This section of the FEDERAL REGISTER

contains notices to the public of the proposed

issuance of rules and regulations. The

purpose of these notices is to give interested

persons an opportunity to participate in the

rule making prior to the adoption of the final

rules.

Proposed Rules Federal Register

42753 

Vol. 80, No. 138 

Monday, July 20, 2015 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2015–2490] 

Bird Strike Requirements for Transport 

Category Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Request for comments on bird 

strike requirements for transport 

category airplanes. 

SUMMARY: This document solicits public 

comments on the need for, and the 

possible scope of, changes to the bird 

strike certification requirements for 

transport category airplanes. The FAA is 

not currently proposing a specific 

regulatory action. The purpose of this 

request is to gather comments from 

airplane manufacturers and other 

interested parties on this subject. 

DATES: Send comments by November 

17, 2015. 

Comments to: Todd.Martin@faa.gov. 

ADDRESSES: Send comments, identified 

by Docket No. FAA–2015–2490, using 

any of the following methods: 

• Federal eRulemaking Portal: Go to 

http://www.regulations.gov 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. 

• Hand Delivery or Courier: Take 

comments 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. 

• Fax: Fax comments to Docket 

Operations at 202–493–2251. 

Privacy: In accordance with 5 U.S.C. 

553(c), DOT solicits comments from the 

public to better inform its rulemaking 

process. DOT posts these comments, 

without edit, including any personal 

information the commenter provides, to 

www.regulations.gov, as described in 

the system of records notice (DOT/ALL– 

14 FDMS), which can be reviewed at 

www.dot.gov/privacy. 

Docket: Background documents or 

comments received may be read at 

http://www.regulations.gov 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. 

FOR FURTHER INFORMATION CONTACT: 

Todd Martin, Airframe and Cabin Safety 

Branch, ANM–115, FAA, Transport 

Airplane Directorate, Aircraft 

Certification Service, 1601 Lind Avenue 

SW., Renton, WA 98057–3356; 

telephone (425) 227–1178; facsimile 

(425) 227–1232; email Todd.Martin@

faa.gov. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

The FAA invites interested persons to 

comment on the need for, and the 

possible scope of, changes to the bird 

strike requirements for transport 

category airplanes by submitting written 

data, views, or arguments as they may 

desire. We have conducted a review of 

bird strike data, and we are considering 

whether to revise the requirements, as 

described in this document. We invite 

comments relating to the technical or 

economic impact that might result from 

any of the rule changes discussed 

herein, as well as any alternative 

suggestions. Substantive comments 

should be accompanied by estimates of 

their economic impact if possible. All 

comments received by the closing date 

for comments will be considered by the 

FAA. 

Background 

Bird strike requirements for transport 

category airplanes are specified in Title 

14, Code of Federal Regulations (14 

CFR), part 25, and vary depending on 

the structural component being 

evaluated. Section 25.775 requires 

windshields and their supporting 

structure withstand, without 

penetration, impact with a four-pound 

bird at VC (design cruising speed) at sea 

level. This regulation has been in place 

and is unchanged since part 25 was 

introduced in 1965. 

Section 25.631 requires the 

empennage structure be designed to 

assure continued safe flight after impact 

with an eight-pound bird at VC at sea 

level, including consideration of control 

system elements. This regulation was 

introduced at Amendment 25–23 

(effective May 8, 1970) as a result of the 

1962 Vickers Viscount accident, which 

was caused by impact with a swan, 

estimated to weigh between 12 and 17 

pounds, that damaged the horizontal 

stabilizer and elevator. 

Section 25.571 considers the rest of 

the airframe and requires the airplane be 

capable of continued safe flight after 

impact with a four-pound bird at VC at 

sea level, and .85 VC at 8000 feet. This 

regulation was introduced at 

Amendment 25–45 (effective December 

1, 1978) with some changes in the speed 

definition since then. A speed criterion 

is provided at 8000 feet to ensure 

adequate bird strike resistance 

capability up to that altitude. 

