Helicopter operations and pilot training in a desert environment requires an aviator to understand the limitations of the aircraft and how visual aspects and personal stress contribute to the challenges of flying. The US Military gained a great deal of information both from the successes and from the failures of Desert Storm/Desert Shield resulting in advanced training and new technology. Desert Helicopter Operations: Military Specific A typical desert environment is unpredictable, potentially violent, and does not follow any particular terrain model.Weather conditions consist of extreme highs, sandstorms, and fluctuating wind speeds; making flight operations extremely unsafe for aviators without adequate training.
Since Desert Storm/Desert Shield, the United States Military has taken the experiences and mistakes that were made and used them to improve desert training for its future aviators. This training benefits all sectors of civilian, commercial, and public aviation. Yet even with experience, desert operations can still catch the most experienced aviator off guard; making it utterly important that aviators without experience have the knowledge to overcome the worst scenario.The most important factors for an aviator to understand in desert operations are the environmental effects on the aircraft, visual illusions and effects during flight, and the different kinds of stress experienced during flight. Environmental Effects on Aircraft When operating within a desert environment, considerations must be taken to include the effects of extreme temperatures and its direct relation to aircraft performance. Extreme temperatures are the greatest power-limiting factor and are one of the leading causes for aircraft malfunction in a desert environment.
Flight physics show that when there is an increase in air temperature there will be a decrease in air density. A decrease in air density ultimately means less air to create lift and less air to cool the engine. In this condition, a helicopter’s performance is limited by decreased maximum payloads and lowered maximum torque availability; prohibiting normal maneuverability. Most of this can be managed through training, the effective use of power management, and ultimately experience.
The majority of aircraft accidents are a result of pilot error even though malfunctions do occur. In the military sector where operations are commonly flown between 80 and 200 feet above the highest obstacle, aircraft malfunction coupled with a pilot error is deadly. In low-level flights, the pilot has a limited amount of time to react to aircraft malfunction or environment change. Some of the more common solutions are to fly at higher altitudes to allow more time for reaction and/or slower airspeeds so as not to push maximum torque availability. Aircraft MalfunctionsSome of the prominent aircraft malfunctions consist of electrical problems, instrument misreading, over heating engines, or a loss in turbine compression.
All of which can be caused by extreme heat and sand. In the desert environment, sand is the root cause for most high aircraft maintenance costs. Most of this damage occurs when the sand is ingested through the turbine. It acts like sand paper as it brushes against internal surfaces. Over time, sand abrasion will alter the aerodynamics of internal airfoils; resulting in a loss of engine efficiency, overall performance, and eventually end in a catastrophic engine failure.
Over heating can cause similar problems when there is inadequate cooling or when the engine is over torqued. A report published by Pratt and Whitney in 2006 demonstrated that sand abrasion is a potential factor in turbine overheating. Research has shown that in some cases where the leading edge of airfoils reached extreme temperatures, sand was more likely to melt and adhere to the surface. These “hot spots” within the turbine decreases the service life. Further research indicates that six hours of sand ingestion is enough to decrease turbine efficiency by 7% (Joe, 2006).With the way technology has progressed over the years, most modern day military aircraft has moved away from conventional steam gauges as a primary instrument.
Instead most aircraft have been fitted with glass cockpits and electronic equipment as a primary means to display essential instruments. However, with more electronics on board there is a greater risk for malfunction under extreme heat conditions resulting in fried components, short-circuiting, and computer processing lag.Fortunately, most problems are found while aircraft are on the ground because a stationary aircraft has greater chance of heating up while a moving aircraft has a constant airflow to cool it down. Visual Illusions and Effects During Flight The greatest number of accidents are caused or related to visual effects during flight; otherwise known as pilot error. Statistics during desert operations from 1995 through 2002 show 67% of pilots over a hundred hours or six months of flight will experience an accident - five out of nine are brownouts and two out of nine are depth perception/disorientation (Desert Flying and Safety Considerations, 2002).Brownout, in aviation terminology, is an in-flight visibility restriction due to rotor downwash lifting loose particles into the air, which engulfs the aircraft in a cloud.
This is a problem that has faced engineers and aviators for the last 13 years since Desert Storm/Desert Shield. Reports show that in the event of a brownout, aviators often put aside training and follow they’re instinct. Visual illusions, stress, and panic are a deadly combination.More times then not, if the aviator continued their approach, they would have made a sufficient landing. However, the common tendency in this situation is to panic and pull up on the collective creating a larger cloud of sand. Because the pilot is already disoriented, this leads to a rollover or an aggressive forward pitch of the aircraft, dipping it into the ground below.
In most cases, if the pilot were able to transition or at least reference the instruments, most brownout accidents could be avoided.Sandblaster Technology New technology developed by Sikorsky Aircraft along with its teammates Honeywell International and Sierra Nevada Corporation was successfully demonstrated in January 2009. This new technology was named the Sandblaster and it integrates four key technologies: “fly-by-wire flight controls with point-in-space approach capability, millimeter-wave radar, a digital terrain knowledge grid, and a low-speed cockpit symbology” (Colucci, 2009). When put together these technologies have the ability to enhance the pilots outside awareness, which becomes useful during an event where outside visibility is limited.Sikorsky’s Sandblaster technology allows the pilot to view the associated terrain within the landing zone through a 3-D illustration and alerts the pilot of all potentially hazardous obstacles, slope, or uneven terrain. Most common illusions.
Some of the more common illusions that pilots will experience in desert environments are false horizon, height perception illusion, ground light misinterpretation, fixation, crater illusion, and lack of motion perception. However, the top three illusions that effect a pilot’s judgment the most during desert flight are height perception illusion, fixation, and lack of motion perception (Allmen, 2003).Height perception illusion is a sensation of being higher than the actual altitude being flown due to the lack of visual reference and poor contrast. This illusion will cause the pilot to correct and descend in altitude.
If the pilot is already flying at a low-level altitude, this will increase the chance for a collision. Fixation usually occurs in a low visibility flight when the pilot fixates on a single instrument instead of scanning all critical instruments to make a judgment.Lack of visual reference has the opposite effect of fixation when the pilot does not focus on anything in particular but is in a daze-like state. Flying in this condition will also foul pilot sensation into thinking he/she is flying slower then reality.
It is critical that the pilot pay attention to the instruments, terrain, and obstacles in order to avoid accidents that often occur at low altitude with a lack of discernible terrain features. Stress Experienced During Flight In desert operations, there are many ways that safety can be hindered by personal stress resulting in loss of life and aircraft.Some of the more common stress factors that pilots rated to be most difficult are: 58% brownouts, 12% multiship operations, 12% physiological (heat), 6% navigation, 6% terrain flight, and 6% terrain interpretation (Desert Flying and Safety Considerations, 2002). If performed on a frequent basis, the increased experience will often result in overcoming the stress associated with each task. Such tasks should be learned with ease and not pushed on a pilot unless comfortable with the task.
No task should be performed for long durations of time or in frequent intervals without adequate recovery.Otherwise, an aviator’s ability to concentrate and make effective decisions will become compromised. This is known as chronic fatigue. Heat Effects on Humans Extreme heat is one of the biggest issues effecting pilot performance.
Heat can cause dehydration, heat stroke, exhaustion, and heat cramps. The body normally sweats 1 pint to 1 quart a day, but under heat stress, the body can lose 3 to 4 quarts in a day (Aeromedical Training for Flight Personnel). In summation, flying in desert conditions is dangerous. With the development of new technology and improved training, the US Military has come a long way since Desert Storm/Desert Shield.
