NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

0201-20-2301

0201-20-2327

April 30, 1955

NBS REPORT

4072

Development, Testing, and Evaluation of

Visual Landing Aids

Consolidated Progress Report

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

For the Period

January 1 to March 31, 1955

for

Bureau of Aeronautics Projects

TED No. NBS-AE- 10002

TED No. NBS-AE- 10006

TED No. NBS-AE- 10008

TED No. NBS-AE-10011

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Th. 'ubiiHiiM.wl Approved for public release by the

„, t< „ frollllll„d mini ptrniiiiM Hot director of the National Institute of Jardi.Waehington

25, d.c. Such permi Standards and Technology (NIST) -t nu been apaciiito the

cal iy prepared If that on October 9, 2015 rt for Iti own uie,
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Development, Testing, and Evaluation of

Visual Landing Aids

January 1 to March 31, 1955

I. REPORTS ISSUED

Report No, Title

21P-18/55 Electrical Characteristics of the Preproduction Model

of a Cable Test-Detecting Set AN/TSM-11

3900 Development, Testing, and Evaluation of Visual Landing

Aids, Consolidated Progress Report for the Period

October 1 to December 31, 1954

Operational and Technical Requirements, Identification

Lighting of Tall Towers (Daylight Operation) Draft 1

Operational and Technical Requirements, Obstruction

Lighting of Tall Towers (Night and Twilight Operation)

Draft 4.

II. TED No. NBS-AE- 10002. GENERAL RESEARCH, LABORATORY AND CONSULTATION SERVICES IN CONNECTION WITH SPECIALIZED LIGHTING PROBLEMS,

VISIBILITY AND FOG MODIFICATION

a. Visibility Meters and Slant Visibility

Transmissometers ? A visit was made to the plant of the CrouseHinds Company where assistance was given the resident Inspector of

Naval Materiel in the inspection of the 10 transmissometers being

procured by the Navy Aerology Branch.

The revisions of text and illustrations of the transmissometer

instruction manual (NBS Report *2588) have been completed and the

manual sent out for reproduction.

Slant Visibility Meter ; The details of the scan drive have

been completed and tested. Wiring diagrams of the drive have been

made, an intermittently defective capacitor and resistor in the

detector have been located and replaced. The instrument has been

sent to the field laboratory at Areata for installation.

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Brightness Meters ; The ratio of ground to horizon sky brightness has a marked effect on the visual range of objects seen against

terrestrial backgrounds,, for example,, runways and runway markings*

Further exploration of the variations in this ratio with azimuth,,

solar elevation,, type of weather and location* is planned for the

Areata Field Laboratory. To facilitate the work* photoelectric

brightness meters and illumi nometers which will automatically scan

the horizon sky and record the measurements have been designed and

are being constructed*

e. General Laboratory and Consultive Services

Marking of Tall Towers 2 Several meetings of Panels of the AGA

Ad Hoc Group studying the lighting and marking of tall television

and radio towers have been attended* Drafts of the operational requirements for night obstruction lighting and day identification

lighting were prepared for the Ad Hoc Group. After minor changes

these drafts were accepted for forwarding to the AGA Subcommittee.

The day identification lighting is based on the system outlined in

our Progress Report for October 1 to December 31„ 1953 (NBS Report

3136).

Characteristics of Retroreflectors ; The specific intensity

data of 21 colored retroreflective samples have been prepared in

report form and a report has been drafted.

Cable Test Detecting Set s The preproduction unit of the

Cable Test-Detecting Set has been received* tested* and a report

released. This set exceeds all the major specification requirements.

It is approximately 7 times as sensitive as the Model OBB Cable

Locator and has much better interference rejection.

Mirror Guidance System for Carrier Landings s A unit which will

be used to demonstrate several proposed wave-off signals to pilots

landing on the Mirror Guidance System has been designed and is being

constructed.

