Crashes in the News - Thread

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GcmsGuru

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There's a video of a NASA test of anti-misting kerosene which demonstrates, quite well, that crash and burn is very real.

A crash is going to generate a lot of heat, through friction, and metal rubbing against pavement, stones, or other pieces of metal will spark. It's not like throwing matches into a bucket; it's more like striking a spark in the spume from the gasoline equivalent of crashing ocean waves.
I'm familiar with this video and some years ago looked into it in a bit of detail. What is shows is the deliberate crash of a radio controlled B-707 for the purpose of supposedly testing how a "gelled" fuel system responds to a crash. The original plan for this experiment was to simply land the aircraft smoothly and let it slide through a number of obstacles which were planned to open up the wing tanks in order to test the fire supression/elimination of the gelled fuel supposedly on board.

As can be seen, the touchdown was anything but smooth and the supposedly gelled fuel easily caught fire...

In any case the gelled fuel was deemed to be useless and as such definitely not worth suggesting/ordering the airlines to install the gelled fuel system.

For what it is worth, it has been my belief for some years that the experiment was probably not conducted as stated using gelled jet fuel, but was probably conducted with Jet-A fuel which (if memory serves me correctly) was formulated with a bit of gasoline at the time. In other words I suspect that the test was designed to fail in order to save the airlines the $ of having to mod all their aircraft and completely revamp their fuel storage and delivery systems...
 

wktaylor

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During catastrophic ground collision, electrical arcing/sparking, engine-parts, plus other metal friction/sparking, is the primary ignition source when tanks rupture and spray/atomize/mist highly volatile AVGAS [or jet-fuel, etc].

Military helicopters have crashworthy tanks and hoses, self-sealing quick-disconnect plumbing connections, extra tough valves, and only short/isolated tubing runs to minimize fuel loss in a non-catastrophic crash... to minimize potential for a fuel-fed 'explosion/pyre' [survive the crash, burn-to-death in the post-crash fire].

NOTE. I have seen water-impact flash-fires that were quickly snuffed-out as the wreckage sank.

Some references You may find enlightening on aircraft mishap/accident investigations and investigative techniques.
AFP 127-1 VI US Air Force Guide to Mishap Investigation – Safety
AFP 127-1 VII Safety Investigative Techniques
AFP 127-1 Safety Investigation Workbook

AFAPL-TR-73-74 Fire and Explosion Manual for Aircraft Accident investigators
AFWAL-TR-85-2057 Aircraft Mishap Fire Pattern Investigation
WL-TR-95-4004 Aircraft Mishap Investigation Handbook for Electronic Hardware
WRDC-TR-90-4075 Failure Analysis Techniques for the Evaluation of Electrical and Electronic Components in Aircraft Accident Investigations

Aircraft Accident Investigation - 2nd edition [RH Wood and RW Sweginnis**]
ISBN 13: 9781892944177, ISBN 10: 1892944170

Air Accident Investigation 3rd Edition [D Owen]
ISBN-13: 978-0750944953, ISBN-10: 0750944951

ICAO Doc 9756-AN/965 Manual of Aircraft Accident and Incident Investigation Part III — Investigation
https://skybrary.aero/bookshelf/books/3708.pdf

** Sweginnis was one our instructors when I took the 2-week USAF Aircraft Mishap Investigation Course in 1984. I have 11-USAF Class A investigations, dozens of Class B investigations and who-knows-how-many Class C and HAP investigations over my 40-yr career.
 

Derswede

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Central North Carolina
Spent a couple of years in a job that in part involved blowing up fuel pumps. The typical service station fire is caused by static electricity. The cell phone warnings are mostly lawyer labels. The worst thing is a person who, on getting out of their vehicle during cold weather... avoids touching anything to prevent the static snap due to sliding out of a vinyl seat which will form a serious static charge on the person. The person then opens the (normally plastic) fuel cap, grabs the nozzle and starts pumping fuel. As the tank fills, an air/fuel vapor mix is being pushed out of the tank which is coming out right at someone's hands on the nozzle. If a spark occurs in that timeframe, poof, you have a fire. Most pumps now carry warnings to touch the pump or the vehicle to discharge any static charge. Amazingly simple to cause a fire in this manner.

