If you are a current CFI, you may train sport pilot candidates, within the category/class listed on your CFI certificate. Obviously, you will need to become familiar with the sport pilot rules under 61 subpart J. The SPORT PILOT & CFI APPLICANT CHECKRIDE book will fill you in on everything you need to know.
You may wonder, “If a sport pilot wants me to conduct a flight review (BFR), can I do it?” Yes, there is no difference in the endorsement an instructor would give for a flight review for sport pilot. See §61.56. A medical certificate is not a requirement for completion of a flight review.
If they are a private pilot operating as a sport pilot, the flight review can be done in any aircraft for which they are rated. If they are “only” sport pilot, it will have to be conducted in an aircraft that meets the definition of a light-sport aircraft.
You will give a standard flight review endorsement, as spelled out in FAA advisory circular AC 61-65E, appendix 1, item 55, as follows:
“I certify that (First name, MI, Last name), (pilot certificate), (certificate number), has satisfactorily completed a flight review of § 61.56(a) on (date).”
Example: S/S [date] John Smith 457887934 CFI Exp. 01-31-10
What do you do if you are a current CFI and would like to instruct within the privileges and limitations of a sport pilot certified flight instructor (CFIS) under subpart K, so that you can use your drivers license in lieu of a third class medical? Assuming your most recent medical application was not withdrawn, denied, or revoked, you don’t have to do anything different. See §61.429 which specifically addresses this situation.
Here is a unique situation where a subpart H (private) flight instructor (CFI) has a current flight instructor certificate but let his 3rd class medical expire. He/she can instruct a student private pilot in a light sport aircraft without a medical and the time counts towards a sport pilot and private pilot because he/she is pilot in command (PIC). All hours count towards a sport and private certificate (except night) because the CFI has a valid Subpart H flight instructor certificate and is PIC of the LSA. He/she cannot fly or provide instruction in a non LSA, at night in any aircraft or in IFR conditions in any aircraft because he cannot be pilot in command.
The CFI with expired medical and a CFIS can give instrument training in a LSA required by 61.93 (e)(12) before a student cross country if it has the required equipment as long as they are in day VMC. No attitude display is required for this and a partial panel (compass, airspeed, altitude) is adequate.