The FAA has opened up the Piper Cherokee spar corrosion AD for comments again after AOPA pressed for less expensive ways to address the potential problem. The AD, which was initially proposed in November of 2017, will continue to affect more than 11,000 Cherokees and Cherokee Sixes but some alternative methods of compliance suggested by AOPA have been included and the comment period reopened until Sept. 18. The revised AD also includes information from Piper “to add a minimum thickness dimension for the top inboard wing skin and to include procedures for reapplying corrosion preventive compound if removed during the inspection.”
The original AD called for cutting new inspection ports in the wings because the area of the potential corrosion is not easily accessible from existing ports. Among the AMOCs suggested by AOPA is the use of borescopes to look inside the wing through existing holes.
My old idea of the inclusion of micro-cameras and LED lighting in difficult-access areas is looking like a rational design choice.
I was able to get an iPhone on a telescoping selfie stick into the areas and have great pics of a spotless spar.
This is great news for Cherokee owners! Finally, the FAA is beginning to realize that the technology that has come about in just the last few years is better than their ancient archaic ways. Now if they will just help me get rid of my 50 year old instruments that weigh 45 pounds…(without spending $35,000)
Check out Dynon.
Dynon is still not that cheap. the basic 7″ screen system with autopilot for the 172 is $13,200, installation is 90-150 hours I spoke to a avionics shop in dallas and was quoted around $10,000 for install. then add $6300 for a garmin GPS nav com and you are up to $29,500. on the other hand 10 years ago this would have been over $100,000. My biggest FAA complaint is that due to certification costs and the lack of competition that results an engine overhaul for a 250-300hp 6 cylinder Lycoming or Continental costs more than a fully loaded dodge challenger R/T. Not a new engine just an overhaul.
Flexible borescopes have become widely available and affordable. It does not make sense to go carving new holes in an aircraft when you can snake a scope in from nearby and get great pictures of the area in question. Anyone who owns an aircraft (especially legacy planes) should probably buy one for their own use. I have a couple and have discovered many other uses for them in addition to peering into hidden places on my plane. The lesser expensive unit cost less than a fill up of 100 LL.
This is a “dissimilar metal corrosion” issue, occurring in aircraft exposed to consistent high levels of humidity and/or moisture.. When moisture is introduced between the steel spar and aluminum skin, that were constructed, sometimes, with no green “ zinc chromite” coating, but rather just bare metal.. MZero C-172 incurred wing damage, during a passing Oshkosh storm.. The repair revealed extensive “dissimilar metal corrosion” damage to the spar, in an area not easily seen during inspection.. The rebuilding of the wing included, a coating of zinc chromite, and additional inspection panels for future inspections.. If you want to pony up on the expensive gadget/s, knock yourself out..