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Classic Wings Magazine WWII Naval Aviation Research Pacific Luftwaffe Resource Center
When Hollywood Ruled The Skies - Volumes 1 through 4 by Bruce Oriss


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PostPosted: Thu Dec 06, 2018 11:33 am 
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Dave Hadfield wrote:
I flew the Spitfire 60 hours this summer. I could have gone to 11 lbs of boost. I never got beyond 8. Not once.


The Randy Sohn paper talks about using sufficient throttle on takeoff to open the power enrichment valve. Does 8 pounds of boost accomplish that or does it not apply in this case?


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PostPosted: Thu Dec 06, 2018 11:45 am 
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One of the common misconceptions about both the R3350 and R4630 was that they were unreliable. That was true early on of both engines, however once the bugs got worked out and they were put in commercial service (instead of high wear military combat operations) they became extremely reliable. As Pratt and Curtiss got a handle on the (then) advanced metallurgy required to make the engines last, they made upgrades and the engines became workhorses. Once it was understood how to properly maintain them, they became rock solid engines. Once we get into the mid-1950s, both engines gave regular 1500+ hour TBO service in airline service. When the change to 100LL came into effect, power settings were adjusted to make allowances for the lower knocking resistance of the fuel and the engines kept trucking. We saw significant numbers of DC-7s and C-97s operating into the mid-1990s because of those changes. But the R2800 was built in such numbers to support such a wide variety of airframes, that it won out simply due to volume. In fact, you can legally get 4 different models of R2800 from the same core engine, so it's possible to do things like convert a Corsair to the R2800-CB3 without much paperwork, or take a Convair 240/340/440 or Douglas DC-6 from a two-speed supercharged CA-18 to single-speed supercharger equipped CB-16. It's the same core, you just change what's attached to it to get the different versions during the build-up.

Also, Joe T.'s T.20 was the one that crashed a couple years ago with Nelson Ezell in the pilot's seat when the engine siezed. Unless I missed something, that airplane was a total loss and his current Fury, "Eagle's Wings", (which debuted at Reno this year) is a different airframe built up by Sanders.


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PostPosted: Sun Dec 09, 2018 9:58 am 
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bdk wrote:
Dave Hadfield wrote:
I flew the Spitfire 60 hours this summer. I could have gone to 11 lbs of boost. I never got beyond 8. Not once.


The Randy Sohn paper talks about using sufficient throttle on takeoff to open the power enrichment valve. Does 8 pounds of boost accomplish that or does it not apply in this case?


Yes, it's very true -- many engines incorporate a fuel port that is open when at full power. This enrichens the mixture, helps prevent detonation, and cools the cylinders. Fuel flow during this setting is extremely high, but it's only used for takeoff or similar situations.

My wife's RV6 illustrates it very well. In a full-power climb the Lycoming O-320 EGT will indicate a certain value. Then, if you reduce power by 50 rpm, the EGT goes up sharply as the mixture leans out (the port being closed). Easy to see and quite informative.

But my standard takeoff power setting in the Spit was 6 lbs of boost -- roughly 42". That's not even at the max climb setting, so we didn't need the cooling effect of the take-off power port, at all.

Spitfires are getting more daily use right now in England than they have since WWII. That's because the CAA changed the rules, and you can advertise and sell flights in 2-seat Spits even without a Commercial certificate (subject to qualifying conditions); like it's an airline flight. There has been a huge line-up of passengers. Entire seasons are nearly pre-sold. I was speaking to the CEO of one of those outfits, and he confirmed they never go anywhere near full power, and the Merlins are not breaking down.

Dave


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PostPosted: Sun Dec 09, 2018 6:46 pm 
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davem wrote:
The owner of the Martin Mars seems to think they still have 3350's

Oops. My bad...

Corrected.

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There is nothing like the taste of fresh shoe in the mouth... so early in the morning!

