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What Does Expertise Look Like?

The Cessna 208 Caravan is a robust workhorse, providing passenger and cargo services in some of the more rugged parts of the world and is the backbone of the parcel feeder networks in the USA. The aircraft’s performance in icing conditions is a frequent source of debate among Caravan pilots. The following paragraphs are a set of posts taken from a dedicated Cessna 208 website (

POST 1.1

The a/c has had an icing problem since 1985. I checked out in Feb of 1986, started flying across the Rocky Mountains at 16,000. 17,000 ft, this was before FlightSafety or Pan Am (note - training providers with C-208 sims). I was taught by on old Cessna instructor [...] in Wichita. He told me this a/c will handle ice, shown picture of a ‘van with up to 3 inches of ice on the leading edge, the picture was taken by a test pilot upon landing in Minot N.D. So off I went to fly DEN- ASE-GJT. Colorado. I learned fast the a/c is under-powered, and the boots system is marginal at best with low airspeed. I learned to take off with 20 flaps move flaps up at 100 kts. and leave 10 flaps in until reaching cruise airspeed. Ice en route? climb if able, most of time could not. If a/c quit climbing ask for block alt and fly the airspeed if a/c started to descend I would let it lose height as slow as possible on the vsi to the MEA and then declare emergency to the nearest airport. I operate the boots with about 1/4 in and continuous at 1 min intervals. If anyone has to cycle the prop, hang on! It will fill your pants the first time. When we started {recurrent sim training) I was chewed out for not following the flight profiles for t/o, and for ILS approaches. When I have to move the power lever full up I take my foot and “kick it higher”. The a/c needs more horsepower and a better boot systems. If Cessna or other operators do not address these issues we got a problem!! Certifying the pilots for flying in ice is not the answer!!!

POST 1.2

The problem was with your route (DEN-ASE-GJT) and your schedule, not the airplane. Go and fly PBI-EYW-TPA a few times on your own schedule and then let us know how you like the airplane and if it's still under-powered. Aside from a few other freight routes in the world with predictable moderate icing, you were flying the worst case scenario every day during the winter. Whomever operated your airplane could have chosen a different aircraft for the with more power yet equal payload and operating costs...let's see, which one would that be? Capt. Slow is right...either leave some freight behind or cancel and stay overnight at a Holiday Inn and wake up refreshed. Icing incidents are solely the fault of the pilot, not the airplane. You are in total control of how much ice gets on your airplane. If you don't believe that, or if for some reason you're not, then there's gonna be trouble.

POST 1.3

Here we go again!!

You are NOT AWAYS in control of how much ice you pick up. Go fly in the Pacific Northwest and experience over an inch of ice in less than three minutes. By the time you can do anything there it is. So, turn around you say? Good— I just flew through that stuff and now I am supposed to go back into it? I think not. Descend, you say... MEA over the mountains is 14,000. Climb, you say? Yeah, right. As I am already unable to maintain the newly mandated 120kts. that is not an option. And there was only trace forecast and reported along the route.

Pontificating about the Caravan’s capabilities should probably be a thing of the past. It is down to skill and luck in the ice and the people that have a certain amount of skill and a lot of experience in the Van are usually the lucky ones. But not always.

The Caravan is a GREAT aircraft if it is kept in a safe environment. I have been flying one for 16years in the mountains, so I guess I can speak a little about the aircraft. Also, in the last couple years I have elected not to depart more than in the previous 14 years. I’d rather be in trouble on the ground than in trouble in the air and wishing I was on the ground. Been there and done that, but not anymore. And my boss actually supports this new decision making procedure.

So. fly the ‘Van safely and wisely and it will get you home every time.

POST 1.4

I have 4000 hours flying the ‘van in Alaska. I have had two encounters with severe ice which the plane handled fine. Both times I exceeded one and a half inches of ice on a non-booted plane. Both times I had a forward C of G and way under gross weight. The ‘van with a forward C of G has a downloaded stabiliser and it works fine. Knowing what I know now about the van changes how I fly in the ice.

The ‘van with an aft C of G has an uploaded stabiliser which has airflow adhesion problems. Thus the vane guides on the stab. Any contamination on the stab when it is uploaded is dangerous and should be avoided.

Now if I am flying the van and I have an aft C of G and pick up ice I deploy some flaps to assure that I have a downloaded stab and land as soon as possible.

In order to make sense of these comments, we need a framework that will allow us to identify the different elements of performance. It is common to categorise behaviour in terms of knowledge, skills and attitudes. Knowledge can be assessed through questioning, either verbally or with a written examination. Skills can be assessed by observing a demonstration of workplace activity. Attitudes are more problematic. In simple terms, attitudes are protobehaviours: they are dispositions to act in a particular way. They are difficult to define and even harder to formally ‘train’ and assess. This tripartite structure of outputs seems plausible but starts to unravel if we look closer. Skills, for example, can be likened to computer run-time code in that they are the enactment of some sort of knowledge structure. If I need to have a mental representation of the action I am trying to undertake, how is a skill different from ‘knowledge’? Without knowledge, I cannot enact the skill. Attitude objectives often read like ‘wish lists’ of desired behaviours. These labels, of course, are artefacts and the exact mechanism of storage in the brain remains a conjecture rather than an anatomical fact. Modern imaging techniques allow us to study brain activation during various recall tasks but the fact remains that what we call ‘learning’ is still something of a mystery in terms of storage methods.

