The Insane Engineering of the 787

Summary

本视频深入探讨了波音787梦想飞机如何革新航空工业。通过大量使用复合材料，如碳纤维增强塑料，波音787实现了更轻、更坚固的机身设计，从而提高了燃油效率和乘客舒适度。视频还讨论了787的创新特性，包括其超临界机翼、电加热除冰系统以及为减少阻力而设计的特别技术。尽管复合材料带来了一些挑战，如与铝的电偶腐蚀问题，但波音通过使用钛等材料和创新的3D打印技术来解决这些问题。

Takeaways

• 🛫 航空业正在经历一场革命，大型客机如A380和B747的时代已经结束，新一代飞机正在崛起。
• 💰 波音公司的787梦想飞机是对航空业未来300亿美元的赌注，这一赌注取得了成功。
• 🌐 787梦想飞机是第一款主要使用复合材料（如碳纤维增强塑料）制造的商业客机，复合材料的比重占到了55%。
• 🔨 复合材料由两种或更多种材料组成，如碳纤维增强塑料，它由极其坚固的碳纤维和塑料树脂粘合而成。
• 🚀 波音使用自动化带材铺设技术生产大型飞机部件，提高了生产效率并减少了人工成本。
• 📈 787梦想飞机的机身强度允许其内部气压更高，相当于更低的海拔高度，提升了乘客的舒适度。
• 🪟 由于复合材料的疲劳免疫特性，787的窗户可以做得非常大，而不会产生应力集中。
• 🌬️ 787的机身和机翼设计减少了空气阻力，提高了气动效率，尤其是采用了超临界翼型。
• 🛠️ 波音公司为了降低成本，采用了3D打印钛金属零件的技术，减少了材料浪费并提高了生产速度。
• ⚡️ 787梦想飞机的设计考虑了雷电击中的保护措施，如铜条的铺设和氮气惰化系统。
• 🔄 787是第一款取消传统引气防冰系统的商业客机，采用了更高效的电加热毯技术。
• 🎥 该视频脚本提供了对波音787梦想飞机革命性设计的深入分析，突出了其在材料、结构和系统方面的创新。

Q & A

波音787梦想飞机的开发背景是什么？

波音787梦想飞机的开发背景是航空业的一次革命，旨在取代以往的大型客机如A380和波音747。随着新飞机的加入，航空公司能够提供更多的直飞航线，并且票价也更为便宜。

波音787梦想飞机在材料上有哪些创新？

波音787梦想飞机在材料上的创新主要体现在其大量使用了复合材料，如碳纤维增强塑料，这使得它成为第一款主要使用这种新材料的商用客机。复合材料的使用带来了诸多优势，如减轻重量、提高燃油效率和增强飞机的舒适性。

复合材料在波音787梦想飞机中的比重是多少？

在波音787梦想飞机中，复合材料的比重达到了55%。

波音787梦想飞机的制造过程中使用了哪些先进技术？

波音787梦想飞机的制造过程中使用了自动化带材铺设技术，通过将预先浸渍有塑料树脂的碳纤维带材包裹在旋转的模具上来制造机身。此外，还使用了大型定制烤箱来固化树脂，并采用了钛合金3D打印技术来减少材料浪费和生产成本。

波音787梦想飞机的燃油效率如何？

波音787梦想飞机的燃油效率非常高，这得益于其轻量化设计和先进的空气动力学特性。复合材料的使用减少了飞机的重量，而流线型的机身和机翼设计则减少了空气阻力，从而降低了燃油消耗。

波音787梦想飞机的窗户为何比传统飞机更大？

波音787梦想飞机的窗户之所以比传统飞机更大，是因为其使用复合材料制造的机身具有更高的强度和耐疲劳性能，这使得飞机能够承受更大的窗口开口而不会出现结构问题。

波音787梦想飞机的机翼设计有哪些特点？

波音787梦想飞机的机翼设计具有高展弦比，这使得机翼在飞行中具有更高的灵活性和更低的阻力。此外，机翼的主梁和肋骨分别使用了碳纤维复合材料和铝合金，以实现最佳的强度和重量比。

波音787梦想飞机如何应对雷电击中的风险？

波音787梦想飞机通过在其机翼表面铺设铜带来确保电子有低电阻的路径沿着机翼表面流动，防止电子流向燃油箱并引发火花。同时，飞机还配备了氮气惰化系统，通过在油箱中填充氮气来防止点燃。

波音787梦想飞机的驾驶舱窗户框架最初是由什么材料制成的？

波音787梦想飞机的驾驶舱窗户框架最初是由钛合金制成的，以防止与碳纤维复合材料接触时发生的电偶腐蚀。后来为了降低成本，这些框架被改为铝制，并涂有特殊涂层以防止腐蚀。

