Thursday, July 30, 2009

How to Put Up a Heliport – Part 4: Obstacle-Free Area

Beginning this part and onwards, the standards that will be used on the rest of the heliport topic will be based purely on the standards and recommended practices (SARPs) published by the ICAO.

SARPs are the annexes to the Convention on International Civil Aviation (also known as the Chicago Convention), an international agreement aimed to harmonize aviation rules and regulations between contracting States. Thus, States who have signed into this agreement are obliged to follow the ICAO SARPs.

As per the standards and recommended practices (SARPs) published by the ICAO, the size of the required obstacle-free area depends upon the overall length or width; whichever is greater, of the largest helicopter intended to operate on the heliport. It also depends on the type of helicopter to be operated on the heliport. Please refer to the helicopter’s flight manual to obtain accurate data for the helicopter’s overall length/width.

AS 365 Overall Length

Depending on the type of helicopter (performances classes) and the type of heliport (elevated or surface-level), there are 3 to 4 portions of the required obstacle-free area, these are:

1. The Final Approach and Takeoff Area (FATO)
2. The Safety Area
3. The portion between the Safety Area and the beginning (inner edge) of the Approach-Departure Surface
4. The over-run portion of the FATO (for surface level heliports serving Performance Class 1 Helicopters)

THE FINAL APPROACH AND TAKEOFF AREA (FATO)

The required dimensions of the FATO depend upon the performance class of the helicopter. For heliports to be used by performance class 1 helicopters, the size of the FATO should not be less than the dimensions prescribed in the helicopter’s flight manual.

If there is no specific size requirement of the FATO in the flight manual of a performance class 1 helicopter, the FATO should have the same dimensions as with the heliports utilized by performance class 2 and class 3 helicopters.

When choosing the size of the FATO, as far as practicable, the dimension to be used should be the one which has more stringent requirements.

The FATO can be of any shape, but as a minimum, a FATO is required to have a dimension that should be of sufficient size to contain an area within which can be drawn a circle of diameter not less than 1.5 times the over-all length or width, whichever is the greater, of the longest or widest helicopter the heliport is intended to serve.

FATO Top View

The FATO of heliports that will be used by performance class 1 helicopters should have bearing strength sufficient to accommodate rejected take-offs. One of the reasons for the requirement of an over-run area is that performance class 1 helicopters are normally eligible for chartered commercial passenger flights so their heliport should have an over-run area for rejected takeoffs.

FATO with Over-run

FATO with over-run side view

For surface level heliports, the surface of the FATO should be resistant to the effects of rotor downwash; be free of irregularities that would adversely affect the take-off or landing of helicopters; and should provide ground effect (air cushion between the helicopter rotors and the surface below).

The FATO’s overall slope in any direction should not exceed 3% and no portion of the FATO should have a local slope of more than 5%.

FATO side front back view

THE SAFETY AREA

Surrounding the FATO is the safety area (synonymous to a road shoulder).

For Visual Meteorological Condition (VMC) Operation (day operation with clear visibility), safety areas extend outward from the periphery of the FATO for a distance of at least 3 m or 0.25 times the over-all length/width, whichever is greater, of the largest helicopter the heliport intended to serve.

This means that if the overall length of the helicopter is less than 12 m, the width of the safety area from the edge of the FATO is always 3m. Likewise, if the overall length of the helicopter is more than 12 m, the width of the safety area that extends from the edge of the FATO will be equal to 1/4 of the helicopter’s overall length.

FATO with Safety Area

For Instrument Meteorological Condition (IMC) Operation (night operation, or, day operation with very low visibility), the safety area surrounding a FATO should extend laterally to a distance of at least 45 m on each side of the centre line; and longitudinally to a distance of at least 60 m beyond the ends of the FATO.

FATO with IMC safety area

For both VMC and IMC operation, there should be no fixed object in the safety area except for frangible objects, which, because of their function, must be located on the area (such as heliport lightings). Likewise, there should be no mobile object on the safety area during helicopter operations.

Objects whose functions require them to be located on the safety area should not exceed a height of 25 cm when located along the edge of the FATO. These objects should not also penetrate a plane originating at a height of 25 cm above the edge of the FATO and sloping upwards and outwards from the edge of the FATO at a gradient of 5 per cent.

The surface of the safety area shall not exceed an upward slope of 4 per cent outwards from the edge of the FATO.

Obstacles at Safety Area

The surface of the safety area shall be treated to prevent flying debris caused by rotor downwash. The surface of the safety area abutting the FATO shall be continuous with the FATO and be capable of supporting, without structural damage, the helicopters that the heliport is intended to serve.

BETWEEN THE SAFETY AREA AND THE INNER EDGE OF THE APPROACH DEPARTURE SURFACE

The portion between the Safety Area and the beginning (inner edge) of the Approach-Departure Surface should also be free from obstacles. The surface of this area should be the same surface as with the safety area.

Portion bet FATO and SA

In the illustration above, for a heliport that will serve a helicopter with an overall length/width of more than 12m, the total required obstacle free area will be twice the helicopter’s overall length on each side of the square. The square shown above applies only to bi-directional paths with 180° separation (example: directly north and directly south approach-departures).

For omni-directional approach-departures (meaning the helicopter may takeoff or land at any direction), the square in the illustration will be rotated accordingly. The rotation will yield to a required obstacle-free radius equal to the helicopter overall length divided by Sine 45° (or 0.707107). For example, a helicopter with an overall length of 13 m operating on an omni approach-departure heliport, the required obstacle-free radius of the heliport will be 13 m divided by 0.707107 which is equal to 18.38m radius or 36.77 m in diameter.

Rotated Square

TUTORIAL/EXPLANATION RECAP:

For VMC Surface-Level Heliports serving performance class 1 helicopters, the obstacle-free areas will be:
1. FATO
2. Safety Area
3. The area between FATO and the inner edge of the approach-departure surface
4. Over-run Area

For VMC Elevated Heliports serving all classes of helicopters, the obstacle-free areas will be:
1. FATO
2. Safety Area
3. The area between FATO and the inner edge of the approach-departure surface

For IMC Surface-Level Heliports serving performance class 1 helicopters, the obstacle-free areas will be:
1. FATO
2. 90 m wide Safety Area that extends 60 m longitudinally beyond the ends of the FATO
3. The area between FATO and the inner edge of the approach-departure surface
4. Over-run Area

For IMC Elevated Heliports serving all classes of helicopters, the obstacle-free areas will be:
1. FATO
2. Safety Area
3. The area between FATO and the inner edge of the approach-departure surface

Next -> Part 5: Approach-Departure Surfaces

2 comments:

awakening said...

Hi Ian,

As you pointed out during my consultation with you last week, we need to be assured that the heliport that we will construct is in accordance with the accetable specifications of CAAP to be eligible for registration. That is why i was asking if there is a company or individual that we can consult or may be able to help us construct the heliport or construct the heliport for us.

I hope you can give me some recommendations.

Thanks Ian,

Deody Solee
Zambales Diversified Metals Corp.

Ian W. Echavez said...

@Deody,

Sorry, I don’t know any Philippine Consultation Firm that really knows international standards for heliports. If you have noticed the Google Ads in my webpage, it also advertises Aviation Consultancy Firms. I don’t have direct control to these advertisements but I think I saw once a Heliport Consultancy Firm displayed on these Ads. If you want to employ their services, it is probably cheaper to just purchase a detailed heliport plan based on your preferred type of helicopter, the topography of the area and the obstacles surrounding the proposed heliport.

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