# Canopy Design



## kool kitty89 (May 2, 2008)

Besides visibility, what advantages and disadvantages do various canopy designs offer, and what effect on performance do they have. How does this apply to different a/c (particularly fighters), compared to their original canopies?

The ones I was most wondering about are:

P-47
P-51
Bf 109
Fw 190


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## Flyboy2 (May 2, 2008)

I think the best type of canopy is the Malcolm hood. The bubble canopy has good visibility, but slightly less pilot protection compared to a "razorback" type. But the razorback had less visibility. The Malcolm hood had a good combination of both.


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## renrich (May 2, 2008)

If you will notice, almost all post WW2 US fighters have bubble canopies whereas most Soviet fighters (after Mig 15,17) had a kind of razorback type design. There must be some drag factor working there. From my tiny experience flying an L39, one is strapped in so tight you can't turn around and look behind very far anyway. I have a friend who was an IP in Huns at the Fighter Weapons School(2000 hours in Huns) whom I asked about that. He said it was difficult to see much of the rear 180 degrees and he knew one hot pilot who in ACM disconnected most of his harness so he could utilise the bubble canopy.


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## kool kitty89 (May 2, 2008)

I think it depends on the circumstances, and the speed operated.

THe argument Bill and soren got into was with the P-51, it turned out a study had shown pressure distribution and the teardrop bubble canopy resulted in less drag than the razorback/turtleback configuration, though the fact that the bubble canopy had a more sloped windscreen threw in a problem as well.

In the case of the P-47 the performance change is much more significant going from 435 down to 426 mph, the changes being the canopy and a gain in 500 lbs gross weight. (fuel capacity the same) The weight alone shouldn't have that much of an effect. (D-22 vs D-23) http://www.wwiiaircraftperformance.org/p-47/p-47-tactical-chart.jpg

However it isn't clear if the figures were also due to addition of wing pylons, but since it lists fuel levels and ranges with 3x drop tanks for all models, this would be implied that wing racks were fitted. (plus racks were standard on the D-22 iirc)

In the Case of the P-47 the initial razorback canopy had less of a slope, but it also didn't have a flat windscreen, rather 2 pannels mounted at a rather sharp angle when viewed from above. Compared to the round slab screen of the bubbletop versions. (malcolm hood versions had the same configuration as the razorback save for the bulged frameless hood.


Of course there's also cases when fairing the canopy into the fusalage isn't the most practical, but a full bubble canopy isn't added either, even though the decking behind the cockpit closely resembles a bubble canopy shape.
Examples:


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## FLYBOYJ (May 2, 2008)

Keep in mind that pilots in the late 1930s the technology to make Plexiglas with complex compound curves wasn't there. In other words bubble canopies. Look how the Zero compensated for that!


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## pbfoot (May 2, 2008)

FLYBOYJ said:


> Keep in mind that pilots in the late 1930s the technology to make Plexiglas with complex compound curves wasn't there. In other words bubble canopies. Look how the Zero compensated for that!


Was aware of the plexiglass issue but never put it all together in ref to the Zero canopy


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## Trebor (May 2, 2008)

well, I like the bubble canopy. more visibilitymakes you feel more free. while the razorback kinda makes you feel confined, and part machine.


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## Glider (May 2, 2008)

I have to admit that it mas my understanding that the Bubble canopy generally cost you a small decrease in spead but the additional visibility was a more than acceptable payback.
It also worth noting that a number of aircraft fitted with the teardrop canopy normally had to have an addition of some sort made to the tail, increasing the size, adding a piece to the base, whatever solution was chosen.


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## kool kitty89 (May 3, 2008)

Yeah, the true bubble canopy would be a difficulty, but frames like the P-38 and P-39 (particularly XP-39) were close, Westlant Whirlwind, and to a lesser extent the Brewster Buffalo. And IMO the Nate/Oscar's canopy was better than the Zero's, smaller, simpler, cleaner and less framing.










But the Miles M.20 seems to be the first example of a full clearview teardrop canopy. 