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PostPosted: Mon Dec 10, 2018 2:15 am 
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CAPFlyer wrote:
One of the common misconceptions about both the R3350 and R4630 was that they were unreliable. That was true early on of both engines, however once the bugs got worked out and they were put in commercial service (instead of high wear military combat operations) they became extremely reliable. As Pratt and Curtiss got a handle on the (then) advanced metallurgy required to make the engines last, they made upgrades and the engines became workhorses. Once it was understood how to properly maintain them, they became rock solid engines. Once we get into the mid-1950s, both engines gave regular 1500+ hour TBO service in airline service. When the change to 100LL came into effect, power settings were adjusted to make allowances for the lower knocking resistance of the fuel and the engines kept trucking. We saw significant numbers of DC-7s and C-97s operating into the mid-1990s because of those changes. But the R2800 was built in such numbers to support such a wide variety of airframes, that it won out simply due to volume. In fact, you can legally get 4 different models of R2800 from the same core engine, so it's possible to do things like convert a Corsair to the R2800-CB3 without much paperwork, or take a Convair 240/340/440 or Douglas DC-6 from a two-speed supercharged CA-18 to single-speed supercharger equipped CB-16. It's the same core, you just change what's attached to it to get the different versions during the build-up.

Also, Joe T.'s T.20 was the one that crashed a couple years ago with Nelson Ezell in the pilot's seat when the engine siezed. Unless I missed something, that airplane was a total loss and his current Fury, "Eagle's Wings", (which debuted at Reno this year) is a different airframe built up by Sanders.


3350s run in low power applications do tend to last longer. Still there were many Lockheed Connies that landed with 3 engines when they were in commercial use. Still, there have been a lot of 3350 failures in recent years, many in Sea Furies. That was one of the reason's the Sanders converted Argonaut to the R2800. The list of Sea Furies that had 3350s fail is pretty long, yes Nelson Ezell was injured after a 3350 failed, and the previous owner before Joe T was also killed by the same plane. Argonaut, Spirit of Texas, Blind Mans Bluff/Critical Mass, and September Fury have all eaten their 3350s (yes they were race engines on BMB and September Fury. I wouldn't say a 3350 is a good race engine.) There was a run of failed 3350s about 10 years ago that were on non race birds as well. The ones I named off were just off the top of my head, but I'm pretty sure there are more. Personally I'd say a R2800 is a much better engine.

Joe Ts new bird was originally a project started by Chuck Greenhill. It was converted to a two seat, then the R2800 was added. I believe it was an ex Iraqi Sea Fury. (Its in the registry but there aren't any pics of it.) I believe this is it. http://www.sandersaeronautics.com/resto ... roject.asp
that said, it might be partly this one.
http://www.sandersaeronautics.com/resto ... -meier.asp
but Im pretty sure this one went to Meier Motors. There was a lot of talk as to which bird "On Eagles Wings" actually is. (It left me entirely confused)

Will


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PostPosted: Mon Dec 10, 2018 10:51 am 
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Blackbirdfan wrote:
Still there were many Lockheed Connies that landed with 3 engines when they were in commercial use.


An old friend of mine was a Connie pilot for the non-scheduled airlines. He said the main problem with the 3350s was the PRTs blowing out (the turbine wheel would fail) which would result in a really long flame out of the exhaust that frightened the passengers because they thought the engine was on fire. That was normally why he would shut down a 3350.


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PostPosted: Mon Dec 10, 2018 10:53 am 
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Dave Hadfield wrote:
bdk wrote:
Dave Hadfield wrote:
I flew the Spitfire 60 hours this summer. I could have gone to 11 lbs of boost. I never got beyond 8. Not once.


The Randy Sohn paper talks about using sufficient throttle on takeoff to open the power enrichment valve. Does 8 pounds of boost accomplish that or does it not apply in this case?


But my standard takeoff power setting in the Spit was 6 lbs of boost -- roughly 42". That's not even at the max climb setting, so we didn't need the cooling effect of the take-off power port, at all.


Thanks for the explanation Dave.


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PostPosted: Tue Dec 11, 2018 1:45 pm 
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From a friend that had one of the early 3350 conversions. In the early 90's you could get Alameda overhauled 3350-26W in Pressurized Cans for next to nothing. They would re-process the bearings and it would run for ever. The supply dried up, and overhauls got a lot more expensive. 2800's at this point are just plain easier to own/operate/maintain.


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PostPosted: Wed Dec 12, 2018 2:07 am 
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Just my observation. R-3350 TC 18's that I am familiar with, have a few parts that could be trouble some, the PRT's were mentioned already, then there is the fuel injection system that is a bit complicated, as most importantly the more unforgiving rolling element bearings. I don't think there are new replacement main bearings for them, and likely just a limited supply of NOS available. The R-2800 has a good dependability record and not needing expensive to reproduce roller main bearings is a huge plus. I suppose there is a bit of a weight savings using them as well.


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