Touchdown and Lift-off Area (TLOF)

Definition

A touchdown and lift-off area (TLOF) is a load-bearing area on which a helicopter touches down or lifts off.

The FAA calls it a load-bearing, generally paved, area normally centred in the FATO (AC 150/5390-2D, 1.8.46). EASA defines it as an area on which a helicopter may touch down or lift off (CS HPT-DSN.A.020). Every heliport has at least one. The heliport page covers the whole facility. This page covers the TLOF alone.

TLOF, FATO, safety area and helipad

Four terms for the areas at a landing site are easy to confuse. Each has its own job.

TLOF. The area under the helicopter at touchdown and lift-off. It carries the load.
Final approach and takeoff area (FATO). The defined area over which the pilot completes the final approach to a hover or a landing. Take-off starts from it. The FAA says the FATO and the TLOF are normally co-located but may be separate. The FATO page covers it.
Safety area. The area around the FATO that reduces the risk of damage to a helicopter that diverges from the FATO by accident. EASA says it is free of obstacles other than those needed for air navigation. It need not be load-bearing (FAA 2.9.2).
Helipad. A small designated area, usually with a prepared surface, used for take-off, landing or parking of helicopters. The helipad page covers it. A helipad is a different idea from the TLOF, because it can also be a parking area.

Where the TLOF stands

EASA says to place one TLOF within the FATO, or to place one or more TLOFs with helicopter stands (CS HPT-DSN.B.120(a)). If the FATO can contain a circle of more than 1 D, keep the TLOF centre at least 0.5 D from the FATO edge (B.120(b)(5)).

The FAA lets a TLOF stand at ground level, on an elevated structure or on a rooftop. A TLOF within the FATO is centred in it (2.7.1). A ground-based or water-based TLOF can also stand outside the FATO. The FAA then asks for a taxi route or hover taxi capability. It does not allow this for rooftop operations.

Size

The size depends on D, the largest overall dimension of the helicopter with the rotors turning (CS HPT-DSN.A.020). EASA says that a TLOF should contain a circle of at least 0.83 D of the largest helicopter that the area serves (B.120(b)(1)). The FAA uses the same factor and adds minimums by heliport type (Table 2-1):

Heliport type	TLOF width and length	FATO width and length
General aviation	0.83 D	1.50 D
Transport	0.83 D, at least 15.2 m (50 ft)	1.66 D, at least 30.5 m (100 ft)
Hospital	0.83 D, at least 12.2 m (40 ft)	1.50 D

The FAA also asks for a gap of 0.34 D between the TLOF edge and the FATO edge. As an example, a helicopter with D = 12 m needs a general aviation TLOF of at least 9.96 m (0.83 x 12 m).

Strength

EASA separates two cases. A TLOF within a FATO should be dynamic load-bearing. EASA defines a dynamic load-bearing surface as one that can support the loads of a helicopter that makes an emergency touchdown. A TLOF at a helicopter stand should be static load-bearing, which means that it supports the mass of the helicopter (B.120(b)(2) and (3)).

The FAA design static load equals the maximum take-off weight of the design helicopter. The design dynamic load is 150 percent of that weight. A load of 0.2 second or less can occur in a hard landing (2.7.3.1 and 2.7.3.2).

Surface and slope

EASA says the slopes should prevent water from collecting on the TLOF and should not exceed 2 percent in any direction (B.120(b)(4)). The FAA asks for a negative gradient of 0.5 to 2 percent on general aviation and hospital heliports. On a transport heliport the longitudinal gradient is 0.5 to 1 percent, and the transverse gradient is 0.5 to 1.5 percent (2.7.5).

The FAA prefers Portland cement concrete for a ground-level TLOF. It says that asphalt may rut under the wheels or skids of a parked helicopter, which has been a factor in some rollover accidents. It also asks for a broomed finish for skid resistance (2.7.4).

Markings

Heliport identification. For a general aviation or transport heliport, the FAA marks the TLOF with a white “H” at its centre (4.3). EASA asks for a white “H” at the centre of the FATO. It coincides with the centre of the TLOF when the FATO contains one (CS HPT-DSN.F.520). A hospital heliport can use a red “H” in a red cross instead (FAA 4.3.2).
Perimeter. The FAA defines a paved TLOF with a continuous white line 0.3 m (12 in) wide (4.4.1). EASA asks for a continuous white line at least 30 cm wide, where the perimeter is not self-evident, on a TLOF in a FATO (F.560).
Touchdown and positioning circle (TDPC). Both sources use a yellow circle. Its inner diameter is 0.5 D and its line is at least 0.5 m wide. It sits at the centre of the TLOF. When the pilot seat is over the circle, the undercarriage is inside the TLOF (FAA 4.4.2, EASA F.570).
Size and weight limit. The FAA marks the D value in a box on the TLOF. Where the load is limited, the box also shows the maximum take-off weight. The numbers are black on white (4.4.3).

