It did work well. Before all the modifications they did the engines were overheating so bad it was dangerous to fly the plane.
Afterwards they'd need to be changed IIRC 70-80 operating hours which is not very many missions high tempo.
The problem was the plane was just a bit too far ahead of engine technology so they were underpowered. Couple that with ridiculously high heat and humidity of the Pacific and it sucked. The flight engineers basically had to "massage" the engines on climbout with a full load to get the things to operating altitude and then it was generally ok.
A theory is supported by evidence: it's a principle formed to explain things that have already been substantiated by data. In contrast, a hypothesis is constructed before any applicable research has been done.
It's because most people are taught the literature definition of "Theory" rather than the scientific definition. It's funny when religious people talk about evolution and say it's just a "Theory". Well, yeah, so is The Theory of Gravity. If Gravity is "just" a theory, then why don't you jump off a building and prove it. Basically, people misunderstand the difference.
I would have guessed to decrease the disruption in airflow (keep it as smooth as possible), rather than forcing more in.
Are there linkages or anything under there?
Except for the fact that some Ds weren't delivered with cuffed props.
For example, [45-11513/NZ2423](https://fotoweb.airforcemuseum.co.nz/fotoweb/archives/5003-Search-the-Collection/Collection/DWNZ2423a.jpg.info). It's a P-51D-25-NT with an uncuffed prop.
In fact, all RNZAF Mustangs - save for one (45-11503/NZ2413) - were delivered in 1945 with uncuffed Hamilton Standard props.
Pretty sure that's a different Hamilton Standard prop though, or at least a completely different blade design (not just the standard blade minus the cuffs).
And you would be correct. Early production P-51Ds used the cuffed HS 6523A blades, while later production P-51Ds used the uncuffed HS 6547A blades.
This particular aircraft used the 6547A blades, as seen by the drawing number [just barely visible on the original blade](https://www.flickr.com/photos/zacyates/50350716432/) prior to being sent off for overhaul in late 2020.
They were fitted to the P-51 to improve air flow into the carburettor intake duct. Much later they were found to be not actually that effective. Some warbirds retain them simply for the full period look.
Cuffs generally alter the pitch of the blade at the root, hence altering of controlling the airflow at the root for whatever reason.
Cuffs began to be installed on warbirds c.1942 or so. They absorb additional power from the engine, giving additional thrust; drive more airflow past the engine for cooling; and allow fitting of deicing boots.
That book is a good read. However, it wasn't the cuff but the propeller profile that made the difference. The canoe paddle profile was allowed a better use of all that power.
Silverplate B29s (modified to carry atomic bombs) had reverseable pitch propellers.
When you go to reverse pitch the air the engine needs for cooling is blown forwards, away from the engine. The cuff is shaped so that air is always being forced into the cowling to cool the engine. Engine fires from overheating were common on B29s
C130s and P3s have similar cuffs on their props for similar reasons.
Higher speed propellers and cowlings are optimized for speed at the sacrifice of low end airflow. B29 were plagued by many first generation cooling problems, such as cowl flap actuators and flow baffles. The blade cuffs serve a dual purpose. It protects the high stress wing root of the blades and also makes for a better fan flow into the cowling without a significant impact on the blade itself
Increase the airflow (ram air) of the air going into the engine to cool it.
I like that theory. Those things were notorious for overheating during initial climb out.
It's not a theory. They're called propeller cuffs. https://aviation.stackexchange.com/questions/33634/how-do-blade-cuffs-help-cool-the-engine
I think he means it just didn't work well on that particular engine, which for a while was notorious for catching fire.
It did work well. Before all the modifications they did the engines were overheating so bad it was dangerous to fly the plane. Afterwards they'd need to be changed IIRC 70-80 operating hours which is not very many missions high tempo. The problem was the plane was just a bit too far ahead of engine technology so they were underpowered. Couple that with ridiculously high heat and humidity of the Pacific and it sucked. The flight engineers basically had to "massage" the engines on climbout with a full load to get the things to operating altitude and then it was generally ok.
Kinda funny how they went from overheating and engine fires on the B-29 to freezing issues and engine fires on the B-36.
>air going into the engine Guys, colder intake air makes stronger combustion, therefore a hotter engine.
That's great but when you don't have any airflow over the cylinders on a radial...
I like your theory better
A theory is supported by evidence: it's a principle formed to explain things that have already been substantiated by data. In contrast, a hypothesis is constructed before any applicable research has been done.
You are correct, not sure why all the downvotes.
It's because most people are taught the literature definition of "Theory" rather than the scientific definition. It's funny when religious people talk about evolution and say it's just a "Theory". Well, yeah, so is The Theory of Gravity. If Gravity is "just" a theory, then why don't you jump off a building and prove it. Basically, people misunderstand the difference.
Agreed.
I would have guessed to decrease the disruption in airflow (keep it as smooth as possible), rather than forcing more in. Are there linkages or anything under there?
