i hope i can give you a broad idea of the concept of black belt. as stated on here previously, a black belt can be a beginner up to what is considered master. example. itf tae kwon do. cho dan bo is a basic black belt. at this level, he has now learned the basics of the art. he is ready to start learning the art. a 4th dan is considered an international instructor. 5th dan and up are master instructors. that was the information given to me by my former 7th dan master instructor, jong moon lee of rockford il, in 1981.
as far as jkd goes, if you take a poll of general skills and abilities of black belts, you might get a broad range and find just where a jkd practitioner fits in according to that type of ranking system. i trained at a school in wpb fl in 1991 with the late edwin pagan. ed told me that an advanced student in his class had the skill level equivalent to a 2nd dan black belt in the typical martial arts class. that was his opinion based upon his level and his teaching of jkd, under richard bustillo.
another kung fu instructor i had in 1984 told me basically the same thing. advanced student was equivalent to 2nd dan. he based his idea on the fact that we trained and sparred with a nearby goju ryu karate school. our advanced students were at about the same level as their 2nd dan black belts. its not a scientific study or formulated upon any true criteria taken, but it might give you some idea.
i taught a martial arts class years ago in the mid eighties and my beginning student, after ten weeks of training with me, (who was a 12 year old girl), had sparred with her father, a student of a local karate master for six months, and she beat him. he took her out of my class stating that it was wrong to teach sparring so soon. he had not done any sparring in the six months he was in the karate class! i told him he should be thankful that his 12 year old daughter would less likely be raped after attending my classes....
belts arent usually given in jkd. they normally use beginner, intermediate, and advanced levels. then either apprentice or assistant instructor, then instructor. some jkd schools even go into intermediate and advanced instructor. personally, i dont like the entire belt system nowadays because it seems outdated. too many people cross training in other arts. my thoughts on this are simple. i believe this idea came from something i read by dan inosanto.
knowledge and learning are like a circle. you come into the circle of knowledge bringing your experience and own knowledge with you. you may come from a background of primarily kicking arts and need to learn close range and grappling arts to help complete your knowledge and round out your abilities. how can you take a black belt from another system and put them in with white belts who have no knowledge? or very limited knowledge...their knowledge of fighting my be pretty good, but they need to work on other areas.
for me, i have considered the idea of using the term, phase training. each phase has certain requirements and conditions. if you come in and know what is in phase two, you need to work on phase one. the only reason they are numbered is to give the instructor an idea of what the individual is learning or has learned. once you complete all the phases you move into the associate or apprentice instructor phase, where you get experience teaching. its something i have been kicking around for some time.
i just wanted to share some of my ideas with you all. i hope it helps in some way. thanks for reading.