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Rule 74.12 Surface Coating of Metal Parts 

and Products (Adopted 11/11/03) 

Rule 74.15 Boilers, Steam Generators and 

Process Heaters (Adopted 11/08/94) 

Rule 74.15.1 Boilers, Steam Generators and 

Process Heaters (Adopted 06/13/00) 

Rule 74.16 Oil Field Drilling Operations 

(Adopted 01/08/91) 

Rule 74.20 Adhesives and Sealants 

(Adopted 01/11/05) 

Rule 74.23 Stationary Gas Turbines 

(Adopted 1/08/02) 

Rule 74.24 Marine Coating Operations 

(Adopted 11/11/03) 

Rule 74.24.1 Pleasure Craft Coating and 

Commercial Boatyard Operations 

(Adopted 01/08/02) 

Rule 74.26 Crude Oil Storage Tank 

Degassing Operations (Adopted 11/08/ 

94) 

Rule 74.27 Gasoline and ROC Liquid 

Storage Tank Degassing Operations 

(Adopted 11/08/94) 

Rule 74.28 Asphalt Roofing Operations 

(Adopted 05/10/94) 

Rule 74.30 Wood Products Coatings 

(Adopted 06/27/06) 

Rule 75 Circumvention (Adopted 11/27/78) 

Rule 101 Sampling and Testing Facilities 

(Adopted 05/23/72) 

Rule 102 Source Tests (Adopted 04/13/04) 

Rule 103 Continuous Monitoring Systems 

(Adopted 02/09/99) 

Rule 154 Stage 1 Episode Actions (Adopted 

09/17/91) 

Rule 155 Stage 2 Episode Actions (Adopted 

09/17/91) 

Rule 156 Stage 3 Episode Actions (Adopted 

09/17/91) 

Rule 158 Source Abatement Plans (Adopted 

09/17/91) 

Rule 159 Traffic Abatement Procedures 

(Adopted 09/17/91) 

Rule 220 General Conformity (Adopted 05/ 

09/95) 

Rule 230 Notice to Comply (Adopted 11/09/ 

99) 

* * * * * 


[FR Doc. E7–22457 Filed 11–15–07; 8:45 am] 


BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 87 

[EPA–HQ–OAR–2007–0294; FRL–8495–4] 

Petition Requesting Rulemaking To 

Limit Lead Emissions from General 

Aviation Aircraft; Request for 

Comments 

AGENCY: Environmental Protection 

Agency (EPA). 


ACTION: Notice of petition for 


rulemaking. 


SUMMARY: Friends of the Earth has filed 

a petition with EPA, requesting that 

EPA find pursuant to section 231 of the 

Clean Air Act that lead emissions from 

general aviation aircraft cause or 

contribute to air pollution that may 

reasonably be anticipated to endanger 

public health or welfare and that EPA 

propose emissions standards for lead 

from general aviation aircraft. 

Alternatively, Friends of the Earth 

requests that EPA commence a study 

and investigation of the health and 

environmental impacts of lead 

emissions from general aviation aircraft, 

if EPA believes that insufficient 

information exists to make such a 

finding. The petition submitted by 

Friends of the Earth explains their view 

that lead emissions from general 

aviation aircraft endanger the public 

health and welfare, creating a duty for 

the EPA to propose emission standards. 

EPA invites information and comments 

from all interested parties on the issues 

raised by this petition. 

DATES: Comments must be received on 

or before March 17, 2008. 


ADDRESSES: Submit your comments, 


identified by Docket ID No. EPA–HQ–


OAR–2007–0294, by one of the 


following methods: 


• www.regulations.gov: Follow the 

on-line instructions for submitting 

comments. 

• Email: a-and-r-docket@epa.gov, 

Attention Docket ID No. OAR–2007– 

0294. 

• Fax: (202) 566–9744 

• Mail. Send your comments to: Air 

and Radiation Docket, Environmental 

Protection Agency, Mailcode: 6102T, 

1200 Pennsylvania Ave., NW., 

Washington, DC 20460, Attention: 

Docket ID No. OAR–2007–0294. 

• Hand Delivery. Deliver your 

comments to: Air and Radiation Docket 

in the EPA Docket Center, (EPA/DC) 

EPA West, Room 3334, 1301 

Constitution Ave., NW., Washington, 

DC, Attention: Docket ID No. OAR– 

2007–0294. Such deliveries are only 

accepted during the Docket’s normal 

hours of operation, and special 

arrangements should be made for 

deliveries of boxed information. 

