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A question about BV 138 props!
- Thread starter sharkman
- Start date
phantom II
Master at Arms
I could not find the reason... :idonno
Cheers , Christian B)
Cheers , Christian B)
Were all 3 engines the same?
phantom II
Master at Arms
YUP !
and all that it say is that they changed #2 to four bladed during production and retrofitted older birds .I would like to know the answer myself except that Blum und Woss had a penchant for odd configurations.
Cheers, Christian B)
Well more blades means more airflow right? Maybe they needed more airflow over the tail surfaces during take off?
They were diesels? :huh:
They were diesels? :huh:
Old Dog
Well-known member
Late variants of the PB2Y Coronado were equipped with four bladed props on the inboard engines and three bladed on the outboards. While researching this I found several theories but the most compelling was that the Navy wanted reversible props on the engines to allow the aircraft to back out of jetties and improve water maneuverability and the only available reversible pitch props at the time was Curtis four bladed units.
Probably not the reason for the one on the Bv 138, no doubt lost in time but I'll see if I have anything in my references.
Probably not the reason for the one on the Bv 138, no doubt lost in time but I'll see if I have anything in my references.
Late variants of the PB2Y Coronado were equipped with four bladed props on the inboard engines and three bladed on the outboards. While researching this I found several theories but the most compelling was that the Navy wanted reversible props on the engines to allow the aircraft to back out of jetties and improve water maneuverability and the only available reversible pitch props at the time was Curtis four bladed units.
Probably not the reason for the one on the Bv 138, no doubt lost in time but I'll see if I have anything in my references.
Interesting Gary,I was thinking last night that I don't recall seeing any other multi engine aircraft with different props.
More blades equals less vibration?
I wonder if it had anything to do with wind flow over the central part of the fuselage, as Bob mentioned. I know the design started out as a gull wing bird with two engines but was under powered so they added the third engine.
Old Dog
Well-known member
Well, other theories for the ones on the Coronado were more clearance between the prop and fuselage (since the engines all had the same HP rating the four bladed units were smaller in diameter to match the load of the three bladed units) and since many of the Coronados were used as VIP transports it was also claimed the four bladed units would make for a quieter cabin. Personally I wouldn't think it would make that much difference. The first theory sounds the most logical to me.
phantom II
Master at Arms
I was looking for that picture last night and did not find it
Well, I'll throw out this theory on the four bladed prop and noise. There is probably something to that.
Prop tips approach the speed of sound when running at max RPM . Using a shorter prop might have reduced the noise that this causes as it would have the effect of reducing the speed of travel of the tips.
Another reason for using Diesel engines . 1. Tremendous torque at low RPM's and 2. The birds could be refueled using the same fuel as in the U boats.
Cheers, Christian B)
Old Dog
Well-known member
None of my references shed any light. Looking at photos the outboard props look a lot like the wooden blades used on the Ju 88, maybe the proximity of the middle prop to the crew a metal prop gave them a sense of security that they wouldn't be rained on by splinters if a wood prop failed in flight.
Chris's explanation is probably as good as any but I'm not convinced that back during that time such a costly modification would have been done just for crew comfort, not much of that seen in any of the German designs of the time.
Chris's explanation is probably as good as any but I'm not convinced that back during that time such a costly modification would have been done just for crew comfort, not much of that seen in any of the German designs of the time.
phantom II
Master at Arms
Ok, so much for theories . I think this is the real answer.
Four bladed prop
Three bladed prop
Cheers, B)
Four bladed prop
Three bladed prop
Cheers, B)
Bamn!
phantom II
Master at Arms
Most logical excuse I could find
. They sure did not mention it anywhere I could dig up.Cheers
phantom II
Master at Arms
Heavens no ! I keep thinking those props need improvement though
Maybe someday Cheers
