P-51B dorsal fin

[drgondog]

Mike - The dorsal fin was an add on - post July 1944. The dorsal fin was first believed to be a solution to stability issues that continued with the introduction of the P-51D-5 (no dorsal) along with the 85 gallon fuse tank in the P-51B/C/D.

When the P-51D-10 came out with production dorsal fin, NAA started sending field mod kits for all the Mustangs, including the B/C's. The primary field mods post July were dorsal fins for pre P-51D-10, and metal covered elevators for all P-51s to replace fabric covered.

 

[MikeGazdik]

Roush must have added the fin to his Old Crow -B later. I used to have photos when it was first displayed, and I don't recall it being present. Neat info all!

 

[drgondog]

I have failed for some reason to look at this thread for awhile.
Some points:
1. The shape and installation of the XP-51D (43-12102 was P-51B-1-NA number 10) canopy was NOT a Typhoon canopy. However the P-47 that had been fitted with the Typhoon canopy was brought by Bradley to NAA engineers to have a look. Bradley also responsible earlier for telling NAA to put a "100 Gallon" fuselage tank aft of seat - which resulted in the final 85 gallon design. As Terry has pointed out the obvious, the P51D and K and H canopies are all 2 feet or more longer.. with a distinctly elongated look when contrast to the Typhoon.

2. The P-51 Malcolm Hood, first installed in Mustang I AG 618 was an NAA Design/Malcolm manufactured canopy.

From RAF AFDU/3/20/33 Dated 7 December, 1942

"In accordance with instructions from Air Ministry (DAT) reference CS/11800, trials have been carried out on a Mustang IA aircraft, AG618 (sic: AG618 is actually a Mustang I - MV) fitted with a sliding hood. This hood has been designed by North American representatives in this Country and fitted to the aircraft by RAF Henlow, and is merely an interim measure in order to ascertain the tactical advantages of having a sliding hood on Mustang aircraft..."
'2. The aircraft has been flown at Duxford for 5 hours and the following comments are forwarded:
'Advantages
'(i) The view for take-off and landing is considerably improved with the hood in the open position. Previously pilots have felt a trifle cramped when landing the Mustang fitted with the standard hood as the long nose restricts forward view and the view to the side panels is poor when compared to most British fighters.
'(ii) The aircraft has been flown at cruising and fast speeds with the hood open and the view for search was found to be greatly improved. Night flying was not actually possible on this aircraft as flame dampening exhausts were not fitted, but it is certain that the improved view would make this aircraft most suitable for night flying.
'(iii) The view forward and sidewards is now completely unrestricted and this gives much confidence to pilots when flying in bad weather.
'(iv) It was found possible to fly with the hood open without using goggles, as apart from a slight eddy at the back of the cockpit, there is no draught.
'(v) With the sliding hood entry and exit from the cockpit is much easier. It was found with the standard hood that it was advisable for a Rigger to make quite certain that the hood was securely locked before taxying out and with the sliding hood tis was now unnecessary.
'(vi) the aircraft fitted with the sliding hood was limited from diving, but maximum level speed runs have been carried out without any problems developing. The hood, although only a lash-up model, showed no signs of blowing away and stayed in the open or shut position at all speeds. It is necessary to use both hands to open or close the hood even at at slow speeds and although at at first this was found a little difficult. it became reasonably easy after practice. The hood has been opened at an indicated speed of 250 mph and closed again at 300 mph, though at these speeds the opening movement was found rather difficult.
'(vii) Level speed runs have been made with this aircraft fitted with the standard hood and with the sliding hood. With the sliding hood there appeared to be a slight increase in speed which is probably due to removal of the aerial mast and rear ventilators. It was also compared with a standard Mustang from an Army Co-operation squadron and again showed a slight superiority in speed."
"Disadvantages
'(i) The radio mast has to be removed from its present position behind the cockpit to allow the hood to open. this will necessitate re-positioning the mast.
'(ii) There is a very slight up-draught through the cockpit when the inboard wheel fairings are open when operating the undercarriage, but this is not considered sufficient to worry about. [The next section concerned criticisms that only affected the 'lash-up hood' and so has been omitted.]
'Conclusions '3 The tactical advantages of being able toopen the hood of the Mustang in the air are very great and pilots have been most enthusiastic about the improved view, particularly during bad weather flying. This should be a great asset whn carrying out "Rhubarb" operations.
'4 The sliding hood will make the Mustang most suitable for night flying due to the view for search and night vision being greatly improved.
'Recommendations
'5 It is strongly recommended that as tactical advantages of having a sliding hood on Mustang aircraft have proved so great, a hood should be carefully designed and fitted to all Mustang aircraft as soon as practicable."


Robert Malcolm, Ltd. was assigned the task of manufacturing the production kits. This firm specialized in blown Plexiglas and made the earlier Spitfire canopy among others. Malcolm refined the NAA design in several ways - notably the hand crank and forward locking system, and began production.

