NATIONAL BUREAU OF STANDARDS REPORT

io 006

DEVELOPMENT, TESTING, AND EVALUATION OF VISUAL LANDING AIDS

Consolidated Progress Report

For the Period

October 1 to December 31, 1968

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation’s central measurement laboratory,

the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and

provides central national services in three broad program areas and provides central national services in a fourth. These are: (1) basic measurements and standards,

(2) materials measurements and standards, (3) technological measurements and

standards, and (4) transfer of technology.

The Bureau comprises the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, and the Center for Radiation Research.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the

United States of a complete and consistent system of physical measurement, coor- dinates that system with the measurement systems of other nations, and furnishes

essential services leading to accurate and uniform physical measurements throughout

the Nation’s scientific community, industry, and commerce. The Institute consists

of an Office of Standard Reference Data and a group of divisions organized by the

following areas of science and engineering:

Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Cryogenics2—Radio Physics2—Radio Engineering2—Astrophysics2—Time

and Frequency.2 THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to methods, standards of measurement, and data needed by industry, commerce,

educational institutions, and government. The Institute also provides advisory and

research services to other government agencies. The Institute consists of an Office of

Standard Reference Materials and a group of divisions organized by the following areas of materials research:

Analytical Chemistry—Polymers—Metallurgy — Inorganic Materials — Physical

Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides for the creation of appropriate opportunities for the use and application of technology within the Federal Government and within the civilian sector of American industry. The primary functions

of the Institute may be broadly classified as programs relating to technological meas- urements and standards and techniques for the transfer of technology. The Institute

consists of a Clearinghouse for Scientific and Technical Information,3 a Center for

Computer Sciences and Technology, and a group of technical divisions and offices organized by the following fields of technology:

Building Research—Electronic Instrumentation — Technical Analysis — Product

Evaluation—Invention and Innovation— Weights and Measures — Engineering

Standards—Vehicle Systems Research.

THE CENTER FOR RADIATION RESEARCH engages in research, measurement,

and application of radiation to the solution of Bureau mission problems and the

problems of other agencies and institutions. The Center for Radiation Research consists of the following divisions

:

Reactor Radiation—Linac Radiation—Applied Radiation—Nuclear Radiation.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D. C. 20234.

2 Located at Boulder, Colorado 80302.

3 Located at 5285 Port Royal Road, Springfield, Virginia 22151.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

2120411 February 28, 1969 10 006

2120414

2120641

2120653

DEVELOPMENT, TESTING, AND EVALUATION OF VISUAL LANDING AIDS

Consolidated Progress Report to Ship Installations Division

and

Meteorological Division

Naval Air Systems Command

Department of the N avy

and to Federal Aviation Administration

For the Period

October 1 to December 31, 1968

By

Photometry Section

Metrology Division

Institute for Basic Standards

IMPORTANT NOTICE NATIONAL BUREAU OF

for use within the Governme

and review. For this reason whole or in part, is not au Bureau of Standards, Washi

the Report has been specific

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

rgress accounting documents intended

t is subjected to additional evaluation

lure listing of this Report, either in the Office of the Director, National

ar, by the Government agency for which

al copies for its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Development, Testing, and Evaluation of Visual Landing Aids

October 1 to December 31, 1968

I. REPORTS ISSUED

Report No. Title

9886 Circuit Description of a Prototype Cable Fault

Locator.

9958 A Surrmary of Low Visibility Conditions at Areata

Airport.

9964 Development, Testing, and Evaluation of Visual

Landing Aids;, Consolidated Progress Report for the

period July 1 to September 30, 1968.

212.11-45/67 Photometric Measurements of Eight 20A/PAR56Q/3

Clear-Cover Approach-and Runway-Light Lamps

212.11-29/68 Photometric Tests of Two Deck Guide Lights

manufactured by The L. C. Doane Company.

212.11-35/68 Static Load Test of a Flush Approach Light

manufactured by Strong Electric Corporation.

212.11-37/68 Photometric Tests of Twelve Type Q6. 6A/PAR56/3

Runway-and Approach-Light Lamps (Production Run)

212.11-37/68

Supplement.

Supplement. Life Tests of Twelve Type Q6. 6A/PAR56/3

Runway-and Approach-Light Lamps (Production Run)

Memorandum

Report

Gages for Type L-850 Light Base.

Memorandum

Report

Intensity Distribution of a Flash Approach Light

Manufactured by Strong Electric Corporation.

