Dwarfs on the Shoulders of Giants

Every cockpit carries a document that most passengers never see and few people outside aviation fully appreciate. It is laminated, usually, or bound in a bright-colored quick-reference format. It contains no prose, no argument, no explanation. It is a list of items and their required states: checked, set, on, off, verified, confirmed.

It is the checklist. And it is the most conservative document in aviation.

I don't mean conservative in the partisan political sense. I mean conservative in the philosophical sense that Edmund Burke would have recognized: a reverence for accumulated wisdom, a distrust of individual improvisation in high-stakes situations, and a humility before the knowledge of those who came before.

Every item on every checklist exists because someone, somewhere, at some time, learned — often at terrible cost — that the item mattered. The checklist is not a collection of bureaucratic formalities imposed by regulators who have never flown. It is a codification of hard lessons. It represents what the dead have taught us, organized so that the living don't have to learn it again.

The Problem Checklists Solve

The aviation industry discovered the necessity of checklists in October 1935, when a Boeing Model 299 — the prototype of what would become the B-17 Flying Fortress — crashed on takeoff at Wright Field in Dayton, Ohio. The crash killed the pilot, Major Ployer Hill, and was attributed to "pilot error." But the error was not incompetence. Major Hill was one of the Army Air Corps' most experienced pilots.

The error was that the aircraft had grown too complex for any pilot to reliably remember everything that needed to be done. The Model 299 was larger, more powerful, and more complicated than anything Hill had flown before. Among the items that needed attention before takeoff were the elevator and rudder locks — which kept the control surfaces from flapping in the wind while the aircraft was parked. Hill taxied out and applied power without removing them.

The locks were not forgotten because Hill was careless. They were forgotten because the human brain, under the task-loading of preparing a complex aircraft for flight, had reached the limit of what unaided memory could reliably manage.

The Army's response was to develop a checklist. The B-17 went on to fly nearly thirteen thousand aircraft over the course of World War II. It became the backbone of the American strategic bombing campaign in Europe. Its crews flew it into conditions that should have destroyed them, and many of them came home.

The checklist was not a constraint on their airmanship. It was the foundation that made their airmanship possible.

Codified Wisdom

Burke wrote that society is a partnership between the dead, the living, and the yet to be born. The checklist is a perfect operational expression of this idea.

The pilot who runs the checklist before engine start is, in a very real sense, in conversation with every pilot who has ever operated that aircraft type. The items on the list were placed there because their omission, at some point, caused a problem serious enough to be investigated, documented, and codified. Each check is a small memorial to a lesson that cost someone something.

Some of those lessons cost very little — a write-up in a maintenance log, a discrepancy report, a close call that nobody was hurt by. Some of them cost everything.

The checklist doesn't distinguish between these. Every item is equally mandatory, because the pilot running the checklist doesn't always know which one, skipped today, will be the one that mattered.

Bernard of Chartres, the twelfth-century philosopher, described his own era's intellectual situation with a phrase that Newton later made famous: we are dwarfs on the shoulders of giants. We see further than our predecessors not because our vision is keener, but because we are elevated by their achievement. The checklist is aviation's implementation of this principle. The crew who runs it faithfully are dwarfs elevated by giants — pilots of modest experience accessing the accumulated wisdom of thousands of flights, thousands of investigations, and thousands of pilots who learned things they did not expect to learn.

The Temptation of Improvisation

The checklist's greatest enemy is not complacency — though complacency is real. Its greatest enemy is expertise.

The experienced pilot who knows the aircraft well, who has run the before-takeoff checklist hundreds of times, who can rattle off the items from memory — this pilot is at greater risk of checklist failure than the student who is still learning the sequence. The expert is tempted to flow the checklist from memory rather than reading it, to skip items he knows are not applicable, to complete steps out of sequence when the operational situation makes the normal flow awkward.

These shortcuts usually don't matter. The items he skips are indeed not applicable today. The sequence he alters still gets everything done. And the shortcuts save time, which matters in a busy operation.

But the checklist's value is precisely in its immunity to this kind of expert judgment. The whole point is that the pilot doesn't decide which items matter today. The list decides. The pilot's job is to verify, not to evaluate.

Burke made the same argument about inherited institutions. The intellectual who dismisses tradition because he cannot immediately articulate its rationale is making the expert's mistake. Just as the pilot who skips the checklist item he can't see the immediate purpose of, the intellectual clearing away institutional forms he doesn't personally understand may be removing a defense whose purpose he has simply never encountered.

The checklist item that seems pointless has usually never seemed pointless to the person who put it there.

A Partnership with the Dead

I have run checklists in aircraft ranging from light Cessnas to wide-body jets. The form changes. The length changes. The specific items change. The principle is always the same.

Before I start an engine, I am in conversation with the engineers who designed the engine start sequence, the test pilots who discovered what happened when you deviated from it, and the accident investigators who documented the consequences of the deviations that mattered. Before I taxi, I am in conversation with every pilot who ever taxied without checking the flight controls and discovered, at the worst possible moment, that something was not connected. Before I apply takeoff power, I am in conversation with Major Ployer Hill.

This is not a burden. It is a privilege.

The checklist is what makes it possible for a pilot of my experience to operate aircraft of extraordinary complexity with a safety record that would have seemed miraculous to the pioneers of flight. It is the accumulated knowledge of everyone who came before, organized into a form that requires only the discipline to use it.

Burke understood that civilization is not the achievement of any single generation, but the cumulative product of countless generations of experiment, failure, learning, and refinement. The living inherit something from the dead, and have obligations to those who come after.

The checklist is aviation's small enactment of this principle.

Run it. Every time. All the way through.

The giants didn't write it for you to skip.