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A funny looking experiment!!! (Read 1962 times)
Oct 29th, 2004 at 11:00pm

Professor Brensec   Offline
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If anyone thinks this is an 'ugly', or at least a strange looking version of the P40, I'll let them get away with it, this time.

Although we all know I believe the P40 to be the best looking plane of it's day (pre and early war years), I'm very glad they didn't opt for thisd particular version - designated XP37.

It apparently had 'centre of gravity' problems when they placed the radiator and supercharger behind the engine, which required th repositioning of the cockpit. Fair enough......reposition it, but don't put it on the tail!!!!!!

...

The Corsair was difficult to land on a carrier because of the length of nose in front ofthe pilot. I wonder how this thing would have gone on a carrier. IMPOSSIBLE!!
« Last Edit: Nov 23rd, 2004 at 2:22am by Professor Brensec »  

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Reply #1 - Oct 29th, 2004 at 11:05pm

Professor Brensec   Offline
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Who said you can't have a 'back seat driver' in a fighter!!  Grin Cheesy Wink

I wonder if the arrow painted on the side is so the pilot knows which end to point down the runway???!!!  Grin Wink
 

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Reply #2 - Oct 29th, 2004 at 11:34pm
Flt.Lt.Andrew   Ex Member

 
Looks like a GeeBee Racer cross breed....

hmmmm....

A.
 
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Reply #3 - Oct 31st, 2004 at 4:38pm

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It looks COOL!!! Shocked Grin
 

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Reply #4 - Oct 31st, 2004 at 4:59pm

Hagar   Offline
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Looks all out of proportion to me. That short moment arm would make it a tad twitchy. Shocked Adding 10 feet or so to the rear fuselage might be an improvement.

Quote:
Looks like a GeeBee Racer cross breed....

My thoughts exactly. Roll Eyes
 

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Reply #5 - Oct 31st, 2004 at 5:27pm

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I like it personally. And I want one. Grin
 

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Reply #6 - Oct 31st, 2004 at 8:22pm
Ben_M_K   Ex Member

 
It kind of looks like a mix beetween a Gee Bee and a P-51. Roll Eyes
 
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Reply #7 - Nov 21st, 2004 at 9:01pm

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Quote:
It kind of looks like a mix beetween a Gee Bee and a P-51. Roll Eyes


Yeah that is definately an interesting looking aircraft!

As for landing it on an aircraft carrier, I'm not gonna do it!!!
 
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Reply #8 - Nov 22nd, 2004 at 3:53am

Professor Brensec   Offline
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Quote:
It kind of looks like a mix beetween a Gee Bee and a P-51. Roll Eyes


Funny you should mention that it looks like a P51!!!

Curtiss (designers and makers of P40) of which this is an experimental variant, were ordered to give the plans of their new fighter to North American, so the new fighter could be 'rushed through' in record time.

Although NortH American claim to have had no more than a 'perfunctory' look at the plans of the completed (and test flown) plane, their P51 ended up looking very 'reminiscent of the new Curtiss fighter based on the P40. (I beleive they had more than just a 'look' at the plans).

Don't get me wrong, I believe the P51 was an innovation and it had features which were original, not the least of which were the laminar flow wings. I, in fact. love the P51B/C.

But many P40 features can be seen on the P51, apart from the overall 'look'. The 'belly mounted' radiator scoop, for instance.
 

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Reply #9 - Nov 22nd, 2004 at 2:00pm

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LOL Prof. We've already had a long discussion on this subject so I'll try not to start all that again. Wink Personally, I can't see any resemblance between the aircraft in your photo & the P-51. Except for the stubby tail end it has the classic look of a Curtiss design.