波音787梦想飞机的除冰系统与传统飞机有何不同？

波音787梦想飞机采用了电加热毯来除冰，这种系统通过在飞机的缝翼上粘合电加热毯来加热机翼表面，从而融化或防止冰的形成。这与传统的从发动机提取热引气并将其输送到机翼前缘等易积冰区域的方法相比，更为高效且减少了燃油消耗。

波音787梦想飞机的燃油箱是如何防止爆炸风险的？

波音787梦想飞机的燃油箱通过氮气惰化系统来防止爆炸风险。该系统通过在油箱中填充氮气来排除氧气，因为燃烧需要氧气的存在。此外，飞机的燃油箱密封件和紧固件也经过特殊设计，以防止电火花的产生。

Outlines

00:00

🛫 航空业的革命与波音787梦想飞机

本段落介绍了航空业正在经历的革命，传统的大型客机如双层A380和波音747已不再流行，取而代之的是新一代飞机。波音787梦想飞机是这场革命的先锋，它是一个价值300亿美元的赌注，不仅改变了航空业的运作方式，也影响了未来飞机的设计和制造。787飞机55%的重量来自复合材料，如碳纤维增强塑料，这使得它成为首个主要使用这种新材料的商用客机。

05:03

🚀 波音787的复合材料优势

这段落详细解释了为什么航空业如此青睐复合材料，以及波音787如何利用这些优势。复合材料由两种或更多种材料组成，例如碳纤维增强塑料，它由极其强壮的碳纤维和塑料树脂粘合而成。碳纤维的强度是钢的5倍，但重量只有钢的五分之一。复合材料的灵活性使其在制造飞机精确而优雅的曲线时非常有用。波音使用自动化带材铺设技术来生产大型飞机部件，这种方法通过精确控制带材的重叠和纤维的方向，充分利用了碳纤维的拉伸强度。

10:04

🌬️ 波音787带来的航空旅行变革

本段落讨论了波音787对航空旅行的影响，包括更舒适的客舱压力、更大的窗户和航空公司运营的便利。787的强化机身能够承受更高的内部压力，减少乘客的不适感。此外，由于使用了复合材料，飞机可以设计出更大的窗户。787的单一大型机身部件消除了所有接缝和紧固件，减轻了重量并减少了燃油消耗。此外，787的机翼非常薄且优雅，复合材料的使用减少了阻力并提高了气动效率。

15:08

📈 波音787机翼的高纵横比设计

这段落解释了波音787机翼的高纵横比设计，以及它如何允许机翼在飞行中承受更大的弯曲。与传统的9:1纵横比相比，787的11:1纵横比意味着机翼更长更窄，能够在飞行中弯曲更多。这种设计减少了涡流阻力，因为翼展的增加减少了翼尖的压力混合，从而减少了能量损失。此外，787使用了超级临界翼型，这种翼型通过优化内部体积和延迟激波形成来提高飞行效率。

20:12

🌀 波音787的气动控制技术

本段落介绍了波音787使用的混合层流控制技术，这是一种减少飞机尾部湍流的创新设备。波音开发了这项技术，以延迟和控制湍流的形成，从而减少飞机的阻力。此外，段落还提到了波音787在设计上使用钛金属的原因，以及它如何通过3D打印技术来降低成本和提高质量。

25:12

💰 波音787的成本挑战与创新解决方案

这段落讨论了波音787在生产成本上面临的挑战，以及波音如何通过创新来降低成本。由于787的制造成本高于销售价格，波音在一段时间内每售出一架飞机都在亏损。为了尽快回收成本，波音寻求减少钛部件的使用，并与Norsk Titanium合作，采用3D打印技术制造钛部件。此外，波音还移除了一些昂贵的保护措施，如铜网和绝缘帽，尽管这引起了一些关注和批评。

30:18

✈️ 波音787的先进材料与系统

本段落总结了波音787使用的各种先进材料和系统，包括在飞机的前缘、尾部和发动机罩部分使用铝或其他金属，以及电加热毯用于除冰。波音787是第一款取消使用引气系统的商用客机，这一技术挑战导致了多个系统的完全重新设计和新型发动机的开发。视频的最后，提到了即将发布的关于波音787动力系统的新视频，以及通过Nebula和CuriosityStream捆绑优惠订阅频道的信息。

🎥 支持Real Engineering频道

这段落是关于如何通过订阅Nebula来支持Real Engineering频道，并享受无广告的视频观看体验和独家内容。作者提到了Nebula上的一些特色内容，如D-Day后勤系列和个人播客Genesis，并鼓励观众通过Nebula和CuriosityStream的捆绑优惠来支持频道。

