During my pilot ground school, I always draw a diagram like the one above as we start to discuss regulations. I do this to reinforce the concept that being safe is not necessarily the same as being legal and being legal is not always the same as being safe. As pilots, we are likely to have a longer flying career if we restrict ourselves to operations that meet both criteria and stay away from the edges.
The concept that safe and legal have some overlap but not a complete overlap is often a little surprising to aspiring pilots. They seem to think the regulations are designed to make us safe.
In many aviation regulations, pilots are given incredible flexibility. I like to call this “rope” – you can use rope to get yourself out of a hole or you can use it to hang yourself – which happens is completely up to how you use it.
The regulations allow a brand new pilot to operate near a 14,000′ mountain in class G airspace, close to the ground with only 1 mile of visibility and flying right near the edge of clouds. This is a case on the very edge of legal, but about as far from safe as you can get.
Pilots need to match their flying to their airplane’s capabilities, their skills, and their own level of experience. This is where the concept of personal minimums comes into play – even very experienced pilots will add margins to what is legal to do in order to stay safe.
On the other side of diagram, one day after the annual inspection expires on an airplane, it is illegal to fly. There’s rarely anything that has happened in that day to make the airplane unsafe, but flying it would put your license unnecessarily at risk. Don’t do it.
Some regulations are designed to give pilots a margin of safety. For example, 91.151 requires pilots to have at least 30 minutes more fuel than is required for their flight in daytime VFR conditions. That’s the legal requirement, but most pilots I know consider 1 hour of fuel margin a minimum. Depending on weather, route, airplane familiarity, and many other factors, even 1 hour may be insufficient.
Margins are great, but only if we actually have them. The accident chain is often started by a pilot who intentionally eliminates margins (because, hey – it’s legal!) and then eliminates any remaining margins unintentionally (though predictably). The accident record is littered with examples of pilots who precisely calculated weight and balance and takeoff distance and fuel requirements, who end up off the end of the runway or short of their destination because their measurement of fuel, passengers, and baggage was much less precise than their calculations or whose fuel management, procedures, or aircraft handling took them outside of the remaining margin with predictable results.
Many of the margins we deal with are cliff edges that are hard or even impossible to see – the cautious pilot surveys the cliff from several angles, walks cautiously near the edge, checks the solidity of the ground, and keeps a respectful distance from the edge to enjoy the view. The bold pilot runs forward to exactly the visible edge, failing to account for the crumbly cliff and his forward momentum and curses the fickle earth on his way down to the chasm.
Keep your margins large, consider how you have consumed them intentionally and how you might be consuming them unintentionally and have a long, happy flying career.