Originally Posted by
groundbum
there's a theme running through a lot of the posts and media postings that I'd like to counteract. The theme is this was an unforseen situation or a unique failure point or something never seen before or a multitude of little issues adding up or a complex engineering/HF scenario etc.
IT'S NOT. It's a basic basic basic engineering flaw to build a system that controls a flight surface based on a single input. Boeing is proud to have years and years of engineering heritage so it knows full well the design was flawed and cheap even as soon as the first person said "we could get away with just 1 input". 100 other engineers would have immediately said no way not ever. But obviously somewhere a commercial person stepped hard enough on the Engineers to get the single input design commissioned. Everything else is just collateral damage. I can even understand though not like the decision to have a primary control surface move just to send feedback back to the stick, rather than add a servo to do the job. All the bits were there so it was too tempting to add some lines of code and voila!
G
It was more than tempting - it was just a little add on to the speed trim system in the eyes of B. The fact that the speed trim system itself has been accepted by all involved in 737 ops (I have to say I found it a strange bit of kit when training on the -300 quite late in career) makes the mod even more tempting.
Doesn’t make it right though - and doesn’t make the STS right either.
B have used this method on other aircraft too to achieve various aims (tanker trim for example) so it is a deep rooted solution in the company. It does however grab the aircraft by the balls and all you need then is a Speedy Gonzales coming along to misuse the situation.
I still think it would be worthwhile to replace this feature completely by a direct feel input for all the reasons outlined already - even if the delay/costs are awful - at the end you get an honest aeroplane to sell the customers.
PS for those who don’t know, having grabbed hold of the aforementioned Saturday night equipment Speedy Gonzales then says “May I trouble you for your wallet?”