If I am a Commercial multi rated pilot with high performance and CFI. But not CFII or MEI, can I give a high performance endorsement to another commercial multi rated pilot in a multi engine?
The thought being since we are both multi rated, an MEI is not needed. But I am not 100% certain on that.
No, you can't.
FAR §61.31(f) states (emphasis mine):
(1) Except as provided in paragraph (f)(2) of this section, no person may act as pilot in command of a high-performance airplane (an airplane with an engine of more than 200 horsepower), unless the person has -
(i) Received and logged ground and flight training from an authorized instructor in a high-performance airplane, or in a full flight simulator or flight training device that is representative of a high-performance airplane, and has been found proficient in the operation and systems of the airplane; and
(ii) Received a one-time endorsement in the pilot's logbook from an authorized instructor who certifies the person is proficient to operate a high-performance airplane.
FAR §61.1(b) defines "authorized instructor" as (emphasis mine):
(i) A person who holds a ground instructor certificate issued under part 61 of this chapter and is in compliance with § 61.217, when conducting ground training in accordance with the privileges and limitations of his or her ground instructor certificate;
(ii) A person who holds a flight instructor certificate issued under part 61 of this chapter and is in compliance with § 61.197, when conducting ground training or flight training in accordance with the privileges and limitations of his or her flight instructor certificate; or
(iii) A person authorized by the Administrator to provide ground training or flight training under part 61, 121, 135, or 142 of this chapter when conducting ground training or flight training in accordance with that authority.
Because you're not an "authorized instructor" in a multi-engine airplane, you can't give the training required by §61.31(f)(1)(i), nor can you use a multi-engine airplane to "certify" another pilot's proficiency under §61.31(f)(1)(ii).
Your creative thinking seems reasonable on the surface, but the verbiage is pretty clear here, and the FAA and courts are known to interpret the regulations very conservatively. You could always ask the FSDO for an official interpretation (if you do, please come back and post the answer here for us!).
Until then, I suppose you'll need to find either an MEI or a single to fly in.
Negative. See §61.195(b)(1-2)
Except as provided in paragraph (c) of this section, a flight instructor may not conduct flight training in any aircraft unless the flight instructor:
(1) Holds a flight instructor certificate with the applicable category and class rating;
(2) Holds a pilot certificate with the applicable category and class rating; and
(3) Meets the requirements of paragraph (e) of this section, if applicable.
This includes logbook endorsements as well for particular aircraft category and class.
Now it is possible to give the other person a high-performance endorsement if the training is conducted in an aircraft category and class listed on your flight instructor certificate. As I understand it, there is no distinction between a high-performance, single engine airplane in a high performance, multi-engine airplane in re to training requirements to meet §61.31(f).
