Thursday, July 30, 2015

Of Micromorts and Risk Buckets...

Each of us carries an invisible bucket of risk with us, each minute of every day we are alive. Every human activity is accompanied by risk - consider the pilots who were flying a flight simulator in a building next to an airport and were killed by an aircraft crashing through the roof.

Some activities impose greater risks than others, and it is worth considering how much risk is in our risk bucket at any moment. It is also interesting to observe how people accommodate risk - how they sometimes carry a full bucket for no valid reason. Every choice we make affects how much risk is in our bucket, and a thoughtful person will balance risks and rewards, or will weigh one set of  risks against another - he or she will choose the lesser of two evils.

A risk is a value comprised of two factors, first the likelihood that an event will occur and second the level of pain, suffering, or loss that we suffer should the worst happen. In aviation, our chief concerns are crashing - damaging or destroying aircraft - hurting or killing people. We are - on the surface - very concerned with risk, some might say "risk-averse" - but underneath, at our core, we tend to accommodate risk with a somewhat fatalistic attitude. We are "flyers" after all,  dashing and unafraid...

After my friend Randy took my helicopter and crew in Honduras in 1988, because he had developed a distaste for his platoon leader, and on this very first flight without me on board the combining transmission failed and killed them all - I got spooked. Another pilot in my company told me, somewhat dismissively, "it's aviation, people die - if you can't accept that you are in the wrong line of work."

Really? We have to accept that dying is a part of flying? Don't we have any control of our fate?

In his book "Fate is the Hunter," Earnest K. Gann postulated that fate is a killer that strikes us who fly randomly, without warning or recourse, and if we choose to fly we must accept this.

I choose to believe that, while some failures of people or equipment are so bizarre as to be unforeseeable (Colgate-Palmolive's BK losing a tail rotor, Hermann LifeFlight's BK slinging a blade), these type of events are so rare as to be in the "micromort" category.

  1. micromort is a unit of risk measuring a one-in-a-million probability of death (from micro- and mortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. (Wikipedia)

So, as I see it, the objective is to always have as few micromorts in my risk bucket as possible, and to make every aeronautical decision with a view to this end (and the prevention of my end).

Let's consider the altitude we fly at. Medical crews tell me that I fly at greater altitudes than my peers. We VFR pilots do have a pretty large latitude in this area - Part 135 of the CFRs says we must be at least 300 feet above the surface when flying people for money - our companies may direct us to be at least 1000 or 1500 feet "when possible, taking into account the ceiling." Patients may have medical issues that push us to fly low. But I have observed a pilot to fly at 700 feet above the ground during the day with no patient on board simply - I suppose - out of habit. I was giving him a local area orientation and didn't feel that it was appropriate to question another experienced aviator about his altitude choices.

That pilot is dead now. Click here to read his sad and unfortunate story.

How high we fly, how fast we fly, how much or little fuel we fly with, how much wind we will operate in, the angle and speed at which we make approaches and departures... these are all aeronautical decisions, and they all involve micromorts which we have in our risk bucket.

Let's look at altitude, and the single engine helicopter. If we choose to fly at low altitude - we are -knowingly or not, accepting the risk of the engine losing power with less time and space to: 

1. Realize that we have a problem. Recognize the change in engine sound, rotor RPM, instrument indications.

2. Transition from normal powered flight to autorotative flight - collective down and - at cruise speeds - cyclic back to maintain rotor RPM. We may have to make some adjustments as we "fly the disk" and let the rotor RPM stabilize. We are looking inside now.

3. Diagnose the real nature of the problem. Is this a failure of the engine or a low-side governor problem? If it is a governor problem can we find the fuel control lever or emergency governor control and adjust it to regain power before ground contact? We are still looking inside.

4. Now, look outside! Find a place to land. Is there a place to land in  this forest, swamp, marsh, or city? Can we reach it?

5. Are the aircraft and crew configured for landing? The patient?

All that stuff takes time and altitude. The lone survivor of a recent crash said that after the engine quit, notwithstanding the pilots stating twice "don't do this to me," they were down in "10 seconds." I want more time than that.

Now, sometimes we are going to be in a position where we willfully turn our backs on all of these micromorts.  Flying in the avoid-area of the height-velocity diagram ( located in the rotorcraft flight manual) means that an engine failure will end badly, and we do it because our job occasionally requires us to. Power line repair pilots spend lots of time hovering next to tall wire structures. Any problems for these pilots are very difficult to overcome....

On August 19, 2014, about 1100 central daylight time, a McDonnell Douglas 369E, N444RS, was substantially damaged when it impacted a utility wire and terrain while maneuvering near Northport, Alabama. The commercial pilot and the passenger were fatally injured.

We should be conscious of our decision to accept risk - every time - and perhaps we should announce it so everyone will pay attention to what's happening. A nurse and I were talking about the way we make approaches into a hospital pad, 200 feet per minute for the bottom 300 feet. He said, "I understand the slow approach, but I wish we didn't make it over that power substation."


I was adding risk to my bucket without thought or reason. No need to be dead and fried when we can simply be dead after engine failure.

In short, flying at low altitude adds micromorts to our risk bucket. Are we doing this for a reason?

"Witnesses located at various locations at the World War II Valor in the Pacific National Monument reported observing the helicopter near their location traveling at a low altitude before it suddenly descended into the water."

This is the case with many decisions we make. We add or subtract from our bucket. Are we taking pictures with our smart phones? Are we taking off with too much or too little fuel? Are we texting? Are we flying over trash-dumps - where birds congregate? Are we clearing the aircraft before turning or moving near the ground? Do we do a preflight each shift?

Do we take a fuel sample or just change the date on the bottle?

Do we carefully walk around and double check for latches and cords before climbing in every time. 

Is this latch secured?

All these things involve risk.

Being a pilot - or member of a flight crew - may appear easy on the surface, but the devil is in the details. Attending to the details requires professionalism and self-discipline. Over the years we grow complacent and begin to accommodate to risk. We carry a full bucket for no reason, because we have done it before...

And those Micromorts, and that risk bucket?  They are there with you on every flight.

edited 8/1/15, 2/28/16, 6/6/17

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