
[Federal Register Volume 80, Number 138 (Monday, July 20, 2015)]
[Proposed Rules]
[Pages 42753-42756]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-17404]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
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 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.
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 

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

[[Page 42753]]



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 eight-pound bird requirement in Sec.  
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

[[Page 42754]]

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 four-pound bird requirement specified in 
Sec. Sec.  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.

[[Page 42755]]

 
    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

[[Page 42756]]

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., Sec.  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 Sec.  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