Letter

Report

Intensity Distributions of a Type C-l Runway Light.

10006 2

II. VISIBILITY METERS AND THEIR APPLICATION

Field Testing of Fog Detectors and Visibility Meters .

Several types of fog detectors and visibility meters are being field

tested at the Areata Airport. The testing of these devices is continuing

and much data during rain are being obtained. Work on the report and

evaluation of the fog detectors is underway: this will be a composite

report of all the fog detector devices. The draft of this report should

be completed during the next quarter.

A detailed report of the performance of the instruments during this

reporting period follows.

NBS Atmospheric Backscatter Meter (Shipboard Visibility Meter)

The NBS atmospheric backscatter meter has operated through most of

this quarter, but some maintenance was required. The response of the

thermostat in the electronics box deteriorated to the point where it no

longer controlled the temperature within the designed range of 40 + 3°C.

The thermostat was replaced, but this type thermostat has such a wide

temperature range that adjustment to the proper position is very difficult.

A type of thermostat requiring less critical adjustment is needed. A

commutating relay, K2200, and a photo-silioon-controlled rectifier, Q302,

failed and had to be replaced.

Sane resistors were also changed to new values to obtain more

reliable operation of the relays. The outer surface of some of the

carbon resistors in the lamp-photocell box appear to be deteriorating perhaps because of the ultraviolet radiation from the lamp. A shield to

protect these components may be desirable. Except for the above mentioned

malfunctions, this visibility meter has performed well. Occasionally the

lamp fails to fire for undetermined reasons, but these misfires average

only a few times per day. The response to decreased transmission in rain

shows good sensitivity.

Videograph B Fog Detector.

The Videograph B fog detector continues to perform well. Moving the

recorder from the field into the laboratory was attempted, but, because

of the increase in noise and the possibility of induced voltages damaging

components in the unit, the recorder was returned to the instrument

shelter in the test area. A series of measurements to compare response

against temperature was started to determine if the sensitivity may be

affected by changes in temperature. Apparently, temperature variations

have a minor effect on the sensitivity of the unit, and control of the

10006 3

internal temperature of the unit may be needed. The Videograph B has a wide range of response to atmospheric transmission changes and shews

good sensitivity in the most dense fogs which have occurred. There is a lack of sensitivity for conditions with visibility above five miles.

Adjustments are available to increase sensitivity in these clearer conditions, but, with these adjustments, the fog detection ranges are

inaccurate.

AGA Fog Detector.

The AGA fog detector has continued to function well. After 16

months of operation, this unit has required no maintenance except for one

lamp replacement. There are no arrangements for continuously recording

the response of this unit, but, by comparison with the transmissemeter,

the relay shewing the presence of fog closes under approximately similar

visibility conditions. Previously, the relay closed when transmittance

over a 250-foot baseline went below 0.85. This has now been changed by

adjustment of the instrument so that the relay will close at a transmittance of approximately 0.70, about one-half-mile visibility.

AGA Visibility Meter.

The AGA "tailored-beam" visibility meter has been returned to AGA.

Much useful information was obtained with this equipment. The equipment

originally performed well, but, after some minor malfunctions and repairs,

the earlier performance was not attained. The reason was not determined.

The equipment as tested did not have the desired sensitivity for very

dense fogs, but minor changes in the design could improve sensitivity in

this range. Further evaluation and report preparation will start during

the next quarter.

Hoffman and Edison Fog Detectors .

There has been no further testing of either of these units since

they were removed for malfunctions and the signal lines were used for

other purposes. The sensitivity of response of these devices deteriorated rapidly after operating for one or two months. These units may be

returned to operation at a later date for further testing when signal

lines are available.

Effects of Height Above Ground on Transmission .

Measurements of transmittance at heights of 5, 10, and 15 feet

above the ground have continued. The data are obtained frem three
=
10006 4

transmssameters mounted at these heights covering the same 2 50- foot

baseline. The desired additional data of particular interest are information on the effect of rain on transmission as well as more information

in fog. Evaluation of this data may be started by the end of the next

quarter.

Fog Variability Studies .

During this reporting period at the Areata Airport, the elapsed

time meters have recorded 219 hours of IFR conditions and 57 hours of

runway lights operated at 100 percent intensity. These totals for the

year of 1968 were 1920 and 260 hours, respectively. The report of the

"Sunmary of Low Visibility Conditions at the Areata Airport" has been

issued. Further work on this task will be conducted at a reduced rate

in order to concentrate efforts on airfield lighting tasks.

