B-17 Grounding Expected

[cvairwerks]

Odd that Boeing would take that attitude after they were so deeply involved with the restoration of that Stratoliner awhile back.

Probably because none of the flying survivors were Boeing built....all came out of Douglas or Vega. Although Boeing owns what's left of Douglas

 

[Thumpalumpacus]

What did they mean by 90 hours? Is that 90 hours of operating at low takeoff weights and lower altitudes? Or 90 hours of operating with a 65,000 lb gross take-off weight and flying for hours at 25,000 feet? And being shot at by flak and/or enemy fighters?

Probably combat life expectancy, I'd guess. They seemed fairly robust otherwise.

 

[SamuelK]

Per EAA on their aircraft, Aluminum Overcast:

B-17 update: We are working closely with the FAA to safely get B-17 aircraft back in the air.
While our B-17 "Aluminum Overcast" has been grounded since the spring of 2021 when damage to a wing fitting was discovered during a routine preflight inspection, other B-17 operators have also grounded their aircraft due to possible wing spar issues.
These issues could lead to the FAA issuing an airworthiness directive for B-17s. Safety is our top priority, and we're committed to finding the best path forward. Stay tuned for updates as we work to get these treasured airplanes flying again!

EAA, Others Wait for Next Step on B-17s | EAA AirVenture News

 

[Buster01]

I rebuilt hundreds of large radial carburetors in the 70s that were updated to post war parts lists. They were carbs for 1820, 1830, 2600, 2800, 3350 and a few 4360s all for fire bombers
and racers. One guy had a dozen P-47 carbs that he wanted converted to DC6B CB16 engines. The man was nuts, to say the least.

The war production builds had brass wear parts as they were not expected to survive long enough to wear out. The mixture plates, which are stainless steel post war, were brass as was the economizer or power boost valve seat. My guess is that lasting for 25 missions would be a miracle for a bomber.

 

[DrumBob]

After the last tragic crash of a B-17 last year, I said it was time to ground all of them. Some of you scoffed at that, but now, maybe it will happen. Let the authorities inspect all of them and determine their airworthiness.

 

[BarnOwlLover]

If you're talking about the in air collision between a P-63 and B-17, that had nothing to do with the B-17s airworthiness. IMO, had a lot more to do with the P-63's heavily framed car-door canopy (shared with the earlier P-39 the P-63 was developed from) and IMO pilot error in the case of the P-63's pilot (for not recognizing/remembering the visibility issues with the canopy).

That said, there's a few reasons why smaller planes like P-51s and Spitfires are common warbirds, and heavy bombers like B-17s, B-24s, Lancasters and B-29s aren't very common. One of which is simply numbers built and that fighters and light/medium bombers are smaller and more easy to house and maintain.

 

[MIflyer]

If you're talking about the in air collision between a P-63 and B-17, that had nothing to do with the B-17s airworthiness.

It mainly had to do with the utter and complete incompetence of the people running the airshow, including especially the "airboss" who was neither qualified for the job nor ever truly executed it.

In that, it was quite similar to the loss of the TBM off of Cocoa Beach.

 

[GregP]

It mainly had to do with the utter and complete incompetence of the people running the airshow, including especially the "airboss" who was neither qualified for the job nor ever truly executed it.

In that, it was quite similar to the loss of the TBM off of Cocoa Beach.

Maybe be careful about saying things like that until the NTSB draws a conclusion ...

I heard there is some new evidence that the P-63 may have turned left to avoid a drone and, in doing so, put the B-17 in his blind spot.

Don't yet know if there is any truth to it or not, but I did see a clip where the P-63 just missed what is purported to be a drone ... could be a thing and could also be a fake video. I would NOT want to be the drone pilot about now, if it is true.

 

[BarnOwlLover]

That's true if the P-6 tried to avoid an errant drone. There's a reason why the FAA tends to get anal retentive about drones flying close to aircraft without approval and going into restricted airspace.

 

[SamuelK]

Maybe be careful about saying things like that until the NTSB draws a conclusion ...

I heard there is some new evidence that the P-63 may have turned left to avoid a drone and, in doing so, put the B-17 in his blind spot.

Don't yet know if there is any truth to it or not, but I did see a clip where the P-63 just missed what is purported to be a drone ... could be a thing and could also be a fake video. I would NOT want to be the drone pilot about now, if it is true.

I was discussing this possible drone factor with a local P-51 owner who attends the National Warbird Conference every year. Not many people apparently knew about it, but it also wasn't the place speculate at. We will find out soon enough I suppose.

 

[cvairwerks]

Looks like the AD on the wing structure has been released. It's going to be a fairly extensive effort to comply with, requiring removal of the inner wing sections to preform the inspections. What AO found and reported is a bit different than reality. I believe we aren't going to see any of the flying B-17's in the air for at least a year or more. I'll bet the B-17 consortium is already working on a solution to the total problem, in anticipation of having to rebuild all the inner wing sections at some point in time.

 

[gumbyk]

Looks like the AD on the wing structure has been released. It's going to be a fairly extensive effort to comply with, requiring removal of the inner wing sections to preform the inspections. What AO found and reported is a bit different than reality. I believe we aren't going to see any of the flying B-17's in the air for at least a year or more. I'll bet the B-17 consortium is already working on a solution to the total problem, in anticipation of having to rebuild all the inner wing sections at some point in time.

