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#31
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It is possible, in that last instant before wanting to hit the runway he could have pull back hard and created a peak load over the 150% structural limit on the wing. Extending the wing with the tip tanks could also increase the moment arm the load has to work on. It sounds like he was fully loaded with people and fuel and near max gross weight. There is also the possibility that he has done this maneuver many times before and over stressed the wing, creating fracture or deformation. This might have been the straw that broke the camel’s back.
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#33
02-26-10, 10:56 AM
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It's important to remember that the posted G limits are symmetrical. If he was rolling and pulling, inducing assymetrical G's, the aircraft's G tolerance is greatly reduced. While we won't know until the NTSB finishes the investigation, it appears much more likely that it's pilot error, he pulled a wing off, versus an aircraft mechanical failure.
The aircraft I flew until recently had Flint tip tanks. They are required to have (approximately) 12 gallons unitl the aircraft's gross weight was reduced (I don't remember the numbers). My technique was to fill the tips, put in the fuel required for the leg in the mains. I would burn the mains until they were about to go below 20 gallons per side, then transfer the tips to land with about 20 gallons per side, well in excess of the 45 minutes required.
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#34
02-26-10, 11:14 AM
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Pressurized G model POH states:
The airplane is certified in the normal category. The normal category is applicable to airplanes intended for non-aerobatic operations. These include any maneuvers incidental to normal flight, stalls (except whip stalls) and turns in which the angle of bank is not more than 60 degrees. In connection with the foregoing, the following maximum certificated gross weight and flight load factors apply: Gross Weight: T/O Wgt ........................................4700 lbs. Landing ........................................4465 lbs. Flight Load Factor: *Flaps up ......................................+3.8 -1.52 *Flaps down ..................................+2.0 *The design load factors are 150% if the above, and in all cases, the structure meets or exceeds design loads Maneuvering Speed .......................155 MPH *The maximum speed at which you may use abrupt control travel. Never Exceed ................................230 MPH Maximum Structural Cruising Speed .190 MPH Most modifications will not adjust the operating limitations. Way too much expense involved. Although the extended fuel cells increase gross weight (normally not for landing but take off and cruise) the operating limitations remain as published by Cessna. By speculation of the events, one would conclude that the pilot exceeded the operating limitations but don't rule out that there was some kind of damage or deterioration that was already present and the timing was not on their side.
__________________
Herb R Harney 1968 337C Flying the same Skymaster for 47 years
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#35
02-26-10, 11:43 AM
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Understood. But, 3.8 is symmetric G's; there isn't a published unsymmetric (rolling) G limit. All that is known is that it is less than the symmetric G tolerance, the aircraft is not stressed for to withstand 3.8G's in a rolling pull.
If he was at red line and pulled up abruptly, he clearly exceeded the airframe limits. If he did a rolling pull, he exceeded them to some unknown additional extent. It will be interesting to see the investigation results. He could have easily pulled the wing off a aero time airframe....
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#37
02-26-10, 01:58 PM
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Just for a visual, here is the location of Station 177. It is 46 inches from the end of the wing not counting the wingtip.
__________________
Herb R Harney 1968 337C Flying the same Skymaster for 47 years
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#39
02-26-10, 10:18 PM
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I was discussing this today with a friend who is a chief metallurgist for P&W, and he mentioned something that puts this into perspective, ie. apparently the bobsleds running at the olympics are pulling 5.2G's going 90mph in a lateral turn.
Think about that for a moment, and then consider that for this crash the guy was doing over twice that speed and his G inducing pull was vertical ! I don't know the math on this, because we can't calculate the "unknown pull-up" but I can certainly see how easy it would be to snap a piece of wing off given what we believe occured. Anybody want to bet a $100- burger that the word corrosion never comes up in the final report? "watch this"
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#40
02-27-10, 12:24 AM
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First and foremost...like everyone here.... I mean absolutely disrespect to the lost lives. I did not know them and I can only assume that they were very similar to me...love flying...enjoying life...everything was fun...until someone got hurt. S--- Happens. My gripe comes from the uninformed pundants blaming the airplane. The machine did its job.
