Could the stressed components have been present before he bought the plane or have occurred prior to this flight when the pilot was alone at 8,000 AGL? I guess we need to take the facts as known to the investigators.
On Sat, Mar 6, 2010 at 9:22 PM, Ed Burkhead <[email protected]> wrote: > > > > But what CAUSED negative g-load sufficiently strong to break the spar in a > negative g manner and eject the seat/pilot/passenger out of the plane? > > I cannot imagine a pilot with the experience and ratings listed doing a > barrel roll or pushing negative g's close to the ground, over civilization > (the golf course). > > I could, maybe, understand a high speed low pass with a sudden pull-up. > I've seen this done perhaps a hundred times at various Coupe flyins. May I > say CLEARLY that I think this is a BAD IDEA. > > Any plane with slop in its control system can get surprise control surface > flutter when it encounters an airspeed and load combination that allows a > resonant vibration to get going. I had that happen to me and am very, very > glad that I reacted correctly and almost instantly (turned the yoke to load > the aileron control system and pulled [with moderation] up to slow down). > > I'm not any kind of genius pilot. In retrospect, I think I must have been > thinking about flutter and been alert for it as I did my power-glide to see > what 144 mph felt like - only that would explain how I diagnosed the > vibration and did the right thing so quickly. > > You'd better believe I got my control system tightened up to specifications > after that and never again tried to power-glide up toward 144 mph!!!! > > The NTSB probable cause report mentions nothing about flutter being > involved > in the accident chain other than repeating the quote from the ATP pilot who > said he observed both ailerons fluttering. I wish they'd addressed this - > but, I suspect they just had nothing solid to go on. > > To me, vibration sufficient to shake the rear windows out of the plane, > knock the inspection hole covers off the plane and shake PAINT CHIPS off > the > plane might, just possibly, be important. > > I'd urge everyone to do the checks necessary to see if your control systems > are within specs. > > And, please, don't show off by doing a dive down to a high speed pass with > or without a sudden pull-up at the end. > > JMHO > > Ed Burkhead > > > > -----Original Message----- > > From: [email protected] <ercoupe-tech%40yahoogroups.com>[mailto: > [email protected] <ercoupe-tech%40yahoogroups.com>] > On > > Behalf Of William R. Bayne > > Sent: Saturday, March 06, 2010 8:14 PM > > To: ety Ercoupe > > Subject: Re: [ercoupe-tech] Re: NTSB probable cause... > > > > > > Hi Craig, > > > > You make an excellent point. They may well have MEANT that > > "cross-sectional strength" was reduced by 10% using "design code" > > practices. > > > > But what they SAID was that the "cross-sectional AREA of the top spar > > cap" was reduced by 10%! On that basis that I deemed the COMMENT > > "utter nonsense". Professionals should express clear and accurate > > findings in any accident report. > > > > The NTSB seems to conclude that aerodynamic stresses substantially > > exceeding applicable design criteria preceded the observed catastrophic > > structural failure of subject wing and spar assembly such that even had > > the "extra" hole not been drilled the structure would have likely > > failed in much the same way with unchanged result. If the possible > > reduction in "cross-sectional strength" from this one non-factory hole > > was dwarfed by the structural design load safety factor, no one would > > bother to "do the calculations". > > > > Regards, > > > > WRB > > > > -- > > > > On Mar 6, 2010, at 14:39, craig wrote: > > > > > The 10% figure probably came from design codes. Any hole no matter > > > how small and the design codes say that you must at a MINIMUM deduct > > > 10% of the structural strength of the metal. In any case if you drill > > > more holes you would have to do the calculations to determine how much > > > tensile strength remains.ie, drill enough holes and you could end up > > > with NO tensile strength left. > > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > > > >
