TazzrassinIDA From United States of America, joined Jun 2007, 38 posts, RR: 2 Posted (5 years 11 months 3 days 12 hours ago) and read 3733 times:
Ok, the searches did not pull anything similar to this, so here it goes. (not that I am proficient at using the searches yet either.)
For some odd reason, I started thinking about this today. Who know maybe I had too much time on my hands. I am familiar with scenes in movies, like in Castaway, where it shows a jet running under water, threatening to eat the stars. There is no way this could happen I know. What if a plane crashed into water in such a way that the engine stayed attached to the wing, and it's fuel supply. The intake is clear of the water, sucking only air, and the safeties that should shut it down have failed. Would it be possible for it to keep running if the exhaust end were under water?
In my pondering, given the "perfect" conditions for the engine to run, except that the tail end is submerged, I would say no it would not. I would think it is kind of like plugging the tail pipe of a car, the engine would eventually not be able to sustain its self.
I hope to stir up some good natured conversation about this, express a question I have been pondering in hopes that my hypothesis is confirmed by others, and see how things go.
Fr8Mech From United States of America, joined Sep 2005, 4260 posts, RR: 12 Reply 2, posted (5 years 11 months 3 days 11 hours ago) and read 3685 times:
Using your assumptions, I see no reason why it woud not continue to run. Performance may suffer a bit, but water at a depth of about 12 feet, assuming the engine is vertical, would be easily pushed away by the high speed exhaust.
TazzrassinIDA From United States of America, joined Jun 2007, 38 posts, RR: 2 Reply 3, posted (5 years 11 months 3 days 8 hours ago) and read 3615 times:
Wow, that video is pretty amazing. I guess it is possible... Thanks for sharing.
SEPilot From United States of America, joined Dec 2006, 6258 posts, RR: 39 Reply 4, posted (5 years 11 months 3 days 3 hours ago) and read 3529 times:
As long as the engine has fuel and sufficient air and appropriate electrics (I'm not sure what jet engines require by way of electrical signals; piston aircraft engines require none) it will continue to run, regardless of whether the exhaust is under water or not. What would probably cause it to stop (assuming it doesn't run out of fuel) is water getting into the fuel, as the tanks have to be vented and if the vents are under water they will suck water instead of air, or if the engine settles into the water enough to suck enough water to drown it. It can actually suck a fair amount of water and still run, but there is a limit, of course.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
SEPilot From United States of America, joined Dec 2006, 6258 posts, RR: 39 Reply 6, posted (5 years 11 months 2 days 14 hours ago) and read 3282 times:
Quoting 3MilesToWRO (Reply 5):
Well, not "signals" maybe, but sparks are useful, I suppose.
An aircraft piston engine has magnetos, which require no outside input, and so I consider them part of the engine. No outside signal is required for them to keep running; there is a grounding wire to short them out to prevent them from firing, but they will run happily all day long with no external connection.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
FLY2HMO From , joined Dec 1969, posts, RR: Reply 7, posted (5 years 11 months 2 days 10 hours ago) and read 3220 times:
If you somehow isolate the engine core from the water, and give it some kind of a snorkel for the intake and exhaust, then yeah, it could work (I'm talking about a turbofan here). I don't think it would work too well though, it takes thousands of HP produced by the turbine section to make the fan turn in air, and water is only *slightly* more dense and heavy than air
In a pure turbojet, or turboprop, hell no, there's no way that could work. While they can sustain extreme rain intake, they are not submersible.
Very close indeed, but if you look closely, the waterline barely goes into the exhaust, and I really I doubt the last turbine stage is in contact with the water at all, the waterline is just too low.
SEPilot From United States of America, joined Dec 2006, 6258 posts, RR: 39 Reply 9, posted (5 years 11 months 2 days 3 hours ago) and read 3124 times:
Quoting FLY2HMO (Reply 7):
In a pure turbojet, or turboprop, hell no, there's no way that could work. While they can sustain extreme rain intake, they are not submersible.
The situation was that the intake was out of the water but the exhaust was under water. As long as the engine was running when it went in I believe it could continue running until it sucked too much water in the intake. I totally agree that any substantial submersion (meaning a couple of inches) of the intake would drown it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
Moriarty From Sweden, joined Jan 2006, 160 posts, RR: 0 Reply 10, posted (5 years 11 months 3 hours ago) and read 2773 times:
Never the less, that video is quite remarkable! It is not too common to see crashes and their aftermath up close like that. Glad everyone seemed ok. Amazing the guy filming the whole thing kept shooting instead of assisting. I guess he made the decision that there was no need for more helping hands.
What I failed to understand was if the engine spooled up due to some technical reason or if there actually was a pilot left trying to do something (heroic or stupid, I'm not the person to judge that if so)...
Airfoilsguy From , joined Dec 1969, posts, RR: Reply 11, posted (5 years 11 months 2 hours ago) and read 2749 times:
Quoting Moriarty (Reply 10): What I failed to understand was if the engine spooled up due to some technical reason or if there actually was a pilot left trying to do something
No one was left in the plane. I believe the engine restarted when they were trying to tie off the jet to the boat using some of the jets wiring. By the way the guy got a new jet with an ironic registration.
Starlionblue From Hong Kong, joined Feb 2004, 15871 posts, RR: 66 Reply 13, posted (5 years 10 months 4 weeks 1 day 21 hours ago) and read 2688 times:
Quoting Moriarty (Reply 10): Amazing the guy filming the whole thing kept shooting instead of assisting. I guess he made the decision that there was no need for more helping hands.
I would like to think so. But he probably just thought: "This will be great on YouTube"...
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Airfoilsguy From , joined Dec 1969, posts, RR: Reply 14, posted (5 years 10 months 3 weeks 6 days 19 hours ago) and read 2451 times:
Quoting Moriarty (Reply 10): Amazing the guy filming the whole thing kept shooting instead of assisting. I guess he made the decision that there was no need for more helping hands.
I am one of the first to criticise people for filming and not helping but what could this guy have done? All the action was in the water and I don't think he had a boat. He was also the first person to call 911.
F14D4ever From United States of America, joined May 2005, 319 posts, RR: 4 Reply 16, posted (5 years 10 months 3 weeks 6 days ago) and read 2266 times:
Quoting TazzrassinIDA (Thread starter): What if a plane crashed into water in such a way that the engine stayed attached to the wing, and it's (sic) fuel supply. The intake is clear of the water, sucking only air, and the safeties that should shut it down have failed. Would it be possible for it to keep running if the exhaust end were under water?
Absolutely not.
Quoting VC-10 (Reply 15): On a modern engine you would have to keep the EEC & the control alternator dry.
The EEC is the least of the concerns in this scenario. With the exhaust under water, there would be insufficient pressure drop across the turbine to sustain compression, which in turn means insufficient pressure and temperature for combustion. At some point as the combustor inlet p & t spiraled down, the compressor would surge violently, at which point it's all over.
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