Mustang canopies.

[packardpursuit]

Not knowing if this subject belongs here, but since it seems the place where Mustang technicalities have been discussed, I'll give it a go.

What was reasoning behind switch to full vision canopy (P-51B/c to D)? Was it simply a question of visiblity?

Not interested in a p##sing contest. So let's exchange considerate and intelligent ideas only, shall we? Perhaps we can all (myself definitely included) learn something.

 

[drgondog]

Pure visibility. The increased slope/slant of the forward windscreen also reduced the drag slightly - but that mod could have been applied to the B/C had drag been a factor.

 

[packardpursuit]

Thanks for your reply.

Pure visiblity is the usual answer, but there were other factos not so obvious. Namely economic, either in direct savings of cost of materials and labor, but also increased speed of production.

Interesting about how D windsceen aerodynamics gets attention on this forum. I'm not disputing it, just noting the concept seems part of the forum's personality. I have few pet concepts of my own.

It has been reported that only 400 P-51B's were to be produced before a new windscreen was to be incorporated. I've often wondered if the D windscreen was what was originally intended?

Some accounts would have u believe the visiblity problem was "solved" withthe advent of the new hood. however I thinkit important to note thefirst production type, as seen on P-51D-5-NA's, was not a complete success, This hood (most asthectically appealing, IMHO) was rather narrow at both sides of pilot's head. Once in England,pilots soon found replacemnt types of the free blown form provided more room for head turning.

Also many stories purport the Malcom hood was only an interim solution to the "visability problem", yet it's pretty clear that interms of pilot visability the Malcom hood represented a much better view than later types. The D hoods that emerged are actually compromises of vision requirements, factored against economic requirements.

 

[drgondog]

Thanks for your reply.

Pure visiblity is the usual answer, but there were other factos not so obvious. Namely economic, either in direct savings of cost of materials and labor, but also increased speed of production.

Interesting about how D windsceen aerodynamics gets attention on this forum. I'm not disputing it, just noting the concept seems part of the forum's personality. I have few pet concepts of my own.

It has been reported that only 400 P-51B's were to be produced before a new windscreen was to be incorporated. I've often wondered if the D windscreen was what was originally intended?

Some accounts would have u believe the visiblity problem was "solved" withthe advent of the new hood. however I thinkit important to note thefirst production type, as seen on P-51D-5-NA's, was not a complete success, This hood (most asthectically appealing, IMHO) was rather narrow at both sides of pilot's head. Once in England,pilots soon found replacemnt types of the free blown form provided more room for head turning.

Also many stories purport the Malcom hood was only an interim solution to the "visability problem", yet it's pretty clear that interms of pilot visability the Malcom hood represented a much better view than later types. The D hoods that emerged are actually compromises of vision requirements, factored against economic requirements.

Economics could be a factor when comparing a Production P-51D-5 with a Division level service center retrofit of a Malcom Hood. IIRC the 'Hood was an 85 hour installation which seems high but consistent with recollection of crew chiefs that were there.

No, the D was not the original concept.

What you may be thinking of was the fact that the USAAF modified the NAA Contract for the P-51A in late 1942 to stop the P51A line and convert the balance of the 1200 ship production order for the P-51B. The Contract mod of the 1200 ship A line, for the 'B', occurred approximately Aug 1942.

1988 P-51B's and 1750 P-51C's were produced - both ceasing after March 1944 when the first P-51D-5s were coming off the NAA and Dallas lines.

February 1943 was the time for pulling two early P-51B-1NA's (#201 and 202) were pulled and modified re: guns and teardrop canopy - but no wing change on leading edge or subsequent gear/gear door/gear bay changes per the production -5's. While the original D canopy may have been slightly narrower than the Malcolm it apparently wasn't noticed as a defect in visibility particularly since the pilot could in fact lean and turn sufficiently to see straight back which wasn't quite possible with the malcolm hood.

My father flew plain birdcage, Malcolm Hood and all models of D (and later H). said the Malcom was better than the birdcage but not quite as good as the D. Subjective, but straight from the mouth of an ace who flew them all (B/D) in combat. He also used rear view mirrors in all models.

