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enter image description here

Why, until recently, were smooth nose sections not popular? By smooth I mean without a break between the nose and windshield. (The question focuses on airliners.)

Seeing the Starliner (left) and DC-7 (middle), which were vying for the transatlantic market, with their almost perpendicular windshields, I wonder if they were more slanted and followed the nose -- like the Commando (right), for example, which proves it was possible -- enough drag reduction would have helped their payloads on windy days.

The Commando style windshields only made a comeback with the 787 and A350 -- the 747 gets close, but like the 75/76/777, there is still a break.

Manufacturing difficulty:
I don't think that's the reason (unless proven otherwise), because the noses are already smooth. The nose could start from the top surface of the fuselage, and cut-outs to be made where the windshield panels would go.

Windshield materials:
Plexiglas was used early on and on wartime aircraft with complex curvatures.


Image sources:
- https://imgur.com/iA7tbFV
- https://airandspace.si.edu/multimedia-gallery/dc-7jpg
- http://www.historynet.com/going-commando.htm

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  • $\begingroup$ What manufacturer made the Commando? $\endgroup$ – CrossRoads Jun 28 '18 at 11:57
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    $\begingroup$ @CrossRoads - Curtiss-Wright. $\endgroup$ – ymb1 Jun 28 '18 at 11:59
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    $\begingroup$ You seem to have forgotten the DH Comet and Sud Caravelle (which used the Comet nose section). Somewhat ironically, the latest jetliners (787, A350, C-series), have ended-up with a nose shape very similar to that of the very first jetliner. Perhaps the real question is why other airliners didn't follow the precedent set by the Comet. $\endgroup$ – Fiddlesticks Jun 28 '18 at 16:38
  • $\begingroup$ Is the ability to use the same pane shape / glass piece part number multiple times on the plane a factor too? I mean it's hard to tell exactly but The Starliner looks like it might have as few as 3 unique pane shapes and many of the glass pieces pictured look like they don't need to be mirrored on the other side of the plane like a lot of the fancier modern ones do $\endgroup$ – StarWeaver Jun 29 '18 at 8:44
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First, the Commando wasn't unique in having a 'stepless' cockpit design- the Boeing 307 Stratoliner, for example had them. Other military aircraft too had them, due to a few reasons like pressurization and the excellent visibility (He 111, Ju 388, B-29 Superfortress, the list goes on... etc) they offered.

While it's true that having this design improves the aerodynamics of the aircraft, there are other things to consider.

  • More complex a shape, more difficult is it to manufacture usually (which increases cost). Aircraft design, then as is now is a trade-off. The designer has to select a nose design based on trade-offs between various factors like aerodynamics, ease of manufacture, location of LRUs etc.

In fact, during original design of Lockheed constellation, multiple nose configurations were considered, which included completely faired nose (along with 'bug-eye' types). That the conventional arrangement was finally selected indicates that the designers decided that the drag reduction offered wasn't worthwhile.

In order to achieve ideal visibility characteristics for the pilot, the entire nose and cockpit of the CW-20E was redesigned to incorporate a flat glass windshield with negligible refractive and reflective errors. At the same time, the field of vision was increased.

indicates that this was definitely a consideration.

The present scenario is different- better materials and manufacturing techniques are available- not only for the windshields reducing errors and quality issues but also the fuselage shell, enabling optimizing structures for better aerodynamics.

I believe the Commando erred on the side of the aerodynamics- it had fairings between the top and bottom fuselage halves, which were later deleted, as flight tests showed they provided no improvement in performance. According to George A Page, Chief Engineer St Louis Airplane Division of Curtiss-Wright Corporation, the C-46 had not only stepless cockpit, but also 'tunnel type' cowlings to reduce drag.

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  • $\begingroup$ Very nice info -- For clarification, I gave the Commando as an example but didn't say it was the only one, I didn't mention the rest because their green-house noses (where the bombardier sat) have no use in air transport, the Commando seemed like a better fit. $\endgroup$ – ymb1 Jun 28 '18 at 15:12
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    $\begingroup$ Also even without refractive and reflective errors, at more oblique angle the reflection is stronger. $\endgroup$ – Jan Hudec Jun 28 '18 at 21:07
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Because it's bloody difficult to make the curved shapes out of the materials used until recently, with the technology available at the time.

The few aircraft that had it in the past generally were very expensive and labour intensive to build, compared to competitors, and therefore not economically successful. Now, with improved manufacturing techniques and materials, plus the rising cost of fuel, it's becoming ever more viable and more such are appearing.

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  • $\begingroup$ The noses are smooth already, they could start from the top and cutout where the windshield would go. $\endgroup$ – ymb1 Jun 28 '18 at 10:31
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    $\begingroup$ @ymb1 different materials. Glass and early clear plastics are extremely hard to get into a delicately curved shape and maintain transparency without a lot of distortion. $\endgroup$ – jwenting Jun 28 '18 at 10:37
  • $\begingroup$ I don't know, Plexiglas was used early on and on wartime aircraft with complex curvatures. $\endgroup$ – ymb1 Jun 28 '18 at 10:45
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    $\begingroup$ @ymb1 in wartime, winning is more important than economic efficiency. The combat life of military aircraft is of the order of a few hours, compared with a few decades for a civil passenger plane. Almost all military flight is training, not combat, but you don't design a fighter aircraft to be an efficient training platform. $\endgroup$ – alephzero Jun 28 '18 at 15:38
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    $\begingroup$ @ymb1 Military aircraft do not have the birdstrike and pressurization redundancy requirements that civilian airliners do (which has led to accidents and deaths), so their transparencies can be made much thinner, and often out of a single layer. Modern civilian windshields have around 8 layers, consisting of at least two layers that can withstand full pressurization loads. $\endgroup$ – user71659 Jun 28 '18 at 17:19
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Blow-molded canopies (like the acrylic one on the P-51D) were relatively expensive in the late WWII and early post-War periods when the early-modern airliners were designed. Cost is an important factor in airliner design, and was even in 1950.

Additional cost factors (contributing to the high cost of deeply or compound curved windshields) are that the materials (acrylic, aka Plexiglas or, by preference for its impact resistance, polycarbonate aka Lexan) were new, cutting edge materials in the early 1950s. Further, molding these materials in compound curves had a high drop-out rate due to distortions forming in the sheet material during heat forming.

Add to the above the need for very large panes to achieve required levels of visibility when the pilot is looking through at a sharp angle, and the difficulty of controlling reflections with strong sunlight falling on the (otherwise useless) panel area under the extended windscreen area, and you have a serious practicality issue with the sharply angles windscreens required for a Commando style.

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Part of the reason for the nose shape was a radar dish being installed there.

A new Bendix or RCA weather radar could be installed in the nose, which changed the nosecone shape.

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  • $\begingroup$ The nose became longer on the Super, but the break was still present on all the earlier variants. $\endgroup$ – ymb1 Jun 28 '18 at 11:58
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Aircraft windshields usually need to be serviced more often than other parts of the nose, because any debris (hail, birds etc) might cause scratch marks or fractures that obstruct the view and might cause a decompression. 'Bulky' windshields are easier to operate than curved ones.

Also, as pointed out in the blog post below [1], airliner front windows were also used for emergency escape purposes, as on China Airlines flight 120 incident [2]. A350, that has curved windshield, includes an additional escape hatch for pilots. The windshield itself is too small to be used as an escape route. Small surface area is preferred to mitigate damage to the windshield.

[1] http://bloga350.blogspot.com/2012/12/a350-xwb-first-curved-windows-airbus-is.html

[2] https://en.wikipedia.org/wiki/China_Airlines_Flight_120

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