Guys. Look at the attached image. It shows the factory drawing on how to drill in the spar cap.
The radii in the extrusion profile is not to be touched. That's what I mean with a standard pattern. If you have holes closer to the edge of the spar cap, going through the radius of the outer or inner sides, you are weakening the spar cap. Maybe not enough that it creates an instant problem, but it will be then the weak spot in your spar, where it will break first. It will flex more there and maybe crack easier. The tragedy of the Sebring breakup is that whatever the cause was for the breakup, be it the pull-up with two people or the aileron flutter, it can happen to you too. I experienced aileron flutter myself and I also was stupid enough to pull up from a dive doing 144 indicated ones. I survived. (My spar is like from the factory.) My thinking is: would any of you let your children fly with a known wrongly drilled spar that got signed off with a 337? What if they experience aileron flutter? Or just pull up for the fun of it? I surely would not let them fly. And the logical conclusion then is that I should not too. We have to make the FAA an offer. If we claim that the center spars are structural ok, holes or not, Mr. Caldwell can ground the whole fleet. Because when we claim that the holes drilled did not affect the spars strength, then ALL Ercoupe spars are in danger of breaking up in case of aileron flutter or a sudden pullup that you do when avoiding other traffic for example. I might add to my list of actions required a dye check of the spars upper caps , maybe not recurring. Hartmut To: [email protected] From: [email protected] Date: Sun, 27 Sep 2009 13:26:17 +0000 Subject: [ercoupe-tech] Re: ACS 8/14/09 - In-flight Breakup of Ercoupe 415-D, NTSB ERA09FA087 Also for number 4. If extra holes that don't follow a standard pattern, if they were approved by a field approved 337 there should be no required action. Kevin1 --- In [email protected], "Ed Burkhead" <e...@...> wrote: > > > > > > Hartmut suggests these possibilities for holes found in the center section > spar: > > > We should give reasonable advice on how this > > > amendment will look like. > > > > 1. First , no extra holes , no further action > > 2. Extra holes, documented - verify that it follows > > > an approved pattern > > 3. Extra holes, not documented - certify if it follows > > > the approved number and pattern > > 4. Extra holes not following an approved pattern > > > or number. Replace spar cap or add stiffener > > > provided by Univair ( has to be developed) > > > > At the least, I would suggest a second remedy to option 4: Provide an > engineering analysis by a DER or other qualified individual showing the > extra holes do not degrade the spar strength beyond required limits. > > > > For example, the designer's letter: > > http://edburkhead.com/Ercoupe/fred_weick_reply_on_holes.htm > > > > And, indeed, before an AD is issued or amended, the FAA should show that > spar holes degrade the strength beyond acceptable limits. So far, we have > only a single instance in which a spar failed, very possibly due to extreme > loads due to aileron flutter and/or a sudden high-g pull-up, possibly at > higher than normal airspeed. I question that this instance justifies > grounding aircraft due to the spar holes. > > > > As always, aircraft which have controls that don't meet the specifications > in ERCO Service Department Memorandums 56 and 57 are unairworthy. > > > > Ed > _________________________________________________________________ Show them the way! Add maps and directions to your party invites. http://www.microsoft.com/windows/windowslive/products/events.aspx
