| Figure 1 shows a microburst--a downward motion of air that spreads in all directions when it hits the ground. Figure 2 illustrates wind shear--the variation of wind over horizontal distances. Figure 3 shows the effect a crosswind has on aircraft at the landing phase. Figure 4 reminds you that winds on the ground can be different than winds aloft--headings you fly in the pattern help you keep a precise track over the ground. |
Ten minutes into the 30-minute flight, we tuned a radio to the automatic terminal information service (ATIS) and were surprised to find out that microburst alarms (with downdrafts clocked at more than 5,000 feet per minute) were going off all over the Colorado Springs airport. To provide a frame of reference, there are three long runways and 10 separate low-level wind shear sensors positioned at various points within the field boundaries, and all of them were activating in the tower.
Larger aircraft were reporting airspeed losses of 30 to 35 knots on final, and several jets in holding patterns away from the airfield advised that if the microburst alarms didn't stop soon, they'd have to divert to Denver. Someone hearing all this on the radio couldn't help but wonder,"What's with these winds?" They had come up very suddenly.
Your homework assignment is to get into the books, do a little research, examine this situation, and think about its implications. A good start might be to check out the Aeronautical Information Manual, the Internet, other authoritative weather sources, and the NTSB and AOPA Air Safety Foundation accident databases for the operational implications of thunderstorms, wind shear, microbursts, gust fronts, crosswinds, and similar weather phenomena.
Awareness of wind is important to your personal flying safety, effectiveness, and enjoyment. In many parts of the country, winds tend to be higher in the winter and spring months, but you should consider them during every flight.
Set thoughtful guidelines
What are your personal wind limits (and not just for crosswinds)? Your answer should not be"I don't know."
When a flight instructor first signs you off for solo, he or she probably includes a wind limitation in your endorsement that is lower than your airplane's demonstrated crosswind component. That's because you are still learning, and your proficiency at that time allows safe operations only up to a certain point.
If you've earned your certificate, you're no longer subject to an instructor's limitation. So what does your current proficiency allow? What limitation would you write in your logbook today? If you're unsure, why not grab a flight instructor and find out? Keep these guidelines in mind.
Thunderstorms. Don't fly within 20 miles of a thunderstorm and the winds it produces. Wait until it moves out of the way, or alter your course-or turn around-before you get near it. Have you ever seen an airplane that has been beaten up by hail from a thunderstorm? Hold that image and you'll agree that you don't want to go there.
If you ever find yourself tempted to flirt with thunderstorms and the many hazards (especially winds) associated with them, just ask,"What is so important about what I'm doing that I have to fly near this thunderstorm?"
It is critical to ask that question when you still can answer it without undue stress. If you do, you won't have any thunderstorm"war stories" to tell, but that's OK. There are plenty online; go to www.ntsb.gov and sort your accident query on"thunderstorms."
Microbursts. They should be avoided altogether. This phenomenon makes for some frightening reading. It just isn't possible to outclimb a 5,000-to-6,000-fpm downburst. Take it on faith that the wind shear associated with a microburst is too much for most pilots and airplanes to handle. Go somewhere else if you can't wait it out.
Also be aware that microbursts can happen in conditions that you might not expect-in and under virga, for instance. That's rain that doesn't reach the ground. On the day we flew from Pueblo, the microbursts occurred in clear air. There were only scattered clouds.
Wind shear. Carefully evaluate what's happening when you start to experience turbulence or hear a wind shear advisory-and be cautious. According to the FAA, 80 percent of the wind shear advisories you hear are real. Don't ignore or reject them out of hand. The hazards are out there, whether you can see them or not.
Crosswinds. Make sure even in VFR conditions that you have the forecasts for everywhere you plan to go before you take off. If the destination forecast isn't available, check out the area forecast. Ask questions about the wind during your briefing from flight service. Even when you're flying under visual flight rules, always pick an alternate airport before takeoff. On a mountain flight, good practice dictates that you have two alternates in mind-airports where you've landed previously with an instructor-before you depart. Don't arrive only to find out too late that you can't safely land.
Check out the forecast surface winds for your arrival time-and file a flight plan ahead of time. Check temperatures and winds aloft to see if there are any irregularities or directional changes. Look for fronts bearing down on your destination and expect 180-degree wind shifts, even if no clouds are present. Wind shifts always accompany frontal passage.
