At what pressure is the lowest usable flight level FL180 recommended?

At what pressure is the lowest usable flight level FL180 recommended?

• A. 29.92 or higher
• B. 29.91 - 29.82
• C. 29.81 - 29.72
• D. Below 29.70

Answer: (A)

The lowest usable flight level is determined based on atmospheric pressure, specifically at flight level 180 (FL180), which corresponds to an altitude of 18,000 feet. The standard pressure at sea level is 29.92 inches of mercury (inHg). When the atmospheric pressure is at or above 29.92 inHg, it is recommended to use FL180 as the lowest usable flight level because it ensures a safe vertical separation between aircraft and the potential for terrain and obstacles below. This is crucial for maintaining safe operational practices in controlled airspace. If the pressure drops below this threshold, operational guidelines suggest that pilots should be cautious, as lower pressures can lead to higher altitudes for the same flight level, potentially compromising safety due to the risk of collision with terrain or other obstacles. Therefore, the recommendation to maintain FL180 is firmly grounded in the need for safety and to adhere to air traffic control requirements. In summary, the choice indicating a pressure of 29.92 inches or higher is based on established aviation regulations that aim to maximize safety by ensuring that the lowest usable flight level remains effective under normal atmospheric conditions.

The lowest usable flight level is determined based on atmospheric pressure, specifically at flight level 180 (FL180), which corresponds to an altitude of 18,000 feet. The standard pressure at sea level is 29.92 inches of mercury (inHg).

When the atmospheric pressure is at or above 29.92 inHg, it is recommended to use FL180 as the lowest usable flight level because it ensures a safe vertical separation between aircraft and the potential for terrain and obstacles below. This is crucial for maintaining safe operational practices in controlled airspace.

If the pressure drops below this threshold, operational guidelines suggest that pilots should be cautious, as lower pressures can lead to higher altitudes for the same flight level, potentially compromising safety due to the risk of collision with terrain or other obstacles. Therefore, the recommendation to maintain FL180 is firmly grounded in the need for safety and to adhere to air traffic control requirements.

In summary, the choice indicating a pressure of 29.92 inches or higher is based on established aviation regulations that aim to maximize safety by ensuring that the lowest usable flight level remains effective under normal atmospheric conditions.