The aero discussions entered the equation back in 2007 during some feisty debates on drag, induced and parasite, as well as many other manueverability/performance discussions. Lednicer had published a very thorough paper of the relative drag characteristics predicted by VSAERO and the stagnation points at the base of the windscreen on the Mk IX was very noticable when compared to the P-51B/D.

 

[packardpursuit]

Yes dgondog, very subjective! LOL

For what it's worth, Glenn Wegman, who has flown and mainmtains a number current P-51's had opportunity to fly Rouche's P-51B with a Malcom facimile. He reported the all around view as being the best he's ever had in any Mustang. certianly a more current subjective assessment.

It seemd to re-inforce my view (admittedly subjective!) that with the pilots head and shoulders fully exposed and above upper longerons, a Malcom hood, which is spherical in all directions, appears to have significantly more room. Not only can the head lean over the side, within the sphere, but whole upper body also. Even on a later D, the shoulders are hedged in by a taller and narrowing canopy base frame, and only the bubble allows head movemnt. A much more constricted arraingemnt, in my opinion.

Had not thought of field conversion to Malcom Hood as part of production hrs. I don't think it is the same thing. Will certainly give it a thinking over.

According to my sources, P-51B production ended in Feb, 44, while P-51C production continued until June of same. Staggered changes to assembly lines saw first D's from Inglewood arrive England, May,44. These fitted with -2 style canopy. Interesting that photos seem to indicate majority of these aircraft had original -2's swapped out with "Dallas" type -6 supplies (spares/replacemnt parts?).The few P-51D-5-NA opperating in the Med don't seem to have carried out this mod.

Again, most histories cite two early P-51B's being converted to test the tear drop canopy. Photos of modified P-51B #43-12102 abound. Yet photos of any such second aircraft are conspicous by their absence. Some accounts also say "102" was the Xp-51D, however this is indispute. My own posing ofthe question to NAA test pilot, Bob Chilton, had him respond that he made th e first flight in it and it was always listed as a P-51B in his logs. To further cloud the developental history, some have attributed the six gun arrangment first being fitted in a P-51C. However and again, photographic evidence is lacking.

 

[drgondog]

Yes dgondog, very subjective! LOL

For what it's worth, Glenn Wegman, who has flown and mainmtains a number current P-51's had opportunity to fly Rouche's P-51B with a Malcom facimile. He reported the all around view as being the best he's ever had in any Mustang. certianly a more current subjective assessment.

I am not near as experienced as Wegman or Rouche but I do have 50+ hours in the TF-51D ( a Cavalier modified P-51D-25) that my father had in the late 50's early sixty's so I 'm not going to debate better view but will offer this observation. I had no problem looking aft - and say, looking left, there was no turtledeck to obscure 7 to 430 with only the vert stab to interfere. I personally have never flown in a malcolm hood version so can't otherwise comment.

It seemd to re-inforce my view (admittedly subjective!) that with the pilots head and shoulders fully exposed and above upper longerons, a Malcom hood, which is spherical in all directions, appears to have significantly more room. Not only can the head lean over the side, within the sphere, but whole upper body also. Even on a later D, the shoulders are hedged in by a taller and narrowing canopy base frame, and only the bubble allows head movemnt. A much more constricted arraingemnt, in my opinion.

Cinched in a harness, there is no difference per se, but a 51 cockit is roomy and permits enough lateral movement to look around. I might concede that the Malcolm Hood has a little better aft/down view due to the points you raise regarding the canopy rail. Pilot upper body length is a factor also. A lot of fighter pilots were runts, relatively speaking (Olds and Feibelcorn and Kinnard being exceptions that come to mind)

Had not thought of field conversion to Malcom Hood as part of production hrs. I don't think it is the same thing. Will certainly give it a thinking over.

It isn't the same as production hour in the sense that it is a post delivery field services 'kit' mod. Candidly I don't have the WBS/CLI detail on the comparison between the windscreen/canopy comparison between the B and D either.

According to my sources, P-51B production ended in Feb, 44, while P-51C production continued until June of same.

You are probably correct on the B and I know the C continued a little longer - I didn't have my fingers on the exact data - hence the vague post March comment for the combined B/C. The first D rolled off in March I believe and the question regarding the last B is one I haven't nailed yet.

