SAE ARP 4822A-2017 Night Vision Imaging System (NVIS) Compatible Illuminated Pushbutton Switches and Indicators.pdf

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4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/ARP4822A AEROSPACE RECOMMENDED PRACTICE ARP4822 REV. A Issued 2006-06 Revised 2017-08 Supersedi

5、ng ARP4822 Night Vision Imaging System (NVIS) Compatible Illuminated Pushbutton Switches and Indicators RATIONALE Warning, caution and advisory push-button switches and indicators are considered by pilots to be one of the most important items in the aircraft crew station. With well defined and histo

6、rical application of aviation color requirements, these push-button switches and indicators can be particularly difficult to achieve in an NVG green-lighted compatible crew station with chromaticity limits now defined by military specifications that are lacking in most FAR documents. This specific t

7、echnology, which is utilized to deal with the design of these devices is covered in this document. The most recent revision to is update the references, add Class C response curve and to correct some photometric and radiometric requirements. 1. SCOPE This SAE Aerospace Recommended Practice (ARP) rev

8、iews the basics of NVIS compatibility and discusses the specific illuminated pushbutton switch and indicator requirements for sunlight readability, color, luminance, and NVIS radiance when used in NVIS compatible cockpits. The recommendations and special considerations set forth in this document are

9、 made to give the design engineer a better understanding of MIL-L-85762A and MIL-STD-3009 NVIS compatibility requirements and to provide information on the visual characteristics of NVIS compatible pushbutton switch and indicators. The recommendations are primarly for military aircraft since civilia

10、n aircraft FAR requirements typically do not cover NVIS applications with the exception of those covered by RTCA/DO-275. 1.1 Purpose The purpose of this document is to recommend the design requirements and considerations which the design engineer should observe when selecting and using NVIS compatib

11、le illuminated pushbutton switches and indicators. NVIS compatible lighting is defined as any lighting whose spectral radiance has been selectively filtered to meet the NVIS radiance and chromaticity requirements of MIL-L-85762A or MIL-STD-3009 when dimmed to the specified luminance value. With the

12、introduction of LEDs as a lighting technology, the use of filtering for NVIS compatibillity is lessened or not required. In addition, LEDs now allow NVIS radiance limits to be achieved with more saturated chromaticity coordinates thereby allowing color selections that are closer to or within the ori

13、ginal Aviation colors requirements. For example, using LEDs would allow warning lights that can meet the Aviation Red requirements but not the NVIS Red requirements since the chromaticity coordinates are now outside the 1976 CIE circle limits but still meet the NVIS requirements. Since the original

14、NVIS requirements were based on filtered incandscent lamps, they had to allow changes in the Chromaticity limits to achieve pushbutton switches that would not impact the visual acuity of the Night Vision Goggle (NVG). SAE INTERNATIONAL ARP4822A Page 2 of 15 2. REFERENCES 2.1 Applicable Documents The

15、 following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document

16、 and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 U.S. Military Specifications and Standards Copies of these documents are available at http:/qui

17、cksearch.dla.mil. MIL-L-85762A Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible MIL-PRF-22885J Switches, Push Button, Illuminated, General Specification for MIL-S-38039D Systems, Illuminated, Warning, Caution, and Advisory, General Specification for MIL-STD-3009 Lighting,

18、Aircraft, Night Vision Imaging System (NVIS) Compatible, 2 Feb, 2001 MIL-STD-411F Aircrew Station Alerting Systems, 10 Mar 1997 3. NVIS COMPATIBILITY BASICS 3.1 Night Vision Imaging System (NVIS) NVIS are devices that provide aircrew members with the ability to see at night by greatly amplifying out

19、side scenes illuminated by the night sky. 3.1.1 Image Intensifiers NVIS use third generation (GEN III) image intensifier tubes having a gallium-arsenide photocathode and microchannel plate to produce the amplification necessary to operate in starlight. 3.1.2 Mechanics of NVIS Operation The night sky

20、 irradiates objects with photons which are reflected as photon images. These photon images are focused by the objective lens onto the photocathode which emits electrons in direct proportion to the number of photons striking its surface. These electrons are greatly multiplied by the microchannel plat

