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R-1820 in B-17 crash

 
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Fri Dec 18, 2020 20:29    Post subject: R-1820 in B-17 crash Reply with quote

This guy goes through the report.
https://www.youtube.com/watch?v=1HNsQuLrOqg

The comments about the cylinder corrosion? Very likely from what was used to put out the fire. There was no mention about fire or heat damage to the magneto's, that could affect the test results.
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kmccutcheon



Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA

PostPosted: Fri Dec 18, 2020 21:26    Post subject: Re: R-1820 in B-17 crash Reply with quote

rwahlgren wrote:
The comments about the cylinder corrosion? Very likely from what was used to put out the fire.

Concur. The corrosion that is visible looks new to me.

rwahlgren wrote:
There was no mention about fire or heat damage to the magneto's, that could affect the test results.

That magneto was worn out and improperly assembled to the engine. Excess heat might have caused the coil insulation to break down but would not affect the primary and secondary winding resistance. Excess heat might have changed the condenser's leak-down rate.
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mksmith



Joined: 12 Dec 2016
Posts: 35
Location: Columbus, Ga

PostPosted: Sun Dec 27, 2020 10:30    Post subject: Cylinder corrosion Reply with quote

I'm skeptical whether or not that amount of corrosion would have been caused at the scene during the initial and later recovery efforts. That said however, the investigative teardown occurred Feb 11-20, four months later so when these pictures were taken, who knows what the condition would have been at the time of the accident.

You can find the information here:

https://data.ntsb.gov/Docket?ProjectID=100356

Item 37 Page 69


On the other hand, given all the other signs of poor maintenance. Both of #4's magnetos P-leads were separated from the housing, the left one being removed completely and grounded to the housing rendering it inoperative, I imagine this should have been caught during a mag check at run up.
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rwahlgren



Joined: 15 Aug 2003
Posts: 324

PostPosted: Fri Jan 29, 2021 23:46    Post subject: Reply with quote

https://www.youtube.com/watch?v=9x1TCMftngU
Start At 11:46


I do not agree with these guys.
I like how he says no damage to the cylinder, he should look again.
I didn't see signs of detonation, did they look at the piston?
Don't they know even a connecting rod bending hydraulic lock usually will not split the head. At 12:30 its the force that distorted the cylinder that split the head. He says when you look at the metallurgy of it??
Sorry guys the NTSB was correct on this.
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kmccutcheon



Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA

PostPosted: Sat Jan 30, 2021 07:47    Post subject: Reply with quote

rwahlgren wrote:
I do not agree with these guys..


I concur, at least partially. A #5 piston image appears in in the Powerplants Group Chairman's Factual Report
https://data.ntsb.gov/Docket/Document/docBLOB?ID=11496506&FileExtension=pdf&FileName=B17%20BDL%20PP%20factual%20final-Rel.pdf
and does indeed show evidence of detonation. However, the head damage is, in my view, more consistent with ground damage. Perhaps the head was weakened by low-cycle fatigue, but the analysis did not go that far. The real takeaway from this report is the magneto condition and P-lead attachment.

By the way, the complete factual report docket is available at
https://data.ntsb.gov/Docket?ProjectID=100356
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rwahlgren



Joined: 15 Aug 2003
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PostPosted: Sun Jan 31, 2021 14:31    Post subject: Reply with quote

Only piston I could barley see was the one in the cylinder, thanks for the links.
The power plant report is great, though the picture quality should be much better. How to find more of these types of reports?

Photo number 80, Engine #3 cylinder #4 ? Detonation? I guess if the engine was running when the prop suddenly hit obstructions then maybe there could have been for a few seconds or so. Continuous running with detonation usually leaves pits, and would clean the combustion space better. What would be the reason for only 1 or 2 cylinders only to be involved? There is a lot of carbon and lead Bromide or what ever on the pistons. Look at photo 64 corrosion on the upper skirt area.
Photo 112 shows rusty top ring, and piston similar to #4. Photo 113 in the cylinder shows rusting. So all white colors could be corrosion, photos only say so much. Photo 114 rust again and corroded push rod tube.
Finally on page 67 they mention corrosion. Photo 119 and how come they don't say detonation with this clean top piston that is similar to the other?
Page 86 and no mention of the missing propeller shaft? How did they rotate it? Photo 157 No mention of detonation here similar to photo 80.
What happened here? Photo 169 shows white on piston top and 170 its gone? Strange inconsistency.
The comments for photo 172, yellow paint on face of the valve? How do they see the face with it installed? Nomenclature problems?
Detonation and yellow exhaust valve face paint has me wondering.
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rwahlgren



Joined: 15 Aug 2003
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PostPosted: Mon Feb 01, 2021 18:11    Post subject: Reply with quote

Is this report the final report on the engines? How come only the 2? Since the plane was barely flying you would think an inspection on all the engines would be in order.
I was under the impression that an investigation for a plane crash engine would be a bit more thorough. There is no mention of checking E gap, nor magneto to crankshaft timing especially when they mention possible detonation. There are more accurate ways to check the point gap, that removes the human element of feel, that I think should have been used, and was the shaft checked for play? There is no mention about the propshaft condition on one of the engines that looks over heated in the photo.
It is obvious that good maintenance was very lacking with some of the findings in this report. The picture quality is horrible.
I expected it to be a bit more professional considering the source.
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kmccutcheon



Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA

PostPosted: Tue Feb 02, 2021 10:45    Post subject: Reply with quote

rwahlgren wrote:
The power plant report is great, though the picture quality should be much better.

