Appendix A A-6 documents methods and calculations, and must document and use scan-failure protection devices.
A.14.1. Considerations for Multiple Visible CW Laser Beams Aimed Within the Same Area For a configuration that aims multiple lasers in the same direction, all of which emit visible wavelengths (from 400 nm to 700 nm), consider the following before completing cell 12a.
Example: Multiple lasers on a stage projecting over the audience into the same area of airspace requiring protection.
• Simplest, most conservative analysis.
o In cell 12a, enter the data for the laser with the highest power. All other lasers will have a shorter hazard distance.
o In cell 12c, enter “1” as the Visual Correction Factor (VCF).
o Notes for this approach follow.
▪ The pre-corrected power (PCP) and the Visually Corrected Power will be the same as the power from the highest-power laser.
▪ Because of no allowance for the beams’ visibility, the SZED, CZED, and LFED distances will be longer than analyzing each laser separately.
• Analyze each laser separately: This analysis will determine which laser beam has the longest NOHD, and which has the longest LFED.
o For each laser projector, determine the NOHD, SZED, CZED, and LFED. Attach documentation showing the data and calculations. See Appendix B for an example.
o Cells 12a and 14a: Enter the data for the projector with the longest NOHD.
o Cells 12c, 14b, 14c, and 14d: Enter the data for the projector with the longest LFED.
A.14.2. Section 12a. Laser and Beam Characteristics Laser type: Enter the lasing medium, e.g., CO2, copper-vapor, diode, or Nd-YAG.
Laser hazard class: Enter the hazard class for the laser, e.g., Class 2, Class 3R, Class 3B, or Class 4.
Power: If a continuous wave laser, enter the maximum power in watts (W). If a repetitively pulsed laser, enter the average power in watts (W).
Pulse energy: If a single pulse or repetitively pulsed laser, enter the pulse energy in joules (J).
Appendix A A-7 Pulse duration: If a single pulse or repetitively pulsed laser, enter the pulse duration in seconds
(s).
Pulse repetition frequency: If a single pulse or repetitively pulsed laser, enter the pulse repetition frequency in hertz (Hz).
Beam diameter and divergence: Provide the diameter using the 1/e peak-irradiance points in centimeters (not millimeters). The divergence is the full angle given at the 1/e points in milliradians (mrad). If measuring the diameter or divergence at the 1/e2 points instead of 1/e, multiply by 0.707 to convert to 1/e diameter or divergence.
NOTE: Diameter and divergence measurements can be complex. If necessary, use conservative (smaller diameter or smaller divergence) simplifications.
Wavelength(s): Based on the number of wavelengths and their relation to the visible spectrum, use the following information to assist with determining what information FAA requires.
• Single-wavelength laser beam: For a laser emitting a single wavelength:
o Enter the wavelength in nanometers (nm) in 12a.
o If the emitted wavelength is:
▪ Within the visible range (400 nm to 700 nm): Enter “2.6” as the MPE value in 12b and enter the results of the visual effect calculations in cell 12c.
▪ Not within the visible range: Determine the MPE value as described in paragraph A.14.2. and enter the value into cell 12b. Enter “N/A (nonvisible laser)” in all cells of the applicable column of section cell 12c.
• Multiple-wavelength laser beam: For a laser simultaneously emitting multiple wavelengths in the same beam (from the same aperture), see Appendix C.
A.14.3. Section 12b. Maximum Permissible Exposure (MPE) Value Provide MPE calculation results in the applicable cell, expressed in milliwatts per square centimeter (mW/cm2) or joules per square centimeter (J/cm2). For convenience, the tables in Appendix B provide simplified, conservative MPE values. If a proponent requires less conservative values, use the ANSI Z136 series of standards or other established methods. If using a method other than the values in Appendix B, document and attach the approach and results when submitting the form.
NOTE: Exposure duration Unintentional laser exposure to the eye of a person in an aircraft is not estimated to last more than 0.25 seconds based on various factors including the human aversion response (for visual lasers) and the natural relative motion between the beam and aircraft related to wind and other
Appendix A A-8 stabilization issues. The analysis in this document applies to laser wavelengths between 400 nm and 1050 nm for exposures less than 0.25 seconds. This analysis also provides conservative results for wavelengths from 1050 nm to 1400 nm.
If the potential exposure may last for an increased duration or a proponent desires to complete a more precise analysis (e.g., wavelengths from 1050 nm to 1400 nm), refer to the ANSI Z136 standards for additional analysis techniques. Document and include the standards’ MPE exposure limits and calculations with the submission.
