SPECIALIST & CRITICAL CARE CENTRE, LLANFRECHFA GRANGE ...planapps.torfaen.gov.uk/Llanfrechfa/Documents... · SPECIALIST & CRITICAL CARE CENTRE, LLANFRECHFA GRANGE ... the AW 139,

SPECIALIST & CRITICAL CARE CENTRE, LLANFRECHFA GRANGE HELICOPTER ACCESS REPORT

Commissioned by BDP Ltd. for the Aneurin Bevan Health Board

by: -Peter Rover, Helicopter Adviser 14, Anglesey Court Road

Carshalton Surrey

SM5 3HZ [email protected]

Tel: 02083957418 May 2012

Llanfrechfa Grange Specialist & Critical Care Centre – Helicopter Access

Prepared by: - May 2012 – Rev 01 Peter Rover, Helicopter Adviser 14 Anglesey Court Road Carshalton Surrey SM5 3HZ Tel: 02083957418 Mobile: 07702664933 Page 1 of 18

1 Introduction: 1.1 This helicopter report, commissioned by BDP for the Aneurin Bevan Health Board, is part

of the submission supporting the planning application for the Llanfrechfa Grange Specialist & Critical Care Centre (LGS&CCC).

1.2 The report will address the options considered for the location of a helipad suitable for the Care Centre as well as detailing the technical specifications required for its design under civil aviation regulations.

1.3 It will further discuss the likely local environmental impact of the helipad due to helicopter operations assuming that the number of movements will be low and will occur at irregular intervals and may occasionally take place at night.

1.4 Helicopter access will be provided for emergencies only. Due to the nature of the emergency use, the exact frequency of helicopter movements is very difficult to predict and any assumptions can only be estimated on best, locally informed judgement. On that basis the Health Board believes it is likely that there may no more than 5 arrivals/departures per week at LG, based on current helicopter use at Neville Hall. For the purposes of the EIA however we have assumed a worst case scenario of three arrivals/departures in any period of 24 hours to allow for the possibility of daily variations and to assess the environmental impact based on this figure.

2 Location Options for Helipad: (See Current BDP Helipad Plan attached to this Report)

2.1 In my earlier report (July 2008), before more detailed plans of the proposed hospital that are now available had been formulated, I recommended that the large field to the East of the site should be the preferred location for helicopter operations. This would have permitted helicopters of all sizes, including the RAF Chinook at 25 tonnes, to operate whilst minimizing the effects of noise and down wash on the surrounding environment.

2.2 This proposal has been shelved because the helicopter touchdown and lift off area where patients would embark/disembark would be too far away from the entrance to A&E and the large field where helicopters would approach to and depart from is not under the control of the Health Board.

2.3 Considering the medical priority is to locate the helipad as close as practicable to the A&E entrance, two other possibilities are now considered; one (Option 2) - North West of A&E on the west side of Ysgubornnewydd Farm (YF) and the other (Option 1) - North East of A&E on the south east side of YF.

2.4 Option 2 is close to a mature copse of trees and the alternative ambulance ‘blue route’ which would complicate a helicopter approach or departure to or from that direction, especially by night. More significantly, with the prevailing wind direction being in the westerly sector between South and North, YF would be down wind of any down wash



effects generated by helicopters close to this helipad location any time the wind was blowing from within that sector. Option 2 is also slightly further away from the entrance to A&E than Option 1.

2.5 Option 1 would be down wind of YF for the majority of the time whilst it is far enough from the front of the hospital to avoid any significant adverse effects from helicopter down wash or noise. The approach and departure flight paths are unobstructed by trees or structures, all of which are either too far away, or below the level of the helipad, and so would not compromise the approach or departure flight path gradients. Option 1 is therefore the preferred option.



3 Helicopter Types, Required Helipad Dimensions and Associated Obstacle Limitation Surface Areas:

3.1 This hospital is likely to attract larger helicopter types from time to time as well as more frequent movements by the smaller Air Ambulance, HEMS and/or Police types. The RAF and RN currently operate the Sea King in the SAR role. This helicopter is 22.2m in overall length, including rotors (‘D’ value) and has a maximum all up weight (MAUW) of 9.3 tonnes. It is likely that this type will remain in service until 2016 when the national SAR role is due to be civilianized and undertaken wholly by the Maritime Coastguard Agency (MCA) using civil registered aircraft and civilian flight crews.

