Archive for October, 2011

Oxygen Bar

Wednesday, October 26th, 2011

Last week we talked about the joys of operating in the flight levels and judging from the comments, the votes seemed to be overwhelmingly in favor of “bigger is better” or at least, easier. I recounted the wonders of the Cessna 441 at FL350 but there is one drawback to that magnificent machine.

The cabin altitude is about 11,000 feet and where slow-onset hypoxia should be considered. Some of the Foundation staff will claim that I’ve spent way too much time at altitude and am permanently hypoxic. (There are times I would agree.) However, this topic gets relatively little attention and even the FARs don’t even bring up the subject of oxygen impairment below 12,500 (5,000 at night). This blog is NOT about rapid decompression where the time of useful consciousness at those altitudes is measured in seconds.

A pulse oximeter is a wonderfully simple-to-use device that clips on a finger tip to instantly measure your oxygen saturation (sat)  and heart rate.  Ideally, at sea level, we’d all have 100% saturation and a pulse of about 60 – fat chance!  Many pilots may start in the low 90s. When your sat drops below 90%, oxygen deprivation is starting to take place. Thinking slows, and heart rate increases as the brain asks for more O2 to be pumped up.

As the sats fall, so does your ability and it can be quite insidious. After a few hours at 9,000-10,000, where many light non-pressurized aircraft fly, many of us will be hypoxic. A slight headache, fatigue, and the inability to process information as quickly as normal, are all symptoms but they vary person to person. But is it operationally significant? In more than few accident cases we see where an otherwise capable pilot made a poor decision that resulted in an accident. Why? One factor that is certainly present in some cases is slow onset hypoxia but you can’t measure O2 saturation on a corpse so the causes remain elusive and speculative.

On my flight back across the country in the C441 at FL350 last week (which we did non-stop in under 6 hours incidentally)  checking the sats was instructive. Both crew seats are equipped with quick-don masks and when my sat was dipping below 90% I’d take a few minutes to bring it back up to normal.  During these episodes it sounded like Darth Vader’s heavy breathing (Right here above planet earth but no Death Star in sight). Sitting in the back for a bit, without the benefit of oxygen,  resulted in sleepiness and my usual slight headache. The oxygen cleared it up. It’s bad enough when passengers are sleepy and a bit out of sorts. Their brains are starving for good air but for pilots this is critical.

The message is clear–if you spend much time above a cabin altitude of 8,000, your sats are going to come down—how quickly varies by individual. Healthy, fit, non-smokers will do better than others. Even if you’re not flying a turbocharged aircraft, you may want to think about  buying a pulse oximeter—they’re available for $30 – $100. After that little stocking stuffer, if the aircraft isn’t so equipped, get a portable oxygen system—your brain (and other body parts) will love it! The Air Safety Institute will be reviewing pilot misbehavior in the future due to oxygen deprivation.

Anyone have a good hypoxia story?

Flight Level Flight

Wednesday, October 19th, 2011

I’ve  enjoyed the privilege of being invited into the flight levels by friends and co-workers, sometimes as PIC and other times just a radio operator/navigator. (Remember when those used to be career fields once upon a time?–but it’s not a growth area these days.) Last week it was high and fast flight on board a friend’s Cessna 441. The trip was East coast to Vegas for NBAA and a speech, then to Prescott, AZ to visit Embry Riddle’s western campus, where I sit on a safety advisory board, then to California to visit Foundation donors and return.

A couple of observations: First, everyone reading this blog knows that GA makes trips possible that would be impossible or completely impractical on the airlines–wish some in our government could understand that. (The Foundation is working on the image education aspect for the general public.)

Secondly, flight in the flight levels is usually much easier than down low. I’m always amazed at the simple operation of turbines compared to pistons: no leaning, no shock cooling, easy starting – etc. Flying high over the mountains is much better than slogging through up and down drafts, dealing with ice and not being able to see boomers nearly as well.

There is turbulence up high but not nearly as much and it is well forecast. There is great psychological comfort in knowing that if you’re getting the bejabbers kicked out of you on takeoff or descent, it will usually be over in a few minutes. Also a highly wing loaded aircraft rides the waves better.  Down low, I’ve had flights where it’s best to resign yourself to a long and largely uncomfortable ride. Best to cancel those trips if passengers are going. Icing? Not very often at -20C.

The machines, while complex are also highly reliable with lots of redundancy–not perfect–but very good. Training tends to be much better for turbine pilots because the hull values are high so insurers want to protect their investment. Owners usually also want to protect those reliable and very expensive engines by understanding how they work. The avionics are now largely comparable between high and low altitude aircraft but I remember well both flying and teaching basic IFR in basic aircraft–no autopilot, and no flight director. The workload was a lot higher by looking multiple places for information. After seeing my first flight director the awe that I held for high end pilots largely evaporated. (“Just tuck the V-bars into the wedge son and adjust your power on the way down until getting to minimums”–but I digress. )

Next week we should talk about oxygen. In the meantime, is it your experience that bigger aircraft are generally easier to fly or not?

What Happens in Vegas…

Wednesday, October 12th, 2011

I spent this past Sunday in Las Vegas at the Single-Pilot Safety Standdown, held in conjunction with the NBAA Convention. There were presentations on how to fly single-pilot better. Dr. Earl Weener, a NTSB Board Member, recounted an accident of an overloaded PC-12 that crashed in Montana because the pilot neglected to use anti-icing additives in the fuel and then delayed way too long in diverting to another airport when it became obvious that the aircraft would not stay aloft to the destination. There were 13 fatalities.

My presentation was on runway excursions, which was discussed in last month’s AOPA Pilot. One area that we talked about, and was a recurrent theme in most of the presentations, was the ever-present human factors.

Here are some for your consideration:

  • Ignorance
  • Fatigue
  • Skill
  • Distraction
  • Complacency
  • Arrogance

As I thought about it, these elements are present in every flight to varying degrees. Not every one, every time but at varying times – it’s part of the human condition.

They are most certainly present in accident flights in different amounts. Have you thought about which one might be prominent in your cockpit as you fly along, and how you would compensate?

I hadn’t looked at these attributes quite that way before and I can think of circumstances in my own flying where there was perhaps just a bit too much luck involved.

How about you?