crashed

[Roger]

A 4500lb car travelling at 180 mph experiences a 20G force if stopped in 50'. Now granted the accident aircraft did not "initially" stop in 50', but instead apparently changed his vetor angle at the bottom of the dive. An angled stop is less severe than a 90' stop as well. That being said if instead of "stopping" his dive he over pulled, then his vector angle change was more severe than a "stop", albeit beginning at an angle.

In the heat of fear, if he pulled this plane up at the last minute, especially given the large elevator on the 337 which will do a damn good job stopping or deflecting the descent, I can see the plane stopping it's descent in a distance that would cause some serious G's loading of the wings. Meanwhile if there were alterations to the tips and added weight of fuel in the tips, this is a no-brainer.

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[CO_Skymaster]

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.

[Kim Geyer]

I think at wing station 177 is where the autopilot bridle cables go through the wing spar

[Ron Moore]

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.

[hharney]

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.

[Ron Moore]

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....

[Roger]

In fact isn't the whole idea behind a screaming dive down to the runway with a last minute pull up, done in a manner to exert G-forces on the passengers? It's like a roller coaster ride.


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