Why were most early WW2 fighters designed with limited rear visibility?

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The notion that 90 percent (or whatever) of shoot-downs never saw their attacker is unfortunately accepted as gospel. Apparently it started with Ray Toliver's bio of Hartmann, who made that assertion presumably based on his experience.

But

I'd attended enough postmortems in fighter aces "ready room" (hospitality suite) sessions to suspect otherwise. So when I distributed an air combat survey to the membership, I got over 200 replies. Here's the lowdown:

From WW I to the jet age, averaging responses from all theaters and services, both as "givers" and "receivers," 20 to 25 percent were by surprise. That tracked nicely with von Richthofen's stats if you take time to compute them. And he of course was the ultimate stocker.
 
My aerodynamics kahunas say that prewar conventional wisdom held that a faired-in cockpit (think 109/Spit/P40) yielded reduced drag and hence more speed.

Thing was:

It probably was not enough to offset the tactical downside--reduced visibility especially in the important rear hemisphere.

I've noted elsewhere that a couple of aces said they preferred the B/C Mustang fitted with a Malcolm hood, which could be more bulged than the 360-degree canopy, to the extent that it was possible to look aft UNDER the horizontals.

We still live with the aerodynamic downside of 360-degree canopies because even with FIGHTERJETS (gaaak) it takes fuel to push that bubble thru the atmosphere.
 
There are two issues here: 1. Aerodynamic drag and its influence on the airplane's overall performance; and 2. Pilot's visibility.

As for 1.: Canopy drag is only one of many drag related factors affecting the aircraft performance. In WW2 aircraft, wing profiles and configuration and engine installation (with cooling) played a much bigger part in the overall aerodynamic drag issue. When it comes to drag due to canopy configurations, the difference between the canopy configurations is smaller. A streamlined and molded configuration as seen for example on the FW190 (and for that matter and much more modern, on the F-4) with well rounded forward windshield is the best when it comes to overall cockpit drag (typical drag coefficient of 0.09). When it comes to bubble enclosures, the typical drag coefficient is 0.1 to 0.15. Furthermore, the drag on bubble canopies is very much dependent on the ratio between the height of the canopy and its length where the best ratio is 12. That is why the drag (negative) contribution of the Ki-43 or Whirlwind canopies were probably higher than on a P-51 because they were short.

As for 2.: My opinion is that the issue was dictated by hubris and conservatism manifested in an attitude of "me the aggressor and I am coming after you - nobody will be coming at me from the back" (or something like that...) The difficulty of making large plexiglass shapes did not stop some aircraft such as the A6M and Ki-43 from having a "bubble" canopy. In the course of WW2, all evolving aircraft designs (P-51C to P-51D, F6F to F8F, Spitfire to late marks/Seafire/Spitful, Hurricane to Tempest, P-47D etc.) went from framed canopies to bubble ones. Reason: pilot's demand for better rearward and all around vision.
 
Just Schmidt said:
I think the main reason for the razorbacks is to do with aerodynamics, as the air moves more smoothly over the cockpit.
Click to expand...
Also the razorback added side area that increased lateral stability... after a short run of P-51Ds with the bubble canopy, they added a triangle fillet at the base of the vertical tail to restore lateral stability that had been lost.

Look at these pics - the ones from Iwo Jima show the "add-on" nature of the fillet quite well.

8th AF P-51 over England, no fillet:




375th FS over England, one with two without:




21st Fighter Group Iwo Jima, all with:

 
The Hurricane to Tempest went backwards with the early Typhoon and Tornado which were worse than the Hurricane.
 
Copied from the British Miles M.52 supersonic research aircraft that got cancelled (But not for that reason!)?

Miles M.52 - Wikipedia

en.m.wikipedia.org

Then we have the British prone pilot research project that reached a Meteor prototype (someone posted a photo of it at Cosford).

PROTOTYPES PRONE-POSITION AIRCRAFT

PROTOTYPES PRONE-POSITION AIRCRAFT Ken Ellis describes Britain’s...
www.key.aero
 
I would have to say (take it or leave it) that the lack of visibility was due to most of them having armor plating behind the seat so when those 30cal rounds were tearing through the air frame it wasn't a straight shot to the pilot, and they had at lease some chance to get out.
if you look at the P-51D, though it had a bubble canopy there was still a fairly "vision" limiting armor plate attached to the pilots seat, same with the FW-190 and BF-109
in conclusion to my observations, theirs not much vision limiting going on here.
 
