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Difficulty: Very hardRecognizing Implied Cause and Effect

During the 1924 polar mapping expedition, command directives required survey aircraft to operate at 8,000 feet over the jagged interior ranges. A persistent, unbroken stratocumulus cloud layer typically hovered at 6,000 feet across the region. High-intensity visual navigation beacons were stationed deep within the valleys to guide the flight crews. Over three days, consecutive survey flights drifted far from their assigned corridors. The aircrews logged that they navigated the interior solely using magnetic compasses and dead reckoning. Command subsequently issued updated directives, mandating that all future flights in that sector operate at a maximum altitude of 4,000 feet.

Based on the passage, what unstated factor most likely necessitated the command's decision to lower the maximum flight altitude?

  1. The unbroken cloud layer situated between the aircraft and the valleys blocked visual contact with the navigation beacons.Answer
  2. B
    The aircrews navigated the interior solely using magnetic compasses and dead reckoning over the jagged ranges.
  3. C
    Magnetic compasses experienced severe deviations when operated at an altitude of 8,000 feet over the interior ranges.
  4. D
    The flights drifting from their assigned corridors caused the aircrews to abandon the visual navigation aids.

Answer

The unbroken cloud layer situated between the aircraft and the valleys blocked visual contact with the navigation beacons.
The passage states that the aircraft flew at 8,000 feet, above an unbroken cloud layer at 6,000 feet, while the visual beacons were on the ground. This physical arrangement meant that the clouds blocked the pilots' view of the visual beacons. Because they could not see the beacons, they had to use less accurate navigation methods, which caused them to drift. Lowering the altitude to 4,000 feet places the aircraft below the clouds, re-establishing visual contact with the beacons. Therefore, the obscured line of sight was the unstated factor that drove the rule change.

Step-by-Step Solution

1
Analyze the spatial relationship between the aircraft, clouds, and beacons.
Aircraft were operating at 8,000 feet, clouds were at 6,000 feet, and visual beacons were stationed in the valleys below.
Understanding the physical arrangement of the elements is necessary to deduce visibility.
2
Determine the limitation placed on the aircrews based on the spatial arrangement.
The unbroken cloud layer at 6,000 feet physically obstructed the line of sight between the aircraft at 8,000 feet and the visual beacons on the ground.
This explains why the primary navigation method was unavailable.
3
Connect the visual obstruction to the navigation method and the subsequent problem.
Unable to see the beacons, crews relied on compasses and dead reckoning, which resulted in drifting off course.
This establishes the full chain of events leading to the navigation errors.
4
Evaluate how the command's new directive solves the problem.
Lowering the altitude to 4,000 feet places the aircraft below the 6,000-foot cloud layer, restoring the necessary line of sight to the visual beacons.
This confirms the unstated cause that necessitated the altitude change.

Key Concept

Recognizing Implied Cause and Effect
Estimated Time:1m 30s
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Recognizing Implied Cause and Effect

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