“Aviation in itself is not inherently dangerous. But to an even greater degree
than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.”

— Captain A. G. Lamplugh

In the world of aviation, people tend to worry about failures. After all, when things go wrong in the air, the outcomes can be severe. When you think of a system failing, what comes to mind? For many, the first thought is of the engine quitting. Maybe you think about fire or electrical failure. But the system that proves most likely to fail time and time again is the human system – the pilot. That doesn’t mean that there is something wrong with the pilot population, or that the training is flawed, although we can all stand to be constantly learning and improving. It does mean that as humans, we are inherently fallible. But by reinforcing the links in the human chain that we know tend to break, we can expect to get a chain that is less likely to break. One way to do this is to follow the concept of “trust but verify.” Originally a Russian proverb adopted by President Reagan in his foreign relations, the aviation world has a lot to benefit from it as well. Here are a few times that I’ve found it’s good to trust but verify.

 

Instrument Indications
Visual references are vital in aviation, from basic flight visibility to being able to see the horizon. Even in instrument flying, all of that hard work flying without visual reference in the clouds comes down to the end where you must spot the runway environment visually. As important as the visual element is, we as humans are riddled with quirks of the senses that cause all sorts of problems. Illusions and misperceptions of both the eyes and the mind have sealed the fate of many pilots who trusted their senses in flight. Instead, we are told to trust our instruments. But wait, don’t instruments fail? Sure, they can break like anything else. Pitot-static failures, gyroscopic failures, and vacuum pump failures are just a start. This is why we trust our instruments – but we verify them. The instruments work together in harmony to create a big picture of the flight. Learning to spot the failure of an instrument begins with trusting its indication, but verifying it with another instrument. For instance, if the attitude indicator begins to show a bank, does that match the indication of the miniature airplane in the turn coordinator or are the wings still level? Is the heading changing on the heading indicator? If not, there might be a failure on the horizon. The artificial horizon. See what I did there?

Cessna 172 Attitude Indicator

Some instruments have an indicator to show whenever it fails like this “gyro” flag on the attitude indicator, but it’s still best to compare readings to other instruments for context clues.

 

Calculations
Another good time to trust but verify is when making calculations. Let’s say you’re planning a cross country flight and filling the boxes of your flight log. I know, that’s old school, but stay with me, kids. You’ve carefully measured out distances and are working out the leg times and fuel burn for each leg. You trust the process of your calculations, whether you are using a manual E6B or a calculator. The problem is that one missed key punch or a misalignment on the E6B can throw your numbers off significantly. There are a couple ways to verify your data. First, run it past the filter of “does this make sense?” If you have a flight of 100 miles and calculate that you’ll burn 30 gallons of fuel, does that generally make sense for your airplane? In a Cessna 172, that sounds to me like a big ol’ hole in the gas tank. After determining that it makes sense, you might simply try calculating a second time. Take the example of adding up total hours for a page in my logbook. If I come up with the same total twice in a row, then I’m probably adding correctly. Finally, consider using a backup source. If you are using a manual E6B for your trip calculations, perhaps you double check your work by plugging your route into a program like Foreflight or using an electronic E6B. Comparing the results from two different sources can spot a problem on the ground before it becomes a real problem in the air.

Old School Paper Flight Log

This is the flight log from my first long solo cross country flight.  There is lots of room for error in calculations without a second method to verify it.

 

Configuring Technology
Technology is a wonderful thing. However, in the same way that calculations can be off if you blindly trust it, so it is with the onboard technology. Let’s say you’ve selected your destination airport or waypoint in the GPS and start to follow the magenta line. You might trust the technology and feel good about the procedure you used to enter it, but what if you are navigating to the wrong place? Did you just hit enter through the confirmation screen or did you genuinely verify it? I find that speaking selections out loud is a great way to verify. Pointing and saying “I have selected KAHN as my destination” will surely catch that one letter off that’s taking you the opposite direction. Good situational awareness is also of value here. By knowing the general direction you should be heading along with the general distance, you can effectively apply that “does this make sense?” filter here as well, instead of blindly trusting the magenta line.

Cessna 172 GPS

It may be fairly easy to follow the magenta line, but are you completely certain where it is leading you?

 

Crew Resource Management
Flying with another pilot or even a knowledgeable passenger can serve more than just good company. Having a culture of open communication and verification can greatly limit the chances of the human system failing. Professional pilots have extensive crew resource management training for this reason. Take the example above of configuring your GPS unit. After plugging in your destination airport and any waypoints, having a second pair of eyes on the configuration might catch that you missed a waypoint, or that you have the wrong navigation frequency tuned in.

This concept is independent of title or experience level. Copilots have watched their captain fly themselves into calamity because they blindly trusted the actions of their much more experienced captain instead of speaking up. I recently rode in the back seat of a training flight. The student and instructor were working on instrument approaches. I saw an airplane in the distance that was heading our direction. I wasn’t sure if the instructor saw it, so I wrestled with whether it was my place to verify that he did. I decided to speak up and I was glad I did. While it didn’t end up being a close call by any means, the instructor had not spotted the traffic and appreciated the extra pair of eyes and the extra layer of caution. Allowing even a fellow passenger on a flight to point out any traffic or anything that seems off to them can add a layer of redundancy for even the most experienced pilot.

Cessna 172 Youth

At seven years old, my son makes a great copilot.  He may be better at spotting traffic than I am. Then after it’s in sight, he stays on it until it is no factor.

 

Fuel Levels
Fuel starvation is a mistake that is made more than the pilot population would like to admit. It’s also fairly simply to combat with a little discipline and a lot of the “trust but verify” concept. Any time you have the airplane fueled, make it a habit to stick the tanks to visually verify the amount of fuel in them. Miscommunication or carelessness can cause your request to “fill her up” to simply not get done the way you hoped. Even if it is your usual line guy who you know and trust, you should still verify that the tanks were filled appropriately. It is both acceptable and expected to do so – even in their presence. As a pilot, I want to make sure I have gas before I fly. And if I were the one filling the tanks, I wouldn’t want an oversight on my part to get noticed in the air when lives are at stake. A single layer of my human fallibility isn’t anything I would want anyone else to bank on.

Cessna 172 Fuel

The fuel stick works like putting your finger over a straw in a cup and lifting out the liquid. You can see the fuel level here is 24 gallons. Visually checking the fuel before every flight is the best way to know how much fuel you have on board.

 

Conclusion
As time marches on, airplanes continue to be built with better, more reliable systems and equipment. Overall, accident rates have been in a decline. While we as humans continue to gain knowledge about aviation over time, the human system will likely always be the most volatile system on the aircraft. By learning our biggest points of failure and developing systems to create redundancies for those failures, we can effectively upgrade our human system. I once heard an astronaut talking about the mistakes he made on the way to landing on the moon. He was thankful that those mistakes didn’t have any costly ramifications. Even the best of us make mistakes on our best days. We’ll never get rid of those mistakes completely, but by developing a “trust but verify” mentality, we place little safety nets underneath many of the potential mistakes of us and those around us.

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