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Is there any precedent or can the debris pattern positively confirm the cause of a crash due to:
If a particular flight path is necessary to facilitate the question, assume the 1988 Airbus flight.
No, not an explosion, just break-up.
The debris field can prove if some parts of the aircraft broke off in the air, before the main impact. However the aircraft can break up also if the pressure vessel fails, if intense fire compromises the structural integrity, or due to mid-air collision.
And on the other hand, an explosion can make the plane uncontrollable without breaking off any large parts e.g. if it severes the hydraulic lines (which can also start fire as the hydraulic fluid is flammable).
An explosion can only be proven by collecting pieces of the wreckage and looking for traces of spalling, shrapnel damage and traces of an explosive.
Yes, especially if the explosion or breakup occurred at altitude. In this case the pieces of the plane will be broadly distributed across the terrain and pieces with any aerodynamic qualities (big, flat chunks) will fall a significant distance from dense pieces of machinery (engines, pumps, motors).
For example, an RV-type plane flying out of an airport not far from my home crashed into an open field; one of its wings came to earth far from the crater, indicating that the wing came off not during the impact but while the plane was still in the air.
Furthermore, pieces of the shattered bubble canopy were found in a cluster far from the crater rather than inside the cockpit, where they would be if the canopy shattered on impact. This allowed the investigators to conclude that the wing spar folded at its join with the fuselage, flipped up and struck the canopy, smashing it to pieces and then separated from the fuselage while the plane was a thousand feet or so above the ground.
Explosions leave blast soot on the pieces of the plane and impact damage from pieces of shrapnel thrown by the exploding munition. A missile strike on an engine will blow it free of the wing at altitude and a bomb in the fuselage will show localized blast soot and tearing patterns in the fuselage structure which can be deduced from the wreckage with a lot of hard work.
Yes and no. I would not use the term "confirm". When a crash is investigated all available evidence is analyzed, including the debris pattern. You would be amazed at how detailed the analysis can be. The size and shape of fragments are analyzed. The way the edges of the fragment deform is analyzed. Even the position of the edge deformities is analyzed, as this may provide a vector pointing directly toward the center of the explosive forces. From multiple such fragments triangulation can be used which can pinpoint exactly, or at least roughly, where the center of mass of the explosion was. Blast pressures at various points can be estimated, and these patterns may be consistent with some types of explosives and inconsistent with others. Chemical trace analysis of the fragment can detect traces of most explosives. Even audio from the CVR can be analyzed to help discern the type of explosion.
A laundry list of scenarios is then analyzed: is all the data consistent with a mid-air explosion; is it consistent with an engine fire leading somehow to a larger conflagration; is it consistent with an otherwise intact airplane flying in a controlled manner into terrain. This analysis produces a degree of confidence as to whether or not that scenario is consistent with the evidence. Oftentimes sophisticated statistical models are employed to quantify these probabilities. The pattern of the debris field is likely to be one such component. However, sometimes there are multiple scenarios that can well explain a certain component of the evidence. That's why all the evidence is taken together. It like a criminal investigation where a list of suspects is whittled down using each piece of evidence to exclude some suspects until finally only one suspect remains, consistent with all the evidence.
The analysis is more likely to be definitive when all of the plane can be recovered.
Of course sometimes it's pretty easy. If you find missile debris along with the plane debris, and missile fragments embedded in a section of the plane, you can probably tentatively conclude it was shot down by a missile. In a criminal investigation this would be called a "smoking gun".
Confirm, no. Give a solid preliminary estimate, yes. It has been done multiple times.
Just mapping the debris field will give preliminary answers as to the following questions:
Every piece of debris found will be taken into evidence and analyzed. This will produce additional conclusive information:
It takes some time to go from theories to most likely cause to conclusive proof, but generally the broad scope of the causes (missile hit, internal malfunction, CFIT, bomb on board) can be ranked into the most and the least likely ones with just the debris pattern.
Confirming anything generally means exploring and assessing every plausible hypothesis. It will usually take 1-3 years before the final report that is the only positive confirmation. That said, the most likely theory is usually established in just a couple months, and the rest of the time is spent evaluating it and looking for more alternatives.
an internal explosion OR
To some degree, yes.
Consider the case of Turkish Airlines Flight 981. In this case the rear cargo door blew off. It was immediately obvious what happened because they found the door, bits of the floor, and a row (or more?) of seats immediately above the door miles from the crash site. Generally, if you find some selection of parts at a distance from the rest, you can be pretty sure the problem started around there.
In the case of an internal explosion, you would expect to see portions of the fuselage or frame would be separated early. For instance, American Airlines Flight 444 led to parts of the airframe being recovered. In this case, the initial set of parts are fragmented into smaller parts, as opposed to complete parts like a cargo door. As the plane breaks up larger parts will shed, but tracking back will reveal the initial type of debris.
Alternately, you may never find those parts, leaving a clear hole in the parts inventory. This was the case for Pan Am 103, where the hole caused by the bomb could be easily seen in the reconstruction.
