You can look this one up. See FY 09 budget request, justification materials, US Air Force, Aircraft procurement-Vol. 2, page 71.
You’ll find on that page a detailed description for not one, but two potential mechanical problems that could cause a B-2A to crash.
Here’s a sampling (read highlighted text):
The problem is caused by the B-2A’s distorted engine inlets.
The distortion causes excessive wear on the stage 1 fan blades for the F118-GE-100 engines. Take that and an unplanned “foreign object damage event”, and, voila, your $1.1 billion bomber may experience a “catastrophic in-flight emergency”.
But there’s another problem. A loose fan blade also can spark an “uncontained titanium fire”. According to the same document, the titanium fire — whatever that is — may cause a “Class A event”, or what normal people call a “crash”.
The problem is listed in the budget justification documents because the USAF is buying repair blades this year to fix the problem. I’m sure it will be interesting for the investigators to find out whether the “Spirit of Kansas” had received the repairs before the crash, among other items of interest, of course.
Titanium can burn, but I’ve only seen (or was that caused)it happen during a turning operation on a lathe. There has to be a lot of surface area, good access to oxygen, and a strong ignition source.
It was kind of like magnesium, but much harder to ignite.
Josh,
So, from what you’re saying, a titanium fire would be easy to achieve with a loose compressor blade. Titanium blade rotating at thousands of RPM, rubbing on a compressor housing, with a huge volumetric airflow thanks to all the other blades on the compressor stages before and after…
George,
Yea, sure sounds plausible, but I’m no forensic scientist.
FOD — Foreign Object Damage — at those speeds, at those temperatures, is completely destructive. I’ve seen a single 2 cm piece of safety wire destroy an entire compressor stage.
You don’t need extraneous mechanical failures to take down a plane; a cotter key smashing a compressor, the compressor blasting shrapnel, shrapnel making important things smoke like a Roaring Twenties starlet, that’s all you need.
A friend of mine who makes custom titanium parts for motorcycle racers had a fairly nasty titanium fire ignited by a welding spark. No large surface area, no more oxygen required than plain old sea-level air. As I recall he couldn’t put it out, he just had to grab the parts with tongs and put them outside and let them burn themselves out…
Deferred maintenance ain’t cheap.
I don’t know about the cause of the fire, but the only way to put out a fire caused by the metals mentioned is to take away the oxygen. That is usually done by pouring sand on it, which obviously is not available in mid air.
DC2
BTW, it actually shocked me to learn that the transmissions of my series aircraft were made of magnesium. The reason being of course that while Mg is a bitch once it catches fire, it has a very high ignition temperature. For what it is worth.
Ver,
You are correct, it does take a high amount of heat to cause combustion. The wheels of most aircraft are also made of magnesium. And magnesium fires are special in that they cannot be put out with water. Either the source of fuel burns out or you take away the cxygen by smothering it.
Magnesium will burn straight through the decks on a ship.
With the exception of aluminum, it takes a lot of heat for a metal to combust. We learned the aluminum lesson on the USS Stark. That is why the DDG-51s are made of steel.
DC2
When you base the “Spirit of Kansas” in Missouri you should expect something like that!
All I want to know is did we get all of our money out of this billion dollar play thing that flys B2
It’s amazing to me that this is actually the first B-2 bomber to ever crash. Granted the number of B-2 Bombers on the market are much lower than say the Boeing 357, 747, or 757 but up until recently they had a 0% crash rating, where as each of those Boeings have crashed at least a dozen times.
One thing in engineering, whether it be buildings or software, stands true always; the more complicated the design the greater the chance for system failure. This is why Windows operating systems tend to crash more than Linux. Jets are getting increasingly more complex. Computers run the vast majority of the vehicle (Hopefully not using Windows as an operating system) while a person maintains about 20% of any of the controls.
This isn’t just for military mind you, this is for even commercial. The more complex something is the more areas there are to miss in preflight checks. The increased odds that something could go wrong in mid air (while it was possibly fine on the ground) or God forbid we pay attention to all the computers and forget to check the simple things on the vehicle like oh I don’t know the blades or the turbine engine.
The fact that a B-2 crashed isn’t amazing to me. What is amazing to me is that we don’t see more aircrafts falling out of the air on a regular basis. (I said all this unafraid to fly and having a love for just about all new technologies regardless of the fact that I don’t actually need it.)
heve you ever seen a chain saw burn.
the gasoline fire ignites the magnesium parts which ingite the aluminum parts which melt the steel parts.
when all is said and done there’s a little pile of white powder with a rusty lump in the middle.
thats funny airplanes have those ingrediants in them also: fuel, aluminum, magnesium, steel.