In 1993, the FAA was developing a 

notice of proposed rulemaking to 

establish a consistent eight-pound bird 

requirement for all structures. The FAA 

decided instead to task the Aviation 

Rulemaking Advisory Committee 

(ARAC) to evaluate the bird strike 

requirements and make 

recommendations. The working group 

completed its deliberations in 2003 

without reaching agreement. All 

members in the working group, except 

the FAA, favored reducing the eightpound bird requirement in § 25.631 to 

four pounds, thus establishing a 

consistent four-pound bird requirement 

for all structures. Other changes to the 

requirements were considered by the 

group, but none were adopted. The 

working group report is available at: 

http://www.faa.gov/regulations_

policies/rulemaking/committees/

documents/media/TAEgshT1- 

031593.pdf. 

More recently, the National 

Transportation Safety Board (NTSB) 

issued the following Safety 

Recommendation to the FAA as a result 

of a fatal Cessna 500 accident that 

occurred in 2008: A–09–072, ‘‘Revise 

the bird-strike certification requirements 

for Part 25 airplanes so that protection 

from in-flight impact with birds is 

consistent across all airframe structures. 

Consider the most current military and 

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42754 Federal Register / Vol. 80, No. 138 / Monday, July 20, 2015 / Proposed Rules 

civilian bird-strike database information 

and trends in bird populations in 

drafting this revision.’’ 

To determine the adequacy of current 

bird strike certification requirements, 

the FAA reviewed a number of reports, 

including the 2003 ARAC report, and 

other reports that address bird 

populations. We also reviewed recent 

bird strike event data and compared the 

energy levels of bird strike events to the 

energy levels prescribed in the current 

requirements. We found numerous bird 

strike events in which the energy level 

exceeded that specified in current part 

25 requirements. 

Sample of Bird Strike Event Data 

The severity of a bird strike depends 

primarily on kinetic energy, which is 

proportional to mass times velocity 

squared. Bird strikes involving birds 

greater than four pounds occur often, 

but usually at speeds below the design 

cruising speed, VC. Therefore, the 

energy level of such strikes is usually 

below that specified in current 

requirements. However, in some cases, 

that energy level is exceeded. 

In each of the bird strike events 

shown below, the FAA estimates that 

the energy level of the strike exceeded 

that specified in current requirements. 

This is not an exhaustive list; these are 

just some examples of events that 

occurred in the US since the 2008 

Cessna accident. For these events, we 

estimated the energy level of the event 

and compared it to the current fourpound bird requirement specified in 

§§ 25.571 and 25.775. 

RECENT EXAMPLES OF BIRD STRIKE EVENTS IN WHICH THE ENERGY LEVEL EXCEEDED THE CURRENT AIRPLANE-LEVEL

STANDARD

[4 Pound Bird at VC] 

1. Energy level approximately 1.8 times current certification standard: 

Date: 4 March 2008. 

Aircraft: Cessna Citation Model 500. 

Airport: Wiley Post (OK). 

Phase of Flight: Climb (3,100′ MSL (mean sea level)). 

Estimated Airspeed: 198 KTAS (knots true airspeed). 

Effect on Flight: Crashed. 

Wildlife Species: American white pelican (mean weight 12.5 lb.). Multiple birds. 

Damage: Aircraft destroyed. Five fatalities. Shortly after takeoff, the airplane flew through a flock of birds. There was no evidence that any 

pieces of the airplane separated in flight. Bird residues were identified on the right horizontal stabilizer and the right side of the vertical 

stabilizer. 

2. Energy level approximately 2.3 times current certification standard: 

Date: 8 April 2008. 

Aircraft: Bombardier Challenger 600. 

Airport: Colorado Springs (CO). 

Phase of Flight: Climb (8,000′ MSL). 

Estimated Airspeed: 260 KTAS. 

Effect on Flight: Precautionary landing. 

Wildlife Species: American white pelican (mean weight 12.5 lb.). Multiple birds. 

Damage: One bird penetrated the fuselage below the cockpit windows, through the forward pressure bulkhead and into the cockpit. Both 

engines ingested at least 1 bird. The #1 engine had fan damage; the #2 engine lost power and had a dented inlet lip. Noise and wind in 

the flightdeck. The left engine had high vibration levels. The fuselage skin and forward pressure bulkhead were penetrated and contained 

bird matter. The left engine thrust reverser torque box assembly and pylon tracks were bent, and the engine cowl supports were broken. 

3. Energy level approximately 1.5 times current certification standard: 

Date: 3 February 2009. 

Aircraft: Boeing 757–200. 

Airport: Denver International (CO). 

Phase of Flight: Climb (7,500′ MSL). 

