FAR 25.1 Applicability 'This part prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for transport category airplanes.'
In essence FAR 25 does not restrict us as pilots. It is for certification purposes and the configuration changes are to stop manufacturers from using a complex and difficult configuration change in order to certify the aircraft.
Not sure about other countries but in Australia the reg that applies to us is CAO 20.7.1B which covers planning and executing a take off. In our case we need to be able to ensure 35' obstacle clearance on departure and 50' in a turning departure.
It states: 'An aeroplane may be accelerated in level flight from V2 speed to final take-off climb speed at a height above the take-off surface that is the greater of:
(a) 400 feet; or
(b) the height necessary to achieve obstacle clearance in accordance with paragraphs 12.1 and 12.2.'
If you don't need to fly a level segment and still meet the obstacle clearance your good so far. It goes on to say:
14 AEROPLANE CONFIGURATION AND PROCEDURES
14.1 Paragraph 14.1A applies if:
(a) the manufacturer of, or the holder of the type certificate for, an aeroplane
has published advice, recommendations or guidance (the information)about the performance of the aeroplane in an emergency, unusual
operating conditions or an abnormal configuration; and
(b) the aeroplane is in the emergency, conditions or configuration.
14.1A The pilot in command of the aeroplane must take the information into account
when planning the take-off or landing of the aeroplane.
14.1B In subparagraph 14.1 (a), type certificate includes foreign type certificate
within the meaning of paragraph 21.041 (1) of the Civil Aviation Safety Regulations 1998.
14.2 Procedures to be followed consistent with this Order, including procedures
anticipating engine failure at any time between the commencement of take-off
and completion of landing, must be specified in the Operator’s Operation
Manual. The procedures so specified must be such that they can be consistently
executed in service by flight crews of average skill and they must also be such
that the take-off flight path with all engines operating is above the one-engine
inoperative take-off flight path.
How do I interpret all this? Unless the manufacturer has a specific procedure my company needs to have one and that procedure could allow the retraction of flap as soon as you reach flap retraction speed as long as you meet the obstacle clearance OEI and all engines and does not require a level acceleration below 400'.