RETIRED CHIEF WARRANT OFFICER 5 DENNIS MCINTIRE
Fort Worth, Texas
Helicopters today conduct operations in environments and at tempos far different from what was envisioned years ago. Brownout was inconceivable while patrolling the East German border back then. It has only been in recent years, with the wars in Afghanistan and Iraq, this problem comes to the forefront.
Dust landings — the effect of swirling dust and debris caused by the rotor wash during the landing of a helicopter — will challenge the best aviators. In heavy dust, brownout is not a question of “if,” but “when.” The “if” is a given, while the “when” is a factor we have little control over.
It’s important to understand that the dust generated during the landing phase doesn’t cause a true brownout until the vortices bring the heaviest dust through the rotor system. If you can be in a touchdown position before that point, your landing will be easier and much safer. Additionally, you must understand the direct correlation between the aircraft angle of approach and the rate of descent as it applies to the ground roll/run following touchdown. It’s best explained this way: At one extreme, we can use a shallow approach angle, in which our airspeed is higher (with a touchdown at or slightly above effective transitional lift), our rate of descent is very low and our ground roll/run is long. That approach is relatively easy to master and has its place when landing to flat, unobstructed areas.
For illustrative purposes, let’s say the other extreme is a 90-degree vertical approach angle. This theoretical approach would use zero airspeed and a very high rate of descent and result in little or no ground run. It would also be extremely difficult to perform. Again, this example illustrates the extreme ends of the spectrum. I am not advocating this type of approach. You can execute a safe and controlled dust landing with minimum ground roll/run to most areas using factors in between these two extremes.
Over the years, I have executed thousands of dust approaches while training others. During that time, I have learned dust landings using a steep side of a normal approach work best when landing to the toughest and dustiest landing zones. This type of approach is tough to perform, but I believe every aviator needs to master it.
Approaches using the steeper approach angle must be flown in concert with a higher rate of descent than that of a normal approach. By a higher rate of descent, I am not implying the aircraft has to literally fall out of the sky. Hardly so. While the brownout condition occurs without warning using the steeper approach, it reduces the opportunity for the dust to cycle through your rotor system prematurely. That decreases the likelihood of a brownout before you are landing assured.
In addition, these approaches require greater skill due to the timing factor involved with adjusting the controls for touchdown. The benefits, however, become apparent when landing to unimproved, dusty landing zones. This approach reduces the ground roll/run while allowing the pilot to see the landing area for virtually the whole approach.
The confidence to perform a dust landing with this type approach comes only through repetition with the benefit of a more experienced pilot or instructor pilot on the other set of controls. Most of this training can take place in a non-dusty area to reduce wear and tear on the aircraft. The final exam, however, must be in true brownout conditions. Only then can aviators know their skills are up to the task.
Surprisingly, I’ve noticed many aviators, especially those flying more powerful aircraft, tend to ignore the wind when determining their landing direction. Forgive me for stating the obvious, but this cannot be overemphasized: Landing with a tailwind forces you to land with a higher ground speed to avoid browning out prematurely. Remember “wind calm” does not always mean there is no wind. Just a few knots of wind can make all the difference in the world when it comes to your dust landing.
Try it yourself. Experiment with a tailwind and headwind dust landing under identical light wind conditions. You can use a quartering headwind/tailwind if you like. Regardless, you’ll be amazed with the results.
Knowing the surface wind is especially important to me. In times where trusted indicators of surface wind were absent (trees, dust, smoke or water), I went through the effort of generating my own dust with a low approach to an area away from my final landing area. I performed the maneuver at a distance from my final landing area to avoid obscuring it prematurely for my later approach. This technique allowed me to accurately determine the wind direction and then consider it, along with other factors, in deciding my final approach method.
Formation landings add a measure of risk due to the increased chance of collision during the landing or go-around phase. Collective training is necessary to ensure individual crews work as one during their formation landing. While the landing techniques for formation aircraft are the same as those for single-ship operations, all aircraft in the formation must use the same approach angles, speeds and braking. In addition, formation landings in dust can be stacked down as a technique so the trail aircraft touches down first. All other chalks land in succession with the lead aircraft touching down last, thereby enabling all the aircraft to land in relatively clean air.
Another landing technique to use is an echelon formation so aircraft can touch down simultaneously. This is only one of many techniques that can be used if the landing zone is large enough and the ground commander doesn’t mind their forces being spread out.
Limited visibility operations, whether they’re in dust, sand or snow, are some of the most challenging environments an Army aviator can face. The primary duty of the PC is the safe operation of the aircraft while performing the mission. Flight technique is important while flying in these challenging conditions. However, crew coordination briefs, rehearsals and application, coupled with the correct flight techniques, are critical to both mission accomplishment and aircrew safety. Fly safely!