1、_ 6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRUWLVSX EOLVKHGE6$(WRDGYDQFHWKHVWDWHRIW echnical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, LVWKHVROHUHVS
2、RQVLELOLWRIWKHXVHU SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2016 SAE International All rights reserved. No part of this publication may be reproduced
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4、-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5938 AEROSPACE INFORMATION REPORT AIR5938 Issued 2011-11 Reaffirmed 2016-11 Information on Hard Landings R
5、ATIONALE AIR5938 has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS 1.SCOPE 2 2.REFERENCES 2 2.1Applicable Documents 22.2Definitions / Abbreviations 3 3.BACKGROUND OF LANDING DESIGN REQUIREMENTS 5 4.HARD LANDING EVENT SEQUENCES 6 4.1Civil (Part 25) Aircraft 64.2USA
6、F Aircraft 94.3USN Carrier Based Aircraft . 114.4Rotorcraft 114.5Others . 12 5.INSPECTIONS 12 5.1Types of Damage 125.2Landing Gear Visual Inspections 125.3Landing Gear Non Destructive Inspections 145.4Rolling Stock Inspections 145.5Non Landing Gear Inspections . 15 6.INCIDENCE DATA ON HARD LANDINGS
7、FOR COMMERCIAL TRANSPORTS 15 6.1NTSB Accidents and Incidents . 156.2FAA/USN Landing Parameter Surveys . 166.3Summary of Hard Landing Incidence Rates . 19 SAE INTERNATIONAL AIR5938 Page 2 of 20 1. SCOPE This document provides information on the current practices used by commercial and military operat
8、ors in regards to hard landings (or overload events designated as hard landings). Since detailed information on inspections would be aircraft specific, this AIR provides only a general framework. Detailed information and procedures are available in the maintenance manuals for specific aircraft. Beca
9、use hard landings potentially affect the entire aircraft, guidelines are listed here for non-landing gear areas. But, the primary focus of the document is the landing gear and related systems. The document may be considered to be applicable to all types of aircraft. This document does NOT provide re
10、commended practices for hard landing inspections, nor does it provide recommendations on the disposition of damaged equipment. Refer to ARP 4915 and ARP 5600. Also, this document does not necessarily address overloads from circumstances other than landings, such as from tow vehicles, runway bumps, t
11、raversing cables, etc. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of the other publications shall be the issue in effect on the date of the purch
12、ase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available
13、 from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AIR 4566 Crashworthy Landing Gear Design ARP 4915 Disposition of Landing Gear Components Involved in Accidents/Incidents ARP 5600 Disposit
14、ion of Damaged Wheels Involved in Accidents/Incidents ARP 5908 Landing Gear Servicing 2.1.2 AIA Publications Available from Aerospace Industries Association, 1000 Wilson Boulevard, Suite 1700, Arlington, VA 22209-3928, Tel: 703-358-1000, www.aia-aerospace.org. AIA Pub 05-01 Best Practices Guide, Ins
15、pection Procedures Following High Load Events 2.1.3 FAR Publications Available from Federal Aviation Administration, 800 Independence Avenue, SW, Washington, DC 20591, Tel: 866-835-5322, www.faa.gov. FAR 23 Federal Aviation Regulations - Airworthiness Standards: Normal, Utility, Acrobatic, And Commu
16、ter Category Airplanes, para. 23.473 “Ground load conditions and assumptions” FAR 25 Federal Aviation Regulations - Airworthiness Standards: Transport Category Airplanes, para. 25.473 “Landing load conditions and assumptions” SAE INTERNATIONAL AIR5938 Page 3 of 20 FAR 27 Federal Aviation Regulations
17、 - Airworthiness Standards: Normal Category Rotorcraft, para. 27.725 “Limit Drop Test” FAR 29 Federal Aviation Regulations - Airworthiness Standards: Transport Category Rotorcraft, para. 29.725 “Limit Drop Test” 2.1.4 Other Publications AS8860 Landing Gear Structural Requirements as Listed in the MI
18、L-886X Series of Specifications CS 23 Certification Specifications For Normal, Utility, Aerobatic, and Commuter Category Aeroplanes, para. 23.473 “Ground load conditions and assumptions CS 25 Certification Specifications for Large Aeroplanes, para. 25.473 “Landing load conditions and assumptions” CS
19、 27 Certification Specifications for Small Rotorcraft, para. 27.725 “Limit Drop Test” CS 29 Certification Specifications for Large Rotorcraft, para. 29.725 “Limit Drop Test” SAWE Recommended Practice 7 Mass Properties Management and Control for Military Aircraft DOT/FAA/AR-97/106 Video Landing Param