Keywords

💡航空工业革命

航空工业革命指的是飞机制造业中发生的重大变革，这些变革使得飞机设计、制造和运营方式发生了根本性的变化。在视频中，提到了传统的大型客机如A380和波音747的时代已经结束，新一代的飞机如波音787梦想飞机正在引领这一变革。这些新飞机更加注重效率、舒适性和经济性，从而改变了航空旅行的整个面貌。

💡波音787梦想飞机

波音787梦想飞机是波音公司开发的一款革命性的商用飞机，它采用了大量复合材料，具有更高的燃油效率和乘客舒适度。该飞机的设计和制造标志着航空工业的一个新时代，它能够执行长距离航线，同时减少燃油消耗和运营成本。

💡复合材料

复合材料是由两种或两种以上不同材料组合而成的新型材料，例如碳纤维增强塑料。这些材料具有高强度、低重量的特点，非常适合用于飞机制造。复合材料的使用可以提高飞机的结构强度，减少重量，从而提高燃油效率和性能。

💡碳纤维

碳纤维是一种由成千上万根微小碳丝组成的高强度、高刚性的新型材料。它比钢铁轻得多，但强度却是钢铁的5倍。碳纤维本身不能单独形成固体部件，需要通过塑料树脂粘合在一起，形成坚固而灵活的复合材料。

💡气动弹性剪裁

气动弹性剪裁是一种先进的飞机设计技术，它允许飞机的机翼在飞行过程中根据速度的不同而改变形状，以优化气动性能。这种技术通过在不同区域使用不同刚度的材料，使机翼在飞行中实现最佳的气动效率。

💡超临界翼型

超临界翼型是一种特殊设计的飞机翼型，它通过优化翼型的形状来延迟激波的形成，从而提高飞机在高速飞行时的气动效率。这种翼型有助于飞机以更高的速度飞行，同时减少波阻，提高燃油效率。

💡混合层流控制

混合层流控制是一种减少飞机尾部湍流的技术，它通过特殊设计的飞机表面结构来延迟和控制湍流的形成。这种技术可以显著减少飞机在高速飞行时的阻力，从而降低燃油消耗。

💡钛合金

钛合金是一种高强度、耐腐蚀、重量轻的金属材料，常用于飞机的关键结构部件。然而，钛合金的成本较高，因此在飞机设计中需要权衡其性能优势和成本。

💡电偶腐蚀

电偶腐蚀是一种金属腐蚀现象，当两种电位不同的金属接触时，在电解质（如盐水）的作用下会发生电子和离子的交换，导致电位较低的金属（阳极）被腐蚀。

💡氮气惰化系统

氮气惰化系统是一种安全措施，通过在飞机的燃料箱中充满氮气来防止燃料箱发生火花和爆炸。由于氮气不支持燃烧，即使燃料箱中有燃料蒸汽，也因为缺乏氧气而无法点燃。

💡电加热除冰系统

电加热除冰系统是一种利用电能产生热量，从而防止或融化飞机关键部位如机翼前缘的冰层的技术。这种系统比传统的利用发动机引气进行除冰的方法更为高效，因为它不会产生额外的气动阻力和能量损失。

