Originally, you just had to swap the engine. That was when it was "hours"...going from RR to GE (or the reverse) was the same amount of time as just swapping an RR or swapping a GE.
Later in the development they couldn't get all the interafaces to work out to where that was possible, so you now have to swap the strut in addition to the engine. It's the strut change that adds time. Changing struts isn't as bad as it might sound (it's roughly equivalent to swapping an engine but with less rigging) but it does extend the time.
The only likely scenario for a change of engine OEM is a leased aircraft moving from one airline to another. It does open an interesting negotiating avenue for airlines though...if an engine OEM ever *really* pisses off an airline on a 787, they can credibly threaten to switch to the other engine OEM. I'm sure the "incoming" OEM would move heaven and earth to make the engine swap as painless and rapid as possible.
tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 81
Reply 3, posted (3 years 10 months 3 days 3 hours ago) and read 6083 times:
Quoting 474218 (Reply 2):
An "engine swap" would require a Service Bulletin and AFM revision.
Not really. A service bulletin is an alteration to the type design. In the case of an engine swap, both configurations are already type certified. You do need swap instructions, but that could be in the AMM and a documentation change doesn't require a service bulletin.
That said, just for process commonality, I suspect they'd do it via service bulletin because that's what all the customers would be used to.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 4, posted (3 years 10 months 3 days 3 hours ago) and read 6069 times:
Quoting tdscanuck (Reply 3): Not really. A service bulletin is an alteration to the type design. In the case of an engine swap, both configurations are already type certified. You do need swap instructions, but that could be in the AMM and a documentation change doesn't require a service bulletin.
Just be cause something is certified it dosen't mean you can do it when every you want.
You are creating a different configuration and configuration changes require a service bulletin or a STC.
A service bulletin was required to replace the RB211-22B engines with RB211-524 engines on the L-1011.
okie From United States of America, joined Jul 2003, 3450 posts, RR: 3
Reply 5, posted (3 years 10 months 2 days 22 hours ago) and read 5940 times:
Quoting 474218 (Reply 4): A service bulletin was required to replace the RB211-22B engines with RB211-524 engines on the L-1011
I really do not know but I am assuming that the plane would come certificated in such a manner as to not require just a whole lot of regulatory hoops to jump through to swap between the two powerplants. This was one of the major selling points from the get go.
That being said with most frames leaving the assembly line with power by the hour these days it is going to be a considerable number of years before contracts on the powerplants are up for renewal. Short of some type of major malfunction causing the turbine to pitch out the discs sawing the plane into pieces or huge difference in fuel burn then I would suspect we are a decade away from swaps short of an operator going Tango Uniform.
tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 81
Reply 6, posted (3 years 10 months 2 days 21 hours ago) and read 5922 times:
Quoting 474218 (Reply 4): You are creating a different configuration and configuration changes require a service bulletin or a STC.
That's true when the new configuration isn't certified as part of the type design in effect at the time that particular airframe was certified...the service bulletin is the vehicle to convey certification to airframes built before the type design was changed (if there was a production cutover). If the configuration is already certified under the type design for that airframe, a service bulletin is not necessarily required (although may be offered none the less for convenience). For example, there are certain parts for which there are huge number of certified part numbers (the 737NG has several dozen certified thrust reversers, for example). Each one is a different configuration. But if the engineering drawings (and, for practical purposes, the IPC) have the right interchangeability notes, you can swap between configurations just by swapping the parts per AMM procedures; no service bulletin required.
Quoting 474218 (Reply 4): Just because something is certified it dosen't mean you can do it when every you want.
A service bulletin is not required to switch between two configurations that are both part of the certified design of a particular airframe (type design + aircraft cert). You do need appropriate instructions to maintain airworthiness while making the switch...this can come from a service letter, service bulletin, AMM, or any other recognized ICA document. The most common case of this is two-way interchangeable parts.
KELPkid From United States of America, joined Nov 2005, 6630 posts, RR: 3
Reply 9, posted (3 years 10 months 2 days 18 hours ago) and read 5862 times:
Quoting nomadd22 (Reply 7): Can you swap the engine and strut simultaneously? Or do you have to remove the engine before removing the strut?
As I recall, AA created their own maintenance prodecudure that did this (against the advice of McDonnell Douglas and GE), and crashed a DC-10 into a neighborhood in Chicago (AA Flight 191). A subtle difference was that American treated the pylon and engine as one unit, as it was easier to remove the pylon from the wing than it was to remove the engine from the pylon. They left the engine attached during the pylon removal and installation procedure (which both the airframer and engine manufacturer objected to). Of course, leaving the engine and pylon suspended overnight by a forklift with leaky hydraulics didn't do the works any good, either...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
broke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 10, posted (3 years 10 months 2 days 12 hours ago) and read 5710 times:
Another issue when going from an American powerplant to a British powerplant or vice versa; the powerplants rotate in the opposite directions. It doesn't sound like much but the torsional loads caused by the different direction of rotation do make a difference. I have worked both RR and PWA powered 757's and strut service problems occur on one side of the strut or the other depending on which engine is installed. For that reason, if the powerplants were swapped, the hours and cycles for each powerplant type would have to be tracked in addition to all the other normal tracked items. It dosen't sound like much but the more complexity that is put into a maintenance program, the more likely something will be missed.
In addition, when the 757 was first put into service, it came with the RB211-535C engine. Later 757's came with the -535E2 and the intent was to swap one engine for the other without any changes to the interface. That didn't turn out to be the case, the strut had to be modified in order to accommodate the newer powerplant. Generally, modified replacement struts were on hand when the powerplant swap occurred and the removed struts were then sent to the strut manufacturer to be modified for use on the following airframe.