Protecting your investment - shielding helicopter engines from airborne threats
Brought to you in partnership with Pall Aerospace. If you would like to discuss any of the topics covered in this article with the company directly, click here.
It is a truism that more nations have successfully developed a space programme than have put an indigenous helicopter design into series production.
Due to the inherent complexity of the helicopter design, ‘the genius of the machine’ is in the degree of attention original equipment manufacturers and component suppliers alike apply to ensuring the reliability of its smallest parts.
One such company is Pall Aerospace, which has been a key supplier to the aviation industry since the 1940s and today continues to offer a broad range of commercial rotary wing contamination control solutions that protect helicopter systems and key components in harsh operating environments.
As Chris Savage, Vice President of Technology at Pall Aerospace explains shielding helicopter engines from airborne threats such as sand, dust, salt, heavy rain, ice and snow, and foreign objects (FOD) brings immediate operating cost savings in addition to the obvious safety advantages.
‘Having engine inlet protection is something to consider for both safety and maintenance cost reduction, and even if you only operate from hardstand to hardstand in perfect weather conditions, bird strikes, FOD and atmospheric dust are all conditions that can affect your engine life,’ Savage says.
‘As we all know, engine overhauls are the most expensive cost consideration in helicopter maintenance and blade erosion or damage affects both balance and power. Consider for a minute that every automobile on the road has an air filter installed to maximize engine life, and most drivers never stray far from paved surfaces, but most helicopters are operated with no engine air filtration regardless of where they operate. This doesn't seem logical when you consider the cost of operating an average helicopter compared to an automobile.’
A range of engine protection systems are currently available, each offering varying levels of protection and advantages.
At one end of the spectrum are rudimentary debris screens, which are little more than a course wire mesh in front of the engine to keep the largest of debris from entering the engine but do little to prevent dirt and sand being ingested into the engine.
Integrated Particle Separators (IPS) and Dust Protection Units (DPUs) offer somewhat more protection from dirt and sand while providing essentially the same protection as a debris screen against bird strikes and fog.
However, while IPS systems have a typical removal efficiency of 85 to 95% for coarse sands, this lowers to just 65% for fine sands, according to a NATO Research and Technology Organisation (RTO) report. DPUs offer a similar level of protection.
One alternative approach is the use of cleanable Inlet Barrier Filters (IBFs), which are air-penetrable physical barriers installed in front of the engine to collect various small particulate contaminants from the air stream, passing clean air through to the engine.
The advantage of Pall’s cleanable barrier filters is that they contain a dry media, rather than an oil wetted media, which can be easily cleaned with either water or air for increased helicopter availability at a lower maintenance cost.
Another more advanced solution is the use of high-performance vortex generator tube systems, such as those featured on Pall Aerospace’s PUREair Vortex System technology.
Vortex systems employ a large number of small diameter vortex tubes in a panel to clean the air.
The contaminated air enters the vortex tube, in which uses centrifugal force spins the solid contaminants to the outside of the tube enabling separation. The contamination is removed from the system by scavenge airflow while the clean air in the centre of the tube is then allowed to pass through to the engine.
The benefits of vortex systems include excellent dust separation efficiency; a significant reduction in engine erosion and component wear; and reduced maintenance and operations costs.
The demonstrated efficiency of the PUREair system versus an IPS system in testing saw Pall’s vortex filtration adopted as standard on the RTM-322 engines that power the NH90 helicopter and the system is now used on more than 50 different helicopter types.
‘For the sake of comparison, an oil wetted inlet barrier filter in the same condition as the RTM-322 vortex system test would have required cleaning 300 times and the IBF would have required replacement at least 20 times,’ Savage says.
‘With an oil wetted IBF, the test would have stopped every two minutes for barrier filter maintenance. With the PUREair system, it went all the way through without interruption. PUREair systems are the best choice to ensure operational readiness at all times.’
While vortex systems are highly efficient at removing most particles, and preventing water and fog ingestion, fine particulates of less than six micron in size have a slightly higher probability of passing through the vortex system into the engine. If very fine sand particles are a concern in your operating environment, the use of IBFs may be more suitable.
Ultimately, choosing the optimum type of engine inlet protection solution depends on how an operator balances a range of factors – the operating environment, requirements to fly in extreme weather conditions, consistency in engine performance, initial procurement as well as inventory costs, and maintenance time and costs.
Brought to you in partnership with Pall Aerospace, which will be exhibiting at Heli-Expo 2019. To discuss which engine air protection option works best for you, be sure to visit this team of contamination control experts at stand B6726.