Page 3.46 ( 5,833)
Flying Winds in the Pattern
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Wind; ....The Calm Wind Approach; ...Light Wind Patterns; Strong Wind Patterns; ...Crosswind Leg;... Turning Downwind in a Crosswind; ...Base Leg Turn with a Tailwind; Base to Final Turn; ...Right Patterns; ...Tailwind Final; ...Headwind Final; ...90-Degree Crosswind; ...45-Degree Crosswind; ...Crosswind Procedures ; ...Extreme Crosswinds; Patience, Patience, Patience; Reading the Windsock Wind and Glide; Beaufort Wind Speed Scale in Knots; ...Finding Wind Direction and Velocity with E6-B; ... Some Tailwinds Are Up to No Good; Instruction in Winds; ...Wind Shear; ...Why Do Pilot's Slow Down on Base?: ...
An airplane moves in an air mass whose movement affects the ground speed of the aircraft. The ground track of an aircraft is the result of a combination of aircraft speed and direction as influenced by air mass speed and direction. An airplane is capable of moving in six different directions. The three rotational moves are controllable by the pilot while the other three are influences from the air mass around the aircraft.
In every landing the pilot should be aware that airspeed and ground speed are not the same. Regardless of groundspeed the required airspeed must be flown. The landing ground speed in a 90 degree 30 knot crosswind will closely approximate that of a calm wind landing. Regardless of the wind direction and velocity a minimal ground contact speed is desirable. The pilot must exercise his best judgment in consideration of conditions, POH recommendations and his own abilities in deciding how to apply flaps. If you are undecided or affected by unfamiliarity, turbulence etc, get further instruction to improve your decision-making ability. As with any landing, do not add flaps within 200' of the ground. Configuration changes are likely to have significant influence on your airspeed control. The removal of flaps should only be incorporated into a go-around.
Wind often is very stressful to the pilot. Takeoffs and landing techniques require greater skill under the influence of wind. even the light and variable wind adds complexities that are difficult to plan for. Having specific wind information can either add to or subtract from a pilot's stress. Runway selection is primarily based on wind direction except where noise abatement rules prevail. Acquiring wind judgment skills is a prime reason for flying in different conditions. A pilot has no way of knowing how the wind will be on a particular leg, at a particular runway, at a particular time or how it will change without notice. You must always fly in anticipation of the wind never being as forecast, stated or expected. Use the wind to stretch your skill limits.
With experience a pilot learns to read winds from water, dust, DME, GPS, the windsock and weather forecasts. Regarding the latter, one thing you can be certain of is that the winds will NOT be as forecast. It is not a good idea to read the wind from a tetrahedron. Most tetrahedrons have locks that allow them to be positioned for the preferred runway without regard to wind direction. The windsock is the best wind indicator at an airport and should be noted on downwind and especially on final. The AWOS at an uncontrolled airport is up-dated every minute. Scheduled ATIS changes are once an hour at about 45-minutes after the hour. When conditions change rapidly or significantly the ATIS may be updated. What you see on downwind will enable you to make a wind adjusted pattern. A disproportionate number of landing accidents are caused by a pilot's failure to adjust the pattern for wind direction and velocity.
The FAA wind cone (sock) can be of several colors but usually orange and either 8 or 12 feet long. Windsocks are fully extended in 15-knot winds. I make a practice of having students practice reading windsocks by comparing ATIS or tower wind directions and velocities with their guesses from the windsock. At one time Concord, CA had five windsocks. It was not unusual to have them all showing different direction and velocity. There is no record of the first windsock, however, the first lighted windsock was sold in 1928 by the Heath company.
When winds are gusting and shifting it is best to add one-half the gust value to your approach speed to protect against shear-induced changes in airspeed. Wind shear on approach causes turbulent eddies that can cause real and illusionary changed in the flight path. An aircraft on glide path can develop sink rates that con only be arrested with full power. This sink is because of loss of lift caused by a headwind component becoming a tail wind in a matter of seconds. Aircraft failing to make adequate correction will land short. A go-around is the option.
The setting sun is already below the horizon. Refraction causes the illusion.
. Perhaps the easiest way to remember is that any verbal wind direction by ATC is given magnetic.
