varsity07840
Airman 1st Class
- 176
- Jun 25, 2013
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
The Lockheed Constellation airliner was designed around the Wright R3350. It must have gotten reliable. It takes years to develop new engines. Like the Napier Sabre, it may have been pushed in to service before it was ready.Much has been written about engine fires on B-29s powered by the Wright R3350. The B-19 and B-32 used the same engine but I've never seen anything written about engine fires on those aircraft. In particular, the B-32 cowl design was quite similar to that on the B-29. Does anyone have an explanation for that? Is it a case of little documentation, or less of an issue with those two aircraft?
Bingo!!!!!The later Wright 3350 engines used fuel injection. Obviously that didn't directly help with cooling but it did give better fuel distribution which may have prevented some cylinders running hot.
My understanding is that there were also problems with the design of the exhaust system which had a separate forward located exhaust collector ring for the front row of cylinders, in front of the engine. That was because the cylinder exhaust ports faced forward. The rear row of cylinders had exhaust ports facing aft. This allowed extremely hot air to be blown directly on the front cylinders. In addition a cracked or damaged manifold would let flames direct hit them. The R-2800 was designed with all exhaust ports facing to the rear with pipes leading to a single collector ring behind the engine. The 3350 exhaust system was later redesigned in a similar fashion.Bingo!!!!!
they found that most of the troubles came from 3 cylinders (?).
Even V-12s with liquid cooling ran hot and cold cylinders due both to differences in cooling and differences in mixture distribution.
The Wright 3350 isn't as well documented as the R-2800 but the post war R-2800s had a lot of changes from even the late war C series engines used in P-47Ms and Ns.
The 3350 may have seen a lot of small changes as well in addition to the fuel injection.
The R3350s that I am familiar with (used on Rare Bear) had steel crankcases.Let's not forget the crankcase was magnesium, not a very pleasant alloy when introduced to high heat or fire.
The original ones were made of magnesiumThe R3350s that I am familiar with (used on Rare Bear) had steel crankcases.
221,000 feet? [I know its a typo]. LOLI don't know about being pushed harder than airline engines.
A Douglas DC-7C made 404 mph top speed, but it cruised at 346 mph at 221,600 feet. That isn't babying the engines at all but, by then, they knew how to operate them and had a flight engineer who was very gentle on throttle changes. Of course, it didn't fly until well into the 1950s. Still, the engines were R-3350s ... later models anyway.
Pratt & Whitney, and Wright, never used magnesium for Large radial production engine crankcases. PW used forged Aluminum, and the 3350's were forged steel. Nose or gear reduction cases and accessory cases were made from Magnesium, and a very bad engineering choice for an aircraft engine. There were some cases of extreme fires while flying in rain storms, since water breaks down and feeds a magnesium fire.Let's not forget the crankcase was magnesium, not a very pleasant alloy when introduced to high heat or fire.