36, 48, 72, and 144 flashes per minute. The duration and

peak intensity of the flashes is changed by changing the types of

lamps used or their orientation in the lamp holders.

The beacon was mounted on the tower at the visibility test

site (figures 4 and 5) and viewed from the taxiway. The visual

range of the beacon, the intensity of a fixed light necessary to

match the apparent intensity of the beacon, the visibility (the

visual range of the 3-foot target by day or of a 25-candle lump by

night), the traasmis some ter readings, the amount of glare, and

the quality of guidance were observed.

5.4.4 Results

Results to date indicate that a flash duration of approximately

0,5 second and a flash frequency of approximate ly 72 per minute

provide the optimum balance between guidance and visual range.

These conditions may be obtained by using six 430-watt, 115-volt,

PAR-56 approach-light lamps on a 12-rpm beacon base. Under these

conditions, the visual range of the approach beacon by day is

approximately 1.3 times the visual range of a black object against

the sky. Since the visibility of even r. we 1 loafer ked runway is at

best only about half the reported visibility, the use of the

approach beacons will produce an appreciable increase in the visual

guidance given the pilots. At night the visibility of the beacon
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is 2 to 3 tines the reported visibility (visual range of a 25-candle

light). The mininun distance from the runway threshold at which a unit can be located without undue glare is about 1300 feet.

5.4.5 Future Work

Plans are now being made for the installation of approach beacons

on the extended centerline of the runway at distances of 1000 and

2000 feet from the threshold so that their performance under service

conditions can be evaluated. The frequency of weather conditions

suitable for these tests is high during the winter season at Areata.

5.5 Measurements of Photometric Brightness and Illumination

5.5.1 Night Brightnesses in the Approach and Runway Areas

In computations involving the visual range of runway and approach lights at night the effect of these lights upon the brightness of their background is generally ignored. As the number of

lights in the systems and the power of the units has increased, the

effect of the systems on their background has increased. Surprisingly, there are no data available relating the background brightness

to the fog density and the other parameters affecting it. Measurements of the sky and runway (or ground) brightnesses are being made

in a wide range of visibility conditions. The points from which

these measurements are being made are shown on figure 2. The results to date indicate that the background brightness of the runway

area ranges from 3.1 foot-lambert in clear weather to 0.25 foot1 amber ts when the visibility is below one-eighth mile and the

brightness setting is step 4. The corresponding brightnesses of

the approach area are 1.0 and 5.0 fooi-lamberts, respectively, when

the system is operating on the 130% setting.

5.5.2 Sky -and Object Brightness Under Natural Conditions

It has been shown that the ratio of ground to sky brightness

has an important effect on the visibility of the runway markings

or of the runway. ^ •) Measurements of this ratio are being made in

a wide range of visibility conditions to determine the magnitude of

this effect. It is hoped that these measurements can be used to

prepare a table of factors applicable to various types of weather.

Then, by applying these measurements to routine visibility observations, a more accurate measure of the visual guidance or contact

height may be obtained. Measurements to date indicate that even

in dense fogs the zenith sky brightness is two to three times the

horizon-sky brightness. The result of this is that horizontal
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surfaces are seen somewhat farther than they would be if the sky

brightness were uniform.

5.6 Comparative Visual Ranges

5.6.1 Visual Range of Flashing Lights

The use of gaseous discharge lights with flash durations in the

milii- or micro-second range has been proposed frequently. At times

an exaggerated measure of their effectiveness is obtained by using

the maximum instantaneous intensity of the light in computations

instead of the apparent intensity computed according to Blondel and

Rey's law.

^

In order to eliminate any uncertainties regarding

the effect of field conditions, the visual range of a "Strobeacon"

flash-tube light assembly manufactured by Sylvania Electric Products,

Inc. is being compared directly with the visual range of a black

object by day and a 25-candle lamp by night and with the approach

beacon described in paragraph 5.4. The intensity of a fixed light

which will give a visual range equal to that of the flashing light

is being determined. Tests are being conducted in a wide range

of visibilities.

