Aircraft hangars – too large to heat?

posted on 27th June 2018

Ambirad specialises in the heating of large spaces – a perennial challenge that needs to be overcome by selecting a heating system that must be both economical and effective. Aircraft hangars have never been easy spaces to heat, but Nick Winton, Nor-Ray-Vac Divisional Manager, AmbiRad Ltd believes the industry now has the answers

When selecting a heating system for aircraft hangars, economy and effectiveness are the two key criteria that specifiers must address. Finding a solution to both in a single heating system can be challenging. However, there is one form of space heating technology ideally suited to the vast volume of the hangar structure – radiant tube heating.

Hangar design can vary greatly depending on the type and size of aircraft it is intended to house, with the roof frequently constructed high enough to allow the complete tail plane within the structure. As such, roof heights can vary from 10m to 30m and consequently the main doors – as well as being the complete width of the hangar – can be virtually as tall as the roof. In many areas of the country, the problem of keeping the hangar warm enough for personnel to work in comfortably is compounded by the fact that most airfields are sited in extremely exposed locations.

An aircraft hangar environment is too hostile for many forms of heating. Warm air heating, for example, is not an appropriate solution. It would not only consume fuel attempting to heat the entire volume of air in the hangar, but the temperature stratification would be enormous. The volume of warm air would also be replaced instantly with colder external air when the doors open to allow aircraft movement in and out. With many commercial aircraft maintenance operations occurring at night, the temperature fluctuations would be considerable. Blanket heat coverage, therefore, is a prerequisite in aircraft hangars. The ideal heating system – one which answers the key requirements of economy and effectiveness – will be capable of heating the complete hangar area, but it should also be zoned to heat specific areas when and where necessary.

Radiant tube heating answers all these needs. It is one of the most energy efficient forms of space heating available; burning fuel (natural gas or LPG) at the point of use so there is no loss of efficiency in distributing heat around the building. Most importantly in the case of aircraft hangars, the warmth from the radiant system felt by personnel is less affected by cold air influx through doors opening and closing. The ability of a radiant heating system to rapidly respond to changed conditions is also paramount.

Radiant systems work in the same way as the sun, emitting infra red rays that will warm only the people and objects in their path. As they do not heat the volume of air in the building, no fuel is consumed wastefully and people still remain warm regardless of fluctuating air temperatures when doors are open and closed. Designed to focus all of their heat exactly where it is needed – radiant tubes will heat the 2m of the building. This enables personnel to feel comfortably warm at all times, while the intense chill is taken off the aircraft structure preventing the build-up of potentially hazardous condensation. When operatives are working in just one area of the hangar, often the case with aircraft maintenance, zoning enables other parts of the system to be switched off. Over time, this produces considerable fuel economies and substantial cost reductions.

At Ryanair’s Prestwick hangar, heated by the Nor-Ray-Vac continuous radiant tube heating system, an under-floor heating system was originally specified, but rejected by Ryanair because of employee discomfort caused by working on a warm floor. Ed Cunningham, Manager of the hangar, said: “We required heating to the hangar with all services installed above a minimum aircraft clearance height.” Subsequently, Ryanair have specified the Nor-Ray-Vac system for two further hangar developments.

Continuous radiant tube heating offers several advantages over linear radiant tubes. The number of burners and roof or wall penetrations required can be kept to a minimum. By providing low intensity, even heat coverage over very large areas, the system is economical, energy efficient and quiet to operate. It can also be easily zoned to fulfil local heating requirements.

Many types of hangars are heated with the Nor-Ray-Vac system, from old World War 2 military hangars to contemporary state-of-the-art hangars – both military and commercial. At RAF Cottesmore in Leicestershire, four old “C” type hangars were decentralised from the high temperature hot water radiant panel system fed by one dedicated boiler house. With enormous distribution losses, the system was burning fuel without producing sufficient heat output. At times, especially during the night or in periods of cold weather, operators worked in single figure temperatures. While far from ideal for the employees, these working conditions also have potentially dangerous consequences should flight safety ever be compromised.

By using data from the base of the excessive operating costs for the existing system, a business case including “whole life costing analysis” was produced for the decentralisation and system replacement with a Nor-Ray-Vac system. Once the existing heating system had been decommissioned, each hangar was equipped with its own Nor-Ray-Vac continuous radiant tube system comprising 24 Nor-Ray-Vac 46kW LR series linear burners with four vacuum fans. Controlled centrally by a Trend BMS, each hangar can also be operated in four separate zones.

Nor-Ray-Vac continuous radiant tube heating has provided the Maritime and Coastguard Agency (MCA) with the unique opportunity to maintain a consistent temperature for two of its helicopter hangars. As the specified heating system for both the Osprey Hangar situated at Portland and the Daedalus Hangar at Lee on Solent, Nor-Ray-Vac provided the MCA with the most efficient and effective solution for the maintenance and storage of its helicopters.

The massive two-bay AirTanker Hangar measuring 147m x 88m was completed on the RAF Brize Norton base as part of the multi-billion pound Future Strategic Tanker Aircraft (FSTA) programme put in place by AirTanker Services working with the UK Ministry of Defence. As the world’s largest Private Finance Initiative contract, FSTA will provide air refuelling and air transport services to the RAF.

The state-of-the-art hangar fully accommodates two of the 14 Airbus A330-200 aircraft for refuelling and aircraft services. With a door spanning 140m wide and 20m high, the specified Nor-Ray-Vac continuous radiant heating system at the front of the hangar is suspended at 23m. From here it progressively follows the roof line to 16.5m high at the back of the hangar. Incorporating 62 Nor-Ray-Vac burners with eight flue discharge points, the system provides each bay with seven separate temperature control zones.

Radiant tube heating is the energy efficient solution for any size of aircraft hangar. With rising fuel costs and restrictions on greenhouse gas emissions, it makes sense to reduce the fuel burden. In the case of radiant heating, this can be achieved without compromising the comfort or safety of personnel. The Nor-Ray-Vac system also qualifies for the ECA (Enhanced Capital Allowance) scheme. This enables the company investing in Nor-Ray-Vac equipment to claim 100% of the equipment and installation costs as capital allowance, in the first year against taxable profits, to provide an upfront tax relief.