For want of one "line replaceable unit", a $73m drone was lost

We don't cover military drones here, but I'll make an exception for this fascinating accident report. We've all lost drones due to technical malfunctions, so we can sympathize with this. At least ours didn't cost $73 million.

From Defense Tech:

On August 11, 2011 Air Force ground controllers lost contact with one of the military’s most advanced — and expensive — drones, an EQ-4B Global Hawk as the jet flew high over Eastern Afghanistan.

Nine hours into an otherwise smooth communications relay mission using the Battlefield Airborne Communications Node (BACN), the plane was cruising at 51,000-feet above sea level 105 nautical miles northwest of Kandahar, Afghanistan — close to the border with Pakistan, in fact, the few news reports that emerged of the crash claim the jet actually went down inside Pakistan —   when a pilot from the 12th Reconnaissance Squadron out of Beale Air Force Base in California “lost all links with the payload,” according to a copy of the Air Force’s report on the incident that the service sent to DT. The pilot did everything he could to reestablish communications with the mammoth drone, but 25 seconds after losing communications, the plane began a high-speed fall to Earth. If plummeted so fast that “both wings and at least one of the lower aft fuselage fairings” were ripped off the jet as it fell. Three minutes later, the Global Hawk crashed into “remote, desert terrain approximately 4 nm from its last reported position and was destroyed,” reads the Air Force’s report. “the estimated loss is valued at 72.8 million.”

So, what caused this?

A single part — or Line Replaceable Unit, as the report calls it — came undone, interrupting the flow of electricity to the plane’s aileron and spoiler actuators — the tiny motors that control the movements of an aircraft’s flight control surfaces you know, the moving parts of the wings that control whether the plane climbs, dives, banks, rolls, etc. As expected, this disconnection rendered “the aircraft uncontrollable.”

(Critical parts that lose it like this one are called single points of failure, meaning that if these sometimes tiny and seemingly insignificant parts fail, the entire weapon system fails. Naturally, military equipment makers try o identify these and do all they can to ensure they won’t fail.)

Why did this single part become disconnected? “The board president also found, by a preponderance of the evidence, that the LRU [the critical part] installation methods were a contributing factor in the mishap,” reads the a summary of the report. Apparently, the screws holding the part in place weren’t tight enough and probably shook loose due to typical flight vibrations.

One other thing to note, the jet’s “avionics were not recovered from the crash site.” Let’s hope they were destroyed in the crash and the subsequent bombing of the wreckage by Air Force bombers and not scooped up by someone who could sell them to the Russians or Chinese.

Read the full reporthere:  

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Comment by Ian forbes on March 7, 2012 at 10:51pm

In gregs note, I say a little prayer for those in our military, I have more than my fair share of friends who are (and were lost) in the military.  I may make light of this topic, it would piss me off to know that we lost anyone on the ground because someone missed that memo, or was too lazy to put some $2.00 loctite on a few screws...  That's all I'm saying....


Chrisytopher, I unfortunately meant avg cost of life as interpreted by insurance/economic statistics, be it military or otherwise.  All warfare comes down to best use of resources, be it human or financeial.  Some would say we won the cold war this way, by crashing their economy through military over budgeting.

Ellisons comment is actually interesting, if two countries engage in strictly drone warefare, and no lives were lost on either side, it would be a pure economic and technological war.  Whoever best manages the development and costs wins...  Its a fun thought experiment. 

This in no way negates the value of anyones life, mine yours, or our troops on the ground.  Come home safely gentlmen.  Crash and Burn...

Comment by Ian forbes on March 7, 2012 at 11:01pm


Miltary Drone == $73 million

4 screws at hardware store = $3.00

1 Tube of locktite blue  -- $2.64

Getting your drone TROOPS home in one piece -- Priceless

Comment by Brent on March 7, 2012 at 11:39pm

Every A/C I have worked on has safety wire or cotter pins on the screws, nuts and cannon plugs securing critical components? A simple low tech solution that has worked since the Wright bros.

Comment by Chuck on March 7, 2012 at 11:48pm

Aircraft (manned anyway) don't rely on Locktite for anything critical. Flight control fastners generally have cotter pins or safety wire. But this apparently was a fastner for an electrical connection. Mil spec connectors have locking mechanisms. Older gear used safety wire. Even inside the boxes the connectors are designed to not come loose. These things might be using equipment that would never meet FAA specs and since they are not governed by these standards corners were cut. No problem. It landed in an uninhabited area in somebody else's country. We will never have drones like this (or cheaper) flying over OUR heads.

Comment by Jack Crossfire on March 8, 2012 at 12:18am

Another crash to make the FAA wait a few more years before starting to draft rules.  The mourning began when the gun replaced the sword & people could rely on unmanned bullets.  If we still had to use swords, there wouldn't be any war.

3D Robotics
Comment by Alan Sanchez on March 8, 2012 at 1:15am
My girlfriend keeps telling me to put my name and contact info on my drones ... Maybe I should start doing it ಠ_ಠ

Comment by Gary Mortimer on March 8, 2012 at 2:24am

Chuck has it right, be prepared for ASTM F-38 I know I know you are all getting bored. Military contractors are going to grand father the small stuff in for Police use based on the blanket permissions they enjoyed. We shall see how that goes. What's ok on the battlefield might not be for the baseball field. Stop pricing your UAS with anything that is not produced in a factory that can give you manufacture date time and unit number.....

Comment by Krzysztof Bosak on March 8, 2012 at 3:10am

@Ian forbes  "4 screws at hardware store = $3.00 1 Tube of loctite blue  -- $2.64 {some random bullshit} - priceless"

blah blah be serious man. Each screw was kosher milgrade towards 50USD range. The loctite was also from a special batch, if used at this point. If not, it would had crashed a few times already, simply because a screw from one unsupervised china factory might not be 100% as normalised as you would expect, in the nearest US hardware store. That somebody forgot to use a screwdriver properly? It was 70USD/yr airtech engie failure, not 3USD screw.

Comment by Ian forbes on March 8, 2012 at 7:29am

@Bosak take a joke man! Do you really think I am serious about the blue loctite (the loctite comment is what bothered you, seriously?)?  And the military does use loctite blue, Ive seen the spec and bid requests.  Maybe they forgot "lefty loosy, righty tighty"?  and a $3.00 screw from a us manufacturer would cost $50.00 by the time it got through the contractor channels and paid for by taxpayers. Remember the lowest bidder build your weapon...

  None of us even know what it actually was that downed the UAV, and I don't much believe military reports on such things.  Maybe  the GPS signal was hacked like the other downed drone in january (once again this is called sarcasm, how the hell do you hack a gps sat signal? Not likely).   

Comment by Ellison Chan on March 8, 2012 at 8:25am

Well, the Taliban should be be able to operate freely the next few days.  The big giant solar flare has probably grounded all UAVs due to either GPS satellite shutdowns.


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