Discussion
What Events Have Caused This AD?
The Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified FAA that an unsafe condition may exist on certain Socata Model TB 21 airplanes. The DGAC reports three occurrences in which carbon monoxide levels in the cockpit have been found to be above specified tolerance levels during certain flight configurations. Carbon monoxide is entering the cockpit from the rear part of the fuselage.
This condition resulted from a design problem and all three occurrences were discovered prior to delivery of any of the affected airplanes. The modification required in this AD is being applied at the factory for all other Model TB 21 airplanes not affected by this AD.
What Is the Potential Impact if FAA Took No Action?
This condition, if not corrected, could result in high levels of carbon monoxide entering the cockpit during certain flight configurations. High levels of carbon monoxide in the cockpit could result in the pilot becoming incapacitated or impairing his/her judgement. Such a condition could lead to the pilot not being able to make critical flight safety decisions and result in loss of control of the airplane.
Has FAA Taken Any Action to This Point?
We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Socata Model TB 21 airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on July 2, 2002 (67 FR 44401). The NPRM proposed to require you to modify the exhaust system.
Was the Public Invited to Comment?
The FAA encouraged interested persons to participate in the making of this amendment. The following presents the comment received on the proposal and FAA's response to the comment.
Comment Issue: AD Is Not Warranted
What Is the Commenter's Concern?
The commenter states that any Model TB airplane with a properly maintained exhaust system should not have a problem with high levels of carbon monoxide entering the cockpit. The commenter has accumulated over 1,200 hours time-in-service and 1,000 landings, including slow and normal flight conditions, on an affected airplane and has not experienced high levels of carbon monoxide in the cockpit. The commenter believes AD action is not necessary.
What Is FAA's Response to the Concern?
We do not concur that AD action is not necessary. We acknowledge that some airplanes may go long periods of time without carbon monoxide problems. However, we continue to receive reports of accident investigations where carbon monoxide poisoning of the crew was a contributor to the accident. Therefore, we have not changed the final rule AD based on this comment.
FAA's Determination
What Is FAA's Final Determination on This Issue?
We carefully reviewed all available information related to the subject presented above and determined that air safety and the public interest require the adoption of the rule as proposed except for the changes discussed above and minor editorial questions. We have determined that these changes and minor corrections:
--Provide the intent that was proposed in the NPRM for correcting the unsafe condition; and
--Do not add any additional burden upon the public than was already proposed in the NPRM.
Cost Impact
How Many Airplanes Does this AD Impact?
We estimate that this AD affects 13 airplanes in the U.S. registry.
What Is the Cost Impact of This AD on Owners/Operators of the Affected Airplanes?
We estimate the following costs to accomplish the modification:
Labor cost
Parts cost
Total cost per airplane
Total cost on U.S. operators
3 workhours x $60 = $180.
$260
$440.
$440 x 13 = $5,720.
Regulatory Impact
Does This AD Impact Various Entities?
The regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.
Does This AD Involve a Significant Rule or Regulatory Action?
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the 2 criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. FAA amends Sec. 39.13 by adding a new AD to read as follows: