OT : Why do they set the engines so far apart on Jet planes ?

I really don't know DT. I've never heard of that happening. Perhaps because the remedial reaction is usually instantaneous :) Reduce power & reduce AoA.

Here's an excerpt from the F100C Flight Handbook (T.O. 1F-100C-1) "...If the engine is allowed to continue operation in a stalled condition, the temperature of the burning gasses increases until serious damage to the turbine section occurs, and the airflow fluctuations may damage the engine air intake duct structure.." So I'm guessing that serious damage could include thrown buckets *and* damage to the intake duct structure could result in engine ingestion of chunks of duct :( - not a good diet for turbine blades. I have never seen fire emitting from the intake (day or night) and there is no mention of that possibility in the Dash One so I'm guessing that it probably doesn't happen - at least not as far as the J-57 engine was concerned. remember I'm talking Abacus days - I'm sure I'm sure engines have improved a bit since then ;-))

On Feb 23, 7:59 am, "Ed Forsythe" wrote:

messagenews: snipped-for-privacy@proxy02.news.clara.net...

Caviation also happens when air is sucked into the prop. This air can come from a couple of sources: along the keel of the boat, or directly down from the surface above the prop. If the boat has a keel that is too deep ( it's like blade running along the center of the bottom of the boat, front to back, and is to prevent sliding sideways in a turn), that keel will allow air from under the front of the boat to travel along the inside of it during a turn and get into the prop. The air displaces the water and the prop overspeeds and makes bad noises. The solution is to reduce the length of the keel (shorten the front of it) and/or trim it to make it shallower. Better yet is to take it off and install a short but deeper fin well back on the bottom, somewhere around the CG. Props on outboards on stern drives are behind the boat's transom and can suck air down into them on a sudden acceleration from a stop. The prop pumps the water out from under the transom and air gets pulled in, like a toilet flushing or tub draining. Straight-shaft or vee-drive setups don't suffer so much this way, since the prop is well forward under the boat, making room for the rudder behind it. An outboard or stern-drive has a small cavitation plate above the prop to help prevent the drawing in of air. Larger cavitaion plates are available as retrofits, and they're often known as lifting devices to make stern-heavy boats get on plane faster. They act like a wing in the water.

Dan

Having air sucked into the prop is indeed a bad thing, but is not really "cavitation" per se.

Here's a good definition from the Wikipedia site:

"...the formation of vapor-filled cavities in the interior or on the solid boundaries created by a localized pressure reduction produced by the dynamic action of a liquid system without change in ambient temperature. Cavitation in the engineering sense is characterized by an explosive growth and occurs at suitable combinations of low pressure and high speed in pipelines; in hydraulic machines such as turbines, pumps, and propellers; on submerged hydrofoils; behind blunt submerged bodies; and in the cores of vortical structures. This type of cavitation has great practical significance because it restricts the speed at which hydraulic machines may be operated and, when severe, lowers efficiency, produces noise and vibrations, and causes rapid erosion of the boundary surfaces, even though these surfaces consist of concrete, cast iron, bronze, or other hard and normally durable material."

Good flying, desmobob

yes, but cavitation doesn't happen in a gas. Its already boiled.

SOMETHING happens alright, but its not strictly known as cavitation.

Jim said Yes, *cavitation is just a low pressure area in a flow*.

The point is that "cavitation" is not that... it is strictly applied to what he said next.

"In liquid that pressure can drop to the point that gas bubbles form and then collapse and then doing all kids of nasty things."

I am not sure that is strictly 'cavitation' either...

Intersting stuff tho.

Uhhuh......and what did I say?

You said "cavitation is just a low pressure area in a flow"

In which case there is a large bit of atmospheric cavitation, and a lot of precipitation heading my way. :-)

Which is a bugger, cos I have a new model to maiden. :-)

I guess you are ignoring the "In liquid" part of the statement? What is your point?

Jim

Lots of engineering considerations go into engine location; most notably the aircraft CG considerations on the swept wing as well as weight distribution and wing loading across the whole wing. The latter creates specific fuel management procedures that must be followed. Airflow would only be a consideration if an engine were located way inboard, but even that problem can be solved by the engineers. As to compressor stalls, they can be caused by many situations, including AOA, a malfunctioning fuel controller, or even a situation where the inlet guide vanes do not properly position themselves. As far as engine-out forces, I might add that the 747 engines are installed/mounted with an ever-so-slight amount of outthrust (1 ~ 2 degrees)

Cheers -- \_________Lyman Slack________/ \_______Flying Gators R/C___/ \_____AMA 6430 LM____ / \___Gainesville FL_____/ Visit my Web Site at

Their point is - *My* cavitation is bigger 'n your'n - ;-))

My point is that your first sentence makes no reference to a liquid.

If you meant a "flow of liquid" as opposed to a "flow in any fluid", you should have said so, since the whole issue is about whether "cavitation" applies solely to liquids or not.

I stand corrected.

Dan

ROFLMAO!!! Gasssp! Where'e the nitro? (glycerine, that is!)

In article , Six_O'Clock_High

That's because it didn't need to. Now go away.