I just passed my IREX today: once again, huge thanks to Bob and his team, for their excellent IREX book, their practice exams, and their patient and prompt help on these forums.

I'm convinced that one of the biggest contributers to my first-attempt pass was doing numerous practice exams; and I thought I'd offer a brief review of the ones I used, in case anyone else might find them helpful.

1. Bob Tait

If you don't already know, these are online exams, available here . Cost (at time of writing) is AU$77 for four exams (three un-timed, one timed), in CASA format; there is an option to purchase additional, randomly-generated exams. The Bob Tait exams are clearly the best of the bunch (no, I'm not being paid to say that), with an easy online interface, instant marking, and clear explanations for every answer. One can even 'flag' problem questions, either to go back to or for special attention post-marking. Questions appeared to be up-to-date without exception. Highly recommended.

2. PCE Practice Cyber Exams

Another online offering, available here . Cost is AU$99 for six exams, also strictly per CASA format and to to CASA time limit (3.5 hours each). The interface is fairly user-friendly, and there is an exhaustive practice tutorial at the start of each exam (easily skipped once you're used to it). Surprisingly for an online exam, many of the questions were badly out-of-date: pre-'Part 61' recency requirements, approach plates for navaids that no longer exist, and a version of VH-OZY that was replaced two years ago were just a few examples. On the plus side, by the time you've finished PCE's exam six-pack, you'll be all over ADF and VOR track-and-heading questions: there are dozens of them (and the answer is almost always 'a').

3. Ground Effect

These exams are available online here (I found them as a hard-copy book, but I suspect it may now be out-of-print - I cannot now find it on any of the usual online aviation shops). Pricing is a bit variable: they work on a system of 'credits' (AU$50 for 50 credits, or AU$90 for 100 credits); you can choose to have your practice exam simply marked, for 5 credits; marked with a KDR (identifies which answers you got wrong), for 10 credits; or marked, with KDR and explanations for each question, for 15 credits. The interface is fairly simple (very similar to that of PCE, though without the practice tutorials). There is a good range of questions; I found a few out-of-date ones in the print version (not surprisingly), but none in the online version. No answer explanations are offered in the hard-copy version, but the online answer explanations (if you shell out the extra credits for them) are extremely thorough; . Highly recommended.

4. Rob Avery / Avfacts

Unusually, this exam is offered in a hybrid format: questions are supplied as a book (AU$61 for four exams, available here , among others), and then answers are entered and marked online using a registration code unique to that book. Beware: I found the book in two different formats - one from Rob Avery, and one with a similar binding but different cover from Avfacts - both containing exactly the same questions. The questions are excellent - wide-ranging and imaginative: surprisingly, even in a 2016 edition I found barely a single out-of-date one. Unfortunately I had technical difficulties with the online marking, which would repeatedly and apparently randomly close my 'results' screen within seconds of displaying it, requiring me to repeatedly re-enter all 40 answers; I don't know whether this is a common problem to other users, or unique to me (I was running Firefox on a Mac). Amazingly, when I submitted an email to customer support, within 90 minutes Rob Avery himself got back to me (on a Sunday evening!) with a temporary work-around and a promise to escalate it to his I.T. section; though I heard nothing from them, and still had the same problem two weeks later. The answer explanations are a little skimpy; but this and the technical hitches aside, I still recommend the Rob Avery exams for their excellent question quality.

I'd really recommend doing all of the above; although some of them are better than others, the more practice you get under your belt, the better your chances for a first-time pass; and at around AU$15 per practice, I think they're all excellent value if they save you a re-sit.

I'll close with a passing mention of Ron Newman's Online Aviation Theory (OAT). This is not a mere practice exam, but rather an entire online course for the IREX. It's quite pricey, at AU$750 for a lifetime subscription. It runs on its own downloadable browser via laptop or tablet (or even smartphone), and Ron is obsessive about keeping his material up-to-date. There are practice questions at the end of each sub-section; and you can put together 50-question practice exams for each section of the IREX syllabus. The answer explanations are sometimes a bit cryptic (they consist basically of quotes from the online material, and sometimes seem to be mismatched). If you have money to spare and really like studying on the move, then you might find this worthwhile; for most of us, I suspect that good as it is, it's a bit too expensive.

I hope that's proved useful to somebody: to anyone sitting the IREX, Good Luck!