But before any of those, the Gladiator had something close and with relatively little framing, carried on to the F.5/39 design


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## Trebor (May 3, 2008)

nice pictures, Kitty! I love the Zero! I do like the canopy of the Zero. it's kind of a combination of a bubble canopy and a razorback. and what I mean by that is the cage-like look the Zero canopy has. I like that. and that's one of the reasons why I like the BF-109


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## kool kitty89 (May 3, 2008)

Oh if you want a real bubble canopy razorback shape cross-over how about this:


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## Trebor (May 3, 2008)

ah yes, the Brewster Buffalo. that is a nice looking aircraft, but I prefer it to be in US pacific colors

(correct me if that's the wrong plane, please. )


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## kool kitty89 (May 3, 2008)

Well the Finns Brewsters came before the Buffalo name was given by the British, and either way the Finns never called their B-239's that. They were usually referred to as "brewsters" or sometimes Taivaan helmi ("Sky Pearl") or Pohjoisten taivaiden helmi ("Pearl of the Northern Skies").
(Other nicknames were Pylly-Valtteri ("Butt-Walter"), Amerikanrauta ("American hardware" or "American car") and Lentävä kaljapullo ("flying beer-bottle").)

But yeah it's a Brewster, but the US colors are kind of boring, though the the older symbols (meatball type) look good on it. (and it doen't look right with the spinner removed as was done to alot of F2A-3's)

This one's nice 





And of course, the dazzel camo: The Art of McClelland Barclay in the Naval Art Collection.


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## renrich (May 3, 2008)

The good thing about the Buffalo canopy was that one could have a green house and grow petunias back there.


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## drgondog (May 4, 2008)

kool kitty89 said:


> I think it depends on the circumstances, and the speed operated.
> 
> THe argument Bill and soren got into was with the P-51, it turned out a study had shown pressure distribution and the teardrop bubble canopy resulted in less drag than the razorback/turtleback configuration, though the fact that the bubble canopy had a more sloped windscreen threw in a problem as well.
> 
> ...


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## kool kitty89 (May 4, 2008)

Well, while still frameless canopies, as mentioned earlier there were a number of interceptors like the MiG 21 and Mirage III that had the canopy faired into the fusalage.


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## FLYBOYJ (May 4, 2008)

kool kitty89 said:


> Well, while still frameless canopies, as mentioned earlier there were a number of interceptors like the MiG 21 and Mirage III that had the canopy faired into the fusalage.


 Those fighters were designed at a time where air-to-air combat was thought to be a thing of the past. The MiG-21 was an interceptor designed to bring down bombers. Look at the MiG-21F, the first version - it was a day interceptor and still had a bubble canopy. It was the later Mig-21 models that had the turtle back and a bunch of avionics shoved into them.


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## buzzard (May 4, 2008)

A fair number of jet fighters were designed without bubble-type canopies. The F4D Skyray, F-8, F-5, F-102, F-106, Tu-128, MiG-23, MiG-25, Mirage III, Draken and Viggen come to mind. Some of these were designed as pure intercepters, but the F-8 certainly wasn't...

Aircraft designers know that performance numbers impress the people who ultimately pay for the planes (politicians) more than less quantifiable qualities such as a pilot's ability to maintain situational awareness. And as Flyboy J mentions, trendy theories and doctrine also play a big role in the design of combat aircraft. Who needs to see what's behind you if automated BVR missile engagements are the way of the future?

Pre-WWII air doctrine was dominated by the bomber prophets, and WWI type dogfighting was largely seen as passe. With fighter designers concentrating on sheer performance, (with bomber interception as the primary role) they regarded streamlining as more important than rearward vision. Until the dogfights began...

The slight protection offered by the fuselage behind the pilot may have been of some use when rifle-calibre armament was the norm, but against .50 cal and cannon fire, most pilots would probably prefer to see the enemy coming, rather than be announced by shells rattling thru the 'razorback'. The Malcom hood is no substitute for a true bubble canopy. Even the post-war Spits had them. And since even fighters spend most of their time at cruise speed, being able to see a 'slower' enemy diving in on your six is worth a few MPH.

