No, the DC-9, MD-80, MD-90, and B-717 all have a single nut but that single nut has two threads. ( A two start thread.). Jack screws with two independent nuts are typically arranged so the backup carries no load until the primary fails. In the two thread single nut design both nut threads wear together and they wear quickly if they are not lubricated.

Whilst we are going along the education route: mechanical seats have levers, bowden cables and pins into holes, all subject to wear and failure; electric motored seats, as far as I recall, all had a mechanical back up, not a B787 Engr, but from earlier posts of the mechanical selection cutting out the actuators suspect the same back-up.
2 switches? the button switch had a very positive feel, also pilots might select the directional switch and then blip the button switch, hence failure would be apparent; blip-ping the directional switch is much more subject of incorrect direction.
When I first worked on an American aircraft of BAE manufacture, I questioned the foot rests on the instrument panel; I was told used in cruise, I note not visible on the B787 panel, but I would still suspect Pilots sit at the rear most seat position during cruise, than hunched over the control column, perhaps some actual Pilots might comment?

They are fitted on some MD aircraft too. The logic seemed to be that pilots are going to put their feet there anyway so best to protect the displays. I don't think I ever saw a flight test pilot use them.

Cockpit Housekeeping & Pilot Ethics
 

I hate when "investigators" resort to "Human Factors"
to explain a "complex failure interaction".
But maybe sometimes there are such HF's.

We all recall the AA901 / 26June94 MD11 upset ntsb's id MIA94FA169
(co-pilot NOT seated in a "normal position",
with seat-aft, & legs-crossed heel-to-knee). Electric seat, visitor entered cockpit ... .
That's ONE red-flag for students of inflight upsets.

The other red-flag mentioned : Visitor-in-Cockpit (F/A).

Several pilots have mentioned PAX ethics (keep their seat-belt fastened)
Pilot-lessons : Cockpit Housekeeping
-- AA311 / 8Oct1947, DC-4, NC90432, Chuck Sisto upset,
taught us that cockpit occupants can unexpectedly interact with switches on the overhead panel (feathered engines).

Housekeeping, Pilot Ethics, "airmanship" from 2009

Gotcha - I recalled that the claim was a dual load path that turned out to be not truly dual allowing for them both to wear at the same time. It baffles me that a single nut with two starts counts as redundant. How far back does FAA blindness go?

And that is being adequately proven with the posts on here...

But they are far more in keeping with an APRuNe (Amateur Pilots Rumour Network)!!!

I am happy when I look at an airline booking and find that it is on a B787...

Or it could stand for Paxing Pedant Rumour Network, you know, for the people who post about the other posts without making any reasonable contribution with their post.

I can only speak for myself but I would feel negligent if I sat with the seat in the most aft position during cruise. I can also say that I can’t remember seeing my First Officers sitting with their seat right back either. I fly short haul though ( max five hour sector) so it may well be different with long haul pilots. My opinion is that the PF should be in a normal seating position at the least.

Your FOs probably take their cues from you. I certainly don't have my seat right back but it's easy enough to be in a comfortable position where you still have access to the flight controls and can put your feet up.

I had to design a cover because the equipment operator would relax by using an under the crew station connector shell as a foot rest. They were resting an ankle on the crossed leg and bracing their foot against the connector under the counter. The user kept complaining the cursor would just randomly move, but could not reproduce. We had engineers on fly-alongs so the operator would be on best behavior and posture. I don't know who finally understood what was happening.

The connector was on a force (rather than displacement) joystick. My company designed the electronics; the installation was managed by a subcontractor with "experience" in such installations and should not have left the cable or connector exposed to such footloose behavior.

I won't name the aircraft, but it was to make deliveries in close proximity regardless of the weather conditions.

How do you eat your scrumptious crew meal?

Ha ha yes good point! I do indeed slide my seat right back to eat my meal. I think the mechanic/engineer who stated was imagining prolonged periods that weren’t restricted to formal handovers for meals. I could be wrong though, it happened once before …..1997 I think.🤔

Our 737 classics had a little tab on the top outer edge of the FMC to stop that from occurring. It was a known problem, the 744’s did not.

This is a good example of why cockpit video cameras should be mandatory. Voice recorders and data recorders can pick up a lot of things but a video recorder would have this incident resolved very quickly.

I had access to, and used, cockpit video and one second frame rate stills as a flight test engineer. These recordings can be a critical component of a flight test data set.

You just have to convince revenue crews, and their unions, they should be fitted. Good luck with that.

The ironic part of the reluctance to accept cockpit video recorders is that the objections are being undermined by all the airline pilot u toobers and social media junkies who are recording their day at work. They are assuming that all those Go-Pros and selfies will not be made available to investigators if their approach to whatever holiday island goes pear shaped. I remember seeing a video from an engineer's phone who was sitting in the jump seat of an Air New Guinea 737 that landed short of the runway in a heavy shower. The video showed the Captains ND with the magenta line going to the runway but the wx radar overlay showing a big mass of red on the final stages of the approach. In the absence of any call outs by the PNF the CVR and FDR would not tell the investigators the full story of that approach. The video showed the investigators what the pilots saw. So there is already de-facto cockpit video recorder so the industry should just mandate it and put similar protocols around it similar to the CVR and FDR.

Sorry, but the 747 seat (and for that matter the 787 and probably any other aircraft as wel) also has manual adjustment. And to get in and out (especially when you are in a hurry) most pilots won’t bother with the electrical but use the manual levers instead. It’s much faster and convenient.
Electrical is used mostly for fine tuning and while you’re actually flying.

I believe the 2 buttons was an excellent idea, like everything else used to be at Boeing:) (but more expensive then a single button).

Yes, there are a lot of those 'junkies', but only a small percentage of the real world. (I don't even own a phone that can take videos and have very often been very wary of those wanting to video everything in sight in my flight-deck/cockpit.)

But the real problem with any cockpit video recorders would be who would have access to them. You hear far, far too many recordings/transcripts from CVRs being broadcast far too widely after an incident where those who don't have a clue (many on here, sadly!) focus on the irrelevant because it is 'sensational' rather then relevant. I know of one crew who cringed when they listened to the CVR together with the UK AAIB of the comments that they had been passing immediately before an incident (the AAIB brushed it aside saying "don't worry, we hear worse"!) but those (irrelevant) comments were NOT made available to the public simply because they were not relevant. But in far too many 'regimes', those comments are made available. I understand that many years ago the New Zealand government decided that the police and prosecuting authorities could have first access to CVRs after any incident. As a result New Zealand pilots went through a significant period of not talking on the flight deck and communicating with hand gestures. This very, very rapidly cause a reversal of that decision as the response was not safe, so the accident investigators now have first access to the CVRs and only release them if there is obvious criminal intent. Cockpit video recorders would be a step far, far too far unless there were absolutely cast iron guarantees over restrictions on their use and their availability to the the idiot public and the idiot media.

Well incidents like this one will only strengthen the hand of investigators who do want them. You don't think that CVRs and FDRs were once considered a step far, far too far?

The cockpit camera idea is a solution in search of a problem.