Air Carrier Captain reported a turn back to the origin airport after EICAS displayed a message regarding the landing gear. Post flight it was found there was a switch in the E&E compartment not in the proper position.

Narrative

While this report may or may not be applicable to the report program; I decided to submit it as I feel there are valuable lessons learned that can affect safety of flight. The flight concerns a memo message that resulted in an Air Turn Back. On preflight we discovered a memo message - VMO GEAR DOWN on the EICAS. I asked my Relief Pilot to look up the message. He only found it located in the MEL manual. It states; it is a memo message and says 'Alternate gear down VMO' and MEL is NA. We double checked our switch selections to include alternate gear extend nose/ body switches. We found them in the normal position. We contacted Maintenance to come investigate. Two Mechanics looked at the message and appeared to attempt to troubleshoot. They left the cockpit; to what I thought was to contact Maintenance Control. Maintenance returned and stated it was good to go. They showed me their manual showing the memo message and it stated 'no maintenance action required.' I looked at the Mechanic and placed my thumbs up; he shook his head in the affirmative and returned the signal to me. I told them I would make a 'C' logbook entry. The Flight Crew discussed why the message was there; and believed the numerous database updates maintenance performed prior to the flight must have created an error.On climb out we noticed the red maximum speed indicator on the speed tape remained low as we accelerated (270 kts). We were heavy with a TOGW over 900;000 lbs. The FMS directed speed pointer was approaching the maximum speed indicator. I set speed intervene and rolled the commanded speed back. As we climbed the minimum maneuvering bar increased. For some reason auto flight VNAV was not holding the selected speed and it rolled towards the minimum maneuvering bar. There were no other indications. I deselected auto flight to manually pitch for speed in the climb. At some point I asked the Relief Pilot to look for an unannunciated checklist. We requested a level off at FL180 so we would not get to an altitude causing a stall or overspeed indication. Once level we selected auto flight again. This time it held the selected airspeed. I elected to remain the Pilot Flying and communicate with company. I tasked the FO (Flight Officer) and Relief Pilot to communicate with ATC; and trouble shoot the problem(s). I contacted Dispatch via SAT for a patch to Maintenance Control. We discussed our situation with Dispatch; Maintenance Control and a Engineer. We investigated if we had enough fuel to continue to destination at a low level. Both myself and Dispatch decided we did not. An ATB was decided; and we received an amended release. During this time it became increasing problematic communicating with ZZZ Control mostly due to language barriers. Eventually I [requested priority] enabling us to remain at FL 180 in holding to dump fuel over the water approximately 160 NM from ZZZ airport. I requested direct to the IAF (ZZZZZ) when we finished holding so we could calculate our fuel burn back to ZZZ. We began fuel jettison procedures per the QRH. Initially the left jettison nozzle failed to open. It opened shortly later. We began the fuel jettison checklist with the QRH vice the Electronic Checklist (ECL). I think this was due to holding the QRH from previously looking up unannounced checklists rather than using the ECL. We later received messages of low pump pressure on our FUEL OVRD pumps. The QRH says not to accomplish those checklists. The problem I believe is since we did not run the Fuel Jettison; ECL it did not inhibit those messages. We had a carrot to run those checklists which I believed we could not ignore. We addressed those checklists by addressing and inhibiting items to clear them from the primary EICAS. We then transitioned to the E Checklist for Fuel Jettison. During Fuel Jettison we received the FUEL TANK /ENG message. Per the checklist we did not address till after jettison complete. After jettison was complete we received a FUEL IMBALANCE message.We accomplished the checklist; and fuel management procedure after determining we had a longitudinal imbalance. After fuel jettison was complete we cancelled the [priority request] while returning to ZZZ. Despite previously requesting direct to ZZZZZ they attempted to route us direct to ZZZZZ1 for the arrival. We requested again and was given direct ZZZZZ. ATIS advertised [Runway] XXR for landing. We prepared and briefed for that approach. Approach then attempted to assign us [Runway] XXL; which is not in the terrain data base. We requested and were given XYL; briefing accordingly. We landed approximately 500 lbs. under maximum landing weight.We were on reduced rest due to prior flight mechanical delay. Crew Scheduling reduced our show time to one hour prior to departure rather than the standard 90 minutes. This combined with a late peak flight added production pressure to our timeline management. I felt my crew's performance was excellent and exceptional. We were tired; and both my FO (Flight Officer) and Relief Pilot caught/trapped many items. They used excellent forethought in advising me on potential outcomes. The memo message was due to a switch in the wrong position in the E&E compartment which we did not have access to in flight. The switch has a strange two position guard where the switch tip appears in either position. Lessons Learned. 1. I was not aware there was a switch in the E&E compartment that controls these functions. Perhaps I missed it; but at no time do I recall this switch being mentioned in any of my training. This switch is common on all these makes of aircraft. I have flown this manufacturer aircraft for over XX years. 2. Using the electronic find in such a situation. I learned a better way to search. Instead of searching a single document. Even though we felt time compressed this would not have taken long. Had I done this; I would have found a better explanation of the message in the Systems Manual. It states; 'Gear down dispatch has been selected in the electronics bay.' Had I done this; most likely I would have brought this to Maintenance attention. 3. As a Captain it is important to delegate and rely on others with more expertise to reach decisions. With that said; especially at international gateways I plan to question Maintenance more to fully understand why they are clearing us to go. In this situation; I will contact Maintenance Control myself to clarify the problem; and clearance. For this event we were under pressure for a timely departure; and I felt comfortable with direction from Maintenance. Next time that will not be the case. 4. With this particular switch selected; FMC fuel calculations will not be accurate with the gear up. While it was most likely impracticable to continue to destination at perhaps FL200; the quick calculations I made to see if it was possible were no doubt off. It showed me landing ZZZ1 with around 19;000 lb of fuel. It did not occur to me till later that was calculating the flight with gear down which the FMC thought we had but we did not. More importantly; calculating my fuel for return to ZZZ was off. Even though I added a little 'buffer' we found ourselves in the descent probably being overweight at landing. I elected to 'dirty up' ahead of schedule to make our Maximum Landing Weight. Recommendations. 1. I do not know how practical this is but I would like to see this message elevated to Advisory or Status level. The switch is only used to dispatch with the gear down. It seems that an elevated message level could be noted with an MEL or other log notation and procedure for the aircrew. At the very least I Recommend this memo message be addressed in the QRH with a do not takeoff without gear down dispatch - or something to that effect. 2. I know this is engineering level at the manufacturer; but that switch appears possibly to be ambiguous for Maintenance Personnel. The guarded switch has two positions; but each position has a hole in the guard for the top ofswitch. While it is placarded normal down; I wonder if a quick glance can be mistaken. Additionally; foreign Maintenance may not find it intuitive. Thank you for reviewing this report.