3.2 The MCA currently operates the AW 139 from bases in Lee-on-Solent and Portland. This aircraft has a ‘D’ value of 16.66m and a MAUW of 6.4 tonnes. Re-organisation of the SAR Force by 2016 will probably see the entry into MCA service of the Sikorsky S92, alongside the AW 139, whilst the military will probably replace the Sea King with the S 92 also at, or about the same time. The S92 has a ‘D’ value of 20.88m and a MAUW of 12.8 tonnes, about the same size as, but 3.5 tonnes heavier than the Sea King.

3.3 Air Ambulance, HEMS/Police helicopter types are currently all in the so called ‘3 tonne’ class with ‘D’ values of about 13m. It is likely that these types will remain in service for many years to come and may be supplemented in due course by larger types up to the size of the AW 139 which can carry more stretcher patients but, by regulation, requires two pilots by day and night.

3.4 The helipad should therefore be designed to accommodate the Sea King as having the larger ‘D’ value and the S92 as having the heavier MAUW. All other types likely to make use of a facility suitable for the Sea King and the S92 will be easily accommodated. The one exception will be the Chinook which at nearly 25 tonnes should not be permitted to land anywhere close to the hospital but instead, if necessary, should land in a field well away from any structure, vehicles or people likely to suffer from its excessive down wash effects.

3.5 The minimum required helipad size is dictated by the aircraft manufacturer when space is at a premium and the helipad is the only area suitable for a forced landing, in the event of failure of a power unit. A series of simulated single engine landings is carried out by the manufacturer during the certification process to determine this and the area is expressed in terms of a minimum length and width in the helicopter flight manual (HFM) performance section. Since this forms part of the Certificate of Airworthiness for the aircraft type, compliance with terms of the HFM performance and limitations sections are obligatory.

3.6 In some case, usually older helicopter types including the Sea King, such data may not be included in the HFM; in these cases the International Civil Aviation Organisation (ICAO) provides alternative guidance in the form of standard operating procedures and recommended practices (Annex 6) and design specifications (Annex 14, Vol II, - Heliports). These require that the minimum size of helipad, when not specified in the HFM, shall be



not less than 1 x ‘D’ and that the shape may be square or circular provided a circle contains the minimum length and width of the ‘D’ value.

3.7 The minimum size of helipad at SCCC, based on the Sea King and S 92 should measure not less than 22.2m x 22.2m which will be large enough also for the S92. If circular, the diameter should be not less than 31.39m. The surface should be load bearing and preferably a hard standing area or at least short grass over a consolidated sub base capable of withstanding the dynamic load of a ‘crash’ landing by the heaviest design helicopter type. In this case the S92 is the heaviest at 12.8 tonnes, resulting in a possible ‘worst case’ dynamic load on the helipad surface of approximately 38.5 tonnes.

3.8 On a surface level helipad there is no need for special drainage, provided any fluids drain away from the helipad centre which can be assured by appropriate profiling of the hard surface base. If concrete is used the base should be Portland cement at least 200mm thick and the slope in any direction should not exceed 2%. It is recommended that the concrete surface should be lightly brushed to ensure good non slip conditions and that all paint markings should be of the non slip variety but not thermo- plastic (road marking) applications which can become detached in time under down wash wear and tear conditions, possibly resulting in hazard to life, limb and vulnerable property in the vicinity.

3.9 The helipad should be surrounded by an obstacle free (not more than 250mm above helipad surface level) safety area (SA) extending to cover an overall area of 2 x’D’ = 44.4m.

3.10 The area affected by down wash depends on the weight of the helicopter, the size of the rotor disc and the strength and direction of the ambient wind at the time. In still wind conditions it may be assumed that downwash effects will be evident up to 30m from the edge of the rotor disc. In the case of the S92, for example, the rotor diameter is 17.17m; the downwash effect will deteriorate rapidly from the edge of the rotor disc where it is strongest out to a distance of 30m from it, or approximately 40m from the helipad centre, where the effect will disappear altogether. The rate of dissipation is not linear so the effect at the periphery of the area will be close to the ambient wind at the time. When there is a strong ambient wind the effect will extend further downwind from the helicopter, but at 30m away from the rotor disc edge no great increase from the ambient wind should be experienced. A fuller discussion of down wash is included under the environmental section of this report.