Results to date indicate that the fleshing light has a visual

range approximately equal to that of a fixed light with an intensity of about 30,090 candles. The visual range of the "Strobeacon”

is approximately equal to that of the approach beacon described in

section 5.4, but because of the short duration of the flashes, it

supplies less guidance.

Similar tests will be made with a Westinghouse flashing approach-light unit when one is obtained.

5.6.2 Visual Range of Slopeline Fixture

The visual range of a unit consisting of a number of closely

spaced lights such as a slopeline fixture is generally greater than

the visual range of a single lamp of the type used in the unit but

is not as groat as a light having an intensity equal to the sum of

the intensities of the lamps in the unit. The cumulative effect

will vary with the angular separation of the individual lights, and

hence with the number of lamps in the unit and the distance the unit can be seen; with the background brightness; and possibly with the

scattering coefficient of the fog. These effects are being investigated under field conditions by finding the intensity of a single light which will give the same visual range as the slopeline
-16-

unit. The slopeline unit and the comparison light are mounted on the

stand at the visibility site (figure 5). These lights are observed

from the taxiway at distances up to the visual range of the slopeline

unit. At each observation station the intensity of the comparison

light is adjusted to match the slopeline unit. Observations have

been made to date in visibilities ranging from 400 to 6200. feet.

5.6.3 Comparative Visual Ranges of Objects and Lights

In the design of systems of visual guidance for use during

hours of daylight, a knowledge of the comparative visual ranges of

objects and lights is necessary. The use of arbitrary values of

threshold constants is not satisfactory in computing the effectiveness of lights as compared to objects because of the large effect

of these values on the intensities determined by computation. The

problem is therefore being studied under field conditions by observing the visual range of the visibility mark and of lights of

known intensity located at the visibility test site.

5.6.4 Visual Ranges Obtained Using Recognition and Detection Thresholds

A study is being made of the comparative visual ranges of objects or lights when recognition and detection are used as the

criteria for seeing. This data will be used in the preparation of

transmissometer calibration curves and in the study of the relation

between laboratory values of threshold and those obtained under ser- vice conditions.

5.7 Atmospheric Transmissornetry

5.7.1 Influence of Field of View of Transmissometer Receiver Upon

Errors in Transmission Measurements

In all measurements of atmospheric transmission made with a telephotometer such as the transmissometer, there are errors introduced because the transmitted light includes some scattered light

which, though radiated by the source, would not reach the receiver

in clear weather. (5) To reduce these errors the field of view of

the transmissometer is kept as small as practicable. In the early

transmissometer installations, baffles were placed between the projector and receiver to reduce this effect. Later the use of baffles

was discontinued because of the inconvenience and expense involved

in their installation and because no significant differences in indicated visibility were observed. A study of the problem by Middleton^ indicates that the problem should have more consideration.

Since any errors will be a function of the particle size distribution
of the fog, a series of measurements in fogs of many types is required. From these measurements it will be possible to determine

whether the cost of installing baffles is warranted.

Two transmissometers are installed on parallel 503-foot baselines 20 feet apart. One transmissometer is installed in the usual

manner (without baffles). The other instrument is provided with

five baffles (figure 7) so spaced that the beam from the projector

and the field of the receiver are restricted to a cylinder 10 inches

in diameter. The chart drives of the recorders of the two indicators are coupled together mechanically so that simultaneous measurements of transmission can be obtained from the two instruments.

The effects of random variations of transmission with time and location are made insignificant by making a continuous record of the

transmission readings of the two instruments and computing the

average of the ratios of these measurements over periods of time

during which the transmission does not vary significantly.

5.7.2 Selective Transmission of Fogs

The present transmissometers use photoelectric cells which

are not spectrally corrected. This is done for £ number of reasons

and is justified when the spectral transmission of the fog is es- sentially uniform. The rapid variations of the transmission of

fogs with time make a study of their spectral transmission difficult. The significance of the effects of selective transmission

on indicated visibility will be studied with the two parallel

transmissometers after completion of the tests of the effects of

scattered light. The two receivers will have photoelectric cells

with different spectral responses and the measurements obtained

will be compared.

