Birds and planes and crashes.

[Locutus of Bored]

How about something like this?



The goal wouldn't be to prevent the impact entirely, but to reduce the impact velocity of the birdstrike enough (through multiple hits before it reached the engine) that the resulting ingestion into the fanblades might not be catastrophic.

There are planes that use similar curved intakes like this (stealth aircraft for example, so there's no direct line of sight to the non-stealthy engines to reflect RADAR), so I don't think it restricts the airflow so much as to be unfeasible.

It probably wouldn't prevent catastrophic failures entirely, but it might greatly reduce them. Plus it has other benefits like preventing foreign object ingestion on the ground, like keeping that guy on 'Lost' from getting sucked into the engine.

The cost of retrofitting existing aircraft with intakes of this type would be high but feasible.

 

[Trekker4747]

How about something like this?



The goal wouldn't be to prevent the impact entirely, but to reduce the impact velocity of the birdstrike enough (through multiple hits before it reached the engine) that the resulting ingestion into the fanblades might not be catastrophic.

There are planes that use similar curved intakes like this (stealth aircraft for example, so there's no direct line of sight to the non-stealthy engines to reflect RADAR), so I don't think it restricts the airflow so much as to be unfeasible.

It probably wouldn't prevent catastrophic failures entirely, but it might greatly reduce them. Plus it has other benefits like preventing foreign object ingestion on the ground, like keeping that guy on 'Lost' from getting sucked into the engine.

The cost of retrofitting existing aircraft with intakes of this type would be high but feasible.

Somewhere there's video a man actually getting sucked through a jet engine... and surviving!

 

[Locutus of Bored]

Somewhere there's video a man actually getting sucked through a jet engine... and surviving!

http://www.metacafe.com/watch/232469/guy_sucked_into_jet_engine_full_story/

Luckily his helmet flew into the blades and slowed them down before he got sucked in, or alternatively, to borrow his fellow sailor's explanation, "God must have held on to his foot." Of course, God sort of dropped the ball on the whole getting sucked into the air intake in the first place business.

 

[Marc]

The bird doesn't have to hit the engine to bring the aircraft down. USAF lost a B-1B (incl. several crew fatalities) to a pelican a few years back I believe.

Over 21 years ago actually (just looked it up on wiki)

They had a bird strike on the leading edge that raptured the fuel lines.

The strike occurred at low altitude so there wasn't much time. There were 6 crew onboard, 3 survived as they were in they ejection seats, of the three killed, 1 was in an ejection seat, two were in jump seats (so manual bailout).

 

[Deckerd]

Somewhere there's video a man actually getting sucked through a jet engine... and surviving!

http://www.metacafe.com/watch/232469/guy_sucked_into_jet_engine_full_story/

Luckily his helmet flew into the blades and slowed them down before he got sucked in, or alternatively, to borrow his fellow sailor's explanation, "God must have held on to his foot." Of course, God sort of dropped the ball on the whole getting sucked into the air intake in the first place business.

I prefer the way Capt Reynolds does it.

 

[Lindley]

The same thing you do if the engine fails for any other reason.

Crap my pants and pray that I land in a marshmallow factory?


J.

A) Airspeed to 65 knots (best angle of glide in a 172, it'll get you about 1.1 miles for every 1000 feet, more with a tailwind).
B) Best place to land. If there's an airport anywhere nearby, head for it; and airports (including private ones) are more common than many people realize, so there's a decent chance of that. Otherwise a dry field or interstate make good landing sites. At night, you head for a dark area. Near lights, but not in the middle of them. Even if you choose an area which turns out to have trees, you can arrange for the plane to just "settle" onto them and minimize the impact. If you're over water head for shore; water landings in a Cessna 172 are not terribly survivable. A good flight plan will always give you a glide path to land while over water.
C) Check. Verify all settings (fuel cutoff disengaged, fuel selector drawing from both tanks, etc), and attempt engine restart. If engine restart fails, shut down the engine entirely to minimize chance of fire.
D) Declare. On the emergency frequency 121.5 or, if applicable, the nearby tower frequency, declare a mayday. State your location, altitude, and attempted landing site. Squawk 7700.
E) Exit. Prior to landing, pop the pilot and passenger doors open to minimize the chance of being trapped if the airframe gets twisted. Once down, leave the plane quickly and move a safe distance away.

