So the Iranians got to the drone that crashed before we could get in there and keep sensitive, high-tech equipment out of their hands. Since drones are (often) operated remotely, why can’t the sensitive equipment be set up so it could be destroyed by remote control?
Seems like it would forestall potential problems. Then again, if it were that simple, we’d already be doing it, right?
It’s all about design tradeoffs.
Somebody decided that as between carrying X pounds of self-destruct gear & running the Y% risk of it going off at the wrong time (including while your men are refueling & maintaining the airplane) versus carrying X pounds more fuel & munitions & sensors but having Z% risk of stuff falling into enemy hands, they chose door #2.
It’s not that self-destruct couldn’t be accomplished. It’s that it wasn’t deemed worth the other things you have to give up to get it.
Whether that was a wise decision is a separate question.
And “self destruct” isn’t like what you see in Science Fiction movies, where the giant starship is reduced to a cloud of hot gas. A real-life self destruct is just a bomb strapped inside the device, and if you press the button the bomb goes off. A drone that fails is going to crash into the ground, how much more destroyed is it going to be if a bomb goes off inside it? A bomb isn’t going to turn a drone into tiny splinters, it’s just going to blow a hole in the drone, and then the drone crashes.
Or perhaps when you take it apart. 
Seems like the electronics could be manufactured in such a way, as to be incomprehensible to anyone who should happen to find it (fully embedded in ceramic?) and the software encrypted/formatted in such a way as to make the collected data inaccessible. That’s what I’d do if someone asked me.
Besides, only supervillains include a self-destruct button in their creations.
According to this article:
All planes already have a fairly effective self-destruct feature, called the ground. I wonder what happens if one of these drones suffers a complete communication failure or terminal error? It might try to navigate back to a known location, or it might even crash itself in some circumstances.
Another thing to consider is what is causing us to lose the drone. They aren’t going to crash unless there’s an equipment malfunction, outside interference like hostile fire, or loss of signal. And any all of those cases there’s a good chance that pushing your self destruct button isn’t going to work.
Also, there’s a huge added risk to the personnel handling the drone. What if it lands too hard? What if the button gets bumped while we have our guys fueling it?
There’s just too much risk to justify the small chance of any reward.
That, and the payload issues mentioned upthread.
Isn’t it unwise to send an aircraft carrying explosives into another country, and to possibly detonate those explosives? Could that be seen as an act of war?
The information held in the drone’s computers is no doubt set to automatically erase in the event of a catastrophe (or in the event of third parties trying to extract said info).
Destroying the airframe so as to effectively forestall reverse engineering is next to impossible. Leave behind a square inch of skin, and that’s enough for the bad guys to analyze the radar-absorbing materials; leave behind an intact panel, and that’s enough for them to start assessing radar-deflecting geometries. The amount of explosive required (and its attendant cost, safety, and performance ramifications) in order to truly obliterate the airframe makes this an unattractive option.
Depending on what you needed destroyed, a shotgun shell or a blasting cap would both be pretty stable, removable, easily worked on and replaced, they would also be light and effective. You don’t need 5 lbs of C4.
If you just want to destroy the computer, then sure. Make sure to scrag the hard drive, if you have one. I recall that the spy-plane that was captured by the Chinese had a destruct mechanism for the computer, which consisted of a hammer.
But making the whole plane explode like they do in the movies is impossible. Even a system that sets the fuel tanks on fire won’t make the plane explode, because you’d need an oxidizer for the fuel. Those big explosions you see in the movies are very tricky to create because you need to mix the fuel with air.
You could make the skin/airframe out of a lightweight, rigid explosive with detonation requirements like those of C4, or perhapse requiring a stiff electrical jolt. It wouldn’t have to be a powerful explosive, just something that vaporizes on command.
But this isn’t some handheld model airplane. According to Aviation Week, this drone appears to have a wingspan of about 65 feet. It also has a rather fat body, and it seems to me that there is probably a shitload of complicated and secret technology in that cavity. I’m not sure a shotgun shell or a blasting cap are going to do the job.
So maybe there was a self-destruct feature–at least for the most sensitive equipment.
But it’s secret!
You’re whoosing us, right?
So is firing hellfire missiles at folks on the ground.
Why not just make the whole plane out of the stuff they make the black box out of?
If you have a candidate lightweight, rigid explosive material they could build an airframe out of, I’d like to hear what it is. Note that we’re talking “lightweight” and “rigid” in the same ballpark as steel and aluminum.
Supposedly, diplomatic pouches destroy their contents if they aren’t opened correctly. At least that’s what the spy novels tell us. 
I would think a vial of HCL would be very useful in destroying sensitive chips in a drone. A electronic lock could trigger something to crack the vial if the wrong security code is entered multiple times.
Hey, I’m an ideas guy, not a scientist. Wave a $40 million bounty in front of the Dupont execs and I’m sure their boys could whip up something involving a molecular C4-esque fiber encased in a carbon nanotube, spun into filaments, woven into a fabric and bonded with a whipped resin slightly denser than air at sea level.
Or something.
It seems to me that what you would want is something like thermite, not an explosive. Explosions leave a lot behind that can be reconstructed; thermite reduces material to slag, not fragments.
And running into the ground generally won’t do* that*, unless it’s molten lava. 