FOD into turbine intake
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FOD into turbine intake
I'm just trying to support a safety case at work, to do with jet intakes and FOD ingress.
Can anybody point me at reported instances (or for that matter a few anecdotes are interesting) of anything - particularly from the ground, and particularly when an aircraft was stationary or taxiing, being sucked into the intake of a turbofan or turbojet.
G
Can anybody point me at reported instances (or for that matter a few anecdotes are interesting) of anything - particularly from the ground, and particularly when an aircraft was stationary or taxiing, being sucked into the intake of a turbofan or turbojet.
G
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In general, the worst case is initial runup above idle to initiate taxi. Often a vortex forms (sometimes visible in high humidity) that starts scrubbing the tarmac and getting loose sand, pebbles, etc. bouncing. If they bounce high enough they get caught up in the inlet flow. A relative small patch of tarmac is the "feeder" zone - directly below the inlet.
Once the aircraft is rolling, the feeder zone only sees the vortex for a short time so it's less of an issue. Plus, the engine is soon back at idle, so the vortex is weaker.
Having spent much of my career "flying" engine test cells, I can tell you some cells are chronic producers of visible vortices - appearing from the floor, sidewalls, or sometimes the ceiling.
Addendum: Harold Klein of Douglas did some work (1957) referenced here.
Once the aircraft is rolling, the feeder zone only sees the vortex for a short time so it's less of an issue. Plus, the engine is soon back at idle, so the vortex is weaker.
Having spent much of my career "flying" engine test cells, I can tell you some cells are chronic producers of visible vortices - appearing from the floor, sidewalls, or sometimes the ceiling.
Addendum: Harold Klein of Douglas did some work (1957) referenced here.
Last edited by barit1; 22nd Jan 2006 at 17:13.
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A number of stands at LHR Terminal 1 have had the areas immediately underneath the jettys cages off to avoid ingestion. In particular there were a number of cases of ingestion on A319 aircraft. BAA responded with aneffective measure.
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Running A 737 At Riyahd At Power With Test Set (manifold Press Gage) On Short Hose, Heard Noise Looked Over At My Mate In Rt Hand Seat And Said We Will Need New Test Set, But A Bit Of Rapid Dressing Of Fan Blades And A/c Left On Time With A Lesson Learned.
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Ghengis - if FOD was such a benign event, why would so much money be devoted worldwide to education and policing via tarmac sweepers and FOD stations on piers and ramp vehicles ? Case proven. 
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Of course it's not a good thing, the issue I'm handling is the various ways of preventing it, of which that's one.
Specifically I'm looking into ways of predicting vortex generation (and preventing it) as a safety (and cost) benefit.
G
Specifically I'm looking into ways of predicting vortex generation (and preventing it) as a safety (and cost) benefit.
G
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Fan blades are expensive hardware. Replacing even half a set will buy a lot of ramp-cleaning.
But it goes beyond that; even if you can save blades by dressing, their efficiency (fuel burn) suffers, and that is a long-term cost.
But it goes beyond that; even if you can save blades by dressing, their efficiency (fuel burn) suffers, and that is a long-term cost.
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This link gives an extreme (and fatal) example:
http://www.aero-news.net/index.cfm?C...9-0e5d3a331a7b
http://www.aero-news.net/index.cfm?C...9-0e5d3a331a7b
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As I'm primarily an engines man (although I'm in the middle of a "cross dressing" course to become a rigger as well. Good ol' RAF. Back to the way it was done 15 years ago!), I always sanitize the area around intakes before starting engines. Mainly because it's me that has to change the bloody engine if it gets FODded.......
Last incident we had was a strap securing bolt on a ground-running guard broke, and got sucked down the intake, necessitating an engine change.
Last incident we had was a strap securing bolt on a ground-running guard broke, and got sucked down the intake, necessitating an engine change.
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FOD Damage
Genghis,
FOD isn't restricted to causing damage to BRT's, an errant bolt or peice of metal will cause damage to wheels, tyres, etc. The secondary damage from a failed tyre during a take-off role, can vary from a few hours delay changing a couple of wheels, hydraulic hoses, and plenty of spped tape, to week in the shed during fairly major structural repairs.
Worst case scenario.... Concorde!
