April 27, 2015

David Jensen

Vice President, Aircraft Maintenance

Aviation Consultants, Inc.

945 Airport Drive 

San Luis Obispo, CA 93401

djensen@acijet.com

US Department of Transportation

1200 New Jersey Ave. SE

West Building Ground Floor, Room W12-140

Washington, DC 20590

Submitted via: www.regulations.gov

Subject: Request for Temporary Exemption to CFR 135.152 Parameter 5 "Normal 

Acceleration"

Dear Sir or Madam,

It was brought to the attention of Aviation Consultants, Inc. Air Carrier Certificate

Number W9BA551H, by Bombardier Aerospace (BA) that certain Digital Flight Data 

Recorder (DFDR) systems certified and installed by BA on certain aircraft are not 

recording a specific parameter listed in 14 CFR 135 Appendix F - "Airplane Flight

Recorder Specification" to the full stated specifications listed for this specified

parameter.

Therefore, in anticipation of suitable rectification by BA, Aviation Consultants, Inc. is 

requesting exemption from the requirements of 14 CFR 135 Appendix F - "Airplane 

Flight Recorder Specification", specifically "5. Normal Acceleration (Vertical)" only. This 

request applies to Bombardier Challenger CL-600-2B16 (CL-604 Variant) manufactured 

after August 18, 2000 and with a DFDR system installed per Bombardier Aerospace 

SB604-31-010 operating under 14 CFR 135 by Aviation Consultants, Inc. 

domestically and abroad, currently one (1) affected aircraft N529KF CL604-5477.
- 2 - April 28, 2015

PETITION FOR EXEMPTION

Specific Section and Extent of Relief Requested

In accordance with 14 CFR 11 Aviation Consultants, Inc., requests an exemption from

the "5. Normal Acceleration (Vertical)" parameter requirements in Appendix F of 14 CFR 

135.152 to permit sampling 5 times (0.2 seconds per sampling interval) per second until

the Data Concentrator Unit (DCU), a subsystem of the affected DFDR system, is 

updated to provide 8 times per second (0.125 seconds per sampling interval) per 

second.

An exemption will have no adverse impact on the safe operation of the aircraft.

The DFDR and its recorded parameters are not required for the safe operation of the 

aircraft. The DFDR's primary purpose is to support investigations in case of accidents.

The affected Normal Acceleration parameter is provided through the DCU. Aviation 

Consultants, Inc. CL604 variant aircraft has/have 2 DCUs. Except for the affected 

Normal Acceleration sampling rate, all data is being collected as required by 14 CFR 

135 Appendix F (e.g. range -3g to +6g, resolution 0.004). The effect is that the normal 

acceleration parameter can be correlated to the appropriate recording rate, as 

described and illustrated below, with no substantive loss of information.

Given that the information can be effectively correlated with no substantive degradation 

in information, we respectfully submit that this compliance issue does not affect the safe 
- 3 - April 28, 2015

operation of the aircraft or hinder potential investigations requiring the DFDR data.

Bombardier Aerospace has committed to developing an in-service solution that involves 

a re-design of the DCU on or before September 20151. Additionally Bombardier 

Aerospace has indicated that a subsequent fleet retrofit period to account for parts 

availability and all affected operators downtime requirements, for a complete retrofit 

within two (2) years of the grant of the exemption. Aviation Consultants, Inc. is 

committed to working with Bombardier Aerospace to effect the final rectification to this 

issue concerning our affected aircraft as soon as practical.

In many cases our affected aircraft are outside the United States for an extended 

period. The public benefit and equivalent level of safety addressed below supporting 

this exemption request have equal applicability to Aviation Consultants, Inc. 

international flights.

The exemption is in the public interest

The problem identified above was found by the aircraft manufacturer (Bombardier), and 

is a systems design problem which CL604 operators have no way to correct at this time. 

Granting this time limited exemption would be in the public interest because it would 

allow U.S. Part 135 operators the ability to continue to provide the unique services that 

support US public, business and industrial leaders while the aircraft manufacturer 

develops and certifies, and the affected CL604 operators incorporate, the modifications 

necessary to bring these aircraft into compliance. This request is substantially similar to 

the Exemption No. 11052 granted to Jet Solutions. L.L.C. in FAA Docket No. 2014-0542 

on September 11, 2014.

Conditions and Implementation

Aviation Consultants, Inc. requests that the FAA to allow continued operation of our

aircraft subject to the conditions specified below:

1. This exemption is valid until the incorporation of the modification correcting the 

deficiency described herein or 24 months from the date of this exemption, 

whichever occurs first, unless previously superseded, rescinded or terminated by 

action of Aviation Consultants, Inc.

2. Copies of this exemption to be retained by Aviation Consultants, Inc., and the

requirement that a copy be provided to the NTSB and FAA in connection with any 

accident or incident where DFDR data is requested or required to be provided; and
- 4 - April 28, 2015

3. Within 90 days of receipt of the Bombardier Aerospace Service Bulletin that 

rectifies the Normal Acceleration parameter issue; Aviation Consultants, Inc. 

must provide a schedule to its FAA CHDO principal avionics inspector (PAl), 

and/or persons designated by the FAA for completion of the new installation within 

the time period of this requested exemption.

Federal Register Summary and Publication

Aviation Consultants, Inc., Air Carrier Certificate number W9BA551H, is requesting

exemption from the requirements of 14 CFR Appendix F of 135.152 to permit the 

sampling rate of 5 times (0.2 seconds per sampling interval) per second2until 

Bombardier Aerospace issues a Service Bulletin that corrects the issue, and in 

accordance with the conditions specified in this exemption request.

This applies to all its CL604 aircraft used in operations under 14 CFR 135. Aviation 

Consultants, Inc. also requests to utilize the exemption outside the United States. It is 

Aviation Consultants, Inc.’s position that safety would not be jeopardized by issuance 

of this exemption as the DFDR is used solely as a recording device in accidents and 

incidents and the affected parameter will still provide useful data in such cases. This 

exemption will benefit the public by allowing U.S. Part 135 operators the ability to 

continue to provide the unique services that support US public, business and industrial 

leaders while the aircraft manufacturer develops and certifies, and the affected CL604 

operators incorporate, the modifications necessary to bring these aircraft into 

compliance.

Due to the immediate and future impact and because this request does not establish 

new agency precedent as it is consistent with the scope of Exemption 11052, Aviation 

Consultants, Inc. requests a waiver to the 120 day filing requirements and the 

publishing of a summary of the petition in the Federal Register.

If there are any questions, please do not hesitate to contact this office at any time.

Thank you,

David Jensen

Vice President, Aircraft Maintenance

1 As indicated by Bombardier and based on the following: "The development schedule takes into account 

current Bombardier and its suppliers resource capacities. The FAA is involved in some of the joint projects, 

including but not limited to the Challenger Avionics upgrade as well as Steep Approach certification and 

operational approval."