The Calm Wind
One of the most difficult patterns to fly well is the one required by a calm wind. In a calm wind situation a student pilot anticipates that landings should be easier. Not so. It is the calm condition at an airport that creates problems. It is not usual in calm wind conditions to have winds of differing velocities as you descend on final. During calm wind landings I suggest that you allow a slightly larger pattern to allow for such variations. If you use the standard landing procedures, suggested elsewhere, you will probably be high on final in calm wind conditions. The airplane is configured for a steep approach but does not come down. Even with full flaps, power off, and short field approach speed the airplane does not come down as expected. Even a well-planned approach under calm surface wind conditions can result in a go around. A second approach may have the same result. The fact is that the calm wind at the surface may well be a tail wind 500' above the ground.
If you experience such an approach, advise the tower to consider changing runways. Even at tower airports it is not unusual to have a wind shift occur well before the runway is changed. Sometimes the runway will be retained because of local noise-abatement requirements.
Last week, as I walked up to the plane, I momentarily stopped and felt the wind. It was very light but could be perceived as a tail wind for the noise abatement runway currently in use. I had my student, sitting in the plane, get out and asked him to feel the wind. What followed was an analysis of what happens when a wind is classified as "calm". Even more importantly, we covered all the effects for the even greater probability that the wind would be "light and variable". We did some watching of aircraft making their landings. Landings were consistently long on the 5000' runway. Also, the landings were usually off to the side of the centerline.
On average, landings are made into runways with the twelve-knot relatively constant velocity and direction winds. Most of our practice and landings are into such winds plus or minus a knot or two. This experience has taught us to make the adjustments to the pattern and aircraft configuration required producing a satisfactory landing. "Calm winds" which are more likely to 'light and variable do not provide the clues the inexperienced pilot has come to expect.
The light tail wind will increase the ground speed and shallow the approach angle. The usual changes in flaps, power, and airspeed fail to produce the desired results. This is caused by the fact that, while the tail wind may exist from 600 feet down to 100 feet the winds higher and lower will be from different directions and velocities. Even the tail wind will vary in velocity on final. The momentary truly calm wind compounds the difficulties.
The solution I offered my student was to extend the down wind leg of the pattern by twenty to thirty seconds any time the ATIS, wind sock, or AWOS indicates a calm wind condition. This adjustment allowed for the more shallow approach angle caused by the increased ground speed. The student was on a good approach but a new "calm wind" problem arose. In the flare the aircraft would begin a barely perceptible drift off the centerline.
It seems that the intensity of the landing itself often so focuses the attention of the student that he/she is completely unaware of drift unless it is either pronounced or occurring just before touchdown. The likelihood or probability of this drift condition occurring must be pre-registered into the mind of the pilot any time the "calm" condition exists. With the runway out of sight in a proper flare the pilot must get his clues from the peripheral vision and the horizon. This takes both practice and experience especially in calm conditions. A failure to correct even the slightest side load on the landing gear is potentially very harmful to the aircraft since this is the weakest area of landing gear geometry. The instructor who does not foresee this area of landing difficulty is not properly anticipating an area of difficulty. It is best to teach every landing as though it has a cross wind.
Strong Wind Patterns
A few day prior to this flight another student and I had winds at 23 knots with higher gusts 40 degrees off the runway heading. Once again I proceeded to talk and walk through the headings for both left and right traffic that would produce an appropriate pattern. Just to get into the plane and start doing landings in these conditions would have been most inappropriate. We were transitioning the student from a C-150 to a C-172. This was his third C-172 flight but his first since getting his license.
In the pattern walk through, I gave the student the needed opportunity to see that some operational adjustments would be required. The initial takeoff would cause us to gain altitude over less distance so that our crosswind would need to be flown angled well into the wind and extended somewhat to create a wider downwind. The turn downwind would need to be angled away from the runway since it was necessary to fly a somewhat wider downwind leg both because of being in right traffic and because the wind direction would produce a an effectively shorter base leg due to a higher ground speed. The power reduction would begin before the numbers and even more angle into the wind would be taken to counter the increased wind effect at a slower airspeed. The wider downwind would give us a base leg sufficiently long to allow adjustments in the length and height of our final approach. The instructional emphasis here is that the pilot's control over the final approach must begin on the downwind leg if not sooner.
