Torque!

[retroaviation]

This is one of my all time favorite photographs. It was taken by Neal Nurmi, back in 1991. If I remember what he told me correctly, he snapped the photo just seconds before the Rare Bear blew it's engine (there is also great footage of this event from the little video camera on the vertical fin). When Neal developed this photo the next day, he immediately took it to the crew of the Bear (at the time) and they looked back in the aft section of the fuselage to find several (or so I'm told) bulkheads cracked and busted.

To me, the single best word to describe this photo is "torque." You can see the paint lines on the cowling displaced, along with the wrinkles in the fuselage.........




Gary

[Warhawk]

In other words Gary you're saying it's probably a good thing the engine let go when it did.

Thats scary to look at that and see how out of shape it is.

[retroaviation]

In other words Gary you're saying it's probably a good thing the engine let go when it did.

Thats scary to look at that and see how out of shape it is.

Well, I dunno if it's ever a good thing when an engine lets go. However, I'd say it was a good thing that this photo was taken, because it was supposedly this photo that caused the crew to go back and take a good close look at the rest of the airframe. I'm sure there are people on this forum that could answer that with more facts than what my pitiful memory can recall though.

I would imagine that the airplane was beefed up substantially and is surely in much better condition now, but I really don't know.

I just think it's a cool picture.

Gary

[Warhawk]

Yes, it's a bad thing when an engine lets go. I just have this image in my head looking at that of the engine leaving the airframe and continuing on while the pilot sits there looking like Wile E. Coyote.

It is a very neat picture though.

[Jack Cook]

I was with jcw once in the T-6G when the 1340 blew-up. I can easliy
remember the feeling of the force going through the a/c and throwing
it about 30' to port (that's left BTW). A 3350 going south was be really ugly

[sdennison]

Torque, yeah that's "tighten it until it breaks and then back off one turn"

[bdk]

You can see the paint lines on the cowling displaced, along with the wrinkles in the fuselage.........

Wrinkles on the bottom side of the fuselage, if on both sides, would indicate that the skins are under a compression load. In a steep turn (high positive "G" loading) the tail is pushing down very hard to keep the nose up, indeed putting the lower portion of the fuselage in compression. The horizontal stabilizer is counteracting the forward pitching moment of the wing airfoil. The upper fuselage skin, in tension, gets stretched tight so you don't see any deformation.

I have been in formation next to a polished T-28 and seen the talicone wrinkle back and forth as we bounced around in turbulence. That is normal though as no airplane is infinitely stiff. If you look at a B-52, you can see wrinkles in the fuselage and that is when it is sitting on the ground stationary.

I do not doubt the story about damage in the tail in the least, I only suggest the cause was most likely not torque. This aircraft has seen a lot of time in steep turns at high speeds in gusty and turbulent conditions, so highly stressed areas could suffer from fatigue damage and crack. This aircraft also suffered an accident at one time (cartwheeled as I recall in the early 60s) so there may have been some unseen damage from that incident that may have contributed to the condition discovered.

The displacement of the paint lines is clearly due to torque (unless they installed the cowling crooked!). I'm only semi-knowledgeable in aerodynamics, but I would expect that the engine torque is mostly reacted by the ailerons with a little help from fin offset (which is probably set for cruise speed). At the speeds seen in Reno it doesn't take much aileron displacement at all to counteract the torque.

[sdennison]

Wrinkles on the bottom side of the fuselage, if on both sides, would indicate that the skins are under a compression load. In a steep turn (high positive "G" loading) the tail is pushing down very hard to keep the nose up, indeed putting the lower portion of the fuselage in compression. The horizontal stabilizer is counteracting the forward pitching moment of the wing airfoil. The upper fuselage skin, in tension, gets stretched tight so you don't see any deformation.

When I look at this photo, I don't see much elevator angle or horizontal stabilizer activity and I can't tell the rudder angle. Could this be a combination of torque and rudder deflection compressing this side of the fuselage and placing the opposite side of the fuselage in tension?

[bdk]

You probably don't need much elevator deflection at 475+ MPH to pull 4 or 5 Gs. You might need a little rudder to initiate and then recover from the turn, but you shouldn't need to manipulate the rudder during a steady state turn.

What would react the torque on the empennage that would cause the fuselage to twist? If there was no reaction to the torque, the airplane would be rolling. Ailerons control the roll axis. Of course we could just be seeing something momentary like I did on the T-28 fuselage but those buckles look pretty deep!

[skybolt2003]

Amazing photo . . .
I used to own an SGS1-36 glider. It's an aerobatic all metal glider. The first time I loaded it up with a little G's I heard a sound that could only be described as someone crushing a beer can – I actually looked back to make sure the tail was still attached. It was disconcerting as hell. In a glider you can hear stuff like that going on.

[Canso42]

I have several friends who are WWII VP Navy vets with time in PBY's PBM's and P5M's.
One of them said "nothing lets go like a 3350!" This comment was first made after seeing a cylinder come through the fuselage on a P5M.

Canso42

[Steve Nelson]

I was visting Pima Air and Space museum a couple of year ago, and outside their engine display building was a section of engine cowl mounted on a post, with a cylinder head stuck halfway through it. I assumed it was somebody's joke, but a museum staffer told me it happened as they were ferrying an old Convair propliner to the musuem.

Unfortunately, I got distracted by some of the museum's other really cool stuff and forgot to take a picture.


SN

[retroaviation]

I was visting Pima Air and Space museum a couple of year ago, and outside their engine display building was a section of engine cowl mounted on a post, with a cylinder head stuck halfway through it. I assumed it was somebody's joke, but a museum staffer told me it happened as they were ferrying an old Convair propliner to the musuem.

Unfortunately, I got distracted by some of the museum's other really cool stuff and forgot to take a picture.

SN

You mean this one?



Gary

[Jack Cook]

I'm no mechanic but I'll that just doesn't look right

[oscardeuce]

That's "air cooled".