The recent scary engine fire aboard United flight 328 reminded me that a lot of our transportation infrastructure depends greatly upon clear, easy-to-read technical documentation–specifically, checklists. Today I’ll walk through some helpful guidelines for pilot checklists…or any checklist, for that matter.
When Your Writing is Literally a Matter of Life or Death
Aircraft–from commercial airliners and fighter jets to single-engine private planes–are complex machines that require a lot of concentration and procedures to operate safely. Unlike a microwave oven or DVD player, airplanes are not machines that people could or should just wing it (so to speak) when following procedures. Each model of plane is different and each one has its own particular processes for operating safely. It is not considered shameful to run through the checklist before performing a given function. Indeed, it’s been found to be necessary. As I’ve learned from watching too many episodes of Air Disasters, if pilots skip a step by trying to do things from memory, they can put themselves into a situation that gets them and their passengers killed. Running through the checklist is an integral part of safely operating the aircraft.
Commercial aircraft checklists make a few assumptions:
- There is both a pilot and first officer in the cockpit.
- Both pilot and first officer are alive, awake, and able to perform their piloting functions.
- The situation covered by the checklist allows enough time for the pilot and first officer to retrieve, read, and act upon the checklist.
- The pilots will engage in a challenge-and-response behavior where each checklist item is called for, acted upon, and responded to verbally.
Pilot 1: “Set flaps to 30.”
Pilot 2: Sets flaps, then says aloud, “Flaps set to 30,” confirming what has been done.
On commercial aircraft, checklists come in multiple forms, beyond the typical three-ring-binder paper format. Some aircraft, for example, have their primary function switches laid out in physical columns somewhere on the control panel. Others have vocal checklists programmed by the aircraft manufacturer that prompt the pilots verbally. Others have computer-aided checklists built into the aircraft or available on computer tablets.
The Air Transport Association of America, now Airlines for America, advocates the following philosophy when it comes to developing checklists:
Checklists should contain, in abbreviated form, all the information required by the trained flight crew to operate the airplane in most normal and non-normal situations. Normal check- lists should be organized by segments of flight. The checklist should contain the minimum cues required for the trained crew-member to verify that the appropriate actions have been completed. Only procedural steps which, if omitted have direct and adverse impact on normal operations, are included. Items annunciated by crew alerting systems are not included.
Also, a NASA report points out that checklists serve the following functions.
- Act as memory guide.
- Ensure that all critical actions are taken.
- Reduce variability between pilots.
- Enhance coordination during high workload and stressful conditions.
Writing Checklists Well
To reduce the potential for danger, people in the industry recommend:
- Restricting vocabulary size.
- Increasing sequential constraints between items (i.e., giving the pilot enough time to perform an action before moving on to the next).
- Employing frequently used words.
- Avoiding ambiguity (i.e., being specific about which instrument is being read or control is being activated).
- Grouping/chunking the items related to a specific task (e.g., starting the engines).
- Separating these chunks on the screen or on the printed page.
- Sequencing tasks in the order they must be performed.
- Ordering tasks by control geography. To some extent, this is a function of the cockpit layout, but if you have to set controls on multiple panels, you should cover all of the actions in a specific area of the control panel before moving on to the next one.
- Making the cockpit actions logical and consistent (i.e., having the pilot employ “muscle memory” by operating the controls across specific panels in a consistent order). This is especially important in an emergency, where easy, quick, and reflexive action is needed.
- Sequencing tasks in a way that allows the crew time to perform the activity without rushing.
If you’re in a position to be writing checklists, following the guidelines recommended for airline pilots is a good start because they are used thousands of times a day and are a critical safety function of commercial air travel. Even if lives aren’t depending on your procedures, you can at least make them as user-friendly as possible by following guidelines that pilots depend upon when lives are on the line.
As an extra “bonus” item, I highly recommend Captain Joe’s video explanation of how checklists were likely used to avoid a catastrophe in the United Flight 328 incident. Happy writing!