20、eter Survey- Washington National Airport DOT/FAA/AR-00/72 Video Landing Parameter Survey- Honolulu International Airport DOT/FAA/AR-96/125 Video Landing Parameter Survey - John F. Kennedy International Airport DOT/FAA/AR-04/47 Commuter Aircraft Video Landing Parameter Surveys, Summary Report - Londo
21、n City Airport, Philadelphia International Airport, and Atlantic City International Airport DOT/FAA/AR-07/53 Video Landing Parameter Survey- Summary Report, LHR Heathrow International http:/www.ntsb.gov/ntsb/query.asp NTSB Aviation Accident Database 2.2 Definitions / Abbreviations Accident: The NTSB
22、 defines Accident as an occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked, and in which any person suffers death or serious injury, or in which the aircraft rece
23、ives substantial damage. AIA: Aerospace Industries Association AMM: Aircraft Maintenance Manual Autoland: A system that fully automates the landing portion of an aircraft flight for low visibility and bad weather conditions. CLDGW: Carrier Landing Design Gross Weight The aircraft maximum gross weigh
24、t specified for landing / arrestment operations on an aircraft carrier. CG: center of gravity DLW: Design Landing Weight The highest aircraft gross weight corresponding to the maximum required sink rate. This definition is common for both military and commercial land based fixed wing aircraft and ro
25、torcraft. EASA: European Aviation Safety Agency FAA: Federal Aviation Administration FPI: Fluorescent penetrant inspection SAE INTERNATIONAL AIR5938 Page 4 of 20 Hard Landing: The term Hard Landing can have multiple definitions. It can refer to the report or declaration of a landing event, where it
26、is suspected that the landing gear or airframe structure, were possibly subjected to damage. Also, a Hard Landing declaration is not necessarily limited specifically to the touchdown event. For aircraft which rely on pilot declaration, a hard landing may be declared based on other landing-related ev
27、ents such as flat tires, rolling off the runway, a heavily rolled landing, etc. Hard Landing can also be used to describe those relatively few events where design landing conditions were truly exceeded resulting in damage or injury. Incident: The NTSB defines Incident as an occurrence other than an
28、accident, associated with the operation of an aircraft, which affects or could affect the safety of operations. LLDGW: Landplane Landing Design Gross Weight This term is used in military applications and is equivalent to the DLW. Typically, the following guidelines are used to establish LLDGW. For u
29、tility, observation, and trainer aircraft, LLDGW = maximum flight weight minus the following: payload to be expended, all external fuel, and 25% internal fuel. For cargo aircraft, LLDGW = maximum flight weight minus: all external fuel and 50% internal fuel. For combat aircraft, LLDGW = maximum fligh
30、t weight minus: all external fuel and 60% internal fuel. MLG: Main Landing Gear MLW: Maximum Landing Weight (commercial) The term MLW, used in a commercial environment, is synonymous with the DLW and corresponds to the highest gross weight for a 10 ft/s (3.05 m/s) landing for transport airplanes. Th
31、e limit sink rate for part 23 aircraft is 7 to 10 ft/s. It is NOT the same as the military definition of Maximum Landing Weight. MLW: Maximum Landing Weight (military) The highest allowable weight for any landing. Typically, it is established by maximum flight weight minus any droppable external fue
32、l tanks and fuel consumed or dumped during one go-around or 3 minutes, whichever provides the lightest aircraft weight. The military MLW term corresponds to the highest gross weight for a 6 ft/s (1.83 m/s) or 8.5 ft/s (2.59 m/s) landing depending on aircraft type. MTOGW: Maximum Takeoff Gross Weight
33、 NDI: Non Destructive Inspection NLG: Nose Landing Gear NTSB: National Transportation Safety Board OEM: Original Equipment Manufacturer Overload: A condition or event which may have subjected the landing gear or airframe structure to damaging loads. Overweight Landing: A touchdown event occurring at
34、 a landing weight above the maximum certified landing weight for that aircraft. Other landing parameters such as the sink rate, side loads, strut servicing condition, etc. are not factors in declaring an overweight landing. S: As used in FAR 23 sink rate equation, S is the reference wing area in uni
