Warbird Information Exchange

For sure, I inspect, clean and replace spark plugs at least 3 times a year for my truck, tough to believe they'd be so lax with a 70 year old bomber - And no doubt at all, fouled, out of tolerance gaps would produce a perhaps drastic drop in power for any engine, right down to complete failure. I'm even guessing some of their spark plugs are easier to access than some of mine, really no excuse. Still, it could of and probably should have made it on 2 good engines, so I suspect the focus is now on that aspect. With a surviving crew member, untrained rookie though he may have been, they should be able to get some insight on that.

BTW there is a dedicated thread on this recent FAA report with alot more info [and speculation of course], didn't see it before I posted here.

Why would you change plugs on a truck 3 times a year?

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" I am a nobody in aviation, but somebody to my family."

What affect do electrode gaps have on the likelihood of detonation?

#3 was found to be partially feathered. They may have poured to coals to it to try and get any thrust they could. Might that be the source of the detonation?[/quote]

Well, it is a balance between the gap, the points dwell time, wire, and the available charge from the magneto. All four of these were reported to be out of tolerance by the FAA. Four!!! All four are crucial to a smooth running motor and that doesn't even take into account the ignition advance timing that probably was way out of wack that contributed to the detonation. I am assuming the ignition timing was as out of tolerance as the rest of the ignition system. Also, this motor was proven by the FAA to be only running on one Mag. The other Magneto was almost useless as it's cam was worn out. No one bothered to check this? Cams don't just wear out overnight. The engine also had a mickey mouse ignition wire repair that probably grounded at least the plug it was suppose to fix. All of these adds up to they weren't that serious about engine tune up or at least paying attention to the "big picture" of what was going on with the motor. With a motor so out of perfect running condition like this one there are no "coals" only "coughs". There also seems to be a conflict of interest on who signed off on the engine status which seems to point to no second level supervision.

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Better is the enemy of Good.

Owner/operator can do plugs without needing any certifications. Not sure who on the maintenance team had an A&P or an IA. I'm sure the NTSB report will address all those issues. Wasn't #3 a recent overhaul?

Seems like #4 was problematic and not unanticipated, but what caused them to feather #3? Was it accidentally feathered instead of #4?

Seems like they may have gotten away with multiple maintenance related issues for some time. Accidents usually aren't as a result of a single point failure. A mechanical failure in combination with pilot error when it really counts can spell doom.

I'm confused by the known pre-crash events, and what the FAA have found. We know prior to the flight they were having issues with one of the engines (No.4?) and we know from the ATC transmissions they asked for permission to rtb to 'blow out the engine', but that would imply that the issues found with the ignition etc of both No.3 & 4 engines were not known about and/or found by the crew when they were clearly having engine running issues......and 'blowing the engine through' was not going to be a cure.
To me that raises even more questions.....?

If you're talking about the safety wire half-assery that chaffed through the P lead: that grounded the entire mag..

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Those who possess real knowledge are rare.

Those who can set that knowledge into motion in the physical world are rarer still.

The few who possess real knowledge and can set it into motion of their own hands are the rarest of all.

What about a Mag check? Isn't that a standard preflight check? I don't hold any certifications related to B-17s but I would figure that a magneto switch and check prior to take off would be customary operating procedure. It should have shed the light on the bad Mag that had its cam flat. It does raise more questions. Also, you need to read the cap on the magneto during inspection. Sometimes carbon trails can exist giving signs of cross ignition. That is another possible predetonation problem. If the FAA saw signs of predetonation it was most likely from looking at the piston tops or valves. They will look like they got hit with a hammer sometimes.

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Better is the enemy of Good.

The FAA didn't. The investigation is being carried out by the NTSB. The FAA is basing their letter on findings from that investigation that have presumably been communicated to them by the NTSB as a safely concern.

The NTSB is investigating to determine the cause of an accident that resulted in death or serious injury, and further determine if there was an underlying inherent 'engineering' issue.

The FAA investigation is to determine regulatory compliance, or lack thereof that may have contributed to the accident.

Those investigations run concurrently, with the actual labor and expertise being provided by a commercial contractor with greater experience with the systems in question. NTSB and FAA representatives will supervise the inspections. In my experience, there is also often pizza.

The FAA portion of the investigation has yielded enough evidence to be used in the regulatory sphere to rescind Collings' authorization for these flights. To the purpose of the FAA's investigation, the preliminary findings are enough. The NTSB's investigation will be more exhaustive and their findings more detailed with a report released later.

As an analogy, the FAA will say the stop light was RED when you went through it, the NTBS report will say that the traffic light was emitting light on wavelengths determined to be within the parameters of "RED"

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

I think the report said the mag with the knackered cam was only firing half the plugs on that mag. It may be that there was also something else going on if it was firing half the plugs just fine... Possibly a duff bushing or bearing that allowed the cam to wobble about as it rotated.

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Those who possess real knowledge are rare.

Those who can set that knowledge into motion in the physical world are rarer still.

The few who possess real knowledge and can set it into motion of their own hands are the rarest of all.

I wonder who they consider and expert on B-17 systems ?

The highest time B-17 pilot in the country, is the one involved in this incident

Probably one of the other half-dozen plus B-17 operators, and/or the half-dozen plus overhaul shops familiar with the R-1820, combined with the readily available documentation and manuals.
Under normal circumstances, the subjects of the investigation would not be involved in any way anyway.

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

The engines apparently went to Mike Nixon for inspection etc.

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Those who possess real knowledge are rare.

Those who can set that knowledge into motion in the physical world are rarer still.

The few who possess real knowledge and can set it into motion of their own hands are the rarest of all.

" the NTBS report will say that the traffic light was emitting light on wavelengths determined to be within the parameters of "RED"." Can't tell if "NTBS" was on purpose or not from the context (not that it matters). Being a pretty serious thread, I wasn't sure if this was meant to put smiles faces. Not nitpicking.

So Randy Sohn just passed away, but his notes on radial Magneto checks are very interesting.
Shows just how complicated it is and how easy it is to make a mistake. http://www.douglasdc3.com/sohn/14.htm

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Better is the enemy of Good.