Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 354; Flight Crew Type 5000
Training / Qualification
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Manuals; Human Factors; Aircraft
Upon completing my walkaround; I noticed there were FOUR vortilons on the left wing versus THREE on the right wing. Our manual (AOM) (Aircraft Operations Manual) states that there are three installed outboard of the engine. This was the second time in about six months that I noticed this on a walkaround. As I entered the jetway; I informed the Ops (Operations) Agent that there was a Maintenance discrepancy and that boarding should be stopped. Six months earlier; we ended up deplaning Passengers and Jumpseaters as the aircraft was taken out of service.I informed the Captain of the discrepancy and informed him of what had happened six months earlier.  Back then; I had 5 vortilons on one wing and three on the other. Although I never got any feedback of the outcome of that particular event; I suspected that a MAX slat had been installed on the NG (Next Generation). I suspected that because the next aircraft we were assigned to was a MAX and the slat in question looked identical to the one on the NG. For what it's worth; our MAX AOM is incorrect in that it states there are three vortilons per wing. There are actually 5. I submitted a report and received an email telling me the manuals would be updated. The MAX AOM is still wrong.Back to my NG in ZZZ. The Captain called Maintenance Control and was told the slats were interchangeable. I actually talked to the Controller as well and told him what happened a few months earlier. He informed me that Company had received guidance from Boeing and told me again that the parts were interchangeable. He mentioned that there was more than one aircraft flying around like that and that he got a call about it every day. I suggested that some sort of guidance should be shared with the pilot group; so that we were aware of the discrepancy between the books and the actual aircraft. I have ZERO written guidance in front of me. The only thing I have is the Maintenance Controller's word; yet for whatever reason it doesn't sit well with me.  I hope to receive feedback; and more importantly; I hope guidance is shared with the entire pilot group (at least update the manuals).
B737-800 flight crew reported the number of vortilons installed on the left wing was different than on the right wing and may be a 737-MAX slat.