21、e and are directed onto a phosphor screen where the amplified image is viewed through the ocular lens (see Figure 1). 3.2 Classification NVIS compatible lighting requirements are stated based on the type and class NVIS being used. 3.2.1 NVIS Types 3.2.1.1 Type I These are direct view image NVIS whic

22、h display the intensified image on a phosphor screen in the users direct line of sight. SAE INTERNATIONAL ARP4822A Page 3 of 15 Figure 1 3.2.1.2 Type II These are projected image NVIS which project the intensified image on a see-through medium in the users line of sight. An example of type II goggle

23、s are Cats Eyes (see Figure 2) Figure 2 - Cats eye goggles SAE INTERNATIONAL ARP4822A Page 4 of 15 3.2.2 NVIS Classes 3.2.2.1 Class A Any NVIS utilizing a 625 nm minus blue objective lens filter conforming to the specifications in Figure 3 are Class A. The relative spectral response of the Class A N

24、VIS is shown in Figure 3 and the tabulated values are listed in Table 6 of MIL-L-85762A or Figure C-4 from MIL-STD-3009. Figure 3 - (Class A) 625 NM minus blue filter specification SAE INTERNATIONAL ARP4822A Page 5 of 15 3.2.2.2 Class B Any NVIS utilizing a 665 nm minus blue objective lens filter co

25、nforming to the specifications in Figure 4 are Class B. The relative spectral response curve of the Class B NVIS is shown in Figure 5 and the tabulated values are listed in Table 7 of MIL-L-85762A or Figure C-5 from MIL-STD-3009. Figure 4 - (Class B) 665 NM minus blue filter specification SAE INTERN

26、ATIONAL ARP4822A Page 6 of 15 3.2.2.3 Class C This class of goggles utilizes a 665 nm minus blue objective lens filter similar to the Class B design, but incorporates a very narrow notch filter around the 545 nm that allows HUD symbology to be viewed on the NVG. The response curve of the Class C is

27、detailed in Figure 5 as taken from MIL-STD-3009, Figure C-6. Class C is unofficial, but careful consideration should be taken that any LED design status light does not peak near the leaky green wavelength 540-550 nm. Figure 5 - Class C filter response curve SAE INTERNATIONAL ARP4822A Page 7 of 15 3.

28、3 NVIS Compatible Lighting NVIS compatible is lighting which can be seen with the unaided eye without causing interference or degradation of the NVIS intensification capabilities. The NVGs will amplify any radiometric energy whether it comes from outside the aircraft or within. By greatly reducing t

29、he amount of radiometric energy in the wavelegths defined in Figures 3 thru 5, the NVGs will instead amplify the weak starlight radiometric energy thereby providing the pilot a sense of daytime images at night. 3.3.1 NVIS Radiance NVIS radiance is the amount of energy emitted by a light source that

30、is visible through NVIS and represents the amount of interference produced by the light source. It is the intregration of radiometric energy to the response curve of the NVGs. 3.3.2 Definition of NVIS Radiance NVIS radiance (NR) is the integral of the curve generated by multiplying the spectral radi

31、ance of a light source by the relative spectral response of the Class A or Class B NVIS. = ()()930450 (Eq. 1) where: NR = NVIS radiance (Class A, Class B or Class C) G() = relative NVIS response (Class A, Class B or Class C) N() = spectral radiance of lighting component (W/cm2*sr*nm) d = 5 nm increm

32、ents S = scaling factor LR/LM where: LR = required luminance level for NVIS radiance per MIL-L-85762A or MIL-STD-3009 LM = luminance measured 3.3.3 Definition of Compatible Lighting A lighting component produces compatible lighting if its NVIS radiance does not exceed a specified maximum when set to

33、 produce a specified luminance. For example, primary cockpit lighting (which is defined as NVIS Green) the maximum allowable NVIS radiance is 1.7 x 10-10 when the lighting is set to produce 0.1 fL. For warning, caution and advisory push-button switches and indicators, the NVIS radiance limits differ

34、 for each category of switches and indicators. Warning push buttons and indicators will have a higher radiance limit to draw the pilots attention due to the serious nature that the signal represents and advisory lighting requires the lowest level of radiance since the signal is of lower importance.