Under these or similar conditions the landing must be considered an option not a necessity. The go-around is the first choice option if the stabilized final approach cannot be established.
Flying the same runway in left-hand traffic in the same wind conditions requires the pilot to make a shorter crosswind to help counter the wind's efforts to drift the aircraft away from the runway. The downwind leg must be angled toward the runway. The base leg again must be sufficient to allow adjustments to the height and length of the final approach course.
The instructional process for landings is not complete unless it exposes the student to the wind conditions described above. The opportunity to fly both left and right patterns in the same crosswind conditions is essential. Going to controlled airports with multiple runways can create variety of pattern and conditions. ATC will honor requests for crosswind runways and different patterns when traffic conditions allow. Changing the time of day is a good way to obtain varied wind velocity.
Crosswind heading/course skills are required in every airport take off where there is anything other than a calm wind. If the wind is right down the runway then the wind effects on heading/course occur on the crosswind and base leg. Just as importantly, the wind speed effects occur upwind and downwind. The groundspeed of the takeoff and landing are as slow as the differences between Vso and wind velocity allows. If the upwind is not angled far enough away from the airport you are apt to have a very short and fast downwind. If the speed of the downwind is not anticipated in the turn to base the downwind may be excessively extended. Failure to correct heading in the crosswind and base legs makes the pattern a trapezoid (wrecked-angle) not a rectangle. The incorrectly flown crosswind leg can greatly reduce the separations normally allowed for 45-degree entry of arriving traffic. Draw it out and see the effect.
The 90-degree crosswind to the length of the rectangular pattern requires that the crosswind be adjusted. The crosswind leg will be affected by the wind. The groundspeed may be either fast or slower depending on the direction of the pattern. Adjustments to the leg length must be made in anticipation of the base leg requirements. The wind effect on the base leg ground speed will be opposite to that of the crosswind leg. Draw it out and see the difference the pattern direction makes. Draw wind direction and crab angle required.
Turning Downwind in a
I believe that shallow banks are more likely to result in a skidding turn and a stall with the ball to the outside (high). This is a prelude to a spin. Better to always make 30 degree banks in the pattern and adjust where you rollout. This bank reduces the "blind" time in the turn. Pre-decide how you are going to correct for the crosswind. Put the plane where you want it on downwind to give a base leg length sufficient to allow corrections.
Skill in performing crosswind patterns is directly related to ground reference skills. The turn to the crosswind part of the pattern also requires awareness as to the wind's effect on speed and ground track. At 90 degrees the crosswind leg will be either a tailwind or a headwind. There is an illusion of speed that occurs during these turns. Rely on the indicated speed and not the perceived speed from your peripheral vision. Without conscious awareness this side vision will give the pilot a sensation of speed or lack of it while in a turn.
The downwind leg of the pattern requires that crab be held into the wind. The pattern should be maintained regardless of the wind. This applies either for takeoffs or landings. In a crosswind, the pilot must depart upwind with sufficient crab that the track of the plane will not conflict with the straight out path from a parallel runway. The turn from base to final must be flown so as not to conflict with the final approach of a parallel runway. Draw an airport and use the words as appropriate wind direction crosswind leg
>90 degree turn <90 degree turn
Rt. downwind leg
Crosswind downwind crab angles
Left downwind leg has dangerous effect if wind allows a short base leg.
Should you find that your patterns are getting tight because of wind, the
cure is to do some 700' ground reference practice in the worst wind you can
find. Go with an instructor if you can, solo if you must. The closer you are
to the ground the better you will be able to judge the required correction.
Once you have the required correction climb back to pattern altitude and fly
the wind correction there. The idea is to develop the sight lines required.
Base Leg Turn with a Tailwind
The greatest hazard on such a base leg turn occurs when the wind becomes a tailwind. This increases the aircraft ground speed by the wind velocity. If the pilot has not correctly anticipated the increased ground speed with an early turn to final several problems arise. As the pilot becomes aware of overshooting the final turn to runway, he senses (peripheral vision) that he is moving much faster than usual. The approach and glide angle is much flatter than usual. To lower the speed he raises the nose, to correct the overshoot he wants to increase the rate of turn most often this is accomplished by additional rudder. Here we have the classic stall-spin entry in the downwind (tailwind) turn. Basic procedure if the wind is blowing you towards the runway on downwind would be to double your distance from the runway on your downwind. The 'home-field' pilot who flies by reference to ground objects for pattern orientation is especially exposed to the hazards of this situation.
