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Turbofan bird ingestion

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Turbofan bird ingestion

Old 22nd Jan 2006, 22:26
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Smile Turbofan bird ingestion

Just wanted to get some other collegue's opinions on actions (return or not) after ingesting a bird after take-off.

Recently I ingested a bird on rotation and immediately noticed the pungent KFC smell (funny, it smells like fish in the intake) which was also strong enough for the purser to call me after gear was selected up.

No abnormal indications as vibration was only 0.3. Smell slowly dissapating, however still there after a few minutes.

In this case after landing I elected to return and after inspection and high thrust engine run (cook the remnants) aircraft was dispatched 3 hours later however on a previous identical scenario albeit a bigger bird, I came back to notice 5 blades bent forward an inch. (vibrations were only 0.6 throughout).

Let the analysis begin!
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Old 23rd Jan 2006, 00:38
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I guess it would help if you told us what airplane this occured on, and what engine make/type. And the flight plan (i.e. continental flight or crossing an ocean).
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Old 23rd Jan 2006, 04:32
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Ah! the wonderful smell of KFC, and the passengers asking "Are we having chicken today?"

For the couple of times that this has happened to me, I've simply kept a sharp eye on the engine parameters following the ingestion, particularly at the times that significant engine speed changes take place, i.e. reduction to Climb, Cruise thrust etc.

I must have been lucky in encountering only smaller birds, there was no indication of damage post-flight in any of the encounters. I have no doubt that a pelican or condor could have inflicted far greater damage.

Canuckbirdstrike, we await your typically well informed thoughts

Regards,

Old Smokey
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Old 23rd Jan 2006, 09:17
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yon ingested the bird not the aircraft

Anyone who ingests a whole bird of unknown provenance like Yon needs a dietician.
But engines seem to manage with small ones and as OS is a bi-motor geezer his donkeys might be a bit better certificated or just more modern than mine were. I presume his idea of a pelican is one that makes his needles wobble and upset his parameters. Terns, boobies and frigate birds are a slightly less serious wake category than a pelican but don't half spang Rollers and CF6's. We used to carry an extra person to blame on -200s but even steam gauges cannot foretell the outcome. So I guess the final arbiter is the engineer but which one?
Did the aircraft accelerate cleanly at all speed changes? Nary a wobble on the instrumentation? When it happened, no one quoted the Mayor of Hiroshima? Provided maintrol isn't a Beijing call centre I'm up for KLAX-EGLL, 411A, how about you?
By the way, they used to go straight through Avons no problem but those engines had a lot more bench-time, were single shaft and built like brick outhouses.

The "E"
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Old 23rd Jan 2006, 10:27
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ANybodyatall,

Good point. It was a B737NG, obviously with CRM56-7 engines. Domestic 1hr leg. Over water.

Yon.
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Old 23rd Jan 2006, 11:44
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It all depends: - the size of the engine, size of bird, etc.
If you are aware that a bird has been through the engine then the safest action is to land and have the power-plant thoroughly inspected. Irrespective of the flight time required to an appropriate airport the subsequent actions will depend on the engine indications.

If you smell the bird then this normally indicates that parts of it have gone through the core which could damage the ‘less robust’ components or even block the air path or bleed off-takes.

If it was a ‘ding’ on the fan then the chance of damage may be less, but the fan produces the thrust, which is susceptible to minor damage.
I have seen small birds ‘ding’ the fan and bounce out of the intake, generally without any damage at all, but then there is the airframe to think about.

I was unfortunate to have a simultaneous dual seagull strike, one through each engine of a twin jet. Everything appeared normal except the max N2 was only 83% with some vibration. Both engines continued to run, (they were Rolls Royce), but after landing at shutdown they ran down very quickly.
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Old 23rd Jan 2006, 14:39
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Land of course

Speaking as an engineer. If you know your engines have ingested a bird/birds, you have to land. You have no idea what damage if any has occured. Things may seem fine but you can't afford to to take that risk with your passengers or crew. Land and let us have a look to make sure it's OK.
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Old 23rd Jan 2006, 16:10
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If you only smelt KFC and the engine parameters were normal, how could you be sure the bird didn't go into an air-con pack intake? Would you have turned back for that? Its a subjective judgement for the pilot, but what is your , or your company's definition of an engine failure?
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Old 23rd Jan 2006, 16:26
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Ingested a bird on t/o roll last summer (jt-9) It did compressor stall so we aborted. The engine continued to run with no adverse signs, but we decided to go back to the gate for inspection. The engine was shutdown on the runway and we found substantial damage to the fan and inlet area.
The point is an engine can suffer considerable damage and continue to run for an unknown period of time. My belief is its always better to return safely than to let it get out of hand. Primary consideration is always passenger safety, not the cost of fuel.
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Old 23rd Jan 2006, 16:36
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Angel

If you only smelt KFC and the engine parameters were normal, how could you be sure the bird didn't go into an air-con pack intake?
Ehh, care to explain how that works?
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Old 23rd Jan 2006, 18:02
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Lots and lots of data on bird ingestions into turbofan engines and their results.

The pilot is advised to take note of his instruments and ears. The instruments display the engine health at the flight conditions, while your ears may pickup a surge (bang/boom/pop etc.) as well as a noticeable change in Buzz-saw. The later is indicative of bent blades. It is extremely rare for an engine which is continued without noticeable shifts in EGT to pack it up completely (no what ifs here, just historical data).

There have been some surprises later when engines which had ingested a bird and surged, were continued in service (they surged again always at inopportuned times)

If you get only a change in power without a permanent change in EGT or Buzz-saw, then the data shows that the engines have run-on without failing.