Highlights

航空业正在经历一场革命，大型客机如双层A380和凸背747的时代已经结束，新一代飞机正在取代它们。

波音787梦想飞机是航空业未来的30亿美元赌注，它不仅改变了航空业的运作方式，还影响了未来飞机的设计和制造。

波音787有55%的重量来自复合材料，如碳纤维增强塑料，这使其成为第一款主要使用这种新材料的商用客机。

复合材料由两种或更多种材料组成，例如碳纤维增强塑料，它由极其坚固的碳纤维和塑料树脂粘合而成。

波音使用自动化带材铺设技术生产大型飞机部件，这种方法通过精确控制带材的重叠和纤维的方向，最大化碳纤维的拉伸强度。

波音787的机身可以承受更高的内部气压，相当于6000英尺的高度，比以往的飞机低25%，提高了乘客的舒适度。

波音787的窗户非常大，这得益于复合材料对疲劳的相对免疫性，可以承受更大的开口而不会出现金属飞机上的压力集中问题。

波音787的机身结构减少了接缝和紧固件的使用，使得机身更轻，减少了燃油消耗，并且提高了空气动力学效率。

波音787的机翼具有高展弦比，这意味着机翼更长更窄，能够在飞行中承受更大的弯曲，从而减少了涡流阻力。

波音787使用了超级临界翼型，这种翼型通过特殊的形状设计延迟了激波的形成，提高了飞机的临界马赫数。

波音787的机翼使用了复合材料制造，允许工程师设计出能够在不同飞行速度下变形的翼型，这称为气动弹性定制。

波音787还采用了混合层流控制技术来减少飞机尾部的湍流，这项技术可以减少燃油消耗高达30%。

波音787使用了15%的钛材料，这是因为钛能够防止与碳纤维复合材料接触时发生的电偶腐蚀。

波音与Norsk Titanium合作，使用3D打印技术制造钛部件，这种方法比传统的粉末激光熔化技术更快、更节省材料。

波音787的机翼前缘和尾部使用了铝或其他金属，因为复合材料在抗冲击性方面表现不佳，而金属在冲击时能够变形而不是像复合材料那样碎裂。

波音787采用了电加热毛毯系统进行除冰，这种系统比以前的从发动机提取热空气的系统效率更高，减少了燃油消耗和阻力。

波音787是第一款商用客机，完全取消了用于除冰的发动机引气系统，这需要对多个系统进行彻底的重新设计。

Transcripts

This episode of Real Engineering is brought to you  by the Curiosity Stream and Nebula bundle deal.  

Sign up now to watch the hour-long version  of this video, linked in the description. 

If you haven’t been paying attention you have  not noticed the revolution happening in the  

airline industry. The days of attempting to build  bigger and bigger airliners like the 850 passenger  

double decker a380 and the 660 passenger humped  747 are gone. The behemoths are simply being  

outcompeted by a new generation of planes. Many  may mourn the slow demise of these iconic planes,  

but you are benefiting from this  change. The entire nature of air travel  

has changed to benefit you and your needs. Your local airport has more direct flights  

to distant lands than ever before, and  the prices of those tickets are cheaper  

than ever. Connecting flights are becoming rarer  and rarer as this new breed of plane takes over.  

The plane at the forefront of this revolution? The 787 dreamliner. A 30 billion dollar bet  

on the future of the airline industry. [1]  Boeing sat at the poker table and pushed all  

their chips forward. An all-in bet on  a radical new future, and it paid off. 

The 787 revolutionized not only  how the airline industry operates,  

but how future planes will be designed and built. This is the breakdown of the 787’s materials.  

By weight, 55% of the 787 is made from composite  materials, like carbon fibre reinforced plastics,  

making it the first commercial airliner  made primarily from this new age material.  

The 787 is rivalled only by the Airbus A350XWB,  introduced 4 years after the 787 in 2015. [2]. So,  

why are composite materials so desirable  for the airline industry and how has the 787  

made the most of their advantages? Composite materials are made up of two or more  

materials. Take carbon reinforced plastics. These  are composed of extremely strong carbon fibres  

bound together by a plastic resin. Carbon fibre,  made up of thousands of tiny thin fibres of  

carbon, is incredibly strong in tension. Up to 5  times stronger than steel, and one fifth of its  

weight. [3] But these tiny fibres can’t create a  solid part by themselves. This is an image of a  

human hair beside a carbon fibre, the carbon fibre  is the smaller one, and just like a human hair  

they can bend and flex and separate very easily.  So, we need to first bind them together with a  

plastic resin to form a solid material, otherwise  they just form a strong, but flexible fabric. 

That flexibility as a fabric is exactly what makes  composites so useful when creating the precise  

and elegant curves of an aircraft. With the right  tooling and designers, composite components can  

be made into almost any shape imaginable. In the past, a disadvantage of making large  

aircraft components from composites was  the time taken to manually lay-up parts.  

Where layers of carbon fiber and plastic resin had  to be carefully constructed. It required skilled  

technicians and was inherently difficult to  scale to the production quantities Boeing needed. 

To get around this problem Boeing uses automated  tape laying to produce massive aircraft sections.  

The 787s fuselage is created by wrapping a carbon  fibre tape impregnated with a plastic resin around  

a rotating mould of the fuselage. This machine  precisely controls the overlaps of the tap and  

the orientation of the fibres to ensure we get the  most out of the carbons tensile strength to resist  

the internal pressure loads and the longitudinal  bending loads the fuselage will experience. 

One of the problems with this manufacturing method  is that this part needs to be placed inside an  

oven to cure the resin. This hardens the plastic  and creates a solid composite structure. Ovens  

the size of a wide body jet airliner fuselage  are not exactly common, and this is often the  

limiting factor on parts made this way  and requires massive upfront investment  

to build a customized oven large enough to fit  the part, but the benefits are well worth it. 

The first and most obvious is the strength carbon  fibre provides. Previous generation airliners are  

typically pressurised to an equivalent pressure  of 8,000 feet. [4] That’s the same height as  

Mount Olympus in Washington State. High enough  that the lower pressure would reduce your oxygen  

intake and your stomach will bloat as the air  inside is higher pressure than the outside.  

