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Crosswind Takeoff

Introduction:

  • While it is usually preferable to takeoff into the wind, but most situations will not be a pure headwind and some crosswind component will exist
  • One example of where you may want to takeoff with a tailwind would be rising terrain, or perhaps if in a glider, a lack of landing options in a rope break
  • No matter what situation you have, always run the numbers and do not exceed the aircrafts limits
Crosswind Component Chart
Figure 1: Crosswind Component Chart
Crosswind Component Chart w/ Limitations
Figure 2: Crosswind Component Chart w/ Limitations

Effect of Winds on Takeoff:

  • Headwinds:

    • Takeoffs will require less distance:
      • Air is already flowing over the airfoils without any movement of the aircraft
        • Depending on the amount of wind and sensitivity of the airspeed indicator, this will register an airspeed without any aircraft motion
      • Because the aircraft feels as though it is already moving (by a factor of the headwind), takeoff lift will be achieved in less time
      • The end-state is that the aircraft will become airborne in less time which translates to less distance
    • Takeoff at slower ground speed
  • Effects of a tailwind:

    • Increased speed to develop minimum lift causing stress on tires
    • Increased takeoff distance
  • Crosswinds:

    • Crosswinds will have some component that is chord wise flow (over the wings) and span wise flow (from the wing tip to the wing root)
    • The chord wise flow will be either a headwind or tailwind as previously stated to help or hinder performance
    • The span wise flow will always be disruptive and provide nothing as the air is not flowing over the wings from leading to trailing edge

Determining Crosswind Component:

  • Crosswinds can be determined through a number of methods which each serve a purpose, depending on the phase of flight
  • Consider your source for winds (true vs. magnetic) and remember if its written its true, if its spoken its magnetic:
    • ATC reports, a wind sock, or ATIS are given in magnetic
    • METARsare given in true and may need to be converted to magnetic
      • Remember winds are variable too so only bother converting if operating at significant deviations
  • When calculating the crosswind always use the full gust component meaning, calculate crosswind as a "worst case" scenario
  • Chart Method:

    • Crosswind charts can be found in nearly every POH/PIM but are not aircraft specific, so any will do
    • Using the example provided in [Figure 1], plot your point using the number of degrees off the runway heading, at with the full gust component as strength
      • Lets say we're going to land at runway 360 and the wind is coming from 020 at 20 knots
      • We'll plot the wind strength at the 20° radial line (representing 20° off the runway) on the 20° point (representing the wind strength)
      • From that point we plotted we can move straight left for the headwind component: roughly 19 knots
      • We can also move straight down for the crosswind component: roughly 6 knots
  • Heading indicator rule of thumb:

    • Find the reported wind direction on the outside of the DI (shown as a large blue arrow). You now have the first piece of information; the wind is from the right [Figure 2/3]
    • Mentally drop a vertical line down from the wind direction on the outside of the DI to the horizontal centerline (shown in blue)
    • The horizontal center line (red) represents the crosswind axis so visually scale-off the crosswind component as a proportion of the length of the crosswind axis, ie, the wind speed
      • Using our example this means our crosswind component is just less than 20 knots (mathematically the answer is 19 knots)
  • Sixths Rules of Thumb:

    • If angle = 10 deg then crosswind component = 1/6 wind strength
    • If angle = 20 deg then crosswind component = 2/6 (1/3) wind strength
    • If angle = 30 deg then crosswind component = 3/6 (1/2) wind strength
    • If angle = 40 deg then crosswind component = 4/6 (2/3) wind strength
    • If angle = 50 deg then crosswind component = 5/6 wind strength
    • If angle = 60+ deg then crosswind component = wind strength
  • Mathematical Formula:

    • The formula for crosswind component = Wind Speed x Sin (Wind Angle) [Figure 2]
    • Example: if the wind is 310°@ 17 knots and you are lined up 330°, you can see you have a wind angle of 20°
    • Reference the chart to see the sine of 20° is 0.3 and multiply that by the wind component of 17 knots and you will get a crosswind component of 5 knots

Crosswind Control Mechanics:

  • From the moment you begin to taxi you will need to compensate for wind blowing at an angle to the runway
  • Placing the yoke into the wind raises the aileron on the upwind wing, to impose a downward force on the wing, to counteract the lifting force of the crosswind and prevents the wing from rising
  • As speed increases, the control surfaces become more effective as you transition from a taxi to flying, thereby requiring less of an input to achieve the same effect, so you will need to take out inputs as you accelerate
    • The crosswind effect will never completely disappear so some input will remain
  • If when taking out your inputs the upwind wing is allowed to rise, it will expose more surface to the crosswind and a skipping action may result
    • This side-skipping imposes severe side stresses on the landing gear and could result in structural failure
  • As both main wheels leave the runway and ground friction no longer resists drifting, the airplane will be slowly carried sideways with the wind unless adequate drift correction is maintained by the pilot
  • If proper crosswind correction is being applied, as soon as the airplane is airborne, it will be side-slipping into the wind sufficiently to counteract the drifting effect of the wind
  • This side-slipping should be continued until the airplane has a positive rate of climb
  • At that time, the airplane should be turned into the wind to establish just enough wind correction angle to counteract the wind and then the wings rolled level
  • Allow the aircraft to weathervane as it rotates and the effect of the crosswind will diminish
    • This puts you at risk if you have too much of an input to have a potential strike with the wingtip and the ground, especially with a low-wing aircraft
    • Anticipate this by keeping the wings level and letting the airplane vane to achieve that straight ground track
  • If a significant crosswind or gusts exists, the main wheels should be held on the ground slightly longer than in a normal takeoff so that a smooth but very definite liftoff can be made
    • This procedure will allow the airplane to leave the ground under more positive control, so that it will definitely remain airborne while the proper amount of wind correction is being established

WARNING:
All procedures here are GENERALIZED for learning.
Fly the maneuver in accordance with the Pilot Operating Handbook (POH)
and/or current Standard Operating Procedures (SOPs)


Crosswind Takeoff Procedure:

  1. Ensure that the Before Takeoff Checklists are complete
  2. Check wind direction indicators, as available, and listen to ATC's wind call when given clearance for takeoff
    • ATC: "[Callsign], [Wind], cleared for takeoff [Runway]"
  3. Check the approach path is clear and then taxi into takeoff position
    • Crossing the hold short call "Lights" (nav/strobe/landing), "Camera" (transponder), "Action" (mixture/flaps/trim/fuel pump, if required
    • Utilize all runway possible
    • Roll forward slightly to straighten the nose/tailwheel
    • Verify heading indicator/magnetic compass are for that of the active runway
    • Use full yoke to position the flight controls for existing wind conditions
  4. Smoothly and continuously apply full throttle, maintaining directional control and runway centerline with the rudder pedals
    • Applying power too quickly may yaw the aircraft to the left, due to left turning tendencies, most apparent in high-powered engines
    • Lower feet to the floor (toes on rudders, not brakes)
  5. Check engine instruments, airspeed, and tachometer
    • ICS: "Engine instruments in the Green, Airspeed Alive"
    • Keep in right rudder and some left aileron to counteract p-factor crosswind effect as required
  6. As you accelerate, maintain centerline with the rudder and wings level with the aileron
    • Slowly remove aileron inputs as the control surface becomes more effective
    • As you accelerate, the aircraft must be flown and not taxied, requiring smaller inputs
  7. At Vr, call out, "Vr, Rotate" and increase control yoke back pressure to pitch up until the top of the glare shield meets the horizon (approx. 9-10°)
    • Smoothly pitch up or the aircraft may delay a climb
    • Forcing the aircraft off the ground may leave it stuck in ground effect or stall
    • During gust conditions, the pilot should remain on the deck a little longer
  8. After liftoff, establish and maintain Vy while maintaining the flight path over the runway centerline
    • Trim as necessary
    • Use of the rudders will be required to keep the airplane headed straight down the runway, avoiding P-factor
    • The remainder of the climb technique is the same used for normal takeoffs and climbs
  9. With a positive rate of climb and no available landing area remaining, depress the brake pedals, call out, "Positive Climb"
  10. During climb out (no less than 200' AGL), lower the nose momentarily to ensure that the airspace ahead is clear, and then reestablish and maintain Vy, maintaining the flight path over the extended runway centerline
    • Trim as necessary
    • Avoid drifting off centerline or into obstructions, or the path of another aircraft that may be taking off from a parallel runway
  11. At 500' AGL, lower the pitch (approx. 7-8°) to establish and maintain a cruise climb
  12. Execute a departure procedure or remain in the traffic pattern, as appropriate
    • If remaining in the pattern, keep the auxiliary fuel pump on
  13. Complete the Climb checklist
Crosswind Takeoff
Figure 3: Airplane Flying Handbook, Crosswind Takeoff Roll and Initial Climb

