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I have noticed that the A380 only uses the two engines closest to the fuselage to reverse thrust to brake. Are all four engines the same (i.e.: could they theoretically swap engine 1 and engine 2) or are the inside ones different from the outside ones?

In general, would the outside ones have reverse capabilities if they were installed on the inside or are they different types of engines?

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  • $\begingroup$ I don't believe that the outboard engines have thrust reversers installed, if that is what you are asking. Hopefully somebody has a reference for that. $\endgroup$ – Ron Beyer Aug 24 at 3:14
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    $\begingroup$ This question discusses the A380 outboard thrust reversers, or lack of. My understanding is that the thrust reversers are more properly considered part of the nacelle, and there is some integration required to link them to the engine systems. If someone knows better I'd be interested to know more. $\endgroup$ – CatchAsCatchCan Aug 24 at 7:11
  • $\begingroup$ Would the failure of one of a pair of outboard reverse thrusters cause a more severe turning force and compromise the landing safety? $\endgroup$ – Transistor Aug 24 at 12:25
  • $\begingroup$ @Transistor The reason for only inboard reversers that I've seen cited is that there's a higher risk of FOD ingestion when using the outboard reversers, given the A380s large wing span. But yes of course, physics alone dictates that the thrust differential has a greater "lever" if the engines are farther out from the body. $\endgroup$ – zymhan Aug 24 at 12:37
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The Airbus A380 comes with two engine choices:

The thrust reversers are not part of the core engines. The reversers are developed by the company which produces the engine nacelle, in this case Safran Nacelles. They developed nacelles for both engine variants for the A380, including the first electrically actuated reversers:

Safran Nacelles nacelle systems equip the Airbus A380 powered by four Rolls-Royce Trent 900 engines or four Engine Alliance GP7200 engines. [...] they are the first in the world to have a thrust reverser with an Electric Thrust Reverser Actuation System (ETRAS®).

(source: safran-nacelles.com)

A380 Nacelle
(image source: safran-group.com)

Are the nacelles interchangeable?

No, the nacelles for the outer engines are different from the inner ones to save weight. This article says:

Four nacelles were developed for the A380: one inboard nacelle (with a thrust reverser) and one outboard nacelle (without), for each of the type's two engines, the Rolls-Royce Trent 900 and Engine Alliance GP7200.

As ymb1 pointed out in the comments, this is confirmed by the type certificate for the Trent 900:

At engine certification, the engine has been approved for use with Aircelle Thrust Reverser Unit (TRU) at the inboard engine positions (part numbers ASE 0010-XX-0 for the left hand installation and ASE 0050-XX-0 for the right hand installation) and for a Fixed Fan Duct (FFD) in the outboard engine positions (part numbers ASE 5010-XX-0 for the left hand installation and ASE 5050-XX-0 for the right hand installation).
The TRU and FFD do not form part of the engine type design and must be certified as part of the aircraft type design.

and also for the GP7000:

This engine is approved for use with Airbus thrust reverser system P/Ns (left and right) L78DR130000xxx / L78DR230000xxx and with Airbus fixed fan duct P/Ns (left and right) L78DR140000xxx / L78DR240000xxx.

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  • $\begingroup$ Got it, thank you! My naive self was including the nacelles as part of the "engine" when I asked the question. $\endgroup$ – Sam Creamer Aug 24 at 17:27
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    $\begingroup$ It sounds from this answer like the actual answer to the question is yes, the engine cores can be moved from one nacelle to another if need be, since the type cert for the GP7000 says that it's approved for use with any of the 4 nacelles on the A380. Just the nacelles themselves couldn't be moved around (which they normally aren't anyway.) Am I reading that correctly from the answer? $\endgroup$ – reirab Aug 24 at 20:47
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    $\begingroup$ @reirab Yes, that would be my interpretation as well. But I don't know if there are any small differences (under the same type cert) that would make moving to a different position impossible (see also John K's answer). Anyway, it is not impossible to move engines because of the reversers. $\endgroup$ – Bianfable Aug 24 at 20:51
  • $\begingroup$ If your interpretation is the engines are interchangeable, then this should be mentioned in the answer, as for the moment it only states the nacelles aren't interchangeable, and therefore doesn't answer the question explicitely. $\endgroup$ – mins 5 hours ago
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Airlines normally maintain what are called Engine Build Units (EBUs) in their spare engine pool. The engine will be pre-assembled up to the point where variations in position on-wing have to be accounted for. Components beyond that point are only installed at the time the engine is installed on-wing.

Designers try to minimize engine "handing", mirror image configurations of things like plumbing, heat exchangers, etc, so the EBU can be built up to the most complete assembly possible, ready to be slapped on in a crisis.

On something like the 380, to the extent that reverser related components can be installed on the EBU, the airline will probably have a choice of:

  1. Leaving the reverser related components off the EBU, so a given EBU from the spare engine pool can be installed on any location on-wing. Cheaper from a spare engine pool perspective. Or:
  2. Maintaining 2 EBUs, one for inboard installations with reverser components installed and one for outboard installations, without reverser components. More expensive, but could be a significant time saver.

The choice will be based on a global cost business case.

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  • $\begingroup$ Good information! How much of the reverser is actually installed on the EBU, though, since the reverser is part of the nacelle, not the engine core? $\endgroup$ – reirab Aug 24 at 20:49
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    $\begingroup$ Hard to say without knowing the engine itself. There will certainly be control components of some sort related to the thrust reverser system; sensors, actuators etc. If the engine is non-FADEC (not in this case I know) there is often a some sort of actuator that snaps the throttle control to idle if the reverser deploys in flight. On a FADEC engine it's done by software. It could be though, that so much of the reverser system is independent of the engine itself that a single EBU is worth having for the entire fleet that there is not enough time saving during a installation build up. $\endgroup$ – John K Aug 24 at 21:07
  • $\begingroup$ The sensors are not really a commonality issue. All that is needed on the non-reverser nacelle and pylon is an interface to the FADEC which mimics the fact that the (non-existent) reverser is not deployed. It's worth pointing out that with FADEC the majority of the engine hardware (up to the level of complete engine modules) can be common even between different mark numbers of engine on different aircraft types. This is analogous to a common powerplant being "re-chipped" for different applications (with different tradeoffs between service life and performance) in the car industry. $\endgroup$ – alephzero Aug 25 at 0:34

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