Section 2. Evaluating Aeronautical Effect

29-2-1. AERONAUTICAL REVIEW

a. At a minimum the following items must be studied as part of any aeronautical review:

1. Location of the proposed laser operation.

2. Aircraft operations affected by the proposed operation.

3. Air traffic flows in the proposed area of the operation.

4. An analysis of adverse effect conducted by the ATC facility having control over the affected airspace.

5. A safety analysis conducted by the Flight Standards Division regarding the effects on flight crews.

6. For visible laser systems, plot the LFZ, CFZ, and SFZ (if applicable) for all potentially affected airports and evaluate any control measures, which may mitigate any adverse effect.

7. The effective irradiance levels listed below must not be exceeded in the corresponding zones.

(a) A laser-free zone is limited to 50nW/cm² or less.

(b) A critical flight zone is limited to 5mW/cm² or less.

(c) A sensitive flight zone is limited to 100mW/cm² or less.

(d) A normal flight zone, as well as the above zones, is limited to the MPE or less.

EXCEPTION-
The LFZ, CFZ, and SFZ need only be considered for visible laser systems. Further, when control measures (e.g., safety observers) mitigate all hazards or other issues raised by the aeronautical review, irradiance levels may exceed the above levels.

b. Consult FDA/CDRH personnel for technical advice. (e.g., regarding repetitively pulsed laser calculations)

c. Scientific/research lasers in accordance with 21 CFR Section 1010.5 may be exempt from Title 49 and, in addition, may not be able to comply with the above procedures. Regardless of whether or not a proponent is exempt from the provisions, a proposal is still reviewed using the above procedures.

29-2-2. LOCAL LASER WORKING GROUP (LLWG)

When necessary, the service area office may convene a LLWG to assist in evaluating proposed laser operation.

a. The service area office must forward information on a proposed outdoor laser operation to the local air traffic facility.

b. The local air traffic facility must act as the focal point for the LLWG. Other participants may include, but not limited to, representatives from the ARTCC, ATCTs, airport management, airspace users, city/county/state officials, other government agencies, military representatives, qualified subject experts, laser manufacturers, etc.

c. The LLWG must resolve issues regarding local laser operations and forward recommendations to the service area office as soon as practicable.

29-2-3. PROTECTION DISTANCE CALCULATIONS

a. The laser system power range table (TBL 29-2-1) provides the applicable protection distances along the axis of the laser beam with a 1mrad divergence. This table must not be used to determine the protection distances for repetitively pulsed (RP) lasers. Proponents are required to resolve RP laser system calculations with the FDA or laser manufacture before submitting a completed Laser Configuration Worksheet to the FAA.

b. TBL 29-2-2 lists sine and cosine values to be used in determining the vertical and horizontal distances to be protected from the laser source. The distances obtained from TBL 29-2-1 are multiplied by these values to determine the appropriate vertical and horizontal distances to be protected based on the minimum and maximum vertical angles. Differences in site/ground elevations should be considered.

c. The vertical component of the protection distance may be determined by multiplying the laser distance from TBL 29-2-1 by the sine of the maximum elevation angle of the laser beam from TBL 29-2-2. For example, vertical component = protection distance x sine of the maximum elevation angle.

d. The horizontal component of the protection distance may be determined by multiplying the laser distance from TBL 29-2-1 by the cosine of the minimum elevation angle of the laser beam from TBL 29-2-2. For example, horizontal component = protection distance x cosine of the minimum elevation angle.

e. Do not reduce calculated distances for correction factor techniques unless validated by FDA/CDRH.

f. All distances must be rounded up to the next 100-foot increment. See example problems 1, 2, and 3 that follow the Vertical and Horizontal Component Table, TBL 29-2-2.

29-2-4. CONTROL MEASURES

Physical, procedural, and automated control measures may be used to ensure that aircraft will not be exposed to levels of illumination greater than the respective maximum irradiance levels established for the various protected zones.

a. Physical beam stops at the system location or at a distance may be used to prevent laser light from being directed into protected zones.

b. The beam divergence, azimuth, elevation, and output power may be adjusted to meet appropriate irradiance levels.

c. Beam direction should be specified by giving bearing in the azimuth scale 0 - 360 degrees and elevation in degrees ranging from 0 - 90 degrees, where zero degrees is horizontal and +90 degrees is vertical. Bearings must be given in both true and magnetic north.

d. Manual operation of a shutter or beam termination system can be used in conjunction with safety observers. Observers must have an adequate view of the airspace surrounding the beam's paths to a distance appropriate to the affected airspace.

e. Scanning of a laser system that is designed to automatically shift the direction of the laser beam can be used. However, scanning safeguards must be found to be acceptable by the FDA and the FAA. The FDA recommendation must be included in the proposal to the FAA.