Staggered changes to assembly lines saw first D's from Inglewood arrive England, May,44. These fitted with -2 style canopy. Interesting that photos seem to indicate majority of these aircraft had original -2's swapped out with "Dallas" type -6 supplies (spares/replacemnt parts?).The few P-51D-5-NA opperating in the Med don't seem to have carried out this mod.

Again, most histories cite two early P-51B's being converted to test the tear drop canopy. Photos of modified P-51B #43-12102 abound. Yet photos of any such second aircraft are conspicous by their absence. Some accounts also say "102" was the Xp-51D, however this is indispute. My own posing ofthe question to NAA test pilot, Bob Chilton, had him respond that he made th e first flight in it and it was always listed as a P-51B in his logs. To further cloud the developental history, some have attributed the six gun arrangment first being fitted in a P-51C. However and again, photographic evidence is lacking.

Interesting to speculate on the C as the first 6x50 mod.

The P-51C cntract ac-33940 was awarded 10-8-42 while the B award was 8-26-42. The first of the B -1NA series started arriving in England in August 1943 and IIRC the first C-1NT's were post January 1944. That would imply that the first C-1NT tooling was ready perhaps four months after the first production B and the first C rolled off maybe in October, 1943? I have just moved and a lot of my stuff is buried so I am just guessing.

The P-51D contract was awarded on 2-27-43 for two ships 42-106539 and 42-106540, which were right in the middle of the P-51B-10 block. That would further suggest that the two early P-51B-1 test ships were flown before the first P-51C-1NT rolled off the line.Two months later the P-51D-5NA contract was let, probably reflecting acceptance by USAAF of the test results.

The fully modified D-5 was in ETO only two months later than the first C-1NT's. Seems to be a real stretth to pose that an early C instead of the 10th production P-51B-1 would have been the first for the six gun test.

Poses the question why not do a relatively simple design mod on the same ship you're doing the canopy mod on?

Interesting to ponder but I don't have the facts and my long time go to guy, Al White, is no longer with us. Al had nothing to do with the design but as Chief Test pilot at NA when I was growing up he had access to all the records.

BTW - have you had any success getting to NAA data from Boeing? I haven't had much luck.

At any rate the discussion on the Malcolm Hood is interesting but certainly in the realm of the subjective and since I had no first hand experience with it I can only express the opinions.

 

[packardpursuit]

drgondog,
I will bow to your first hand observations in what constitutes a good view from the seat of a D. The only Mustang cockpit I've ever sat in was Mantz' P-51C, while it was at Movieland of the Air, 1971. The sides and top panels were rmoved at the time. I did try to turn to get the view between the seat back and the front of the quarter lights. Not too practical at all, is my recollection.

There is SO MUCH of the Mustang story, in its boxed and accepted versions, that simply doesn't make sense, quite often in a chronilogical issue . We don't have full access to the real behind the scenes happenings re: developemnt and decission making except in snippets and brief revelations by some insider and then trying to reconcile that with what is known, or believed known, or assumed to have happend because extant photos suggest that it did. I suppose it's all the room for research and specuation possible"between the lines " that makes it all so interesting.

I personally don't think Boeing has ever had any real archived NAA historical materials. Too many are asking for it and coming up empty. Of course I would gladly eat crow if it proved otherwise!

 

[drgondog]

I agree your observations but have found Gruenhagen's book to the best of the data presentations, and Mustang Designer on Schmeud's contributions. I was not much of an Atwood admirer (through second hand accounts as I never met the man).

As to Boeing - You may be right, or Boeing is simply consumed by indifference regarding requests. I do have the full blown set of drawings on all models of the P-51 on CD - but not always easy to rifle shoot specific drawings to get what I want. The Detail, to Assy, to Inst'l trees are not always consistent so the Easter Egg hunt often occurs.

Enjoyed the dialogue but I did have a hard time trying not to get into a p#$@%ing contest. Just kidding.