I still maintain there's only so many places you can fit a radiator scoop on a single-engined fighter. The most common locations were directly below the engine as on the P-40 & Hawker Typhoon, under the wings as on the Spitfire & Bf 109 - and below the mid-fuselage as on the P-51, Hawker Hurricane and many other types. I read an interesting article in Aeroplane Monthly by J. Leland "Lee" Atwood, vice-president of North American Aviation in 1940. It's based on a lecture he gave to the Yorkshire Air Museum on June 13, 1998. Here's what he said about the "laminar flow" wing. Quote:
After the RAF contract was awarded it was decided - at the recommendation of the aerodynamics group - to use the new "laminar flow" aerofoil, which promised further drag reduction. In the event, many tests (including some in recent years) have shown that extensive laminar flow was not developed by the Mustang wing, and that the drag of the wing was probably no less than that of conventional wings of the same thickness & taper ratio. On the other hand the figures .....
... indicate a substantial drag-reduction advantage for the cooling system.


Earlier in the article he states that. Quote:
The theory of this air pump effect (of the radiator scoop) was encapsulated in the work of F. W. Meredith of the Royal Aircraft Establishment at Farnborough, whose report (RAE No 1683) of August 1935 greatly influenced me, as chief engineer of North American Aviation, to offer the British Purchasing Commission the ducted radiator design configuration in 1940. Meredith's report showed how the momentum loss in the cooling radiator could be largely restored when excess cooling air was being forced through the radiator at high speed. .....
.... Since Meredith's work was generally expressed in unfamiliar mathematical terms, it was poorly understood & sometimes even described in terms of mild ridicule.
Quote:
Unfortunately this high-speed phenomenon could not be effectively measured by regular wind-tunnel scale model tests, and no full-size tunnels ran fast enough (200 - 400 mph) to obtain meaninful results; so it was viewed as ephemeral or even imaginary by many people in the engineering practice. Actually it is quite real, and has a close relationship with jet propulsion. It is reported that Willy Messerschmitt made extensive efforts to determine the reason for the low drag of the Mustang, but his wind-tunnel measurements did not disclose the air jet effect, and most probably could not have done so with the equipment available at the time.
« Last Edit: Nov 22nd, 2004 at 3:27pm by Hagar »  

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Reply #10 - Nov 22nd, 2004 at 3:45pm

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LOL Prof. We've already had a long discussion on this subject so I'll try not to start all that again. Wink Personally, I can't see any resemblance between the aircraft in your photo & the P-51.


Agreed...

Rather think it bears a resemblance to the Napier Heston myself (well, not really, but the Heston's worth looking at anyway Wink )...

http://www.jaapteeuwen.com/ww2aircraft/html%20pages/HESTON-NAPIER%20RACER.htm

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Reply #11 - Nov 22nd, 2004 at 4:05pm

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Quote:
Agreed...

Rather think it bears a resemblance to the Napier Heston myself (well, not really, but the Heston's worth looking at anyway Wink )...

Now that's what I call a nice looking aircraft Charlie. Certainly worth looking at. Wink
 

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Reply #12 - Nov 22nd, 2004 at 4:21pm

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Now that's what I call a nice looking aircraft Charlie. Certainly worth looking at. Wink


...Once the undercarriage is retracted Grin...
 
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Reply #13 - Nov 23rd, 2004 at 2:19am

Professor Brensec   Offline
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G'day Hagar. I figured you'd pop up here, after I made the comments. You seem to be able to smell them............lol.  Grin

I wasn't referring to the 'P40' variant pictured at the beginning of this thread, rather the XP46 which was the one that Curtiss gave the plans to NA for.

I recall, as you said, that we have discussed this before. The XP46, which I will picture again below (so the uninitiated can see the resemblance), I maintain is the 'forerunner' and 'inspiration' for the P51A/B. And I don't care what NA says.  Tongue Tongue Tongue................lol  Grin Wink

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Reply #14 - Nov 23rd, 2004 at 4:34am

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Hi Prof. I know I'm wasting my time but I couldn't resist it. Tongue Grin

You should know me well enough to realise that I enjoy playing Devil's Advocate. I don't know the truth & doubt it will ever be uncovered now. Mind you, the article I mentioned is extremely interesting & proves that the information on the "Meredith Effect" was available & documented in 1935 if anyone was prepared to read it. From what I can make out, 2 prototypes of the XP-46 were ordered on September 29, 1939 & the first flight did not take place until September 29, 1941, exactly 2 years later. The Mustang was already in production & being evaluated by the RAF by then. The Napier Heston in Charlie's photo is another example of the ventral positioned radiator scoop which was certainly not unique, not in Europe anyway.

