1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical 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 there
2、from, is the sole responsibility of the user.” 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 2015 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 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/AIR6441 AEROSPACE INFORMATION REPORT AIR6441 Issued 2015-07 Information on Parkin
5、g Brake Systems RATIONALE The industry requested that general reference information on parking brake system architectures be compiled including a discussion of various parking brake related issues. 1. SCOPE This SAE Aerospace Information Report (AIR) provides information on the parking brake system
6、design for a variety of aircraft including part 23, 25, 27, and 29. The document includes a discussion of key technical issues with parking brakes. This document does NOT provide recommended practices for parking brake system design. 1.1 Purpose This AIR has been prepared by a panel of the SAE A-5A
7、Committee and is presented to document the design approaches and service experience from various applications of parking brake systems. This experience includes commercial and military applications. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the
8、 extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document tak
9、es precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-
10、776-4970 (outside USA), www.sae.org. AS8584A Brake Systems, Wheel, Military Aircraft 2.1.2 Other Publications FAR 25.671 / CS 25.671 General (Control Systems Design most notably during takeoff. If application of the parking brake occurs during the takeoff run, the aircraft will likely not be able to
11、 achieve a safe takeoff. Also, locked wheels could cause tire skid through and potential loss of control. These events may be due to pilot error, poor indication methods, a PB system fault, or a combination of all three. Table 1 Date Location Aircraft Description Source Jun 2010 Leeds (LBA) Citation
12、 CJ1 Brakes dragging on takeoff; PB set with hot brakes causes binding AAIB Report Cessna Citation CJ1+, N646VP Mar 1994 Anchorage AK (ANC) B747-200F PB set for takeoff NTSB Number ANC94IA037 Jan 1990 Cedar Rapids IA (CID) B737-300 PB set for takeoff; rigging out of adjustment NTSB Number CHI90IA070
13、 Jan 1980 Meigs Field (CGX) Falcon 10 PB set for takeoff NTSB CHI80AA024 SAE INTERNATIONAL AIR6441 Page 14 of 19 5.2 PB Applied for Landing Having the PB applied for landing is also a serious hazard. With the brakes locked, a landing aircraft will likely experience tire skid-through and potential lo
14、ss of control. Table 2 Date Location Aircraft Description Source May 2012 Talkeetna, AK (TKA) DHC-2 Landed with PB set NTSB Number ANC12CA041 Aug 2010 Sacramento (SMF) A320-232 Landed with PB set NTSB Number WPR10IA430 Jan 2007 Leeds (LBA) A319 Flt crew set PB for landing instead of full flaps AAIB
15、Report Airbus A319-131, G-DBCI July 2006 Downsville TX Cessna 180 Malfunction of PB locked RH wheel for landing NTSB Number DFW06CA178 Aug 2005 Houston (IAH) ERJ-170 Landed with PB set N/A March 2004 Ft Lauderdale (FLL) A300 Landed with PB set NTSB Number MIA04IA056 5.3 PB Release or Improperly Set
16、Several incidents have occurred because the flight crew believed that the parking brake had been released when in fact it had remained engaged. FAR 25.735 requires that when the parking brake is not fully released this be clearly indicated to the flight crew. Care has been taken in the design of the
17、 parking brake mechanism on most aircraft to ensure that deliberate action is required to release the parking brake. Several incidents described in 5.1 and 5.2 may have been caused by improper release procedures, failed PB indication, inadequate means of indication, or flight crew oversight of a PB
18、indication. Still other incidents have occurred where the parking brake was not set during ground handling operation when it should have been. PB indication, flight crew distractions, and poor communication with ground maintenance personnel often contribute to these occurrences. Table 3 Date Locatio
19、n Aircraft Description Source July 2006 Newark (EWR) ERJ-135 Pushback with PB set NTSB Number NYC06LA191 Feb 2003 Oxford (OXF) TBM 700 PB knob set without applying brake pedals AAIB Report Socata TBM 700B, N700VA Sep 2001 Indianapolis (IND) B757-222 PB not set when disconnecting from tow NTSB Number