 

[packardpursuit]

I heard the guy that did th e P-51D-5-NA drawing in book about Schmued is an ok dokie guy. I know for a fact, if he had to do them over again, he would have added something in the front view to make it look less anemeic!
Charlie

 

[drgondog]

I heard the guy that did th e P-51D-5-NA drawing in book about Schmued is an ok dokie guy. I know for a fact, if he had to do them over again, he would have added something in the front view to make it look less anemeic!
Charlie

Like what?

 

[packardpursuit]

"He", the draftsman, should have ghosted in the cowl former just infront of the engine. It would have given some definition to a visually bland spot. IIRC, the spinner and prop kind of appear to be hanging in mid air, with the canopy sort of hovering above. I may still have the original art packed away.

Questionable art aside, I believe Wagner's book, Mustang Designer, is a very good effort. IIRC, it is supported by Horkey's effort (Sorry, I forget the title).

Charlie

 

[drgondog]

"He", the draftsman, should have ghosted in the cowl former just infront of the engine. It would have given some definition to a visually bland spot. IIRC, the spinner and prop kind of appear to be hanging in mid air, with the canopy sort of hovering above. I may still have the original art packed away.

Questionable art aside, I believe Wagner's book, Mustang Designer, is a very good effort. IIRC, it is supported by Horkey's effort (Sorry, I forget the title).

Charlie

Charlie - my books are packed away but I believe it was Mustang Designer...

http://www.amazon.com/dp/1560989947/?tag=dcglabs-20

Bill

 

[packardpursuit]

Issue of proposed 400 P-51B 's being built (1st production block) and then switching to a diferent windscreen originally arose for me, with publication of Classic Aircraft No.3 (1973 Cross, Scarborogh,Roberston - Patrick Stephens Ltd.) page25

" Yet another proposal by Norh American in March 1943 was that factories at Inglewood and Dallas, after 400 B models, should turn over to D model, employing a wing moved forward by three inches and improved top cowling fairing lines 'to effect better merging into the pilot's windscreen'. No specific mention was made at this time of the re-designed rear fuselage and 360 degree-vision canopywhich distingquished the eventual D model."

The only error that I can percieve derived from that statement is placement of the wing. It never "moved", wing of Mustang I is in same place as P-51D. The changes of the D's cowling were undertken. It is possible the authors (Cross Roberston) meant larger "Expanded Leading Edge" instead of "moved?
Hence my wondering if indeed D windscreen without familiar canopy and rear decking was envisioned with the "high back" features of Mustang I thru P-51D/K?

It should also be noted a number of proposal were being tendered about B/C/D production and that diverse concept drawings and windtunnell models from this time period (March- Oct.'43) abound. I also realize it's rather easy to wildly speculate what COULD HAVE BEEN, but we are faced with the hard truth that decisions were made and the models we can still observe came to pass.

Was wondering too, if you possibbly got the chance to ask your father if P-51B's and C's were refered to as "razorbacks" during WWII ? I've talked to a few WWII vets and never got an affirmative on that score. Others report differently.

Found my copy of Wagner's book "Mustang Designer- Edgar Schmued and the P-51", see page 125. That is my drawing produced for Crystal Scmhued, 1990. As I look at it now, I would make the changes mentioned earlier, but realized a more glaring anomoly. The chin intake appears off center to viewr's left. It is an opticle illusion, as I remember double checking. It was/ is, the position of the relative prop blades, I believe, making it appear "pulled" to othe pilot's right.

 

[drgondog]

Issue of proposed 400 P-51B 's being built (1st production block) and then switching to a diferent windscreen originally arose for me, with publication of Classic Aircraft No.3 (1973 Cross, Scarborogh,Roberston - Patrick Stephens Ltd.) page25

" Yet another proposal by Norh American in March 1943 was that factories at Inglewood and Dallas, after 400 B models, should turn over to D model, employing a wing moved forward by three inches and improved top cowling fairing lines 'to effect better merging into the pilot's windscreen'. No specific mention was made at this time of the re-designed rear fuselage and 360 degree-vision canopywhich distingquished the eventual D model."