It is more useful to consider two classes of knowledge: declarative and process. Declarative knowledge describes attributes about the world while process knowledge describes rules about action. This might sound like we are back to ‘skills and knowledge’ discussed earlier but this is not the case. Declarative knowledge is usually thought of as concepts and facts but, in relation to expertise, I suggest that declarative knowledge represents sets of constraints that must be satisfied in order for a particular condition to be considered ‘true’ (Ohlsson, 2011). For example, if asked ‘what is the capital of France’ I must, first, recall the names of all French cities that I have in my memory - a set of facts - and then select one that satisfies the constraint . Of course, ‘capital city’ is, itself, a construct. Lyon is a large French city knowrn to me but it does not satisfy the ‘capital city’ constraint. In an aviation context, the requirement to be ‘stable’ at a specific point on the approach requires a pilot to have a set of constraints in memory that can be applied to the current status of the aircraft. The condition ‘stable’ can then be declared either true or false. If false, then process knowledge is applied to rectify the situation. Process knowledge comprises rules that guide action. By framing declarative knowledge as a constraint set, we can also reframe ‘error’ as a form of feedback. The performance deemed ‘erroneous’ typically violates a constraint, it is discrepant, and should trigger remedial action. We will come back to this when we look at error in more detail in Chapter 6.

Rasmussen (1983) proposes three categories of behaviour: skill-based, rule-based and knowledge-based, generally referred to as the SRK framework. Skill-based behaviour comprises collections of sensorimotor routines that constitute observed action. Hand flying an aircraft requires the complex arrangement of various sensorimotor inputs to the aircraft controls if it is to be conducted successfully. Skill- based behaviour becomes more proficient over time such that, eventually, it becomes almost automatic, requiring little formal conscious control. In effect, the allocation of attention to task monitoring is minimal or even subliminal. Rule-based behaviour comprises collections of statements that allow' us to select between competing skill-based routines. Rules can be formally prescribed, as in procedures


A Framework of Expertise


Constructed solutions to new problems generated by mental models

Improvise equipment configurations

Improvise new techniques or configurations Creating alternative plans

Planned goal denied, improvise new goal


Cue-directed selection between alternative routines

Select configuration in support of operating procedures

Recognising progress towards goal. Selecting alternative procedures or configurations

IF this rule THEN next action ELSE different rule


Sensorimotor control of action

Operation of equipment

Visualisation of path Anticipate selections

Cue generation to corroborate future state


Manipulate hardware, software and people to achieve goal

Manoeuvre Direct device in a specific direction. Short-term activity

Trajectory Action intended to achieve future goals Long term

and checklists, or derived from experience. Knowledge-based behaviour is the process of deriving new rules to deal with novel situations. In order to be successful at this level, we need robust, representative models held in memory that can be used to run ‘what if scenarios. The SRK framework represents the actions, or outputs, that flow from the declarative/process knowledge.

In Table 1.2, I have attempted to categorise types of ‘knowledge’ in a framework that reflects the nature of work. Along the vertical axis, I show Rasmussen’s SRK taxonomy. These categories seem to reflect mental storage in that each type of behaviour requires additional cognitive effort as measured in recall response times. Skill-based responses can be recalled from memory faster than knowledge-based responses. The horizontal axis reflects the time available for execution. ‘System’ reflects actions associated with the immediate configuration of the aircraft, system or device. ‘Manoeuvre’ reflects action in the near-term while ‘trajectory’ is a requirement to consider actions needed at some future stage and reflects the fact that an action now could have a consequence in future.

Returning to the Cessna Caravan pilots discussing flight in icing, Table 1.3 contains statements that reflect examples of expertise: knowledge applied to an operational context. Post 1.3 also illustrates what we mean by a possible ‘attitude’. The poster comments:

I’d rather be in trouble on the ground than in trouble in the air and wishing I was on the ground. Been there and done that, but not anymore. And my boss actually supports this new decision making procedure.

What we can see in this statement is a belief that safety is more important than production and, importantly, the poster also shows how positive reinforcement by management influences attitude development.


Caravan Pilot 'Expertise'


The van with a forward c/g has a downloaded stabiliser and it works fine

[L]eave some freight behind or cancel and stay overnight at a Holiday Inn and wake up refreshed


Now if I am flying [...]

I have an aft c/g and pick up ice I deploy some flaps to assure that I have a downloaded stab

I learned to t/o with 20 flaps move flaps up at 100 kts. and leave 10 flaps in until reaching cruise a/s

If a/c quit climbing ask for block alt and fly the airspeed If a/c started to descend, I would let it lose height as slow as possible on the vsi to the MEA and then declare emergency to the nearest airport


I operate the boots with about 1/4 in and continuous at 1 min intervals





Distribution of Comments







1 (2.6%)

9 (23%)








2 (5.2%)



2 (5.2%)






The Caravan is a relatively simple aircraft in terms of structure and, so, it is not surprising that there are relatively few comments relating to the skills, with just 2 (0.5% of the total) references to operating aircraft systems. In Post 1.1, we see references to the use of the propeller de-icing, leading edge boots and to the operation of the power levers. Of the 38 statements contained in the four posts, most are evenly divided between rule-based and knowledge-based behaviours (see Table 1.4). The single largest category is knowledge/trajectory. This has implications for what we mean by ‘CRM competence’. Effective decision-making - a key ‘nontechnical’ skill - in critical situations depends upon robust knowledge structures.

It is of interest that most of the time, crews work in the four cells that comprise the lower left portion of the framework, highlighted in Table 1.3. The industry model of training is focussed largely on developing proficiency to cope with a set of aircraft ‘states’ described by this quadrant. Accidents, however, typically involve behaviours associated with the four cells that make up the upper right quadrant. The rule/ manoeuvre cell is a transition zone between control and failure. Airline recurrent training, if it is to develop system resilience, should focus on developing the expertise need to control the set of contingencies that occupy the top-right quadrant.

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