NTSB releases preliminary report on deadly B-17 crash

The several posts suggesting the anti-knock rating of 100LL Avgas causing engine malfunction in this crash are not based on available information. N93012 was a Boeing model B17-G manufactured in 1944 with four Wright R-1820-97 1,200-horsepower engines (NTSB Preliminary Report). This engine model corresponds with Boeing’s documentation which specifies “not less than 100 octane gasoline” (Boeing B17-G Field Service Manual, Jan 1945, pp 66 and 453). ExxonMobil states “Aviation Gasoline 100LL has been approved by the major aircraft engine manufacturers for use in aircraft engines originally designed for operation on the following grades: 80/87, 100/130 and the discontinued 91/98.” (ExxonMobil Avgas, June 2018). Shell states “Avgas 100 and/or Avgas 100LL can be used in aircraft spark-ignition piston engines, for which the engine manufacturer has approved this grade of fuel. Although having the same performance in terms of anti-knock ratings, the two grades are distinguishable by tetra-ethyl lead (TEL) content and color...” (Shell Fuels Technical Data Sheet, Oct 2007).

While some other fuel issue could be a factor, the anti-knock rating of 100LL most likely isn’t. Conjecture about “115/145 octane Avgas”, “Using 100LL instead of the fuel these engines were designed to run on”, or “Low Octane could make the Mags look faulty where they were not” are not supported in this incident.

Yes, definitely we should wait for the final NTSB report.

I’m sure the takeoff weight was very low, compared to a maximum weight takeoff in world war 2.
Even with 100LL gas and 2 engines shut down, he should have been able to land safely.
I flew DC3s for many years. 14 engine failures, 3 on takeoff and 1 that wouldn’t feather. I was at max weight, and was able to land safely. Maybe something else going on.

Its doubtful that the fuel octane was the cause of failure, the original engines were set to run on 115/145 but that fuel has not been around for many years and I am sure the engines had been timed to run on 100 LL because that's what you find at the majority of airports where this aircraft had been used to going. The NTSB will get to the bottom of the problem

where's the prelim on the B767 crash

The preliminary report really tells nothing that is not already known about this incident.

Can anyone comment on the flaps being in a retracted position? I would think the flaps would normally be extended to approach flaps. Perhaps without the flaps extended it caused a loss of lift at low speed and resulted in the impact 1000 feet prior to the runway. Of course this is speculation and we need to wait for the final report... But it stood out to me when I read that.

I wonder if they have had time to tear down the engine to see if there is anything obvious in the one that failed!

Why can't we accept the pilot's comment: Rough Mag on #4? All this conjecture is BS

I notice #4 (the suspect engine) had over 800hrs SMOH at the time of the accident, the other three engines were overhauled at annual and were low time. I wonder what the TBO was used on these engines in service. Most military applications I would imagine would carry much lower TBO, possibly even only a few hundred hours. That doesn’t explain the attempted feather and failure on 3 but it may help explain why #4 died.

Direct link to NTSB report https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20191002X11326&AKey=1&RType=HTML&IType=MA straight from the source

I spoke to crew at an event a number of years ago at an event at Republic Airport. I do not remember if the airplane inferred to was a B-17 or a B-29, but I was told that newer versions of the engine or a different one were required to be installed. I am wondering if those engines were the newer ones.

In any multi-engine aircraft, speed is the critical issue. He may have never reached blueline where the airplane will at least maintain altitude. He probably had his 2 left engines at max power and the 2 right engines either totally or partially shut down. He seems to have been in a constant right turn since he started losing engines. Flaps would have helped him hit the ground at a slower speed but he would have hit the ground sooner given his reduced power. He must have flown right over the terminal building. Read (or watch the movie) Fate is the Hunter by Ernest Gann.

I thought the fuel nozzles for Jet/A were changed after Bob Hoover’s crash.

The note on the fuel used is very crucial. Using 100LL instead of the fuel these engines were designed to run on, which is no longer available, basically makes every takeoff a three engine takeoff power wise. The loss of an engine then becomes very critical. It is not known, but if the crew pushed #3 engine up in an attempt to help with the loss of #4, that engine may also have deteriorated from the low octane fuel. It's clear that they struggled around the pattern. As Sparkie mentioned, the engine tear downs will help tell the story.