A.14.3.1. MPE: Single Pulse Laser Use Table 1 for lasers that produce a single pulse of energy with a pulse width less than 0.25 seconds. Enter the MPE per pulse value in joules per square centimeter (J/cm2) in cell 12b.
A.14.3.2. MPE: Continuous Wave Laser Determine if all wavelengths of a continuous wave laser beam are in the visible spectrum (400 nm to 700 nm).
• If all wavelengths are in the visible range, enter “2.6” in cell 12b.
• If one or more wavelengths are not within the visible range:
o Record all wavelengths on a separate document per A.14.1., Section 12a, Laser and Beam Characteristics.
o Use Table 2 to find the MPE for each wavelength.
o Calculate the NOHD for each wavelength per A.16.2.1., Slant Range (NOHD).
o Enter the MPE value for the wavelength with the longest NOHD in 12b, and use this MPE value for the visual effect calculation values in 12c and the remainder of section 14a.
A.14.3.3. MPE: Repetitively Pulsed Laser Some repetitively pulsed lasers can produce hazards greater than CW lasers with the same average power. Treat the following lasers as CW lasers, use the instructions in A.14.2.2, and enter the MPE value in the repetitively pulsed column:
• 400 nm to 1050 nm: PRF greater than 13 kilohertz (kHz).
• 1050 nm to 1400 nm: PRF greater than 6.5 kHz.
NOTE: The most restrictive MPE for a repetitively pulsed laser is determined from choosing the most conservative MPE considering Tables 1 and 2. The PRF values provided only apply for a
0.25 s exposure with individual pulse widths less than 5 µs for wavelengths from 400 nm to 1050 nm and less than 13 µs for wavelengths from 1050 nm to 1320 nm.
Appendix A A-9 For the purposes of this form, a laser with a PRF of equal to or greater than one hertz is a repetitively pulsed laser. These lasers can produce an additional hazard greater than that of a single pulse or continuous wave laser. The MPE calculation for repetitively pulsed lasers uses its PRF, designated MPEPRF. Determine the MPEPRF using either the per-pulse energy or the average power.
This document provides a simplified method for calculating the MPEPRF for average power with wavelengths in the visible and infrared region (ANSI Z136 series can provide a less conservative value in some cases). Although designated MPEPRF, enter the value in either the “MPE” or “MPE per pulse” cells of the repetitively pulsed laser column (FAA only requires one of the two MPEs). Use the following simplified methods to determine the MPEPRF.
• Ultraviolet wavelengths less than 400 nm: Reference the ANSI Z136 series. Enter the MPE value in cell 12b (“MPE per pulse” row).
• Visible and infrared wavelengths up to 1050 nm. For a laser with a PRF:
o Less than 13 kHz: Use Table 1 to determine the MPE per pulse in J/cm2 and enter the value in cell 12b (“MPE per pulse” row).
o Greater than 13 kHz: Evaluate as if a CW laser. Use Table 2 to determine the MPE in mW/cm2 and enter the value in cell 12b (“MPE” row).
• Infrared wavelengths from 1050 nm to 1400 nm. For a laser with a PRF:
o Less than 6.5 kHz: Use Table 1 to determine the MPE per pulse in J/cm2 and enter the value in cell 12b (“MPE per pulse row”).
o Greater than 6.5 kHz: Evaluate as if a CW laser. Use Table 2 to determine the MPE in mW/cm2 and enter the value in cell 12b (“MPE” row).
• Infrared wavelengths greater than 1400 nm: For an exposure to a repetitively pulsed laser at these wavelengths, a PRF of just a few hertz results in a more restrictive CW MPE than the pulsed MPE. The MPE that indicates the greatest hazard determines what MPE to enter into cell 12b. Fill in the appropriate “MPE” cell in the Pulsed column, indicating whether the MPE is in J/cm2 or mW/cm2.
NOTE: The simplified methods of Table 2 use the average power to determine the MPE in mW/cm2. Using other methods, it is possible to use the pulse energy to determine the MPE per pulse in J/cm2.
A.14.4. Section 12c. Visual Effect Calculations Non-visible lasers: If the laser has no wavelengths within the visible range (400 nm to 700 nm), enter “N/A (non-visible laser)” in all three cells of the appropriate column of section 12c and proceed to section 13.