5.7.3 103%TM Setting Calibrator

An experimental calibrator for determining the 103% setting

of the transmissometer was constructed at the Bureau and sent to

Areata for field tests. These tests indicated that some minor

revisions in design were needed to increase the range of adjustments and improve the stability of the system. A prototype unit

in which these modifications have been included has been constructed

and is ready for service testing.

5.8 Study of Factors Affecting the Determination of Visual Guidance

Data correlating atmospheric transmittance, sky brightness, etc.

with the visual guidance obtained by the pilot of an aircraft landing
- 18-

under low visibility conditions, are needed* To obtain data of this

type, arrangements were made for the pilots of Southwest Airways to

report the guidance received on ILS approaches. The forms used and

the instructions for using them are included in Appendix 1. The

'data received will be correlated with the readings of the transmissometers in the approach and touchdown areas, measurements of brightness, approach- and runway-light intensity, etc,

5.9 Runway Markings

The instrument runway of Areata Airport has been marked re- cently with a system of runway markings designed by Mr. W. H.

Levings, the Airport Manager. Figure 8 is a photograph of the run- way marked with this system. Pilot opinions regarding this system

and the effectiveness of runway markings in general are being obtained, using the questionnaire given in Appendix 2.

This questionnaire is based upon a questionnaire suggested by

Mr. Levings and has been modified to obtain basic design information

as well as pilot opinion regarding this particular system.

6. SUMMARY

This report has described the facilities of the Field Service

Operation at Areata Airport and has discussed the tests in progress

and the background of these tests. Since no two fogs are alike,

observation or measurements must be made in a number of fogs covering a wide range of fog densities in order to obtain meaningful

results. These measurements are now being made. When sufficient

data are obtained on a particular test, a report covering that

phase of the work will be issued.
References

Annual Reports of the Meteorology Department of the Landing

Aids Experiment Station for 1947, 1948, and 1949.

C. A. Douglas, "Factors Affecting the Relation Between

Reported Visibility and Visibility From Aircraft," MBS Report *2715, August 12, 1953.

Naval Air Test Ceriter Interim Report A1-1/SE203,ET23S-1039,

14 November 1950.

I. Langmuir and W. F. Westendorp, "A Study of Light Signals

in Aviation and Navigation," Physics i, 273-317 (1931).

C. A. Douglas and L. L. Young, "Development of a Transmiss one ter for Determining Visual Range," CAA Technical

Development Report *47, February 1945.

IV, E. K. Middleton, "The Effect of the Angular Aperture of

a Telephotometer on the Telephotometry of Collimated and

Noiicollimated Beams," Journal of the Optical Society of

America, 39, 576T 581 (1949),
Hourly Rates for Services Performed by

Humboldt County Department of Aviation

Classification Hourlv Rate

Carpenter $ 2.25

Plumber n> o e> £m O fc* W

Electrician 2.25

Welder 2.25

Mechanic 2.25

Equipment Operator 2.50

Driver 2.00

Painter O 'oc; Pick-up Truck 3.50

Flat Bed Truck 4 o 00

Heavy Cargo Truck 6.00

(w/Hydraulic Hoist)

Winch Truck 4.00

Welding Machine 3.75

Grader 8.00

Road Roller 12.00

Ditch Machine 12.00

Crawler Crane 12.00

Bulldozer 7.50

Shovel-Overhead Tractor 7.50

Fork Lift C AA, OevO

Cargo Trailer 4.00

Note; All of the above rates include

necessary operator and/or driver.
-21

Table 2

Tests in Fog

(Visibi lity Below Two Miles)

Test Period Tvee of Test"5

Date

1953

Time B C D E

7-3 0430-0615 X

13 0-^1 £

i^ v> X

14 0440-0545 X

22 0450-0630 X

3-6 1615-1715 X

9 0845-1030 X

10 2200-2315 X

11 0845-1045 V

12 0930-1050 X

17 1915-2100 X

18 1515-1710 X

23 1330-1145 X

24 1020-1215 A. 27 0845-1015 X

9-1 0800-1000 X X X

0745-1145 X X A

*3 0445-0545 X

0830-0915 X

2000-2345 X

v-v* -w X

4 0000-0100

0800-0850 X

-8 1600-1645 X

9 0500-0730 X

%r

J*. X

0830-1245 V•/&I X

sr

Su. -11 2315-0145 X

-15 0530-0730 y

0800-1130 X X

-18 0500—0700 X X

0300-0945 X v* •23 1430-1515

£ v/ X

X

* See end of Table for explanation of symbols.