However, from what "Lee" Atwood explains in the article the Heston would not have benefitted from the Meredith Effect. This is caused by the design & shape of the radiator scoop itself. The important thing seems to be that the front part of the scoop is clear of the fuselage as it is on the P-51D & not directly bolted on or faired into the fuselage itself as on the Heston & so many other examples. This is clearly shown on this photo I took of the immaculate P-51D "Jumpin' Jacques" during a fly-in at Abingdon earlier this year.
...
I don't think the all-important gap between the air intake & the fuselage was so marked on the original P-51 & this was developed over a period of time. It would have been mainly a matter of trial & error as the results couldn't be verified in the wind-tunnels available at the time. The full extent of the air scoop's effect on perfomance was not fully appreciated until after WWII was over.

I think any similarities between the P-40 & P-51 might be exaggerated by the fact that US-designed fighters were invariably radial engined so wouldn't require a radiator at all. (The Curtiss P-75 Hawk, direct predecessor of the P-40, was powered by the Pratt & Whitney Twin Wasp.) These are the only ones I can think of that had inline water-cooled engines, both originally having the same engine. The photo in your previous reply only serves to remind me of the basic differences between the two types. Wink

PS. It didn't strike me until recently how similar the air intake on the F-16 is to the Mustang air scoop. This might explain its remarkable performance.
« Last Edit: Nov 23rd, 2004 at 6:22am by Hagar »  

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Reply #15 - Nov 23rd, 2004 at 6:30am

Professor Brensec   Offline
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You're absolutely correct, mate.





........................................you are wasting you're time!!  Grin Cheesy Wink

I understand all this, but still, the fact remains that the NA blokes had the drawings which Curtiss were 'forced' to handover. But NA refuse to confirm the obvious 'temptation' was given into, to look at what the Curtiss people had come up with. Even in the face of their 'famous' 102 day feat (or however many days it was), they still mantain that they simply "tossed" such a valuable asset aside and went about designing their 'unique' fighter.      Ha!!!!!!!!

It means much to me that Curtiss, who were approached first for the 'much needed' high performance, high altitude fighter (shortly to have 'long range' added to the requirement), were unable to entertain the idea of such a project because they were busy stocking ALL the allied Air Forces with the fighter that held the lines for 3 years (bar the Spit), in every theatre of the war.  Cheesy Wink

Seriously, I know what you say is true, but we all have our favourite plane and we defend it, even when the odds are stacked high........like the P40.   Grin Cheesy Wink
 

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Reply #16 - Nov 23rd, 2004 at 6:41am

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LOL Grin You're as bad as Ozzy & his Spitfires, if not worse. Tongue Wink

Whatever the truth of the matter I don't think anyone would disagree with my opinion that the P-51D is a beautiful aeroplane. This gives me the excuse to post a couple more of my photos of a fine example, probably the most immaculate warbird I've ever seen. I don't need much encouragement. Wink

If a designer were to sit down now & design a Merlin-engined fighter it would probably turn out looking something like this.  
...
...
« Last Edit: Nov 23rd, 2004 at 11:10am by Hagar »  

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Reply #17 - Nov 23rd, 2004 at 4:14pm

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LOL Grin You're as bad as Ozzy & his Spitfires, if not worse. Tongue Wink


Getting there... Wink

Quote:
This gives me the excuse to post a couple more of my photos of a fine example, probably the most immaculate warbird I've ever seen. I don't need much encouragement. Wink


If you ever need an excuse Doug, just ask... Grin

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Reply #18 - Nov 24th, 2004 at 12:33am

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Quote:
Hi Prof. I know I'm wasting my time but I couldn't resist it. Tongue Grin .........
.........However, from what "Lee" Atwood explains in the article the Heston would not have benefitted from the Meredith Effect. This is caused by the design & shape of the radiator scoop itself. The important thing seems to be that the front part of the scoop is clear of the fuselage as it is on the P-51D & not directly bolted on or faired into the fuselage itself ............................. The full extent of the air scoop's effect on perfomance was not fully appreciated until after WWII was over.
............PS. It didn't strike me until recently how similar the air intake on the F-16 is to the Mustang air scoop. This might explain its remarkable performance.