Nearly 180 degree turn
to make crosswind
to downwind turn extended crosswind leg
Nearly 180 degree turn
90 degree turn
Shallow left bank and nose held Right bank held to align with
Aligned with runway with bank runway and left rudder used to
reversed to right. Nose held straight keep nose straight.
with left rudder right wing low
Base to Final Turn
There are many ways to discuss and teach the hazard that can exist in this route source of the downwind turn with associated stall and spin. Some instructors go to great lengths to emphasize that this turn is the home of the fatal stall spin, that occurs along with a runway crosswind, a base tailwind, a steep turn, slow airspeeds, low altitude, optical illusions and excess bottom rudder. These all need not occur together. Any two or three will be enough for the unwary.
(1) The crosswind causes a short base leg;
(2) The tail wind on base causes optical illusion of excess speed so you raise the nose and lose airspeed;
(3) You overshoot the runway on base and make a steeper than usual turn to final;
(4) You need more turn but are already too steep so you apply rudder to bring the nose around;
(5) You are now low, slow, steep, yawing, stalling and out of options.
As an instructor I take another approach. My crosswind pattern practice is designed so that we practice just as many left patterns as right patterns. My preflight consists of pattern drawings and pattern walk-through that emphasize the crab angles needed to expand the distance from the runway when the downwind crosswind is blowing the aircraft into the runway. By staying well away from the runway where the crosswind will be a tailwind after our base turn we avoid the short base and the entire visual trauma caused thereby. Rather than teaching the stall recognition of this situation, I place the emphasis upon avoidance of the situation all together. The danger lies in flying the incorrect pattern in the first place.
As mentioned above, the best and only preventative for getting into a situation where the base leg is too short, is for the pilot to have corrected for the crosswind on the downwind leg so as to fly a wider pattern that will give a longer base leg. This is most easily accomplished in left patterns because the runway is easier to see. The potential problem worsens in right patterns. The pilot is apt have difficulty in seeing the runway. Several dips of the wing to bring the runway into view will cause the plane to gradually move closer to the runway. This can drastically shorten the base leg and lead to a stall-spin situation. If a crosswind is moving you closer to the runway, get much further out (away from the runway) than seems appropriate and you should be about right. In this situation further away from the runway is much safer.
The turn into a following tailwind raises the ground speed. The pilot who reacts to this ground speed and not the indicated speed is likely to increase backpressure on the yoke to lower the speed. A no! no! You must understand the relationships between indicated airspeed, ground speed and relative wind. In a downwind landing your approach will be flatter, faster (ground speed) and higher. The main difference between a headwind landing and a tailwind (downwind) landing is the angle of the approach and the ground speed at touchdown. Do not increase airspeed downwind. A 10 knot tailwind on final will double your required landing distance.
The downwind rollout distance difference from a no-wind landing can be figured by finding the "square of the quotient of the actual touchdown speed divided by the normal touchdown speed" . If you normally touchdown at 40 kts and are landing with a 10 kt tailwind you will first divide the normal speed 40 + 10 = 50 by 40 = 1.25 x 1.25 (squared) = 1.56 which means that you will require 56% more landing distance with a 10 kt tailwind. This only works if you make the same original touch-down point. Double the distance is more likely.
Runway shallow tailwind approach diagram
A tailwind will increase the groundspeed and make the approach shallow as diagramed. The amount of tailwind varies with the relative angle of the wind.
--Add to required POH no-wind distance how far it takes to accelerate to
--You will have a higher ground speed than normal to achieve liftoff. Fly the indicated airspeed.
--Landings require 20-percent more distance for every five knots of tailwind.
--Takeoffs require double POH distance for every 10 knots of tailwind.
--Tailwinds cause pre-mature rotation because of excess groundspeed illusion.
--Use your POH.