Transmissometers and Runway Visual Range Equipment .

A demonstration at the plant of the manufacturer of the new

transmissometers and runway visual range (RVR) equipment being procured

by FAA from Solid State Radiation Institute was attended. A conference

with representatives from several government agencies was held in con- junction with the demonstration to determine the suitability of this

equipment for providing RVR information to pilots in Category II and III

conditions, and to standardize the equipment, installations, and use of

information for these conditions. The RVR equipment being procured was

considered suitable for providing the RVR information needed for Category

II operations, but there was considerable doubt expressed by sane of the

attendees that information suitable for Category III operations could be

obtained with this equipment.

MS Drawing for Transmisscmeter Lamp.

An MS drawing has been prepared for the transmisscmeter lamp to

insure that the quality of this lamp is maintained and that the critical

dimensions and the alinement of the beam with the lamp seating plane are controlled. See Figure 1.
'
10006

iI! A

rn

yi

HORIZONTAL PLANE PERPENDICULAR TO SEATING PLANE AND TO VERTICAL

PLANE. VERTICAL (FILAMENT) PLANE

PASSES THROUGH TERMINAL SCREWS

AND IS PERPENDICULAR TO SEATING PLANE.

DASH NO. RATED

VOLTJ

INITIAL WATTSFILAMENT TYPE RATED

LIFE HOURS

AVERAGE

PEAK INTENSITY

(MINIMUM) CANDELAS

BEAM APREAD

AT 100, 000 CANDELAS

DEGREES

MAXIMUM

DEVIATION OF BEAM AXIS FROM MECHANICAL

AXIS

COVER

HORIZONTAL VERTICAL

-1 (a) 6. 0 120 ± 10 C-6 (b) 3, 000 180, 000 1. 5 (d) 3 (d) 1. 5° Clear

(a) FILAMENT TO BE SHIELDED SO THAT NO DIRECT LIGHT FROM THE FILAMENT IS EMITTED FROM THE LAMP

(b) AXIS OF THE FILAMENT TO DEVIATE FROM PARALLEL TO THE FILAMENT PLANE BY NOT MORE THAN 5°. (c) WHEN LAMP IS MOUNTED WITH THE COVER GLASS INSERTED IN A 7. 75 INCH DIAMETER HOLE IN A FLAT PLATE. THE

DIRECTION OF THE PEAK OF THE BEAM SHALL BE WITHIN 1 1/2 DEGREES OF THE NORMAL TO THE PLATE

(d) IN SERVICE THE LAMP WILL BE OPERATED WITH THE FILAMENT AXIS VERTICAL.

DIMENSIONS IN INCHES UNLESS OTHERWISE SPECIFIED, TOLERANCES: DECIMALS ±0. 016. ANGLES ±1°. EACH LAMP SHALL BE PERMANENTLY AND LEGIBLY MARKED WITH THE IDENTIFICATION NUMBER, MANUFACTURER’S TRADE MARK

OR ABBREVIATION OF MANUFACTURER’S NAME. RATED VOLTS, AND WATTS.

PA NAVY AS.

Other OustUSAF

LAMP. INCANDESCENT. PAR-64 BULB. SCREW TERMINAL BASE. TRANSMISSOMETER

MILITARY STANDARD

MS

si!;

PROCUREMENT SPECIFICATION SUPERSEDES MIL-L-6363 DD 672-1

Figure 1.

10006 <o

III. AIRFIELD LIGHTING AND MARKING

Beacon Manufactured by North American Aviation, Inc.

A beacon designed and built by North American Aviation for use in

tests of obstruction lighting of tall TV takers was received frcm the

National Aviation Facilities Experimental Center for intensity distribution checks. The unit contains six 500-watt, 20-ampere PAR-56 lamps

arranged in a circle aimed upward and six similarly arranged pointing

downward. A revolving mirror (with both surfaces reflecting) tilted 45°

frcm its vertical axis generates a flashing beam with a 360° horizontal

coverage and with a flash rate in any horizontal direction of twice the

rate of rotation of the mirror. The 20-ampere lamps were operated at

18.6 amperes, as recommended by the manufacturer. Intensities measured

at 20° horizontal intervals (the vertical angle of traverse was 6.0°)

were as follows:

Intensities (kilocandelas)

Reference Top 6 Lamps Bottom 6 Lamps

0° 320 340

20° 290 350

o

o 290 250

60° 270 310

00 o

o 270 220

100° 280 290

120° 340 340

140° 340 260

"Average" 300 295

It was evident when looking into the beam that the mirror was not

flat, and, as a consequence, all of the lamps were not making their

proper contribution to the total beam intensity. Each of six lamps was

burned in turn and the contribution of each was determined (not to 1%

accuracy; hence, the total of more than 100%)

Lamp Number (arbitrary) Percent Contribution

1 20

2 11

3 28

4 12

5 7

6 24

Total 102

10006 7

It follows that, if each of the lamps were contributing to the

extent of lamp number 3, the intensity of the unit would be increased

about 70%.

The beam width (at points of 50% of peak intensity) in the vertical

direction (one determination only) was about 9.5°.

A letter report will be issued.

In-Runway Visual Approach Slope Indicator (VAST) .

Concern has been expressed regarding the use, by pilots of longbodied aircraft, of the Visual Approach Indicator System (VASIS) when

these aircraft are in the flare attitude. One suggested solution for

this problem is the addition of a third set of bars to the VASIS, upwind

of the present pair of bars, to define a second glide slope. However,

since the addition of more bars to the present VASIS presents some problems, the installation of VASI-type lights in the runway might be

advantageous in presenting the after-flare indication.

A configuration of on-hand components to simulate an in-runway VASI

was assembled at the National Bureau of Standards and photometric

measurements were made of the unit. The lamp was especially made for a short (28-inch) lamp-to-aperture distance. A vertical intensity distribution is shown in Figure 2. NBS Test Report 212.11-1/69 will be issued.

Flush Approach Light Manufactured by the Strong Electric Corporation . A letter report was issued giving the results of photometric tests

(nude before the static load tests) of a flush approach light manufactured by the Strong Electric Corporation, Toledo, Ohio. The unit

contained two 500-watt, single-ended experimental halogen-cycle lamps.

A peak intensity of 19 kilocandelas was obtained. Beam widths (points

of 50% of peak intensity) were 7.5° vertical and 28.5° horizontal (one

determination of each)

Static load tests were made on the unit and reported in test report

212.11-35/68. Both lenses of the unit cracked during the test.

Flush Flasher Approach Light Manufactured by Armglo Corporation .

Photometric imeasurements were made of the smaller of two flush

flasher approach lights manufactured by the Amglo Corporation, Chicago,

model 3051. The energy supplied to the 3/4-inch diameter helical

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10006 3 11

4

3

9

1

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of a X- Semiflush VASI Unit —

Projection: one inch -(- Lamp: PAR-64, 20-ampere, 300 w- Filament: 0. 080 inch ahead of focua'

, o i

Prism angle: 2 Horizontal angle of traverse: 0

Composite

White beam

Red beam

Degrees Down Figure 2 Degrees Up

10006 9

flashtube was 365 watt-seconds (nominal) per flash. The power supply

was performing erratically, so the test was not conclusive. Since the

power supply deteriorated further, it was not possible to test the

larger unit, model 5858.

Figures 3 and 4 give a vertical and horizontal presentation of the

intensity distributions in two planes. Figure 4 was made frcm data

taken at 10° intervals and therefore does not shew the irregularities

of the continuously recorded trace of figure 3. A letter report will

be issued.

Life Tests of Twelve Type Q6. 6A/PAR56/3 Runway-and Approach-Light Lamps

(Production RunJ~i

Twelve Type Q6. 6A/PAR56/3 runway-and approach-light lamps frcm a production run were life tested at rated current. Average life to burnout or to the time when the voltage dropped to 95% of initial voltage of

eleven lamps (one lamp burned out before the test was started) was 798

hours. Federal Specification WL-101 permits a 17% deviation frcm the

stated life (1000 hours) , or an average of not less than 830 hours to

the sample tested. MBS Test Repert 212.11-37/68 Supplement was issued.

Type C—1 Lights with Philips (Netherlands) Lamps.

A letter report was issued giving the photometric measurements of

each of five lamps in a type C-l runway edge light. Four lamps were

made by Philips of the Netherlands and were operated at a current to

make their luminous output 4800 lumens. The fifth lamp, manufactured

by General Electric Company, was operated at 6.6 amperes, it having been

previously determined that its lumen output was 4720 lumens. Peak intensities in one direction of the Philips lamps were 37, 32, 32 and 35

kilocandelas; for the GE lamp, 28 kilocandelas.