I've always wondered how many '109 pilots died because of that crappy canopy. If they could make something like the Me 262, you'd think that, at the very least, the Galland hood could have been introduced by '42.


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## Graeme (May 4, 2008)

The prone position and their associated canopies must have made it *very* difficult to look 'behind'.


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## Trebor (May 4, 2008)

the hell kinda plane is THAT? I've never seen anything like that.


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## FLYBOYJ (May 4, 2008)

Trebor said:


> the hell kinda plane is THAT? I've never seen anything like that.



Northrop XP-79 - Wikipedia, the free encyclopedia


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## drgondog (May 4, 2008)

buzzard said:


> A fair number of jet fighters were designed without bubble-type canopies. The F4D Skyray, F-8, F-5, F-102, F-106, Tu-128, MiG-23, MiG-25, Mirage III, Draken and Viggen come to mind. Some of these were designed as pure intercepters, but the F-8 certainly wasn't...
> 
> *No, the F-8 was the last of the Gunfighters for 15 years, was the Fleet Air Superiority beast and probably did not have the bubble canopy because of the variable incidence wing behind the canopy - it and the other birds were designed before advanced computational models and computers made sophisticated designs cheaper to model and faster - to explore better canopy designs, for example.*
> 
> ...



Probably the relative same number as the P-40, P-47D Razorback, P-51B, Hurricane, etc. I also suspect (can't prove) that there was little difference in total flat plate drag between the Birdcage, Malcolm Hood and Bubble at least not enough to slow it down more than external fuel or cannon pod mounts.


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## kool kitty89 (May 4, 2008)

I meant that the turtleback/razorback configurations of the high performance jets would imply that it was advantageous from a drag stand point, otherwise it would make no sense not to use a bubble canopy. 

I never disagreed with the visability advantage the bubble canopy gave.

I also agree that the razorback itsself would add next to no protection, but armor (particularly head armor) can be added more effectively w/out trying to maintain rear view. But in some cases (like the many models of the P-39) head armor was omitted to allow the rear view, this would leave the pilot vulnerable though.
Another option was to fit a slab of bulet proof glass behind the pilot which would give both advantages. (this was done on many Soviet P-39's, as head armor allowed almot no rear visibility for that a/c, some Bf 109's wih Galland hood used that too iirc)

There are compromise canopy designs as well, other than the Malcolm hood (which really isn't better than a clearview un-bulged canopy hood). Replacing some of the rear fusalage decking with plexiglass can be almost as effective as a bubble canopy. The P-36 is the first major example I can think of, with scallopped rear fusalage sides, same as used on the P-40. The P-40N utilized a frameless hood and plexiglass decking extending to the top of the fuselage.
The Finnish Myrsky used a similar design, as did the Galland hood (albeit less extreme). As did the spitfire, and (barely) the Hellcat.


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## drgondog (May 4, 2008)

renrich said:


> If you will notice, almost all post WW2 US fighters have bubble canopies whereas most Soviet fighters (after Mig 15,17) had a kind of razorback type design. There must be some drag factor working there. From my tiny experience flying an L39, one is strapped in so tight you can't turn around and look behind very far anyway. I have a friend who was an IP in Huns at the Fighter Weapons School(2000 hours in Huns) whom I asked about that. He said it was difficult to see much of the rear 180 degrees and he knew one hot pilot who in ACM disconnected most of his harness so he could utilise the bubble canopy.



Rich - the design factors driving a canopy design include shock wave characteristics for supersonic flight, temperature and visibility. The 50's and 60's (through 68 timeframe) designers weren't much concerned with visibility because 'gunfighting was dead' and the 102/106 and 105 were designed with entirely different missions than air to air against fighters.

I must confess that I would not be loosening up 'much' particularly in an F100's relatively small cockpit vs say compared to an A-10 or F-105 or and F-15but I'm sure he knows what he is talking about.. just enough to enable a slightly greater swivel but not enough slack to whack your head against the canopy in an 8g turn?


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## drgondog (May 4, 2008)

kool kitty89 said:


> I meant that the turtleback/razorback configurations of the high performance jets would imply that it was advantageous from a drag stand point, otherwise it would make no sense not to use a bubble canopy.
> 
> *More likely for the M 2.5 and above performers heat was a bigger factor.*
> 
> ...



KK - the Malcolm Hood was also 'bulged' on the sides and really did offer better visibility to 730 on either side and better visibility over the trailing edge of the wing - not to mention no stiffeners or other distractions that a P-51B or 109G had...


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## kool kitty89 (May 4, 2008)

I also agree that adied pylons or gun pods will have a greater (and more predictable) effect on drag than changes in canopy design.

But then there's cases like with the P-80 where the Lockheed tip-tanks actually reduce drag and increase wing efficiency and roll rate. (acting as primative winglets, resulting in a reduction of vortex at the wingtips)

But that's kind of counterintuitive, like the case with the P-51's canopy.


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## drgondog (May 4, 2008)

kool kitty89 said:


> I also agree that adied pylons or gun pods will have a greater (and more predictable) effect on drag than changes in canopy design.
> 
> But then there's cases like with the P-80 where the Lockheed tip-tanks actually reduce drag and increase wing efficiency and roll rate. (acting as primative winglets, resulting in a reduction of vortex at the wingtips)
> 
> But that's kind of counterintuitive, like the case with the P-51's canopy.



KK - in a sense yes. In the early days of wind tunnels and airfoil theory, the wing extended to each side of the wind tunnel and drag figures were lower than in real life.. why? The 2-D effect permitted no induced drag at the tip.

The P-80 wing tank assisted the 2-D Flat Plate effect and reduced induced drag. Winglet on modern aircraft combine that effect with also reducing the concentrated tip vortex - also reducing drag.

As to assisting roll rate for the P-80 I really have no opinion... that IS counter intuitive because a wing tank would INCREASE rolling moment of Inertia which would tend to slow rate of roll.


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## kool kitty89 (May 4, 2008)

On the Malcolm hood, I was comparing an unbulged framless canopy, not the "birdcage type" but I do agree that the bulge does help a little.

And another thing to note with the P-40N is that the frameless hood has the larger bordering frame at it's base, which blocks some of the view that the older framed one didn't.

And as to the armor plate, the thin walled 20mm HE mine rounds also had very poor penetration (as did the HE 13 mm rounds) causing mostly surface damage to the aluminum structure, so the armor plate (or thick armor glass slab) should usually be able to block that as well.


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## kool kitty89 (May 4, 2008)

For roll the P-47N had added outer wing tanks in the longer wings, but the clipped tips gave it roll better than the normal wing.

On the P-80 the better roll may be with empty tanks, I read the same for the F9F's perminant tip tanks.

And is the 2-D effect the same as the "endplate effect."


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## claidemore (May 5, 2008)

buzzard said:


> I've always wondered how many '109 pilots died because of that crappy canopy. If they could make something like the Me 262, you'd think that, at the very least, the Galland hood could have been introduced by '42.



Back in 1938? they tied a couple 109 airframes to a radial engine for testing. Those two 'radial 109s' did have a bubble canopy, much like the one used an the FW190.

Yet they did not introduce the bubble canopy into production 109s. I asked Soren why, he said it was because they caused more drag. Not sure if thats true, or if they didn't want to go to the trouble of retooling production (odd since the Soviets did it for Yaks and La5s), or if it was a stability issue. (109 has a fairly small vertical stabilizer.)


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## kool kitty89 (May 5, 2008)

Also the Galland hood offers pretty good visibility with that narrow fuselage, and it was a fairly simple conversion from the older canopy design. And due to the small fuselage there isn't much space to cut away decking for a bubble canopy, meaning that the added view wouldn't be much better than with the Galland hood. A sliding canopy has other advantages over the hinged on though.

Plus the pilots field of vision is also limited by how far he can turn and look over his shoulder anyway, without a mirror. (usually limited to something like 280-300 degrees) Granted another advantage of the bubble canopy would be the internal mounted mirror. (otherwise necessitating an external mirror which added drag)

Plus buzzard's original comment was on the delay in implementing the Galland hood, the "crappy canopy" being the older one.


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