AC 21-16F RTCA Document DO-160 versions D, E, F, and G, “Environmental Conditions and Test Procedures for Airborne Equipment” AC 23-17B Systems and Equipment Guide for Certification of Part 23 Airplanes and Airships AC 25-7B Chg. 1 Flight Test Guide for Certification of Transport Category A i r p l a n e s AC 25-21 Certification of Transport Airplane Structure AC 25-22 Certification of Transport Airplane Mechanical Systems AC 25.1309-1A System Design and Analysis AC 25.1322-1 Flightcrew Alerting AC 43.13-2B Chg. 1 Acceptable Methods, Techniques, and Practices – Aircraft Inspection and Repair
c. FAA Orders.
Order 8110.4C Type Certification Process (Change 4 incorporated) NOTE: FAA ACs and orders can be obtained electronically from;
Federal eRulemaking Portal; http://rgl.faa.gov/, or from the FAA websites; http://www.faa.gov or http://www.faa.gov/regulations_policies/orders_notices/.
d. Society of Automotive Engineers (SAE) Documents.
SAE AIR-4566-A Crashworthiness Landing Gear Design SAE ARP-1311C Landing Gear Structures and Mechanisms – Aircraft ISO 7137 : 1995 Environmental Conditions and Test Procedures for Airborne Equipment (not an SAE document but is available from the
S A E ) NOTE: These documents can be obtained by mail from the Society of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale, Pennsylvania, 15096; or electronically from the SAE International website, http://www.sae.org/.
e. RTCA Documents.
RTCA/DO-160G Environmental Conditions and Test Procedures for Airborne equipment, Issued December 6, 2007 RTCA/DO-178B Software Considerations in Airborne Systems and Equipment Certification, Issued December 1, 1992 NOTE: Copies of RTCA documents may be purchased by mail from the RTCA Inc., 1150 18th Street NW, Suite 910, Washington, DC 20036; by fax, after completing the Document Order Form and faxing to 202-833-9434; or electronically from the RTCA online store at: http://www.rtca.org/onlinecart/.
f. Military Documents.
MIL-STD-810F Environmental Test Me thods and Engineering Guidelines NOTE: This document can be obtained by mail from the Department of Defense, DODSSP, Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094; or electronically from the DODSSP website at:
http://dodssp.daps.dla.mil/.
g. European Aviation Safety Agency Documents.
EASA Certification Specifications (CS) and Acceptable Means of Compliance (AMC) for CSs are available on the EASA website, http://easa.europa.eu/agencymeasures/certification-specifications.php.
4. Definitions. For definitions of VSR, VSR1, and VC, see 14 CFR part 1 §1.2, Abbreviations and symbols.
5. Background. Amendment 25-136 revised § 25.729(a) through (f) to harmonize part 25 with CS 25.729. The amendment adopted the mo re stringent of the two requirements.
6. Discussion and Demonstration of Compliance.
a. Intent of Rule. (Ref. § 25.729, Retracting mechanism). This rule provides minimum design and certification requirements for landing gear actuation systems to address:
(1) Structural integrity for the nose and main landing gear, retracting mechanism(s), doors, and gear supporting structure for loads imposed during flight, (Ref. § 25.729(a)(1)(ii)(iii)),
(2) Positive locking of the kinematic mechanisms, (Ref. § 25.729(b)), 5
(3) Redundant means of extending the landing gear, (Ref. § 25.729(c)),
(4) Demonstration of proper operation by test, (Ref § 25.729(d)),
(5) Gear up-and-locked and down-and-locked position indications and aural warning, (Ref. § 25.729(e)(2)(5)),
(6) Equipment damage from tire burst, loose tread, and wheel brake temperatures, (Ref. §§ 25.729(f)(1)(2), 25.731(d), and 25.735(j)).
b. Demonstration of Retracting Mechanism Proper Functioning (Ref. § 25.729(d), Operation test). Guidance addre ssing flight testing used to demonstrate compliance with this section may be found in AC 25-7B Change 1 “Flight Test Guide for Certification of Transport Category Airplanes,” chapter 4, section 4, paragraph 52, issued December 7, 2011.
c. Retracting Mechanism Indication (Ref. § 25.729(e), Position indicator and warning device).
(1) When light indicators are used, they should be arranged so that:
(a) A green light for each unit is illuminated only when the unit is secured in the correct landing position.
(b) An alert consistent with § 25.1322 is illuminated at all times, except when the landing gear and its doors are secured in the landing or retracted position.
(2) The alert required by § 25.729(e)(2) should be consistent with § 25.1322 and operate regardless of the position of wing leading-or trailing-edge devices, or the number of engines operating.
(3) The design should be such that nuisance activation of the alert required by § 25.729(e)(2) is minimized, for example:
(a) When the landing gear is retracted after a take-off following an engine failure, or during a take-off when a common flap setting is used for take-off and landing;
(b) When the throttles are closed in a normal descent; or
(c) When flying at low altitude in clean or low speed configuration (special operation).
(4) Inhibition of the alert required by § 25.729(e)(2) above a safe altitude out of final approach phase either automatically or by some other means to prevent these situations is acceptable, but it should automatically reset for a further approach.
(5) Means to de-activate the alert required by § 25.729(e)(2) may be installed for use in abnormal or emergency conditions provided that it is not readily available to the flight crew, that is, the control device is protected against inadvertent actuation by the flight crew and its deactivated state is obvious to the flight crew.
d. Protection of Equipment on Landing Gear and in Wheel Wells (Acceptable Means of Compliance) (Ref. § 25.729(f), Protection of equipment in wheel wells).
(1) The use of fusible plugs in the wheels is not a complete safeguard against damage due to a bursting tire.
(2) Where brake overheating could be damaging to the equipment in the wheel wells, an indication of brake temperature should be provided to warn the pilot.