** Additional brightness measurements were made in f

with the other tests. Brightness measurements in vis

two miles have been made on a more extensive schedule

above.

F

og in connection

i bili ties exceeding

than indicated
09 .

Table 2 (cont.)

Tests in Fog

(Visibility Below Two Miles)

Test Period Tvoe of Test*

Date Tims A** B C D E F

i > 9-24 1915-2030 X

27 1340-1415 X

28 9815-0845 X

10-5 1700-1830 X X X

1945-2245 X X

6 0830-1000 X X X

1700-1730 X

1945-2230 X X ye 7 0645-0945 %rA X X

3 1015-1945 X

yrA

27 0715-0930 X X X

1600-1645 X

1900-2130 X X X

28 0800-0930 X X

o> 1 0700-0930 X X X X

11-2 0615-0945 X X X X

3 07.30-1015 JX V X X

1500-1730 X X X X

2330-0245 X X X

4 0330-0915 X

6 0815-0830 X

(Thf* 0830-1200 X X

V

1530-1630 X

24 0815-1145 X X

» r X X

1300-1330 X

1915-2315 X X

27 0810-0830 X

Explanation of Symbols

A, Measurements of ground and sky brightnesses in the runway and

approach areas.

B. Determination of the optimum flash duration and frequency and

the optimum location of approach beacons.
Explanation of Symbols (coat.)

Determination of the effective intensity of Strobeacons.

Determination of the intensity required to produce a visual

range equal to object visibility.

Determination of the apparent intensity of six- and tenlight slopeline lighting units.

Comparison of the visual ranges obtained when detection and

recognition are used as criteria.

Study of the errors introduced in transmission measurements

by scattered light.
•;

_ 1

HEPORT OF ILS APPROACH

Areata, California Date Time Fit,

a/*

104-

Handled controls

on instruments

Handled controls

after contact

Copilot_

Pilot Copilot

Indicate on chart by proper symbol;

Pilot (D Copilot <£> Point approach lights sighted (I) Point contact flight started (f)

oint runway lights sighted (3) Point of touchdown (?)

Humber approach lights first sighted

Pilot Copilot

Number approach lights carried

Pilot Copilot

Number runway lights carried

, Pilo t Copilot^

Approach

Lights

Runway

Lights

Approach lights

Ground plane

Threshold lights

Runway lights

Runway markings

Remarks :

.sity of lights

High OK Low

Guidance

Adequate Inadequate
-25- APPENDIX I (eont.)

REPORT OF WEATHER DURING ILS APPROACH

Date Time Fit. Pilot

Ceiling Top of Fog feet

Visibility Weather

Wind: Direction Speed iHo

Tran smis someter Reading

T-A Range

T-D Range

Background Brightness

Bright O Average Q Dull £3 Twilight Night Q

Approach Light Intensity %

Runway Light Intensity %

Remarks
-26-

APPENDIX 1 (cont.)

Explanatory Notes

for

’'Report of ILS Approach"

This report form is intended to furnish data which will

assist the National Bureau of Standards in studies of the effects

of atmospheric transmission upon the performance of visual landing aids. A copy of the form should be completed for every ILS

approach into Areata Airport. It may be used for approaches

other than ILS when desired. The form should be completed immediately

after a landing or as soon thereafter as possible. Completed forms

should be sent weekly, or more often if they accumulate rapidly, to

National Bureau of Standards, Box 193, Areata, California, or may be

left at the Eureka-Arcata terminal to be picked up there by our personnel.

