Beyond the locked gate of the airport, the plane waits patiently out on the tarmac. It’s thirsty for fuel. I punch in the code and push open the chain-link door as it squeals on its tired hinges.
Filling up fuel in your car is typically not a fun activity. But, somehow, it’s different with a plane. Perhaps it’s the fact that the tank is just the inside of the wing — you can see (and hear) quite clearly as the fuel laps up against the edges. I watch the blue tinged fuel slowly creep its way up to the top. As it nears, I slowly let up on the pressure of the filler handle and let the fuel slow to trickle. As the vapors vent, I smell the distinct odor of AvGas.
N8831N at Mansfield Municipal Airport, 1B9 in December 2020
Climbing under the wing and bracing myself against the wheel, I drain the fuel sump to check for contaminants. I lift up the fuel inspector to the sunlight to check for the characteristic blue tint of the fuel. In the old days, some would simply dump the 50-odd mL of fuel on the ground, but today, conscious of the environment and the rising cost of fuel, most pour it back into their tank, including myself.
During this whole process, a few might even don protective rubber gloves as to avoid touching the fuel. After all, unlike automative gasoline, AvGas — or more appropriately 100 Low Lead (100LL) — is still contains trace amounts of tetraethyl-lead. The additive serves several purposes, including preventing engine knock and detonation as well as for lubrication of valves.
This situation plays out every day at nearly all airports in the United States and the rest of the world. Yet, according to the United Nations Environment Programme in their August 30 press release, “the era of leaded petrol is over.”
As others have pointed out, that’s not exactly the case. The UN EP announced that leaded fuel was finally phased out in Algeria, one of the last holdouts for automotive gasoline. However, leaded fuel in the form of 100LL AvGas is ever-present, exhausted by the light planes flying in the skies directly overhead.
Unfortunately, there currently exist no viable alternatives to leaded AvGas, which has a higher octane rating of 100 compared with the 87 of regular automative gasoline or 93 of premium automative gasoline. Consider also that most planes were designed in the 1950s and remain essentially unchanged in their powerplant designs since then, and the market is ripe for disruption. I think this highlights the need for significant research into developing alternatives that could be a drop-in replacement for traditional 100LL.
When we think of surgery, the image that most often pops into our heads is the darkened operating room, with a huddle of attendants surrounding the surgeon, all eyes glued to the surgical field. This is what Nikolai Begg, then an engineering student and now engineering director at Medtronic, thought when he first observed a surgery. While this heightened drama certainly is better for the camera and focuses our attention, the real operating room is quite a different scene.
The room is kept cool and bright, with staff bustling around setting up sterile equipment and readying the patient. The anesthesia team wheels the patient in through the double doors, gently talking the patient through what will happen as they get the anesthetic. As the patient goes under, the ventilator is connected, and a heater is switched on around the patient to keep them warm against the cool air of the OR. Eventually things settle down, but the lights do not dim just yet. Instead, the lights above the operating table are switched on and provide a focused beam on the surgical site. A time out is performed, inspired by the pre-takeoff briefing by pilots, to verify the patient and procedure.
THE PHYSICS OF PUNCTURE
Now as the first incision is about to be made, this is a critical moment in laparoscopic surgery. As Begg describes, the whole room quiets down and the surgeon is handed a trocar, essentially a modern version of a bayonet, to make several punctures through the abdomen for the camera and instruments. Begg suggests that we are all familiar with the physics of this — remember trying to stab a straw through a CapriSun juice pouch? Put too much pressure, and the instant it goes through, bam! You get a nice splash of juice all over your hand. Do it very wrong, and you might have a hole on both sides or a hurt hand as well. So imagine the stakes if the puncture is happening right above the abdomen?
Underneath the skin of the abdomen is a thin layer of fat. Beyond this is the peritoneum, similar to a balloon that encloses the abdominal organs. The challenge for the surgeon is to puncture through the peritoneum without going too far and entering the abdominal cavity and unintentionally damaging the anatomy below. In his TED talk, Begg compares this to drilling through a thin wall.
The physics are the same after all, right? When you apply a force towards the wall, there will be an equal and opposite force back towards your hand. Right at the moment when the drill first goes through the wall, however, there’s suddenly an imbalance. The wall cannot apply any force back, which results in the drill accelerating towards the wall until you can react. Begg wanted to solve this problem, and he had an idea.
POPSICLE STICKS AND RUBBER BANDS
Nearly eight years later, I too observed a laparoscopic colectomy. At the moment of puncture, I remembered this talk. The scene was the same, but this time, the surgeon was using a modern trocar which automatically retracts just as the puncture occurs. The journey from a simple metal awl to a complicated mechanism started out as a simple model using popsicle sticks and rubber bands.
It goes to show that coming up with a solution for a complex problem can sometimes be as simple as putting together a bunch of popsicle sticks in an interesting and thoughtful way. And by thinking through the physics of puncture, Begg decided to use a spring to retract the tip as soon as it went through. As pressure is put on the tip, it pushes the popsicle sticks outwards, which interferes with the wall and “sticks” through friction. However, as soon as the pressure is removed, i.e. as soon as it punctures, nothing is holding the popsicle sticks in place. The spring is then able to pull back on the tip and retract it before it can damage any structures underneath.
LOOKING FOR THE OBVIOUS
As Begg explained, this had been a serious problem for over 25 years with little change in the trocar device itself. Solving this required looking at it in a different way. Rather than attributing it to the skill of the surgeon, a mechanism could take the guesswork out and react to changes much faster than a human. The genius in this particular device is that it requires no active components and accomplishes the retraction purely mechanically.
Often, it is the most obvious problems that are the most challenging to see. We’re not always aware of them or we take things for granted. By seeing the physics of puncture, Begg was able to find a new solution that seems obvious now in hindsight. Perhaps this will inspire us to look deeper at the world around us, searching for things that we otherwise would have overlooked.
