14 CFR § 27.1383

Each required landing or hovering light must be approved.

Each landing light must be installed so that—

No objectionable glare is visible to the pilot;

The pilot is not adversely affected by halation; and

It provides enough light for night operation, including hovering and landing.

At least one separate switch must be provided, as applicable—

For each separately installed landing light; and

For each group of landing lights installed at a common location.