NOTE-
Scanning may reduce the level of illumination; however, it may also increase the potential frequency of an illumination.

f. Any automated system designed to detect aircraft and automatically terminate the beam, redirect the beam, or shutter the system, must be reviewed and found to be acceptable by the FAA before the use of the device may be accepted as a control measure.

TBL 29-2-1
LASER SYSTEM POWER RANGE TABLE
CW Laser Beam Divergence: 1 Milliradian
* NOT TO BE USED WITH RP SYSTEMS

* The FDA may be contacted to validate data for repetitively pulsed lasers.

NOTE-
[1] To determine the NOHD for lasers having divergence values other than 1.0 mrad use the formula - NOHD @ 1.0 mrad ÷ mrad (actual divergence) = NOHD.

EXAMPLE-
Power 40W, Divergence 7 mrad
NOHD 40W @ 1.0 mrad = 4,591
4,591 ÷ 7 = 656 NOHD. Rounded up to nearest hundred feet = 700 feet.
(A beam divergence of .7 would make this calculation 7,000 feet)

* The proponent validates repetitive pulsed information with the FDA and submits a completed laser configuration worksheet.

TBL 29-2-2
VERTICAL AND HORIZONTAL COMPONENTS

VERTICAL COMPONENT

Maximum Elevation Angle	Sine (vertical component multiplier)
90	1.0000
85	.9962
80	.9848
75	.9659
70	.9397
65	.9063
60	.8660
55	.8192
50	.7660
45	.7071
40	.6428
35	.5736
30	.5000
25	.4226
20	.3420
15	.2588
10	.1737
5	.0872
0	.0000

HORIZONTAL COMPONENT

Minimum Elevation Angle	Cosine (horizontal component multiplier)
0	1.0000
5	.9962
10	.9848
15	.9659
20	.9397
25	.9063
30	.8660
35	.8192
40	.7660
45	.7071
50	.6428
55	.5736
60	.5000
65	.4226
70	.3420
75	.2588
80	.1737
85	.0872
90	.0000

LASER PROBLEM SOLUTIONS

EXAMPLE PROBLEM 1:
Laser output power = 15 watts
Laser beam divergence = 1.0 mrad
Find: Laser protection distances:
1. Find TBL 29-2-1 at 15 watts in the Laser Output Power column.
2. Proceed horizontally and read: NOHD of
2,811 feet, CFZ of 64,108 feet, SFZ 14,335 feet.
Answer: (with rounded up distances): NOHD
2,900 feet, CFZ 64,200 feet, SFZ 14,400 feet.

EXAMPLE PROBLEM 2
Laser output = 18 watts
Laser beam divergence = 1.0 mrad
Maximum elevation angle 60°
Minimum elevation angle 20°
Find:Vertical and horizontal distances to be protected:
1. Laser distance (from TBL 29-2-1) = 3,080 feet.
2. Sine of 60° maximum elevation angle (from
TBL 29-2-2) = 0.8660.
3. Find altitude by multiplying 3,080 feet
by 0.8660 = 2,667 feet.
4. Cosine of 20° minimum elevation angle (from TBL 29-2-2) = 0.9397
5. Find horizontal distance by multiplying 3,080 feet by 0.9397 = 2,894 feet.
Answer: Minimum required protected airspace
is 2,700 feet vertically and 2,900 feet horizontally from the laser source.

EXAMPLE PROBLEM 3
Power = 25 watts
Laser NOHD at 1 mrad = 3,629 feet.
Beam Divergence = .7 mrad
Find: Actual NOHD
1. Find actual NOHD by dividing the NOHD at 1 mrad divergence (3,629 feet) by actual divergence
(.7 mrad).
2. 3629 feet. ÷ .7 = 5184 feet.
Answer: NOHD 5,200 feet (rounded up)