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Chock

Interesting engine modification lol

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Got asked to check the engines on an A321 this morning, as apparently one of them had 'some damage' and it had been suggested we might have caused it at Manchester prior to it departing for Turkey earlier yesterday. The damage didn't prevent it from flying back into Manchester from Antalya, but when it landed and we'd finished unloading it and stuff, I had a look and I took this picture, where you can see the fan blade is sort of 'dog eared' at the bottom (I've had to tweak the colours and sharpen a bit because it was dark and very amber coloured owing to the airport's sodium lights on the ramp when I took it at about 5.30 am). Interesting to note how the fan blade is bent, I suspect from the inside (i.e. by some force on it from behind) as far as I can tell, which would suggest to me that some engineer has done it from behind the blade when accessing the engine intake from the other side. We wouldn't normally have access to the other side of those fins, so I doubt anyone at our company did this damage. It will be interesting to see what the engineers at Manchester make of this.

wM8ZVS5.jpg

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I’ve seen that exact kind of damage several times caused by FOD known to have entered from the front. I suspect the engine may have ingested a small pebble or something similar - perhaps while applying reverse thrust, which is the most likely time for such a thing to happen. 

Typically tip curl damage will require replacing the blade - it’s not permissible to try to straighten out the bent section. Fortunately blade replacement is relatively easy to do on-wing.

Nicks in the edge of a blade mid-span can often be removed in place by blending out the damage with a fine-tooth file (within limits established by the engine manufacturer) - as long as the nick did not produce any significant distortion in the shape of the blade’s airfoil.

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Yeah, I figured it would be an easy fix, i.e. simply replacing the blade, although I should imagine it has to be balanced too.

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8 hours ago, Chock said:

Yeah, I figured it would be an easy fix, i.e. simply replacing the blade, although I should imagine it has to be balanced too.

If a blade has to be replaced, they will often replace the one directly opposite as well. Blades can be ordered in matched sets with identical weights (or as close as possible), which often eliminates the need to rebalance the whole fan. Balancing can be a lengthy process requiring multiple engine runs with special test equipment attached. It’s easier to buy pre weight-matched blades than to try to find a single blade of a specific weight to match the opposite one already installed. (The weight of each blade in grams is marked on the root).

They are not cheap. We had to buy a matched set last winter because of tip curl caused by ice ingestion on a CF-34 on a CRJ-200. As I recall, they cost about $32,000 each! I assume the cost is even higher (per blade) on a larger engine like that on the Airbus.

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Yup, aeroplane parts are expensive, however I should imagine the airlines can get some sort of deal for having to get a lot of parts regularly.

I've not been in the maintenance facility at Manchester too often, but it is an extensive one, so I'm sure they're well able to do quite fancy maintenance, and there is of course the engine test area alongside it even though some test runs are occasionally done on stand.

I know that last year they were literally the first place to repair a Boeing 787 which had been damaged when a service vehicle had driven under one and damaged the skin of its belly. At the time, since the 787 was fairly new in service, it wasn't actually known whether a repair of that type could even be done, and for a while it was touch and go whether the airliner would either have to have an entire rear end put on it, or be scrapped completely, but some Boeing engineers flew over and checked it out and it was eventually determined that it could be patched there, so it's certainly a capable repair place. I seem to recall hearing that repair cost about eleven million quid in total. I hope they didn't send the person who drove into the thing the bill!

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