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Application of Regulations on Fuel Venting

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Federal Aviation Administration (FAA), DOT.


Policy determination.


This document advises the public of a recent decision by the Federal Aviation Administration (FAA) concerning the application of certain provisions of the regulations regarding fuel venting requirements.


We must receive your comments by August 25, 2011.


This is a notice of a policy determination only. You may send comments identified by Docket Number FAA-2011-0746 using any of the following methods:

  • Federal eRulemaking Portal: Go to and follow the online instructions for sending your comments electronically.
  • Mail: Send comments to Docket Operations, M-30; U.S. Department of Transportation, 1200 New Jersey Avenue, SE., Room W12-140, West Building Ground Floor, Washington, DC 20590-0001.
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Privacy: The FAA will post all comments it receives, without change, to, including any personal information the commenter provides. Using the search function of the docket Web site, anyone can find and read the electronic form of all comments received into any FAA dockets, including the name of the individual sending the comment (or signing the comment for an association, business, labor union, etc.). DOT's complete Privacy Act Statement can be found in the Federal Register published on April 11, 2000 (65 FR 19477-19478), as well as at

Docket: Background documents or comments received may be read at at any time. Follow the online instructions for accessing the docket or go to Docket Operations in Room W12-140 of the West Building Ground Floor at 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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Curtis Holsclaw, Office of Environment and Energy (AEE-2), FAA, 800 Independence Ave., SW., Washington, DC 20591; e-mail, facsimile (202) 267-5594, telephone (202) 267-3575.

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Title 14 of the Code of Federal Regulations (14 CFR), part 34, § 34.11 is the regulation that prohibits fuel venting, the intentional discharge to the atmosphere of fuel drained from fuel nozzle manifolds after engines are shut down. By its terms, the regulation does not apply to normal fuel seepage from shaft seals, joints, and fittings.

During a recent aircraft certification, the FAA became aware of difficulties in applying the language of § 34.11 to the newest designs of aircraft engines. The Boeing Models 747-8, 747-8F, and 787 series airplanes incorporate new General Electric (GE) Model GEnx-2B and GEnx-1B engines, respectively. These GE engines include an advanced technology fuel system that significantly reduces fuel consumption and emissions. This technology incorporates the use of a larger, complex fuel manifold and a new fuel nozzle design that also uses check valves as an alternative to a fuel manifold drainage collection tank as a means to prevent release of fuel after shutdown. While this design reduces overall emissions, flight tests revealed an intermittent, inadvertent release of a small amount of Start Printed Page 44458fuel after the engines were shut down. This release of fuel is caused by unexpected elevated fuel manifold pressures that result in the release of fuel from the fuel nozzles. Under certain atmospheric conditions this release of fuel results in a visible vapor. This event was not observed during the GEnx engine's certification testing under 14 CFR part 33, but only after it was installed and operated on the subject airplanes.

Following these observations, the FAA reconsidered how the provisions of § 34.11 should be applied under the circumstances of these certifications. A review of the history of the section found that it was promulgated in 1973 in response to short-sighted environmental practices of the time, including the routine dumping of up to a gallon of raw fuel onto the ground after engines were shut down. The general prohibition in § 34.11 is stated in the first sentence of that section, that “[n]o fuel venting emissions shall be discharged into the atmosphere from any new or in-use aircraft gas turbine engine subject to the subpart.” The second sentence appears to condition this prohibition, stating that “[t]his paragraph is directed at the elimination of intentional discharge to the atmosphere of fuel drained from fuel nozzle manifolds after engines are shut down and does not apply to normal fuel seepage from shaft seals, joints, and fittings.” The language of the second sentence presents a unique situation in aircraft certification by introducing the concept of intent, without clearly referencing where the intent attaches. The second sentence also specifies three locations where “seepage” is considered normal and acceptable.

Historically, application of § 34.11 has not been an issue. Aircraft engines designed since promulgation of the rule have not included any means by which fuel is collected and dispersed outside the engine after shutdown. The GEnx engines at issue do not release fuel from the three locations noted in the regulation—shaft seals, joints, or fittings. Nor does the amount of fuel or the manner in which it is being released rise to the level of historical fuel dumping that prompted the adoption of the regulation in 1973. Yet, small quantities of fuel (up to 5.5 ounces) are being released intermittently under certain conditions, and the fuel is being vaporized on contact with hot surfaces inside the engine, resulting in the visible fuel vapors that have been observed when they emit from either the inlet or exit plane of the engine.

The new engines incorporate technological advances and environmental performance improvements that were never envisioned when the original regulation was adopted in 1973. These factors have made it more difficult to reconcile the design and function of these engines in a certification context with a 38-year-old regulation that was aimed at a different set of circumstances. Application of the current regulation has become less clear in this context.

With the cooperation of the equipment manufacturers, the FAA investigated the safety and environmental effects of the fuel release and vaporization. The FAA consulted with the Environmental Protection Agency (EPA) on the local air quality impacts. While we were satisfied that no safety and minimal environmental effects are evident, we remain concerned about compliance with the intent of the current regulation, and the inability of the current regulation to be unambiguously applied to the certification situation.

The FAA has determined that the best course of action is to allow the current certification of these engine/airframe combinations. The certification basis includes requirements that the manufacturers develop and install modifications that will eliminate these intermittent fuel releases and observed vapors that have been experienced during certification testing. These modifications will apply to newly manufactured airplanes by December 31, 2012, and in-use airplanes by December 31, 2014.

The technological advances incorporated in these engines allow them to more than exceed the separate regulatory requirements for emissions that are the focus of current environmental compliance efforts. The FAA will re-examine the language of the fuel venting regulation and its application during certification to determine whether it needs to be changed to address issues associated with newer technologies. We may consult with the EPA on whether to propose changes to § 34.11 and its companion regulation at 40 CFR 87.11. We will also consider whether more flexibility in application of the regulation is appropriate based on the experience gained during this certification. The decision to proceed with certification of the subject airframe/engine combinations is an effort to acknowledge the lack of clarity in the application of the regulation to the specific circumstances encountered. The requirement to modify the aircraft is intended to prevent any retrenchment from the original regulatory intent.

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Issued in Washington, DC, on July 14, 2011.

Lourdes Q. Maurice,

Executive Director, Office of Environment and Energy.

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[FR Doc. 2011-18191 Filed 7-25-11; 8:45 am]