Fe deral Aviation Agen 

SUBJECT : GLASS FIBER FABRIC FOR AIRCRAFT 

cY ACNO: 2044 

AIRCRAFT 

EFFECTIVE : 

9/3/M 

COVERING 

1. 

2. 

3. 

4. 

PURPOSE. This circular provides a means, but not the sole means for 

acceptance of glass fiber fabric for external covering of aircraft 

structure. 

REFERENCE REGULATIONS. FAR’s, Sections 23.603, 25.603, 27.603, 

and 29.603. 

BACKGROUND. There has been an increase in the use of glass fiber 

fabrics for covering aircraft structure over the past years. While 

existing Technical Standard Orders provide a basis for the acceptance 

of cotton fabrics for aircraft cwering, they do not provide a means 

for acceptance of glass fiber fabric. Past installations using glass 

fiber fabric have received engineering approval by means of Supplemental 

Type Certificates. 

ACCEPTABLE MEANS OF COMPLIANCE. 

(a) General. The referenced regulations require that the 

materials used in the structure must show suitability 

and durability, to be established by tests or experience, 

and meet approved specifications so as to ensure strength 

and other properties conforming to the design data. 

Fabrics are acceptable in showing compliance with the 

referenced regulations if they comply with Military 

Specifications HIL-C-9084, ML-Y-114OC, and MIL-G-1140 

in the untreated condition, have the following properties, and are tested in accordance with the methods 

listed: 
Page 2 AC m-44 

9/3/65 

Property 

(1) Weight, oz. per sq. yd., max. 

(2) Thread count, ends per in. min. 

warp and fill, respectively. 

(3) Breaking strength, either direction 

lb. per in,, min. 

(4) Elongation, when under 70 lb. 

(5) 

(6) 

(b) 

(4 

(4 

tension, per cent, 162x 

Nominal Width 38 in. 13 

44 in. 13 

50 in. 13.5 

60 in. 14 

69 in. 15 

90 in. 16 

Burst strength, mullen, points, min. 

Sizing, Finishing, and other nonfibrous materials, percent max. 

170 

4.5 

Value 

4.5 

36 x 34 

80 

Test Method 

ASTM D39-61 

ASTM 039-61 

ASTM D39-49 or D579-49 

(Raveled atrip method) 

ASTM D39-49 

(Raveled strip method) 

(Note (4) 

(Note 09) 

D579-49 Section 12 

(Note (c)l 

Yarns. Comrocrcially designated Type E continuous filament glass 

fiber yarns, as listed in Table II of Military Specification 

m-Y-114OC, are acceptable. 

Weave. The weave should be plain (one up and one down). 

Processing of Finishin&. It is acceptable if the processed or finished f6bric is shown ,b test or service experience to be compatible with standard aircraft grade6 of nitrate or acetate butyrate 

dope conforming to the military specifications lfbted in Note (d) 

or an equivalent specification. The finished fabric should be 

compatible with epoxy, polyurethane and polyester type resins conforming to tho6e specifications libted in Note (d). Compatibility 

may be demonstrated by appropriate examination of the fabric area 

after vetting by the impregnating agent. 

Par 4 
AC 20-44 

9/3/u 

Page 3 

NOTES: (a) Elongation at 70 pounds should be mensured from a base lfne 

on a chart to a point at which the curve intersects 70 pounds 

load ordinate with the base line passing through the point 

vhere the cume leaves the zero ordinate. 

(b) Bursting strength should be determined with a hydraulic type 

machine in vhich the fabric is firmly clamped against a rubber 

diaphragm, through vhich the pressure is applied to a circular 

area of approximately 1 square inch. The pressure required to 

burst the cloth should be registered on an accurate Bourdon 

tube-type gage, calibrated fn pound6 per square inch, the readings of which are designated as points. See Federal Specification CCC-T-19lb, Hathod 5122 for details of test. 

(c) A desizing operation may be performed, if necessary, to reduce 

the sizing content to the max. specified. 

(d) The following military specificatfons, or later revisions thereof, 

apply to aircraft dope and epoxy and polyester resins: 

NIL-D-5549A-1 Clear Dope, cellulose - Acetate 

Butyrate. 

MIL-D-7850 Fungicidal Dope, First Coat, 

. Cellulose-Acetate, Butyrate. 

MIL-D-555011-1 Pigmented Dope, Cellulose-Acetate, 

Butyrate. 

HIL-D-555lA-2 Pigmented Dope, Gloss, Cellulose 

Acetate, Butyrate. 

XXL-D-5553A-2 Clear Dope, Cellulose Nitrate 

KLL-D-55524-1 Clear Dope, Gloss Cellulose Nitrate 

NIL-D-5554A-1 Glass Dope, Cellulose Nitrate 

MIL-D-5555-1 

MIL-R-9300A 

Pigmented Dope, Cellulose Nitrate 

Resin, Epoxy, low pressure 

laminating. 
Page 4 AC 20-44 

9/3/65 

MIL-R-25042A Resin, Polyester, low pressure 

laminating. 

MIL-R-7575B Resin, Polyester, low pressure 

laminating. 

orge S. Moore