OIT_999.0046_12_00.txt

OPERATOR INFORMATION TRANSMISSION - OPERATOR INFORMATION TRANSMISSION

SUBJECT: ATA 31 - FDR Brake pressure (LH & RH) parameter recording issue

OUR REF.: 999.0046/12 DATED 05 Jun 2012.

OIT CATEGORY: AIRWORTHINESS

NOTICE: This OIT provides information on continuous airworthiness subjects or 

documents. It is each Operator's responsibility to distribute this OIT, or to 

distribute the information contained in this OIT, to all of their applicable 

Maintenance and Engineering organizations for information and application of the

recommendation.

REFERENCED DOCUMENTS:

Ref.1: Airbus OIT 999.0112/97 REVISION 03 DATED 21 DEC 2000

Ref.2: Airbus Petition letter for Exemption, FAR 121.344, Appendix M to FAR 

121.344, Parameter 68 "Brake Pressure (left and right)", reference: 

SA31M12009739

Ref.3: Airbus - Exemption/Rulemaking Document ID: FAA-2012-0429-0001 Docket ID: 

FAA-2012-0429

1. PURPOSE

The aim of this OIT is to inform all A320 family operators about a recording 

issue affecting #Brake Pressure# parameter M68 in the Flight Data Recorder (FDR)

and the impact on the compliance with FAA rule 14 CFR 121.344 Appendix M.

2. APPLICABILITY

All A320 family aircraft fitted with Sagem or Teledyne FDIU software with a 256 

words/second recording speed.

The 256 w/s recording speed is activated with MOD 32339 (SB 31-1212) or MOD 

32452 (SB 31-1384).

Aircraft fitted with a 1024 words/second FDR recording speed are not impacted by

this parameter M68 issue.

1024 words/second FDR recording speed is activated with optional MOD 151637, MOD

151680 or MOD 153923. No standard SB is available.

3. BACKGROUND

FDIU software with a 256 words/second recording speed were developed to add 

several parameters on FDR and also to comply with FAR 121.344 requirements (see 

Ref.1).

The new parameter M68 #Brake Pressure (left and right)# introduced in the 256 

w/s FDR frame allows to determine pressure delivered to the brakes through brake

pedals or by autobrake system.

The brake pressure data is acquired by FDIU software from the Braking and 

Steering Control Unit (BSCU) and then recorded on FDR M68 parameter. The M68 

parameter is composed of several #sub-parameters# (M68a01 to M68a19) to gather 

information on aircraft braking system.

The M68 parameter definition only takes into account full landing gear 

configuration i.e. with 8 wheels (4 wheels on main landing gear + 4 wheels for 

aircraft fitted with bogie landing gear).

Bogie Landing Gear is installed through MOD 20139 and can be removed with MOD 

22129.

Refer to M68 Parameter Recording Map in Appendix of this OIT.

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OIT_999.0046_12_00.txt

Wheel 1 data is recorded on sub-parameter M68a01, Wheel 2 on M68a02...

For more detailed information about the FDR data frame, refer to Flight Data 

Recording Parameter Library (FDRPL).

The brake pressure data is recorded on FDR Word 61 for LH wheels 1,2,5,6 and 

word 189 for RH wheels 3,4,7,8. The LH & RH brake pressure data is recorded 

every second i.e. once every four second per wheel. This results in following 

recording sequence: LH: 1/2/5/6/1/2... RH: 3/4/7/8/3/4/...

If a bogie landing gear is not installed (i.e MOD 20139 not embodied or MOD 

20139 + 22129 embodied), then the brake pressure data on wheel 5,6,7,8 will be 

recorded as Non Computed Data (NCD). This results in a 2 second data gap within 

the 4 seconds frame (LH: 1/2/x/x/1/2... and RH 3/4/x/x/3/4...).

FAA rule 14 CFR 121.344 Appendix M requires that brake pressure information is 

recorded every second on Left and Right side of the Landing gear. Such a rule is

applicable to all N-registered aircraft produced between 19 AUG 2002 and 06 DEC 

2010. All these aircraft have been delivered with a 256 w/s recording speed FDIU

software(see Ref.1).

The M68 parameter "Brake Pressure (left and right)" is therefore not recorded 

within the required ranges, accuracies, resolutions, and recording intervals 

when aircraft is not fitted with bogie landing gear and is in normal braking 

mode as specified in FAR 121.344, Appendix M.

From 06 DEC 2010, to comply with FAA rule 121.344 Appendix M amendment 121-349, 

new FDIU software with 1024 w/s recording speed were embodied on Airbus 

aircraft. Since recording rate of parameter M68 was increased to 1 second for 

each wheel, these aircraft are therefore not impacted by parameter M68 recording

issue.

4. DESCRIPTION/RECOMMENDATION

Airbus has launched the development of new FDIUs software based on 256 

words/second DFDR recording speed. These software will record on FDR required 

sampling of Normal Brake Pressure (left & Right) independently of the aircraft 

Landing gear configuration (i.e. 4 or 8 wheels).

These new software are planned to be available on Q3 of 2013 through Service 

Bulletins (SB).

Airbus on behalf of affected operators has sent to the FAA a Petition for 

Exemption letter (Ref.2) which has been published by FAA in (Ref.3) document.

http://www.regulations.gov/#!documentDetail;D=FAA-2012-0429-0001 

Operators may use this docket to submit comments or other useful information. 

FAA indicates that exemptions from operational CFR parts (e.g. part FAR 93, part

121) are usually granted to operators only. Therefore, the docket may also be 

used by operators to submit petitions on the same topic.

However, in the current case, FAA may be able to grant exemptions to affected 

operators based on AIRBUS petition. This could be processed by FAA, after AIRBUS

has provided FAA in the course of June 2012 with identification of all affected 

aircraft, registration numbers and owners. Such aircraft list may be shown on 

FAA docket.

For more information on FAR regulation matters such as petition or exemption 

processes, please contact your FAA local representative.

5. FOLLOW UP

Operators will be kept advised of progress on this issue via issuance early June

of a new Technical Follow-Up (TFU) ref 31.33.00.024.

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6. CONTACTS

Questions about the technical content of this OIT are to be addressed to:

Sebastien DE MARCO

Indicating & Recording Systems Engineer - SEEA1

CUSTOMER SERVICES

Phone: +33 (0)5 67 19 52 02

Fax: +33 (0)5 61 93 44 25

Mailto: sebastien.s.de-marco@airbus.com

Best Regards,

Laurent ALEGRE

Head of Avionics & Electrics Department - SEEA

CUSTOMER SERVICES

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Appendix OIT 999.0046/12 dated 05 June 2012

M68 Parameter Recording Map 

Word 1st 2nd 3rd 4th second 

61 Wheel 1 

Left 

Wheel 2 

Left 

Wheel 5 

Left 

Wheel 6 

Left 

189 Wheel 3 

Right 

Wheel 4 

Right 

Wheel 7 

Right 

Wheel 8 

Right 

Main Landing Gear Bogie Landing Gear