This is uncomfortable and exacerbates the effects  of jet lag. Thanks to the 787s stronger fuselage,  

it can increase it’s internal air pressure to an  equivalent of 6,000 feets. 25% lower in altitude,  

and about 7.3% higher in pressure. [5] It may  not sound like a lot, but it goes a long way  

in making the journey more comfortable, at  the very least the person next to you won’t  

be farting as much. Less farting is always nice,  but my favourite benefit of the stronger fuselage  

is the absolutely massive windows. This is the 787 window, and these are windows  

of some equivalent aluminium airliners. They are  absolutely massive. In aircraft made primarily  

of aluminium, having holes this large in metal  panels would result in the build up of stress  

at the window boundaries, as the stress  contours have to deviate around the window.  

This stress does not exceed the material's  strength, but over repeated pressure cycles  

tiny imperfections in the metal can grow into ever  larger cracks and eventually fail. [6] Holes this  

large in an aluminium airliner would severely  shorten the plane's flying career before it  

needed to be fixed or disposed of, kinda like  cracks in McGregor's leg shortened his career,  

but it’s not a problem for the 787 thanks  to composites' relative immunity to fatigue.  

You could kick Dustin Poirier’s knee cap as  many times as you like with carbon fibre shins. 

The carbon fibre construction provides plenty  of benefits for the airline operators too.  

Because the fuselage is just one massive part,  Boeing was able to eliminate all joints and  

the fasteners needed to join them together. Sections that used to be made up of 1500  

aluminium sheets riveted together using 40 to 50  thousand fasteners are now just one massive carbon  

fibre section.[7] Carbon fiber's strength to  weight ratio already makes the fuselage lighter,  

but eliminating joints and fasteners  makes it even lighter again. 

The reduced weight reduces fuel burn. This  fuselage is also incredibly aerodynamic because  

it doesn’t have thousands of little bumps and  ridges all over it from those joints and rivets.

Animation 5a These surface imperfections make the  

plane’s surface rough and cause it to disturb  more airflow, increasing parasitic drag. [8] 

Composite materials help reduce drag in other  ways. One of my favourite things about the  

787 is its extremely thin and elegant wings. The main structural member of a wing is the wing  

spar. It’s primary role is to resist the upwards  bending forces during flight. It’s essentially  

just an I beam, a shape optimized to resist  bending loads. The wing spars of the 787 are  

constructed from carbon fibre composite, while the  ribs, the structural members connecting the two  

ribs that support the wing skin, are machined out  of solid aluminium plates. [9] The structure the  

rear and forward wing spars form with ribs running  between them is called the wing box, and it forms  

the main load bearing structure of the wing, while  also being a literal box for fuel to be stored. 

The carbon fibre spar provides the wing  fantastic strength. Strength is quantified  

by the force required to completely fracture  a material, but carbon fibre composites have  

another important quality that makes them perfect  for aircraft wings. Their maximum elastic strain.  

There are two types of deformation. Elastic and  plastic deformation. Elastic means the material  

will snap back into its original shape after  the load is removed, like an elastic band.  

Plastic means it will be permanently deform  and won’t return to its original shape  

once the load is removed. Something we don’t  want happening. This is permanent damage. 

Carbon fibre composites can deform further  before they strike this plastic deformation zone,  

at about 1.9% [10] while aircraft aluminium  begins permanently deforming at less that  

1% [11]. That means we can bend carbon composites  further before we need to worry about permanently  

deforming them , and that means we can make our  wings super flexible. During flight the wing tip  

of a 787 can move upwards by 3 metres, that sounds  a lot, but in order to get certified by the FAA  

every plane needs to be able to handle 150%  of the planes absolute maximum expected load  

during flight for 3 seconds, and during that test  the 787s wing bent upwards by 7.6 metres. [12] 

That’s a great deal of bending, despite carbon  fibre composites being stiffer than aluminium.  

Meaning, it takes more force to deform the  same volume of material, but critically, 

787 wings are not the same shape as their  aluminium counterparts. This ability to withstand  

greater bending allowed engineers to make the  787s wings with a higher aspect ratio. [13]

Aspect ratio is the ratio between  the wing span and mean chord,  

or wing width. A high aspect ratio would  be a long skinny wing like a glider,  

while a low aspect ratio would  be a delta wing of a fighter jet.

A traditional airliner has an aspect ratio of  about 9, like the 787s predecessor the 777,  

but the 787 has a massive aspect ratio at  11. [14] This is what causes the 787s wings  

to flex so much during flight. Composites are actually much stiffer  

than aluminium, but their ability to withstand  high deformation allowed the engineers at Boeing  

to create a much higher aspect ratio wing,  a longer narrower wing that would bend more,  

but this comes with some huge benefits. The planes with the highest aspect ratio  

are gliders. For an unpowered plane the  highest priority is minimizing energy lost  

to drag. This allows the glider to stay in the  air for extended periods with no engine. These  

types of aircraft typically have aspect ratios  greater than 30, and these aircraft have the  

lowest drag penalties as result of vortex drag. This is the drag caused by air mixing from the  

high pressure zone under the wing with low  pressure air above the wing, forming votives  

at the wing tip, by spreading the area of the wing  over a longer span we minimize the pressure that  

drives this mixing at the wing tip, and thus  minimizes the energy lost to the vortices. 

