What temperature condition requires altitude corrections for all altitudes on an Instrument Approach Plate?

When evaluating temperature conditions that necessitate altitude corrections during an instrument approach, it's important to note that the standard atmosphere assumes a particular lapse rate where temperature decreases with altitude. Typically, a temperature deviation from this standard—particularly when the temperature is colder than expected—can influence aircraft performance, specifically in relation to density altitude.

In this scenario, temperatures that are significantly lower than standard can lead to a situation where the aircraft descends through more dense air than anticipated, which affects the actual altitude relative to the indicated altitude. For instance, at -30°C, the need for altitude corrections becomes critical because this is a point where the standard performance tables and figures provided on the Instrument Approach Plates no longer remain valid.

Under -30°C, pilots must adjust their altitude to ensure safe and accurate approach and landing profiles. This correction helps to compensate for the increased density, preventing the aircraft from being at a higher actual altitude than what is displayed to the pilot. This understanding is crucial for maintaining safe operational standards and ensuring precision in instrument approaches.

As temperatures continue to decrease beyond -30°C, while corrections are still necessary, the standard corrections and guidance offered in the relevant manuals significantly emphasize this temperature specifically due to the commonality of operations at this threshold.