Instructions: Direct your comments to 

Docket ID No. EPA–HQ–OAR–2007– 

0294. EPA’s policy is that all comments 

received will be included in the public 

docket without change and may be 

made available online at 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI or otherwise 

protected through www.regulations.gov. 

The www.regulations.gov website is an 

‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through 

www.regulations.gov your e-mail 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the Internet. If you 

submit an electronic comment, EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

disk or CD–ROM you submit. If EPA 

cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, EPA may not be 

able to consider your comment. 

Electronic files should avoid the use of 

special characters, any form of 

encryption, and be free of any defects or 

viruses. For additional information 

about EPA’s public docket visit the EPA 

Docket Center homepage at http:// 

www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the docket 

are listed in the www.regulations.gov 

index. Although listed in the index, 

some information is not publicly 

available, e.g., CBI or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, will be publicly 

available only in hard copy. Publicly 

available docket materials are available 

either electronically in 

www.regulations.gov or in hard copy at 

the Air and Radiation Docket in the EPA 

Docket Center, (EPA/DC) EPA West, 

Room 3334, 1301 Constitution Ave., 

NW., Washington, DC, Docket ID No. 

OAR–2007–0294. This docket is open 

from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal 

holidays. The telephone number for the 

Public Reading Room is (202) 566–1744, 

and the telephone number for the Air 

and Radiation Docket is (202) 566–1742. 

FOR FURTHER INFORMATION CONTACT: 

Bryan Manning, Assessment and 

Standards Division, Office of 

Transportation and Air Quality, 2000 

Traverwood Drive, Ann Arbor, MI 

48105; telephone number: 734–214– 

4832; fax number: 734–214–4816; email address: manning.bryan@epa.gov, 

Assessment and Standards Division 

Hotline; telephone number: (734) 214– 

4636; e-mail address: asdinfo@epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. What Should I Consider as I Prepare 

My Comments for EPA? 

1. Submitting CBI. Do not submit this 

information to EPA through 

www.regulations.gov or e-mail. Clearly 

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mark the part or all of the information 

that you claim to be CBI. For CBI 

information in a disk or CD–ROM that 

you mail to EPA, mark the outside of the 

disk or CD–ROM as CBI and then 

identify electronically within the disk or 

CD–ROM the specific information that 

is claimed as CBI). In addition to one 

complete version of the comment that 

includes information claimed as CBI, a 

copy of the comment that does not 

contain the information claimed as CBI 

must be submitted for inclusion in the 

public docket. Information so marked 

will not be disclosed except in 

accordance with procedures set forth in 

40 CFR part 2. 

2. Tips for Preparing Your Comments. 

When submitting comments, remember 

to: 

• Identify the appropriate docket 

identification number in the subject line 

on the first page of your response. It 

would also be helpful if you provided 

the name, date, and Federal Register 

citation related to your comments. 

• Explain your views as clearly as 

possible. 

• Describe any assumptions and 

provide any technical information and/ 

or data that you used. 

• If you estimate potential costs or 

burdens, explain how you arrived at 

your estimate in sufficient detail to 

allow for it to be reproduced. 

• Provide specific examples to 

illustrate your concerns, and suggest 

alternatives. 

• Make sure to submit your 

comments by the comment period 

deadline identified. 

II. The Friends of the Earth Petition 

This notice is seeking comment on 

and information related to a petition for 

an EPA finding and rulemaking and 

collateral relief from the Friends of the 

Earth. This petition is seeking the 

regulation of lead emissions from 

piston-powered general aviation aircraft 

under section 231 of the Clean Air Act. 

The complete petition of Friends of the 

Earth is available from their Web site, 

the docket, from the EPA Web site at: 

www.epa.gov/otaq/aviation.htm, or from 

the individual listed under FOR FURTHER 

INFORMATION CONTACT above. 

Friends of the Earth is an 

environmental advocacy organization 

headquartered in Washington, DC. The 

petition they submitted concerns the 

use of leaded aviation gasoline in 

piston-powered general aviation aircraft 

in the U.S. Friends of the Earth believes 

that ‘‘EPA action regarding lead in 

general aviation aircraft is long overdue. 

