# passenger jet electrical power generation **URL:** \ **Category:** Factual Questions\ **Created:** [August 7, 2017, 1:00pm UTC](https://boards.straightdope.com/t/passenger-jet-electrical-power-generation/792993 "2017-08-07T13:00:40Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![JHBoom](https://avatars.discourse-cdn.com/v4/letter/j/13edae/32.png) [@JHBoom](https://boards.straightdope.com/u/JHBoom)\ **Post date:** [August 11, 2017, 10:25pm UTC](https://boards.straightdope.com/t/passenger-jet-electrical-power-generation/792993/21 "2017-08-11T22:25:38Z")
> [@Hari\_Seldon](#): > > When you have a 110 socket on a passenger airplane, is it 60Hz or 400? 60Hz. Or 230V 50Hz, depending on who owns the aircraft. The S-92 helicopters I work on here in the M.E. have 230V 50Hz sockets in the cabin for passenger use. Passenger seat outlets, IFE (In Flight Entertainment) systems, and other non-essential cabin loads are powered by their own power supplies, separate from the power supplies for avionics and other, more critical aircraft systems. Those things are also among the first to be “load shed” in the event of an electrical system failure. The S-92 automatically load sheds all cabin power except the emergency lighting in the event of a single main generator failure. Cabin power will not come back on unless/until the pilot starts the APU. ---
**Author:** ![JHBoom](https://avatars.discourse-cdn.com/v4/letter/j/13edae/32.png) [@JHBoom](https://boards.straightdope.com/u/JHBoom)\ **Post date:** [August 11, 2017, 10:33pm UTC](https://boards.straightdope.com/t/passenger-jet-electrical-power-generation/792993/22 "2017-08-11T22:33:32Z")
Missed the edit window: > [@Rocketeer](#): > > The 757 and 767, if used for EROPS, have a hydraulic motor generator (HMG) which uses a hydraulic motor to generate about 10KVA of electricity in the case of both engine-driven generators dying. The generators, at the time of 757/767 EROPS certification, were not considered reliable enough that the probability of losing both on a long overwater flight was less than 10E-9. So the HMG was added to provide a backup electrical power source. > > By the time the 737 was certified for EROPS operation, generator reliability had improved and the FAA’s understanding had evolved, and an HMG was not required. Interesting; I’ve only ever heard/seen it called ETOPS. Had to use The Google to find out what EROPS is. Which leads to the usual style of aircraft mechanic humor… “What does ETOPS stand for? _Engines Turn Or Passengers Swim!_” ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 12, 2017, 12:26am UTC](https://boards.straightdope.com/t/passenger-jet-electrical-power-generation/792993/23 "2017-08-12T00:26:22Z")
They changed it to EROPS a few years ago when they began to apply similar regulatory logic about divert planning to non-twins. So now it’s “Extended Range Operations”. Or equivalently: “Engines Run Or Passengers …” The recognition moment was that engine problems were no longer the main cause of mid-ocean diversions. Instead it was other systems or passenger medical or violence issues. Problems that 3- and 4-engine aircraft are just as prone to. So now everybody regardless of engine count has dedicated contingency plans for Artic or mid-Pacific diverts, max time to landing, etc. Some of the details are still more stringent for some twins under some regimes. But everybody has some restrictions. [Previous page](https://boards.straightdope.com/t/passenger-jet-electrical-power-generation/792993.md?page=1)