This is something I have a good bit of experience with. As Colin stated you need a 5 hour test period. Following is a little long, but is copied from a letter I received from my FSDO after asking them the question:
Dear Sir: After a review of order 8130 it has been determined that you must perform a minimum of five hours of flight-testing after incorporating a major change. In addition, due to the nature of the change you have incorporated on your aircraft, you must perform an actual reweigh to determine the correct weight and ballance information. This includes computing the most forward and most aft center of gravity. The following paragraph is the reference used to make this determination. Please advise this office of the proposed flight test area. Do not conduct any flight-testing until you receive verification from this office as to the suitability of the proposed flight test area. (19) After incorporating a major change as described in 21.93, the aircraft owner is required to reestablish compliance with 91.319(b) and notify the geographically responsible FSDO of the location of the proposed test area. The aircraft owner must obtain concurrence from the FSDO as to the suitability of the proposed test area. If the major change includes installing a different make and model of engine or propeller, the aircraft owner must fill out a revised Form 8130-6 to update he aircraft's file in the FAA Aircraft Registry. All operations must be conducted under day VFR conditions in a sparsely populated area. The aircraft must remain in flight test for a minimum of 5 hours or for the time the FSDO assigns. Persons nonessential to the flight must not be carried. The aircraft owner must make a detailed logbook entry describing he change before the test flight. Following satisfactory completion of the required number of flights in the test flight area, the pilot must certify in the records that the aircraft has been shown to comply with 91.319(b). Compliance with 91.319(b) must be recorded in the aircraft records with the following, or a similarly worded, statement: "I certify that the prescribed flight test hours have been completed and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous characteristics or design features, and is safe for operation. The followin aircraft operating data has been demonstrated during the flight testing: speeds Vso____, Vx____, and Vy____, and he weight____, and CG location____at which they were obtained." Sincerely, XXX Aviation Safety Inspector Note that this information is probably also listed in your operating limitations. The starting point is to send a letter of fax to the FSDO, call first and get a name is best, describing the mod and sugesting a test area and suggesting to them a five hour test flight phase in accordance with order 8130. Get their response back IN WRITING before test flying and be sure to put the entry in your log book before when you are done with the test phase. I also called the tech specialists at EAA and they told me that to be in compliance you need to test up to your established max gross weight during the test phase. You also need to reestablish your V speeds which means doing your climb and descent tests and making the graph to get the speeds. I have the faxes I sent to the FSDO if you need any help on the wording. Good luck! Brian Kraut Engineering Alternatives, Inc. www.engalt.com