This is not unlike the design of the intake on the F-4 Phantom .........if you are not aware, check out this frontal shot of the splitter-plate/engine intake on one.............this gap seems a necessity for performance and somehow must help avoid a boundary layer which may prevent "clean flow" into the intakes ?
 

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Reply #19 - Nov 24th, 2004 at 2:54am

Professor Brensec   Offline
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Certainly lovely photos Hagar.  And a beautiful plane. As far as WWII birds go, I've only ever seen them up close in Museums and the Australina War Memorial (except when I flew in the Spit...... Grin Grin Grin Grin But I was too young to be that thrilled about the plane itself. Just a mixture of scared and exhilarated, is all I recall from my flight in "The Kangaroo Plane").

I do love the P51, although I prefer the B/C version (a bit faster and still looking like your 'classic' - 'framed canopy'/ridge back - WWII fighter). I know these things actually impeded the pilots ability to see, but I just like it. I also think the 'ridge back' arrangement contributed to some more 'longitudinal stability', which I feel may be lacking in your 'bubble canopy' types.

Most Australian pliots I have read accounts by, preferred their B/C's to the D, citing some sort of "lack of stability, especially in a tight turn against torque"

It (the P51) would be my next 'sentimental' choice after the P40, between which there is no comparison, because of the part it played in the RAAF after the P40 was finally discontinued as the 'frontline fighter' (although this was very late in the peice, and many pilots flew the P40 later variants up till the end of the war).

By the way. The ammo in the wing of that P51 is obviously 'empty' and harmless, but are there 'complete' guns in there (maybe with firing mechanisms missing)? Or are there just 'barrel ends' projecting out the front of the wing, with no 'body' inside?  Grin Wink
 

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Reply #20 - Nov 24th, 2004 at 6:12am

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This is not unlike the design of the intake on the F-4 Phantom .........if you are not aware, check out this frontal shot of the splitter-plate/engine intake on one.............this gap seems a necessity for performance and somehow must help avoid a boundary layer which may prevent "clean flow" into the intakes ?

You're probably correct Ken. I've seen these plates many times but assumed they were some sort of deflector. Until now I never associated them with an improvement in performance. Going back to "Lee" Atwood's article. Quote:
... the first Mustang design had a similar entry opening [to the Spitfire Mk IX]. It was later apparent that the thin boundary layer of air flowing along the lower surface of the wing was progressively thickening in front of the duct opening, and that the flow would break away at a point on the upward curve of the duct wall. While the resulting turbulent unsteady airflow apparently did not cause a serious vibration [on the Spitfire], it certainly reduced the efficiency of the radiator & prevented complete closure of the exit opening, which is necessary to develop the jet thrust.

In the case of the Mustang, the duct opening was larger and the flow instability more violent, creating an unacceptable vibration & rumble. Resourceful engineers at NA, working with wind-tunnel models, overcame the problem by lowering the intake a couple of inches to provide a gutter or scupper via which this layer of turbulent air could bypass the intake. This has been common practice for such ducts ever since.

Atwood reckoned, with the benefit of hindsight, that a similar modification to the Spitfire radiator intakes would have increased its speed by more than 20 mph.

Quote:
By the way. The ammo in the wing of that P51 is obviously 'empty' and harmless, but are there 'complete' guns in there (maybe with firing mechanisms missing)? Or are there just 'barrel ends' projecting out the front of the wing, with no 'body' inside?

To be honest I'm not sure Prof. I was so impressed with the darned thing I didn't know where to look next. I never expected to see any warbirds that day, never mind anything like this beauty. Like many others I was most surprised when it turned up at a vintage light aircraft fly-in. Shocked

Going by the accuracy of the superb restoration I imagine it still has the guns fitted although these would have to be permanently deactivated to fly in UK airspace. I think it's now based at North Weald but I'm not sure of its history. It could possibly have been restored in France, in which case the regulations might have been different. I know a French "large-scale" R/C modeller who has a scale Stuka & Fw 190 that can drop real bombs. Shocked These are used mainly for film work.

