A useful debate is now being conducted over current and future manpower needs of the metropolitan police force {editorial, Feb. 20}. Much of the discussion, however, is centered on numbers and not on the quality of new applicants and the success of recruits.

The basic requirements needed to apply to become a D.C. police officer include being between 18 and 30 years old and having a high school diploma and a minimum degree of physical fitness. As a successful applicant several years ago, I know that any further screening is so lax as to be practically nonexistent. There is an especially severe lack of meaningful psychological screening.

The results are both predictable and disconcerting, and add to the manpower crunch, for each year there is an unacceptably high attrition of young recruits and officers from the force. The attrition is due to many factors, including career changes, injuries and even criminal behavior.

One way in which this attrition could be reduced, and the overall quality of the force improved, would be to open up the application process to persons over the age of 30, as neighboring jurisdictions have done. These applicants would bring in many cases a greater degree of maturity, further life experience and more extensive work history on which to be evaluated during the application proc-ess -- and later in functioning as an officer on the street.

Quite frankly, if I needed to dial 911, I'd rather have someone who was 35 years old responding to my call than someone who was 18. LOUIS B. MEYERS Washington