The turn into the head wind is not as likely to create a problem since the reaction is to lower the nose. These perceived speeds become critical in landing. A strong headwind to the runway will, however, cause a relatively steep and unfamiliar glide angle. Do not let this steeper approach cause you to raise the nose. Maintain normal indicated airspeed and do not be concerned about being too high, on a short runway, or even landing long. Keep the normal approach speed regardless of the approach angle.
Winds of 15 kts or greater will give very steep full flap approaches. Barring gusts, this is no problem as long as the correct approach speed is maintained into the roundout and flare. The angle of the approach angle gives the illusion that the descent is actually faster. Such is not the case. If the nose is raised to slow the descent it can actually increase the rate of descent while decreasing the airspeed. Under such conditions, a stall can occur unexpectedly without the exaggerated nose-up attitude of the typical stall. By maintaining the proper approach airspeed we will have the ground effect cushion required during flare. Under gusty conditions it is well to add 5-10 kts to approach speed, use less than full flaps, and maintain power into the flare.
Very strong winds 18 kts up require special attention. The crosswind turn made after takeoff may not be 90 degrees to the runway. Rather a heading must be selected to give a 90-degree ground track allowing for the wind. The same procedure must be followed on downwind and base. It is not necessary to worry about being too high in strong winds even with no flaps. To avoid being carried too far away from the runway on your downwind, you should proceed with minimum delay to your base with a crab toward the runway.
The stronger the headwind wind, the steeper the approach
90 Degree Crosswind
At the multiple runway airport, a 90-degree crosswind is a relatively unusual wind. For this reason some pilots may lack sufficient experience to deal with 90-degree crosswinds of any velocity. If the crosswind is blowing so as to move you closer to the runway, double your downwind distance from the runway. Choose a heading that will make the desired correction and fly the heading. With a longer base leg you can start your turn early and allow the wind to blow you over to the final approach course. You will already have the proper wing low so all that is needed is to punch in opposite rudder and lower the nose for approach speed. You should draw this out in both left and right patterns around a runway until you understand what safety requires. You can always ask tower to use a crosswind runway if it does not conflict with traffic.
45 Degree Crosswind
When the crosswind is less than 90, each one of the pattern legs requires a heading /course adjustment. Prior to takeoff you should make a tentative heading selection and flight lines that will give the desired crosswind ground track for each leg. Allow an extra 30 seconds or so of time when flying against the crosswind. If the wind is a partial tail wind you might turn downwind sooner than usual. It is more likely that you will unintentionally stay too close to an airport in windy conditions. By staying further away and keeping a somewhat longer final, you allow yourself more time to make adjustments. Draw a pattern around an airport in both left and right traffic and a wind at 45-degree crosswind.
I fly at a field where a local FBO has traditionally limited all student flights to 6-knot 90 degree crosswind landing conditions. Such instructional restrictions, I feel, unduly inhibits the student's opportunity to gain the needed experience in the real world of flying. Just the last two days, I had a student out in the practice area and at two different airports in 22-knot winds. We did ground reference and landings. We did full flap, no flap and slips to landings in direct-down the runway winds and crosswinds. The student learned to enjoy the slips and the sense of control that a smoothly performed forward slip gives. We side slipped to each side of the runway and worked on getting on the centerline down low. My only regret is that the winds were not stronger and more variable. She takes the checkride tomorrow. The windy conditions are expected to continue. She will not fail because of non-exposure to the test flight conditions. Draw a runway and pattern with small aircraft on the lines angled to illustrate the crab angles required to fly the pattern. Place the words where appropriate.
Turn to final requires
right bank to runway reversed
to left bank and right rudder
wind direction extended crosswind leg
Since wind is blowing
you away from runway,
Stay closer than usual
Nearly 180 degree turn
to make downwind to
Shallow turn base turn. Nose held
early 180 degree turn from straight with left
crabbed upwind to the rudder and right wing
correction angle required low.
for the crosswind
The crosswind landing requires crossing the controls, not what you have normally striving for. It feels funny (read bad) You fight the effects on crosswind, downwind, and base by turning the aircraft into the wind in coordinated flight. On final, the rules change and the effect of the wind is corrected with wing low and opposite rudder. 1/2 of a Dutch-roll.
Winds are not usually steady and stable. They will vary in direction, velocity and change with altitude. A constant adjustment of rudder and wing is required to compensate for these changes. If the pilot persists in holding a tight grip on the yoke he will be unable to sense the corrections required.