35、ts of square feet for English units or square meters for SI units SI: System Internationale SAWE: International Society of Allied Weight Engineers USN: United States Navy W: As used in FAR 23 sink rate equation, W is the aircraft gross weight in units of lb. for English units or kg for SI units SAE
36、INTERNATIONAL AIR5938 Page 5 of 20 3. BACKGROUND OF LANDING DESIGN REQUIREMENTS The table below describes the limit sink rates and aircraft gross weights used for various types of aircraft. For the land based fixed wing aircraft, these limit sink rates are for zero roll angle, zero roll rate, and 10
37、0% lift conditions. TABLE 1 LANDING DESIGN REQUIREMENTS Aircraft Type Gross Weight Limit Sink Rate, ft/s Limit Sink Rate, m/s FAR 23 Design / Maximum Landing Weight 4.4 (W/S)0.25 Must be t7 Need not exceed 10 0.902 (W/S)0.25 * Must be t2.133 Need not exceed 3.05 m/s FAR 25 Design / Maximum Landing W
38、eight 10 3.05 Max Takeoff Gross Weight 6 1.83 US Land Based Fighter / Bomber DLW (Landplane Landing Design Gross Weight) 10 3.05 Maximum Landing Weight 6 1.83 US Land Based Trainer DLW (Landplane Landing Design Gross Weight) 13 3.96 Maximum Landing Weight 8.5 2.59 US Ship Based Fixed Wing Carrier La
39、nding Design Gross Weight See note* N/A FAR 27 Max Takeoff Gross Weight 8 2.44 FAR 29 Max Takeoff Gross Weight 6.55 2.00 US Military Rotorcraft Various; refer to applicable requirements 12 (design) 3.66 (design) * Note: Gross weight (W) must be in kg and reference wing area (S) must be in m2 for thi
40、s equation * Note: landing sink rates are design values, unique to the aircraft, based on multivariate analysis accounting for approach speed, roll rate, ship motion, etc. Typical values for design sink rate are 25 28 ft/s. For commercial transport applications, landing gear design landing loads are
41、 governed by the following regulations. The first part of FAR 25.473 states “the airplane is assumed to contact the ground 1) in the attitudes defined in 25.479 and 25.481; 2) with a limit descent velocity of 10 ft/s (3.05 m/s) at the design landing weight; and 3) with a limit descent velocity of 6
42、ft/s (1.83 m/s) at the design take-off weight. This requirement and those defined for side and drag loads in 25.479, 481 and 485 establish the threshold above which hard landing events occur. For commercial small airplane applications, landing gear design landing loads and the threshold above which
43、hard landings occur, are governed by the following regulations: FAR 23.471, 23.473, 23.479, 23.481 and 23.485. On land based US military applications, the design loads are given in AS8860 (formerly the MIL-L-886X series). Background information is also available in JSSG 2006 and JSSG 2009 Appendix A
44、. For trainers, the limit sink rates are 13 (3.96 m/s) and 8.5 ft/s (2.59 m/s) at LLDGW and MLW respectively. All other classes of aircraft have limit sink rates of 10 (3.05 m/s) and 6 ft/s (1.83 m/s) for those same weights. Also, the landing gear design limits shall not be exceeded by landing at 15
45、% higher sink rates as long as the weights are 15% lower. The conventional military aircraft criteria differ slightly from the commercial requirement in that the 6 ft/s sink rate applies at a Maximum Landing Weight and not necessarily at the takeoff weight. US Navy design requirements for landing lo
46、ads also come from AS8860, section 3.1.4.8. For carrier based aircraft, the analysis involves a complex multivariate check of probabilities of various factors to establish a design sink rate. The typical sink rate is between 25 and 28 ft/s (7.62 and 8.53 m/s). Note that USN carrier applications trea
47、t landing loads as design loads, not as limit / ultimate loads like US Air Force and commercial applications. SAE INTERNATIONAL AIR5938 Page 6 of 20 4. HARD LANDING EVENT SEQUENCES 4.1 Civil (Part 25) Aircraft The typical hard landing inspection sequence for commercial aircraft is shown in Figure 1.
48、 The upper section of the figure addresses those conditions normally reported by the flight crew. One set of causes is what is commonly thought of when referring to hard landings. They include conditions during the touchdown event: high sink rate, high roll angle or roll rate, bounced landing, or high de-rotation rate onto the nose gear. Another set of causes listed are secondary events which may require a hard landing inspection. They