Estimated Airspeed: 270 KTAS (Airspeed not recorded. Airspeed estimate assumes airplane was flying 10 knots below 250 KIAS speed restriction. At 7500′ MSL, 250 KIAS is approximately equal to 280 KTAS). 

Effect on Flight: Emergency landing. 

Wildlife Species: Bald eagle (mean weight 10.4 lb.). Single bird. 

Damage: Bird hit right side of engine cowling making a large dent before entering the engine where it damaged all fan blades. 

4. Energy level approximately 4.2 times current certification standard: 

Date: 10 August 2010. 

Aircraft: Embraer 145. 

Airport: Salt Lake City International (UT). 

Phase of Flight: Approach (11,000′ MSL). 

Estimated Airspeed: 290 KTAS. 

Effect on Flight: Landed using back up radio. 

Wildlife Species: American white pelican (mean weight 12.5 lb.). Multiple birds. 

Damage: Birds punctured the nose of the aircraft between the nose cone and windshield. The birds damaged the skin, stringers, structural 

mounts and various avionics equipment. One bird penetrated the airplane’s skin and entered the forward avionics bay. The captain lost a 

number of his primary instruments. 

5. Energy level approximately 2.3 times current certification standard: 

Date: 08 November 2010. 

Aircraft: Bombardier DHC–8. 

Airport: Los Angeles International (CA). 

Phase of Flight: Approach (6,600′ MSL). 

Estimated Airspeed: 243 KTAS. 

Effect on Flight: Emergency landing. 

Wildlife Species: Common loon (mean weight 9.1 lb.). Single bird. 

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Federal Register / Vol. 80, No. 138 / Monday, July 20, 2015 / Proposed Rules 42755 

RECENT EXAMPLES OF BIRD STRIKE EVENTS IN WHICH THE ENERGY LEVEL EXCEEDED THE CURRENT AIRPLANE-LEVEL

STANDARD—Continued 

[4 Pound Bird at VC] 

Damage: Bird impact resulted in a 12-inch hole in the right wing leading edge, and internal structural damage to the right wing and fuel 

tank. 

6. Energy level approximately 1.2 times current certification standard: 

Date: 15 November 2010. 

Aircraft: Embraer 170. 

Airport: Minneapolis-St. Paul International (MN). 

Phase of Flight: Climb (5000′ MSL). 

Estimated Airspeed: 270 KTAS. 

Effect on Flight: Precautionary landing. 

Wildlife Species: Snow goose (mean weight 5.8 lb.). Multiple birds. 

Damage: Radome, engine, fuselage. Autothrottle system disengaged. First officer’s primary flight display had alert flags for the indicated 

airspeed and altitude parameters. Substantial damage to the radome and its underlying structural components. The forward pressure 

bulkhead web contained a dent and puncture. The left engine compressor section was damaged. 

7. Energy level approximately 1.4 times current certification standard: 

Date: 01 November 2011. 

Aircraft: Airbus 320. 

Airport: Minneapolis-St Paul International (MN). 

Phase of Flight: Climb (3300′ MSL). 

Estimated Airspeed: 220 KTAS. 

Effect on Flight: Precautionary landing, emergency declared. 

Wildlife Species: Tundra swan (mean weight 14.8 lb.). Single bird. 

Damage: Bird hit right side of nose. Substantial damage to the radome, nose, #2 engine and forward pressure bulkhead. 

8. Energy level approximately 1.8 times current certification standard: 

Date: 25 October 2012. 

Aircraft: Boeing 757–200. 

Airport: Boise Air Terminal (ID). 

Phase of Flight: Climb (14,000′ MSL). 

Estimated Airspeed: 390 KTAS. 

Effect on Flight: Precautionary landing. 

Wildlife Species: Snow goose (mean weight 5.8 lb.). Multiple birds. 

Damage: The radome was penetrated and the bulkhead was punctured. There was extensive damage to the #2 engine. 

9. Energy level approximately 2.2 times current certification standard: 

Date: 12 October 2013. 

Aircraft: Cessna 525. 

Airport: Lincoln (NE). 

Phase of Flight: Climb (6400′ MSL). 

Estimated Airspeed: 220 KTAS. 

Effect on Flight: Precautionary landing. 

Wildlife Species: American white pelican (mean weight 12.5 lb.). Single bird. 

Damage: Substantial damage to the outer right wing spar. 