Granted, I like the bubble canopies on most later World War II fighters and they probably did offer better than average overall visibility, there's one problem. Humans aren't owls. We can't turn our heads 270 degree in all directions. That's IMO the limiting factor more than anything even with a bubble canopy.
 
While our cranium rotation is limited to a certain degree, what you can do is turn your shoulders by leaning forward and rotating your torso. Also your eyes swivel to a small degree and you have the use of peripheral vision. Here is a fighter with a "bubble" canopy but not a good one. When the pilot leans forward and rotates he still has to look around the bulkhead area that sits behind him.



Here is a contemporary aircraft to the Mi-29 that solved for rear visability.


Of note is the lack of any bulkhead or visual obstacle behind the ejection seat. And to look around the ejection seat we would lean right, rotate our torso to the left, twist our necks and look around the RIGHT side of the ejection seat, or the same side we we're leaning into.

Cheers,
Biff
 
The removal of the aft top deck for the 'Cockpit Enclosure, Sliding' (P-51D) had absolutley zero effect on lateral stability. Said lateral instability following installation of Merlin in Mustang I at R-R was discovered immediately - and the first dorsal fin was installed on AL963, and reported to NAA in Feb1943.

The production kits for 104-25001 (for P-51B/C) and 109-25001 Fin were released from engineering in late March (21st and 30th) 1944. ALL P-51B/C/D in ETO absent the DF were modified with the DFs at Base Service Group near or on AAF Fighter fields
 

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GreenKnight121 said:
Also the razorback added side area that increased lateral stability... after a short run of P-51Ds with the bubble canopy, they added a triangle fillet at the base of the vertical tail to restore lateral stability that had been lost.
Click to expand...

To add to earlier exchange -
The first DF installed by R-R on AL963 circa Dec 1942. Reported to NAA in Feb 1943.
NAA designed and tested both DF and Fin aps in mid 1943 on P-51B-1-NA 43-12095, then dispatched 43-12095 to NACA Langley
NAA installed DF on P-51D-5-NA 44-13255 #4 in March 1944.
March 1944 production drawings released
March 1944 the first production insertion for new DF Planned for mid Block P-51D-5-NA and entire last block (NA111) P-51C-10-NT
P51C-10-NT #1 44-10753 July 1944
P-51D-5-NA #651 44-13903 July 1944
T.O. issued April 1944 to install field kits on P-51B/C and P-51D April 1944
Kits delivered to BAD2 Warton for both airframe types n June 1944 and distributed to Service Groups June/July 1944 for local FG installation.

The design objective was aerodynamic 'smoothing' of prop votex on empennage to reduce up/downloads on Horiz.Stab and side loads on Fin/Rudder.
Empennage failure was linked to strong Yaw inputs and asymetric loads in sideslip/snap roll at high speed.
Reverse Rudder Boost tab was also included in the DF installation. The penalty was slightly lower Roll rate and increased force on rudder pedals at high speed.

The DF served zero structural pupose. It added nothing to 'bend' resistance of Fin/Rudder due to side loads.
 

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Absolutely correct. In dog-fighting manoeuvres you damn-well do learn to contort your body, head and neck to extreme angles, often with your head also rolled right back and your eyes rolled too the stops! Even in an equal advantage position in the fight you may well be on opposite sides of the circle pulling many G's and you HAVE to keep visual! You also have to learn how to fly the aircraft at the limits without looking forward all the time! Gun Air to Air fighting is very physical, during air combat training everyone used to go up several collar sizes due to neck muscle development!
The cockpit armour of the WW2 era does illustrate the risk/benefit equation. Short range gun was the only real weapon and the value of seat/back/head armour was considerable as it could prevent pilot injuries/death in many situations where the fight was not lost, just hits taken. However, for hits from decent cannon fire, protecting the pilot was going to need a lot of armour. Various missile lethalities also change the cost/benefit in post WW2.
Lookout and spotting your enemy is important. Head movement and a good visual scan technique is critical if you want to spot other aircraft, you have to look around your blindspots!
Cheers

Eng
 
Great photos, the P-51 brought all the latest technology together to make the Cadillac of the Sky.
 
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