Appendix A A-10 Visible lasers: For any laser emitting wavelengths within the visible range (400 nm to 700 nm), proponents must submit visual effect calculations to assist FAA with its evaluation of laser beams bright enough to distract or interfere with a crewmember’s vision, e.g., glare or afterimage. To reduce the risk of distraction or interference, FAA established the following areas wherein crewmembers should not encounter light greater than the values listed.
• Sensitive Flight Zone: 100 microwatts per square centimeter (µW/cm2).
• Critical Flight Zone: 5 µW/cm2.
• Laser-Free Zone: 50 nanowatts per square centimeter (nW/cm2).
Because perceived brightness varies with wavelength (e.g., a green laser appears brighter to the human eye than a red or blue laser of the same power), proponents can apply a visual effect correction factor if desired. This correction factor has the result of allowing more power for red and blue beams than for green beams of equal power and divergence.
A.14.4.1. Determine the Pre-corrected Power (PCP).
The PCP is the total power (sum) of all visible wavelengths. The PCP calculation method depends on the laser’s mode of operation.
• Single Pulse: Multiply the pulse energy (in joules) stated in cell 12a by four and enter the value.
NOTE: This technique averages the pulse’s energy over the 0.25-second maximum pulse duration, and is a conservative approximation of the visual effect of a pulse. If proponents use less conservative calculations, they must document and attach the methods and calculations.
• Continuous wave: Enter the total power (sum) of all visible wavelengths. If the laser emits only visible wavelengths, this will be the same as the maximum power entered in cell 12a.
• Repetitively pulsed: Multiply the pulse energy (in joules) by the pulse repetition frequency (hertz) stated in cell 12a and enter the value.
Appendix A A-11 A.14.4.2. Determine the Visual Correction Factor and Visually Corrected Power.
Use one of the following methods to provide the VCF and the Visually Corrected Power of the laser.
• Simplest/most conservative analysis.
o VCF: Assume no correction factor and enter “1.0 (assumed).”
o Visually Corrected Power: Enter the same value as the PCP.
• Single-wavelength beam.
o VCF: Enter the appropriate value from Table 3.
o Visually Corrected Power: Multiply the VCF by the PCP and enter the resulting value.
• Multiple visible wavelengths: Choose one of the two following methods and enter the resulting value.
o Make a simplifying, conservative assumption.
▪ VCF: Use Table 3 to determine which wavelength has the largest factor (is the most visible), and enter the value.
▪ Visually Corrected Power: Multiply the VCF by the PCP (the sum of all visible wavelengths) and enter the resulting value.
o Analyze each wavelength’s power and VCF individually to find the overall VCF and the visually corrected power. There are two methods to perform this calculation.
▪ Software calculation: Use laser safety software with the ability to enter separate wavelengths and powers for a single laser beam. The software should provide a total VCF calculation for the combined wavelengths and the Visually Corrected Power calculation for the beam.
NOTE: Include attachments (and list in cell 7b) of screenshots or printouts showing the wavelength and power inputs and the software’s resulting VCF and visually corrected power values. Ensure completion of section 15, listing the software name and version.
▪ Manual Calculation: Attach a spreadsheet or worksheet showing the steps of the following calculations:
• For each visible wavelength, list the power at that wavelength.
Sum the listed wattages and enter than number as the PCP in cell 12c.
Appendix A A-12
• For each visible wavelength, consult Table 3 and list the VCF of the wavelength.
• For each visible wavelength, multiply that wavelength’s power by the VCF of the wavelength. This provides the visually corrected power for that wavelength.
• Add all visually corrected powers for all wavelengths together and enter this as the visually corrected power in cell 12c.
• Divide the visually corrected power by the PCP to obtain the overall VCF for the laser beam. Enter this as the VCF in cell 12c.
NOTE: Include attachments (and list in cell 7b) showing the wavelength and power inputs and the resulting VCF and visually corrected power values. Ensure completion of section 15, describing the method used.
Example: Manual calculation
• For each visible wavelength, list the power at that wavelength. Sum the listed wattages and enter that number as the PCP in cell 12c.
o A laser has three visible wavelengths: 8W of 630 nm (red), 4W of 520 nm (green), and 10W of 450 nm blue.
o The laser has a total power of (8 + 4 + 10) 22W of visible light. Enter “22” in cell 12c as the PCP.
• For each visible wavelength, consult Table 3 and list the VCF of the wavelength.
o 630 nm has a VCF of 0.2653, 520 nm has a VCF of 0.7092, and 450 nm has a VCF of 0.0380.
o Document the VCF for each wavelength.
