ASTM F2429-15(2021)

Standard Terminology Relating to Aerospace Transparent Materials and Enclosures

SCOPE
1.1 These definitions cover generic optical terms which appear in one of more standards relating to aerospace transparent materials and enclosures.  
1.2 The definitions cover, in most cases, special meanings used in the transparency industry. No attempt has been made to include common meanings of the same terms as used outside of the transparency industry.  
1.3 Definitions included have, in general, been approved as standard.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2021
• ICS: 01.040.49 - Aircraft and space vehicle engineering (Vocabularies)
• ICS: 49.020 - Aircraft and space vehicles in general
• Technical Committee: F07 - Aerospace and Aircraft
• Drafting Committee: F07.08 - Transparent Enclosures and Materials

Overview

ASTM F2429-15(2021): Standard Terminology Relating to Aerospace Transparent Materials and Enclosures establishes consistent, standardized definitions for optical terms used in aerospace transparencies and enclosures. Developed by ASTM International under the guidance of globally recognized WTO principles, this standard ensures clear communication and alignment across the aerospace sector when referring to transparent materials, such as windscreens, canopies, and windows.

The terminology defined in ASTM F2429-15(2021) is designed for use within the transparency industry-covering specialized meanings that are critical for aerospace applications. By providing a reliable reference, the standard supports manufacturers, designers, engineers, and regulatory bodies with precise language for quality assurance, compliance, and performance evaluations of aerospace transparencies.

Key Topics

ASTM F2429-15(2021) addresses a comprehensive set of terms related to the optical characteristics and testing of aerospace transparent materials, including:

• Angular Deviation: The displacement angle of a light ray passing through a transparency, impacting how objects are viewed from inside the aircraft.
• Birefringence: The phenomenon where a light beam splits into two when passing through certain transparent materials, potentially creating visible color patterns known as rainbowing.
• Crazing: Occurrence of micro-cracks near or beneath the surface, which can reflect light and impair visibility.
• Design Eye: A reference point used in cockpit or canopy design for visual and anthropometrical optimization.
• Distortion and Grid Line Slope: Nonlinearities in object appearance due to transparency imperfections, measured using grid lines for optical evaluation.
• Haze and Halation: Scattering of transmitted light, causing reduced clarity and visual contrast for pilots.
• Multiple Imaging and Secondary Images: Occurrences of duplicated images due to internal reflections or imperfections.
• Transmission Coefficient: A measure of the transparency's efficiency in transmitting radiant energy.

These terms provide clarity and technical specificity necessary for evaluating, specifying, and certifying transparent aerospace components.

Applications

ASTM F2429-15(2021) delivers significant benefits across the aerospace industry, facilitating:

• Product Specification and Procurement: Ensures accurate communication on optical requirements for windscreens, canopies, and windows in both military and civil aircraft.
• Testing and Certification: Provides standardized terminology that underpins quality assurance testing, regulatory compliance, and third-party certification.
• Research and Development: Informs materials scientists and engineers developing new transparent materials with reference terms for laboratory and field studies.
• Maintenance and Inspection: Equips technicians with precise vocabulary for identifying, diagnosing, and reporting defects like haze, distortion, or crazing during service and repair.
• Training and Documentation: Supports consistent aerospace training programs and technical documents, improving cross-team understanding and operational safety.

Adopting this standard plays a key role in harmonizing expectations and results throughout the supply chain and lifecycle of aerospace transparencies.

Related Standards

For comprehensive understanding and implementation of best practices in aerospace transparency, consider these related ASTM standards:

• ASTM D1003: Test Method for Haze and Luminous Transmittance of Transparent Plastics
• ASTM F2156: Measuring Optical Distortion in Transparent Parts Using Grid Line Slope
• ASTM F1165: Measuring Angular Displacement of Multiple Images in Transparent Parts
• ASTM F1316: Measuring the Transmissivity of Transparent Parts

Additionally, relevant industry documents such as AL-TR-1993-0036 (Definitions of Terms Relating to Aircraft Windscreens, Canopies, and Transparencies) provide further insights and technical background.

ASTM F2429-15(2021) serves as a foundational reference for anyone working with aerospace transparent materials, promoting accuracy, consistency, and technical excellence globally.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2429 − 15 (Reapproved 2021)
Standard Terminology Relating to
Aerospace Transparent Materials and Enclosures
This standard is issued under the fixed designation F2429; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope which have been known to appear in transparencies as
rainbowing or the apparent random dispersion of light into
1.1 These definitions cover generic optical terms which
its component colors.
appear in one of more standards relating to aerospace trans-
parent materials and enclosures.
crazing—theoccurrenceofverysmall,localized,micro-cracks
at or under the surface of, but not extending entirely through,
1.2 The definitions cover, in most cases, special meanings
a transparent material, which act like tiny mirrors that reflect
used in the transparency industry. No attempt has been made to
light in unwanted directions.
includecommonmeaningsofthesametermsasusedoutsideof
the transparency industry.
design eye—the reference point in aircraft design from which
1.3 Definitions included have, in general, been approved as all visual or optical anthropometrical design considerations
standard. are taken.
1.4 This international standard was developed in accor-
distortion—the rate of change of angular deviation across the
dance with internationally recognized principles on standard-
transparency, usually characterized by grid-line slope, result-
ization established in the Decision on Principles for the
ing in the non-linear mapping of objects viewed through the
Development of International Standards, Guides and Recom-
transparency.
mendations issued by the World Trade Organization Technical
grid line slope—anopticaldistortionevaluationparameterthat
Barriers to Trade (TBT) Committee.
compares the slope of a deviated grid line to that of a
2. Terminology
non-deviated grid line, which is expressed as a ratio such as
1 in 8 or 1 in 20 (the visual optical quality improves as the
2.1 Definitions:
second number of the ratio gets larger).
angular deviation—the angular displacement of a light ray
from its original path caused by non-parallelism of opposite
halation—the scattering of light by the transparency into the
surfaces as it passes through a transparent material, which is
viewer’s line-of-sight reducing the perceived contrast of
expressed in units of angle (degree, minutes of arc, millira-
external objects, also referred to as haze.
dians) and is a function of the angle of incidence at each
haze—the percent of transmitted light that is scattered so that
surface of the material and the index of refraction of the
its direction deviates more than a specified angle from the
material.
direction of the incident beam, resulting in the reduction of
angular displacement—the angular separation of the second-
contrast of objects viewed through the transparency.
ary image from the primary image as measured from the
multiple imaging separation—the angular separation of pri-
design eye position of a transparency.
mary and secondary multiple images as measured from the
binocular disparity—the difference in angular deviation be-
design eye position.
tween two light rays passing
...