3.11 There must be at least two directions of approach available, separated by not less than 150⁰ in order to accommodate a possible ‘baulked landing’ case where the pilot needs to ‘go around’. Both options 1 and 2 would provide for this.

3.12 Additionally, the obstacle limitation surface area (OLS) under and close to the flight paths should be protected from encroachment by obstacles that could compromise the aircraft safety in the event of a single engine failure occurring at any time on the approach or on take-off. A diagram on the following page illustrates the construction of OLS areas for the S92 based on current performance information. Provided the profiles flown are either



vertical or helipad (‘up and backwards’ on take-off) and not ‘clear area’, the vertical gradient may originate at the take-off decision height above the helipad surface and not from helipad surface level. This would only be the case where clear area profiles can be flown which would depend on there being large clear surface areas for a forced landing to be executed safely away from the helipad itself. This is not the case at SCCC at either of the two location options considered in this report.

3.13 The larger helicopter types fly a vertical helipad profile on take-off whereas the smaller air ambulance types employ an ‘up and backwards’ profile. It is this latter profile which demands the most restrictive obstacle environment on the ground within the OLS areas because, in the event of a power unit failure whilst executing the rearwards manoeuvre, the pilot must dive the helicopter to gain forward speed to force land back on the helipad. In doing so the pilot must ensure that the helicopter remains at least 35 feet vertically clear of any obstacle under and close to the flight path. The diagrams on the following pages, taken from the EC 135 HFM and showing the S 92 requirements, illustrate the obstacle restriction requirements for the different types and can be applied as appropriate to all other helicopter types likely to use this facility: -

4 Helipad Markings and Lighting: 4.1 The diagrams on the following page show the standard helipad markings and lighting; the

details of the illuminated wind sleeve, the dimensions of the white cross and red H and the non operational sign.

4.2 When the helipad is non operational, the white cross and red H should be covered with a yellow cross on a red background indicating to pilots that the helipad is out of use. (see Page 6)

4.3 It may be necessary to install obstacle lighting (low intensity, steady red) on the highest part(s) of the new hospital. This can best be assessed visually from the air and from the surface at night once the development is complete.



TYPICAL SURFACE HELIPAD MARKINGS (S92)

9.5m+ x 1m

21m

21M

FATO Perimeter lights – green as per ICAO specification. Flood lights to be Xenon x 6, set normal to preferred flight paths (NE/SW prevailing)

H

3m





Typical Illuminated Wind Indicator





Distance (d) =390m (day) 432m (night)

Helipad – Touchdown and lift off area (TLOF) 21m x 21m load bearing area minimum size surrounded by firm, flat, clear area/obstacle free space to a total of 42m x 42m. (Hard surface will ensure patient trolley access in all weathers)

Obstacle limitation surface area

15% divergence ( 8°32’) (night) 10% (5°43’) (day)

8% slope (4° 35’)

All round obstacle free access should be the aim but, if impracticable, there must be at least two OLS separated by not

less than 150 degrees preferably close to prevailing wind (SW)

Construct template on acetate film or tracing paper as below to scale to determine feasibility of helipad location.

TDP/LDP

Width 120.19m (day) 171.7m (night) Elevation datum level

Not less than 150°

Diagram not to scale based on S92 Dimensions ‘D’ value 20.88, say 21m RD =17.17m Note: Climb out and/or approach gradients may originate at TDP/LDP (30 – 50 ft ahl) when

helipad profiles are to be flown, otherwise should originate at helipad surface level.



5 Environmental Impact of Helicopter Operations: 4.1 Downwash

4.1.1 Helicopter downwash can be quantified and compared with generally high, gusty wind

conditions. A helicopter will displace a mass of air equivalent to its own all up weight, the heavier the helicopter, the stronger the effect will therefore be on the immediate, surrounding environment. The initial velocity of the downwash will be dependent on the speed of rotation of the main rotor in particular and the tail rotor to a much lesser degree. The velocity decreases rapidly with increasing distance away from the rotors and becomes indistinguishable from the ambient wind at about 30m from the edges of the rotors.

4.1.2 Dr. John Leverton’s research paper for Westland Helicopters, presented to the Royal

Aeronautical Society in 1973, estimates that downwash velocities extend to a distance of about 2 to 3 rotor diameters from the helicopter when, owing to natural dissipation, the velocities rapidly decrease. Graphs illustrating typical velocities and comparing them to the Beaufort wind scale and their dissipation rate are shown on the next pages. (Figures 1 and 2).



