I know that the 737NG is not fly-by-wire, but are the control surfaces controlled with hydraulic systems that transfer the input from the pilot to the control surfaces via fluid (hydraulics), or is the pilots' input transferred to the control surfaces' electronic actuators via electric signals?


Of course it's hydraulic.

Electric actuators or power-by-wire is actually a far more exotic technology than fly-by-wire, and the latter is a hard prerequisite for the former.

Normal fly-by-wire is still based on hydraulic systems, with the electrical FBW system controlling the valves. And even in power-by-wire systems, the final actuator is typically a small enclosed hydraulic unit.

The newer 737 MAX has a couple FBW elements (spoilers), but is still a manual system, well short of FBW or PBW.

  • $\begingroup$ Mhmmm, how bout on the max? And does that mean that the 737 is less reliable than the a320? Or is it safer as a human is operqting the controls? $\endgroup$ – lpydawa Aug 11 '18 at 6:54
  • $\begingroup$ By max I meant the 737MAX $\endgroup$ – lpydawa Aug 11 '18 at 7:14
  • $\begingroup$ Reliability is a complex subject, and safety a further separate one. Statistically speaking, the A320 has a better record. What can be said for sure is the A320 is a much more modern design - the 737 is itself based on the 707. $\endgroup$ – Therac Aug 11 '18 at 7:43
  • $\begingroup$ Yes, true, but why is the 737 still so popular? Its the A320 is so good in every aspect, then why does Ryanair use them? $\endgroup$ – lpydawa Aug 11 '18 at 7:58
  • 1
    $\begingroup$ The economics. The 737 is simpler and lighter, coming out to a slightly lower CASM. But it's got a tighter cabin and can't carry ULD boxes. The two have been close in sales, with A320 edging out ahead lately. You'll have to read a lot of industry publications to get an idea of what the competition is about. The short version is of course money. $\endgroup$ – Therac Aug 11 '18 at 10:29

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