Chapter 15-Transition to Jet Powered Airplanes |
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Table of Contents General Jet Engine Basics Operating the Jet Engine Jet Engine Ignition Continuous Ignition Fuel Heaters Setting Power Thrust to Thrust Lever Relationship Variation of Thrust with RPM Slow Acceleration of the Jet Engine Jet Engine Efficiency Absence of Propeller Effect Absence of Propeller Slipstream Absence of Propeller Drag Speed Margins Recovery from Overspeed Conditions Mach Buffet Boundaries Low Speed Flight Stalls Drag Devices Thrust Reversers Pilot Sensations in Jet Flying Jet Airplane Takeoff and Climb V-Speeds Pre-Takeoff Procedures Takeoff Roll Rotation and Lift-Off Initial Climb Jet Airplane Approach and Landing Landing Requirements Landing Speeds Significant Differences The Stabilized Approach Approach Speed Glidepath Control The Flare Touchdown and Rollout |
THE FLAREThe flare reduces the approach rate of descent to a more acceptable rate for touchdown. Unlike light airplanes, a jet airplane should be flown onto the runway rather than ôheld offö the surface as speed dissipates. A jet airplane is aerodynamically clean even in the landing configuration, and its engines still produce residual thrust at idle r.p.m. Holding it off during the flare in a attempt to make a smooth landing will greatly increase landing distance. A firm landing is normal and desirable. A firm landing does not mean a hard landing, but rather a deliberate or positive landing. For most airports, the airplane will pass over the end of the runway with the landing gear 30 û 45 feet above the surface, depending on the landing flap setting and the location of the touchdown zone. It will take 5 û 7 seconds from the time the airplane passes the end of the runway until touchdown. The flare is initiated by increasing the pitch attitude just enough to reduce the sink rate to 100 û 200 feet per minute when the landing gear is approximately 15 feet above the runway surface. In most jet airplanes, this will require a pitch attitude increase of only 1 to 3 . The thrust is smoothly reduced to idle as the flare progresses. 15-22 Ch 15.qxd 5/7/04 10:22 AM Page 15-23The normal speed bleed off during the time between passing the end of the runway and touchdown is 5 knots. Most of the decrease occurs during the flare from each cockpit are different because window geometry and visibility are different. The geometric relationship between the pilotÆs eye and the landing gear will be different for each make and model. It is essential that the flare maneuver be initiated at the proper heightùnot too high and not too low. Beginning the flare too high or reducing the thrust too early may result in the airplane floating beyond the target touchdown point or may include a rapid pitch up as the pilot attempts to prevent a high sink rate Figure 15-25. Extended flare. |
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