Lights

A heliport that operates at night needs a TLOF lighting system. EASA allows perimeter lights or floodlighting. It also allows luminescent panel or segmented point source lighting where the first two are not practicable and FATO lights exist (CS HPT-DSN.F.690). The FAA lights a heliport for night operations, or for instrument operations by day, with TLOF perimeter lights (4.13).

Item	EASA CS HPT-DSN.F.690	FAA AC 150/5390-2D, 4.13.1
Colour and type	Fixed omnidirectional, green	In-pavement green L-852H, or as an option elevated green omnidirectional
Square or rectangular TLOF	At least four lights per side, including each corner. Spacing at most 5 m	At least four per side (three at hospital and private-use heliports). Spacing at most 7.6 m (25 ft). An odd number per side
Circular TLOF	At least fourteen lights in the evenly spaced pattern	An even number, at least eight, evenly spaced
Position	Along the edge, or within 1.5 m of it	In-pavement within 0.3 m (1 ft) of the edge. Elevated within 3 m (10 ft) outside the edge
Height	At most 25 cm. Inset where a raised light would endanger helicopters	At most 51 mm (2 in) above the TLOF plane

The FAA says that floodlights do not replace TLOF lighting (4.13.4).

Elevated TLOFs

The FAA defines an elevated heliport as one on a rooftop or other elevated structure. Its TLOF is at least 0.8 m (30 in) above the surrounding surface (1.8.6). At a general aviation or hospital heliport the TLOF stands above the FATO elevation. It also stands above any obstacle in the FATO or safety area that cannot be removed (Table 2-3). The structure under an elevated TLOF must carry the dynamic load (2.7.3.2). The FAA recommends fall protection for a platform 0.8 m (30 in) or more above its surroundings (2.10).

What it means on an airfield

The perimeter lights and the markings of a TLOF are visual aids, like those of a runway. The two sources set the colour, the place and the spacing of each one. They do not say how to inspect them. TarmacView’s drone airport inspection inspects airfield lights. Ask whether the method fits your heliport.

Frequently Asked Questions

What is a TLOF at a heliport?

A touchdown and lift-off area (TLOF) is a load-bearing area on which a helicopter touches down or lifts off. The FAA says it is normally centred in the final approach and takeoff area (FATO). EASA defines it as an area on which a helicopter may touch down or lift off.

What is the difference between a TLOF and a FATO?

The TLOF is where the helicopter touches down. The FATO is the larger area over which the pilot completes the final approach and from which take-off starts. The FATO is at least 1.50 D wide for a general aviation heliport in the FAA rules, and the TLOF is at least 0.83 D.

How big is a TLOF?

EASA says a TLOF should contain a circle of at least 0.83 D. D is the largest overall dimension of the helicopter with the rotors turning. The FAA also gives 0.83 D. It sets a minimum of 15.2 m (50 ft) for a transport heliport and 12.2 m (40 ft) for a hospital heliport.

What colour are the lights of a TLOF?

The perimeter lights of a TLOF are green. EASA specifies fixed omnidirectional green lights. The FAA specifies in-pavement green lights of type L-852H, or as an option elevated green omnidirectional lights.

What markings does a TLOF have?

A TLOF has a white H at the centre for a standard heliport. A TLOF in a FATO has a white perimeter line when its edge is not self-evident. A yellow touchdown and positioning circle shows where the pilot seat should be. The FAA also marks the size and weight limit.

Does every heliport need a TLOF?

Yes. EASA says at least one TLOF should be provided at a heliport. The FAA says every heliport has at least one TLOF. EASA places one TLOF within the FATO, or places TLOFs with helicopter stands.

Can a TLOF stand outside the FATO?

Yes, in the FAA rules, for ground-based or water-based operations but not for rooftops. The FAA then asks for a taxi route or hover taxi capability. EASA also allows TLOFs at helicopter stands, and these are designed for static loads.

This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.

What is a Touchdown and Lift-off Area (TLOF)?