Computation of the Effective Intensity of Flashing Lights s A

mathematical analysis has been made of the effects of changing the

limits of the integral of the Blondel and Rey relation

on the effective intensity* Ie

o It was found that the maximum value

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of I is obtained when the times tj and are the times when the

instantaneous intensity,, I, is equal to Ie

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Use of this fact will facilitate the specification testing of

flashing lights and provides a reliable means of determining the

visual range of these lights 0 A report covering this work is being

prepared*

Approach-Light System Design ? Technical advice and assistance

has been given members of the Visual Landing Aids Branch in developing the design of an approach-light system for field test at

NAS„ Atlantic City*

V0 TED N0 o NBS-AE-10011, FIELD SERVICE OPERATIONS

a. Airfield Lighting

Approach Beacons t Pilot reaction to the approach beacons has

continued to be favorable* The pilots desire the beacons on for

all approaches at night 0 Most pilots prefer to have the beacons on high intensity until they have located the runway lights and then,

in clear weather,, to have the intensity reduced to the low setting.

In the past these changes in intensity with power on damaged the

relay contacts since frequently the low intensity relay would close

before the high intensity relay had opened. This has been eliminated

by the installation of a suitable switch to control the relays.

Pilot comment has indicated a need for threshold lights of higher

intensity. To meet this need,, 14-inch projectors with 250-watt,

12,5-volt 0 C-8 filament lamps have been installed,

c. Research on Visibility Measurements and Visibility Meters

Transmis some try ; Checks of the total time required for maintenance and scheduled preventive maintenance checks of the transmissometers during this period indicate that approximately 8 hours

per instrument per month is required,

A study has been made of the causes of stray light reaching

the receiver of the transmissometer being used to measure the errors

produced by scattered light. This light was found to be the result

of diffraction around the disc which cuts off the direct light from

the projector. Since this cannot be avoided, all measurements will

be corrected for the increase in reading produced by diffraction.

Slant Visibility Meter s The slant visibility meter has been
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received and the plans for the installation are being made., It is

expected that the installation will be completed by May 1.

Effective Intensity of Flashing Lights ("Strobeacon") afad of

Composite Lights (Slopeline Units) : The effective intensity

data of the "Strobeacon" have been compiled and the reduction of

the data has been completed except for corrections for the angular

size of the light and of the comparison light. The effective intensity of this light is substantially independent of test distance

(except for the effect of angular size). The effective intensity

is about 6000 candles by night and 16*000 candles by day. Application of the Blondel and Key Law to the intensity-time data given

in LAES reports gives an effective intensity of about 9000 candles.

Editing of the draft of the report giving the results of specific

intensity determinations of slopeline units has been completed. The

"size" and "row" factors developed by DeBoer have been applied to

these data. The agreement between our field measurements and DeBoer 9 s laboratory data is good when the visual range of the units is more

than about one-half mile. For very short visual ranges,, our measured

effective intensities lie between the effective intensities computed

from the "size" and "row" factors and approach the intensity of a single lamp of the unit. In general,, when the visual range of a unit

is more than one-half mile* changing the number of lamps in the

unit will produce a proportionate change in the effective intensity

of the unit.

d. Electrical Engineering

Airfield Lighting Maintenance Manual s The introduction to the

trouble shooting section for series circuits has been drafted and

is being edited. The draft of the step-by-step trouble shooting

procedure has been checked and revised. A detailed block diagram

of airfield lighting circuits has been prepared. The preliminary

design of the trouble shooting charts has been completed.

GENERAL

Mr. James E. Davis* Electrical Engineer (Airport Lighting*

GS-9) has been reappointed. He reported for duty March 31. The

complement of the Field Laboratory is again complete. There have

been one or two vacancies since May 1954. Since there are only four

positions* these vacancies have caused considerable delay in the

progress of the work.

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The high-voltage feeder cable to the visibility site deteriorated

to the extent that 3000 feet of it required replacing,,

A number of fogs of short duration occurred during this period.

Tests in these fogs were confined largely to the determination of

the effective intensity of approach beacons and to studies of recognition and detection thresholds.