Bob, What is powered by the RAT depends upon the aircraft. Some power both hydraulics and electrical systems. Others just power hydraulics, usually (always?) with a hydraulic motor driving an electrical generator.
In the 737, I recall reading that the FDR and CVR are not considered to be essential systems and thus are not powered by the RAT. I can see both pro and con arguments for that but it would explain the loss of data in the Jeju case. -- Karl > On Jun 17, 2025, at 12:26 PM, Robert Ditchey via Mifnet > <mifnet@lists.mifnet.com> wrote: > > This question is directed to Mike Borfitz and the Mifnet pilots for possible > response, which I seek. > > There have been a few discussions about the RAT and the Air India crash. But > this e-mail pertains also to the Muan/Jegu Air crash in Korea and to the > “Miracle on the Hudson” crash of “Capt. Sullie.” > > It is my understanding that all of the aircraft involved in these accidents > have flight controls (ailerons, etc.) that rely upon hydraulic actuators to > move and position the flight controls, whether or not they are “fly by wire.” > In turn, the actuators depend upon electricity to function, and the > hydraulic system is powered (I think) by electric hydraulic pumps, not engine > driven pumps. That is also important when we consider that in the Sullie > case and in the Jeju case, bird ingestion caused the engines to fail (both.) > > So, in these cases, I am of the belief that the RAT deployed immediately when > the engines failed. And I also believe that the RAT permitted the electric > and hydraulic systems to continue to function, allowing the flight controls > to continue to function. (Obviously, with Sullie and Jeju, the flight > controls functioned up until impact, with both engines out.) > > But with the Jeju case, both the CVR and FDR failed before the crash. I > would guess that both the CVR and FDR are connected to the battery bus. Or > else the RAT could have or should have powered the recorders. Why did the > flight controls continue to function but not the recorders? > > I ask for some explanations from our esteemed group. If not, please send me > a good link. > > Bob Ditchey > -------------------------------------------------------------------------- > Revised: 20250507 > > You are receiving The Mifnet because you requested to join this list. > > The Mifnet is largely a labor of love, however the infrastructure isn't > exactly cost-free. If you'd care to make a small contribution to the effort, > please know that it would be greatly appreciated: > https://wardell.us/url/mifbit <https://wardell.us/url/mifbit> > > All posts sent to the list should abide by these policies: > > 1) List members acknowledge that participation in Mifnet is a privilege--not > a right. > 2) Posts are always off the record, absent specific permission from the > author. > 3) The tone of discussions is collegial. > 4) Posts are expected to be in reasonably good taste. > 5) We discuss ideas and not personalities, and we don't speak ill of other > Mifnet members. > > * The Mifnet WEB SITE is: > https://www.mifnet.com/ <https://www.mifnet.com/> > > * To UNSUBSCRIBE from this list at any time please visit: > https://lists.mifnet.com/ <https://lists.mifnet.com/> > OR: SEND THIS MESSAGE via email: mifnet-requ...@lists.mifnet.com > <mailto:mifnet-requ...@lists.mifnet.com>?subject=leave > > * Send Mifnet mailing list POSTS/SUBMISSIONS to: > mifnet@lists.mifnet.com <mailto:mifnet@lists.mifnet.com> > > * You may reach the person managing The Mifnet at: > mifnet-ow...@lists.mifnet.com <mailto:mifnet-ow...@lists.mifnet.com> > > * Please consider the DIGEST version of The Mifnet, which consolidates all > list traffic into 1-3 > messages daily. See instructions at: > https://lists.mifnet.com/ <https://lists.mifnet.com/> > > * Manage your personal Mifnet SUBSCRIPTION at: > https://lists.mifnet.com/ <https://lists.mifnet.com/> > > * For a list of all available Mifnet commands, SEND THIS MESSAGE via email: > mifnet-requ...@lists.mifnet.com > <mailto:mifnet-requ...@lists.mifnet.com>?subject=help > > * View The Mifnet LIST POLICIES and PRIVACY POLICY at: > https://mifnet.com/index.php/policies <https://mifnet.com/index.php/policies> > > * View instructions for Mifnet DELIVERY PROBLEMS at: > https://mifnet.com/index.php/delivery-problems > <https://mifnet.com/index.php/delivery-problems> > > * View The Mifnet LIST ARCHIVE at: > https://lists.mifnet.com/hyperkitty/list/mifnet@lists.mifnet.com/ > <https://lists.mifnet.com/hyperkitty/list/mifnet@lists.mifnet.com/>
-------------------------------------------------------------------------- Revised: 20250507 You are receiving The Mifnet because you requested to join this list. The Mifnet is largely a labor of love, however the infrastructure isn't exactly cost-free. If you'd care to make a small contribution to the effort, please know that it would be greatly appreciated: https://wardell.us/url/mifbit All posts sent to the list should abide by these policies: 1) List members acknowledge that participation in Mifnet is a privilege--not a right. 2) Posts are always off the record, absent specific permission from the author. 3) The tone of discussions is collegial. 4) Posts are expected to be in reasonably good taste. 5) We discuss ideas and not personalities, and we don't speak ill of other Mifnet members. * The Mifnet WEB SITE is: https://www.mifnet.com/ * To UNSUBSCRIBE from this list at any time please visit: https://lists.mifnet.com/ OR: SEND THIS MESSAGE via email: mifnet-requ...@lists.mifnet.com?subject=leave * Send Mifnet mailing list POSTS/SUBMISSIONS to: mifnet@lists.mifnet.com * You may reach the person managing The Mifnet at: mifnet-ow...@lists.mifnet.com * Please consider the DIGEST version of The Mifnet, which consolidates all list traffic into 1-3 messages daily. See instructions at: https://lists.mifnet.com/ * Manage your personal Mifnet SUBSCRIPTION at: https://lists.mifnet.com/ * For a list of all available Mifnet commands, SEND THIS MESSAGE via email: mifnet-requ...@lists.mifnet.com?subject=help * View The Mifnet LIST POLICIES and PRIVACY POLICY at: https://mifnet.com/index.php/policies * View instructions for Mifnet DELIVERY PROBLEMS at: https://mifnet.com/index.php/delivery-problems * View The Mifnet LIST ARCHIVE at: https://lists.mifnet.com/hyperkitty/list/mifnet@lists.mifnet.com/