Studies increasingly show that lead in 

any quantity threatens the public 

welfare. Lead emissions from general 

aviation aircraft constitute a substantial 

proportion of all current lead air 

emissions. As a result of the use of 

leaded aviation gasoline, humans and 

ecological receptors at or near general 

aviation airports may be exposed to 

elevated levels of lead.’’ 

Friends of the Earth contends that 

‘‘safe unleaded alternatives to aviation 

gasoline do exist. Since 1999, the 

research and development process has 

produced unleaded fuels that have 

received approval from the FAA for 

current use. Tens of thousands of lowperformance aircraft have received 

supplemental type certificates allowing 

them to run on unleaded automobile 

gasoline (commonly referred to as 

mogas in the aviation community). 

Additionally, a mogas alternative, 82UL, 

has been developed for use by some 

low-performance planes. The 

combination of these two fuels can be 

utilized by nearly seventy percent of all 

piston-driven aircraft. Additionally, the 

FAA allows a select number of planes 

to run on an ethanol based aviation fuel 

(AGE85); the remaining thirty percent of 

general aviation planes can potentially 

use this unleaded gasoline.’’ 

The Friends of the Earth petition was 

addressed to EPA. Both EPA and the 

FAA have specific statutorily defined 

roles regarding aviation. EPA through 

section 231 of the Clean Air Act can 

make findings regarding air pollution 

emissions from aircraft and set 

standards regulating such emissions and 

FAA has the statutory authority to 

regulate the fuel used in aircraft (49 

U.S.C. 44714). By this Notice, EPA is 

soliciting comment on the petition, 

specifically on the points discussed in 

the section ‘‘Request for Comments’’ 

presented below. EPA will use this 

information in its statutory assessment 

of whether lead emissions from pistonpowered general aviation cause or 

contribute to air pollution that may 

reasonably be anticipated to endanger 

public health or welfare. 

III. Background Regarding Lead in 

Aviation Fuel 

In a variety of chemical forms and 

exposure pathways, lead has long been 

recognized as causing serious adverse 

health effects. In 1978 EPA established 

a National Ambient Air Quality 

Standard for lead of 1.5 micrograms per 

cubic meter, as a maximum quarterly 

average. Research completed since that 

time, discussed in EPA’s Air Quality 

Criteria Document for Lead (2006) 

indicates that health effects of lead 

occur at blood lead levels lower than 

those previously reported and include 

concerns not previously studied 

(available at www.epa.gov/ncea). The 

adverse effects of lead include 

neurotoxic effects (e.g., IQ loss in 

children), effects on the immune 

system, red blood cell production, 

cardiovascular system, kidney, bones, 

teeth and reproductive and 

developmental systems. EPA is 

currently conducting a review of the 

NAAQS which has included the 

assessment of health and welfare effects 

of lead documented in the Air Quality 

Criteria Document for Lead (2006). 

Integral to the NAAQS review are 

decisions regarding the adequacy of the 

current standard for lead and whether 

the Agency should retain or revise it. 

Consistent with the court order 

regarding this review, the review and 

regulatory development process will be 

completed by September 1, 2008. 

Additional information about the review 

is available at: http://www.epa.gov/ttn/ 

naaqs/standards/pb/s_pb_index.html. 

Thirty-five years ago, cars and trucks 

were the major contributors of lead 

emissions to the air. In the 1970s, EPA 

set national regulations to gradually 

reduce the lead content in gasoline. In 

1974, unleaded gasoline was introduced 

for motor vehicles equipped with 

catalytic converters. EPA banned the 

use of leaded gasoline in highway 

vehicles after December 1995. As a 

result of EPA’s regulatory efforts to 

remove lead from gasoline, emissions of 

lead from the transportation sector have 

dramatically declined (96 percent 

between 1980 and 2005). The large 

reductions in lead emissions from motor 

vehicles have changed the nature of the 

air quality lead problem in the United 

States. Industrial processes, particularly 

primary and secondary lead smelters, 

utility boilers, and battery 

manufacturers taken together, are now 

responsible for most lead emissions into 

the atmosphere. 

