Understanding Vref and Approach Speeds

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UNDERSTANDING VREF AND APPROACH SPEEDSEMPRESA BRASILEIRA DE AERONUTICA S.A.

THIS DOCUMENT INCLUDES ALL REQUIRED INFORMATION TO CLARIFY EMBRAERS OPERATIONAL PHILOSOPHY REGARDING APPROACH SPEEDS. THIS MANUAL IS APPLICABLE TO EMB-145, EMBRAER 170 AND EMBRAER 190 FAMILIES OF AIRPLANES.

GP1971 APRIL 26, 2004REVISION 6 SEPTEMBER 20, 2010Copyright 2010 by EMBRAER - Empresa Brasileira de Aeronutica S.A.. All rights reserved. This document shall not be copied or reproduced, whether in whole or in part, in any form or by any means without the express written authorization of Embraer. The information, technical data, designs and drawings disclosed in this document are property information of Embraer or third parties and shall not be used or disclosed to any third party without permission of Embraer.

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LIST OF EFFECTIVE PAGESORIGINAL ............0 ........... APR 26, 2004 REVISION ............1 ........... SEP 20, 2005 REVISION ............2 ...........OCT 10, 2005 REVISION ............3 ...........AUG 11, 2006 REVISION ............4 ........... SEP 21, 2007 REVISION ............5 ............ JUL 01, 2008 REVISION ............6 ........... SEP 20, 2010

* Title ................ REVISION 6 0-LEP * 1..................... REVISION 6 2..................... REVISION 4 0-TOC 1..................... REVISION 5 2..................... REVISION 4 GP 1..................... REVISION 4 2..................... REVISION 4 3..................... REVISION 4 4..................... REVISION 4 5..................... REVISION 4 6..................... REVISION 4 7..................... REVISION 4 8..................... REVISION 4 9..................... REVISION 4 10................... REVISION 4 11................... REVISION 4 * 12................... REVISION 6 * 13................... REVISION 6 14................... REVISION 5 15................... REVISION 5GP-1971

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UNDERSTANDING VREF AND APPROACH SPEEDSTABLE OF CONTENTSINTRODUCTION .................................................................................. 1 SECTION I - LANDING REGULATIONS ............................................. 1 FAR/JAR 25.125 - LANDINGS........................................................ 1 FAR 121.195/JAR OPS 1.515 - FIELD LENGTH LIMIT WEIGHT ........................................................................... 3 LANDING DATA PRESENTATION................................................. 4 SECTION II - WIND EFFECTS ............................................................ 5 UNIFORM WIND MODEL DISTRIBUTION..................................... 5 VARIABLE WIND MODEL DISTRIBUTION .................................... 7 VERTICAL WIND DISTRIBUTION IN THE REAL WORLD.......... 10 SPEED MARGIN TO VREF DURING THE APPROACH ................ 11 SECTION III - APPROACH SPEEDS................................................. 12 SECTION IV - VAPP CONSIDERATIONS ........................................... 13 VAPP MINIMUM VALUE ................................................................. 13 VAPP MAXIMUM VALUE ................................................................ 14 ABNORMAL/EMERGENCY PROCEDURES ............................... 15 SECTION V - CONCLUSIONS........................................................... 16

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INTRODUCTIONThe main purpose of this publication is to clarify Embraers operational philosophy regarding approach speeds by providing sufficient background theory to aid operators with their own operational policy related to this topic. This publication provides guidelines only and does not annul, amend or complement instructions recommended in the Airplane Flight Manual.

SECTION I LANDING REGULATIONSBefore establishing any definition about approach speeds, we must first understand how a landing is defined under current civil aviation regulations, especially factors that must be accounted for.

FAR/JAR 25.125 - LANDINGS(a) The horizontal distance necessary to land and to come to a complete stop from a point 50 feet above the landing surface must be determined (for standard temperatures, at each weight, altitude, and wind within the operational limits established by the applicant for the airplane) as follows: (1) The airplane must be in the landing configuration. (2) A stabilized approach, with a calibrated airspeed of VREF, must be maintained down to the 50 feet height. VREF may not be less than: (1) 1.23 VS1g. (2) VMCL (Minimum Control Speed in Air on landing configuration). (3) A speed that provides maneuvering capability on approach and landing. As per the text above, the first statement that validates all the certified landing data is CROSSING THE THRESHOLD WITH VREF at a height of 50 ft.

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During certification, the actual landing distance is demonstrated as follows: Standard temperature. Landing configuration: landing gear and flaps set for landing. Stabilized approach at VREF. Changes in configuration, power or thrust, and speed, must be made in accordance with the established procedures for service operation. Determination on a level, smooth, DRY and hard-surfaced runway. The landing must be made without excessive vertical acceleration, tendency to bounce, nose over, ground loop, porpoise, or water loop. If any device is used that depends on the operation of any engine (such as thrust reversers), and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating. The reverse thrust effect is not accounted for during Embraer airplane landing certification. The landing may not require exceptional piloting skill or alertness. The pressure on the wheel braking systems may not exceed those specified by the brake manufacturer (maximum braking capability) and may not be used so as to cause excessive wear of brakes or tires. Means other than wheel brakes may be used if that means: Operation is reliable and safe; Operation is such that consistent results can be expected in service; and is such that exceptional skill is not required to control the airplane. In regards to Embraer airplanes, other braking resources means the use of spoilers on ground.

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FAR 121.195/JAR OPS 1.515 - FIELD LENGTH LIMIT WEIGHTThe LANDING FIELD LENGTH regulations require that the landing distance on a DRY RUNWAY, based on a landing weight assuming normal fuel consumption, must not exceed 60% of the available landing distance. Thus, there is a 40% stopping margin to the end of the runway. In other words, the LDA (landing distance available) published for a specific runway must be 1.67 (or 1/0.60) longer than the actual landing distance. For WET runways, the minimum required length must be the dry runway required length increased by 15%. As the dry runway required length is the dry actual landing distance multiplied by 1.67, the WET runway required length is the dry actual landing distance multiplied by 1.92 (=1.67x1.15). The wet runway landing condition demonstration is not required during certification flight tests.DRY RUNWAY

V=0 50 ft

ACTUAL DRY DISTANCE DRY FIELD LENGTH = 1.67 X ACTUAL DRY DISTANCE

FIGURE 1: DRY RUNWAY CERTIFICATIONWET RUNWAY

50 ft

ACTUAL DRY DISTANCE DRY FIELD LENGTH = 1.67 X ACTUAL DRY DISTANCE WET FIELD LENGTH = 1.92 X ACTUAL DRY DISTANCE 15%

FIGURE 2: WET RUNWAY CERTIFICATIONGP-1971

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LANDING DATA PRESENTATIONThe LANDING FIELD LENGTH LIMITED WEIGHT presented in the AFM or Airport Analysis Software is the maximum weight at which the airplane is capable of landing in 60% of the available runway length under DRY conditions. It is important to know that flight-testing is performed on DRY runways only. The WET runway condition is not evaluated during flight-testing and the values contained in the AFM are calculated by adjusting the DRY condition parameters. Special certifications, such as slippery and contaminated runways, require additional flight tests and may present reverse thrust considerations, depending on certification parameters. The landing data shown in the AFM must include correction factors for winds. They cannot be more than 50% of the nominal wind components along the landing path opposite to the direction of landing, and not less than 150% of the nominal wind components along the landing path in the direction of landing. For FAA and EASA certification purposes, ice accretion corrections must be applied to VREF should icing conditions on landing be encountered or predicted and, as a result, all the landing data presented in the AFM should be adjusted.

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