Hi there,
I have recently taken my RAF PTI specialist interview and can confirm that it is highly competitive and very tough. You are judged based on a scoring system from 1-4. For each part of the spec interview so the bleep test, Sapca etc. you will be either branded as 1/2/3/4: 1 being bad, 3 being a pass, 4 being a good pass. In total I scored a 3.0 which was high enough to be deemed suitable however due to the competitive nature I narrowly missed out on being accepted. I am re-doing my spec. interview tommorow so hope to get a higher pass to gaurantee acceptance.
In regards to the interview, you will do it before all the other tests so its a really good opportunity to impress the examiners before starting the tests which will help you in their judgements of you. To be fully prepared for the interview you must have really good knowledge of the career path of the RAF PTI, so the 12 sections of 28 weeks specialist training etc., make sure you highlight all of your achievements especially sporting wise and be able to demonstrate examples of leadership and responsibility (the more you have in the locker the better). It is also important that you are confident in the reasons why you specifically want to be a PTI in the RAF (a good point to make is that in the RAF you are treated with more respect than army etc.). This interview will be marked by the scoring system so if you score highly it gets you off to a great start and compensates for your weaknessess in other areas.
The other tests are marked the same way, so achieving 13.2 or more will score you a band 3 which is a pass, but don't worry necessarily if you score less than that as its not a pass/fail element unlike the swimming, one lad in my interview scored 12.6 on the bleep test but was still guaranteed a job. When you do the press ups and sit ups, you should be aiming for +50 press ups in a minute and +60 sit ups in a minute for a decent score (if i had of managed 3 more press ups and 2 more sit ups I would have scored 13.2 overall which would have guaranteed me a job!!!). Don't underestimate the sporting transfer ability examination either, at the time it seems slightly more laid back and enjoyable and its not absolutely crucial but they will be watching you the entire time so make sure you concentrate on getting your techniques right. When you lead your warm up you will be given the night before to plan it and its aimed to last 7 minutes (but in reality lasts a lot less than that), make sure when you deliver it use confidence and try to come up with some original ideas. The officiating element is fairly straightforward but again the examiners will always be watching so be confident and authoritative.
The swimming assessment takes place the next day and is important to get right I only scored a 2 on the swimming which cost me dearly. It's a very quick assessmentt so you have little time to settle in the pool so make sure your training has fully prepared you for it. I can tell you from my own experience that the swimming separates the decent from the very good candidates, but once you get it out the way its a whole lot of weight taken off your shoulders. In your 5 minute tal you will be expected to talk about personal life so hometown, family, jobs, holidays etc. but the main concxern of the examiners here is to monitor how you talk and deliver a speech in front of people, keep it interesting and add a bit of humour if you can. Finally the SAPCA is all about how much effort your willing to put in, its your last examination of the interview so ensure you put 100% into it! Its very challenging and very fatiguing but if you put in maximum effort then the examiners will admire that.
After all this is compete you will be invited into the office one by one as they tell you how you got on and what you scored in total. They will tell you where you excelled but more importantly areas to improve. If you don't pass its likely they'll invite you back again in either 6 months or 12 months. If you do pass however your position isnt guaranteed unless you score 3.2 or above then its very likely. They will contact you a few weeks later to let you know if you have been awarded the job!
I hope this has helped as when i first did my interview I was looking for information to help me out but there didn't seem to be much out there, so i went into great detail here. In regards to the age thing it doesnt really matter when i did my interview ages ranged from 17-26 and they were purely judged on their scores. However the older you are obviously you will have more experience but obviously younger candidates are easier to mould into what they're looking for but don't worry to much about that as theyll mainly judge you on your perfomances on the tests and your ability and suitability to be a PTI in the royal airforce.