35、MIL-L-85762A and MIL-STD-3009 defines the various NVIS limits for warning, caution and advisory signals. If using LEDs, then the NVIS radiance limits called out in MIL-L-85762A and MIL-STD-3009 can also be achieved while still meeting the original chromaticity requirements of the Non-NVIS indicators

36、 SAE INTERNATIONAL ARP4822A Page 8 of 15 4. RECOMMENDATIONS Illuminated pushbutton switches and indicators are used in crew stations as visual signals to provide crew members with vital status information. Functionally, they serve as caution and advisory lights, master caution lights, and warning l

37、ights. When these crew stations are required to be compatible with NVIS, the pushbutton switch and indicators must meet the lighting requirements of MIL-L-85762A or MIL-STD-3009. These compatibility requirements must be strictly observed so as not to compromise the safety of crew members performing

38、tasks while using NVIS. 4.1 Sunlight Readability Illuminated pushbutton switches and indicators requiring readability in sunlight must meet the daylight legibility and readability requirements of MIL-L-85762A or MIL-STD-3009. Two separate requirements are defined depending on whether or not the indi

39、cator is to be readable in direct reflected specular sunlight. 4.1.1 Specular Sunlight Readability Requirements Illuminated switches and indicators requiring readability in direct reflected specular sunlight must have a lighted contrast CL not less than 0.6 and an unlighted contrast CUL with an abso

40、lute value less than or equal to 0.1 under 10000 fc of illumination as defined in MIL-L-85762A, MIL-STD-3009 (this document allows 0.4) and MIL-PRF-22885J when set at full rated voltages. The design goal should be a lighted contrast CL of not less than 0.6 with the improvements to NVIS filters now a

41、llowing that higher level of contrast value. 4.1.1.1 Test Arrangement The test arrangement must be as shown in Figure 6 where the 10000 fc source is set to an angle of 15 off the normal to the indicator and is the angle of incidence. The photometer is set at the angle of reflectance of 15. Other tes

42、t set ups have angles varing between 15 to 45, but the selected angle must be the same from the normal for the light source and photometer/spectroradiometer. Figure 6 SAE INTERNATIONAL ARP4822A Page 9 of 15 4.1.1.2 Contrast Requirements The contrast requirements for CL and CUL are: The On/Background

43、 Contrast CL = (B2- B1)B1 0.6 The Off/Background Contrast = (3 1)1 0.0 0.1 (Eq. 2) where: B1 = average background luminance B2 = average character luminance, lighted B3 = average character luminance, unlighted The average character and background luminance measurements should include three readings

44、per character in accordance with the sunlight readability test procedure defined in MIL-S-22885J. 4.1.2 Daylight Readability Excluding Specular Sunlight Illuminated pushbutton switches and indicators not requiring readability in direct reflected specular sunlight must have a contrast, CL, of not les

45、s than 1.0 in a 10 000 fc diffuse white light environment as defined in MIL-S-38039D. 4.1.2.1 Test Arrangement The test arrangement is not defined in MIL-S-38039D but a suggested test arrangement is shown in Figure 7. Figure 7 SAE INTERNATIONAL ARP4822A Page 10 of 15 4.1.2.2 Contrast Requirement The

46、 contrast requirements for CL is: 0.1BBBCC o n tr a s t112L (Eq. 3) where: B1 = average brightness of the unlighted portion B2 = average brightness of the lighted portion The average character and background luminance measurements should include three readings per character in accordance with the su

47、nlight readability test procedure defined in MIL-S-22885J. 4.1.3 Special Considerations 4.1.3.1 Specular Reflections The sunlight readability test requiring readability in direct reflected specular sunlight is the most severe test for sunlight readability. It represents the worst case situation wher

48、e the indicator is exposed to direct sunshine and positioned such that the pilot sees a specular reflection of the sun. In this case it is recommended that the indicator have hidden legends and a low reflective, diffuse front surface to avoid ghosting (appearing illuminated when unenergized) and to

49、eliminate surface specular reflections. 4.1.3.2 Contrast Values The specular sunlight contrast value of CL 0.4 has been reduced from 0.6 minimum to allow for the additional filtering necessary to achieve NVIS compatibility in MIL-STD-3009, paragraph C.5.9. A contrast of 0.4 is marginally acceptable and it is desirable for indicator to have higher contrast values for improved su