These event data, including estimated 

airplane altitude and airspeed, are 

derived from the following reports: 

1. The FAA Wildlife Strike Database, 

available at: http://www.faa.gov/

airports/airport_safety/wildlife. 

2. The FAA Aviation Safety 

Information Analysis and Sharing 

(ASIAS) System, available at: http://

www.asias.faa.gov. This includes the 

FAA Accident/Incident Data System, 

and the NTSB Aviation Accident and 

Incident Data System. 

3. National Transportation Safety 

Board. 2009. Aircraft Accident Report: 

Crash of Cessna 500, N113SH, 

Following an In-Flight Collision with 

Large Birds, Oklahoma City, Oklahoma, 

March 4, 2008. Aircraft Accident Report 

NTSB/AAR–09/05. Washington, DC. 

In addition to the events listed above, 

there are hundreds of examples of bird 

strike events in which the energy level 

did not exceed current requirements, 

but substantial damage to the airframe 

occurred. In addition to structural 

damage, major damage to electrical, 

flight control and fuel systems has 

occurred, and there have been dozens of 

incidents in which the flight deck was 

penetrated. 

Bird Population Trends 

The bird strike threat has increased, 

especially the threat due to larger birds. 

In a report commissioned by the FAA, 

Assessment of Wildlife Strike Risk to 

Airframes; Herricks, Mankin, and 

Shaeffer; December 2002; the authors 

wrote, ‘‘The findings of this report, 

supported by other literature, indicate 

that future operational environments for 

aircraft can be expected to contain larger 

numbers of birds, and larger numbers of 

birds with weights greater than four 

pounds.’’ 

According to Wildlife Strikes to Civil 

Aircraft in the United States, 1990– 

2013, US Depts. of Transportation and 

Agriculture, July 2014: ‘‘Many 

populations of large bird and mammal 

species commonly involved in strikes 

have increased markedly in the last few 

decades and adapted to living in urban 

environments, including airports. For 

example, the resident (non-migratory) 

Canada goose population in the USA 

and Canada increased from about 0.5 

million to 3.8 million from 1980 to 2013 

(Dolbeer et al. 2014, U.S. Fish and 

Wildlife Service. 2013). During the same 

time period, the North American snow 

goose population increased from about 

2.1 million to 6.6 million birds (U.S. 

Fish and Wildlife Service. 2013). Other 

large-bird species that have shown 

significant population increases from 

1980 to 2012 include bald eagles (6.4 

percent annual rate of increase), wild 

turkeys (9.5 percent), turkey vultures 

(2.7 percent), American white pelicans 

(7.9 percent), double-crested cormorants 

(6.1 percent), sandhill cranes (5.9 

percent), great blue herons (1.2 percent), 

and ospreys (3.0 percent, Sauer et al. 

2014). Dolbeer and Begier (2013) 

examined the estimated population 

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trends and numbers for the 21 species 

of birds in North America with mean 

body masses greater than 4 pounds and 

at least 10 strikes with civil aircraft from 

1990–2012. Of these 21 species, 17 had 

shown population increases from 1990– 

2012 with a net gain of 17 million birds. 

Previous research had documented that 

13 of the 14 bird species in North 

America with mean body masses greater 

than 8 pounds showed significant 

population increases from 1970 to the 

early 1990s (Dolbeer and Eschenfelder 

2003).’’ 

Airspeed Information 

In the U.S., § 91.117 prescribes a 

speed restriction of 250 knots indicated 

airspeed below 10,000 feet mean sea 

level. The 250 knot speed restriction is 

also in place in Mexico and Canada, and 

in many areas around the world, but not 

everywhere. Where this speed 

restriction is in place, it provides a 

significant safety benefit with respect to 

bird strikes. 

While deviations to this speed 

restriction are allowed, and the 

requirement is not global, it does 

indicate that limiting airspeed below 

10,000 feet is operationally feasible for 

transport category airplanes. Indeed, to 

meet current bird strike criteria, some 

manufacturers specify relatively low 

VMO and VC airspeeds up to 8000 feet, 

that increase above that altitude. These 

speed ‘‘cutbacks’’ at lower altitudes are 

beneficial for three reasons: (1) They 

increase safety by reducing the energy of 

any bird strike that occurs below 8000 

feet, (2) they apply to all airspace, not 

just those areas covered by US operating 

regulations, or those of other countries, 

and (3) they reduce the bird strike 

speeds to which the airplane must be 

designed. 