Figure 1: S92 disc loading = 11.317 lbs/sq. ft. Downwash velocity immediately below disc = 51.5 kt (59.3 mph) - Beaufort scale - Force 10 strong gale. EC 135 T2 disc loading = 7.103 lbs/sq.ft. Downwash velocity immediately below disc = 45kt (51.8 mph) – Beaufort scale – Force 9 gale.



Figure 2

S 92

EC 135



4.1.3 The US Department of Commerce published an analysis of ‘rotorwash’ (downwash) effects in helicopter mishaps in 1991. A graph from the document showing peak velocities generated by an example 4.3Tonne helicopter type is shown at Figure 3 below for information. This is useful because it quantifies the effects and also shows how quickly ‘rotorwash’ (downwash) dissipates with height/distance away from the helicopter generating it.

Figure 3 4.1.4 The duration of downwash peak values affecting the surface, structures or buildings and

facings close to where the helicopter is to land are restricted to short time periods, in the

Note: A 4.5 Tonne helicopter in a low hover would produce a wind effect of 55 kt. at a distance of 40 feet from the rotor centre; this reduces to 15 kt when the helicopter is in the hover at 8 feet above the helipad.



region of 30 seconds or so during the final stages of an approach to land and on subsequent take-off and departure. The vertical and near vertical profiles flown, in order to ensure the aircraft is able to force land in the event of an engine failure, mean that the final part of the approach to land and the initial take-off and departure, are restricted to the helipad area surface itself and near vicinity of the helicopter so that the effects felt elsewhere will be much less significant.

4.1.5 Provided light facing/cladding, vulnerable people and loose objects are not permitted closer

than 30m to the edges of the helipad during the landing or subsequent take-off, no damage to persons or property should be caused by helicopter downwash. Loose dust and dirt, as in windy conditions, can be whipped up and may cause superficial ‘sand blasting’ damage to vehicles parked within 30m of the edge of the helipad. This can be avoided by ensuring the hard surface is washed regularly and kept dust and dirt free.

4.1.6 The conclusion to be drawn from these diagrams is that the effects of downwash from a helicopter on persons or property on the surface at a distance of 30m from the helicopter rotors will be no more than the effects normally experienced on a gusty, windy day and will be localised.

. 4.1.7 The rotor tips create vortices which are erratic in their velocity (direction and speed)

depending on the mass of the helicopter, speed of rotation of the rotor tips and the ambient wind and temperature. This ‘vortex’ effect combined with downwash has been known to cause light or insecure cladding and other light objects and/or structures to become detached at distances up to 30 metres from the rotors. External cladding and light structures in the vicinity of helipads should be robust enough to withstand these effects, secured, or else removed altogether.

4.2 Other Environmental Effects 4.2.1 Environmental questions most frequently asked about hospital helipads include, whether

the helicopter operation will be safe and, what the effect of noise, vibration and fumes from the helicopter might have on hospital personnel and patients near to the helipad and whether the life style of local residents will be significantly compromised by the operation of helicopters.

4.2.2 Safety is assured by the operator’s compliance with the regulatory requirements for

airworthiness of the helicopters as well as the demanding maintenance schedules and mandatory qualification and periodic training for flight and ground crews.

4.2.3 For surface level helipads the risk analysis of a crash occurring when fewer than 10

expected movements (take-off or landing) per day are expected is considered remote, so integral fire and rescue cover is not mandated. The local fire brigade should, as a precautionary measure, be familiarised with the helipad location, how to access it, where



the water hydrants are and how to deal with the helicopter types likely to use it and aviation fuel fires (Jet A-1/Avtur). They should be able to attend in the unlikely event that a helicopter should crash and burn on the helipad. All modern helicopter types are fitted with ‘crash proof’ self sealing fuel tanks which reduces the risk of fuel leakage in any significant quantities even in the worst case scenario whilst the engines are located at some distance from the fuel tanks.