When you first fly downwind you must start making your adjustment for the wind. The wind is never exactly as given on the ATIS or the AWOS. The wind be it calm, blowing a gale, 90 degrees cross, down the runway or any combination thereof, will require the pilot to adjust, plan, re-adjust and re-plan the pattern required for a given wind. Failure to anticipate and make the required corrections in a timely manner can lead to an accident. If you have not made a pattern that allows a smooth transition to final, go around.
The base to final (key position) turn is the critical point in the pattern. You can correct for being high or low by correcting the angle and by flap application. You need practice to make this determination of being high or low. Regardless of the wind you should fly a constant airspeed since this will give a relatively constant angle on the approach. Learning to judge the angle commensurate to the wind direction and velocity takes practice and experience at a wide variety to airports.
Problems with crosswinds are directly related to basic flying skills. Ground reference, trim, airspeed, Dutch rolls, and light touch come immediately to mind. You must be able to make the required runway alignment adjustment to counter any unexpected wind change instinctively. There is no time for complex thought processes close to the ground. You must practice the Dutch roll until it occurs automatically. The need for drift correction can occur even in "calm" conditions.
Every aircraft is certified has having a demonstrated crosswind capability. This is determined by the winds available at the time of certification. An average pilot should be capable of landing in such conditions. As crosswinds exceed this demonstrated minimum a pilot should minimize flaps and increase approach speed. The maxim aircraft/pilot t capability is exceeded when full control input is not capable of maintaining directional control even at increased speeds.
The cross-control slip method of crosswind landings utilizes the lift forces of the wings to counteract the drift effects of the wind. The wind is countered by varying the bank (read lift-turn) effects of the wing. Any turn is countered by opposite rudder. A crosswind landing is possible as long as there is sufficient rudder power to keep the nose aligned with the runway. Additional rudder power may be obtained by increasing airspeed.
Properly performed, a crosswind landing will touchdown on the upwind main wheel first. On touchdown the yoke should be moved into the wind to keep the downwind wheel off the ground until the aileron ceases to be effective. This means that full deflection of the aileron will be required as the aircraft slows. If the aircraft is kept rolling straight with the rudder the lowered wing will not be able to touch the ground because of ground effect.. As in other landings the nosewheel should be the last to touch. In this configuration you now have the yoke correctly positioned for taxiing.
Poor crosswind landings more than from any other single cause damage aircraft. Ability to land in a crosswind depends upon the aircraft capability and the pilot's ability to use that capability. Crosswind landing skills require constant rejuvenation. The complexity of skills used in making crosswind landings are not exceeded by any normal flight maneuver.
Regardless of ATISs or windsocks, the only wind that counts is the one when you touch down. In strong winds the further out you confirm your ability to remain in line with the runway and the nose in line with the centerline, the better you can control your touch down. Once in the sideslip, you have good drift control while in the flare. How much slip and rudder you will need in the flare is a variable. You do whatever it takes.
The crab alternative is perhaps better for aircraft like the Skipper which tends to be squirrelly. In the crab arrival you wait until you are in the roundout before lowering the wind and aligning the nose with the centerline.
I did a basic IFR flight lesson as a review with an instrument student today. He was under the hood from takeoff until heading home slightly over an hour later. The takeoff was o.k. Except, he did not put in enough crosswind correction as we rose above 100 feet. Then the trouble began. Over the neighboring hills turbulence caused the aircraft to rock and roll. The pilot began fighting the aircraft and turbulence with a relatively tight grip and abrupt corrections. After three or four minutes I was asked to take over. The plane, actually, was well trimmed. The pilot had been impatient and was not giving the aircraft enough opportunity to smooth out. I smoothed everything out VFR and gave control back. He subsequently had no problem. You can never win the yoke fight with turbulence if you make it a fight. A light touch wins with horses, airplanes and women.
Next we did climbing-timed 360s both left and right and then did them in level flight followed by power off and on stalls. Initially the stalls had some altitude and heading problems but by having him do a VFR stall series holding heading with emphasis on the heading bug the problem dissolved. All subsequent hooded stalls did not have heading problems. Even the full-power stalls held heading into the stall and during recovery. Likewise, with the clean and dirty slow flight that included timed 180-degree left and right standard turns.