Currently, tetraethyl lead (TEL) is 

added to gasoline used in most pistonengine powered aircraft. The 2002 

National Emissions Inventory (NEI) 

estimates that lead emissions from the 

use of leaded aviation gasoline 

(commonly referred to as avgas) are 491 

tons; this accounts for 29 percent of the 

air pollution emissions inventory for 

lead, and is overall, the largest source 

category. This estimate is based on the 

Department of Energy estimate of about 

281 million gallons of avgas supplied in 

the U.S. in 2002 (data available at http:// 

www.tonto.eia.doe.gov/dnav/pet/hist/ 

mgaupus1A.htm). In 2006 the volume of 

avgas supplied in the U.S. was about 

280 million gallons. The majority of 

avgas contains up to 0.56 grams of lead 

per liter (2.12 grams of lead/gallon). 

This is referred to as 100 Low Lead 

(100LL). There is another grade of 100 

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octane avgas that contains 1.12 grams of 

lead per liter, but this product is not 

widely available. 

According to the Federal Aviation 

Administration (FAA) General Aviation 

and Air Taxi Activity and Avionics 

(GAATAA) survey (2005), there were 

over 190,000 piston-engine powered 

aircraft engaged in flight operations in 

the U.S. in 2005; these aircraft 

comprised approximately 90 percent of 

the aircraft in the general aviation fleet. 

In 2005, approximately 29 million 

landing and take-off events (58 million 

total operations) were conducted by 

piston-engine powered aircraft. Among 

the total hours flown by general aviation 

aircraft, about 68 percent occurred in a 

piston-engine powered aircraft. 

According to the General Aviation 

Manufacturers Association (GAMA), 

there were approximately 2,750 new 

piston-engine powered aircraft 

manufactured in 2006. This is the 

largest production volume over the past 

ten years and reflects an average annual 

increase in sales that ranged from eight 

to 43 percent during the preceding 10-

year period except for 2001 and 2002. 

GAMA estimates that the average 

piston-engine powered aircraft is 35–40 

years old. 

Avgas and automotive unleaded 

gasoline are both derived and blended 

from the refining of petroleum. 

However, due to the different nature of 

engine designs and operating 

environments these two types of 

gasoline are different in their chemical 

composition. Avgas is refined and 

blended to meet ASTM specification 

D910 while automotive unleaded 

gasoline (commonly referred to as 

mogas) meets ASTM specification 

D4814. Generally, avgas is transported 

independent of other fuel to avoid crosscontamination and to maintain the tight 

specifications of avgas required for 

proper engine operation in general 

aviation applications. TEL is added to 

avgas to increase octane, prevent 

knock,1 and prevent valve seat recession 

and subsequent loss of compression for 

engines without hardened valves. Lead 

and other additives are added 

downstream of the refinery; most avgas 

is distributed by truck directly from the 

refinery to the bulk gasoline terminals 

or bulk plants or to the storage tanks 

and refueling equipment at airports. 

1 Knocking is the sound produced when some of 

the unburned fuel in the cylinder ignites 

spontaneously resulting in rapid burning and a 

precipitous rise in cylinder pressure that creates the 

characteristic knocking or pinging sound (Chevron 

2005 available at: http:// 

www.chevronglobalaviation.com/docs/ 

aviation_tech_review.pdf). 

Most piston engines used in general 

aviation are type certified by FAA for 

the use of leaded avgas (mostly 100LL). 

The FAA has issued supplemental type 

certificates (STCs) qualifying piston 

engines used in general aviation to use 

unleaded avgas. There are two types of 

unleaded gasoline reflected in these 

STCs. The first type of unleaded 

gasoline which can be used under STCs 

is ethanol-free unleaded automotive 

gasoline (mogas). Most aircraft using 

this mogas have low-compression 

engines which were originally certified 

to run on leaded 80/87 avgas and 

require only 87 antiknock index 

gasoline. The second type is known as 

82UL avgas, which is unleaded fuel 

similar to automobile gasoline but 

without additives. It may be used in 

aircraft that have an STC for the use of 

automobile gasoline with an aviation 

lean octane rating of 82 or less or an 

antiknock index of 87 or less. ASTM 

specification D6227 has been 

established for 82UL but this fuel has 

not yet been produced for general 

distribution.2 About 97 percent of 

gasoline used in piston-engine powered 

aircraft is leaded avgas, mostly 100LL. 

The remaining three percent is ethanolfree unleaded automotive gasoline 

(mogas). 