• For each visible wavelength, multiply that wavelength’s power by the VCF of the wavelength. This provides the visually corrected power for that wavelength.
o Red: 8W × 0.2653 = 2.1224 visually corrected watts o Green: 4W × 0.7092 = 2.8368 visually corrected watts o Blue: 10W × 0.0380 = 0.380 visually corrected watts
• Add all visually corrected powers for all wavelengths together and enter this as the visually corrected power in cell 12c.
Appendix A A-13 o Add the three visually corrected watts results together (2.1224 + 2.8368 +0.38) to obtain the visually corrected power of 5.3392 watts.
o Enter “5.3392” in cell 12c for visually corrected power.
o Explanation: Although the laser in this example outputs 22 total watts, the human eye perceives the laser to have the same brightness as a 5.3392 watt laser emitting at the 555 nm wavelength (perceived as brightest by the human eye).
• Divide the visually corrected power by the PCP to obtain the overall VCF for the laser beam. Enter this as the VCF in cell 12c.
o Divide the visually corrected power by the PCP (5.3392 / 22) to obtain the overall VCF for all visible wavelengths of 0.2427.
o Enter “0.2427” in cell 12c for VCF.
A.15. Section 13. Beam Direction(s) Use Section 13 to enter the beam(s) elevation angle(s), direction(s)/azimuth(s), and specify the azimuth source.
If the beam can move to multiple locations (for example, it rotates or is scanned) or if there are multiple lasers emitting beams in similar directions and angles (e.g., a laser show from an outdoor concert stage), FAA can evaluate the possible beam locations as a single configuration.
Enter the maximum and minimum elevation angle of the beams, and the widest spread in azimuth of the beams. FAA will evaluate the entire area of this configuration as protected airspace where any beam could project at any time.
If lasers are widely separated at the geographic location listed on page one of the form (reflected in section 11) or there are lasers aimed in different/non-overlapping directions, each laser or group of lasers is a different/separate configuration. Complete a Laser Configuration Worksheet (page two of the form) for each configuration.
13a and 13b. Enter the beam projections’ minimum and maximum elevation angles (pointing directions) in degrees of the beam projections for this configuration only.
13c. Azimuth and type of north
• Azimuth o Fixed beam: Enter the azimuth on which the beam will project.
o Moving beam (e.g., rotating, scanned, or aimed): If the beam will move horizontally during the operation, enter the movement range in degrees; e.g., “20° to 50°.”
Appendix A A-14 NOTE: Moving beams FAA considers east as 90°, south as 180°, west as 270°, and north as 360°. Enter degrees from smallest to largest moving clockwise, otherwise FAA will interpret the beam rotating everywhere except where intended. Example: An entry of 10° to 350° means the proponent plans to rotate within a total of 340°. If planning to rotate within 10° (either side) of north, enter 350° to 10°.
For some configurations, FAA may need additional information concerning the beam direction,
e.g., the laser is mounted on a moving aircraft or spacecraft and/or the beam projects downward.
• Type of north: Select true or magnetic north.
o Using a compass: If a proponent determines the azimuth degrees or if control measures will use a compass, check the “Magnetic north” box in cell 13c.
o Not using a compass: If a proponent determines the azimuth degrees using a map or other method and if control measures do not use a compass, check the “True north” box in cell 13c.
13d. Magnetic declination (degrees)
• If a proponent checked the “Magnetic north” box in 13c, enter the geographic location’s magnetic declination (or magnetic variation) in degrees from true north, e.g., 11°west.
• If a proponent checked the “True north” box in 13c, enter “N/A” (not applicable).
A.16. Section 14. Protection Distancesi There are four important distances to consider when evaluating the safety of a proposed outdoor laser operations. Each of these calculated distances enhances safety by minimizing the potential exposure of crewmembers to laser light.
NOTE: The ANSI Z136 series of standards contains extensive methodology on determining hazard distances. FAA, in collaboration with SAE International, derived all equations from ANSI Z136.1.
The NOHD relates to the potential risk of permanent physical injury (e.g., the eye). The other three distances relate to temporary visual effects that could distract a person or interfere with a person’s performance of critical tasks. A brief definition of each follows, with additional explanation found in the glossary (Appendix F).
Appendix A A-15 Nominal Ocular Hazard Distance (NOHD)
• Distance (from the laser source to this defined distance) over which it is necessary to protect the safety of a crewmember’s eyes.
• Considered for all lasers projected into navigable airspace regardless of whether or not the beam is visible.