To encourage these speed cutbacks, 

we believe establishing the bird strike 

speed criteria based on VMO rather than 

VC may be warranted. While most 

structures rules are based on VC, 

allowing these very speed-dependent 

criteria to be based on VMO may make 

the establishment of speed cutbacks 

easier to achieve. 

Summary of FAA Findings 

Our review of bird strike event data 

and bird population data indicates the 

following: 

1. Bird strikes have occurred and will 

continue to occur at energy levels that 

exceed the level provided by current 

requirements. 

2. Numerous bird strikes have 

resulted in penetration into the flight 

deck, mostly below the windshield, 

even at energy levels below current 

requirements. Penetration of the cockpit 

obviously introduces a number of 

significant risks to the airplane. 

Currently, there is no requirement that 

specifically prohibits penetration of the 

flight deck through structure other than 

the windshield. 

3. The bird strike threat has increased, 

especially the threat due to larger birds. 

Therefore, current fleet history may not 

be indicative of what to expect in the 

future. 

4. Bird strike events often involve 

more than one bird. Such multiple bird 

strikes may result in structural damage 

in several areas, pilot disorientation, 

engine failure and systems failures. Any 

one of these effects can significantly 

reduce the controllability of the 

airplane. Sections 25.571 and 25.631 

assume a single bird strike, rather than 

multiple bird strikes. The FAA believes 

that this single bird strike approach is 

an adequate approach for airframe 

structure as long as the single bird strike 

criteria are robust. By showing the 

structure capable of withstanding a 

significant bird strike in any one area, 

a bird strike to that area should not 

compound the hazard from strikes in 

other areas. 

5. Limiting airspeed below 10,000 feet 

is operationally feasible for transport 

category airplanes. Bird strike data 

indicate numerous damaging bird 

strikes have occurred above 8000 feet, 

but above 10,000 feet, bird strikes are 

rare. Therefore, expanding the envelope 

above 8000 feet, but limiting it at 10,000 

feet, may be warranted. 

6. Establishing reduced VMO and VC

airspeeds at lower altitudes provides a 

significant safety benefit with respect to 

bird strikes. 

Request for Comments 

The FAA invites interested persons to 

comment on the need for, and the 

possible scope of, changes to the bird 

strike requirements for transport 

category airplanes by submitting written 

data, views, or arguments as they may 

desire. We invite comments relating to 

the technical or economic impact that 

might result from any considerations 

discussed herein, as well as any 

alternative suggestions. In particular, we 

invite information, comments, and 

opinion on the following questions: 

1. Should the bird weight requirement 

be applied consistently across the 

airplane? 

2. Should the bird weight requirement 

be increased, to eight pounds or some 

other value? 

3. Should a ‘‘no-penetration’’ 

requirement be applied to the entire 

fuselage, not just the windshields? 

4. Should the bird strike criteria be 

expanded to 10,000 feet? 

5. Should the 0.85 speed reduction 

factor at 8000 feet, currently specified in 

§ 25.571, be removed? 

6. Should the speed criterion for bird 

strikes be based on VMO rather than VC? 

Conclusion 

This document solicits public 

comments on the need for, and the 

possible scope of, changes to the bird 

strike certification requirements for 

transport category airplanes. 

List of Subjects in 14 CFR Part 25 

Aircraft, Aircraft safety. 

Issued in Renton, Washington, on June 25, 

2015. 

Jeffrey E. Duven, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2015–17404 Filed 7–17–15; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2015–2462; Directorate 

Identifier 2014–NM–224–AD] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for certain 

The Boeing Company Model 737–100, 

–200, –200C, –300, –400, –500 series 

airplanes. This proposed AD was 

prompted by reports of cracked antenna 

support channels, skin cracking 

underneath the number 2 very high 

frequency (VHF) antenna, and cracking 

in the frames attached to the internal 

support structure. This proposed AD 

would require repetitive inspections to 

determine the condition of the skin and 

the internal support structure, and 

follow-on actions including corrective 

action as necessary. We are proposing 

this AD to detect and correct skin 

cracking of the fuselage which could 

result in separation of the number 2 

VHF antenna from the airplane and 

rapid depressurization of the cabin. 

DATES: We must receive comments on 

this proposed AD by September 3, 2015. 

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