The Experimental Aircraft 

Association and Petersen Aviation 

estimate that ethanol-free unleaded 

gasoline can be used in approximately 

40 percent of the piston-engine powered 

aircraft fleet (e.g., those aircraft with 

low-compression engines).3 In contrast, 

in order to prevent knock or detonation 

during the combustion process, highcompression piston engines require 

higher octane than typical unleaded 

gasoline provides. These aircraft also 

typically have higher utilization rates 

and fuel consumption rates than their 

low-compression counterparts. The 

AOPA estimates that high-compression 

piston-engine powered aircraft currently 

consume approximately 70 percent of 

the leaded avgas supplied nationally, 

and that the remaining 30 percent of the 

leaded avgas is used in aircraft that 

could also use ethanol-free unleaded 

automotive gasoline. 

Efforts to explore reduced lead 

emissions from piston-engine powered 

aircraft have primarily focused on fuels 

to replace 100LL avgas, with less 

2 82UL has not yet been produced for general 

distribution due to limited demand. It would be a 

fraction of the 100LL market. It is an aviation grade 

product, and thus, refiners can not simply alter 

mogas to make 82UL. 

3 The Experimental Aircraft Association and 

Petersen Aviation data are available at 

www.aviationfuel.org and www.autofuelstc.com/ 

autofuelstc/pa/PetersenAviation.html. 

attention given to potential engine 

modifications. The FAA conducts 

research exploring replacement fuels for 

use in piston-engine powered aircraft at 

its William J. Hughes Technical Center. 

Publications from this research can be 

found at http:// 

www.actlibrary.tc.faa.gov/ by searching 

for ‘unleaded avgas’. The Coordinating 

Research Council has organized the 

Unleaded Aviation Gasoline 

Development Group which brings 

together FAA, AOPA, GAMA, the 

Experimental Aircraft Association, 

airframe manufacturers, engine 

manufacturers, fuel producers and other 

interested parties. The objective of the 

group is to facilitate development of a 

high-octane unleaded aviation gasoline 

as an environmentally compatible, costeffective replacement for the current 

100LL avgas. Documents regarding the 

CRC Unleaded Aviation Gasoline 

Development Group can be found in the 

docket for this notice. 

At the 23rd World Assembly of the 

International AOPA, Lennart Persson of 

Hjelmco Oil in Sweden suggested that a 

91/96 octane unleaded avgas could be a 

transparent switchover for 70 percent of 

the U.S. general aviation fleet. He 

indicated that this fuel would provide 

similar performance to 100LL avgas and 

has done so successfully in Sweden for 

15 years. It is now offered for sale at 70 

locations in Sweden. For more 

information see http://www.iaopa.org/ 

info/assembly23/ppts/persson.pdf 

IV. Request for Comments 

EPA is soliciting public comment on 

any and all aspects of the petition from 

Friends of the Earth regarding issues 

related to the use of lead in general 

aviation gasoline. To assist us in 

developing our response to the petition 

EPA specifically requests information 

and comment on the following. 

1. EPA requests information related to 

human and environmental lead 

exposures and effects around airports. 

Specifically, we request information on 

concentrations of lead in the air, soil, 

surface water or other environmental 

media at or near airports where leaded 

avgas is used. Information regarding 

sources of lead in addition to leaded 

avgas in these areas is also requested. 

2. We request information on levels of 

lead in indoor dust in homes in the 

vicinity of airports where leaded avgas 

is used and information regarding the 

presence of leaded paint in those 

homes. 

3. We request information on blood 

lead levels in children and adults 

residing or attending school in the 

vicinity of an airport where leaded 

avgas is used. 

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4. We request information on the 

characteristics of the populations 

residing in the vicinity of an airport 

where leaded avgas is used, specifically, 

information regarding the number of 

children six years and younger, the 

number of schools, daycare facilities, 

retirement homes, and the 

socioeconomic status of the population. 

5. EPA request information on the 

volume of leaded avgas and unleaded 

aviation gasoline (mogas) supplied at 

individual airports nationwide. 

6. EPA requests comment on locations 

where unleaded aviation gasoline is 

available and the reason for its apparent 

lack of widespread availability. We 

request the submission of information 

related to supplying unleaded aviation 

gasoline at airports and how potential 

fuel distribution issues could be 

addressed. 

7. EPA requests information on the 

characteristics of piston engine general 

aviation operation, including annual 

LTOs by airport, LTO characteristics per 

airport and aircraft/engine type 

including mode, time-in-mode, and fuel 

flow rate in mode. Related to this, EPA 

requests information on the frequency 

and duration of local area flights 

(including touch/go operations) and 

flight durations within the mixing layer. 

