Federal Aviation Administration

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Federal Aviation Administration

1 Memorandum

2 Date:

November ##, 2022

3 To:

All Airports Regional Division Managers

4 From:

5

Michael A.P. Meyers, P.E. Manager, Airport Engineering Division, AAS-100

10/13/2022

6 Prepared by: Marvin Woods, P.E., AAS-110

7 Subject:

8

Engineering Brief No. 104, Supplemental Guidance to Advisory Circular 150/5345-44K (Specification for Runway and Taxiway Signs)

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10 This Engineering Brief (EB) addresses omissions and ambiguities to Advisory Circular (AC) 11 150/5345-44K, Specification for Runway and Taxiway Signs. This EB will assist FAA safety 12 personnel, airport owner operators and their support staff, and signage providers with interim 13 guidance in interpreting and applying the above referenced AC while it undergoes the revision 14 process.

15 Attachment

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FAA

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Airports

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ENGINEERING BRIEF 104

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Supplemental Guidance for Advisory Circular (AC) 150/5345-44K, Specification for Runway and Taxiway Signs

Purpose. This Engineering Brief (EB) provides supplemental guidance and clarifications to address ambiguities found in AC 150/5345-44K, Specification for Runway and Taxiway Signs. The principles and practices contained in this EB will ultimately be incorporated into the revised AC.

Applicability. Except as otherwise required under 14 CFR Part 139, this guidance is not legally binding in its own right and will not be relied upon by the FAA as a separate basis for affirmative enforcement action or other administrative penalty. Conformity with this guidance, as distinct from existing statutes, regulations, and grant assurances, is voluntary only, and nonconformity will not affect rights and obligations under existing statutes and regulations.

Application and Use. This Engineering Brief will assist FAA safety personnel, airport owners, operators and their support staff, and signage providers with interim guidance in interpreting and applying the above referenced AC requirements.

Background. One of the goals of Advisory Circulars is to establish a uniform set of standards throughout the National Airspace System (NAS). However, airfield signage infrastructure (i.e., sign housing and enclosures) may develop into non-standard configurations at individual airports over time. This legacy system has made implementing uniform standards challenging in a variety of situations. This Engineering Brief will address some of those challenges as we strive toward goals of uniformity and consistency.

Questions. Contact Marvin Woods at 202-267-9529 or by email at Marvin.Woods@ for any questions about this Engineering Brief.

Effective Date. This Engineering Brief becomes effective as of the date the associated memorandum is signed by the Manager, FAA Airport Engineering Division, AAS-100.

EB No. 104

FAA Airport Engineering Division

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54

Guiding Principles in Airfield Signage

55 The goals of airfield signage should be (in the following order) to:

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1. Convey and maintain safety.

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2. Be clearly visible.

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3. Provide accurate instruction and description of its physical location.

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4. Provide clarity in its meaning and subsequent comprehension.

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5. Be concise in its message.

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6. Be consistent in its appearance in promoting uniformity.

62 We encourage everyone involved in the design, construction, installation, inspection and 63 maintenance of airfield signage to use the principles above as a checklist in their tasks or duties.

64 Furthermore note, unlike mechanical, or electronic devices, the function of signage is abstract. It 65 is a two-dimensional message in a three-dimensional active environment. It pertains to human 66 visual perception. Two key aspects of visual perception are:

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1. Symmetry.

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2. Proportionality (or scale).

69 Always apply the proper use of these aspects in coordination with the requirements of AC 70 150/5345-44K.

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71

Issues Identified with Sign Face Layouts

72 Manufacturing Tolerances. 73 Tolerances refer to a range in both directions, not just a minimum or maximum. For example, a 74 border width of 1 inch (25 mm) with a tolerance of ?1/8 inch (3 mm) is interpreted as having a 75 minimum width of 7/8 inch (22 mm) and a maximum width of 1.125 inch (32 mm).

76 Paragraph 3.2.5.2b of AC 150/5345-44K has been corrected to remove potential conflicts with 77 Table 10 of the AC (included for reference). For guidance, see the related Errata Sheet.

78 Note: Refer to Figure 5 of AC 150/5345-44K (included for reference) and associated "Notes" for 79 applicable exceptions.

80 Figure 1 shows an example of the specified separation distance between message elements.

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Figure 1 ? Horizontal Spacing/Separation Distance between Message Elements

Size 2 sign ? 2"-14" range Size 3 sign ? 2.5"-16" range

X

CD

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83 Paragraph 3.2.5.2.b (3) of AC 150/5345-44K states:

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"If the sign panel viewable horizontal length exceeds the maximum spacing allowable for

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the message elements, then the overage on the panel must be blanked out (black) at the

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outboard end of the legend in relation to its mounting (left or right side) adjacent to the

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Taxiway/Runway."

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(See Improving the Conspicuity of Signs with Blanks below)

89 The term "outboard" is defined relative to the sign's location from the Taxiway/Runway to 90 which its message applies, not the sign housing that contains it. However, the AC does not define 91 a maximum spacing. This does not mean the spacing is unlimited as this may introduce 92 confusion and/or hesitancy to pilots and airfield ground personnel.