PS. The "Lee" Atwood article I'm quoting from is in the May 1999 "Mustang Special" edition of Aeroplane (Monthly) magazine.

PPS. Brief history & more pics of Jumpin' Jacques. http://www.mustangsmustangs.net/p-51/survivors/pages/44-72035.shtml
 

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Reply #21 - Nov 24th, 2004 at 11:32am

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Quote:
Certainly lovely photos Hagar.  ...............I know these things actually impeded the pilots ability to see, but I just like it. I also think the 'ridge back' arrangement contributed to some more 'longitudinal stability', which I feel may be lacking in your 'bubble canopy' types.

Most Australian pliots ...............preferred their B/C's to the D, citing some sort of "lack of stability, especially in a tight turn against torque"



I think this is borne out by the additions on some models of the dorsal fin in front of the main vertical stab.....seen here on a few models showing different canopies and cooler intake shapes........also of note is the differing heights and aspect ratios of the vertical fin on the later models, in an attempt to improve this longitudinal stability issue.......

...
 

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Reply #22 - Nov 24th, 2004 at 2:05pm

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Very interesting set of profiles there Ken. It shows the continuous development of the radiator scoop over the different models quite well. The gap between the nose of the scoop & the fuselage is not clear in the drawings unless you're aware of it. I think this is the cause of much of the confusion as to how the principle works. According to "Lee" Atwood, the much-vaunted "laminar flow" wing is a fallacy & had no noticeable effect on performance. I suspect this belief that the wing was responsible was encouraged to prevent Willy Messerschmitt & other Axis aircraft designers discovering the real reason. It was also believed by people who worked on & flew the aircraft & is still referred to today by many veterans & even test pilots. As with other similar examples, what started out as wartime propaganda turned into a legend. I've also heard many well-known & otherwise well-informed air display commentators stating that the distinctive "Mustang moan" (caused by the radiator scoop) is the sound of the airflow over the open gun ports - even when the particular aircraft has no guns & the ports are covered over. Roll Eyes It's quite possible this was another wartime legend.

Quote:
I think this is borne out by the additions on some models of the dorsal fin in front of the main vertical stab

This problem was not unusual when fitting more powerful engines or converting "razorback" fighters to "bubbletops". The later P-47 bubbletops had a similar dorsal fin to the P-51D. It was overcome on the Spitfire by first enlarging the rudder & later the complete vertical tail surfaces on the bubbletop versions.

As this topic started off with the P-40 I got to wondering what happenened to the Curtiss company. This once-famous name does not crop up much after the end of WWII. I found this interesting history of the Curtiss-Wright Corporation. http://www.curtisswright.com/history/Default.asp
 

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Reply #23 - Nov 24th, 2004 at 10:27pm

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Thanks for that set of profiles, Ken. I have seen it a few times in my travels, but to be honest, didn't notice the fin having been added on later D models.

Obviously, the Australian pilots that I mention, were not alone in their having criticisms of the D model in terms of this 'longitudinal stability'. I'm sure, for the manufacturer to make such additions, it would have to have been an obvious and commonly acknowledged problem for them to have engineered a modification.

I'm certainly no 'aerodynamics' expert. In fact, I understand little. But it seems to me that this 'instability' could well have had something to do with the abnormal speed 'bleed-off' in tight turns experienced by the D model (but not the B - another reason I prefer the B).

(Let me see if I can explain my idea without a knowledge of the aerodynamic terms).
It seems to me, if you are directing the plane to turn sharply (while using the elevator pivoting upwards, when the plane is 'banked'), the plane is going to want to tend to go in the original direction, belly first. Without a good degree of 'directional' guidance (for want of the correct term), like that which would be given by the 'razorback' or the added fin, the plane, when it eventually began to move in the direction required, will have spent much of it's speed being 'forced' by inertia belly-first in the original direction.  Roll Eyes ??? Embarrassed Lips Sealed

I can picture it, but I don't know if I've been able to explain it  clearly. But anyway, in my head, it would seem to account for the 'bleed-off' of speed that the D experienced in tight turns. (Like I siad,  in my head, anyway  Grin Grin Wink.

