P-51B dorsal fin

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fastmongrel

1st Sergeant
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May 28, 2009
Lancashire
I had always thought the dorsal fin mod to the the P-51 only came in with the P-51D but I have just come across a photo on google of a flight of RAF Mustang IIIs



Had a look for some more info on this but no luck. Were they changeover aircraft built using a mix of parts or was this a service modification. Any info would be great as I am thinking of building a Malcolm canopy Mustang III and might consider modding the kit.
 
Yep. When the 'D' was introduced, the cut-down rear fuselage caused some lateral stability, so the dorsal fillet was added. It was found that this also improved handling on the 'B' and 'C', and some airframes were modified, initially I believe at BAD1 Burtonwood, UK, for the USAAF.
No doubt Bill might be able to provide more detailed information regarding USAAF aircraft. As far as I have seen, RAF Mustang IIIs were mainly as standard 'B' and 'C', with some later airframes being received with the dorsal fillet. Note that the pic posted is post January 1945, judging by the upper wing roundels. Checking my listings of airframes issued to the RAF, there is no distinction which had the fillet, but if this can be narrowed down to a NA production batch, I have the US Bu Numbers which cross-reference with the RAF serial numbers, which should provide relevant info.
 
I am doing some research on the Mustang III because I have a plan to build a model of every aircraft my late father worked on during his time as an RAF instrument fitter. I am not looking for particular aircraft because I dont (apart from a couple of cases where there are aircraft as a backdrop in photos) have airframe numbers to work from.

I will start the project with the Mustang because it was the first fighter a/c Dad worked on. I havent done any aircraft modelling for nearly 40 years so I thought it best to start with something relativley simple (I might have just shot myself in the foot there) rather than jump straight into a Short Sunderland or Avro Lancaster for example.

Its quite a list of aircraft to keep me happy for a good few years Dad started working on Percival Proctors and ended up working on Vickers Valiant Nuclear bombers 20 years later.
 
The dorsal fin was never developed as a result of stability lost when the bubble conopy was fitted, as popularly believed.

In reality, whenever power is increased without any redesign, stability is lost. The switch from the Allison V-1710 to the Merlin V-1650 increased the power due to the Merlin's superior supercharger design (thanks Dr. Stanley Hooker), and stabiility was lost from the P-51B model forward. When they fitted the bubble canopy from the Hawker Typhoon to the Mustang, the aircraft STILL had the stability issue the P-51B had. The dorsal fin extension was developed to counter this because it did not interfere with production and could be retrofitted. Yers, they COULD have enlarged the vertical fin ... but that would entail a production stoppage that was not considered worth the delay.

Many dorsal fin extensions were retrofitted, but an entire shipoad of dorsal fin extensions were lost to a U-boat sinking and the dorsal fins were fitted much more slowly than anticipated. Some were simply fabricated locally from Aluminum.

You can see the British answer to fitting more power to the Spitfire as the aircraft was developed. Check out the fin on any Griffon-powered Spitfire compared with, say, a Mk V. You will note the fin area was greatly increased. It was the same problem as the Mustang dorsal fin extension.
 
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Airframes. You might not think so, but North American did.

The canopy was diveloped by the British for the late-model Typhoons and Spitfires. The concept was copied by North American. In fact, the first Mustangs with the bubble camopies use Typhoon canopies that North American had modified as far as the canopy frame and mounting go, but were otherwise stock late-model Typhoon canopies.

Since I live in Southern California, we get a LOT of former North American Aviation employees (as well as other aviation manufacturers, including Northrop, Douglas, etc.) at the museum. Many worked on Mustangs. We even get visitors who helped design the various aircraft. Pete Law of the Lockheed Skunk Works is a frequent visitor. Anyway, more than 20 visitors who used to work at North American confirmed this fact and I, for one, believe them, especially when they show up with original documentation in tow.

Obviously the P-51H and TF-51 have canopies that are different, but the "D" model canopy was pure Hawker Typhoon late-model.

View attachment 185303
 

Great pic Greg. Thanks for posting it. The Typhoon was a bruiser of a plane
John
 
The P-51 British idea, British money, British engine, British canopy and British drop tanks what a great American plane.

Got my tin hat on and waiting for the incoming
 
fastmongrel said:
The P-51 British idea, British money, British engine, British canopy and British drop tanks what a great American plane.
Click to expand...

You have forgotten about mentioning the Polish idea of long range flights and the first reconnaissance flight by Lt. Janusz Lewkowicz, on 27th September 1942 from England to Stavanger , Norway and back flying Mustang Mk I.
 
Whilst I agree that the design concept of the P51 'bubble' canopy is similar to that of the Typhoon, the shape and size are different, as was that of the MkXVI 'low-back' Spitfire (and other late Marks) compared to the Typhoon.
I don't dispute that the P51D canopy is 'Typhoon type', but it's not a true Typhoon canopy.
 
The shape and size are the same, at least on the early examples. Maybe different later, but I don't think so. The lines are exactly the same on our two P-51D's and they are both late models.
 
fastmongrel said:
The P-51 British idea, British money, British engine, British canopy and British drop tanks what a great American plane.

Got my tin hat on and waiting for the incoming
Click to expand...

Okay, I'll bite for fun.
a. British idea. I believe the Brits just wanted P-40s. It was NA engineers that said they could provide a better plane. The Brits only said okay.
b. British money, British engine, British canopy and British drop tanks. It not the ingredients that make the cake good, it the mixing. The Brits had the money, the engine, the canopy and the drop tanks, but, they could make no Mustang!
 
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