Common Errors:

  • Failure to adequately clear the area prior to taxiing into position on the active runway
  • Using less than full aileron pressure into the wind initially on the takeoff roll
  • Mechanical use of aileron control rather than sensing the need for varying aileron control input through feel for the airplane
  • Premature liftoff resulting in side-skipping
  • Excessive aileron input in the latter stage of the takeoff roll resulting in a steep bank into the wind at liftoff
  • Inadequate drift correction after liftoff
    • Be sure your track over the ground stays aligned with the runway as part of the upwind leg
    • Do not allow the aircraft to drift closer to downwind, as aircraft may be there

Practical Test Standards/Airman Certification Standards:

  • Practical Test Standards/Airman Certification Standards
  • Private Pilot Airplane Land:

    1. Exhibits satisfactory knowledge of the elements related to a normal and crosswind approach and landing with emphasis on proper use and coordination of flight controls
    2. Considers the wind conditions, landing surface, obstructions, and selects a suitable touchdown point
    3. Establishes the recommended approach and landing configuration and airspeed, and adjusts pitch attitude and power as required
    4. Maintains a stabilized approach and recommended airspeed, or in its absence, not more than 1.3 VSO, +10/-5 knots, with wind gust factor applied
    5. Makes smooth, timely, and correct control application during the round out and touchdown
    6. Touches down smoothly at approximate stalling speed
    7. Touches down within the available runway or water landing area, within 400 feet beyond a specified point with no drift, and with the airplane’s longitudinal axis aligned with and over the runway center/landing path
    8. Maintains crosswind correction and directional control throughout the approach and landing sequence
    9. Executes a timely go around decision when the approach cannot be made within the tolerances specified above
    10. Utilizes after landing runway incursion avoidance procedures
    11. Completes the appropriate checklist
  • Private Pilot Airplane Sea:

    1. Exhibits satisfactory knowledge of the elements related to a normal and crosswind approach and landing with emphasis on proper use and coordination of flight controls
    2. Adequately surveys the intended landing area
    3. Considers the wind conditions, landing surface, obstructions, and selects a suitable touchdown point
    4. Establishes the recommended approach and landing configuration and airspeed, and adjusts pitch attitude and power as required
    5. Maintains a stabilized approach and recommended airspeed, or in its absence, not more than 1.3 VSO, +10/-5 knots, with wind gust factor applied
    6. Makes smooth, timely, and correct control application during the round out and touchdown
    7. Contacts the water at the proper pitch attitude
    8. Touches down within the available runway or water landing area, within 400 feet beyond a specified point with no drift, and with the airplane’s longitudinal axis aligned with and over the runway center/landing path
    9. Maintains crosswind correction and directional control throughout the approach and landing sequence
    10. Executes a timely go around decision when the approach cannot be made within the tolerances specified above
    11. Utilizes after landing runway incursion avoidance procedures
    12. Completes the appropriate checklist

Conclusion:

  • Takeoff (and landing) factors are dependent on: thrust, weight, lift, drag, and friction (runway surfaces)
  • After reaching the hold short and completing all checklists you are ready to call for takeoff clearance
    • If ever told to taxi off the active and you receive a subsequent clearance, ensure all takeoff checklists are performed AGAIN
  • Consider filling out a crosswind sheet with the limits of your aircraft to be able to quickly determine if a wind component is within your aircraft's limitations [Figure 4]

References: