T-6 "crash" (everyone OK)

[RyanShort1]

http://www.orlandosentinel.com/news/loc ... 6373.story

I guess a ground loop constitutes a crash to the news media?

Ryan

[Rajay]

I just looked at the pictures attached to that story in the Orlando Sentinel; it "crashed" alright. It won't be flying again anytime soon. It looks like the left wing is bent and the spar is probably buckled. (It would kinda have to be, duh.)

I always thought that T-6's were tough old birds, so she must have lost it pretty early in the landing roll out - while there was still a lot of kinetic energy. It looks like it swerved right and the left main landing gear collapsed, dropping the airplane hard onto its left wing.

What a shame...

[Jack Cook]

Has been for sale on couresy for quite a while.
"Has" being the relative word here

[mustangdriver]

So was she the owner of this aircraft? Or just getting some time in it? Glad that she was able to walk away from it.

[Jack Cook]

I love the report's line "The plane swerved off the runway"".
Well you stupid SNJ what did you do that for.
Both groundloops I was in I can honestly say it wasn't the airplanes fault

[Rajay]

Wonder what a pranged T-6 sells for? Undamaged engine would still make it expensive. Guess it goes to Barnstormers now!

I wouldn't say the engine is "undamaged." It may not be obvious, but in the last photo posted on the Orlando Sentinel Web site, you can see that the prop is bent. There definitely was a "prop strike" when the gear collapsed and the wing hit the ground.

I would speculate that given the nature of AD 56-06-02, which applies to all P&W radials, a sudden stoppage could have easily broken or pulled loose some cylinder hold-down studs.

[Chunks]

I don't think it's the same one on the courtesy site, unless they've made some paint, canopy, cowling and prop changes.

Chunks

[Matt Gunsch]

I would speculate that given the nature of AD 56-06-02, which applies to all P&W radials, a sudden stoppage could have easily broken or pulled loose some cylinder hold-down studs.

I am not sure where you are reading anything about sudden stoppage affecting cylinder base studs, but I would love to hear your theory.

Here is the text of the AD..........

56-06-02 PRATT & WHITNEY: Applies to All Models Engines.

Compliance required as indicated.

As a result of engine fire reported due to cylinder failure as a result of stud failures, the following must be accomplished to reduce cylinder and stud failures:

A. If a cylinder flange attaching stud fails during engine operation, the adjacent studs may be subjected to severe overstress. The same is true if an attaching nut becomes loosened to the extent that there is clearance between the nut and the cylinder flange. If more than two adjacent studs have broken, or the nuts have become loose, there is a probability that the cylinder flange has been overstressed.

B. If, during line inspection or at engine teardown prior to overhaul, a nut is found to be loose or there has been failure of a stud, replace that stud and the two adjacent studs.

C. If more than two adjacent studs have failed or if more than two adjacent nuts are known to have been loose during engine operation, the cylinder should be scraped or rebarreled and all the studs on the cylinder mounting pad replaced.

D. If only two adjacent studs have failed or two adjacent nuts have been found loose, the cylinder should be replaced, but it need not be scrapped provided that the nuts adjacent to the failed studs or loose nuts are found to be at least to minimum torque and that the cylinder flange has not become distorted more than 0.003 inch; also, that the flange and area above the flange are magnafluxed and show no crack indicators. If the bottom of the cylinder flange is not perfectly flat, but is not distorted more than 0.003 inch, it should be lapped flat before reinstallation. Before a replacement cylinder is installed, the crankcase studs immediately adjacent to the two broken or loose ones should be replaced.

E. During cylinder installation, securely tighten the cylinder flange attaching nuts.

[Rajay]

Yeah, I have the text of the AD.

As I said, I was just "speculating" (I never said that I read it in the AD) that since, per the AD, anytime you just look at the engine during normal maintenance, after normal operations, you have to be concerned with the cylinder base studs breaking or pulling loose and therefore the cylinders getting loose...
that I wouldn't be at all surprised if the severe shock of a sudden stoppage caused the same thing to happen.

