The 737

Imagine you took a VW Beetle, like this:

The best known beetles date from 1970 or so. Let’s say we want to take this standard old Beetle and make it better.

What we’re going to do is take twice as many people, so we want 8 seats not 4. We’re going to double the power of the engine. We’re going to make it drive twice as far on the same tank of fuel. This all sounds pretty great.

Is it still a Beetle? No, it’s not.

It’s now a VW Bus. Or it’s a modern VW Beetle. Or it’s something else. But it’s not a VW Bug any more.

It would be like calling a banana an apple because they’re both about the same size and they’re both fruit.

Old and busted turbojet.

And yet that’s what we did with the 737, which also happens to date from 1970 or so. If you look at the 737 specs you can see that from the original 737-100 in 1968 to the 737 MAX 8 we:

  • ~Doubled the passengers from 85 to 162
  • ~Doubled the range from 1,500 to 3,300 miles
  • ~Doubled the cargo capacity from 650 cubic feet to over 1,500
  • ~Doubled the thrust from ~14,000 to ~29,300 pound-feet
  • Added about 30% more wing area

Practically everything has changed apart from the fuselage cross-section and the name.

New hotness turbofan-winglets-with-inflight-wifi.

Systems aren’t optimizable by breaking them down and optimizing the sub-components all by themselves. If you take the VW Beetle and drop in an engine that’s twice as good on every metric is has impacts across the system we call a “Beetle”. The heavier engine needs more structure to support it. The load it puts on the transmission is higher so you need a better transmission. The transmission now may need higher quality oil. And on and on. The effects ripple through the system.

We (or rather, Boeing has) have been incrementally improving the 737 for 50 years. As so often happens, we’ve been making a bad thing better, dramatically better it must be said, rather than making something good.

Aircraft are systems too and there’s a complex interplay between all the parts. That’s why superficially a 777 might look like a really big 737 but really they’re completely different animals with their own characteristics, designed for different things.

Hammond hates inspections. They slow everything down.

Jurassic Park

So why isn’t there a new thing? Why still the 737?

The regulatory environment deems it so. It’s vastly easier to make an incremental change to a validated airframe than to make a new one. A new one requires certifying everything and retraining everyone in the system. Pilots, crew, maintenance, gate handlers. Everyone gets new training and it’s all expensive and takes time.

The military doesn’t buy weapons, they buy weapon systems. There’s people, processes and vast infrastructure to field a weapon on the other side of the planet. It’s those systems that make it all expensive and complicated.

Boeing has been reasonably optimizing a system for 50 years and it finally “broke”. As Taleb would say, it got fragile.

It’s arguable it isn’t broken at all. It’s arguable it broke a while ago. Whatever.

Either way, it’s not entirely their fault. We made it approximately impossible to make a new type of plane unless you’re Boeing. And even then we made it devilishly difficult. So they did what we asked of them and made existing designs more and more efficient until suddenly it wasn’t.

The actual details of the two MAX crashes, ET302 an JT610 are going to be fascinating to read in 2-5 years when the investigations are all settled. Maybe it was the MCAS, maybe it wasn’t.

Either way, eventually the optimizations would run out and the system would break somehow, due to some thing or other.

My bet is Boeing will be fine, because:

  • They did what we asked them to do
  • Airbus is no better
  • The airlines involved are far away and constrained in various ways
  • The pilots are dead, so we can easily blame them

More training will be designed and implemented. Maybe there will be other systems changes like software updates. Boeing will recover unless a well-funded domestic airline loses an aircraft.

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