September 11 , 2013 U.S. Department of Transportation Docket Operations West Building, Room W12

- 140 1200 New Jersey

Avenue, S.E. Washington, D.C. 20590 Subject: Petition for Exemption,

Delta Engineering for Project ODA

- 2337

- 01 Title 14 CFR § 25. 571(e) ( 1) , amendment 25

- 96 Subject: R equest for immediate exemption from Title 14 CFR § 25

. 571 (e)(1) bird strike substantiation to Vc

. 

### Introduction: Ina ccordance with Title 14 CFR Part 11, Delta Engineering is petitioning for an immediate exemption fro m Title 14 CFR § 25. 571 (e)(1) showing that the aircraft is capable of completi ng a flight after impact with a 4 pound bird with relative speed of Vc. Delta Engineering’s STC project, ODA

- 2337

- 01 is for the installation of a Panasonic GCS antenna sy stem, under a large composite radome, on a Boeing 737

- 900ER aircraft. Delta Engineering wants to use Vmo in place of Vc for compliance with Title 14 CFR § 25.571 (e)(1). Title 14 CFR § 25. 571 (e)(1) amendment 25

- 9 6 states, “ Impact with a 4

- pound bird when the velocity of the airplane relative to the bird along the airplane’s flight path is equal to Vc at sea level or 0.85 Vc at 8,000 feet , whichever is more critical; ” As provided in Title 14 CFR § 25. 1 5 05 Vc can equal Vmo ; a lso Vmo is established as the maximum speed that is not to be deliberately exceeded. Vmo is published and FAA approved in the Airplane Flight Manual and the Ty pe Certificate Data Sheet, A16WE

. Whereas Vc is not a published number , available to the public and wh en provided we may not been able to trace to the TCDS. 

### Supporting data for the requested exemption : In NPRM 55 FR 29756 the FAA provided a position the Vmo was not appropriate since Vmo is an operational speed whereas Vc is a design speed. Although keeping the design criteria consistent is a good objective it does not necessaril y change the level of safety. As provided above Vc is allowed to be equal to Vmo. S ince the event of striking a bird is related to the operation of the aircraft using the maximum operational speed of the aircraft vs design speed of the aircraft does not reduce the level of safety

. T itle 14 CFR 25.571(e) requires correc tive action by

the flight crew, if necessary , after the bird strike which could include further operation al speed limitations.Title 14 CFR §25.1505 requires the establishment of maximum operating airspeed (Vmo) which is not allowed to be greater than Vc , but Vc can equal Vmo

. T itle 14 CFR §25.1505 also establishes that only inadvertent operations of the aircraft are allowed to exceed Vmo. Title 14 CFR §25.571 prior to amendment 72 required “Impact with a 4

- pound bird at likely operational speeds at altitudes up to 8,000 f

eet”. The aircraft ty

pe certificated prior to amendment 72 have not been shown to be unsafe or more suspect to bird strike. For aircraft that were certified using 25.571 prior to amendment 72 compliance, a speed of 250 knots has been used as the likely o perational speed. A lthough, an operational speed of 250 knots is possible, 250 knots is the likely speed below 10,000 feet. The FAA has granted multiple time limited exemptions from Title 14 CFR 25.571(e)(1) for the same ty pe alterations. F AA Exemption 10847, 10848, 10849, 10851, etc. The se exemptions remove compliance with Title 14 CFR § 25.571 (e)(1) for a period of one year. The FAA would not grant exemption from 25.571(e)(1) if the aircraft was unsafe, even for one ye ar. 

### Proposed Requirements for Equivalent level of safety: Since the aircraft is not allowed to normally operate above Vmo ensuring compliance with Title 14 CFR §25.571(e)(1) using Vmo will not i mpact the level of safety. The non

- traceable manufacturers data presented to Delta Eng ineering indicates Vc=Vmo. Delta Engineering wants to the following wording for Title 14 CFR §25.571(e)(1) “Impact with a 4

- pound bird when the velocity of the airplane relative to the bird along the airplane’s flight path is equal to Vmo at sea level or 0.85 Vmo at 8,000 feet , whichever is more critical” 

### Public Interest: Granting this exemption would benefit the public because some of the manufactures consider the Vc data as proprietary

data and will not disclose the information. Without the manufacturers Vc data, this will impact the ability of modifying aircraft that require compliance with 25.571(e)(1) and the applicant using later amendment levels. Granting this request for exemption would not adversel y affect safety because of the extremely low p robability

of a bird strike when the aircraft

. And the aircraft is not to be operated at speeds above Vmo

. T he aircraft operator is aware of Vmo limitation because of the visual and audible warnings.


### Conclusion: Although using Vc for compliance with Title 14 CFR 25.571(e)(1) is more consistent, using Vmo does not reduce the level of safety. Delta Engineering wants to the following wording for Title 14 CFR §25.571(e)(1) “Impact with a 4

- pound bird when the velocit y o f the airplane relative to the bird along the airplane’s flight path is equal to Vmo at sea level or 0.85 Vmo at 8,000 feet , whichever is more critical”

Sincerel y,John A. Moritz Delta Engineering 13 DRBA Way New Castle County

Airport New Castle, Delaware 1 9720 Phone (302) 325

- 9337 E Mail jamoritz@delta

- engineering.com