In order to conserve the reporter’s time, the form was designed

to provide the minimum of information needed. Any elaboration of

this information or of related information by noting comments or observations on the back of the form will be appreciated.

Time : Use the 24-hour clock on Pacific Standard Time.

Chart : The chart on the left of the form is of the approach

zone and runway 31 of the Areata Airport, and is to be used for

locating significant points.

Handled Controls : Check the proper blocks to identify the person

handling the controls during the first part of the ILS approach and

after contact flight is started. This is necessary as there may be differences in the distance at which the lights are seen as a result of the

different duties of the two pilots.

Points Indicated on Chart : The position of the plane at significant

points should be located on the chart by proper symbol and number. The

pilot as designated at the top of the form - not necessarily the person

handling the controls - designates his observations by circumscribing

the numbers locating the points with a circle O . The co-pilot, as listed at the top of the form, designates his points with a diamond A.

Show the approximate position of the aircraft to the left or right of

the center line as well 'as the distance from the runway threshold. As

shown on the form, 1 is the position at which the approach lights were

first sighted; 2 is the pdint contact flight was started; 3 is the

point the runway or threshold lights were first sighted; and 4 is the

point of touchdown. If either pilot or co-pilot should fail to make an observation or if the position of the aircraft can not be determined

approximately, then that observation should be omitted from the chart

and an explanation given in the remarks.
-27“

APPENDIX 1 (cont.)

Number of Lights : Indicate the approximate numbers of approach lights

seen at the time the lights are first sighted, the average number

visible during contact flight, and the average number of runway lights

visible after the threshold is crossed. If there is a marked difference between the number visible in the left and right rows list the

number visible for each row. When most of the system is visible, all, or the fraction of the system, may be indicated rather than the approxi

mate number of lights.

Intensity of Lights ; Indicate in the proper box the opinion of the

pilot handling the controls during visual flight as to the intensity

setting of the approach and of the runway lights with respect to the

desired intensity. Do not indicate the actual position setting as this will be obtained from the control tower.

Guidance s Indicate in the proper box the opinion of the pilot handling

the controls during visual flight as to the adequacy of the guidance

supplied by the lighting systems, by the ground plane, and by the "runway” markings. The ratings given apply to the particular approach and

not to the over-all performance of the system. In rating the lighting

systems consider the purpose for which they were designed. Since the

lighting systems are intended to supply information at distances

greater than objects can be seen, they should be considered as supplying inadequate guidance when the ground plane or runway markings supply

the information at greater distances. Thus, if the markings on the end

of the runway are seen before the threshold lights, the threshold light

should be considered inadequate. Similarly, the runway lights should

be considered inadequate when the runway markings are visible from

greater distances. A brief note under remarks explaining why a given

item is considered inadequate will be helpful.

Remarks ; Include in this section any significant information not

covered by the form and any explanations required to clarify any of the

observations. All missed approaches caused by inadequate visual

guidance should be explained in detail.
-28°

Appendix 2

Questionnaire

on Runway Marking Configuration

at

Areata Airport

I. Identification Information.

(Answer only those questions in this section which are necessary

to describe your flight and previous experience. The other

questions will be completed by airport personnel.)

1. Pilot Rating

2. Date Time

3. Type of aircraft _ _ Operated by

4. Have you made any previous approaches on this runway marking

system?

Circling ________ Straight in None

5. The airports listed below have different types of runway markings. Check those at which you have made approaches or landings.

Oakland (broken center line)

La Guardi a (CAA Standard M. T50-Nl0a)

_________ Los Angeles (TSO-NlO)

II. Appraisal Information.

6. What was seen first: airport buildings . runway

runway lig'nts_ centerline _ threshold markings _____

I edge markings . distance markings .

7. At what distance from the threshold 'were the runway markings

first sighted: mi. : altitude ft
-29-

Appendix 2 (cant,)

8. At -‘jhat distance from the threshold did the runway marking configurations furnish adequate visual guidance : _____ ini . ; altitude _____ ft,

9, Evaluate the information furnished by the configuration by

checking the proper boxes.