8. EPA requests information on the 

disposal of leaded avgas after a pilot 

checks the fuel before starting the 

aircraft. Specifically, we request 

information on how this fuel is 

discarded (i.e., is it deposited on the 

tarmac) or otherwise handled? 

9. Leaded avgas contains ethylene 

dibromide which acts as a scavenger for 

lead by converting lead oxide to lead 

bromide compounds which are volatile 

and easily exhausted from the engine. 

This prevents lead oxide depositing on 

the valves and spark plugs where it 

could damage the engine. EPA requests 

information on the variation in lead 

emission rates at various operating 

modes and power settings and the 

quantity of lead retained in the engine 

and engine oil as a fraction of the lead 

in the fuel combusted. 

10. EPA is requesting comments on 

the potential use of replacement fuels 

for use in piston-engine powered 

aircraft. Approximately 40 percent of 

the piston-engine powered aircraft fleet 

is certified with an STC allowing the 

use of ethanol-free unleaded gasoline 

(82UL or ‘‘mogas’’), but these fuels are 

not widely available at airports. 

Information available to EPA suggests 

that 30 percent of the 100LL avgas 

consumed could be replaced by 

unleaded gasoline. These aircraft are 

equipped with low-compression engines 

that may also run on leaded aviation 

fuel when mogas or 82UL is not 

available. 

11. We request analysis of the 

prospects for developing an unleaded 

fuel for the general aviation fleet that 

will meet the needs of high-compression 

engines, including additional research 

needed. 

12. EPA is requesting comment on the 

viability of a high-octane unleaded 

aviation gasoline in a high-compression 

engine to provide equivalent 

performance and safety to 100LL avgas. 

13. In this context, EPA requests 

comment on the viability of the use of 

ethyl tertiary-butyl ether (ETBE) or other 

octane enhancing compounds for 

unleaded fuel. 

14. We also request information on 

what modifications would need to be 

made to the existing fleet of highcompression engines as well as new 

engines, with appropriate lead time, for 

them to operate on high-octane 

unleaded fuel with an equivalent 

margin of safety. In particular, we solicit 

comment on electronic ignition systems 

(full authority digital engine control) 

and knock (detonation) sensors, 

including comments on further research 

on these technologies. One example for 

consideration is the Teledyne 

Continental Motors/Aerosance 

Powerlink FADEC system. 

15. EPA also requests information on 

the ability of current engines to operate 

on avgas with a decreased lead content 

relative to 100LL, and identification of 

the minimum lead content needed to 

maintain safe engine operation. 

16. EPA requests comment on the 

storage of avgas, specifically, issues 

related to above ground storage capacity 

compared to below-ground storage 

capacity. 

17. EPA requests comment on the 

availability of additives less toxic than 

lead to enhance aviation gasoline 

octane. 

18. We request comment on the longterm availability of TEL as an avgas 

additive. 

19. We request information related to 

the feasibility and costs of any potential 

options for limiting lead emissions from 

existing aircraft. 

20. We request comment on the STCs 

which have been approved to allow for 

the use of unleaded gasoline in general 

aviation, the percent and characteristics 

of the current fleet covered by STCs, 

and obstacles to wider acceptance and 

application of the STCs. 

21. EPA is requesting comment on 

additional research on alcohol-based 

fuels of which we should be aware. The 

FAA has approved a very limited 

number of STCs for use of ethanol-based 

AGE–85 fuel (85% ethanol in 15% 

unleaded gasoline) under a preliminary 

fuel specification. Subsequent approvals 

allowing more widespread use of AGE– 

85 are pending the development of a 

final, aviation-grade fuel specification to 

ensure potential safety concerns with 

the fuel are fully vetted by the FAA and 

the aviation industry. 

22. EPA is requesting comment on 

additional research or information 

regarding the use of diesel engines in 

general aviation, particularly regarding 

equipment changes and the related 

costs. The FAA has approved Type 

Certificates and STCs for diesel-cycle 

engines that use widely-available, 

unleaded jet fuel. 

Before the end of the comment period, 

please send all comments and related 

information to the address indicated in 

the ADDRESSES section at the beginning 

of this notice. 

Dated: November 9, 2007. 

Stephen L. Johnson, 

Administrator. 

[FR Doc. E7–22456 Filed 11–15–07; 8:45 am] 

BILLING CODE 6560–50–P