I always found it disappointing that the P51D, being such a wonderful plane, in most ways, could literally 'turn on a sixpence, but after having done so, you look at the ASI and find you've lost 100 knots somewhere in the process.
 

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Reply #24 - Nov 24th, 2004 at 11:13pm

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Actually Bren, the reason that planes bleed off speed in turns is that effectively, in a turn you are going "up hill".....first you roll into the turn and with the reduced wingspan presented to gravity due to the bank and hence increased wing loading (weight/wing area - also due to the bank) you will need to add elevator to fly through the turn with a higher angle of attack on the wing to make up for these deficiencies.....this is the same effect as trying to climb, as opposed to flying straight and level.........once you are banked into the turn and have the elevator input increased, you will add in some rudder to balance the turn and make the tail follow the nose through the turn......in a very steep turn you may need less rudder and more elevator along with added power to overcome the drag of the higher angle of attack required to maintain altitude through the turn......

........more confusion added now ?  8)
 

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Reply #25 - Nov 25th, 2004 at 12:16am

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Quote:
........more confusion added now ?   


This would appear to be the case...... ??? ??? Roll Eyes

Thanks mate.
 

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Reply #26 - Nov 25th, 2004 at 1:15am

Rifleman   Offline
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" Full size A/C are just
overgrown models ! "
Tropical island in the Pacific

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Sorry but it seemed to make sense to me at the time.... Roll Eyes........

..........only trying to be helpful, but sometimes I go on a bit........ Embarrassed
 

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Reply #27 - Nov 25th, 2004 at 4:14am

Hagar   Offline
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My Spitfire Girl
Costa Geriatrica

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I've forgotten more about aerodynamics than I ever knew which wasn't a great deal to start with. Shocked

Ken will know from his experience with R/C models that it's possible to fly an aircraft perfectly well on ailerons & elevator alone with no rudder at all, even doing basic aerobatics. Many popular sport models have a fixed fin with no rudder. On conventional piston-engined aircraft & gliders the rudder is used to help initiate turns but "opposite rudder" is often required to hold the nose up once the turn is established. In a real aircraft this tends to be instinctive & you might not even notice what you're doing with the rudder or what position it's in relative to neutral.

From what I do remember about aerodynamic theory, the problem with the bubble canopies is that modifying an existing design by cutting down the rear fuselage decking to fit them reduces the surface area of the fuselage profile. When the aircraft is banked in a steep turn the fuselage acts as a wing & creates its own lift. The deeper the fuselage, the more surface area & hence more lift available when banked. This also helps to maintain stability in the yaw axis in all normal flight conditions. Reducing the surface area of part of the basic airframe without compensating for it will upset the delicate balance of the original design & make it twitchy & less controllable.

Many WWII fighters had a short tail moment arm* & were by no means perfect in this respect to start with, suffering from instabilty problems throughout their time in service. The canopy itself might also disturb the airflow over the vertical tail surfaces, further reducing stability & control - especially at low airspeeds. Fitting a dorsal fin or using other methods for increasing the area of the fin & rudder will often but not always correct this problem. Fighter aircraft are flown to the limits in combat situations & the usual rules go out of the window. An aircraft with predictable flying characteristics & responsive controls throughout the speed range must be a great bonus to a fighter pilot.

I discovered to my surprise when I had a flight in one many years ago that the rudder is very rarely used in normal flight on jet fighters like the Hunter. It's only required for advanced aerobatic manoeuvres & steering on the ground.

*PS. The XP-37 in Prof's original topic is a perfect example. I suspect it suffered from longitudinal instability in the pitch & yaw axes. Lengthening the rear fuselage by even a couple of feet would improve it considerably, both in looks & performance. Leaving aside all aerodynamic theory, the old adage, "If it looks right, it will fly right" proves true more often than not. Wink
« Last Edit: Nov 25th, 2004 at 10:27am by Hagar »  

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