Did I miss anything? As you may be able to tell, it's much better for an engine failure to occur at high altitude than low. Counter-intuitive, but true. A failure on takeoff is just about the worst time for it to happen.

 

[Nerdius Maximus]

I don't see how even some taut chicken wire would do either of those to any measurable or detrimental effect.

Given the amount of thrust generated, I suspect any reasonably large object (especially many of them, as in the case of the US Air flight) would simply crash through the screen on its way to getting sucked into the engine.

What about some stiff rods spaced, say, 2inches apart in a grid-pattern? Something robust and fairly sturdy? I mean, yeah something weak like chicken-wire isn't going to cut it but maybe it'd be something worth tryng with heavy-duty (but obviously light weight) rods? (Not in practicality at first, obviously, but in wind tunnels/tests.)

It wouldn't have to be a tight grid just a small enough that it could preclude a bird from getting in there.

Stiff rods...

 

[RoJoHen]

Bird countermeasures!

And so it came to pass...the first deflector dish was invented.

 

[Chimpy Chompy]

How about something like this?

I think that would reduce the velocity of air reaching the compressor as well as that of the chunks of bird, and engine performance will suffer as a result.

 

[Chimpy Chompy]

Just had a chat with someone more expert in these things. A duct like that would result in varying flow characterstics across the inlet to the engine itself - ie air going faster in some places than others. Which isn't ideal. Not to mention, modern airliners have hugely wide inlets (to take in as much massflow as possible), so you'd have a huge metal duct sticking out the front of each engine, with various structural implications.

You mentioned stealth jets, i'd be interested to see how they've done it. Like I said I'm sure it is doable, probably just impractical from the perspective of commercial aviation.

Few other thoughts - most birdstrikes in generally hopefully just go through the bypass flow, ie the only bit of machinery they actually hit is that big fan on the front, then it's clear space all the way out. It's only if one goes through the core engine (ie into the compressor) that you've got problems. So I think engineers take their chances on the odd lone bird - as opposed to a whole flock of them - not being disastrous.

re: putting a grid on the front, problem is that if it comes apart somehow, bits of metal through your engine will do more harm than bits of bird!

 

[melancholymecha]

all this talk of birdstrikes has reminded me of when Fabio got hit by that goose...

 

[Sheep]

I will use this opportunity to post Richard Hammond and the chicken gun:

http://www.youtube.com/watch?v=PgxxmTOZJBE

This doesn't really address the issue of how to prevent birds from getting sucked into a jet engine, but I'm wondering if such materials could be used in an engine to make such an incident slightly less catastrophic.

 

[Mutai Sho-Rin]

Who's the flying mod? Or has he retired now?

jkladis is a pilot and I have about 900 hours in single engine aircraft (Cessna and Grumman). I guess you could call me a "retired" mod.

 

[Amaris]

The same thing you do if the engine fails for any other reason.

Crap my pants and pray that I land in a marshmallow factory?


J.

