Ultrasonic Thickness Measurement of Aircraft Windows Updated March 2009
DeFelsko manufactures a hand-held, non-destructive ultrasonic
thickness gage that is ideal for measuring the thickness of aircraft windows
during the window restoration process.
Measurement Challenges
When evaluating the effects of wear and erosion on a substrate, the primary objective is to non-destructively measure
its remaining
thickness. Due to the safety considerations associated with aircraft
inspections, rapid sampling and data logging may be required.
Substrate Thickness Measurement Solutions
The ultrasonic PosiTector UTG Std is ideal for
non-destructive measurement of acrylic substrate thickness between 1 and 50 mm
(0.04 and 2.00"). Figure 1 is an application photo of a repair
technician using a PosiTector UTG Std to measure the remaining substrate thickness of
an aircraft window under repair. By measuring across the surface of the
window, it is possible to identify areas that have experienced significant
in-flight erosion
or wear from the window restoration process.
Figure 1 - Measurement of Aircraft Windows
The PosiTector UTG Std features several preprogrammed sound velocities for common
substrates. When measuring the thickness of acrylic windows, the user may either select
"plexiglass" from the gage
menu, or for best accuracy, make a simple adjustment to a known sample thickness or sound velocity.
The PosiTector UTG Std can be adjusted to a broad range of sound velocities spanning
from 0.0492 to 0.393 mils/µs
(1250 to 10000 m/s).
The PosiTector UTG Std's preset Aluminum sound velocity is ideal for measuring the thickness of aluminum panels on aircraft wings.
When multiple measurements are required, the Scan Mode feature of the instrument
enables 20 readings per second to be taken while the coupled probe is
dragged across the window surface. The result is a high-detail
thickness map of the window. As shown in Figure 2, the
Scan Mode of the instrument displays the total number of readings as well as the
highest and lowest readings. Not only will this provide the user with a
sampling of the thinnest and thickest readings attained from the substrate, but
the readings can also be stored and downloaded to optional PosiSoft computer
software by the instrument.
Figure 2 - Scan Mode: 20 readings per second.
Ideal for quick inspection over a large area.
Free Consultation
For current pricing or to order these
instruments, please contact us by telephone (315) 393-4450, fax (315) 393-8471,
or e-mail techsale@defelsko.com. If you require additional technical
information or have questions relating to your particular application, we
encourage you to take advantage of our years of experience in recommending the
best gage for your application.
During normal operation of an aircraft, micro cracks form on the outside of
passenger cabin windows due to commonly occurring elements such as dust,
sand, pollution, airborne volcanic acid and de-icing compounds.
Preventative maintenance programs that repair such micro cracks prior before
they become visible prevent high repair and replacement costs.
Global Aero Services has patented a robotic computer driven system that is
used for window restoration referred to as the Global CS1 Repair Machine.
The CS1 attaches directly to the exterior surface of the aircraft with suction
cups. The CS1 has four polishing heads impregnated with special formulas
that through robotic pickups and controls are used to polish and remove micro
cracks from windows. In approximately 15 minutes, the CS1 is capable of
automatically completing a window repair while restoring viewing clarity for the
passenger. As the CS1 begins work on the next window, an operator
simply wipes the window clean of remaining residue with a light cleaner and soft
cloth.
Why measure?
While the window restoration process can be repeated numerous times before
exceeding manufacturer suggested tolerances, it is still necessary to monitor
the remaining window thickness by measuring after each repair. Such
safety inspections are critical in aeronautical applications due to the
potential catastrophic events associated with a failure.
Considering that passenger planes may have over 200 windows per aircraft, and
that maintenance of cabin windows is rated as the 3rd highest maintenance cost
in the industry, a fast and affordable method of measuring window thickness is
required. Unlike mechanical measurements, ultrasonic inspections can occur
from one side of the window, while leaving it in place, lowering maintenance
costs and aircraft downtime.
Where is the market?
The Global CS1 operates on Boeing 727, 737, 747, 757,
767, 777; Airbus 300 through 321 series; Fokker 100; MD80 and MD90 Series; as
well as DC-8 and Dash-8. Due to its universal nature, the PosiTector UTG
can be used to measure restored window thickness on these or any such aircraft.