Derswede
 

wktaylor

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Messages
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Midwest USA
Derswede... To expand on Your comment...

Synthetic clothing fabrics and very dry air create abundant static electrical build-up... will dissipate on contact with a metallic contact. These sparks have a lot of energy ... just like a spark-plug in a piston-gasoline engine.

I think the 'real concern' about cell-phone usage, while pumping fuel [gasoline/diesel], is the very-real and serious 'distraction factor'... that can have divert the driver's attention from the relatively 'simple... but dangerous... process of refueling a vehicle and crazy stuff that can 'happen' [**** happens]. And, of course, any fuel-spills that occur are a liability and a possible danger to the gas-station.

CAUTIONARY TALE...
Several years ago a USAF mechanic was drilling-out leaking blind bolts in the upper wing skin of an F-16 with open fuel access doors on a very hot [+90F] day in the ROK. He was kneeling on the upper wing skin grinding drill-starting-marks on the heads of bolts when he suddenly began screaming and his BDUs/T-shirt were on fire... and someone noted a weird heat-distortion in the air columns coming out o the access doors. His grinding shot red-hot sparks over the open tank... that was NOT fully de-puddled/purged... which ignited warm/rising jet-fuel/air vapors and the interior of the wing became an efficient fiery oven, with the access openings feeding air and the puddled fuel quickly evaporating as the fire heated the interior structure . Weirdly, there was no visible 'flame' just the heat distortion columns and the obvious panic/pain/fear of the mechanic on-fire [he was medevac'd to the USA for burn-treatment]. The hangar area where the jet was parked did not have Halon fire bottles... so mechanics improvised with powder-fire extinguishers... put-out the fire, but required a wing-change due to FE powder contamination inside the wing. I went to investigate the wing and determined that it was totally contaminated with extinguisher powder and that the interior finishes were 'scorched'. the wing had to be replaced. the contaminated wing sent to Ogden-ALC for final determination of repair or scrap.
 

wktaylor

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Similar video [movie] presentations made by USAF demonstrating flammability/explosiveness of JP-4 [~='gasoline with oil' (for lubricity)] Uhhhhhhggggggg. Thank god the USAF discontinued JP-4 [and all Avgas] and went to JP-8 and is now using mostly Jet-A+ special-additives. Static electricity, arcs/sparks from any-other source [wiring shorts, lightning, etc], sloshing fuel [aeration + static charge build-up, etc] made JP-4 and Avgas very dangerous.... mush less so , JP-8 and Jet-A.

NOTE. Some people believe the solution to explosion prevention in a crash is fill tank spaces with 'ballistic foam'... WRONG!!!! Ballistic foam minimizes/contains the effects of instantaneous ballistic impacts [battle sources, such as shrapnel, bullets, cannon-shells, etc], and minimize internal static discharges that could ignite fuel-air mixtures that are 'just-right' [not too-lean or too-rich]. HOWEVER, but in a crash scenario, with ripped-open fuel tanks [obviously not-crash-worthy] the ballistic foam helps the 'mist' the fuel thru the porous spongy matrix... making fire/explosions potential far worse.
 

Swampyankee

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There’s an entire specialty involved in preventing static electricity caused explosions in places like grain elevators, flour mills, and cotton mills. None of these evaporate, but finely divided powder has a huge ratio of surface area to volume, so it burns very, very fast.

It also generates it own static electricity. Frighteningly, so can finely divided mists of water or fuel.
 

BBerson

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Must be big sparks or fire to see it from that distance. I guess the aluminum scraping is what sets off the crash fires we see when fuel tanks are ruptured.
 

Hephaestus

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I'm no crash analysts, but I'd imagine it's ferrous metals that spark on pavement more than the non ferrous.
 
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