CAA SN–2019/005 is a direct response to the second B737 Max loss. It may be polite and encapsulated in vague discussion, but it is directly talking to the 737 trim system. Peripherally, it may remind some airbus operators of the implications of direct law and the need to remain in trim, but that is not the central theme.
"This is with particular reference to aircraft equipped with conventional trimming systems (i.e. non-fly-by-wire) and aircraft which use manual trim back-up systems in the event of an electronic trim system malfunction."
Until MCAS came along as a surprise in the MAX, the latent issues of the B737 trim system had been lost in the mists of time.
While giving warm fuzzies for effort, I rmain befuddled by the following comment:
"Utilising their Safety Management System (SMS)...". The industry had two exceptional events occur, which are the subject of major mishap investigations. Two airlines have SMS that would have applicable information in that area, the other 200+ IATA airlines and sundry other operators around the world, in 121, 125, 135 and 91 type ops would be wondering what they are referring to. As it is a UK CAA document, then presumably it is targeting the SMS programs of the handful of 737 operators that have the aircraft on their AOC's and which have not had events of note for the subject matter. Arguably the FCF manual reversion events from about a decade ago may at a pinch be considered to be the SMS items of note, however, that is not technically correct, the events in the manual reversion arise from an elevator position difference between power on and manual reverted conditions, which may indeed have led to an out of trim problem touching on the limitations of manual trim, but they didn't in the cases that occurred, so the SMS reference is, well, odd.
. . . .
Out of all of those parts, how that fits into the SN suggestion to use the SMS... is lost on this observer. Possibly it is an urging of the airlines to become expert in the latent deficiencies of the aircraft they operate, to second guess the regulator and the certifying authority, but I doubt that is something that the airlines want to or should be doing. The fundamental problem with say Ch.5 and 6 which are the meat and potatoes (er, Yorkshire pud and gravy for Brexiteers) is that data doesn't exist to work with for the operators, unless they did have the problem on the Max. If they had, we would have heard about it in the Mirror, or other rag, or at least on PPrune. In the absence of data, how does a reactive linear/quasi linear system function to promote safety?
fdr;
Interestingly, having gone to the CAA SN after
Turb's comments but prior to reading your post, your comments reflect precisely the way the SN struck me as well. What do we do that isn't already being done, and on what basis?
For example, I was thinking about how both our SMS and FDM/FOQA Programs could best be employed to advance the thinking and implied plan of response in the SN.
But for this to occur, there would already have to be events in the reporting system or in the flight data and, hopefully, a plan already in place. I like the emphasis on manual flight, SA, etc., but AF447 was our lesson for that important and still-necessary aspect of training.
Since the inception of our FDM Program we have monitored the operation for LOC Events, including stabilizer trim position-and-movement in phases of flight in which changes might occur which increase risk., (e.g., trimming into the level-off during a go-around).
While FDM Events may be captured and crews contacted in standard (typically western) ways for further info (and not for punishment), the SN appears to emphasize what we already know should be done.
The emphasis is correct. I'm looking foward to seeing how airlines come to terms with the SN especially if they're already "tuned-in".
The cynic in me says that airline managers are going to do the math, play the odds, and hope the next hull loss doesn’t happen on their watch.
Tomaski, for those that may not have heard the term before, that approach by those who don't understand how safety work is done, is known as "tombstone safety".
PJ2