Field Tests of Cable-Fault .Locator Developed by NBS .

The testing and evaluation of the Cable-Fault Locator (CFL) have

continued, and a draft of the report was prepared. The CFL works well

for tracing circuits and locating lew-resistance-to-ground faults in

cable buried directly in the ground. For many installations of cable in

steel pipe, the cable could be traced and semetimes faults could be

located, but for other circuits in steel pipe, the results ware unsatisfactory. For open-circuit faults in direct-burial cable, the cable

could be traced to within 50 feet or less of the fault and even up to the

fault in some installations. Under conditions when useful results were

obtained on the tests, the CFL performance was equal to or better than

that of the AN/TSM-11 cable test-detecting set. Except near turns in
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10006 10

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10006 12

the cable, the depth of directly buried cable could usually be determined

accurately with the CFL. The waveform of the output voltage from the

signal generator, which is basically a squarewave, was badly distorted,

depending on the circuit to which it was connected. The tendency towards

distortion was increased with the higher test frequencies and the higher

output voltage settings. The CFL is an inprovement over the AN/TSM-11

in many respects, but these field tests have indicated areas where further improvements may be possible. A report on the CEL will be issued

next quarter.

Airfield Lighting Maintenance Manual .

Following the review of Visual Landing Aids General Service Bulletin

No. 27, Visual Landing Aids Design Standards—Landbased Installations,

and several survey reports, reported last period, lists of types of

lamps and transformers that are currently in use were prepared. The

lamps were listed according to lamp types, fixture specifications, and

light fixture or system. The transformers were listed according to

application, fixture type, and electrical characteristics. These lists

include information on types, specifications, standard drawing numbers,

Federal Stock Numbers, fixture types, electrical ratings, and, when

available, the superseded type, stock number, specification, and standard

drawing number. The lists will be useful for preparing the Airfield

Lighting Maintenance Manual.

Portable Inset-Light Photometer.

A portable wheel-mounted photometer has been completed except for

the installation of the photometer measuring components. The construction of this photometer consists of a bottomless light-tight box (see

Figure 5) that can be positioned over the light to be measured to make

an in-place photometric check of touchdown zone and centerline lights.

By using a folded light path, a measuring distance of approximately ten

feet is used for the photometric test. This distance is considered minimum in order to obtain an accurate measure of the effects of dirt or

moisture on the lens, which diffuse the light beam. A calibration check

can be made of the photometer at any time by switching on a batterypowered reference light built into the unit. By visually observing the

beam position on a translucent plastic window on the photometer, an indication can be seen of the vertical angular elevation of the beam.

The photometric sensing unit will be mounted at the center of the plastic

window, which will also be the center of the inset light beam if the

vertical angle of the beam is correct.

This photcmeter has been designed as a feasibility model for making

spot checks on the centerline inset lights selected at random.

10006

RUNWAY

LIGHT

10006 14

IV. CARRIER LIGHTING AND MARKING

Light with Deep Elliptical Reflector for use as a Deck Floodlight .

Two interior-type fixtures with deep elliptical reflectors were

received, one to accomodate a 500-watt T-24 lamp and the other a 750-

or 1000-watt T-24 halogen-cycle lamp. Photometric measurements will

be made of the units to determine the suitability of the ellipticalreflector-type unit for use as a glare-free deck floodlight.

V. MISCELLANEOUS TECHNICAL AND CONSULTIVE SERVICES

Review of Draft Specifications .

Drafts of the following specifications and reports were reviewed

and the carments were forwarded:

Specification MIL-R-6402B Regulator, Constant;

Current, Taxiway Lighting, Type M-2;

Required Operational Capability (ROC) for Runway Visual Range

(RVR) Data to Support All-Weather Landing Systems;

Development of Transit'd ssoireter Calibration Techniques and

Devices

;

Transmisscmeter Calibration and Alignment; and

Flight Tests and Evaluation of Heliport Lighting for VRF.

Project Foggy Cloud.

