#10 ( Re-confirmed this answer with AFS-810 the week of 02-28-2011, updated 12-27-2011 ):  I've only instructed in centerline thrust multiengine aircraft for the military (F-15, T-38, T-37, F-14, F-18, A-10, etc).  Will they give me Airplane Multiengine on my new Flight Instructor Certificate, and if so will it be restricted to centerline thrust aircraft?  No, they won't give you Airplane Multiengine on your new Flight Instructor certificate.  They also won't give you Airplane Single Engine because a centerline thrust airplane is still a multiengine airplane, not single engine.  But they will give you an Instrument airplane rating on your flight instructor certificate. 

Along with the Flight Instructor Instrument Airplane rating, the FAA has been issuing multiengine instructor certificates with centerline thrust restrictions to military IPs who've only ever instructed in centerline thrust aircraft (see the bottom of this page for the FAA list of centerline thrust aircraft).  However, they have now re-interpreted their position on this.  It is now their position, in short, that since the Practical Test Standard for Certified Flight Instructor Airplane never recognized the issuance of a centerline thrust restriction for multiengine Flight Instructors, there is no basis upon which to issue a centerline thrust restriction for multiengine airplanes to a military instructor applying for a Flight Instructor certificate based on military competency.  Therefore, they will not issue "Airplane Multiengine" on a flight instructor certificate to a military IP who only instructed in centerline thrust airplanes.  Click here for a copy of the June 10th FAA memo on this subject.  They also won't issue "Airplane Single Engine" to a centerline thrust multiengine only IP because a centerline thrust multiengine airplane is still multiengine, not single engine.

The good news is that Military Competency to Flight Instructor is still a great deal, even if the only rating you get on your Flight Instructor certificate is Instrument Airplane.  After all , the removal of the centerline thrust restriction to multiengine would have required a checkride anyway, and would have been otherwise useless by itself because there's no serious training being done in the U.S. in centerline thrust multiengine airplanes.  But more importantly, the golden part of this regulatory change to allow military competency to a Flight Instructor certificate has always been that it allows military IPs to "clep" out of the dreaded Initial Instructor checkride that has to be done with an FAA Inspector (not a designated examiner), has a 6+ hour ground eval, a 2+ hour checkride, and has a 66% initial failure rate. By getting any Flight Instructor certificate (including Instrument Airplane) for just doing a short written test, a person "cleps" out of the Initial Instructor checkride... and therefore every rating  after that which a person wants to add to their Flight Instructor certificate is accomplished thru a simple add-checkride instead (flown with a designated examiner, shorter ground eval, shorter checkride, etc).  So in short, you're still getting a CFII certificate to put on your resume, you're still clepping out of the Initial Instructor checkride, and you will still have to fly checkrides for anything else you want to add to the certificate.  All things considered, it's still a very good deal.

Once you have your flight instructor certificate with an Instrument Airplane rating on it, you can add airplane single engine or airplane multiengine in one of two ways: 1) if you get IP qualified in another military aircraft that is multiengine, non-centerline thrust or if you get IP qualified in a single engine airplane, you can add those ratings by just taking in your qualification paperwork (form 8, NATOPS form, etc).  2) you can take the FIA test (Flight Instructor Airplane) and fly an add-checkride with a designated examiner.

If you have already done your MCI test, turned in the paperwork, and been issued a Flight Instructor certificate that had an "Airplane Multiengine limited to centerline thrust" rating on the back of it, you can expect the FAA to remove the "Airplane Multiengine limited to centerline thrust" part completely when you renew your certificate at the 2-year point, unless you get the centerline thrust restriction removed before then (see below for more information on the short list of maneuvers that are required to be flown on the checkride to remove the centerline thrust restriction).

This new interpretation for centerline thrust does not in any way affect helicopter IPs, it does not affect people who were IPs in single engine airplanes, and it does not affect IPs who taught in non-centerline thrust aircraft.  It only affects the issuance of Airplane Multiengine on the flight instructor certificate of someone whose only multiengine IP time in the military was in a centerline thrust aircraft.