10
$\begingroup$

As a follow up to why doesn't the A380 use outboard thrust reversers, if a component is not used in an engine, is it completely removed (hardware, wiring etc etc) or is it just made inoperative?

In the case of the A380 wouldn't it make it more difficult to maintain and handle 2 engines which are the same, but with different accessories installed?

Wouldn't it be risky as there might be human error factors whilst servicing or installing the thrust reversers?

$\endgroup$
12
$\begingroup$

Short answer

The reverser is not installed on the outer engines. As the linked question mentions: This allows to lighten the engines, this also prevents any unwanted and hazardous opening in flight as well as the costly check time for an unused feature.

The reverser used on the A380 is a cold flow type. It is merely part of the engine by itself. It is actually integrated in the nacelle structure channeling the bypass cold flow.


Principle

Thrust reversal on this aircraft type consists in opening the bypass duct sideways, interrupting the bypass flow in the duct and redirecting it through the opening. The opening is created by sliding the aft section of the nacelle case to expose a set of vanes. The blocked flow now escapes sideways and is guided forward by the vanes:

enter image description here
Principle of cold flow thrust reverser (source)

enter image description here
Thrust reverser on the A380 (source)

Engine, reverser, nacelle

The A380 is equipped with Trent 900 from Rolls-Royce or GP7200 from Engine Alliance. The thrust reversers are made by a different provider, Airbus-Aircelle (formerly Hurel-Hispano, now part of Safran), which also manufactures the nacelles. This is because the thrust reverser is really integrated in the nacelle rather than linked to the engine.

Trent 900

The reverser is in the cold / bypass flow behind the fan section which is the engine section with the largest diameter (in the Trent 900, about 3m!).

enter image description here
Hot flow, cold flow and reversed flow in a Trend 1000 (similar to 900).
Based on an excellent 3D model by Gandoza, on TurboSquid.

The cold flow duct is similar in both versions of the nacelles. The duct is fenced by two semi-annular walls, where the flow is rushed by the fan and the LP compressor.

The reverser features are just added or not at the end of the duct, just behind the fan frame.

enter image description here
Not the A380, but similar: Front panels can raise like petals and block the flow when the sleeve move aft (source)

Cold flow duct with reverser

The inner wall prevents all the flow to reach the core and the components and pipes around it, in order to not create damage or drag and heat. However a limited quantity of air is still directed toward the core for cooling.

enter image description here
Trent 900 duct and reverser.
Based on TurboSquid models.
Top image from the excellent 3D model by BlueGreen.
Bottom images from another excellent 3D model by BlueGreen.

Cold flow duct without reverser

Left half of the duct highlighted in blue.

enter image description here
Nacelle duct for cold flow. Based on image by Benny Zheng on Airliners.net

$\endgroup$
  • $\begingroup$ As I understand it, a large percentage of the thrust produced by this type of engine is from the cold air flow, but I'm not clear. In thrust reversal is the engine still producing forward thrust? $\endgroup$ – Howard Miller Apr 22 '16 at 3:19
  • 2
    $\begingroup$ @HowardMiller: You're correct for this type of engine with cold flow reverser. The net rearward thrust is about 40%. This ratio decreases with RPM. See this thread on PPRuNE. This article states an efficiency in the range 30-60%. Efficiency of buckets reverser is higher. $\endgroup$ – mins Apr 22 '16 at 6:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.