Join William Lidwell for an in-depth discussion in this video Flexibility Trade-Offs, part of Universal Principles of Design.
- Hi, I'm William Lidwell and this is Universal Principles of Design. In this movie Flexibility Tradeoffs Why the jack of all trades is master of none. The F-35 joint strike fighter was conceived in the late 1990s to replace the Air Force's F-16, the A-10, the Navy's F/A-18, and the Marine's Harrier. Now if you're not familiar with these planes, that's okay.
The point is that the performance requirements for these aircraft are very different and many are in conflict with one another. For example, the optimal design for a high-altitude aircraft where the air is thin has large wings to make turns quickly. Whereas the optimal design for low-altitude aircraft where the air is thick, has small wings, reducing drag and making a small target. Take off and landing from an aircraft carrier requires a rugged and heavy airframe, a lot of extra weight that's not required by a plane that lands on a runway.
And vertical takeoff and landing is a whole thing by itself. It means that being able to take off and land like a helicopter and then fly like a normal jet. Imagine the increased complexity of piloting such a craft much less a combination of all four crafts. So how is the F-35 fared? The original estimated cost for an F-35 in 2001 was about $70 million per plane. Today, one F-35A, the Air Force's version, costs $148 million.
One F-35B, the Marine Corps version, costs $251 million. And one F-35C, the Navy version, costs a whopping $337 million. And the costs are still rising. The plane is riddled with bugs, performance problems, and usability problems. One critic summarized the situation like this. "The F-35 can't turn, can't climb, can't run. "It is by an objective measure, a failed design." There is great appeal to the idea that you can design something flexibly to perform many different functions, at less cost, and at a greater level of performance than more specialized designs.
It is the siren song of design. But unless existing specialized designs are just terribly inefficient, this idea is always wrong and flexibility tradeoffs are the reason why. So what are flexibility tradeoffs? Stated simply, as the flexibility of a design increases, the usability and performances of the design decreases. This is not some platitude. It is like a law of nature, like gravity or the speed of light.
In fact we could easily justify calling this principle the law of flexibility tradeoffs. Here's why. Flexibility entails satisfying a larger set of requirements which often conflict with one another. Which means compromises and complexity in the design. And compromises and complexity increase cost and decrease performance and usability. For example, the Swiss army knife has many tools that increase its flexibility. But the tools are less efficient and less usable than their standalone equivalents.
Performance and usability are traded for flexibility. When the value of flexibility outweighs these tradeoffs, as with the Swiss army knife, then it's worth it. So when are flexibility tradeoffs justified? You can use this five question test. 1. Is suboptimal good enough? 2. Is the performance environment stable, meaning does it stay the same over time? 3. Are performance and user requirements similar? 4. Can functions be modularized in the design? and 5. Does the value of flexibility justify the performance tradeoffs? If the answer to any of these questions is No, with the F-35 for example, we get five Nos.
The flexibility tradeoffs are going to be costly and the probability of failure high. If however the answer to all of these questions is Yes, then flexibility tradeoffs may be justified, meaning there is an opportunity for one general-purpose design to be successful. A good example of this is Smartphones which merge telephones and cameras. This merging works because the phones and cameras are good enough quality for most people, the performance environment is fairly stable, the user requirements for cameras and phones are similar, they're portable, handheld and they store information.
The electronics can be modularized, and having both functions integrated into one device is valuable. So whether you use your understanding of flexibility tradeoffs to make better strategic design decisions, to know when to combine or separate design specifications, or to avert disastrous procurement decisions remember the idiom, "jack of all trades, master of none" is not just true, it's the law.