UnsatisExcellent Adequate Marginal factory

10. Number in order of usefulness on this approach:

canter line __ edge markers

threshold distance markers

11. Number the airports at which you have made landings in the

order of personal preference of the runway marking configuration.

__ Areata _____

______ LaGuardia _ __

__ __ Los Angeles __ _________

(fek land _

12. Number in order of preference for centerline marking.

_____ solid stripe diamonds

_____ broken stripe _____ none
-30-

Appendix 2 (cont.)

III. Supplementary Information.

13. Check any of the following comments you consider applicable.

Cross out inapplicable words.

Centerline.

_____ Diamonds are clearly defined. _____ Diamonds become indistinct when aircraft is below glide path.

______ Length of each diamond should be (increased) (decreased) (unchanged)

________ Diamonds (are) (are not) a desirable form of centerline marking.

________ Other (explain).

Threshold Markings.

______ Threshold markings are satisfactory without change.

_______ Information regarding runway length (is) (is not) desirable in

threshold markings.

More space between bars is required. _____ (Diminish) (Increase) the (length) (width) of the bars.

________ (Increase) (Decrease) number of bars. _____ Other (explain).

Edge Markings.

Edge markings are (desirable) (not useful).

______ The edge markings (do) (do not) supplement the guidance supplied

by the center line.

________ The width of the edge markings should be (increased) (decreased)

(unchanged)

________ A broken line (is) (is not) preferable to a solid line.

______ Other, (explain).

Distance Markers.

_______ Distance markers (are) (are not) useful.

_______ The shape of the distance markers (is) (is not) readily distinguishable. _____ The distance markers (give) (do not give) an easily interpreted

indication of the distance down the runway.

______ More distance markers (are) (are not) desirable.

.. Other, (explain).

14. Remarks:

i
(cont.

)

1-

Appendix 2

IV. Project Information.

15. Is it your personal opinion that this runway marking configuration is of sufficient value to warrant its use- at other airports?

Yes ______ No

16. If, in your opinion, the entire configuration should not be

adopted, what features of this configuration would you like to

see included? Diamond center line , threshold markings . edge marking s__ distance markers _.

17. Would you prefer to have the same type and size of markings on the

three types of runways (all weather, basic instrument, and VF3)

Yes ______ No __

If this is not economically feasible, which 'would you prefer:

_____ Scaling down the size of all the markings. _____ Eliminating some of the markings. Which? Diamond, centerline, edge markers, threshold markers, distance markers. _____ Using other, simpler configurations for basic instrument

and VF8 runways.

______ Other (explain).

13. In your opinion, should the design of the runway marking configuration consider its utility in VFR as well as IFR conditions?

Yes No _____

19. Remarks

Approach Weather Information

To Be Completed By Areata Airport

1 . Ce i 1 i net _ Ft. 4. 'O o:Q !

. Visibility: Visual Mi. •»Jo i^<3> X Cl TA Mi. 6. Haze

TD Mi

7. Snow

S. Wind: 3. Other

9. Brightness Measurement Foi
'
FIG. I

AERIAL

VIEW

OF

ARCATA

AIRPORT

I

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V

- -V » CONDUCTOR NO 1*1010 WTSTMGMOU'X CAacf) OlRlcT OURIAl

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• • rwaTro m« iranmmvimi un vCMi info (KlfPiumi *wn

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" MANOHOt INOT Au TiMUWNI O MANMOm

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cr

tf

INDICATORS

FIG. 3

EXAMPLES

OF

TRANSMISSOMETER

INSTALLATIONS
.
I

FIG. 4 VISIBILITY TEST SITE

FIG.

5

DETAILS

OF

VISIBILITY

TEST

SITE

»

FIG. 6

DETAILS

OF

EXPERIMENTAL

APPROACH

BEACON

r

FIG. 7

TRANSMISSOMETER

INSTALLATION

FOR

SCATTERED

LIGHT

TEST

FIG. 8 RUNWAY MARKING SYSTEM

AT ARCATA AIRPORT

dr*