Winds at pattern altitude. These are important, too, because they almost always differ from surface winds. The headings you fly in the pattern will help you track a precise course over the ground, just like the rectangular patterns you learned to fly for the private pilot certificate. Good tracks equal good patterns, and good patterns usually result in good landings. Seldom will you see a bad landing result from a good pattern. Be aware; correct for the wind in the pattern and look forward to good landings.
Wind compensation throughout the approach and landing process is important-even after touchdown when you're on the landing roll, and during taxi. In changing or variable pattern situations, my favorite radio call is,"Tower, say winds."
Gusts. Do you remember how to compensate for wind gusts on final? How often do you really do that? Just add one-half of the gust velocity to your final approach airspeed. If the winds are from 270 degrees at 8 knots with gusts to 18, that's a 10-knot gust component. Add 5 knots to whatever your normal final approach airspeed would be, and don't forget that the five-knot gust correction on final will cause you to float a bit in the flare.
Other"adverse" winds. We've all heard stories about strong headwinds at altitude, but how about headwinds-and tailwinds-on the ground? Scores of airplanes have been turned over during taxi because their pilots failed to hold the flight controls in the proper positions.
Headwinds can shorten your takeoff roll, but don't count on them to reduce the computed takeoff distance so you can legally attempt takeoff from a short runway. What happens if the headwind quits just as you begin your takeoff roll?
The same logic applies to taking off in a tailwind. Just a 10-knot tailwind will increase your takeoff roll by 50 percent on a hard surface compared to calm winds. That might be OK if you're on a 9,000-foot runway at sea level. Run the numbers for a 1,500-foot grass strip in the mountains or on a hot day, however, and you'll find that it won't work in a lot of airplanes. Always calculate your takeoff performance.
Fuel planning for in-flight winds. There are two critical things to remember about the winds here: Always compute how the winds will affect you en route, and keep track of how the wind affects you as you fly.
Over the past five years, there were 223 general aviation fuel exhaustion accidents. The pilots involved simply ran out of fuel. Were these mishaps caused by failure to plan for wind effects en route? Were they caused by changing winds or excessive headwinds-or lack of awareness of what was happening en route?
If you ever experience uncertainty about the winds, whether you're planning a flight or already en route, check it out. The mere act of doing so illustrates that you're aware and thinking about the wind-a great virtue for pilots to practice.
In flight, Flight Watch (122.0 MHz) exists to help you with anything you need to know about the winds. Don't forget about ATIS and AWOS/ASOS-although you're certainly considering them for your departure and destination airports, don't overlook this information at airports along your route-you can access it by telephone or online before you take off, or through their radio broadcasts while aloft. You can also get wind info from ground control, the tower, approach and departure control, and other sources.
Ask yourself,"How do I think about the wind, anyway? What wind factors do I consider when I'm flight planning and making decisions? Do I use both existing/reported winds and forecast winds? Do I include intermittent conditions-and do I specifically check how long intermittent conditions (especially winds) are forecast to persist? Am I generally conscious of the effects of 'wind' while I fly? Do I consider -or even think about-gusts, or only steady winds?" They're all important.
Are you wondering what we did the day we encountered those microbursts on the way to Colorado Springs? Well, after holding for about 45 minutes over a racetrack several miles south of town, we headed back to Pueblo to wait out the weather. What would you have done?
The 'poor man's' wind indicator
The next time you walk out to your airplane, take time to look around.
If the wind is at five knots, you will feel it on your face; dust and paper start flying when the wind is above 10 knots. When you see small tree branches moving, the airport windsock will also be standing straight out. That means the wind has reached 15 knots, and it's time to pay attention to the direction of the wind.
In Colorado Springs, Colorado, looking to the west from the airport toward Pikes Peak, there's a steam plant. You can often tell what kind of a day it's going to be by just observing the behavior of the rising steam. Anything like that near where you fly?
It is difficult to overemphasize the importance of wind on your flying. Up-front awareness keeps the ever-present wind in perspective. If it suddenly occurs to you to ask, "What's with these winds?" you might already be behind the power curve.
The important thing is to stay ahead of the wind as you fly. It's not the wind itself that's important, but the effect winds can have if you fail to anticipate or correct early for them.
Wally Miller is president of an aviation training, consulting, and marketing firm in Monument, Colorado. He is a Gold Seal CFI who has been instructing for more than 30 years and flying for more than 40.
Related Articles
