Course Review
·In a slipping turn, the airplane is not turning at the rate appropriate to the bank being used, since the airplane is yawed toward the outside of the turning flight path. The airplane is banked too much, so the horizontal lift component is greater than the centrifugal force.Equilibrium between the horizontal lift component and centrifugal force is reestablished by either decreasing the bank, increasing the rate of turn, or a combination of the two changes.
·A skidding turn results from an excess of centrifugal force over the horizontal lift component, pulling the airplane toward the outside of the turn. The rate of turn is too great for the angle of bank. Correction of a skidding turn involves a reduction in the rate of turn, an increase in bank, or a combination of the two changes.
·A slip occurs when the bank angle of an airplane is too steep for the existing rate of turn. It usually is the result of insufficient rudder when entering or recovering from a turn, inadvertently holding top rudder while turning, or not keeping the wings level while maintaining heading. The airplane flies sideways, and those inside tend to lean toward the low wing (as does the ball of the slip/skid indicator).
·A skid, on the other hand, is the result of excessive rudder application. A skidding airplane also flies somewhat sideways, and those inside tend to lean opposite to the yaw (as does the slip/skid ball).
·The most significant difference between a slip and a skid becomes apparent when the airplane is made to stall while skidding. The excessive rudder being applied may cause the airplane to spin in the direction of yaw. No difference exists between an intentional spin and one that results from an inadvertent skid. The necessary pro-spin force is the same in each case.
·Intentional slips are used to dissipate altitude without increasing airspeed and/ or to adjust airplane ground track during a crosswind. Intentional slips are especially useful in forced landings and in situations where obstacles need to be cleared during approaches to confined areas. A slip can also be used as a means of rapidly reducing airspeed in situations where wing flaps are inoperative or not installed.
·Slips can be invaluable during an approach to a forced landing, an emergency means of speed reduction, to compensate partially for inoperative flaps, to assist in closing a door that pops open, and to divert smoke and flames from an engine fire away from the co*ckpit.
·An airplane in a slip is in fact flying sideways through the air even though it may appear to be going straight over the ground. This results in a change in the direction that the relative wind strikes the airplane. Because the airplane is banked, the vertical component of lift is reduced allowing for an airplane in a slip to descend rapidly without an increase in airspeed.
·Most airplanes exhibit the characteristic of positive static directional stability and, therefore, have a natural tendency to compensate for slipping. An intentional slip usually requires deliberate cross-controlling of ailerons and rudder throughout the maneuver.
·There are two types of intentional slips: sideslip and forward slips. Sideslips are frequently used when landing with a crosswind to keep the airplane aligned with the runway centerline. A sideslip is entered by lowering a wing and applying just enough opposite rudder to prevent a turn. The amount of slip, and therefore the rate of sideward movement, is determined by the bank angle. The steeper the bank, the greater the degree of slip. As the bank angle is increased, additional opposite rudder is required to prevent turning.During a crosswind landing, the airplane is banked into the wind so that the sideslip velocity is equal and opposite to the crosswind velocity (zero drift).
·The purpose of a forward slip is to increase the rate of descent by increasing drag without increasing airspeed, and a sideslip is to land in a crosswind.
·The airplane doesn’t know whether it’s in a forward slip or a sideslip—the only difference is that with a sideslip, the ground is moving under the airplane in the direction the landing gear wheels roll.
·Because of the airflow (ram or venturi) at the static port, airspeed indicators may not be reliable during a slip. An airplane that has two static ports – one on each side – balances out these forces and is more reliable during a slip. This can be observed by opening the alternate static source during a slip.
·Generally, there is nothing wrong with slipping with flaps extended. Some airplanes, however, because of airflow blanking of the tail surfaces recommend that slips not be accomplished when flaps are extended.
·A spin is more likely to result from stalling the airplane in a skid than it is from stalling the airplane during a slip. A stall during a slip poses little hazard. If an airplane in a slip is made to stall, it displays very little tendency to yaw one way or the other. The airplane may tend to roll into a wings-level attitude, but that is about it. In fact, in some aircraft, stall characteristics are improved.
·During a slip, the ball on the slip-skid indicator is toward the side with the lowered wing or inside the turn. During a skid, the ball on the slip-skid indicator is toward the side with the high wing or outside the turn. Mnemonic: “Slip into the turn. Skid away from the turn.” Drag is increased during a slip because the airplane’s longitudinal axis is at an angle to the flight path.
·Slipping turns occur when the nose is yawed away from the turn. A skid results from the application of too much rudder during a turn. This can be resolved by either relaxing the rudder and/or increasing the bank angle without increasing rudder input.
·When practicing stalls, it is most critical to avoid a spin by not skidding the airplane during the stall. A spin is much more likely to occur during a skidding turn than a slipping turn.
·During a slipping stall, a high-wing airplane will lose rudder authority, and a low-wing airplane will lose aileron authority.
·The indicated airspeed at which an airplane will stall is higher during a slip.
·Pilots should avoid slipping (or skidding) with a low fuel supply because the maneuver could result in unporting a fuel pump or fuel line, thereby starving an engine of fuel.
·Acceleration is a change in velocity. Velocity consists of two components: 1) a direction and 2) a magnitude. A change in direction or magnitude is considered acceleration. An airplane that is turning is accelerating.
·In a yaw-damper-equipped airplane, turn off the yaw damper before performing slips.
·When slipping an airplane to lose altitude and you have a crosswind, you can bank (slip) in either direction, but banking into the wind sets you up for the sideslip direction that will be required for landing, and it will not be necessary to change the direction of the slip prior to landing.
·Inadvertent stall/spin accidents continue to occur because pilots turning from base to final approach subconsciously apply “inside” rudder to increase the rate of turn without increasing their bank angle. A steeper bank would be preferable to a skidding turn. Better yet—over-fly the final approach and fly back to it in coordinated flight.
·Airplanes with electronic flight displays (glass co*ckpits) have a bar under the sky pointer that acts the same as the ball on a conventional slip-skid indicator. The bar gets its data from AHRS and accelerometers. One bar width is equal to one ball width displacement on a turn and slip indicator.
