Bubble Canopy.

[J.A.W.]

Why the gradual drift away from the (Hawker introduced to combat-type) clear blown one-piece bubble canopy
- as the `50s drew on into the `60s ?

Was it an area-rule thing, or a thrust-drag-heat limitation issue?

Or just lack of combat - whereby fighter jocks would be demanding.. "Where's my 'kin bubble canopy?"

 

[J.A.W.]

Dunno why this subject got 'moved'..
..wasn't the 'bubble canopy' effectively.. 'unbuilt'.. between the `40s ( F-86) & the `70s ( F-16)...

 

[Stargazer]

I think that's because you were not discussing an aircraft project, but a technical feature of production aircraft and the possible technical or political choices which induce choosing it or opting it out.

 

[Bill Walker]

A large part of the reason was the drift in military/designer philosophy away from close in dog fighting, where the pilot needed maximum visibility in all directions, to longer range radar directed engagements using air to air missiles, where the pilot was not interested in visual contact with the target.

The bubble canopy carried an aerodynamic drag penalty, and aircraft maximum speeds were increasing, so the bubble canopy became, in theory, unneeded. All this changed when conflicts like Viet Nam showed that there still times when the pilot needed to close with the enemy and get in a turning fight. At the risk of over generalizing, this need came about becasue modern conflicts were limited, compared to WW2, and there was often the possibility of non-combatant aircraft in the area. In all out war the theory is you know where the good guys are, and everything else in the air is a bad guy who gets an AAM. Modern reality is much more complicated.

 

[Jemiba]

Looking at the F-86 or Hawker Hunter, I think, the bubble canopy wasn't completely discarded,
but replaced by a more aerodynamical form of it, sacrficing a bit of the pilots vision for an aerodynamical
better shape. But, there still was a big difference between, say the razorback-versions of the P-47, or the
P-51B and the Sabre or Hunter, I think. The Mirage III or MiG 21, of course are better examples, but those
were Mach-2 fighters, designed in a way Bill explained.

 

[J.A.W.]

Thanks for the views expressed.

The initial P-47 bubble canopy conversion directly used the Typhoon canopy,
& Grumman jumped on that & more for F8F ideas from Hawker (albeit Miles had showed the way)..

Oddly, the MiG 21 canopy became worse, bubble-wise - as it grew a hump-back.

& high thrust - late `50s twin jets like Phantom & Lightning ought to have had no canopy aero-issues,
'cept heat-related maybe?

 

[Steve Pace]

Don't forget the P-51D/K, TP-51D, F-6D/K and P-51H Mustangs. -SP

 

[J.A.W.]

Well, sure the P-51 did get there.. eventually..
..after going through a Spitfire-type 'Malcolm-hood' conversion to rectify the 'jail-bars' in the B/C for ETO..

The Spitfire was late to the true tear-drop bubble too, while the P-38 never got there..

Odd that only the low-production build 'corn-cob' Corsair got one too.
& the Bf 109X radial prototype got one, but the rest dipped out..

The late FW 190s finally got a blown (bulged) bubble - after the A2G variants showed it was a good thing..

 

[famvburg]

I suppose the P-40 could be included via the P-40Q. Wasn't there a P-63 version that ended up with a true bubble?

 

[AeroFranz]

Let's not forget the Whirlwind!
And granted, it was heavily framed, but the Zero seemed to be designed for a good field of view.

 

[Bill Walker]

Oddly, the MiG 21 canopy became worse, bubble-wise - as it grew a hump-back.

The MiG-21 was originally designed as a dog fighter, based on the Russian experiences in Korea, so it started with a bubble. As time passed, and the Russians were not involved in Viet Nam style air combat, they lost interest in dog fighting and gave up the bubble canopy to grow internal volume.

& high thrust - late `50s twin jets like Phantom & Lightning ought to have had no canopy aero-issues,
'cept heat-related maybe?

Not sure what you mean by "no canopy aero issues". Bubble canopies create drag, independent of engine power. Big engines help overcome the drag, but for a given engine size the bubble canopy will slow acceleration, climb, and top speed.

Heat did play a factor in early Mach 2 designs, because of the limited materials and forming techniques available to make bubble canopies back then. Just look at an F-102 or F-106 canopy for a typical 1950s high temperature canopy design.
[/quote]

 

[J.A.W.]

Phantom & Lightning were not exactly lacking power-wise, so, no particular reason to fit severely streamlined, but somewhat restrictive vision canopies - compared with earlier (F-86 ) or later (F-16) - bubbles.

The really fast interceptor ( not intended to dogfight) contemporary designs like XF-108/MiG 25 may have had more reason to have a priority toward canopy heat (& nuke) proofing, but pilots would surely prefer
a better combat view.

Was the W.Whirlwind canopy a framed bubble, or a 2-piece, like the F-104?

 

[lastdingo]

You need to sacrifice a lot of volume behind the cockpit which you could use for low density avionics (no centre of gravity problem) without additional drag.

A true one-piece canopy was also challenged by the bird strike threat.

 

[J.A.W.]

Indeed, the windscreen heat/bird-strike factor is a biggie.

The F-16 appeared to follow the early MiG 21 style of a main front canopy/rear hinge type.

'Phantom Over Vietnam' by John Trotti has an anecdote of the windscreen heat warning alarm going off
during a high Mach flight test, & causing a mandatory abort..

 

[Bill Walker]

Phantom & Lightning were not exactly lacking power-wise, so, no particular reason to fit severely streamlined, but somewhat restrictive vision canopies - compared with earlier (F-86 ) or later (F-16) - bubbles.

What counts in a fighter is excess power - what is left over after you overcome drag. Excess power gives you climb, acceleration, and turning ability. Any fighter pilot wants MORE of these, no matter how much you give him. Less drag = more excess power. If (as the theory went in the 1960s) the pilot was only watching his radar scope and instruments while accelerating, climbing and turning, why give him more canopy than he needs? Add to this the problems others pointed out about bird strikes and heating, which required modern materials and fabrication methods to overcome, and the small canopies of the Phantom, Lightning, Mirage III, CF-105, F-106, MiG-23 etc. made sense at the time.

You can see the point where the thinking turned by comparing the early mockups of what became the Jaguar (no bulge in the canopy) with the final production Jaguar canopy. The results of the Viet Nam air war were becoming known at about that time.