If you get an EGT shift or a permanent change in buzz-saw then there is no telling how much longer it will last unless of course you manage to baby it and get rid of the EGT effects or buzz-saw..
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Old 23rd Jan 2006, 22:58
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My experience thus far on ALF502/LF507. Of all the bird strikes where the engine was involved only one was heard. Several were discerned during walk-around aafter landing and smelling the KFC odour approaching the engine.

In one instance at a remote location engineering authorised an engine run, on completion of which, the remains of several smallish birds passed further through the compression stages, bogged the engine down, and an overtemp resulted.

The only engine strike I heard was a large Kite (hawk) going down #3 or 4, though I didn't know it had hit then engine at the time. The loudest bang I've ever heard in an aeroplane, one fan tip bent forward and I'd hate to think what might have happened during the ensuing 3.5 hr flight had we not rejected.

To answer Yon's question, I don't think there's a hard and fast rule. Had I hit the kite above V1 and heard the bang, I think I'd have burned to LWT and returned for landing.

Had I departed the remote location where the over temp occurred, I'd probably continue and monitor the engines closely, in the absence of some positive indicator of an ingestion.

As an aside I'm now operating aft mounted BR715s. I doubt one would hear anything abnormal with them from the flight deck, short of self destruction or stopping.
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Old 24th Jan 2006, 00:03
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Sorry for not wading in sooner, my day job interfered. Many of the other posts have raised the fundamental question - How do you know that there hasn't been any damage to the engine? The answer is you don't and there is lots of data to show that relying on cockpit displayed engine paramaters to form a judgment on the condition of the engine is not wise. Strike data and engine manufacture information shows that in many cases the engine will suffer a "delayed damage" failure. The only way to know for sure is to have the engine inspected by qualified personnel using boroscopes and/or black lights.

I am not proposing that every bird strike requires a return to land. Obviously some thought must be given to the size and number of birds struck. However, if the strike occurs in IMC (yes birds do fly in IMC) or at night, observations are problematic. To assist with making the decision you might want to frame it based on what engines are certified for with respect to bird strikes. With the excception of the very large engines like the GE90 RR Trent on the B777, the majority of jet aircraft engines are certified to ingest, at the aircraft liftoff speed, one 4-pound bird OR 8 1.5-pound birds OR 16 3-oz birds may not cause the engine to-- (1) Catch fire; (2) Burst (release hazardous fragments through the engine case); (3) Generate loads greater than those ultimate loads specified in FAR 33.23(a); or (4) Lose the capability of being shut down. (b) Ingestion of 3-ounce birds or 1 1/2 -pound birds, under the conditions prescribed above, may not-- (1) Cause more than a sustained 25 percent power or thrust loss; (2) Require the engine to be shut down within 5 minutes from the time of ingestion; or (3) Result in a potentially hazardous condition.

Another guideline to apply is that as altitude increases although the strike rate decreases BUT the the average weight/size increases and you are most likely going to hit a flocking bird.

Taking into account all the above you can see that if you ingest seagulls or waterfowl, particularly of you ingest more than one you will most likely have damaged the engine.

And we haven't even talked about airframe or collateral system damage that can occur from hitting a flock of birds - something not catered too in the certification standards.

Food for thought (sorry I couldn't resist)

Richard - A320 Pilot and Bird Strike researcher
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Old 24th Jan 2006, 12:05
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Originally Posted by 777fly
If you only smelt KFC and the engine parameters were normal, how could you be sure the bird didn't go into an air-con pack intake? Would you have turned back for that? Its a subjective judgement for the pilot, but what is your , or your company's definition of an engine failure?
??????? I guess you better revise your aircon pack operating theory 777fly. Pack intakes are for cooling airflow for engine bleed air. If you were to get a bird into a pack intake only and smell KFC then you have a seriously damaged heat exchanger and would also need to return as the pack probably wouldn't pressurise and would be leaking hot bleed air into the pack bays with all the fire and other associated implications of that.
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Old 24th Jan 2006, 12:21
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Sorry guys, you are right. Just checking if you are awake at the back. Brain doesn't work too well at 4am in Seoul! Even so, its a difficult set of options if all engine parameters are normal after flying through a bird. Whats the definition of engine failure?
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Old 25th Jan 2006, 04:50
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Yon Garde,

I tend to agree with Old Smokey... As long as all the gauges read okay (and all else seemingly normal), for that flight, I would have done what you did--continue on. (especially considering it was a short 1hr flight with the aircraft and engine type you had on hand)

However, Canuckbirdstrike also makes a valid point that you as a pilot obviously can't tell from your seat what the physical damage to the engine might be. It is for that reason why if I were to fly say a twin on an overseas flight, I would have returned for an engine inspection... Not worth the risk. Plus I hate swimming.
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Old 25th Jan 2006, 16:05
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... and you are most likely going to hit a flocking bird
The very words that pilots through history have used.
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Old 25th Jan 2006, 17:17
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If a ingestion is suspected particularly if any other indications are apparent,return. An incipient failure may occur,surge margins might be reduced,perhaps only becoming apparent at an increased flight level.
Flying with an engine that 'may' be about to fail is not ideal,you may also prevent further damage to an 'extremely' expensive engine which could necessitate replacement,unprogrammed downtime & a potentially pricey QEC rework.
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Old 25th Jan 2006, 18:42
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From what I can remember from my 'Advanced Boroscope Inspection' (sic) course the CFM 56 is particularly susceptible to turbine blade damage post bird strike as the feather quills block the blade cooling holes.

Result is very expensive, turbine blades melted and possible engine failure.

Food for thought next time you consider your options.
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Old 25th Jan 2006, 22:28
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It's so hot back there I'd expect any feather residue (finely chopped by the compressor) would be quickly incinerated. So the "feather quills" inspection is a bit hard for me to - umm - swallow.
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