Normally higher aspect ratio wings have lower  internal volumes. For an unpowered glider this  

isn’t an issue, but for a plane that needs that  storage space for fuel it is. Less storage volume  

for fuel means lower range, and one of the primary  goals of the 787 is to be an efficient long range  

aircraft, capable of allowing airliners to open  new routes that were once deemed impossible. 

Thankfully modern planes like the 787 use a new  kind of aerofoil. The supercritical aerofoil.  

Older aerofoils looked something like this. A  reasonably symmetric design with a sharp nose  

and gentle curves on the upper and lower  surface. This is a supercritical wing. The  

leading edge is blunter with a larger  radius, the top is relatively flat,  

and the lower portion has this strange cusp at the  back. This aerofoil has much more useful internal  

volume thanks to it’s blunt leading edge  and larger thickness to chord ratio. [15] 

Helping solve our low internal volume problem  associated with high aspect ratio wings.  

The supercritical wing was first tested  by NASA on a modified TF-8A Crusader,  

and you can really see the similarities in design  ethos between this experimental plane’ s sleek  

wings with the 787s. But increased internal volume  is not why NASA developed the supercritical wing.  

NASA developed it to delay the onset  of shock wave formation over wings. 

When air travels over a wing, the air on top  accelerates. This means that even though the  

plane itself might be travelling below the  speed of sound, the air over the wings may  

break it and create a shock wave. This shockwave  decreases lift and causes an increase in drag,  

this kind of drag is called wave drag and planes  need to fly below the speed this occurs at.  

This speed is called the critical mach number. The supercritical wing was designed to increase  

the critical mach number. [16]The flat  top of the supercritical wing means the  

air does not accelerate as much as  it would over a classic aerofoil. 

Ofcourse, this causes a loss in lift because that  fast moving air is causing a drop in pressure on  

top of the wing. To compensate, supercritical  aerofoil has this concave curvature underneath  

the wing which causes an increase in pressure  there to compensate, this increase in pressure  

does not affect the critical mach number. While  the larger radius of the leading edge increases  

the lift generated at higher angles of attack. This is because air struggles to follow the  

tighter turns of a smaller radius leading edge,  which causes earlier flow detachment and stall.  

The larger radius delays this flow separation. This aerofoil shape changes continually as you  

travel the length of the wing. Twisting and  curving in computer calculated precision.  

Optimizing the wing shape to be as efficient as  possible, and the use of composites provided the  

engineers with the confidence that these shapes  could be manufactured. The skin is simply laid  

down on a mould with automated tape laying once  again, we don’t have to beat metal into shape each  

and every time we want to recreate these delicate  curves. The fibres of the wings have even been  

laid in a specific pattern to tailor the stiffness  of the wing in different areas. This means the  

wing deforms exactly as the 787s engineers want  it to as it gains speed. [17] So the wings shape  

actually changes during flight to better suit  the needs at different speeds. This is called  

aeroelastic tailoring and is the forefront of  state of the art aeronautical engineering today. 

The 787 also features a novel device designed  to reduce turbulent flow over the tail of the  

aircraft.Two types of flow states exist  in aerodynamics: Laminar flow occurs at  

low velocities and is characterised by fluid  layers flowing smoothly over each other in neat  

orderly layers. Laminar flow is predictable and  non-erratic and does not create significant drag.  

Turbulent flow is far more common but still  very little is known about how to predict its  

behaviour. It is very difficult to control because  of the formation of small vortices called eddies  

in the flow, making the flow highly erratic.  Turbulent flow occurs at higher flow velocities  

and causes a significant increase in drag.  At cruising speeds of 80-85% of the speed  

of sound , turbulent flow is ultimately  unavoidable, but we can work to minimize it. 

Boeing has developed a technology that helps them  delay and control the formation of turbulent flow  

called Hybrid Laminar Flow Control. Details on  their implementation of the technology are sparse;  

this technology is capable of reducing  fuel burn by as much as 30% [18], and so  

companies are keeping their research extremely  secretive to keep their competitive advantage. 