20、 CHI01LA331 SAE INTERNATIONAL AIR6441 Page 15 of 19 5.4 Fluid Transfer between Systems In aircraft that use the pedal application type of PB as described in 4.1, the pressure for both normal and parking operations comes from the same hydraulic system. There still may be multiple hydraulic systems in
21、 the aircraft which feed the brake system where fluid transfer must be prevented or addressed. But those issues are separate from the PB system. On the other hand, the independent type of PB as described in 4.2 will often have the source of pressure for parking come from an alternate hydraulic syste
22、m. In those cases, the possibility exists where fluid will migrate from one system to the other as the PB is used. If this condition persists, one system will run low on fluid while the other will have excess fluid. One approach for addressing the fluid crosstalk is to link the reservoirs such that
23、excess fluid in one system will flow back to the low reservoir. That method is not appropriate for part 25 aircraft where separation of fluid systems is required. Table 4 Date Location Aircraft Description Source Dec 1999 Chicago O Hare (ORD) BAE 146 PB fail after pilot transferred fluid between hyd
24、 systems NTSB Number CHI00IA037 5.5 PB Used for Emergency Backup to Normal Braking Using the parking brake as an emergency backup to the normal braking system is sometimes considered in the parking brake system implementation. Note, the PB is not necessarily the first means of backup braking, since
25、many aircraft have alternate braking systems. Still, there are some aircraft that utilize the independent parking brake as described in 4.2 as a final emergency braking feature. With an independent means of applying the brakes, failures in the normal brake system will not affect the ability of the p
26、arking brake to apply brake pressure in an emergency. The parking brake control may have the ability to meter the brake pressure if it is used as an emergency backup such as on the Embraer ERJ-170/190. The parking brake is also used as an emergency backup brake system on the Airbus A320. When the pa
27、rking brake is used as an emergency braking system there is no antiskid protection so the wheels may lock and cause tire skid-throughs if the parking brake is set at speeds greater than 10 knots. These emergency braking systems require a modulating emergency/parking valve for control. Note, sizing r
28、equirements for the emergency braking system to comply with 25.735 and 25.671 may be more stringent than the requirements for the parking brake. 5.6 Thermal Compensation In hydraulic brake systems, an accumulator is used as an energy storage device allowing brake pressure to be applied when the hydr
29、aulic system itself is off or failed. In some smaller aircraft applications, the compliance provided by the accumulator is sufficient to address any thermal changes over long parking periods. In larger systems, thermal compensation during parking is usually provided by check valves incorporated into
30、 the parking brake valve. If the brake cools and contracts after the PB is applied, the brake pressure would otherwise decrease. But, with the check valves in place, the parking pressure will maintain brake pressure at the desired parking level. Likewise, if the PB is applied immediately following a
31、 stop the brake temperature and possibly the brake pressure will tend to increase. A pressure relief valve could be used to allow excess pressure to bleed off. 5.7 Leakage through Control Valves In many aircraft, the parking brake latching feature is upstream of the antiskid valve. An example is sho
32、wn in Figure 4. However, sophisticated control valves like antiskid valves or some brake metering valves are designed for fast response. The penalty for this fast response is excessive leakage to return when the valves are operating. This leakage is not a functional problem under normal braking oper
33、ation when the hydraulic system pump and/or accumulator can compensate for the leakage. But in a parking brake situation, this leakage would quickly deplete the parking pressure. To address the leakage, an isolation valve is put in the return line of the antiskid (or metering) valve. This valve serv
34、es to trap the parking pressure stopping the valve leakage to return. In some applications, this isolation valve is referred to as the parking brake valve. SAE INTERNATIONAL AIR6441 Page 16 of 19 5.8 PB Indication Methods Nearly all of the more serious PB incidents are caused by the cockpit crew not
