How to Kill People in Clouds

Luke Bucklin disappears in a Mooney, foolishly
See also
http://www.startribune.com/local/west/105871163.html?elr=KArks:DCiU1PciUiD3aPc:_Yyc:aUoaEYY_1Pc_bDaEP7U

(I am a commercially and instrument rated glider and airplane pilot, and an FAA-designated Sr. Aviation Medical Examiner and a general internist interested in aviation human factors.)

This tragedy illustrates the fact that 90% of aircraft accidents are due to the misperceptions, miscalculations, or mistakes of the most complex part of the aircraft: the flesh-and-bones thing operating the controls. Another pilot and I were chatting about the circumstances of this disappearance, based on media reports; he summarized by saying, “That was manslaughter! He should never have taken off in that plane in that weather!”

Why does he feel this way? Because the situation strongly suggests that this pilot experienced loss of control due to tailplane icing and plummeted to earth. And the pilot knew, or should have known, the dangers.

Factors:
1: the particular model of aircraft that he flew is not certified for flight into known icing conditions; in fact, federal regulations prohibit this and similar aircraft from being flown into known icing conditions. Debate does exist on just what “known” means, legally, but … if we know there’s gonna be more than trivial ice, we really shouldn’t go there.
2: Snowfall always means there is icing in the clouds! And the icing continues to accumulate until the airplane breaks out of the cloud tops (if indeed the airplane is capable of climbing to such an altitude) or descends to above-freezing temperatures.
3: The model aircraft he flew is not turbocharged, and has significantly decreased power above about 12,000 ft, leaving small margin for adverse conditions.
4: Icing conditions affect the efficiency of the propeller, decreasing power and speed; decreasing the efficiency of the wing, which both decreases lift and increases drag; and, most importantly, the tail (invisible to the pilot), decreasing the pilot’s ability to hold the nose up with the elevator control.
5: During the crash, ice breaks off, and quickly melts as soon as there’s warmth, removing the evidence from post-crash investigators.

So, knowing that this man took off into clouds from which was falling snow, at high altitude, with minimum enroute altitude of 15,800ft well above the best performance of his aircraft, over unlandable terrain, we can conclude that he has deliberately flown into a dangerous combination of risks. This is spelled R-E-C-K-L-E-S-S.

What evidence is available regarding this?

I looked up the flight trace and airplane registration on flightaware.com
http://flightaware.com/resources/registration/N201HF
This shows that the pilot was flying a 33 year old Mooney, a wonderful airplane, but one that is equipped neither with anti-icing equipment that could reduce ice accumulation, nor with engine turbocharging.
It is possible to purchase aftermarket anti-icing for this aircraft, but it reduces top speed slightly and load-carrying capacity significantly, and in any case is NOT approved for flight into known icing conditions (it’s useful for inadvertent icing encounters; I have such a system on my own Mooney).
It is possible to purchase an turbocharged engine for this aircraft, but it’s much more cost-effective to purchase the turbocharged model; I would be amazed if this aircraft had had such a conversion. A turbocharged Mooney can climb to about 22,000 ft if equipped with oxygen. But even this altitude may not outclimb icy clouds. When there’s snow, cloud tops are often in the range of 20s thousand feet altitude.
In addition, while the Mooney does have 4 seats, its load-carrying capacity with full fuel tanks seldom permits 4 people with luggage. I would be very surprised if this aircraft had not been somewhat over its maximum gross weight. This decreases the maximum altitude it can achieve and raises the stall speed; other adverse consequences are not related to this flight (less margin in bad turbulence, potential damage to landing gear on landing).

Now, let’s look at the flight trace:
http://flightaware.com/live/flight/N201HF

If you zoom in on the map, you will see that the airplane went straight and true after turning on course.
If you click on track log and graph http://flightaware.com/live/flight/N201HF/history/20101025/1730Z/KJAC/KPIR/tracklog you will see a graph of altitude (with a spurious ravine, a gap in data.

If you scroll down on that page, you will see a spreadsheet of data, that, to the knowledgeable person, has some very suggestive data (isn’t that just the way data works?).
First, we have to realize that this is “data” and subject to error. We need to look at consistencies.