Here’s what we know. In the late 80s and early  90s NASA and Boeing began investigating a suction  

system on the 757 that would draw in boundary  layer air, that is the layer of very slow moving  

air that clings to the surface of moving objects.  It looked something like this [19]. The outside  

skin of the surface was permeable to air through  tiny perforations, too small for the naked eye to  

see. Manufacturing the permeable surface, while  also keeping the tiny holes clear of debris is  

one of the many challenges with this technology.  The outer and inner skin were then attached to an  

elaborate plumbing system that was connected to  a turbopump which sucked air from the boundary  

layer of air that would form along the plane’s  surface. By doing this they could drastically  

delay and reduce the size of the turbulent  flow, and in turn reduce the drag on the plane.  

There is no space for this ducting system inside  the wings of the 787, but from what we do know it  

is inside both the horizontal and vertical tails,  however the only clue of their presence are these  

little doors, who’s purpose are a mystery to me  with little to no information available online,  

a testament to how advanced this plane is. [20] Composites give plenty of advantages,  

but it does come with some disadvantages. When we examine the plane’s composition. One  

material jumps out at me. 15% of this plane  is titanium, that’s much higher than normal.  

Titanium is an expensive material, so they must  have had a good reason to use it over aluminium. 

Aluminium is typically corrosion resistant when  left on it’s own, but when it is placed in direct  

contact with carbon fibre composites, something  strange happens. The aluminium begins to corrode  

incredibly quickly. Something about carbon fibre  causes aluminium to oxidize and fall apart.  

Carbon fibre is like aluminiums kryptonite. [21] This phenomenon is called galvanic corrosion, and  

it happens when two materials that have dissimilar  electric potentials or nobilities are placed in  

contact with an electrolyte, like salt water.  [22] If we take a look at the galvanic series,  

which quantifies materials nobilities, we can see  that graphite is very noble, on the far end of the  

left scale, while aluminium is quite far to the  right. [23]When this occurs an electric potential  

forms between the two materials that causes the  two materials to trade electrons and ions, which  

results in the anode being eaten away. This effect  is made even worse when the surface area of the  

more noble material, the cathode, is very large in  comparison to the less noble material, the anode.  

Say for example, when carbon fibre components  are fastened together using aluminium fasteners. 

To avoid this corrosion the engineers  needed to pick a material closer to  

carbon in the galvanic series, and the  closest suitable metal was titanium. 

This has been a huge source of cost in  manufacturing, Boeing’s production cost was higher  

than it’s sales price for quite some time. Meaning  they were making a loss on each aircraft sold. 

This is fairly typical for new airliners,  as R&D and manufacturing tooling costs  

take time to recoup and companies like Boeing  typically spread these costs over a period of  

time on each plane,instead of just having a  massive negative balance sheet in one year,  

but because the 787 was so radically new, these  sunk developments costs, called deferred costs  

were expected to reach 25 billion before Boeing  even reached a breakeven point on each plane  

sold. Where the cost of manufacturing equaled  the sales price. In comparison the Boeing 777  

reached 3.7 billion [24] To recoup costs as fast  as possible it was essential that Boeing reduced  

the cost of production, and high on their list was  the elimination of titanium parts where possible. 

The frame around the cockpit windows for example  were initially made out of titanium, but were  

changed to aluminium with a special coating to  prevent corrosion. While some parts that were  

originally titanium were changed to composites  like door frames. [25] Other improvements were  

sought to make the manufacturing process for  titanium less costly. Many metallic parts used  

on aircraft start off as large blocks of metal  that have been machined down into their final  

shape. This results in a tonne of wasted metal  as the metal is gradually shaved away. Aircraft  

manufacturers quantify this wastage with something  called a buy to fly ratio, and it’s a huge source  

of increased manufacturing costs. One Boeing  has tackled this is by collaborating with Norsk  

Titanium, a titanium 3D printing company.[26] Now making 3D printing metal parts is not easy.  

Most titanium 3D printing involves a powdered  titanium that is melted together using lasers.  

Researchers used special high speed x-ray imaging  to visualize what happens during this process  

and found a lot of imperfections.  The track varies in height,  

the powder gets blasted away resulting in varying  thickness and separated tracks that coalesce and  

even bubbles causing pores in the metal. This  creates parts with a lot of micro-imperfects  

and imperfections that lead to decreased  life as fatigue causes cracks to form. 

We can visualise a material's fatigue  strength by plotting on a S-N curve,  

which places the magnitude of the alternating  stress on the Y-axis and the number of cycles  

it survived on the x-axis. For traditional  machined titanium it looks something like this,  

whereas for 3D printed parts it looks like this.  [27] 3D printed parts simply fail much sooner  

because of these tiny imperfections. Norsk has  worked to improve this. Instead of using laser  

sintering with powder, Norsk have developed a  revolutionizing patented wire based metallic  

3D printing system for titanium that they  monitor with 600 frames per second cameras  

for quality control. These 3D printed parts are  then machined down into the final shape, reducing  

the total titanium used by 25-50%, and their  printing method is 50 to 100 times faster than the  

powdered printing method. This process resulted  in the first ever FAA certified 3D printed  

structural components and they first flew in the  Boeing 787.[26] This plane truly is innovative. 

