Least Risk Bomb Location

This fascinating tidbit is from Aviation Week and Space Technology (April 9, 2007, p. 21), in David Bond's "Washington Outlook" column (unfortunately, not online).

Need to Know

Security and society's litigious bent combine to make airlines unsuited for figuring out the best place to put a suspected explosive device discovered during a flight, AirTran Airways tells the FAA (Federal Aviation Administration). Commenting on a proposed rule that would require, among other things, designation of a "least risk bomb location" (LRBL) -- the place on an aircraft where a bomb would do the least damage if it exploded -- AirTran engineering director Rick Shideler says it's hard for airlines to get aircraft design information related to such a location because of agreements between manufacturers and the Homeland Security Department. The carrier got LRBL information for its 717s and 737s from Boeing but can't find out why the locations were chosen, "or even who specifically picked them," because of liability laws.

I'd never heard of an LRBL before, but the FAA has public proposed guidelines on them. Apparently flight crews are trained to stash suspicious objects there.

But liability seems to be getting in the way of security and common sense here. It seems reasonable that an airline's engineering director should be allowed to understand the technical reasoning behind the choice of LRBL, and maybe even give the manufacturer feedback on it.

EDITED TO ADD (4/21): Comment (below) from a pilot: The designation of a "least risk bomb location" is nothing new. All planes have a designated area where potentially dangerous packages should be placed. Usually it's in the back, adjacent to a door. There are a slew of procedures to be followed if an explosive device is found on board: depressurizing the plane, moving the item to the LRBL, and bracing/smothering it with luggage and other dense materials so that the force of the blast is directed outward, through the door.

Posted on April 20, 2007 at 1:39 PM • 34 Comments

Comments

RoyApril 20, 2007 1:57 PM

This is rich.

DHS is against giving out the one place a bomb would be least effective, since that would increase the knowledge of terrorist plotters, letting them know the worst place for their bomb to be put.

Designate the safest 1% of the volume, and that reduces the enemy's ignorance from 100% to 99%. That's a whopping 0.044 dB improvement.

PhillipApril 20, 2007 2:01 PM

I may be looking at something and making it too simple but wouldn't the "LRBL" be somewhere not on the plane? Can't we design planes so a reasonably sized object can be ejected through some kind of air lock hatch? Assuming you aren't flying over a densely populated area....THAT would be the "LRBL".

Bruce SchneierApril 20, 2007 2:13 PM

"I may be looking at something and making it too simple but wouldn't the 'LRBL' be somewhere not on the plane? Can't we design planes so a reasonably sized object can be ejected through some kind of air lock hatch? Assuming you aren't flying over a densely populated area....THAT would be the 'LRBL.'"

At a guess, the ejection system would be far riskier to include in the aircraft design than the residual risk of a bomb exploding.

When was the last time a flight attendant had to stash an actual bomb on the plane? A fake bomb? Has this ever actually happend? (My guess is that it has, although very rarely.)

dpawtowsApril 20, 2007 3:13 PM

Also on the subject of ejection: The vast majority of objects stashed in such location will turn out to be false alarms. Do we want to be randomly bombing the landscape with misplaced cellphones?

eBayesianApril 20, 2007 4:10 PM

Every novice statistician knows they should carry a bomb deliberately. The chances of TWO bombs being on the plane are tiny.

John KelseyApril 20, 2007 4:24 PM

I've got this image of some kind of game-theoretic response here....

Terrorist: (stands and produces hand grenade) "Everyone stay where you are, or I will blow this plane up for Allah."

Counter-terrorist: (calculates payoff matrix, rolls dice to decide strategy, stands, produces hand grenade, and pulls out pin) "No, *I* will blow this plane up."

ARMApril 20, 2007 4:57 PM

While the idea of a designated "least risk bomb location" seems pretty good, I'm curious as to how such a thing would work, and under what circumstances it would be used.

It would have to be pretty easily accessable, so that a flight crew lacking in EOD training could get the thing in there easily. And wouldn't also need some way of securing the device? It seems to me that they'd almost have to have been designed into the plane from the get-go.

FooDooHackedYouApril 20, 2007 5:25 PM

Interesting... So, if attackers can research the least locations then they can do what to the others? Seems risky to make this information public.

VTBApril 20, 2007 6:15 PM

Of course, if the criteria for picking a LRBL were public, then those criteria would also be useful to an attacker for picking a MRBL, would they not?

johnsApril 20, 2007 6:15 PM

Isn't the cockpit door hardened on all commercial airliners now? Seems like the logical place would be behind it.

roenigkApril 20, 2007 6:28 PM

A google of that phrase find s "line training manuals".

