Take Off Clearance Switch

There are many steps involved with getting a commercial airliner into the air. As such, procedures have been implemented over the years to do this as safely as possible. One critical step in this process is to ensure that an aircraft is permitted by air traffic control to actually do the taking off from any given runway*. This is crucial since hurtling a jet full of fuel down a runway that has another jet full of fuel landing/crossing said runway makes a large and expensive mess. To stop this happening, clearance from ATC to take off is part of the take off checklist, which contains all the necessary steps. Except it doesn't always work.

Recently, I'll link it when I find it again, there was an incident where a regional jet was cleared to hold (not take off) and started the take off roll anyway. As they crested a rise in the runway the vertical stabilizer of a Boeing 777 came into view. Erring on the side of caution/employment, the crew aborted the take off. Seconds after, they then received clearance, the 777 was essentially finished crossing by this point.

The problems here were some expectation bias, but also because the process of getting clearance is essentially verbal via the radio, and passing that point on the checklist relies entirely on one/both crew remembering if they heard that clearance. This is where the expectation bias can creep in. If you do the same trip 100x, and you hear clearance to hold at the end of the runway then almost immediately clearance to take off, you may think you heard the second part just because 100x before, you did.

The problem being, there's no visual reference like you get with nearly every other checklist item. Other items, such as the strobe light that should be on before take off, you can check by looking at the switch. So why not make clearance the same?

In this way, while making the radio call to obtain take off clearance, your finger can be on the switch... as you hear it, you flick the switch. Both pilots now have visual reference as to whether this has happened. But, we can do more than this. If this switch were linked into the avionics, in the "no" position, several safety interlocks might be added, for example, engine thrust might be limited to 30%** to prevent un-cleared take off rolls.

Even better, a light as visual reference would be useful for all in range. The best situation would be for the aircraft to transmit the status to ATC to highlight any disagree status with the controller.

*A runway is preferable. It's considered poor form to be landing on a taxi way, Harrison. ** Or whatever max reasonable taxi thrust might be for the type, for a Cessna 172 in mud, that might be 127%.