nora110•10d agoMost Upvoted

Thought those $20 ultrasonic testers were a joke until I used one on a Cessna 172

Buddy brought his cheap ultrasonic thickness gauge from Amazon to check wing skin corrosion on my annual. I laughed when he pulled it out. Set it up, ran it on a spot near the fuel vent that looked fine. Came back 0.032 instead of 0.040. Pulled the skin and found pitting underneath I never would have caught. Has anyone else had a cheap tool actually save their ass on an inspection?

3 comments

3 Comments

ericj4510d ago

The real win with those cheap ultrasonic gauges isn't finding the obvious thin spots. Its catching the areas that look perfect to the eye but are already starting to corrode from the inside out. I had a friend who used one on his Piper fuselage near the battery box. Everything looked clean until the gauge showed 0.020 on a spot that should have been 0.040. Peeled the paint back and found pitting deep enough to see daylight through. That gauge paid for itself a hundred times over that day.

the_jessica10d ago

Borrowed one from a buddy after seeing his results on a Mooney wing. Ran it over the belly near the drain holes like the manual says and got a reading of 0.036 on a spot that should have been 0.050. I thought it was a fluke so I ran it again. Same reading. Third time still 0.036. Peeled the paint and found intergranular corrosion starting to creep out from the rivet line. Caught it early enough that a light sanding and some Alodine fixed it up. That cheap gauge found something my eyes never would have seen and saved me from a much bigger headache down the road.

taylorellis10d ago

That 0.020 reading with daylight poking through is the stuff of nightmares. Makes you wonder how many planes are flying around right now with corrosion hiding under a fresh coat of paint that someone slapped on without checking first. Did your friend end up having to do a full skin replacement on that section or was it a patch job? Ive seen battery box corrosion spread way further than you'd think once you start cutting into it, sometimes it runs along the stringers and you end up replacing half the belly.