Charlie - I wonder about the source. I agree your comments below and a further illustration of confusion is that actually moving the wing forward should further exacerbate the cg and static margin issues and not help at all re: stability due to heavier and larger Packard/Rolls - which is the primary reason why relative wing/spar location in H stayed the same as the B/D but the aft fuselage length was increased by ~13"


The only error that I can percieve derived from that statement is placement of the wing. It never "moved", wing of Mustang I is in same place as P-51D. The changes of the D's cowling were undertken. It is possible the authors (Cross Roberston) meant larger "Expanded Leading Edge" instead of "moved?

That would be my guess - that the root chord at the centerline was perhaps 3" longer but the main spar position remained the same. What is interesting to me is that the wheel doors were re-designed to 'flow' into the new forward surface area afforded by the root extension - well before reports of structural failures came in from ETO - due to doors opening under High G manuevers - even though wheel uplocks kits were added.

Hence my wondering if indeed D windscreen without familiar canopy and rear decking was envisioned with the "high back" features of Mustang I thru P-51D/K?

Gruenhagen, pg 96, indicates that the 'D' was conceptualized to have a full 360 view from the beginning - and suggests that new manufacturing techniques learned from B-17 nose section development of one piece plastic/acrylic.

It should also be noted a number of proposal were being tendered about B/C/D production and that diverse concept drawings and windtunnell models from this time period (March- Oct.'43) abound. I also realize it's rather easy to wildly speculate what COULD HAVE BEEN, but we are faced with the hard truth that decisions were made and the models we can still observe came to pass.

Was wondering too, if you possibbly got the chance to ask your father if P-51B's and C's were refered to as "razorbacks" during WWII ? I've talked to a few WWII vets and never got an affirmative on that score. Others report differently.

I was around a LOT of fighter pilots growing up as an Air Force brat. I never heard any distinction other than 'bird carge', 'Malcolm Hood' and 'Bubble/Tear Drop' 0r, simply 'B' and D and H model. Never heard 'razorback' attributed to 51A/Bin those discussions.

I suspect that some former Jug pilots who later flew 51B and 51D may have rolled over the terminology for the P-47s they flew before transitioning.

back to 'subjective' and I would not claim that the term was not used for the 'turtledeck' versions.

Found my copy of Wagner's book "Mustang Designer- Edgar Schmued and the P-51", see page 125. That is my drawing produced for Crystal Scmhued, 1990. As I look at it now, I would make the changes mentioned earlier, but realized a more glaring anomoly. The chin intake appears off center to viewr's left. It is an opticle illusion, as I remember double checking. It was/ is, the position of the relative prop blades, I believe, making it appear "pulled" to othe pilot's right.

Interesting Charlie - I will look as soon as I unpack. Seems to me that the only real change forward of engine bulkhead (between B and D) was that the aft part of the cowling line line was slightly improved in combination with the increased (lower) angle of the D windscreen?

IIRC the difference in same region between A and B was an increase (up) of the thrust line, dropping the wing and changing the cowl to include chin intake and 'decreased' second order upper cowling line to enable a packard merlin to be stuffed in?

 

[packardpursuit]

I'm supposed to be working right now, but since I work at home, i'll quickly add the following:

1. Actual chord increase from B/C to D, because of latter's larger Expanded Leading Edge, is 9.3" at c.l.
33.28" ahead of 25% verical datum vs 42.52" for D.

2. Begininng with XP-51F, NAA subscribed to SAE recommended standard of placing Sta. O at extreme
tip of Spinner. So same relative positionof spar may be considered appropriate. However P-51H also had
legthened nose, probably to compensate for that extended rear fuselage.

3. Reasons for larger Expanded Leading Edge of D is directly related to two factors, general wing
strngthening by inclusion of a sub spar ahead of the wheel wells AND simplification of the wheel
doors/aftnose contours. The B/C and ealier have more complex contours all coming togeter in close
proximity.

4. Use apropriate for term "razorback" is subjective and appears to have emerged some time in the early
60's. I cannot find any ref. prior to that. It appears to be popular appelation that probably won't go away
soon. I'm of the opinion that one can actually locate and appreciate the why and how of razorback
feature on an earlier P-47, WWII crews did infact use it in that period towards T-bolts BEFORE the
advent of Bubble canopy types. However, is no such place on a P-51B/C or earlier, for that matter.