We headed home by tacking to a VOR in a strong crosswind. The flare was into a 12/14 knot 90-degree crosswind in clean configuration. As he flared, I advised him to leave the power in. The aircraft floated about 10-feet above the runway. At this point he must have become impatient for rather than reducing power in 100-rpm increments he pulled it all off. The aircraft fell like a rock. He was barely able to avoid a hard landing. I hope a lesson learned. Moral: In landings don't become impatient and try to land the airplane, let the airplane land when IT is ready.
I play a little game every time I arrive at the airport in my truck. I get a look at a flag or windsock and the sky and then try to see how close I can come to matching the ATIS. You can get so that you come pretty close with your guessing.
Wind Effect on
Wind Best Glide mph Glide Ratio Descent rate at 5000 feet
30kt tailwind ----64 --12.8:1-- 740 fpm
20 kt tailwind ---65 ---11.3:1--755
10 kt tailwind ---67-----9.3:1-- 775
No wind --------70---- 8.5:1-- 800
10 kt headwind -74---- 7.2:1---850
20 kt headwind -79---- 6.0 :1-1920
30 kt headwind -85 ----4.8:1- 1035
Speed Scale in Knots
Description - Visible Condition
0 knots Calm smoke rises vertically
3.47 knots Light air direction of wind shown by smoke but not by wind vanes
6.08 knots Light breeze wind felt on face; leaves rustle; ordinary wind vane moved by wind
10.42 knots Gentle breeze leaves and small twigs in constant motion; wind extends light flag
15.64 knots Moderate breeze raises dust and loose paper; small branches are moved
20.85 knots Fresh breeze small trees in leaf begin to sway; crested wavelets form on inland water
26.93 knots Strong breeze large branches in motion; telephone wires whistle; umbrellas used with difficulty
33.02 knots Moderate gale whole trees in motion; inconvenience in walking against wind
39.97 knots Fresh gale breaks twigs off trees; generally impedes progress
46.92 knots Strong gale slight structural damage occurs; chimney pots and slates removed
54.74 knots Whole gale trees uprooted; considerable structural damage occurs
62.56 knots Storm very rarely experienced; accompanied by widespread damage
63.43+ knots Hurricane devastation occurs
Finding Wind Direction and Velocity with E6-B
--From your instruments get outside air temperature, altitude and indicated airspeed.
--Compute the true airspeed.
--Use compass or heading indicator for heading.
--Use chart or GPS to get groundspeed and track.
--Using the above information you can work the usual wind triangle backwards to find wind direction and velocity on the wind triangle side of the E6-B.
--You could use vectors and a protractor to do this as well.
Wind direction can be determined in low level flight by changing your heading until you zero out your cross-track drift. Paying attention to which way you are drifting over the ground while flying straight and level will tell you which way the wind is blowing.
Wind speed can be determined by using a GPS, DME (if suitably located) or by using a stop watch to time your run over a fixed distance both upwind and downwind, then using the ratio of the times against your airspeed to compute the wind.
Some Tailwinds Are
Up to No Good
--There is no data regarding tailwind effects in your POH.
--A 30 knot headwind that is half your takeoff speed will reduce your takeoff distance by 75-percent
--The same wind as a tailwind will probably increase your required liftoff distance by over 100 percent
--The same wind as a tailwind will decrease your rate of climb by 90 percent.
--Cessna says for every 2 to 2.5 knots of tailwind to add 10 percent to takeoff requirements
--Piper has no figures above a five knot tailwind.
--Up or down slope helps or hurts takeoff performance by an average of 3 percent per degree of slope.
--Ignore slope, takeoff into the wind.
--You become a Kamakazi departing with anything approaching a 20 knot tailwind.
Instruction in Winds
In the past few weeks I have been taking pilots up in unfamiliar high performance and complex aircraft to give them the time and instruction needed for endorsements. The major region of concern for these pilots have been crosswind landings and rightly so.
Yesterday morning I had a pilot plan a local flight into four uncontrolled airports. We and planned to fly them in sequence with some configuration changes and maneuvers between each airport. At the airport, I told the pilot that we would reverse the direction of the flight. I asked if he could find a reason for the change in direction. He very correctly noted that later in the morning stronger winds could be expected at the last airport.
