h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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Aircraft are at greatest risk from drones (and, indeed, from
birds) during takeoff and landing. These are the times when
engine failure would be most disastrous, and also when the
plane is travelling slowest (making it easier for someone to fly
a drone into an engine). Also, planes tend to
come in quite
low for landing (and start out low for takeoff), putting them
within range of drones and birds.
Suggested, therefore, is a simple mesh of fine wires across the
engine intakes. The mesh would be coarse enough to allow
reasonable airflow, but just fine enough to stop drones and
birds. After takeoff, the mesh would be retracted to allow
unrestricted airflow and hence more economical flight. It
would be re-deployed just before landing.
Diaphragm
https://en.m.wikipe...AIris_Diaphragm.gif
[xenzag, Dec 30 2018]
[link]
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Retracting mesh.... that may be difficult to
realise, so I suggest a type of camera iris who's
individual segments are covered with perforations
like a colander. The perforations would
be large enough to allow sufficient air to flow for
take off and landing, and the iris would retreat
completely into the surrounding engine cowling
when not in use. See link. |
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//and start out low for takeoff// In fact, they
start off so low that rabbit sweepers are also
required to prevent these foolish creatures from
being run over and entangled by the aircraft
wheels. |
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//Retracting mesh.... that may be difficult to realise// |
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I have a cunning plan. Have individual wires on small
spring-loaded spools, attached in a ring around the intake.
Each wire runs to a fixed attachment point. The spools can
move around the rim of the intake. To deploy the mesh,
each spool travels around the rim until it's opposite its
wire's attachment point, stretching the wire across the
intake. To un-deploy, each spool travels back around the
rim until it's next to its wire's attachment point, the wire
spooling in as it does so. |
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Mechanical spiders could also generate a rapid web when there was a threat. |
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Equally, a grandmother strapped to each engine could knit
something when necessary. |
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Now you're getting there..... Pratt and Knitney engines. |
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OK, an update and improvement. The wires are now all
fixed at one end to a single attachment point on the leading
edge of the wing or, if the
engine is mounted forward of the leading edge, to a small
forward-pointing thing. In either case, all the wires are
anchored to one point above and in front of the engine. |
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The other ends of the wires are, as before, attached to
spring-loaded spools that can be moved around the rim of
the engine intake. |
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Now, when deployed (the spools having distributed
themselves evenly around the lower 2/3rds of the intake)
you have a sort of skewed 2/3rds cone extending from
above-and-in-front-of the engine to around the lower 2/3rds
of the intake. This arrangement will actually deflect any
oncoming debris downwards, below the intake. |
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When retracted (the spools having all moved up to the top
of the intake rim) you have a narrow bundle of wires that
are largely out of the intake stream, and hence won't
impact performance. |
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This is clearly a work in progress, and risks
becoming a bird's nest of entangled wires if just
one of them breaks, so I'm not convinced, but the
rabbit sweepers should be easier. I'm thinking wide
yard brushes, that are attached to the front of the
wheel structures, and turn sideways for storage as
the undercarriage is retracted. |
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//clearly a work in progress// We prefer to think of it as an
endeavour of constant improvement. |
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Trained eagles could predate rabbits, hares (very common at Schipol) and drones. |
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Small, armed UAVs could peform the same role, although onlookers would not be able to enjoy the spectacle of a magnificent bird of prey perched on top of a lighting gantry and tearing its kill apart. |
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//Trained eagles could predate rabbits// |
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No, it seems that rabbits predate eagles. The first fossil
evidence for rabbits is from about 40 million years ago; for
eagles, 36 Mya. _Trained_ eagles, of course, are much more
recent. |
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A big heavy hammer that swings out and knocks away anything approaching the engine? To save weight it can be filled with fuel. |
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"What? No, it's fine, really. Just need to bolt this robotic
hammer on, about here. Sheesh - wish I'd remembered to
bring the cordless drill. No, no, really, it's perfectly safe -
see? It can't quite swing round enough to hit the... ah, well,
OK, but it won't actually swing that far in use. Probably." |
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Sticking anything in front of a jet engine creates new
safety risks which will require further mitigation, so
on the whole I think it's probably a bad idea. Engines
have to be able to deal with a range of bird strike
events already and perhaps ingesting a drone would
actually be less severe. In any case I think the
solution is to prevent aircraft/drone collisions in the
first instance. |
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I'm not convinced the wires will cause a significant
downward deflection at almost 200mph, so really
they'll just be slicing the bird/drone before it gets
properly chopped up by the fan. The wires would
need to be pretty substantial to survive a high speed
collision with a stray bolt sucked up off the runway. |
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Also any pressure loss in the intake system will
reduce the engine thrust thereby prolonging the
take-off manoeuvre. Generally you want to get off
the ground as quickly as possible and out of the way
of near-ground threats. |
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// ingesting a drone would actually be less severe. // |
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No, it wouldn't. In practical tests, small metallic components cause disproportionate damage to the N2 spool if they get that far; damage to N1 is bad enough. |
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Observers may have noted that, thus far, we have abstained from launching a painstaking, merciless and devastating technical critique* of the idea. |
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That can change. We do hope that [MB] has a nice New Year present for us ... |
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*including numerous explanatory footnotes. |
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doitdoitdoitdoitdoitdoitdoit |
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If you are going to go this way, should not this device be two non touching conductive interleaved filters? |
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// doitdoitdoitdoitdoitdoitdoit // |
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No doubt it was your ancestors who patronised Roman amphitheatres, to watch the wild beast fights, executions and gladiatorial combats, revelling in the stench of blood and the sight of gore, and all the while munching on snack foods in between baying for yet more violence and cruelty. |
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I wonder if this applies to bagpipes? |
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//We do hope that [MB] has a nice New Year present for us // |
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Oh yes, we certainly do. Can I just check that you have some
Vaseline, a packet of fish-fingers and two AA batteries? If
not, I'll add those. |
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No, we have a good stock of all three items, and have also purchased extra curtain rings this year. |
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You did remember to get the brass ones this time? Only the
plastic ones tent to get brittle at low temperatures. I don't
want to have to take you to A&E for the third year running. |
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