5. B/c thrust actually below FRL incorporating down thrust angle, aprrox same vicinity as earlier placemnt. ht of firewall lowered slightly on D to beter fit that new windscreen.

 

[drgondog]

I'm supposed to be working right now, but since I work at home, i'll quickly add the following:

1. Actual chord increase from B/C to D, because of latter's larger Expanded Leading Edge, is 9.3" at c.l.
33.28" ahead of 25% verical datum vs 42.52" for D.

That makes sense. I wonder if the "3" extra mentioned in the article relates to the leading edge 'growth' for the increased strake angle of The D, and new intersection with the outside fuselage contour? The MAC would not have changed at all outside the gear attach region where the strake ends.

2. Begininng with XP-51F, NAA subscribed to SAE recommended standard of placing Sta. O at extreme
tip of Spinner. So same relative positionof spar may be considered appropriate. However P-51H also had
legthened nose, probably to compensate for that extended rear fuselage.

This is probably true but doesn't make sense to me as spinner contours and sections could change but the spinner interface point probably would not.

3. Reasons for larger Expanded Leading Edge of D is directly related to two factors, general wing
strngthening by inclusion of a sub spar ahead of the wheel wells AND simplification of the wheel
doors/aftnose contours. The B/C and ealier have more complex contours all coming togeter in close
proximity.

This makes sense but I suspect the reason was more to beef up the root 'beam' (at leading edge) to take the upgraded bomb/fuel tank shackle capability to 1000+ pounds plus extra .50 and ammo. The ease of manufacturing also makes more sense but stamping tools for contours, once made, don't appear to increase or decrease cost unless the original contour quality was hard to achieve.

4. Use apropriate for term "razorback" is subjective and appears to have emerged some time in the early
60's. I cannot find any ref. prior to that. It appears to be popular appelation that probably won't go away
soon. I'm of the opinion that one can actually locate and appreciate the why and how of razorback
feature on an earlier P-47, WWII crews did infact use it in that period towards T-bolts BEFORE the
advent of Bubble canopy types. However, is no such place on a P-51B/C or earlier, for that matter.

That fits my personal experience and dovetails to my own historical notes.


5. B/c thrust actually below FRL incorporating down thrust angle, aprrox same vicinity as earlier placemnt. ht of firewall lowered slightly on D to beter fit that new windscreen.

Charlie - I read that the thrust line had to be dropped during the Mustang I trials and engine mounts deepened and widened to accomodate the bigger engine. Are you saying the thrust line of the production B actually was lower than the A (relative to main longerons)??

Regards,

Bill

 

[packardpursuit]

It's been a while but I believe MAC is based only on the basic wing area and doesn't (at least on P-51B engineering figures) include the area of Expanded Leading Edge. Since NAA sources give same wing area for D, I'm guessing MAC is same for both. It appears that the wing area of ELE was conveniently ignored for all intents and purposes. I've not seen any weight and blance specs for D, but suspect the B data applies. Would you know for sure?

Re relative spar locations between variants: Spinner for XP-51F appears to be in identical placement as P-51B, as is most of cowling profile and section. I will see soon about comparative spar locations. Cursory judgement is that they are very similar. However, p-51H wing, compared to F, is some 9" farther aft. It seems very clear to me the F is based upon P-51B, where H is strtched and changed in ways quite different than either. I'd always believed the F&H wings were similar in airfoil, but just recieved complete F ordinates and will have to verify if infact same.

I'd wondered about the 3" dimensional difference at the respective ELE and fuselage side interesection, as well. I just calculated the difference at W.Sta.17.5to be slightly in excess of 6" between B and D. So 3" appears to be in error.

Change to simpler lines in the aft cowl/landing gear doors could have also been an aerodynamic consideration. Complexity of B/C shapes in that area could have been seen as a detriment to radiator coolant air induction and in need of a general clean-up.

Can't say about specific constructional differences being harder/more costly to achieve with earlier under fuselage to wing contours, however, it should be noted that overall, P-51B/C production at some 3700 units in less than year and a half, is hardly the production rate achieved in a similar time period withthe D/K's. NAA really ramped up with the later, with some 9,600 units.