When we arrived at the last airport the active runway had a strong wind right down the runway. It was the short runway and presented no problem. However, after landing I had him taxi to the long runway with a 90-degree crosswind and the windsock standing straight out and swinging wildly.
The takeoff went well but on two consecutive efforts to land the pilot was unable either to maintain runway alignment, nose straight with wing down or both at the same time. We departed without making a crosswind landing. I considered this a very good lesson for the pilot. A pilot should know the point at which a flight condition exceeds his capability.
When we returned home he asked if I could have landed in that crosswind. I confirmed that I thought I could have made the landing but would have been concerned about the subsequent ground operations. Knowing what not to do is just as important a knowing what to do. In my opinion, instructors should make it a point to expose their students to upper land lower performance limits of an aircraft/pilot combination
Wind Shear (See: Downdraft)
A significant change in wind direction or speed over a short distance. Greatest effect on aircraft performance is where change exceeds ability of aircraft (mass) to be accelerated or decelerated.
Why Do Pilots Slow Down on Base?
Genes Response to Jay,
The worst situation leading up to the turn to final stall is a crosswind to the runway that serves as a tailwind when on base. The pilot lets the wind blow him into the runway so that he has a relatively short base leg giving less room and time to turn final. Without being fully aware of it, every pilot uses his peripheral vision even when looking over the nose. To answer your question as to why a pilot would slow the aircraft before turning final. It is due to the sensing of a faster than normal ground speed With the tail wind you seem to be going faster than ,normal'. Instinctively the pilot raises the nose to slow down the movement over the ground.
While looking out to the side toward the runway and planning his turn to
final he fails to note his airspeed while reacting to the apparent excessive
ground speed. This speed, which is the aggregate of aircraft and wind, carries
the plane past the point to turn to the runway. The pilot turns toward the
runway too late, too steeply, and notes that he has over-shot the runway. In a fatal effort to
get back to the runway the slowness of the speed, the steep angle of the turn
and the application of rudder to assist the turn is the basic entrance to a
stall with added yaw required to initiate a spin.
The entire situation is avoided by flying twice as far from the runway when a crosswind drives you toward the runway. This gives you a longer base and more time to make your turn to final. Turning early is o.k. since the wind will blow you to the runway.
Basic training weaknesses in ground reference, airspeed control and situational awareness add up to a pilot who needlessly kills himself. It all begins on the downwind leg of the pattern.
Yes you can maintain the standard downwind path by crabbing for the wind on the downwind but that would not change the quicker base leg caused by the tail wind. All of these patterns are flown in a situation having parallel runways. This increases the need for not overshooting the final approach. I make a practice of doing just as many patterns to the left as to the right as a way of emphasizing the need for different patterns. Situations where only one runway exists do not offer this instructional advantage. In the past week I have made four one hour flights with students in 90-degree crosswinds of 16-17 knots. Flying wider is the best solution. With the wider downwind the student has a better handle on the turn to final.
As luck would have it, my lesson today gave me a terrific first-hand demonstration of this very discussion.
Did some T&Gs at Phoenix Regional which has one runway (3/21) and a crab on the downwind worked great! Wind reported by the KCHD ATIS was 190 at 10G15.
My CFI pulls a divert on me to Williams Gateway (12/3o) and we get a left base to 30C approach so managing ground track, watching for traffic, remembering to call a 2 mile left base, etc, etc made for an interesting lesson segment. It's a little more intense trying to align yourself properly with approaches being flown on BOTH sides! I had my first Tower-commanded go around due to a Cherokee which was slow in exiting the runway. Usually I'M the one pulling the plug on an approach.
A couple of more T&Gs back at Chandler and I suddenly realized I had a huge sh*t eating grin on my face because I was making acceptable cross-wind landings!!! My body was actually doing what my brain wanted it to do.
The owner of the FBO took me by the hand, walked me to the flight-line side door, pointed at the windsock and asked me what I saw. "A crosswind, says I..." To which he replied, "And youre standing here, smiling!?!" I laughed and said, "Yup...something went very right today!!"
A great day!
Student Pilot - KCHD
18.5 Hrs ... Nowhere to go but up!
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Continued on Page 4.12 Types of Landings