A) Airspeed to 65 knots (best angle of glide in a 172, it'll get you about 1.1 miles for every 1000 feet, more with a tailwind).
B) Best place to land. If there's an airport anywhere nearby, head for it; and airports (including private ones) are more common than many people realize, so there's a decent chance of that. Otherwise a dry field or interstate make good landing sites. At night, you head for a dark area. Near lights, but not in the middle of them. Even if you choose an area which turns out to have trees, you can arrange for the plane to just "settle" onto them and minimize the impact. If you're over water head for shore; water landings in a Cessna 172 are not terribly survivable. A good flight plan will always give you a glide path to land while over water.
C) Check. Verify all settings (fuel cutoff disengaged, fuel selector drawing from both tanks, etc), and attempt engine restart. If engine restart fails, shut down the engine entirely to minimize chance of fire.
D) Declare. On the emergency frequency 121.5 or, if applicable, the nearby tower frequency, declare a mayday. State your location, altitude, and attempted landing site. Squawk 7700.
E) Exit. Prior to landing, pop the pilot and passenger doors open to minimize the chance of being trapped if the airframe gets twisted. Once down, leave the plane quickly and move a safe distance away.

Did I miss anything? As you may be able to tell, it's much better for an engine failure to occur at high altitude than low. Counter-intuitive, but true. A failure on takeoff is just about the worst time for it to happen.

Wow, that sounds far more survivable than my plan.
Thanks, I'll remember that should it ever happen!

J.

 

[M'Sharak]

Who's the flying mod? Or has he retired now?

kladis is a pilot. Lindley has been doing the training/coursework for a pilot's license. Mutai is also a licensed pilot but is no longer modding on this board. mrcoaster is flight crew for one of the airlines, but not a pilot.

 

[Locutus of Bored]

Just had a chat with someone more expert in these things. A duct like that would result in varying flow characterstics across the inlet to the engine itself - ie air going faster in some places than others. Which isn't ideal. Not to mention, modern airliners have hugely wide inlets (to take in as much massflow as possible), so you'd have a huge metal duct sticking out the front of each engine, with various structural implications.

Ahh, thanks. I figured lowered fuel efficiency as a result of the duct would likely be the biggest hurdle to this being feasible.

You mentioned stealth jets, i'd be interested to see how they've done it. Like I said I'm sure it is doable, probably just impractical from the perspective of commercial aviation.

The B-2 Spirit stealth bomber seems like a good example, since it probably has the most drastically angled intakes.

re: putting a grid on the front, problem is that if it comes apart somehow, bits of metal through your engine will do more harm than bits of bird!

I wonder if they've ever had that problem occur with the F-117's RADAR absorbing intake grill or if the composites and the angle used somehow lessen or absorb the impact.

 

[Chimpy Chompy]

Hmm, I didn't realise there was a kink on the outlet as well!

re: the F117, there's a relatively small space to cover over with the grill. Airliners use high-bypass engines, with correspondingly wider inlets. A bigger grill will have a higher risk of structural failure.

(It's probably also a just plain more acceptable risk on a fighter jet vs an airliner)

 

[Marc]

How about something like this?

Just remebered that the inverse of that design has been used.

The Boeing 727 used an S-tunnel for the intake on the 3rd engine. The nacelle was on top of the fuselage but the actual engine was in the fuselage.

 

[Gaseous Anomaly]

Imagine if you will an aircraft taking off at a minimum of 160 knots, anything that comes in contact is a projectile. Here is a picture of a bird strike on a Blackhawk helicopter.
Maximum speed: 159 kt (183 mph, 295 km/h)
Cruise speed: 150 kt (173 mph, 278 km/h)

Boeing 757
Cruise speed .80 Mach (530 mph, 458 knots, 850 km/h at 35,000 ft cruise altitude)

I'm not sure what the take off speeds are but I'd guess its 160 knots or better. With a screen on the front of the engine you'd have just that much more FOD for the engine to ingest.

 

[MANT!]

in 1984,a B-52G at Blytheville AFB hit an eagle at 400kts during a low level run in Arizona, it entered the aircraft just below the copilots window, came through the instrument panel (smashing through wire bundles, pitot-static lines,structural supports and several instruments on it's way through) and hit the copilot, nearly killing him. I saw the damage and the interior was frightening to behold.

The aircraft was grounded for 3 months while Boeing engineers, assisted by USAF personnel, repaired all the damage.