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93 Therefore, the range for horizontal spacing/separation distance between message elements in a 94 sign array as described in paragraph 3.2.5.2.b (3) of AC 150/5345-44K is also applicable for the 95 last message element to the edge of the sign housing. (See Figure 2.)

96 Figure 2 - Horizontal Spacing/Separation Distance between Message Elements to the Edge

97 of Sign and Outboard End of the Legend in Relation to its Mounting (in Detail A, Taxiway

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Charlie is left of the sign; in Detail B, Taxiway Delta is left of the sign)

Size 2 sign ? 2"-14" range Size 3 sign ? 2.5"-16" range

X

X

Z

Z

CD DB

Detail A

Detail B

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100 Example: The tolerances for "X" or "Z" for a given size sign in Figure 2 above are equal. 101 Therefore, the tolerance between two message elements (Figure 2, Detail A) and the tolerance 102 between the last message element and the end of the sign (Figure 2, Detail B) are equal. Any 103 "overages" (distance from the end of the right side "Z" tolerance to the outboard end of the sign) 104 as shown in Figure 2, Detail B, follows the guidance in paragraph 3.2.5.2.b(3) of AC 150/5345105 44K.

106 Additional considerations: 107 The dimensions of a lighted sign are specified in Table 3-1 of AC 150/5345-44K. Sign housing 108 lengths must be chosen to show only complete message element(s) and be the shortest possible 109 overall length. The shortest possible overall length of the sign housing is established by factoring 110 in the minimum dimensions from Table 10 and Figure 5 of AC 150/5345-44K (Table 10 and 111 Figure 5 included for reference) in the spacing calculations for all message elements.

112 If a two-sided sign is required, the side with the longest legend will determine the length of sign 113 used.

114 It is also important to note that the message element separation/spacing differs from character-to115 character. For example, in Figure 2, Detail A, the black Taxiway C Location Sign that includes a 116 yellow border is one message element. The Taxiway D Direction sign includes two arrows and a 117 "D" character and is considered one message element. An example of character-to character 118 spacing would be the distance between the "D" character to the inner portion (leg) of the arrow 119 (applicable on both sides).

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120 As stated earlier, the infrastructure (i.e., sign housing and enclosures) which the signs rest, is a 121 non-standard compilation of what individual airports developed over time. For this reason, some 122 measure of flexibility must be applied under certain field constraints, as we move toward 123 conformity and uniformity in the NAS.

124 To accommodate unique or older signs with nonstandard sign widths, additional horizontal 125 spacing/separation distance is allowed from the last message element to the outboard end of the 126 legend (see Figure 3). This spacing/separation distance (Y), is an addition to the spacing and 127 separation distance (Z) and must not exceed 12 inches (305 mm) for a Size 1, 14 inches (356 128 mm) for a Size 2, and 16 inches (406 mm) for a Size 3 sign (Y). In Figure 3, the letter "M" is 129 used for reference because it is horizontally symmetric and its outer edges are easily defined.

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Figure 3 ? Optional Additional Horizontal Spacing/Separation Distance from the Last

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Message Element to the Outboard End of the Legend in Relation to its Mounting

Size 2 sign ? 2"-14" range Size 3 sign ? 2.5"-16" range

Z

Z

DB

Y

M

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133 Improving the Conspicuity of Signs with Blanks 134 It has been reported that adding blanks may impair or obscure the ability of airfield ground 135 personnel to perceive the end of the sign. This could inadvertently create impact hazards. Blank 136 sides of airfield signs may bleed light making them deceptively visible on a clear night. Airport 137 vehicles hitting signs during low visibility conditions, such as blowing snow, may be an issue. 138 This could inadvertently create trip or ground vehicle impact hazards. To mitigate this the 139 airport owner/operator may consider:

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? Reflective tape and/or markers (away from the line of site of aircraft) per AC 150/5345-

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39, Specification for L-853, Runway and Taxiway Retroreflective Markers.

142 Paragraph 3.2.5.4.a (Lighted Sign Faces) of AC 150/5345-44K reads...

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"a. Signs must be either single face with a message on one side or double face with a

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message on two sides."

145 However, as the sign housing and both messages may not have necessarily been designed and 146 installed concurrently. Considerations for each sign change:

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? If both signs are being modified as part of an active or planned project, and the shorter

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message array of the two sides will not conform to the AC, consider a modification of

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standards (MOS) per FAA Order 5300.1, Modifications to Agency Airport Design,

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Construction, and Equipment Standards. The owner operator may wish to consider an

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MOS.

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? If changes in site conditions require a message array to be modified, and both or either

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side will not conform to the AC, a modification of standards (MOS) should be

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considered.

155 Summary 156 The guidance offered in this Engineering Brief is supplemental and interim. However, the 157 guiding principles previously described will always be applicable and should always be 158 enforced.

EB No. 104

FAA Airport Engineering Division

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159 For reference only:

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160 EB No. 104

FAA Airport Engineering Division

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