crashed

[Seagull Tango]

A discussion with another old Skymaster pilot raised an interesting discussion point on the impact of ground effect.

An aircraft flying at or very nearly at Vne, descending into ground effect, would see the airspeed increase as the wing became more efficient, with the concurrent reduction in induced drag, assuming the power setting remained constant.

A second point is whether there is any impact on the loads and stresses if an aircraft enters into ground effect in a bank -- i.e., one wing is in ground effect, while the other is not.

I don't know if the load changes related to ground effect have ever been studied AT HIGH SPEEDS. Does anyone have knowledge of that?

To my knowledge, ground effect research is typically focused on low speed impacts, improvements in the efficiency of the wing while in ground effect at the extremes of the envelope (meaning that the aircraft is able to fly in ground effect at an extreme weight or temperature, but is beyond the envelope and unable to climb out of ground effect until sufficient weight of fuel is burned off, etc.).

[oldyuki]

And so ... we separate the proverbial men from the boys. I know, I know, just go sit in the corner and keep quiet.

[Roger]

I did my first aerobatic - upset training today and the instructor was explaining to me how in a banked dive when attempting to pull up, the "up wing" is loaded with about 50% more G's than the lower wing. He went on to explain how in most accidents where a plane breaks up in the clouds, they usually find the outboard last 3 feet of one wing, about two miles back in the flight path. This because when the pilot tries to pull up and out of his dive/spin, the up wing usually break away at the end due to the over-G.

The insturctor knows his stuff, and trains upset for both the Army and Navy.

I asked him then if he had read the Skymaster crash in NJ, which he said he did. His opinion was that it was a banked turn / pull up that over stress the higher wing.

Meanwhile upset training was the most fun I've had in years

[CO_Skymaster]

I had to think about that for a moment and where the forces are on the wing, but he is right. The up wing has the downward alerion deflection, so that part of the wing has the higher angle of attack and higher loading. Augh... you're taking me back to my aerodynamics classes. :-)

Karl

[N5ZX]

Questions:
The accident A/C was using rwy 32.

The debris field was distributed along a 360 heading from the departure end of the rwy indicating a right deviation from a 320 rwy heading...right wing was lower than left (right bank).

The right wing tip seperated from the right wing and seems to have peeled up and rolled over the fuselage, impacting the rear engine nacelle. This would seem to indicate that the bottom of the wing was the "leading edge", otherwise wouldnt the seperated portion have impacted further back on the A/C...like on the tail boom, etc.

The NTSB preliminary report says that the right wing spars show indications of DOWNWARD bending...the seperated portion folded UP and over....what could cause that?

The plane flew a perfect, pattern. Descended at an unacceptable speed with Flaps and gear up and spoiler apparently not deployed...they were TRYING to go fast.
15:44:19 332* 900' 120kts....I normally climb at 100
15:44:50 240* 1100' 137kts....I normally do cross-wind at about 110
15:46:50 156* 1400' 148kts....I normally start slowing to 100 around mid-field..
15:47:00 062* 600' 171kts....My base-leg is 100... 100 on final...90 over the fence....80 on the numbers (or somewhere there-abouts).

The last radar return had them on Base-leg at 600' msl (450' above Field Elevation) at 171kts and accelerating.

Max maneuvering speed for a "normal" P337 is 155kts. Max Maneuver for the Aviation Enterprises wing tip extension tanks (if empty) is placarded at 125kts.

And to make a 90 degree turn and descend 800' in 10 seconds (according to the radar sweeps) sounds like "abrupt maneuvers" to me.

Could this HARD left descending turn (forcing the right wing up) have flexed the right tip downward.... bending the spar, weakening it but still allowing the pilot to maintain the controlled high-speed low pass along the rwy until he pulled up "sharply" and the weakened spars gave-way?

Certainly not arm-chair quarterbacking....just trying to get my head around the physics and aerodynamics and yall seem to be excellent resources.

Thoughts?
Cole

[jack374dn]

As I have stated in an earlier message, my super skyrocket, 374DN, @ 32" M.P., 2400 RPM, @ 2000 feet MSL, nose down 200 FPM, @ 1000 feet MSL = RED LINE [VNE]
OAT = 85 F, DP 52, SMOOTH AIR, dead still ...

Jack

[CO_Skymaster]

I was looking at Cessna Skymaster Videos on U-tube and came across a video of someone making a high speed low pass. I noticed that the aircraft made a sharp turn close to the ground before the pass. I wondered if this is what the pilot was trying to do when the accident occured.

http://www.youtube.com/watch?v=c3KyePDEoQQ

Karl