Visual interference distances: Protection distances considered in addition to NOHD for planned use of visible lasers. The distance included for each calculation begins at the laser source and ends at the defined distance. The distance term and primary hazards for each are as follows.
• Sensitive Zone Exposure Distance (SZED): Flashblindness and afterimage.
• Critical Zone Exposure Distance (CZED): Glare.
• Laser-free Exposure Distance (LFED): Not expected to cause a distraction beyond this distance.
NOTE: Visual distraction may also occur within the SZED and CZED.
A.16.1. Protection Distance Considerations
• Visible/non-visible determination: Determine whether one or more of the laser wavelengths are visible (within 400 nm to 700 nm).
o If the laser has no wavelengths within the visible range:
▪ Enter “N/A (non-visible laser)” in all nine SZED, CZED, and LFED cells (14b through 14d).
▪ Calculate only the three NOHD distances for section 14a.
o If the laser has one or more visible wavelengths, proceed to calculate all twelve exposure distances (cells 14a through 14d).
• Exposure distances less than the NOHD: For some visible lasers, the SZED, CZED, and LFED calculations may result in a value less than (a shorter distance) the NOHD. If this is the case, for safety reasons:
o Do not enter the distance value in the applicable cell and, instead, enter “Less than NOHD.”
o Rationale: The NOHD (distance potentially damaging to the eye) is the most important for calculating safety distances and the protection of commensurate airspace.
Appendix A A-16 A.16.2. Slant Range Calculations For lasers with a small beam diameter at the output aperture (less than one centimeter),5 use the equations 70-1.1 through 70-1.3 as examples of a simplified method and enter the data in the first column of section 14. Perform the calculation and round up to the next whole number.
A.16.3. Slant Range (NOHD) To determine the NOHD slant range (SR) in feet:
• Use Equation 70-1.1 for a single pulse or repetitively pulsed laser with a frequency less than 13 kHz (less than 6.5 kHz for 1050 nm to 1400 nm).
• Use Equation 70-1.2 for a continuous wave or repetitively pulsed lasers with a frequency greater than 13 kHz (greater than 6.5 kHz for 1050 nm to 1400 nm).
• Complete the calculation and enter the result in cell 14a (slant range column).
Equation 70-1.1: Calculating NOHD slant range with pulse energy and MPE in J/cm2 𝑁𝑂𝐻𝐷𝑆𝑅 = 32.8𝑚𝑟𝑎𝑑 × √1.2732 × 𝐽𝑀𝑃𝐸
Equation Term Explanation NOHDSR NOHD slant range (feet)
32.8 Conversion factor used to convert centimeters into feet and radians into milliradians (0.0328 feet per centimeter) mrad Beam divergence (milliradians)
1.2732 4/π (derived from the original ANSI equation) J Pulse energy (joules or J) MPE MPE per pulse (joules per square centimeter or J/cm2)
5 For lasers with beam diameters larger than one centimeter at the output aperture, use the appropriate NOHD calculations in ANSI Z136.6, Appendix B. and submit calculations to FAA as a separate attachment.
Appendix A A-17 Equation 70-1.2: Calculating NOHD slant range with average power and MPE in mW/cm2 𝑁𝑂𝐻𝐷𝑆𝑅 = 32.8𝑚𝑟𝑎𝑑 × √1273.2 × 𝑊𝑀𝑃𝐸
Equation Term Explanation NOHDSR NOHD slant range (feet)
32.8 Conversion factor used to convert centimeters into feet and radians into milliradians (0.0328 feet per centimeter) mrad Beam divergence (milliradians) 1,273.2 4/π (derived from the original ANSI equation) then divided by 0.001 to express the value in milliwatts for this equation (original equation uses watts) W Average power (watts) MPE MPE (milliwatts per square centimeter or mW/cm2)
NOHD calculation example What is the NOHDSR for a 40-watt CW visible laser with a beam divergence of 1.5 milliradians?
Given:
mrad: 1.5 milliradians W: 40 watts MPE: 2.6 mW/cm2 (from Table 2) Solution:
𝑁𝑂𝐻𝐷𝑆𝑅 = 32.81.5 × √1273.2 × 402.6 = 21.87 × √19588 = 21.87 × 140 = 𝟑, 𝟎𝟔𝟐 𝐟𝐭 A.16.4. Slant Range (SZED, CZED, and LFED) SZED slant range: To calculate the SZED slant range (SZEDSR) distance, use Equation 70-1.3.
Complete the calculation and enter the value in cell 14b (slant range column).