Canopy aerodynamics

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spicmart

Staff Sergeant
916
194
May 11, 2008
Which features influence the aerodynamics of fighter canopies and to what extent?

Of course there is the angled windshield and the flushness of struts. But what about curved windows?
Which fighters do you think have especially bad or good canopy aerodynamics?
 
Better canopy design is fraught with contradictions.

Better for combat or better for aerodynamics?

Here's the Anaquim Project aircraft:


It goes 324 mph on about 220 hp. But you really can't see anything forward, making it best for aerodynamics and worst for combat.

Here's a Miles Master:


Definitely better for visibility, but not exactly the most aerodynamics thing around.

To me, one of the better canopies was on the Fw 190 for a good compromise between aerodynamic and visibility, leaning a bit toward the aerodynamic side.


If you go look at it, the early Bell XP-39 had a canopy better suited for visibility and, after the NACA-recommended cleanup, the later XP-39 was better aerodynamically.
 
muskeg13 said:
It doesn't get much worse than this:View attachment 776663 Blackburn Skua
Click to expand...
It did on some airliners.

First two objectives were protecting the pilot while allowing him/them to see out. Streamlining was usually (but not always) 3rd.
The sloped forward windshields were supposed to reduce reflections of the instruments in the windshield/s.
Figuring out to keep windscreens clear of crap (oil leaking from engine) without windshield wipers may have taken a few tries. Or trying for less fogging/freezing in rapid descents.
Not saying it worked but they had to start somewhere.
At least the Skua had some vision over the nose for carrier landing.
 
The aerodynamic penalty is almost nothing.

If you look at the most often-quoted specs, the turtledeck has a best speed of 444 mph and the bubble is 437 mph. The best-speed heights are very slightly different. Your speed may vary.

That's a whopping 1.58% difference, which falls right within the differences to be expected among individual airplanes within the same manufacturing batch.

Practically speaking, I'd call that a dead heat.

At the Planes of Fame, we fly anywhere from 3 to 6 P-51s. Mostly three. The stock P-51Ds (two of them) vary more than 7 mph between them at the same power and rpm. In the case of these two, one can use 2 inches less manifold pressure to stay side-by-side, meaning that, at identical power settings, it is faster. That's pretty normal variation.
 
FWIW, people can check out the report by NACA, when they were trying different ways to lessen the effects of the compresibility on the YP-38. Includes also the fixes to the canopy.
Granted, these efforts combined were mostly beneficial to the speeds above 420 mph TAS at 20000 ft, going on to 460+ mph at the altitude. How much a perfect canopy is a must-have for the speeds of 550-600-650 mph is everyone's guess.
 
Have you ever noticed in some older cars the instrument dials can be seen reflected in the windshield, under some light conditions, like in the dark?
The way to prevent that is put a brow at the top of the dash, and all modern cars have that.
Having a reverse slanted windshield would also prevent that reflection.

With the big radial on the front of that Breda, I don't see how he had much forward vision to improve, but I guess every little bit helped.
 
Most of the older, 1940s at least, had a small toggle switch to turn off the dash lights at night to reduce visual annoyance. The newer cars began to have a Rheostat in the switch to turn dash lights down, or off. On much later, GM at least, I found if less than full brightness, the area near the switch gets warm. My 93 Buick Roadmonster dash was too warm for peace of mind when dash lights dimmed, so I always left the dash lights full on at night.
 
This bubble canopy provides both good visibility and good enough aerodynamics for Mach 2. Compared to WWII planes distinctive features are the low angles front/back, as well as smooth transition between the canopy and the fuselage. No armored windscreen though.

 
If you took the front canopy of the Fw 190 compared to the other fighters which would you rate better or worse.
Are fighters with curved frontal side.windows (P-51B/D, or, say, some type of Yak-3, frontscreen less draggy?
 
spicmart said:
If you took the front canopy of the Fw 190 compared to the other fighters which would you rate better or worse.
Are fighters with curved frontal side.windows (P-51B/D, or, say, some type of Yak-3, frontscreen less draggy?
Click to expand...
Intuitively, I'd say curved side windows are better. To know exactly how much better you'd need wind tunnel tests and/or CFD. And enough better to be worth the additional manufacturing complexity? That again depends on how exactly you're planning to manufacture them etc.
 
Straying off topic, but...dash dimmer rheostat overheating was probably a common GM problem. I experienced the same in my 1994 Yukon. The dash light dimmer was always at least warm, but sometimes I was afraid of it being so hot as to melt plastic or start a fire. Fortunately, this problem seems to have been fixed in later models. My "new" current vehicle, a 2005 Yukon, doesn't have this problem.

Roadmonster- Good!
 
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