All Malcolm Hood canopies were installed in the UK after arrival. In the case of RAF, the Hood was installed prior to operational acceptance of ALL Mustang III's at RAF Henly, along with new antenna, etc. In the case of 8th and 9th AF the need was too great to hold up each P-51B/C for ~135 manhours to do the installation.

For the 8th AF I believe that RAF/AAF Warton (not RAF/AAF Burtonwood) as it was the primary Depot for B-24s and P-51s and initially they did EVERY mod for the P-51 after assembly at Speke, including the original 85 gallon tank Inst'l in the P-51B-1 and -5-NA and C-1-NT's that were shipped to England. I still have not found source documentation for Hood installations at each fighter group base Service Group as kits became available. I doubt it simply because Warton would be better equipped and personnel trained in the installation rather than varied skills at different bases.

The DFF fin mod was done first by RAF on a Mustang X, AL 963, in July 1942. It achieved measurable but not complete successful stability improvement. I have found no correspondence from RAF Hucknall to NAA detailing the results, nor internal documentation at NAA leading to the test and production design of a DFF nearly two years later. The structure in the rear empennage of the P-51B and D was strengthened by TO to compliment the addition of the DFF kits to P-51B/C and P-51D-5-NA through approximately 44-13980. Somewhere after that, the DFF was installed to the end of -5 and all succeeding D,K models.

I have seen a valid DFF on several 354FG ships including Beerbower's Bonnie B which is dated before mid July and a couple suggesting a much earlier install - but I haven't nailed the actual dates OR the place of Modification as the kits didn't arrive for 8th AF until late July at the earliest.

I must admit surprise that the myth of the 'Tyhoon canopy was installed on the P-51D prototype' continues to linger as the image of 43-12102 is well known and easy for the practiced eye to note the huge difference in shape.. ditto when comparing the Mustang to the P-47D bubble canopy - which IS much closer to the Typhoon canopy.

 

[grampi]

Ah, was that to take photos of German fighters shooting down American bombers?

Lol!

 

[pbehn]

It is a bit strange to me that the malcolm hood or a US version of it wasnt put on he Mustang from the start, since it was designed for the British and the Spitfire was already in service at the time, ditto for the P47 and F4U. Were there drawbacks to the Malcolm hood such as not being optically perfect?

 

[drgondog]

It is a bit strange to me that the malcolm hood or a US version of it wasnt put on he Mustang from the start, since it was designed for the British and the Spitfire was already in service at the time, ditto for the P47 and F4U. Were there drawbacks to the Malcolm hood such as not being optically perfect?

Interestingly, VERY few Malcolm Hoods were retrofitted to Mustang I and IA even after the design and production ensued. I suspect that Malcolm Ltd had its hands full producing the canopy for the Spit and Mustang III and P-51B/C after the design was proven in service...

The DFF was also first installed and tested with favorable results to improve yaw stability in the Mustang X, but somehow NAA didn't get the memo. Having said that the DFF was never THE solution for high speed yaw issues and only solved by the combination of longer fuselage, greater moment arm between a/c of wing to a/c of horizontal Stab plus 15% greater area of the horizontal Stab - of the P-51H over the B/D.

As Greg noted above, the increase in torque of the four blade prop plus the Rolls engine over the Allison was the root cause of the increasing issues as maximum HP grew from 1150 to 2200 from XP-51 to P-51H

 

[fastmongrel]

There is a film on the net showing the manufacture of a bubble hood. I have looked but cant find it again but iirc correctly it was a very sklled and labour intensive process with a high percentage of rejects.

 

[bobbysocks]

i wonder if it distorted depth perception when landing. back in the early 70s i tried a dome style face shield when riding motorcycles. while i loved the view ( and lack of bugs smacking my face ) the curves distorted things more than i liked so when to a flat shield. i could see that kind of hood might make assessing the distance off of the ground could be an issue.

 

[pbehn]

i wonder if it distorted depth perception when landing. back in the early 70s i tried a dome style face shield when riding motorcycles. while i loved the view ( and lack of bugs smacking my face ) the curves distorted things more than i liked so when to a flat shield. i could see that kind of hood might make assessing the distance off of the ground could be an issue.

Reading the appraisal by the US an advantage of the Malcolm hood is it could be slid back for take off and landing. Some Spitfires have an oval panel in the hood sides. I remember reading this was optically perfect but cant remember why it was placed where it was, not all photos show it.

 

[fastmongrel]

Reading the appraisal by the US an advantage of the Malcolm hood is it could be slid back for take off and landing. Some Spitfires have an oval panel in the hood sides. I remember reading this was optically perfect but cant remember why it was placed where it was, not all photos show it.

It was a Knockout panel that the pilot bashed with his elbow if the inside of the cockpit steamed up. It could also be used when trying to open the canopy in an emergency sometimes at high speed the pressure differential could make the cockpit stiff to move. I believe they stopped being fitted when the blown canopy with curved sides came into use on the MkVs.