"3. What is the least risk bomb location on the MD90 aircraft?

- The right forward service door."

Since every flight crew for every airline in the world will have to know this, one couldn't really believe a terrorist would not know it as well.

Ian MasonApril 20, 2007 6:31 PM

Several people have made the assumption that knowing the least harmful place for a bomb would offer an attacker some useful information. Aside from the fact that this offers a small, probably tiny, reduction in the set of 'places to stick a bomb', any half decent undergraduate mechanical engineer could look at few photos of a plane and tell you where to stick a bomb to cause a catastrophic structural failure. Moreover there isn't one suitable place there are many.

Christoph ZurniedenApril 20, 2007 8:08 PM

Is it really a good idea to define a place, where one should store something that might be a bomb?
There's probably only one LRBL, maybe two or three, depending on the type of the aircraft, but as Ian Mason pointed out: there are way more places to place a bomb to cause strucural damage.
So, if someone finds a device and calls it a bomb because it has the letters "bmob" written on it, the probability that it lies at the LRBL is very low even if you have several of it. The number of MRBLs will outnumber them by several magnitudes.
That means, that it has to be moved. I don't think it is a good idea to move something you think might be a bomb. The bombsquad does it from time to time, if blowing it up might do to much damage to something very expensive in the neighbourhood. But they put that bomb in a small vault where it can explode inside and all you get is a bang and a small puff of smoke---they don't lean it at the door of a flying plane and hope for the best.

There might be situations where the knowledge of a LRBL is usefull, but I doubt it's with a bomb.

CZ

MegaZoneApril 20, 2007 8:34 PM

CZ - An aircraft is different from a bomb in a building, etc. You can't evacuate a plane in flight. And if there is a timer, or the belief that it will detonate, it is better to move it to a LRBL than leaving it somewhere where it will do a lot of damage and bring the plane down. Most bombs brought on board a plane have been carried, or in some way portable, and not tamper resistant because that would interfere with the bomber getting it in place in the first place. It has to be something that can get past security and be smuggled - and not go off when they don't want it to, such as on takeoff or in turbulence.

billswiftApril 21, 2007 5:52 AM

""but can't find out why the locations were chosen, "or even who specifically picked them," because of liability laws.""

The problem isn't finding where the locations are; it is the airlines want to know **why** they are the LRBL and **who chose** those locations, to protect themselves in the event of.

Christoph ZurniedenApril 21, 2007 9:02 AM

@MegaZone
I guess you asume too much here.
At first: the LRBL is not a safe place do detonate a bomb of any size. It may be safe for a small leftover from the 4th of July, but not for anything significantly larger. It only reduces the change that the bomb causes catastrophic failure of the plane's structure. I am not an aviation-engineer but I think that that place reduces the risk of a fatal end only for some points, maybe from 99% to 98%, which also depends heavily on the size of the bomb.
You also cannot asume anything about the bomb:
--The thing you found and called a bomb may or may not be a bomb

It may fro example be a packet that belongs to Berthold Mob, who writes his name on all of his packets and that's why it has "bmob" written on it.

-- it may or may not explode even if it's a bomb

The last large terroristic attack here in germany failed because the terrorists were too dumb to build a simple bomb.

-- it may or may not be strong enough to cause fatal damage to the plane where it is placed

Even the aformentioned firecracker is able to cause a fatal damage if it is placed correctly but there is of course a upper limit. I don't know how much exactly but I'm quite sure that 2 kilo C4 will wreck the plane no mater where you place it.

> and it may or may not have a device, that triggers the bomb when it is moved.

You assume something complicated here, but that's very rarely the case. If you move a handgrenade that has it's ring attached to the ground with some thin and nearly invisible thread like a fishing line you have a problem if you are for example in a flying plane.
If the normal procedure is, that anything that somebody called a bomb will be moved to the LRBL the chance is very high, that it will be moved. Attaching a fishing line is way simpler than building a timer and you can safely trigger the bomb by just calling the airline.

To make my point more clear: it's not the LRBL in and of itself but the procedure. The LRBL alone, especially if the exact place is kept secret (time may matter) can be called neutral, but only to avoid the more fitting expression "useless". So what's the exact procedure if somebody finds something and calls it a bomb?

An LRBL makes sense when it is really a safe place to detonate a bomb, like a box padded with kevlar with the lid directed to a place of the plane where ist is more or less safe to blast a hole into. Even better if you can move the box itself to upend it over the suspicious packet, makes five directions a bit safer. Main disadvantage of course is the fixed size of the box.

