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May
09
2014
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Posted 10 years 200 days ago ago by Admin
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PERSONAL PROTECTIVE EQUIPMENT (Part One)
By Dr. Dudley Crosson
It doesn’t matter what you call it – Personal Protective Equipment (PPE) or Aviation Life Support Equipment (ALSE) – it is all the same. It is the equipment that the flight crew should be using to protect them from conditions that may occur during an accident. It is common practice to utilize ALSE in the public safety and HEMS communities, but it is obvious that not all do so. Another observation is while most use ALSE, not all use it properly. Many pilots took the path of civilian training and most likely did not receive training on PPEs. Others went the military route and received proper training. Over the years, those properly trained may have modified procedures a little for the sake of comfort or expediency of application. This is certainly understood and appreciated. However, we cannot lose site of the intent, or necessity, of proper use.
As an Aeromedical Safety Officer (AmSO), I want to present this topic from a slightly different perspective – a mitigation perspective. There is no reason for someone to go into a career in aviation and expect to retire with hearing loss. If unfortunately someone is involved in an accident, there is no reason for injuries to occur because the helmet was not fit properly, or the flight suit did not fit or was not worn properly, or because gloves and good boots were not worn. There is no doubt that wearing PPE properly in the middle of summer can be uncomfortable, but like insurance, it is needed.
This is a two-part article. Part one will address helmets and their related accessory devices, while part two will look at the rest of the equipment.
Helmets
The helmet is considered by some to be the most important PPE worn. In some ways this may be true, but there are a few more considerations than just wearing it. One needs to also consider proper fit and characteristics for both short-term health, such as survivability and shock absorption, and long-term health for hearing loss mitigation and myalgia (muscle pain) mitigation.
First, let us look at the short-term health aspects of the helmet. This seems to be the only aspect that most crews consider when looking for a helmet. This is certainly the most impressive aspect, and is supported by a study by Taneja and Wiegmann (2003). They “analyzed patterns of injuries sustained by pilots involved in fatal helicopter accidents from 1993 to 1999 by reviewing the FAA’s autopsy database.” This database included all helicopter accidents, not just public safety. A couple of very impressive details to come from this were that skull fractures were the second most common causes of blunt force trauma: 51% of the cases. In addition, the brain was the most common (62%) of the organ/visceral traumas. This study looked at all the cases, including public safety, HEMS, and tourism as well. From the report it is safe to assume that those not wearing helmets had the most trauma.
A common question is which helmet is the best? I do not believe there is a ‘best,’ but several that are options. There are a number of acceptable helmets to select from, including the HGU-56P –(top left and current military issue), HGU-84, SPH-5 (bottom left), Alpha Eagle series (Alpha Eagle 250, top right), and the Gallet series (bottom right). As in any case, there are pros and cons for each. When making a selection, it is important to look at supporting test data to see how it compares with others. Certainly the HGU-56P goes through the most stringent testing, but that does not necessarily mean it is the best for your needs.
Whatever the selection criterion is, once the helmet of choice is purchased it needs to be properly fit. Meaning, it is important to follow the manufacturer’s recommendations. In one case, a mold of the top of the head may be made and sent to the manufacturer prior to delivery of the helmet so that they may do the initial fit/sizing. After that, fine-tuning may be done in order to eliminate any ‘hot spots’ and get the ‘perfect fit.’ The reason this is emphasized is that without a good fit, the helmet will be uncomfortable and at the very least the wearer will suffer through the flight, and worst case the helmet will not be worn. After wearing the properly fit helmet for a couple of months (especially through hot months), check the fit again. Straps tend to stretch and internal padding tends to form. A simple test is to reach back and grasp the base of the helmet and pull forward. If the helmet slides off the head, it is too loose. Related to this is the common mistake of users not tightening the nape strap. When all is done, with a secure neck and nape strap, the helmet should be comfortable enough to be worn for a few hours at a time.
Visor down
Once the helmet is fit properly and in use, it is critical to remember to ALWAYS have a visor down, either the tinted one or the clear one. This is mostly due to bird strikes, but other times it is important as well such as when a crewmember is on the skids during hoisting operations. There are no sunglasses that protect against that much impact. If the helmet of choice is the Gallet 250, ask the manufacturer to place the clear visor on the inside. The reason for this is that many individuals find they can have this visor down and still be able to wear NVGs at night.
Preventing long-term health consequences
Now that short-term health has been addressed, we need to consider long-term consequences. It is very rare that users consider this when choosing a helmet. The most common issues are hearing loss, neck/back pain, and/or neurological damage. Let us look at noise first. The helicopter crew is exposed to a wide range of frequencies: engine(s), drive shaft, transmissions, rotors, and propellers. The Surgeon General has established 85 dBs as the maximum level of continuous, unprotected exposure to steady-state noise for eight hours. Obviously no helicopter operates at 85 dBs, so hearing protection is needed, which mostly is the helmet. Proper fit also helps here because of the fit of the ear cups and insulation of the helmet. Hearing protection is an area where helmets vary greatly.
There is a supplementary way to help protect against damaging noise, and that is by also wearing earplugs. Certainly if funding is available, communication earplugs (CEPs) are an option. They are essentially foam earplugs with holes drilled through them length-wise and speakers inserted. While communication is clear, and often the volume can be turned down, some crewmembers feel that CEPs put pressure inside the ears. Thus, their suitability is a personal preference.
The ultimate hearing protection is active noise reduction (ANR). This is built into the helmet, and works by 180-degree out-of-phase noise to cancel ambient noise. Essentially it cancels any undesirable noise by superimposing an inverse sound wave.
Another long-term health issue is that of neck and/or back pain. Just by virtue of having to wear a helmet weighing between two and four pounds for a long period of time, this should be expected. Combined with this weight is the head movement associated with flying a helicopter, often times looking down and to the side. Lastly for those using NVGs, these goggles add weight. Individuals who have been flying for several years commonly have neck and/or back pain. Some experience pain only when flying, while others experience it all the time. Neck exercises are certainly warranted in order to avoid such pain. Another aid is to utilize something commonly worn by NASCAR drivers to support their helmets – a Nomex® neck support. It is similar to a pillow that wraps around the neck, often used by travelers on planes. However, Nomex® is firmer and supports the weight of the helmet without limiting turning of the head.
Helmets, and their related equipment, are a critical component of crewmembers’ PPEs. When thoroughly researched, intelligently selected, and properly fit, they are much more tolerable and effective. Part Two of this article will look at flight suits, boots, gloves, and other protective gear.
References
Taneja, N. and Wiegmann, D. “Analysis of Injuries Among Pilots Killed in Fatal Helicopter Accidents,” Aviation, Space and Environmental Medicine, 2003; 74 (4): 337-41.