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#200744 - 04/22/10 03:15 PM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: unimogbert]
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
Originally Posted By: unimogbert
18:1 glide ratio is a number that comes to mind for jets. I've flown sailplanes with a much worse glide ratio.

I looked up glide ratios of passenger jets in the past and was surprised at the variability of answers. The 12-16:1 range comes up most frequently, but also some references as low as 3-4:1 (especially when flown "heavy") and also as high as 28:1 for an MD-80 on one website. Wow, really, 28:1?!

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#200747 - 04/22/10 03:48 PM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Arney]
Susan Offline
Geezer

Registered: 01/21/04
Posts: 5163
Loc: W. WA
+1 on the glidability of commercial aircraft. I can remember two incidents (besides the one into the Hudson) without looking them up.

There was the Air Canada aircraft that ran out of fuel (fueling error when metric replaced gallons) at cruising altitude, and ended up doing a glider landing at an unused air force base, where a bunch of people were all watching drag races with their backs to the silent aircraft. One kid turned his head in time to clear the runway.

The other was a China Air flight that was coming into (I think) San Jose, CA. The last I heard, the fuel lines had frozen. They were a glider for the ten minutes it took for the lower altitude and warmer temps to thaw the lines so the crew could get the engines started again. IIRC, when they got the engines restarted they were only 1500' off the ground.

Both of these were in the 80s.

Sue

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#200749 - 04/22/10 04:04 PM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Arney]
Am_Fear_Liath_Mor Offline
Carpal Tunnel

Registered: 08/03/07
Posts: 3078

Quote:
I looked up glide ratios of passenger jets in the past and was surprised at the variability of answers. The 12-16:1 range comes up most frequently, but also some references as low as 3-4:1 (especially when flown "heavy") and also as high as 28:1 for an MD-80 on one website. Wow, really, 28:1?!


As with anything the lift to drag ratio is a variable for any aircraft, which depends on the Altitude, glide speed, payload etc.

The LD ratio is proportional to the square root of the wing aspect ratio divided by the zero lift drag coefficient. So just by looking at an aircraft such as the Boeing dreamliner or DH Comet 4, they will have an excellent LD ratio because of high aspect ratio wing. Aspect ratio is equal to the square of the wing span divided by the wing planform area. So aircraft with long narrow wings will have the greatest LD or glide ratio.

Concorde for example will have a glide ratio of between 4 and 7 depending on its speed and altitude due to the supersonic capable small aspect wing ratio and large overall wing area making it the fastest jet aircraft in the world including all in service types including all civilian or military types.



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#200750 - 04/22/10 04:14 PM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Susan]
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
Originally Posted By: Susan
One kid turned his head in time to clear the runway.

Well, there you go! Another example of why we need crash whistles installed on all planes (a reference to another recent thread)! LOL

Of course, they would need to be made loud enough to be heard over the sound of cars drag racing to be truly effective.

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#200769 - 04/22/10 11:12 PM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Arney]
Art_in_FL Offline
Pooh-Bah

Registered: 09/01/07
Posts: 2432
The ups and down of closing airspace because of ash:
http://scienceblogs.com/eruptions/2010/04/eyjafjallajokull_flight_cancel.php


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#200782 - 04/23/10 06:20 AM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Art_in_FL]
MostlyHarmless Offline
Old Hand

Registered: 06/03/09
Posts: 982
Loc: Norway
Yup, clearly a damned if you do -- damned if you don't situation for aviation authorities.

The ash, it turns out, is actually the smoking remains of the crashed Icelandic economy...

“I’m stuck in Europe because of an Icelandic ash-hole!”


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#200783 - 04/23/10 06:45 AM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Art_in_FL]
James_Van_Artsdalen Offline
Addict

Registered: 09/13/07
Posts: 449
Loc: Texas
It was, and is, well known that volcano ash plumes can damage airplanes in flight to the point of immediate failure. In the (very) few cases of engine shutdown the engines were restarted before impact but there's no reason to believe that was anything other than random chance.

It was known by Sunday that *this* volcanic ash plume could damage airplanes. The KLM exec who flew on a test flight and proclaimed "I didn't crash!" neglected to mention the aircraft that did sustain engine damage, and that KLM had not taken apart their engines to see if they had suffered the kind of damage this ash plume was known to cause.

The problem is that nobody has a map of where the debris will go. Vertical wind sheer means different altitudes have different danger areas, and I don't know if there is any way to detect it remotely. Iceland isn't going anywhere and as long as the Jet Stream is in the region, this can happen - time to fund some research on volcanic debris plume composition and dispersal.

Overall I think the EU authorities made the right decisions for the right reasons, and the airlines are being dishonest and deceptive in their arguments.

Time to repack that travel bag with underwear and socks that can be washed in a sink and dry overnight... I'd not sure there is a "dries overnight" shirt or pants? A week of prescriptions may be to little... ...time to look at that bag again.

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#200878 - 04/24/10 02:04 AM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Art_in_FL]
Dagny Offline
Pooh-Bah

Registered: 11/25/08
Posts: 1916
Loc: Washington, DC
Fascinating lengthy article in the April 24 Wall Street Journal on how the 1815 eruption of the Tambora volcano in Indonesia caused global cooling that reverberated around the world in ways big and small. The article also compares it to the current Iceland eruption, Krakatoa, Mt. St. Helens and others.

http://online.wsj.com/article/SB10001424...IDDLESecondNews

* APRIL 24, 2010

Eruptions and Disruptions

Iceland's volcano pales before giants that may have sped U.S. settlers and led to 'Frankenstein'



"...crop failures dotted the northern hemisphere—rice failed in parts of China, wheat and corn in Europe, potatoes in Ireland (where it rained nonstop for eight weeks and triggered a typhus epidemic that killed 65,000 and spread to England and Europe). At Lake Geneva in Switzerland, vacationers from England sat out gloomy June storms reading ghost stories and composing their own. Lord Byron wrote a narrative poem, "Darkness," in which there was no sun, "no day." His personal physician, Dr. John Polidori, wrote "The Vampyre," and Mary Shelley began "Frankenstein." Famine spread across Switzerland. Food riots and insurrections swept France, which had already been caught up in the chaos following Napoleon's 1815 defeat at Waterloo.

"In New England, 1816 was called "the year without a summer" because there were crop-killing frosts every month, including the normally frost-free months of summer, across the region.

"It snowed in Virginia in June and again on the Fourth of July.
"


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#200880 - 04/24/10 02:07 AM Re: UK Airspace Closed - Volcanic Ash Disaster [Re: Dagny]
Dagny Offline
Pooh-Bah

Registered: 11/25/08
Posts: 1916
Loc: Washington, DC
And more pics of the Icelend volcano and the northern lights, which the ash is making more spectacular than usual.

Incredibly beautiful color.

The link is enormous so know that the slideshow can be found in the article I linked to in the previous post.


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