Sunday, May 26, 2013


Yesterday was cockpit organization, today it's another science and art of flying: Checklists.

Lately, I've been thinking about the methods airlines and corporate-flying use regarding checklists, and applying it to the general aviation world. I've read and been told that airlines use the "challenge-response" method for normal procedures, and the "call-do-response" for abnormal/emergency procedures.

What do they mean?

The "challenge-response" (do and verify) method includes a flow pattern of memorized items from Standard Operating Procedures to configure the airplane for a particular segment of the flight. After the flow, the pilot verifies the most important items, for that segment, have been done by using a checklist. In a multi-crew scenario, the pilot-monitoring performs the flows and reads the items of the checklist. The pilot-flying then responds verbally and by visually checking that item in the cockpit. The checklist doesn't have the same items of the flow, but only the most important ones. Also called "killer-items". Basically perform the actions by memory and verify the important items with a checklist.

The "call-do-response" (read and do) method is the one where the pilot reads an item from the checklist and performs an action. Or in the multi-crew scenario, the PM reads the item, and the PF responds verbally and performs the action. This method doesn't require the pilot to memorize the items, since every item (action) is included in the checklist. So, basically read the item and perform an action. It's also the method the majority of light airplane manufacturers establish in their manuals.

Both sound pretty good, don't they?

In this post I'll analyze which one is more efficient for a typical small airplane flight. That includes: which one is better for normal operations (and the specific flight segments), abnormal, and emergency procedures, which one's better for single-pilot and multi-crew operations (instructor and student, or pilot-flying and pilot-monitoring, for example), and then conclude with a system that allows for better efficiency and safety.

Here's a list of the typical normal flight segments:

Pre-flight (interior and exterior check of the airplane)
Pre-engine start (cockpit organization and departure briefing)
Engine start
After engine start
Before taxi
Taxi (instrument cross-check and verification)
Before takeoff (ground checks, engine run-up and takeoff briefing)
Takeoff (normal, short-field and soft-field)
Cruise (cruise and arrival briefings)
Landing (normal, short-field and soft-field)
After landing
Shut-down and securing

This is a list of the abnormalities, followed by the emergencies:

Electrical failure
Alternator failure
Insecure door
Radio failure

Engine failure on takeoff roll
Engine failure after liftoff
Engine failure in flight
Engine fire on ground
Engine fire in flight
Fire in airplane
Emergency descent
Emergency landing

The objective is to decide what method to use for each segment and abnormality/emergency. Some recommend using the "call-do-response" method for the segments on the ground and using the "challenge-response" method in the air. I would say the "challenge-response" method can be used for everything! The issue with that is the flight manuals always come with the "call-do-response" type and you would have to develop a kind of SOP with flows and a checklist for that airplane.
A NASA study shows the "challenge-response" method is safer and more efficient, because you might jump an item from the "call-do" checklist after getting distracted. Commercial aviation is safer than general aviation. That leads us to the conclusion that since airlines use the "challenge-response" method, it would be wise to use it in your Piper or Cessna.
The problem I see with this is that airlines always operate as multi-crew, so the PF can fly the airplane and the PM goes throught the abnormal/emergency procedures using the "call-do-response" method. As a single-pilot, there might not be enough time to perform all of those actions while reading the checklist, so it's better to use the "challenge-response" method.

With that said, I'd say the kind of method used begins with the type of airplane and whether the flight will be performed as single-pilot or multi-crew. If the airplane requires a multi-crew for its operation, then the "challenge-response" method can be used for normal procedures and the "call-do-response" for abnormal/emergency procedures.
If the airplane can be flown as single-pilot and in the case it's a dual flight, or a safety pilot is required, then the "challenge-response" method is recommended for every normal, abnormal or emergency procedure. The thing with flying as single-pilot is all the tasks are performed by only one person and the tasks can't be shared, so it becomes much more critical to perform all those procedures from memory and then verify the important items with a checklist containing no more than five or six items.

So, what's now to be done is a flow checklist in form of SOPs for the airplanes you're going to fly, and a checklist to be used in the airplane to verify the important items have been done. This is much more complicated and requires memorization of procedures and flows.

Maybe that's why the "call-do-response" method is more attractive for the average airplane owner and/or flight school, but it isn't necessarily safer nor more efficient.

As I've said before, it's also a good subject to talk about in the hangar.

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