Wednesday, November 1, 2006
Helicopter Training: Whither the Wind?
Knowing and using the wind properly is key to safe flight in rotorcraft. A flight-training veteran offers tips for doing both successfully.
WIND CAN BE A CRITICAL CONSIDERATION IN THE safe operation of rotorcraft, and is one pilots can grow to disregard (particularly if most of their flying is done in their local area).
That is among the common mistakes cited by flight instructors and flight-training veterans as being committed by experienced and new pilots alike.
As one of those veterans, Roger Sharkey, observed, "I don't think many pilots would say they take off and land downwind, but we all do." Sharkey is president of Sharkey's Helicopters in Lebanon, N.H. and partners with Enstrom Helicopter Co. in advanced training programs.
"It usually starts with 2-3 kt of wind," he said. "Then after about six months, it becomes 4-6 kt. A year or two later, with all still going well, we graduate to 10-plus kt of wind. All of us get away with it for years without incident. Any downwind is too much" if it can be avoided for takeoff or landing, he said ("Common Mistakes in Training [and Flying]," April 2006, page T6)
In the latest in our series of articles examining common mistakes that helicopter pilots encounter and techniques for recognizing and avoiding or correcting them, Rotor & Wing asked MD Helicopters' Nick Page to discuss knowing and using the wind.
A test and demonstration pilot for the Mesa, Ariz.-based manufacturer, Page has been in the training business for the better part of 20 years "and my flying career has been focused pretty much on training."
He agreed that a lack of awareness of the wind is a common error, "especially with pilots that are brought up in big aircraft.
"They don't tend to have as intuitive a sense of where the wind is or how important it can be for them," he said. "People that are brought up in R22-style, or smaller, aircraft tend to be far more cognizant of where the winds are, just because they don't have the luxury of power."
There are common traps that pilots fall into that lead to problems in managing the wind, he said.
One is that "a lot of times pilots get comfortable flying the aircraft they're in at the location they're at and they really don't do a good job of paying attention to the winds," he said. "They rely on the continued reliability of their aircraft to overcome any of the pitfalls that the wind presents."
Here again, pilots who fly smaller aircraft tend to be more conservative in this regard. "It's one of the first things they check prior to takeoff,' he said, "which way the winds are blowing."
The key is paying attention to what's occurring around you on a day-to-day basis. Doing that, you "very quickly will develop an intuitive sense of what's going on with the aircraft on any given day and how the winds are affecting it, without having to use mechanical, external indicators."
Wind savvy is not a matter of experience measured in flight hours.
"You can say a guy with a lot of hours is somebody who's obviously developed that knack," Page said. "But I've seen people with thousands of hours that are very ignorant of how to read the winds vs. some people that only have a few hundred hours that have a very sharp ability to sense even slight winds. And that's because they've taken the time and effort to learn what's going on around them."
In the desert around Mesa, for instance, "often times, unless the winds are blowing very fast, you don't get any of the usual external wind indicators," he said. "You don't have trees blowing. You don't get dust, normally, unless you've got extremely high winds.
"Flags are a rare thing, and smoke and so forth," he said, "so things that people can look at in other parts of the country on a regular basis, you know water and such like that, we don't have that out here. So you pretty much have to develop a feel for it."
That can be difficult, especially in a new aircraft, Page said.
The way the aircraft is handling in the ambient air can give you some very good clues as to which way the wind's blowing. "Obviously, if you've got the aircraft in trim," he said, "you can detect from crab angle a general idea of where the winds are blowing from."
When making an approach into the wind, the aircraft is going to handle quite a bit different than it would on the same approach with a downwind condition, he said. "If you've got a lot of wind, 15 kt or greater, often times it's very obvious where the winds are blowing," he said. "They tell you very quickly. The way the aircraft handles clearly indicates if you're not into the wind. It's much harder to work."
When flying in the mountains or at higher density altitudes, problems can be caused by very light winds, in the 5-10 kt realm, "where you don't get the same clear physical movement on the aircraft," Page said. "You really have to pay attention to more subtle cues."
Pilots versed in mountain flying will use a "wind circle" to plumb the winds.
"Basically, you pick a spot on the ground and, as you pass over the top of it, you execute a standard-rate turn," Page said. "You maintain that standard-rate turn for 360 deg, keeping a constant airspeed and bank angle. When you roll out on the original heading when you started the turn, how the aircraft is displaced from the start point tells you the direction of the wind and gives you a sense of velocity as well. That's a real good mechanical way until you've developed a good seat-of-the-pants feel" for the wind.
Other cues to the winds, he said, include the amount of pedal input required to maintain heading.
"On a normal approach into the wind, because it's a reduced power setting, generally speaking in an American-made aircraft you'll normally apply more right pedal then you will left pedal," he said. "If you're downwind, however, often times the power demand is greater and you find that you need more left pedal than you're used to. So that is a clue that maybe you're in a downwind condition."
The airspeed indicator provides another cue. If you're landing into the wind, even with a very light wind, Page said, the airspeed indicator on most aircraft will still continue to wiggle.
"Not necessarily reliably," he said, "but it will continue to sort of wiggle in the gauge, almost to the point of bringing it to a dead hover."
If you go into a downwind condition, "often times that airspeed indicator will stop on the peg, even while you've still got significant ground speed outside the aircraft," he said. "So that's a good clue that there's not enough air coming across the pitot tube and you're probably downwind."
It is essential to think of the wind in considering your go-around options.
"They always say landings are mandatory, takeoffs are optional," Page said. "The same thing could be said about a go-around. When you're making an approach, if you don't give yourself an out, often times whether you realize it or not you've committed yourself to landing, regardless of how that ends up." He recommends planning the go-around options into your approach "just in case things go bad."
First, as you come into an area, he said, try to determine as soon as possible the wind direction and speed. "Often times you can, if you're paying attention, have that figured out in a relatively short period of time. Then it's basically confirming or not what you already suspect and watching the cues with the aircraft and any external cues that will confirm or deny."
Again, with American-made aircraft as an example, "if you're going to run out of pedal at a high situation, in all probability the aircraft is going to go to the right," he said. "So allowing yourself an escape path to the right is probably the safer bet if the landing area will allow that." Set up an approach that allows you to break to the right should the aircraft encounter unexpected winds.
Refine that further by not making an approach that requires your right break to be a 90-deg or greater turn. "Come in at an angle that, if you have to break out to the right, instead of having to make a 90 deg or sharper turn, you can often times get away with a relatively small heading change to allow the nose to drop a little bit and gain a little more airspeed and regain your pedal, Page said.