4.3 Noise /Nuisance 4.3.1 Noise and nuisance can be minimised either by locating the helipad on the ground, as far

away from residential areas as possible and, by planning the flight paths to avoid unnecessarily low transits over sensitive areas and by varying the flight paths in and out of the site where feasible. The duration of noise events is short, in the region of 1 minute for an approach and landing or take-off and departure and the frequency of helicopter movements can be expected to be low, probably in the order of two or three a day at most. The absolute levels of noise should be balanced by the infrequent occurrence of such noisy events and particularly by the positive benefit afforded to patients and to the community by being able to transport persons in urgent need of medical treatment to or from the hospital quickly and safely. The public can, and do appreciate the usefulness of a hospital helipad rather more positively than one used for purely personal convenience or commercial purposes.

4.3.2 A formal noise analysis for hospital helipads, in my experience, is neither conclusive nor

probably even helpful because the frequency of movements is too irregular and too infrequent to draw any truly objective conclusions. Public perception is that helicopters are noisy and there is no denying that. The peak noise measurements are in the region of 85 – 100 dbA, similar to police and ambulance sirens for example, but possibly less intrusive. Measured and averaged, as is the standard for noise analyses over a daytime period or a 24 hour period, the overall noise levels are not increased to any significant degree by the occasional helicopter arrival or departure.

4.3.3 The general public will understand that the helicopter is operating for the benefit of the

community in helping to save lives when time is critical and thus complaints about hospital helipads are rare. All that can be said definitively about helicopter noise is that the helicopter types to be used are all noise certificated by law in compliance with ICAO Annex 16 specifications. It will help, and this is the normal situation, to restrict routine air ambulance flights to social, day light hours only, but night time flights should not be prohibited should the need arise.

4.4 Fumes 4.4.1 Sometimes concerns are expressed about fumes possibly entering hospital air conditioning

systems causing unpleasant smells. This can be avoided by careful positioning of air intakes with regard to proximity to the helipad and prevailing wind direction. In this case no effects from fumes should be experienced within the hospital or nearby YF premises.



4.4.2 The following Figure 4, courtesy Dr. John Leverton, shows the composition of exhaust products from typical turbine engines as found in modern helicopter types. Engine technology has continued to improve since this table was compiled so that helicopter engine exhaust emissions are now even cleaner.

Figure 4



4.5 Assessment of Effects on YF Property due to Helicopter Operations:

The preferred location (Option 1) for the centre of the hospital helipad is about 25m from the south east corner of the YF property boundary. The planned flight paths will avoid any over flight of the hospital and YF property and the prevailing winds will place the helipad downwind of the property for most of the time. In light wind conditions or, when the wind is from the south east, it is possible that the south side and south east corner of the property will experience some effects from downwash; this is unlikely to be of any significance when the smaller ‘3 tonne’ air ambulance types are operating. The larger, heavier types could, in adverse wind conditions, have an effect similar to gale force 8/9 gusts, on the edges of the property at this distance from the helicopter rotors. This could be mitigated by erecting a robust fence, about 2 m high on the south side of boundary and along part of the east side of the property. This would shield the property from both downwash, including possible vortex effects as well as alleviating excessive noise created by the heavier helicopters, albeit for short periods of time.



5 Conclusions and Recommendations: 5.1 The preferred location for the S&CCC helipad is Option 1. This location will provide the

closest access to A&E enabling rapid, direct transfer of patients by trolley from the helicopter to the treatment unit with minimal exposure to weather.

5.2 It is likely that the number and frequency of helicopter movements will be low and infrequent and will only be undertaken for urgent medical reasons. Most movements will take place during working hours by day; but the helipad should be equipped for possible night use if and when the clinical circumstances demand such use.

5.3 The prevailing winds in relation to the helipad location should displace any downwash effects clear of both the hospital and the YF property for most of the time. When the winds are from the South or South East a robust fence about 2m high erected along the southern boundary and part of the east boundary should mitigate both downwash and noise effects that might be experienced on the boundaries of the YF premises, as well as providing a screen from view for the residents from the patients arriving/departing.

5.4 Helipad lighting and an illuminated wind indicator should be provided as discussed and shown in paragraph 4. The lighting need only be switched on at night or in poor daylight visibility conditions when a helicopter arrival has been notified and can be switched off again when the helicopter has departed. Light pollution should therefore be minimal and will occur infrequently.

5.5 It is recommended that the helipad be located as shown on the accompanying site plan as Option 1. Helicopter operations, due to their low expected frequency to/from this location can be conducted safely and should cause no undue adverse environmental effects to either the hospital or the YF residents or property.

Peter Rover, Helicopter Adviser