Am I incorrect in thinking that if you see no corrosion anywhere else
on the plane it is
unlikely to have serious corrosion in hard/impossible to see areas?
Does not the "Swiss Cheese AD" or alternate method in that AD address
these areas?
I wonder if any of the severly corroded Ercoupes had spent their
lives in the Midwest/etc.
well away from salt water exposure.
Dan Caliendo
Ercoupe Mach 0.14
3658H
On May 25, 2009, at 5:45 PM, William Rich wrote:
I've searched for a suitable Ercoupe continually for the last 6
weeks and I'm an ace Google researcher. One theme that is leaping
out at me is CORROSION. As an unbiased newcomer, I can clearly see
corrosion is the proverbial elephant in the Ercoupe living room.
This infamous NTSB accident finding speaks volumes:
http://www.ntsb.gov/NTSB/brief.asp?ev_id=20040315X00324&key=1
The key statement is:
"Comparison of the inspection requirements in the Service Bulletins
and AD's to the area where the corrosion was present in the
accident aircraft revealed that none of the inspection methods
would likely have found the corrosion."
The response to this blunt warning is varied: some have exercised
due diligence and performed invasive evaluations of their
airframes, including skin removal, ultrasound, and scraping if
required; while others have chosen to focus on the Red Herring
aerobatic component of the accident report.
The vivid pictures in this well known submission are stunning:
http://www.ercoupe.info/?n=Main.Hartmutscsection
Key statement:
"I found some surface corrosion on all parts where previous primer
applications did not reach. Nothing major. It just needs a cleanup
and prime and done. Then I found what we all are afraid of,
something which looked like corrosion on the inboard spar of the
trailing edge on the right side of the center section. It is hard
to see, because one has to look through two lightening holes, with
the wings detached, And even then you can see just a fraction of
the rib."
The corrosion in this account almost went undetected except for the
due diligence of the owner.
Corrosion even went undetected during the refurbishment of G-BKIN:
http://www.popularaviation.com/Ercoupe/PhotoGallery.asp?Page=6
Key statement:
"Shortly after this photo was taken G-BKIN was shipped to the
States to Seattle (Tacoma) rebuilt and flown there for a short time
before being scrapped due to corrosion in the center section AD."
The airframe was "rebuilt and flown" prior to detection of
corrosion requiring scrapping.
The important thing I've learned in all this is:
SERIOUS CORROSION OFTEN WAS YEARS IN DEVELOPING AND WENT UNDETECTD
DURING NUMEROUS ANNUAL INSPECTIONS AND EVEN REFURBISHMENT.
I personally will exercise extreme caution in my Ercoupe search and
insist on rigorous assurance that a prospective airframe is safe.
The Ercoupe is an endearing aviation classic. It has both a trendy
retro-modern look and a technical execution that remains
competitive in the 21st Century. Unfortunately, it is those
virtues that belie it's extreme age and possible hidden weaknesses.
In my less than humble opinion, it is likely some operational
Ercoupes should not be flying, and for some of those, the price of
remediation is unacceptable. These are old airplanes, the numbers
are dwindling, and the task of finding a safe and reasonably priced
airframe is difficult.
