April 23, 2013

Mr. Jonathan Moritz Delta Engineering 13 DRBA Way New Castle, DE 19720 jemoritz@delta-engineering.com (302) 325-9351

Introduction :

Delta Engineering, 13 DRBA Way, New Castle, Delaware 19720, submits this petition, under the provisions provided for in Title 14 Code of Federal Regulations, Part 11, as a petition to grant exemption to Title 14 CFR § 25.251 to change “V d ” to “V mo /M mo with validated CFD to V d ”. Delta Engineering is requesting this exemption for our FAA STC projects that modify the external configuration of the aircraft to install large radome’s. Currently the STC projects us the Equivalent Level of Safety process to allow for flight testing to V mo /M mo with validated Computer Fluid Dynamics to V d

.

Delta Engineering has completed several FAA STC’s with large radome’s with successful results (no affect to 25.251) for example ST02884NY-D, ST02927NY-D, ST02905NY-D, ST02890NY-D, ST03163NY-D for aircraft models 737, 747, 777, A330, A340, A319, A320.

Below table outlines the current 25.251 requirements.

Amendment 25.251 0 (b) Each part of the airplane must be shown in flight to be free from excessive vibration, under any appropriate speed and power conditions up to at least the minimum value of allowed in Sec. 25.335. The maximum speeds shown must be used in establishing the operating limitations of the airplane in accordance with Sec. 25.1505. In addition, it must be show n by analysis or tests, that the airplane is free from such vibration that would prevent safe flight under the conditions in Sec. 25.629(d). 23 (b) Each part of the airplane must be shown in flight to be free from excessive vibration, under any appropriate speed and power conditions up to at least the minimum value of allowed in Sec. 25.335. The maximum speeds shown must be used in establishing the operating limitations of the airplane in accordance with Sec. 25.1505. In addition, it must be show n by analysis or tests, that the airplane is free from such vibration that would prevent safe flight under the conditions in Sec. 25.629(d). 72 (b) Each part of the airplane must be shown in flight to be free from excessive vibration, under any appropriate speed and power conditions up to at least the minimum value of V D allowed in Sec. 25.335. The maximum speeds shown must be used in establishing the operating limitations of the airplane in accordance with Sec. 25.1505. In addition, it must be show n by analysis or tests, that the airplane is free from such vibration that would prevent safe flight under the conditions in Sec. 25.629(d). 77 (b) Each part of the airplane must be demonstrat ed in flight to be free from excessive vibration under any appropriate speed and power conditions up to V DF / M DF . The maximum speeds shown must be used in establishing the operating limitations of th e airplane in accordance with Sec. 25.1505.Current Method used for 25.251 :

Delta Engineering proposes using a validated CFD and performing a flight test to V mo /M mo .

In order to address 14 CFR 25.251 vibration and buffeting requirements, the following will be completed :

1. Perform CFD analysis of the aircraft both with a nd without the radome, at the following speeds : M mo , M Dive and 1.5G recovery at M Dive

. 2. Demonstrate analytically that the aerodynamic flow field does not change significantly between M mo and M Dive

. 3. Include in the flight test plan, flight to V mo and M Mo in order to demonstrate no adverse vibration and buffeting, and no adverse change to handling characteristics due to the radome installation.

4. Extrapolate that the radome installation is aerodynamically insignificant and therefore compliant to 14 CFR 25.251(b).

Public Interest & Safety :

This exemption is in the interest of the public as to allow flight testing for such FAA STC’s to only

V mo /M mo instead of V d with valid CFD to V d

.

This exemption is also in the public interest to avoid FAA resources on creating Equivalent Level of Safety’s for each FAA STC project.

There would be no adverse effect on safety if this petition for exemption was granted as the methods proposed in this exemption are already FAA accepted/approved.

Jonathan Moritz Delta Engineering