ISO/R 1548:1971

Ref. No. : ISO/R 1548-1971 (E)
UDC 620.7.064.5 : 621.316.923.1
IS0
I N T E RN AT I O N A L O R G A N I2 AT I O N FOR STAND AR D I ZATl O N
.
IS0 RECOMMENDATION
L
R 1548
PRECISION FUSE-LINKS FOR AIRCRAFT
(TYPE A)
1st EDITION
May 197 1
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.

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BRIEF HISTORY
The IS0 Recommendation R 1548, Precision fuse-links for aircraft (Type A), was drawn up by Technical
Committee ISO/TC 20, Aircraft and space vehicles, the Secretariat of which is held by the British Standards
Institution (BSI).
Work on this question led to the adoption of Draft IS0 Recommendation No. 1548, which was circulated
L
to all the IS0 Member Bodies for enquiry in June 1968. It was approved, subject to a few modifications of an
editorial nature, by the following Member Bodies :
Italy Thailand
Australia
New Zealand Turkey
Belgium
Canada Peru U.A.R.
Czechoslovakia South Africa, Rep. of United Kingdom
Greece Spain
Israel Switzerland
The following Member Bodies opposed the approval of the Draft :
Germany
Netherlands
U.S.S.R.
This Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided
to accept it as an IS0 RECOMMENDATION.

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-5- ISO/R 1548-1971 (E)
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IS0 Recommendation R 1548 May 1971
PRECISION FUSE-LINKS FOR AIRCRAFT
(TYPE A)
1. SCOPE
This IS0 Recommendation gives the dimensions and performance requirements for a range of precision fuse-
links suitable for use in aircraft electrical systems having voltage and frequency characteristics conforming to
IS0 Recommendation R 222*, Voltages for aircraft electrical systems, at any ambient temperature from
- 65 OC to + 85 OC, and all altitudes from O to 24 400 m.
2. TERMINOLOGY
The terminology used in this IS0 Recommendation is in conformity with the International Electrotechnical
Commission (IEC) Publication 269, Low voltage fuses with high breaking capacity for industrial and similar
purposes - Part 1 : General requirements, as far as practicable.
3. GENERAL REQUIREMENTS
The fuse-links should comply with the requirements of IS0 Recommendation R 1547, Precision fuse-links
for aircraft - General requirements.
4. DIMENSIONS
The dimensions of the fuse-links should comply with Table 1 for the ferrule type or Table 2 for the tag
type.
5. CURRENT, VOLTAGE AND BREAKINWAPACITY RATINGS
The current ratings, the voltage ratings and breaking-capacity ratings of the fuse-links should be in accordance
with those listed in Table 3.
6. TIME/CURRJZNT CHARACTERISTICS
The pre-arcing time/current characteristics of the fuse-links should be within the appropriate envelope curves
shown in the Annex.
7. TESTS
The fuse-links should be tested in accordance with IS0 Recommendation R 1547.
*
See also IS0 Recommendation R 1540, Characteristics of aircraft elecfrical systems. (In course of preparation.)

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TABLE 1 - Dimensions of ferrule-type fuse-links
Points of measurement of voltage drop
I \

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-7- ISO/R 1548-1971 (E
TABLE 2 - Dimensions of tag-type fuse-links
c
I Bodv I B I C ID1 E I F I
max. min. max. min. nom. max. min. max. min.
34.0 32.8 7.3 7.0 0.8 53.1 50.0 3.9 3.7
mrn
O
in 1.349 1.294 0.289 0.275 0.032 2.097 1.974 0.152 0.147
rnm
34.3 33.0 12.7 12.1 0.8 56.6 54.9 5.2 4.9
1
'v
in
1.354 1.300 0.500 0.475 0.032 2.234 2.160 0.204 0.194
~
mrn 37.8 36.8 18.3 17.9 1.2 71.4 69.9 6.9 6.5
2
in 1.490 1.450 0.720 0.704 0.048 2.818 2.754 0.270 0.256
mrn148.0 147.0 135.1 134.5 I 1.6 189.4 187.9 18.9 I 8.1
in I 1.890 I 1.850 I 1.382 I 1.360 I 0.063 I 3.522 1 3.462 I 0.334 I 0.318
G H J K L
Body
size
max. min. nom. rnax. min. max. min. rnax.
I I I I I I I I I
mm 6.5 6.2 43.4 6.5 6.2 0.81 0.71 0.64
O
in
0.255 0.245 1.71 0.255 0.245 0.032 0.028 0.25
mrn 10.3 9.5 44.5 12.0
11.8 1.40 0.51 7.9
1
in 0.406 0.375 1.75 0.474 0.463 0.055 0.020 0.312
mm 16.0 15.2 55.4 16.8 16.7 1.40 0.51 9.5
2
in
0.630 0.600 2.187 0.663 0.656 0.055 0.020 0.375
I
rnm 26.2 25.4
69.9 33.3 33.0 1.40 0.51 12.7
3-
in 1.030 1.000 2.75 1.319 1.306 0.055 0.020 0.5

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