REFERENCE NO: AW600-31-2456, Rev. 1 INFORMATION TYPE: Maintenance 

Operational

ATA: 31-31 EFFECTIVITY: Challenger 604 (5301 to 

5665)

SUBJECT: Challenger 604 FAR 135 Flight Data Recorder 

Sampling Rate 

AW600-31-2456  Basic Issue: September 9, 2014  Revision 1: October 7, 2014

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1. REFERENCES:

1.1. Bombardier Request for Exemption to Part 135 Appendix F - FDR Normal Acceleration parameter 

requirement for Challenger CL-600-2B16 (Challenger 604 variant) Aircraft.

1.2. Individual Exemption Request Letter template (attached)

2. INTRODUCTION:

Bombardier petitioned for a Request for Exemption (ref. 1.1) from the FAA to Part 135 Appendix F - FDR 

Normal Acceleration parameter requirement for Challenger CL-600-2B16 (Challenger 604 variant) Aircraft. 

Any aircraft operating under Part 135 is affected, and any Challenger 604 operator flying under Part 135 

rules must apply for, and obtain, an exemption until the solution is installed.

3. DESCRIPTION:

Bombardier recently identified a potential recording issue with one of the sampling parameters for 

Challenger 604 aircraft operated under Part 135 operating rules. Specifically, it was discovered that the 

normal acceleration sampling rate is recorded by the FDR at the required rate of 0.125 seconds (eight 

times per second). However, the source data is provided to the FDR at a rate of 0.2 seconds per sampling 

(five times per second). Normal acceleration data is provided through the DCU-4002. The baseline 

Challenger 604 aircraft has two such units, and a third DCU is optional per Service Bulletin 604-31-001.

It is Bombardier’s position that the data from the existing DFDR can be correlated to match the sampling 

requirements of Appendix F (Normal Acceleration) without compromising the information recorded. All 87 

other regulated parameters have been confirmed to record at the range, accuracy, and sampling rates 

specified in Appendix F. Both Bombardier and the FAA have confirmed that this information is not 

necessary for the safe operation of the aircraft, and is primarily used to support investigations of incidents 

or accidents.

Based on the above, Bombardier submitted a petition on May 15, 2014 to the FAA on behalf of affected US

customers operating under Part 135, requesting that a time-limited exemption be granted to allow 

continued operations until a permanent solution to the issue is incorporated. We have recently been 

informed by the FAA, however, that this exemption request has been denied due in part to a lack of 

information on the affected operators and the FAA’s general policy not to grant exemptions to 

manufacturers on behalf of operators.

Therefore, affected operators must submit a petition for exemption for their own aircraft. To facilitate this, 

Bombardier has prepared the attached Individual Exemption Request Letter template (ref. 1.2), which can 

be filled in with specific operator information and submitted to the FAA via the http://www.regulations.gov

website.
AW600-31-2456  Basic Issue: September 9, 2014  Revision 1: October 7, 2014

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4. ACTION:

Affected Operators should submit their petition for exemption as outlined below.

There is no action to take if (a) you are operating under FAR PART 91 or (b) your aircraft was 

manufactured before August 19, 2000 (pre-aircraft 5465). If you are operating a non-FAA registered 

aircraft, please note that, at the present time, Bombardier has had no indication from any other 

airworthiness authority that there is a requirement to address this situation.

Petition for Exemption process

a. Log on to http://www.regulations.gov

b. Enter FAA-2007-0001 in the SEARCH window

c. Select the “Comment Now” button next to “Instructions for Filing a Submission to FAA for 

applications/petitions/exemptions and any other item for which a Docket does not exist.”
AW600-31-2456  Basic Issue: September 9, 2014  Revision 1: October 7, 2014

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d. Paste the following text in the “Comment” box:

Request for an Exemption from 14 CFR 135.152 "Appendix F to Part 135—Airplane Flight Recorder 

Specification", specifically the requirement to meet the parameter "5. Normal acceleration (Vertical)" 

sampling rate of 8 times per second. This is due to being advised that certain DFDR systems 

installed in CL604 aircraft by Bombardier have been found to only sample this specific parameter at 

5 times per second. 

The request is a request for relief so that affected aircraft may continue to operate while Bombardier 

engineers a solution to the issue. The DFDR is a recording tool and does not affect the safe 

operation of the aircraft. It is an important tool for accident investigations, and even though does not 

meet the specific parameters for 14 CFR 135 operations, it does exceed what is required for 14 

CFR 91 operations, and will still continue to provide useful data if needed.

e. Upload your completed Individual Exemption Request Letter 

f. Fill in the requested contact information and follow the remaining instructions