I had no problem with the image quality. They have sufficient resolution to view at essentially full size. Lighting could have been better in some.
Quote:
How to find more of these types of reports?

Try https://data.ntsb.gov/Docket/Forms/searchdocket
Mode = Aviation; you must supply a state or region and a date range
The main NTSB website is https://www.ntsb.gov/Pages/default.aspx
Quote:
Photo number 80, Engine #3 cylinder #4 ? Detonation? I guess if the engine was running when the prop suddenly hit obstructions then maybe there could have been for a few seconds or so. Continuous running with detonation usually leaves pits, and would clean the combustion space better.

Yes, detonation. The high-velocity shock waves have scoured the carbon off the piston crown and started to melt it. This occurs only in the area where the detonation wave occurs, which is usually close to the exhaust valve; by the time it reaches the other side of the combustion space it has lost much of its energy. Since the scoured area has not accumulated any new carbon, I’d speculate the detonation was recent. Too bad they did not show the ring pack in that area.
Quote:
What would be the reason for only 1 or 2 cylinders only to be involved?

Intake leak; cooling fin damage or blockage; damaged baffles; loose-fitting exhaust valve stem; excessive oil consumption; higher compression ratio due to articulated rod motion.
Quote:
There is a lot of carbon and lead Bromide or what ever on the pistons. Look at photo 64 corrosion on the upper skirt area.

I think the corrosion visible in this image happened post-mortem; corrosion like that on the skirt would have been wiped away during operation.
Quote:
Photo 112 shows rusty top ring, and piston similar to #4. Photo 113 in the cylinder shows rusting. So all white colors could be corrosion, photos only say so much. Photo 114 rust again and corroded push rod tube.

Again, the ring rusting indicates exposure to water after operation.
Quote:
Finally on page 67 they mention corrosion. Photo 119 and how come they don't say detonation with this clean top piston that is similar to the other?

This cylinder has the worst corrosion. The barrel and piston crown corrosion indicates water setting in the cylinder.
Quote:
Page 86 and no mention of the missing propeller shaft? How did they rotate it?

Probably with the starter dog.
Quote:
Photo 157 No mention of detonation here similar to photo 80. What happened here?

This may have been a lower-time piston that has not accumulated carbon to the same degree. It also may have been subjected to slight detonation and then subsequently corroded in the carbon-free areas.
Quote:
Photo 169 shows white on piston top and 170 its gone? Strange inconsistency.

I think that is a trick of the lighting.
Quote:
The comments for photo 172, yellow paint on face of the valve? How do they see the face with it installed? Nomenclature problems?

They are talking about the combustion surface (sometimes called combustion face) as opposed to the valve face that contacts the valve seat.
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rwahlgren



Joined: 15 Aug 2003
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PostPosted: Tue Feb 02, 2021 17:29    Post subject: Reply with quote

Yes that is why I was pointing out the corrosion and rust, from sitting after being watered down or what ever is used to put out the fire. So when they mention white color on the piston etc we have no real idea what it is in a photo.
I just thought the photos especially some of the close up out of focus ones should have been better since the outfit taking them has almost unlimited dollars to afford a better quality camera, especially for such important tasks as aircraft accident investigations.
All those detonation causes mentioned okay. But they would cause long term detonation problems, with the lack of major pitting and or burned edges the event would have been short term or very intermittent.
It would be nice to see more of these kinds of reports.
And pardon the pun, what has me on the antidetonate is that video where they claimed detonation blew up the cylinder head. Very Happy
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rwahlgren



Joined: 15 Aug 2003
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PostPosted: Thu Feb 04, 2021 17:02    Post subject: Reply with quote

Volume 4, Number 4 Torque Meter magazine.
ATDC by Kevin Cameron

Article is about DETONATION AND PREIGNITION

On the continued page 18
"Light deto leaves the edges of pistons looking slightly sand-blasted. Heavier deto splashes off aluminum which can sometimes be seen as something like gray cigarette ash specks on the spark plug insulator."

Just thought this was on topic for this discussion.
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rwahlgren



Joined: 15 Aug 2003
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PostPosted: Fri Feb 05, 2021 15:46    Post subject: Reply with quote

In doing some study on detonation, I found information that crevice space could be ripe for helping detonation. Since in the crevice space possible stagnate air fuel mixture could be available and not readily ignited from normal ignition flame. Crevice space would be the area around especially the top compression ring. And this maybe why that area and piston edges are so susceptible to the attack from detonation.
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