Desktop version

Home arrow Management

  • Increase font
  • Decrease font


<<   CONTENTS   >>

Communication as Hierarchical Control

Much of this chapter has looked at communication between individuals, but the maintenance example introduced the idea of logs, diaries and job cards as control mechanisms. As well as facilitating action, communication is probably the primary control mechanism in my hierarchical system. Figure 8.2 captures some of the hierarchical communication aspects of the Embraer tragedy. In this section, I want to look at communication as a broader control process at the system level, partly because it is convenient to do so here and also because formal communication structures and protocols shape interpersonal communication. In this section, we will be looking at policies and procedures, orders and instructions as communications artefacts. In the maintenance case study, quality inspectors’ written reports, shift handover sheets, maintenance document packages and job cards represent the range of artefacts used to exert control over subordinate levels in the system. These communication artefacts are created to both satisfy a regulatory requirement and also to communicate to the end-user of the technology. Thus, they serve two purposes and this can sometimes present problems. We also need to consider not only how artefacts are constructed but also how they are interpreted and applied. The risk of communication failure is as prevalent in this domain as it was when we considered speech.

Control is typically exercised through the creation of rule sets. We can identify three types of rules: goal, process and action (Grote, 2008). Goal rules are about broader conditions and are represented by policies. A policy is a description of a state or top-level constraint. For example, the ‘clean wing’ concept which forbids dispatch with contamination on the aircraft is a ‘policy’ and, therefore a goal rule. Not all goal rules are communicated as a formal ‘policy’ but are usually written in such a way that their force is implicit. Process rules guide decisions. For example, rules are written

Communication in a system

FIGURE 8.2 Communication in a system.

to direct pilots to deice aircraft before departure if certain environmental conditions apply. Action rules are about task completion: how to do the job. In a cold-weather operations briefing, there might be specific instructions about how to conduct checks of the airframe to verify that it has been properly deiced. As we move from the action, through the process to goal rules, descriptions tend to become more generic. Policy manuals tend to be collections of different types of rules, usually formulated at the goal and process levels. Action rules are usually delegated to checklists for use on the job. Checklists, however, are subsets of larger rule sets designed to communicate specific actions. They are abbreviated process rules that describe key steps in a specific element of the task of operating the aircraft. Non-normal and emergency checklists also contain decision rules to allow for contingencies. This next case study looks at checklists in action.

On 6 April 2006, a Bombardier DHC8-Q400 (SHK, 2007) experienced a propeller overspeed. A combination of the inputs of the captain, who was pilot flying, and the performance of the aircraft automation resulted in the aircraft rapidly descending from 2000 to 1200 ft before the crew could regain control. The case study is complex. Both pilots were very experienced, having both flown the B-747, and had accumulated considerable flight time on turboprop aircraft. The technical failure occurred during the descent, prior to the aircraft levelling off but before then turning left to begin the final approach. The initial indication of a problem was via a white propeller electronic control unit warning lamp. The lamp is simply an attention-getter. The crew then need to diagnose the problem and, in this case, the right-hand propeller was found to be over-speeding. This was correctly diagnosed by the crew. The overspeed checklist was not consulted, instead the initial ‘memory items’ were completed. These call for the following actions:

Power Lever...........Retard Toward Flight Idle

Airspeed.....................................Reduce

IF unable to control propeller RPM:

Because the aircraft was in the descent, the power levers were already at flight idle and the aircraft speed was reducing towards the final target speed for the approach. Therefore, it was felt that these conditions had been satisfied. As the aircraft levelled off at 2000 ft, the captain increased power on the left-hand engine in order to maintain level flight. The aircraft’s own automatic systems increased power to the left-hand engine such that there was now greater than 100% torque applied to the left side. The right-hand propeller, still at flight idle, presented a negative angle of attack to the airflow and, as such, was an effective speed brake. The resultant drag caused the temporary loss of control.

Before we look at the formal communication represented by the checklist, we should just look at the communication between the crew. On two occasions, the FO suggested that they ‘secure’ the right engine. Both times the captain rejected the idea. In his evidence, the captain said that he thought that was the engine was ‘dead’. He had constructed the situation as the loss of the engine but, given that they were commencing the final approach, he did not want to start the complex process of shutting down the engine at that moment. The FO conceived of the situation as a propeller problem and the action of ‘securing’ the engine would automatically cause the propeller to auto-feather and, thus, reduce the drag. By referring to the engine while actually meaning reducing the drag from the propeller, the FO failed to communicate her intent to the captain. The propositional content of the speech act was obscured. It is interesting that the pilots were, nonetheless, communicating in formal, professional terms.

Returning to the checklist, documentation can be evaluated in terms of its formulation, intent and scope. To a degree, these categories overlap those we saw earlier when we looked at the properties of speech. The formulation is similar to the linguistic form in that it captures the use of language - in this case, written - to communicate information. The intent is similar to propositional content in that it relates to the information contained in the checklist items. Social force is implicit in that the checklist is an official document. I have added a third dimension, scope, that possibly does not apply as widely to communication at the interpersonal level. It relates to the range of circumstances under which the communication applies. The context may change the appropriateness of a specific rule.

The intent of the first two actions in the Q400 checklist is to reduce the load on the propeller to stop the situation getting any worse: we are stabilising the problem. In the context of the event, the crew had simply identified an issue and taken the initial steps. The checklist actions neither diagnosed the problem nor represent an appropriate response.

Moving on to scope, there are three phases of flight during which a crew might need to cope with a propeller issue: during take-off and climb, in the cruise and during a descent. During take-off, the pilots activate an automatic feathering system designed to cope with a failure at a critical stage of flight. The captain had completed his periodic company training the week before the event during which he rehearsed a propeller overspeed after take-off. It seems that the checklist was designed to cope with an overspeed in the cruise phase of flight, hence the need to reduce the load. This is not an issue in the descent. Once the aircraft levelled off, the propeller now became an issue because of the drag it induced. Ironically, the correct action at this point would have been to advance the power level to a position of about 10% torque, which equates to the minimum drag position. The appropriate action was the opposite of the action required by the checklist. While automation can deal with the take-off, the checklist can deal with the cruise, it seems the designers forgot about the descent.

Formulation describes the use of language and is the textual equivalent of linguistic form. The propeller overspeed checklist includes the following:

Note: If the engine is not shutdown immediately after feather the propeller with the

Alternate Feather system, the propeller may unfeather [...]

This statement is not correct in its use of English. Its meaning, mirage-like, flickers and fades witli every reading. The text would be correct if ‘after feather’ was changed to ‘after feathering’. The meaning would be clear, however, to a pilot already experienced on aircraft fitted with feathering propellers. Could such a simple change be difficult to make? We will return to this checklist in Chapter 10 but, for now, we can see how control fails at a systemic level because of poorly framed documents.

 
<<   CONTENTS   >>

Related topics