In commercial aircraft like Airbus or Boeing, there are several control surfaces that work in the same function such as for roll control capability, the control surfaces are aileron and spoiler. Also just like (Correct me if i'm wrong) HSTAB trim as backup of elevator. Because of course it is used for redundancy hence there are no single failure lead to catastrophic. But i read that predator and reaper do not have spoiler. So how the configuration of predator/reaper control surface to accommodate "no single failure lead to catastrophic" in term of control surface failure

Thank you

  • $\begingroup$ Why would they need redundancy? It's not like it's going to kill hundreds of passengers if it crashes. $\endgroup$ Commented Mar 11, 2020 at 7:06
  • $\begingroup$ @JörgWMittag Okay, but according to CS 23 Special Condition rev 3 link related to RPAS, still, if the RPAS fly into civilian airspace and crash due to erroneous of roll control resulting one or more fatalities, it is still considered Catastrophic. But even below it, which is hazardous, the case is loss of RPAS control capability, which i think the accommodate hazardous type function, redundancy is still required. $\endgroup$
    – Zahi Azmi
    Commented Mar 11, 2020 at 7:17
  • $\begingroup$ Why would this be relevant? Has General Atomics applied for a civilian European Type Certificate? I can't even imagine what a civilian use of a. Reaper would be. $\endgroup$ Commented Mar 11, 2020 at 8:25
  • $\begingroup$ There is redundancy. And, then there are work arounds. The examples that you gave sound more like work arounds. They are systems meant for another purpose that can be utilized as a last resort. For instance, trim tabs are not meant as backups to primary control surfaces. They can be used as such in a pinch. But, that is not their primary function. Saying that, many small aircraft do not have trim tabs on every control surface. Nor, do they have spoilers. Safe flight is still accomplished. Military drones are not large aircraft compared to Airbus and Boeing aircraft. $\endgroup$
    – Dean F.
    Commented Mar 11, 2020 at 9:42
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    $\begingroup$ You may note that redundancy is also provided by several control surfaces moved by different hydraulic circuit (e.g. multiple spoilers, each pair being connected to different hydraulic circuit) $\endgroup$
    – Manu H
    Commented Mar 11, 2020 at 10:56


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