Hmmmmmmmmmm.
C
Any thread going to start on Hugo Chavez threatening war with Colombia? he wants to try out his new Su-27s. NOW THIS IS TAILOR MADE FOR OUR F-22s!!!! Now we’ll find out how they’ll perform against each other. Yesssss,bring it on!!!!!!
Both magnesium and aluminum are critical components of metal alloys which most aircraft today are made of to reduce weight and increase strength. Magnesium alloys tend to be more strong than aluminum and thus are used more extensively. (Remember those alloy wheels called Mags? What do you think those are made of?)
Magnesium fires burn very quickly and with extremely high temps. They can’t be put out with water. They need foam. They will usually consume their prey faster than anyone can put them out. That’s what makes them so dangerous.
THE B IN B2 stands Bomber not Boeing. Also there are fewer B2’s than commercial planes flying in the sky hence the different number of commercial plane crashes to military plane crashes. No less it it tragic.
THE B IN B2 stands Bomber not Boeing. Also there are fewer B2’s than commercial planes flying in the sky hence the different number of commercial plane crashes to military plane crashes. No less it it tragic.
I question the high ignition temps required to burn these 2 metals. I used to grind 1/4″ thick magnesium stamping dies using a 7″ grinder, collecting the dust in a bin behind the grinder. If I forgot to empty the bin before grinding steel or iron, one red hot piece of the ferrous material in the bin would ignite the magnesium dust. The red hot ferrous piece was probably about 800F, that’s not very hot in the world of burning metals. Cast iron will melt at 2300-2400F, steel melts slighty higher. The tip of a lit cigarette is about 800F, so I’m saying magnesium, in dust form, will ignite at 800F or slightly above.
When machining (turning) titanium pieces it’s standard procedure to have a fire extinguisher (at least one) within reach to attempt to dose the fire should it ignite. Cutting is done slowly to reduce the temps created as much as possible, to inhibit ignition. I agree that water is not the answer with burning metals, it may even cause an explosion. A sticky foam, for fires in the vertical position, would be best.
My first assumption on reading the words “titanium fire” go back to my days working at GE Aircraft Engines.
Part of the engine case (could be the area surrounding the fan, or compressor, or both…I don’t know the specifics of the F118 engine) is made from titanium. A loose blade can cause friction, and at the high rate of rotation can cause enough friction to actually ignite the titanium.
Titanium is similar to magnesium in that it burns, and once ignited burns hot and is difficult to extinguish. It isn’t easy to ignite titanium, but engine blade friction can do it (and has, F/A-18s have experienced the problem on rare occasion).
Once a titanium fire starts in an aircraft, there is little to do but get out ASAP. I don’t know of any aircraft that contains a system to extinguish a titanium fire in the engine area.
Gents, just sat on the plane with a B-2 crew chief who said the plane crashed due to pilot error: stalling on takeoff. He said the word inside his circle of B-2 maintainers is that it wasn’t a mechanical failure but rather an abrupt climb that the aircraft’s comps didn’t regulate enough. No other proof of that, but it’s a pretty reliable source.
The immediate cause does indeed appear to have been a stall and consequent loss of lift during takeoff. It’s still unclear if it was pilot error, i.e., yanking the stick back too far, or some sort of fcs problem. It is a known characteristic of the a/c that the cg is very far aft when the tanks are full for ferry flights (a/c normally doesn’t carry that much fuel on training and operational missions). talk about a bad day for that crew…
Speculation to fit the reports go this way:
Hydraulic failure in the Right side drag rudder control caused all four systems to that to failfrom the small resultant fire near the engine. The right drag rudders close, blown shut by the air stream. The now heavy drag on the left side causes a hard yaw to the left, the right wing being nearly straight to the air streem causes a hard pitch up and a sudden snap-roll to the left. All of this taking just a couple of seconds. Inverted the B-2 hits the ground level, upsidedown, a little to the left of the intended flight path. They need lockouts to prevent this on the surfaces and in the hydraulic systems.
G2,
I also worked at GE Aircraft Engines and I can attest to titanium fires. I was present when a bearing failure occurred on a different type engine and the compressor rub was enough to ignite the titanium. It was not a pretty sight. The aluminum cowling just melted away. Carbon dioxide finally put out the fire but it took a while. The floor of the test cell had little puddles of molten metal that had dripped down and resolidified.