This is all cessna needed to tighten the noose on their supplimental inspection extortion. Naturally there is no mention in the media (even the aviation media) of the fact that the accident aircraft had an OUTBOARD wing failure.....no-where near the wing-root that is the subject of the inspection. There is no mention in the articles that the left seat was a visiting pilot from Poland, the right seat (PIC) was a 2200hr ATP. The three pax were the children of the left-seater There were three other family members on the ground watching the take-off The plane was modified to larger 300hp engines and 3-blade props ( hinting that the owner liked "performance"...certainly not a crime or even remotely a "bad thing" but its an important piece of the puzzle) The plane was modified with extended tip-tanks (exactly like mine) which when empty reduces max maneuvering speed to 143kts ... at altitude...interpret that as reduced air density = reduced drag. Ergo, at lower altitudes or colder atmospheric conditions...greater desity....more resistance....even lower Max Maneuvering Speed) The plane took off (90kts), retracted gear) climbed to pattern alt ( 100kts) turned downwind (125kts @ 900' msl) turned base (140kts) decended on final, flaps up, gear up, (155kts) leveled off 50' agl (165kts) nosed up sharply at the far end if the runway (171kts) At which time the right wing tip snapped off and the plane rolled into the ground....but stayed significantly intact I'm no accident investigator, but I interpret all that as a pilot doing an impromptu airshow for visiting friends...no problem...until you exceed the placarded performance limitations of your tip-extensions. Then s--- happens and you go from pilot to farmer in about...3 seconds. But since the words "skymaster" and "wing" are used in the same article, it's a foregone conclusion that the 337 fleet should just go ahead and start lubing-up in preperation for cessena's regulatory boon-doggle. The articles also don't mention that in the 2000+ production aircraft in 40+ years of military and civilian flights (including the rollercoaster rides of being an FAC "hedge runner").....not one has had the failure that the new inspection is supposed to address. Oh well....I'm justglad that the supplimental inspection is SUPPOSED to be for commercial operators ..... For now.... But we are all waiting for the other shoe to drop. I know I preaching to the choir and I'm still a new comer around here. But it just infuriates me to have the media implying it was the airplanes fault. I absolutely LOVE my skymaster. I did years of research that lead me to it. I've read and summarized every single 337 accident on file with the NTSB and I've made cross comparison charts with other types. The SkyMaster isnt perfect, but it is a DARN good plane if it is used properly...and is very forgiving if it is used improperly. But everything has its limits. And it irritates the crap out of me that an unfortunate event resulted in the death of 5....tragedy for their families and friend....and will almost certainly have profound, possibly devistating results on the rest of us, too. Again, no disrespect for the dead or their families. But, again, assuming he was anything like me, he would be the first to say "I was having fun and didnt pay attention to my airspeed...and it caught up with me. It wasn't the plane's fault...it was the PILOT IN COMMAND." Just my rookie opinion, and probably not a very popular opinion. Cole Reed
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#42
02-27-10, 10:17 AM
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Actually N5ZX, there was a bit of local coverage in the Asbury Park Press and Newark Star Ledger regarding the followup and "human interest" portions of this story. Some points are and will always be open I'm sure, such as who was flying the plane since the owner "Jack", was in the left seat, but "George", who had all of the ratings was in the right seat? Wojciech (George), was also an instructor at Trenton-Robbinsville and there was no reported or known relationship other than the other three passengers, Andrew Zajaczkowski and his son along with a young cousin were friends of the owner.
The problem is that much of this appears in the electronic media, that is, on the web pages, and then goes off into the blue a few minutes after "publication". For instance, on NJ.com .... type in "polish boxer" and there is an article on a boxing champ who turned down a seat on the flight. I'm not a member of the press, but have been doing a follow up for a friend who covered the story and we came to essentially the same conclusions. I had some questions regarding "177" and the fact via the NTSB, that he took on 90 gallons.
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#43
02-27-10, 11:04 AM
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I have tip extensions from Owen Bell's "Aviation Enterprises" as with his winglets and tail boom fairings, air conditioner, etc. I see that there is a winglet in the accident plane's wreckage, and mention of tip-tanks in the NTSB report, along with mention of the engine upgrades (possible sky rocket conversion).
My tip extensions only add 2' to each side, giving me a total wingspan of 44'6" (including the winglet / stol droop assembly thingie) the NTSB says that the seperated section was 6', implying that the extended tip was intact and actually survived the impact of that seperated section coming to rest. I make no pretense of being an expert. I dont believe in the term "expert" since (in theory) we are always learning....which means there is a great deal out there that we dont know. Much of what I say is simply me talking though my thought processes in hope that others will point out thinking errors which might keep me from duplicating the results. OldYuki, I was absolutely not referring to any prior message from you (or any other memeber). Admittedly I am at fault of abusing the forum and simply using it as a venue for random bitching....I hadnt even taken the time to read the other entries. My appologies for the generalized rant. But I live in Austin, and have had to suffer through rampant misinformation concerning the idiot who rammed the office building with his cherokee. Way too much rush to "scoop the story" not enough effort to check the facts. In your case, OldYuki, I applaud your efforts and to seek out answers and wish that others in the media industry shared your professional ethic. I also thought it was odd for the accident plane to put-on 90 gallons (3 hours) of fuel for what the family said was to be a local sight-seeing flight. I think this implies that there was possibly not much fuel on board before fueling. I speculate that would increase the "zero fuel weight" leverage effect, combined with the added lift on the wing tips....means lots of force being applied in the middle. Low density altitude increases aerodynamic drag...further increasing the forces at play. Again, I never want anyone to think I was implying that either of the front seaters were "bad pilots". They were having fun, enjoying their lives, and enjoying their plane. They just APPEAR to have played on the wrong side of the safety envelope. We'll know more next year when the NTSB makes their final report. For now....I think I'll just keep my numbers within the placarded limits. When all else fails....read the instructions. Thanks all, and I appologize again for my ranting. I am usually MUCH more restrained, but am easily flustered when folks (outsiders) make assumptions that this supports Cessna's agenda and derails the argument against their sudden interest in our fleet. Cole
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#45
02-27-10, 07:27 PM
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thanks ..
Cole, I sure didn't take any offense at that at all and I know where it's coming from indeed. Media off the shelf and "out of the can" comments" like ... "the flight from an uncontrolled airport" ... or ... "the pilot failed to file a flight plan" ... things like this indeed will light my short fuse.
My friend will most likely be asked to do the follow up on this story and he just wants to get thing right and know what questions to ask or .. not to ask. All of the data that may or may not factor has had us scratching our collective .. things like the fuel, STOL and lastly the mod to 300 hp .. or the report that he took on 90 gallons. Well, it's way beyond "common knowledge" for the average Joe. Great forum and a great crew .... so thanks again .... going to the source, the guys who own and love these ships (is my envy is showing?) ..
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