What does this data tell us? There’s a story here.
1: Look at climb rates. The FAA standard expected climb for piston-engine aircraft in instrument conditions is 500 ft/min. This airplane at sea level is probably capable of almost 1500 ft/min. Climb rate decreases with altitude, as the engine’s maximum power decreases as the air gets less dense. As a rule of thumb, the instrument pilot is embarrassed or worried when an airplane is not able achieve 500 ft/min. If you look at this data, you see that the pilot was able to exceed this rate up to 11,600 ft., at 3:14 pm. He maintained about 12,000 ft from 3:15 to about 3:20, then climbed to about 14,000 until 3:30 (2000 ft in 10 min is 200 ft/min, a slow climb) After 3:14, we see that he never again had a rate of climb more than 240 ft/min, and he appears to have been maintaining 14,000 ft. (I read that he was assigned 15,800, but the minimum enroute altitude in this sector is 14,000 and there’s no clear sign in the trace that a climb was attempted. I would be surprised if a controller gave this particular aircraft a higher altitude than necessary.)
To see the minimum altitudes, you can go to skyvector.com, enter KJAC and click GO, then click on IFR charts, and use your mouse to look at the routes, e.g. http://skyvector.com/?ll=43.607333333,-110.73775&chart=411&zoom=3 the miminum enroute altitude for the airways (white band with black line) is printed above the small reverse-type airway designation (V298 and V330 in this case)
2: look at the ground speeds. This is airspeed +/- wind, but the wind is a constant factor. This airplane has a normal cruise speed around 150 kt. We don’t know what the winds aloft were that day; but winds above about 10,000 feet are almost always westerly. This plus airspeeds under 130 kt until 3:31 suggest that he was slow for some reason. I normally climb my Mooney at about 130kt and 500 fpm; he would be able to do this to about 10-12,000 ft and then performance would trail off. His climb speeds were about 100 kt; some Mooney pilots do climb at this speed.
However, ground speeds reached about 160 kt by 3:32 pm
3: Notice that after 3:34 pm, the ground speed rapidly decays to 118 kt at 3:49 (in 15 minutes) while maintaining 14,000 ft (to repeat, we have to look at consistencies; my experience is that this FAA-based data, reported from calculations of transponder returns, tends to fluctuate).

What could cause this slowing?
1: A decision by the pilot to save fuel. Unlikely: pilots prefer to go fast; otherwise they could drive.
2: A loss of engine power. Unlikely: pilots have engine-monitoring instruments, and generally get very anxious, especially over water or unlandable terrain with any engine malfunction.
3: Accumulation of ice. Likely: it’s insidious; there’s a certain bravado among some pilots (“Hey, I had nearly a inch of ice, and my Mooney handled it just fine! I kept my airspeed up, and just descended into warm air!”); and, most important, its accumulation on the tailplane is invisible from the cockpit.
The Mooney has a special characteristic: the elevator, in level flight, can be “locked” by ice, especially if the autopilot is used (the autopilot flies much more smoothly than a human, who continually moves the controls to make small corrections)
A very nice illustration of the Mooney’s elevator, the same model as the missing aircraft, is at http://boxybutgood.com/M20F/1024/00053.jpg
Note that the end of the elevator has an arm-like extension. This is a balance weight. In level flight, the elevator is angled downward to the rear; the front end of this balance weight is *above* the plane of the horizontal stabilizer to which it’s attached. Ice can fill this gap and trap the elevator from being deflected up if the nose needs to be raised. We cannot know whether Mr. Bucklin was using his autopilot, but I am sure that his aircraft had one and would be surprised if he had not had it engaged.

Why does an airplane crash in icing conditions? Usually, because of tailplane icing. Most pilots, in my experience, are ignorant of the risks of tailplane icing, discussed thoroughly and illustrated in this NASA video: http://video.google.com/videoplay?docid=2238323060735779946# It’s a 20-minute video, so I’ll summarize by saying that the tail holds the airplane up. That is, the heavy engine is well in front of the center of gravity, airplanes are deliberately nose-heavy, so that if they stall, they’ll descend nose-first and pick up speed going forwards. The horizontal tail is a small wing; it generates downward-directed lift to balance the engine’s weight. Changing the angle of the elevator permits climb and descent (technically, it adjusts the speed by changing the wing’s angle of attack, and the engine power is adjusted to manage the actual rate of climb or descent).
Ice reduces the ability of the horizontal tail to generate this balancing downward-directed lift; beyond a certain point, the tail cannot lift the nose of the aircraft, which then becomes a lawn dart.

Final datum: Look at 3:50 to 3:52. While not speeding up, Mr. Bucklin’s aircraft descends 1000 ft in 2 minutes, 1300 ft in one minute. Deviation from one’s assigned altitude by more than 300 ft is a violation of federal air regulations. No attentive pilot would have deliberately made such a descent. This strongly suggests that the earlier decay in airspeed was due to insidious loss of propeller and wing efficiency due to icing, and the rapid loss of altitude due to continued ice accumulation, probably rendering the tailplane relatively ineffective in holding the nose up in a level attitude.

Summary:
Mr. Bucklin took off into snowy clouds, assuredly containing some ice.
Mr. Bucklin appears slower than usual for his model aircraft.
Climb rates after 12000 ft are slower than usual
Aircraft speed mysteriously decreases in the last 6 minutes of flight
The aircraft begins a rapid, inappropriate descent after going slowly for 3 minutes.
If I were traveling with 3 sons, the autopilot would have been on, and there would have been much happily distracting conversation. There is no reason to think that Mr. Bucklin would have noticed insidious loss of speed in just 5 or 6 minutes.