2024 14 CFR 77.23 – Heliport imaginary surfaces

2023 14 CFR 77.23 – Heliport imaginary surfaces

2022 14 CFR 77.23 – Heliport imaginary surfaces

2021 14 CFR 77.23 – Heliport imaginary surfaces

2020 14 CFR 77.23 – Heliport imaginary surfaces

2019 14 CFR 77.23 – Heliport imaginary surfaces

2016 14 CFR 77.23 – Heliport imaginary surfaces

2015 14 CFR 77.23 – Heliport imaginary surfaces

2014 14 CFR 77.23 – Heliport imaginary surfaces

2010 14 CFR 77.23 – Standards for determining obstructions

2009 14 CFR 77.23 – Standards for determining obstructions