The AD only calls for inspecting the bolt holes using either mag particle (wings off) or eddy current testing, which can be done without removal of the wings.
Also, any aircraft that have already been inspected with the last 10 years are already compliant (I'm not sure how many there are).

I'm guessing that depending on the results of the initial inspections, there may be further regular inspections required.

 

[cvairwerks]

First sentence of the inspection requirement states that the wings have to be removed to accomplish the AD.

 

[gumbyk]

First sentence of the inspection requirement states that the wings have to be removed to accomplish the AD.

(g) Inspection
Before further flight: Perform inspections to detect cracking and corrosion by doing the actions specified in either paragraph (g)(1) or (2) of this AD. No action is required by this AD if all wing terminal fittings have been inspected in accordance with paragraph (b)(1) of AD 2001–22–06, Amendment 39–12485 (66 FR 54111, October 26, 2001), and, as of the effective date of this AD, no more than 10 years or 2,500 flight hours have accumulated since that inspection.

(1) Separate all 8 wing terminal-to-spar chord joints (wings off) and perform a magnetic particle inspection of the steel terminal fittings and an eddy current inspection of the 8 inboard holes in the end of the spar chord, in accordance with procedures approved by the Manager, West Certification Branch, FAA.

(2) On the left and right lower forward terminal fitting-to-spar chord joint assemblies, remove the most inboard fastener common to the spar cord and the terminal fitting, and do an eddy current bolt hole inspection on the steel terminal fittings and on the aluminum spar chord in accordance with procedures approved by the Manager, West Certification Branch, FAA.

First sentence is to complete either (g)(1) or (g)(2).

FAA's estimate of costs is 25 hours labour. I don't think anyone would think you could remove wings in that amount of time, even a regulator!

 

[machine shop tom]

Odd that Boeing would take that attitude after they were so deeply involved with the restoration of that Stratoliner awhile back.

Probably have a different legal team since then.

 

[machine shop tom]

I rebuilt hundreds of large radial carburetors in the 70s that were updated to post war parts lists. They were carbs for 1820, 1830, 2600, 2800, 3350 and a few 4360s all for fire bombers
and racers. One guy had a dozen P-47 carbs that he wanted converted to DC6B CB16 engines. The man was nuts, to say the least.

The war production builds had brass wear parts as they were not expected to survive long enough to wear out. The mixture plates, which are stainless steel post war, were brass as was the economizer or power boost valve seat. My guess is that lasting for 25 missions would be a miracle for a bomber.

I have rebuilt HUNDREDS of carburetors over the last 45+ years. Have never even seen an aircraft carburetor.

 

[GrauGeist]

I have rebuilt HUNDREDS of carburetors over the last 45+ years. Have never even seen an aircraft carburetor.

They looked similar to Automobile carbs, being 1bbl or 2bbl and the pressure carbs were a bit bulkier.

As far as the earlier comment goes about brass carb components.

I have yet to see any brass parts fail on a vintage carburetor and I have dealt with all types and from all years: Ball & Ball, Stromberg, Zenith, Rochester, Carter, Motorcraft, Holley and so on.

The only "brass" part that is prone to fail, is the rubber cone on the needle seat, otherwise, the brass float hinge, which is usually pinned with a stainless rod holds up well and the float itself *may* fail if it's out of adjustment and rubs against the bowl over time.

Military aircraft engines were expected to be overhauled after a service marked in hours, some of the auto carbs I have worked on were well over fifty years old and still very serviceable.

 

[gumbyk]

They looked similar to Automobile carbs, being 1bbl or 2bbl and the pressure carbs were a bit bulkier.

As far as the earlier comment goes about brass carb components.

I have yet to see any brass parts fail on a vintage carburetor and I have dealt with all types and from all years: Ball & Ball, Stromberg, Zenith, Rochester, Carter, Motorcraft, Holley and so on.

The only "brass" part that is prone to fail, is the rubber cone on the needle seat, otherwise, the brass float hinge, which is usually pinned with a stainless rod holds up well and the float itself *may* fail if it's out of adjustment and rubs against the bowl over time.

Military aircraft engines were expected to be overhauled after a service marked in hours, some of the auto carbs I have worked on were well over fifty years old and still very serviceable.

Aircraft carbs also have a lot less movement in service. Engine power is largely 'set and forget' in each phase of flight, unlike a car where you are on and off the throttle every time you go around a corner.

 

[cvairwerks]

With two of the last 4 flying are B-17's grounded for spar chord damage, I seriously doubt that either of the other two operators are going to use #2 for compliance.

From what I gather, from those I know in the B-17 world, problems with the chord sections has been building and already grounded quite a few aircraft previously. There are no new or reusable chord pieces out there and as of right now, no known method to fabricate new pieces.

Of the a/c in restoration for flight, I think all but one have the wings off right now.

 

[machine shop tom]

Aircraft carbs also have a lot less movement in service. Engine power is largely 'set and forget' in each phase of flight, unlike a car where you are on and off the throttle every time you go around a corner.

Yep. Most of the wear in a vehicular carburetor is in the throttle shafts and shaft bores and accelerator pump cams and cups. Years ago, I devised a way to use Briggs and Stratton valve guides and tooling to bush Quadrajet (and other 5/16") throttle shaft bores.