 

[drgondog]

It's been a while but I believe MAC is based only on the basic wing area and doesn't (at least on P-51B engineering figures) include the area of Expanded Leading Edge. Since NAA sources give same wing area for D, I'm guessing MAC is same for both. It appears that the wing area of ELE was conveniently ignored for all intents and purposes. I've not seen any weight and blance specs for D, but suspect the B data applies. Would you know for sure?

Simple answer - No.The MAC could only be slightly influenced by the increased chord and area due to the increased root chord.. but only the delta between the B plan form and D for that 'triangle' from the fuselage/wing interface to the WS location where the rest of the wing begins. negligible contribution.

Re relative spar locations between variants: Spinner for XP-51F appears to be in identical placement as P-51B, as is most of cowling profile and section. I will see soon about comparative spar locations. Cursory judgement is that they are very similar. However, p-51H wing, compared to F, is some 9" farther aft. It seems very clear to me the F is based upon P-51B, where H is strtched and changed in ways quite different than either. I'd always believed the F&H wings were similar in airfoil, but just recieved complete F ordinates and will have to verify if infact same.

I'd wondered about the 3" dimensional difference at the respective ELE and fuselage side interesection, as well. I just calculated the difference at W.Sta.17.5to be slightly in excess of 6" between B and D. So 3" appears to be in error.

I had always operated on "7" as the difference - three would not possibly be enough to make the lower cowl fair into the wing based on looking at the experimental Mustan I modification. I think Al Whaite told me seven inches but that was 40 years ago when we had that conversation.

Change to simpler lines in the aft cowl/landing gear doors could have also been an aerodynamic consideration. Complexity of B/C shapes in that area could have been seen as a detriment to radiator coolant air induction and in need of a general clean-up.

I would be inclined to believe the aero effects more important than labor/materials/quality benefits

Can't say about specific constructional differences being harder/more costly to achieve with earlier under fuselage to wing contours, however, it should be noted that overall, P-51B/C production at some 3700 units in less than year and a half, is hardly the production rate achieved in a similar time period withthe D/K's. NAA really ramped up with the later, with some 9,600 units.

Charlie - the B/C (IMO) represents major new tooling, jigs and fixtures for both Inglewood and Dallas - and start up (completely new labor force) and some changes (in fabrication and assy processes) in Dallas, whereas the D/K represents fully trained, fully tooled line at both locations with far less learning curve. At Inglewood, the line went from A to B with the requisite changes in tooling and methods. At Dallas - it was a complete start up from ground zero and several months behind the B.

I doubt very much that the aft lower cowl/wing interface made much difference, although they would not have made the change unless the benefit outweighed the development cost.

 

[packardpursuit]

"I doubt very much that the aft lower cowl/wing interface made much difference, although they would not have made the change unless the benefit outweighed the development cost."

Agreed. What ever changes were made between basic B and D designs HAS to be seen in that light. Almost added comment re: B/C and earlier were just practice for D production.

Note too, almost constant update. Canopy shapes (at least five different idenfiable shapes), two different dorsal fin fillets (and changes to tail structure and anti-boostrudder tab), addition of aditional arms capability,radars, etc. Quite a bit of "improvement " or developement during VERY short (time wise) production runs.

 

[drgondog]

"I doubt very much that the aft lower cowl/wing interface made much difference, although they would not have made the change unless the benefit outweighed the development cost."

Agreed. What ever changes were made between basic B and D designs HAS to be seen in that light. Almost added comment re: B/C and earlier were just practice for D production.

That is so true as very few tooling changes were require to shift over to D/K, ditto line training for labor or manufacturing processes.

Note too, almost constant update. Canopy shapes (at least five different idenfiable shapes), two different dorsal fin fillets (and changes to tail structure and anti-boostrudder tab), addition of aditional arms capability,radars, etc. Quite a bit of "improvement " or developement during VERY short (time wise) production runs.

also the tailplane/horiz stab incidence change, the wheel uplock kits, the change to metal fabric of elevator, retrofit dorsal fins back to B/C, zero launch rocket launchers, different props and prop controls, factory delievered rear view mirrors imbedded in canopy, different radios and antenna, different electrical gun heaters and gunsights - the latter - all internal equipment changes.

I'm sure we must have left some out.