35、 realizing the actual state of the PB. Examples of having PB pressure mistakenly applied during takeoff or landing are well known. But there are also many cases of the flight crew releasing normal brakes believing that PB pressure was present, only to have the aircraft move and strike another aircra
36、ft or other piece of equipment nearby. A reliable and very obvious means of indication is required to show when parking pressure is applied to the brakes as required by FAR 25.735. Several incidents described in this section may have been caused by failed PB indication, inadequate means of indicatio
37、n, or flight crew oversight of a PB indication. Adequate indication of the PB status to the flight crew is of crucial importance. 5.9 Pneumatic Pressure for PB Some aircraft such as the Cessna Citation use pneumatic pressure as an emergency means of applying the brakes. The pneumatic pressure can be
38、 modulated to bring the aircraft to a stop. No use of pneumatic pressure as a normal means to apply the parking brake is known at this time. 5.10 PB with Dual Cavity Brakes Several aircraft such as the McDonnell Douglas commercial aircraft and Airbus A330/A340 use dual cavity brakes in the brake sys
39、tem. Dual cavity brakes have two sets of pistons that are typically pressurized by separate hydraulic systems thereby ensuring separation of the hydraulic fluid. In the McDonnell Douglas aircraft, both cavities of the brake are active for both normal braking and parking. See Figure 5. Some dual cavi
40、ty brakes are designed such that one set of cavities can generate full stopping force, such as on the Airbus A330/A340. In this type of system only one set of brake hydraulic cavities is pressurized when the parking brake is set. Also, on the A330/340, one set of cavities is intended for normal brak
41、ing while the second set is for emergency braking and parking. This type of system is shown in Figure 8. Both these types of dual systems would prevent fluid transfer between hydraulic systems when parking (refer to 5.4). 5.11 Pedal Braking Availability with PB Set Several aircraft incidents have re
42、sulted when the flight crew could not stop the airplane from moving with the parking brake set because pedal braking was deactivated and there was no hydraulic pressure at the brakes. On these aircraft, if the hydraulic system used to supply pressure to the brakes with the parking brake set is not p
43、ressurized, pedal braking is not available unless the parking brake is released to switch over to the normal braking system. This type of parking brake system has been shown to be problematic. Hydraulic gauges have been placed in the cockpit to indicate to the flight crew the hydraulic pressure avai
44、lable in the parking brake system to preclude this type of incident but the issue is not completely alleviated. Table 5 Date Location Aircraft Description Source June 2010 N/A B777 A/C rolled at gate; PB failed, normal brakes deactivated when PB set N/A June 2009 Old Sarum, Wiltshire UK (EGLS) Aero
45、AT-3 PB set with hyd off making toe brakes inoperative AAIB Report Aero AT-3 R100, G-TGUN April 2006 Heathrow (LHR) A320 Hyd union failure during taxi out; at gate, PB set without pressure, pedal brakes deactivated when PB set AAIB Report Airbus A320-A1, EC-GRF SAE INTERNATIONAL AIR6441 Page 17 of 1
46、9 5.12 Use of Chocks Some aircraft incidents have occurred from the improper use of chocks in combination with the parking brake. In some cases, these incidents are aggravated by inadequate communication between the flight crew and ground maintenance personnel. Table 6 Date Location Aircraft Descrip
47、tion Source Feb 2009 Heathrow (LHR) B777-268 PB valve failure while passengers disembarked AAIB Report Boeing 777-268ER, HZ-AKC Nov 2008 Asheville NC (AVL) Falcon 50 A/C not chocked when pilot released PB NTSB Number ERA09CA122 Oct 2006 Heathrow (LHR) B767 A/C rolled at gate; PB handle improperly se
48、t and chocks not placed AAIB Report Boeing 767, C-GEOU 5.13 Pressure Availability for PB In some cases, the failure of the parking brake function is due simply to the loss of hydraulic pressure in one or more of the applicable aircraft hydraulic systems. 5.14 Rotorcraft Some rotorcraft intentionally
49、 perform sloped and shipboard landings with the parking brake applied. If antiskid is installed on the aircraft, in order to bypass touchdown protection or other antiskid logic, the antiskid system would typically be disabled or bypassed for this event via a flight deck control or specific antiskid logic. Aircraft forward velocity is generally less than 5 knots during the landing. In some instances, prior to landing, the parki