The tyre failure which triggered that tragic chain of events was a result of a piece of a DC10 T/R cowl which fell onto the runway.
FOD is and always be a serious hazard to aircraft safety, you shouldn't need to build a business case to address this.
FOD isn't restricted to causing damage to BRT's, an errant bolt or peice of metal will cause damage to wheels, tyres, etc. The secondary damage from a failed tyre during a take-off role, can vary from a few hours delay changing a couple of wheels, hydraulic hoses, and plenty of spped tape, to week in the shed during fairly major structural repairs.
Worst case scenario.... Concorde!
The tyre failure which triggered that tragic chain of events was a result of a piece of a DC10 T/R cowl which fell onto the runway.
FOD is and always be a serious hazard to aircraft safety, you shouldn't need to build a business case to address this.
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Having been flying for two decades I'm well aware of this.
What I'm doing is building a business case to investigate the creation specifically of the vortices that can suck large objects into engine intakes. The stronger the case I can make, the more freedom we'll get to investigate this widely. In my experience the two strongest arguments to get money for this sort of job are (a) loss of life, and (b) loss of revenue [sadly not always in that order.] So that's what I'm doing.
If I held the purse-strings myself, rest assured, I'd not need to make the case! All this anecdotal stuff however, is great and helps me a lot. (That said, there is always a finite budget, even for safety, and one has to prioritise.)
That said if anybody knows any numbers - hard pounds or dollars for estimated costs due to engine FOD ingestion, that would help me even more.
G
What I'm doing is building a business case to investigate the creation specifically of the vortices that can suck large objects into engine intakes. The stronger the case I can make, the more freedom we'll get to investigate this widely. In my experience the two strongest arguments to get money for this sort of job are (a) loss of life, and (b) loss of revenue [sadly not always in that order.] So that's what I'm doing.
If I held the purse-strings myself, rest assured, I'd not need to make the case! All this anecdotal stuff however, is great and helps me a lot. (That said, there is always a finite budget, even for safety, and one has to prioritise.)
That said if anybody knows any numbers - hard pounds or dollars for estimated costs due to engine FOD ingestion, that would help me even more.
G
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Genghis,
What kind of case are you trying to make ?
In my experience most FOD damage is because the rules are bent.
( yes after 20 hours when its hissing down with rain or -5 it is easy to bend rules
)
Many times a proper FOD inspection is not done.
All the manuals have danger areas at various power settings but how many people that run engines could either quote those figures or visualise where they are in relation to the intake.
Doing a static run should be relatively easy to police. Having to taxi to a run up area is more difficult.
Another problem is when you position on a run pad to do power assurance and then the wind changes so you have to move ( L1011 No 2 engine
)
I think that if you look at the number of engine runs carried out, the number of FODs is not that many. Of course the accountants will tell you one is too many - but hey **it happens
I am not sure what you can do to prevent it.
What kind of case are you trying to make ?
In my experience most FOD damage is because the rules are bent.
( yes after 20 hours when its hissing down with rain or -5 it is easy to bend rules
)Many times a proper FOD inspection is not done.
All the manuals have danger areas at various power settings but how many people that run engines could either quote those figures or visualise where they are in relation to the intake.
Doing a static run should be relatively easy to police. Having to taxi to a run up area is more difficult.
Another problem is when you position on a run pad to do power assurance and then the wind changes so you have to move ( L1011 No 2 engine
)I think that if you look at the number of engine runs carried out, the number of FODs is not that many. Of course the accountants will tell you one is too many - but hey **it happens
I am not sure what you can do to prevent it.
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The tyre failure which triggered that tragic chain of events was a result of a piece of a DC10 T/R cowl which fell onto the runway.
by tako
by tako
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there was an instance in the mid 90's at a certain scottish airbase where they had a civilian contractor in to basically erase the tyre marks on the thresholds of the runways. they used a form of shot blast ( actual material unknown!) but the tally ended up as 1 swing wing a/c ( crew got a tie etc and a nice trip in a helicopter, and no major injuries if i remember correctly!! ) but the tally of engine changes was close to if not in double figures!!!! like i say few years ago but the point is these shot blasty things were microscopic in size but caused untold damage and nearly the worse consequences possible...