If a piston stops very suddenly or even kicks back because of a prop strike, and the valves on that particular cylinder just happened to be closed at that instant, the build-up of pressure inside the cylinder would be tremendous. Certainly enough to potentially overstress the base studs.

I was just throwing it out there for sake of conversation.

I was also wondering, but didn't have any specific experience to go on, whether radial engines, especially single-row radials, are MORE or LESS likely to have crankshaft run-out issues after a prop strike. On the one hand, they are relatively shorter than in a flat (horizontally-opposed) engine - which would equate to a shorter lever working against them. On the other hand, the longer cranks of the flat engines are also supported by more bearing surfaces along their length.

I spent 10 years working for an engine overhaul shop that had a "sister" prop shop under the same roof. As both a pilot and senior mechanic, I was often the guy sent on the road to inspect and ferry back a customer's aircraft after a prop strike. I think that they were always flat engines in my experience - and also I can't remember a single one that was out of limits beyond the point that it was acceptable for me to bolt up a spare prop and fly the plane home.

Matt, you're a T-6 guy, right? You probably have lots more experience with radials than I do (I'm always looking for new opportunities to work on them...but,) In any case, what is your perception of the relative vulnerabilities or strengths of radial engines in regard to prop strikes or sudden stoppage damage?

[Rajay]

Yeah, I have the text of the AD.

per the AD, anytime you just look at the engine during normal maintenance, after normal operations, you have to be concerned with the cylinder base studs breaking or pulling loose and therefore the cylinders getting loose...

Except that I just didn't read it thoroughly enough this time around, or the first time either apparently. I didn't catch the "As a result of engine fire..."

I could have sworn, based on my memory of the first time I came across this AD years ago, that it seemed to be requiring you to inspect the cylinder studs (and sign off the AD) anytime you were close enough to see them.

My bad. This time, I have to admit that I just didn't know what I was talking about....

[Matt Gunsch]

On a 1340 prop strike the blower gears are the ones that get damaged. The blower is turning 10 to 14 times, depending on the ratio, of the crankshaft speed and when there is a sudden stoppage all that energy stored in the blower impeller has to go somewhere, which is into the blower gears.

On a engine with a reduction case, the reduction gearing takes the blow.

Cylinders don't know anything than up and down motion, and a sudden stoppage does not do anything more than what they are designed to handle, if anything, the load is less than the stresses of operation. There cannot be a pressure increase unless your blower kicks in just as the prop hits, and even then, the pressures in the cylinders would not be any more than normal operation.

[Glenn Wegman]

Cylinders don't know anything than up and down motion, and a sudden stoppage does not do anything more than what they are designed to handle, if anything, the load is less than the stresses of operation.

You might want to think about that a little!

Where does the cylinder pressure from combustion go if the propeller blade is against something (the pavement) and the crankshaft cannot rotate freely?

[Matt Gunsch]

Cylinders don't know anything than up and down motion, and a sudden stoppage does not do anything more than what they are designed to handle, if anything, the load is less than the stresses of operation.

You might want to think about that a little!

Where does the cylinder pressure from combustion go if the propeller blade is against something (the pavement) and the crankshaft cannot rotate freely?

put it this way, I have never seen a cylinder damaged by a prop strike, nor have I ever read anything in a maint or O/H manual that says to inspect the cylinders in the event of a prop strike. If you have anything in writting that says to inspect cylinders after a prop strike I would like to see it.

[Glenn Wegman]

....In other words, you are unable to answer the question?

My question was in reference to cylinder pressure. You claim it would be less than in normal operation. Please explain.

[Matt Gunsch]

....In other words, you are unable to answer the question?

My question was in reference to cylinder pressure. You claim it would be less than in normal operation. Please explain.

Most prop strikes occure at idle, so the cylinder pressures would not be that great.

If you have any other info, instead of playing games, show your hand.
I have looked thru 43.13, cam 18, the R-1830 overhaul manual, and the A&P engine handbook.