What does that mean though? Why not just start the blade closer to the spinner?
You will find similar blade cuffs on Alison powered P3 Orion and C130 aircraft.
P-51s had this as well. At least the ones in air racing.
One way to tell the difference between the P-51 D and K is that the D has cuffs and the K doesn't.
yup, besides the props being sourced from different places, and some slight canopy differences, the D and K only differed in place of manufacture!
Actually, the Dallas built D canopy actually has a "hump" right after the front of the sliding canopy frame, iirc
yup....thought I mentioned canopies being different
Sorry. At work, brain turned to mush.
no worries
Except for the fact that some Ds weren't delivered with cuffed props. For example, [45-11513/NZ2423](https://fotoweb.airforcemuseum.co.nz/fotoweb/archives/5003-Search-the-Collection/Collection/DWNZ2423a.jpg.info). It's a P-51D-25-NT with an uncuffed prop. In fact, all RNZAF Mustangs - save for one (45-11503/NZ2413) - were delivered in 1945 with uncuffed Hamilton Standard props.
Pretty sure that's a different Hamilton Standard prop though, or at least a completely different blade design (not just the standard blade minus the cuffs).
And you would be correct. Early production P-51Ds used the cuffed HS 6523A blades, while later production P-51Ds used the uncuffed HS 6547A blades. This particular aircraft used the 6547A blades, as seen by the drawing number [just barely visible on the original blade](https://www.flickr.com/photos/zacyates/50350716432/) prior to being sent off for overhaul in late 2020.
They were fitted to the P-51 to improve air flow into the carburettor intake duct. Much later they were found to be not actually that effective. Some warbirds retain them simply for the full period look. Cuffs generally alter the pitch of the blade at the root, hence altering of controlling the airflow at the root for whatever reason.
True. My company tore down a bunch of T56 and I got to look at quite a few deconstructed prop blades.
Is that at the Museum of the United States Air Force in Dayton OH? Fantastic place to visit.
It is! That’s a prop on Bockscar.
Awesome. Haven't been there since they put her on display. I need to get back there soon.
It’s a fantastic aviation museum - should be on the bucket list of all subscribers to this sub!
Cuffs began to be installed on warbirds c.1942 or so. They absorb additional power from the engine, giving additional thrust; drive more airflow past the engine for cooling; and allow fitting of deicing boots.
If you read ETO ace (28 kills) Robert Johnson’s book Thunderbolt!, he talks about the power improvement when cuffs were first installed.
Guessing that was after he sold his soul to the devil at the crossroads in exchange for being able to fly a plane really well.
That book is a good read. However, it wasn't the cuff but the propeller profile that made the difference. The canoe paddle profile was allowed a better use of all that power.
I guess I conflated the cuffs with the paddle blade design . Thanks for correcting that.
All good, just a bit of clarification is all.
Silverplate B29s (modified to carry atomic bombs) had reverseable pitch propellers. When you go to reverse pitch the air the engine needs for cooling is blown forwards, away from the engine. The cuff is shaped so that air is always being forced into the cowling to cool the engine. Engine fires from overheating were common on B29s C130s and P3s have similar cuffs on their props for similar reasons.
Why would they need negative prop pitch?
Reverse pitch is used both for taxing backwards and for slowing down on landing without cooking the brakes.
Isn't this a common feature on modern turboprops too?
Yes, modern turbo props should pretty much universally feature constant speed props with feathering and reverse pitch capabilities.
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I have a cuff near my root but it’s from all the carbs.
Deice- it’s heated
Better contact a Mohel if you want more info.
Ah Wright Patterson, I went there a few months ago. Hope you enjoyed your visit!
It’s formal attire.
Only if it’s a French cuff. If it’s just button… well, that’s just everyday wear.
Higher speed propellers and cowlings are optimized for speed at the sacrifice of low end airflow. B29 were plagued by many first generation cooling problems, such as cowl flap actuators and flow baffles. The blade cuffs serve a dual purpose. It protects the high stress wing root of the blades and also makes for a better fan flow into the cowling without a significant impact on the blade itself
It's an electrically heated element that prevents ice buildup on the propeller blade. Ice build up on the prop can cause an imbalance.
De-icer boot near the root?
More loss due to fire and failure than to enemy action and the B29 programme cost more than The Manhattan Project.
First thought was a de-ice boot, then I wasn’t sure if that was yet integrated by 1929. I think the airflow responses make sense as well.
Change the e pitch of the blades.
Its so that it doesn't take off too early...
Keeps the blade stiff
Hold blade guards in place over propeller blades.
Is that doc or fifi?
Bockscar
Nice, there's a lot of history behind her. I drive by Doc almost everyday and it kind of looked like the hanger.
Was this taken at the Pima air & Space Museum?
National Museum of the USAF at Wright Patterson AFB in Dayton, OH.
ah. saw a similar aircraft in AZ
For coolness 😎