The activities of Project Foggy Cloud at the Areata Airport

terminated November 15, 1968. This project was directed by the Earth

and Planetary Division of the Naval Weapons Center, with its purpose

to evaluate methods of modifying warm fog and stratus clouds. Seme of

the results near the end of the fog season appeared promising. A

summary of this activity prepared by the project personnel is included

with this report (see Appendix A) . The NBS Visual Landing Aids Field

Laboratory assistance on this project during this quarter consisted of

a few observations and comments during tests, evaluating possibilities

of fog or stratus during the month of November, and help in loading

and preparing for departure. The present plans anticipate a return to

Areata next spring for more testing during the next fog season.

10006 15

Bureau of Public Roads and Oregon State Highway Department.

John Hegmann, Bureau of Public Roads, and William Zirbes, Oregon

State Highway Department, visited the VLA Field Laboratory at Areata

to discuss devices and means of detecting fog along highways. They are planning a test project for a section of Interstate 5 Highway in Oregon

to ccmpare instrument indications with observations by the Highway

Patrol Officers in determining the presence of fog on the highway

requiring reduced driving speeds. This project may extend over a period

of three years. The problems of sampling errors, maintenance of and

limitations of equipment were discussed. The transmissaneters seemed

the most suitable equipment presently available, but same of the fog detectors may prove suitable for this type use. They were considering an installation of one or more transmissaneters using a 250-foot baseline

for the initial installation.

10006 16

APPENDIX A

FROM: PROJECT FDGGY CLOUD DATE: 11 November 1968

TO: NATIONAL BUREAU OF STANDARDS REF: 143/RSC:dp

POST OFFICE BOX 193

ARCATA, CALIFORNIA 95521

SUBJECT: Summary of Project FOGGY CLOUD

1. Project Foggy Cloud was a field evaluation of methods of modifying

warm fog and warm clouds. The project was planned and conducted by the

Earth & Planetary Sciences Division of the Naval Weapons Center, in

collaboration with the U. S. Army Atmospheric Sciences Laboratory, the

U. S. Air Force Cambridge Research Laboratories and the U. S. Navy

Weather Research Facility. On contract to NWC, personnel of Meteorological Operations, Incorporated, Hollister, California, participated

directly in the project. Other agencies which contributed personnel,

technical support or equipment to the project include the Tactical Air

Command, Air Weather Service, U. S. Army Terrestrial Sciences Center

and Cornell Aeronautical Laboratories.

2. A total of 72 seeding tests and 41 supporting tests were run during

the period 25 March to 10 November 1968. Twenty-five of these tests

were conducted with pyrotechnic seeding agents, 30 with sprayed solution

and 17 with dry powdered agents. Both ground based and airborne seeding

techniques were evaluated for pyrotechnic and spray agents. During each

test, the nature and extent of any cloud modification was measured and

evaluated. Data gathered include standard weather observations; transmissivity; atmospheric soundings; aerial measurement of temperature

dewpoint observations; and droplet-size data. Most of the data have

been reduced to yield a time history of nvaasurements and events before

and after seeding. The most significant result of this project has been

the discovery that a solution of 4 parts ammonium nitrate and 3 parts

urea in 0.78 parts of water has extremely suitable properties for warmfog modification. Although we have not yet developed a completely

reliable technique to disperse warm fog, several airborne tests with

this solution have yielded very encouraging results. It is reasonable

to expect that future work will enable us to specify the unknown details

necessary to engineer an operational fog-dispersal capability suitable

for airport applications.

10006 17

APPENDIX A (CONTINUED)

3. The project was based at the Arcata-Eureka Air Terminal because

of its favorable weather regime, its special instrumentation and its

history of use for projects of this kind. Testing was conducted

principally at or over the airport or in suitable areas close to it.

As has been the case in earlier projects, the cooperation by personnel

of the National Bureau of Standards has once again been outstanding.

We are indebted to Messrs. John Simeroth, James Davis and Janes

Wilkerson for advice and assistance and canpletely voluntary collaboration in the many activities necessary to plan, conduct and evaluate

the tests. These men provided background information and climatological

data, pertinent test transmissivity data and other technical materials

and references. They frequently observed our tests in person, providing

us observations and helpful suggestions in locating tests and observational sites. They loaned us various equipment useful in accomplishing

specific tasks. They relinquished use of our leased office spaces,

without which we could not have operated. All of these activities were

conducted in a spirit of friendly cooperation which is greatly

appreciated.

4. Three reports on the project are planned on a priority time schedule.

Information copies of these reports will be furnished to your office.

(Signed) Richard S. Clark

Richard S. Clark

Field Director

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