Uncontained engine failure
Uncontained engine failure
Join Date: Jul 2001
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In the event of a failure such as a fan blade letting go, you would not want bits of the blade hitting the fuselage, so the idea is to try to contain the debris within the engine. The LP compressor casing in some makes of engine has a circumferential wrapping of Kevlar to absorb the impact and help contain the bits.
If it fails to do so, you have an uncontained failure.
If it fails to do so, you have an uncontained failure.
The word "uncontained" can be a bit misleading. The (thankfully!!) few big, bad nasty engine failures I've been involved in let lots of nuts and bolts go out the tailpipe. Because said scrap iron did not exit sideways through the engine casing, the failures were "contained" even though a fair mass was missing after landing.
A defined "uncontained" engine failure blasts bits out the side of the engine through the casing. This is obviously bad as the bits can enter another engine and turn a bad day into a nightmare.
A defined "uncontained" engine failure blasts bits out the side of the engine through the casing. This is obviously bad as the bits can enter another engine and turn a bad day into a nightmare.
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It may not generally be known but the armour plating is designed to " contain" the N1 or Fan section of the engine in the event of Foreign Object Damage resulting in break up of the Fan blades.
I am personally not aware of any engine which is currently designed to contain the N2 or high compression stages of the engine if they should subsequently break up.
Food for thought.
I am personally not aware of any engine which is currently designed to contain the N2 or high compression stages of the engine if they should subsequently break up.
Food for thought.
Join Date: Aug 2001
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>It may not generally be known but the armour plating is designed to " contain" the N1 or Fan section of the engine in the event of Foreign Object Damage resulting in break up of the Fan blades.
I am personally not aware of any engine which is currently designed to contain the N2 or high compression stages of the engine if they should subsequently break up.
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The requirement is to ensure that the outcome of a single blade release (from any cause) does not burst (become uncontained) the engine casing, no mater what stage (fan, compressor or turbine). There is no requirement, nor am I aware of any claims, to contain anything other than blades (like rotor disks).
History has shown that debris still exits the engine by going forward (through aircraft inlet cowls) or aft out of the tailpipe.
I am personally not aware of any engine which is currently designed to contain the N2 or high compression stages of the engine if they should subsequently break up.
<
The requirement is to ensure that the outcome of a single blade release (from any cause) does not burst (become uncontained) the engine casing, no mater what stage (fan, compressor or turbine). There is no requirement, nor am I aware of any claims, to contain anything other than blades (like rotor disks).
History has shown that debris still exits the engine by going forward (through aircraft inlet cowls) or aft out of the tailpipe.
Lomapaseo,
I think the reason that only the fan cases are armoured is that the energy released by a liberated N2 blade is quite small compared with a fan blade. Take P&W JT9D - fan blade mass about 4.5Kg and RPM 3800 or so. That's a hell of a lot of energy in the liberated blade, not to speak of the savage out of balance forces acting to destroy the bearing system. By comparison, the N2 blades are tiny, even though they spin at around 11000 rpm they contain a small fraction of the energy of a fan blade, likewise the out of balance forces.
I think the reason that only the fan cases are armoured is that the energy released by a liberated N2 blade is quite small compared with a fan blade. Take P&W JT9D - fan blade mass about 4.5Kg and RPM 3800 or so. That's a hell of a lot of energy in the liberated blade, not to speak of the savage out of balance forces acting to destroy the bearing system. By comparison, the N2 blades are tiny, even though they spin at around 11000 rpm they contain a small fraction of the energy of a fan blade, likewise the out of balance forces.
