FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 5. Nondestructive Inspection (NDI) | 7. Ultrasonic Inspection | 5-95. Bond Testing Instruments
9/8/98
AC 43.13-1B
TABLE 5-8. Ultrasonic inspection methods for bonded structures.
Advantages
Disadvantages
THROUGH-
TRANSMISSION
Applicable to
structures with ei-
ther thick or thin
facing sheets.
Applicable to
structures with
multiple layers
bonded over hon-
eycomb core.
Detects unbonds
on either side
Detects broken,
crushed, and cor-
roded core.
In some cases
water in core can
be detected.
Access to both
sides of part is re-
quired.
Does not deter-
mine layer position
of unbonds.
Alignment of
search units is
critical.
Couplant is re-
quired.
INSPECTION METHOD
PULSE-ECHO
RINGING
Applicable to struc-
tures with either thick
or thin facing sheets.
Determines which
side is unbonded.
Detects small un-
bonds.
Detects broken,
crushed, and cor-
roded core.
In some cases water
in core can be de-
tected.
Applicable to com-
plex shapes.
Detects small near
surface unbonds
(larger than di-
ameter of search
unit).
Inspection from both
sides required, does
not detect far side
unbonds.
Applicable only to
skin-to-honeycomb
core structures.
Reduced effective-
ness on structures
with multiple skins
over honeycomb
core.
Applicable only to
near surface un-
bonds, works best
on unbonds be-
tween top sheet
and adhesive, may
miss other un-
bonds.
Reduced effective-
ness on thick skins.
Couplant required.
DAMPING
Applicable to
structures with ei-
ther thick or thin
facing sheets.
Applicable to mul-
tiple-layered (more
than two layers)
structures.
Detects unbonds
on either side.
Detects small un-
bonds (larger than
diameter of re-
ceiving search
unit).
Applicable only to
doublers and lami-
nate-type struc-
tures.
Access to both
sides required.
Does not deter-
mine layer posi-
tions of unbonds.
Couplant required.
Inspection rate is
slow.
Couplant required.
Par 5-95
Page 5-49