Titanium was not the only  material Boeing worked on removing  

from the plane's construction to save on cost. Copper once formed an important part of the 787s  

wing, where it was laid down in thin strips on  the wing's surface. This is not a typical design  

choice for aircraft wings, and once again it was  influenced by the 787s composite construction,  

because composite materials  are not good conductors. 

Carbon fibres are great conductors, but  problems arise because of the plastic resin  

binding them together, as this resin is  an insulating material, preventing the  

passage of electricity. [28] Animation 15a Which is a massive problem for planes,  

as getting hit by lightning is not a  rare occurrence. One study calculated  

that lightning strikes occurred once every  3000 hours of flying between 1950 and 1975. 

A 787 was struck by lightning while taking  off from Heathrow. Upon landing in India,  

42-46 holes were found in the fuselage as a  result of resistive heating. [29] The plane  

survived and was flown back to London  for repairs with no passengers aboard,  

but composite’s vulnerability to this kind  of damage is a drawback and the repair  

process is more complicated than with aluminium. However, this strike could have been much worse,  

if the electricity does not smoothly run along  the surface of the plane and exit, it may cause  

a spark in the fuel tanks and cause an explosion. This kind of accident was not uncommon in  

the early days of the airline industry. Like Pan Am Flight 214, which was struck  

by lightning while it flew in a holding  pattern waiting for a lightning storm to  

pass at Philadelphia International Airport  in 1967. It’s left wing fuel tank exploded,  

causing the plane to barrel out of control  to the ground in flames. [30] Since then the  

aviation sector has implemented rigorous safety  measures and lightning protection tests to ensure  

an accident like this could never happen again. Early 787 wings were designed with copper strips  

to ensure the electrons had a path of low  resistance along the surface of the wing,  

ensuring they wouldn’t travel to  the fuel tank and cause a spark,  

while also preventing resistive heating damage  to the composite structure. Fasteners were sealed  

with an insulating material to stop electricity  from travelling down the metallic fastener into  

the fuel tank, and the fasteners themselves  were fitted with compression rings and a sealant  

to eliminate potential spark locations caused  by gaps and sharp edges. Finally the 787 has a  

nitrogen inerting system that fills the tank with  nitrogen; ignition can’t happen without oxygen. 

Boeing has since removed two of these  protections in a cost saving measure,  

removing the copper mesh and insulating caps, which drew concern and criticism, but Boeing  

argues that between the nitrogen inerting  system and the other safety measures,  

these expensive features were not needed. [31] Where composites couldn’t be used,  

other materials were chosen. The leading  edges of the wing and tail, the tail-cone,  

and parts of the engine cowling, were all made  from aluminium or other metals [5]. The leading  

edges of the plane needed aluminium because of  the composites' poor impact resistance. While  

composites have extremely high strength, they can  be brittle on sudden impacts such as bird strikes,  

which most commonly happen at the leading  edges of the wing or on the engines.  

Metals are able to deform on impact with a reduced  chance of fracture, instead of shattering as  

composites would (Visual [4]). Aluminum leading  edges were also beneficial for the purpose of  

de-icing because they are good thermal conductors. If you have ever flown on a very cold day you  

may have seen a truck spray fluid onto the  wings of the plane. This is de-icing fluid.  

A heated mixture of glycol and water. It’s  needed because most planes aren’t capable  

of de-icing themselves on the ground. The  787 can be, when fed with external power,  

because it uses a new type of de-icing system. The 787 uses electrically heated blankets bonded  

to the surface of the slats [32] , which are  able to heat the surface of the wing and melt  

or prevent any ice formation on the leading edge  of the wing. Traditionally, ice is prevented by  

extracting hot bleed-air from the engine and  piping it to vulnerable areas such as the  

leading edge of the wing where ice build up could  severely interfere with the wing's operation.  

This draws valuable energy away from the  engines and increases fuel consumption,  

while also requiring a complicated network  of tubing and exhausts which adds weight  

and increases complexity of  construction and maintenance. 

The electric heating system is twice as  efficient as the extracted bleed air system,  

as no excess energy is lost through venting  air to the atmosphere, and it also reduces  

drag as the exhaust holes for the bleed air  on the lower side of the wing create drag.[33] 

The 787 is actually the first commercial airliner  that has eliminated this bleed air system,  

which was a huge technical challenge and  required a complete redesign of several systems,  

and an entirely new engine. In our next video we  are going to explore the incredible engineering  

behind the power systems of the 787, exploring  the advancements in the jet engine and the overall  

system architecture that allowed the 787 to become  the most efficient long range airliner ever made. 

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