But there are a lot of things that are not bombs but are to dangerous to transport them anywhere in a plane and are found only when it is to late to store them outside of the plane, so a LRBL is definitly not useless for such things if the pace is public and carefully marked as such (as I said above: time may matter). But it is useless as a secret place for things that might be bombs and have a procedure in place that all such things have to be moved to that place. That means too, that you can smuggle several small bombs onboard (be carefull to write "contains bomb" in large bright letters on it and don't forget to call the airline) which will be joined at one place by the personnel onboard.

But the publication, that there are LRBLs determined and try to give you the impression that they are safe to store bombs is pure and utter security theater. Depending on the procedure in place it is also dangerous.

CZ

A PilotApril 21, 2007 9:50 AM

The designation of a "least risk bomb location" is nothing new. All planes have a designated area where potentially dangerous packages should be placed. Usually it's in the back, adjacent to a door. There are a slew of procedures to be followed if an explosive device is found on board: depressurizing the plane, moving the item to the LRBL, and bracing/smothering it with luggage and other dense materials so that the force of the blast is directed outward, through the door.

Gregg GroffApril 21, 2007 10:06 AM

Least risk bomb location? That's a good one.
It is amazing what nonsense people will buy into for the illusion of security and safety. It has been proven how ineffective airport security has been time and time again, yet air travelers still submit to it to calm their own fears.
Now the concept that you could find a bomb and move it to a safe location within the plane sounds like pure Hollywood to me.

JoeApril 22, 2007 4:38 PM

Perhaps I'm just missing something here, but why not just have everyone strap in, depressurize the cabin, open the door and toss it out?

TomApril 22, 2007 6:42 PM

"Of course, if the criteria for picking a LRBL were public, then those criteria would also be useful to an attacker for picking a MRBL, would they not?"

Security through obscurity is a bad idea in computer systems, and probably in this case too...

another bruceApril 23, 2007 12:12 AM

i've heard of brown ice coming down from the sky, just put the bomb in the same place the brown ice comes from and jettison it.

AJ FinchApril 23, 2007 6:50 AM

Designating a "Least Risk" location / procedure for use in an airborne aircraft is not security theatre. It may or may not be effective, but it is certainly not theatre.

Imagine being the captain of an airliner where a possible bomb has just been discovered. What would you do? You must assume that: you cannot jettison it, you have no handy kevlar boxes, you have no local bomb-disposal expert.

Preparing for a very bad (an unlikely) situation in a case where you have very little room for manouevre is not going to yield stunningly wonderful solutions, so don't dis the airlines for making the best of a bad job. At least they're trying to do the Right Thing.

I suspect that the strategy of using a LRBL has been driven by aircrew. These are the people whose lives are on the line... unlike the security guards groundside who are telling you to toss your drinking water.

khaled habibApril 23, 2007 7:18 AM

During the last few weeks i was searching to gain information might assist me for my draft concerning security and security in air .LRBL was very interesting positive ant-terror procedures should implemented for all aircraft. What made me amazing is the fact of no aircraft manufactures think in away to have the potential bomb eject from the plan during operation, which is very high-tech but worthy!! Wish to provide us at lately designed methods concerning this which is very important for allllll .and wish to not be utilizes as well

MarkApril 23, 2007 7:57 AM

"The designation of a "least risk bomb location" is nothing new. All planes have a designated area where potentially dangerous packages should be placed. Usually it's in the back, adjacent to a door."

I'm not sure if this is the best place for a bomb. Since the last thing you want is something solid heading in the direction of the tail.
On many airliners an explosion in the passenger cabin is less dangerous than one in the cargo hold. Because of the way loads are carried in flight. Exceptions would be aircraft with a high mounted wing, such as the 146.

Stephan SamuelApril 23, 2007 10:13 AM

LRBL works on the assumption that all bombs will be found before detonation. I've not carefully studied aircraft terrorism history, but I believe most previous cases went off before detection.

If you publish the LRBL, potential terrorists know one place they shouldn't put a bomb. If you don't publish it, they need to have someone "on staff" with enough knowledge of where to put the bomb.

What's going on here is that either: a) someone doesn't know enough about this stuff to make intelligent decisions, or b) a skilled anti-bomb expert's expertise is being wasted trying to save one out of a million flyers when there are a dozen people getting blown up in Iraq daily. Maybe reprioritization is in order?

Richard BraakmanApril 24, 2007 4:23 PM

Huh? I see no such assumption.

The LRBL doesn't really "work" at all. It's simply an answer to a question. The question is, "If we find a bomb on an airplane, what should we do?"

The basic answer is of course "It doesn't matter, you're screwed". The LRBL is a slightly more refined answer, namely "If you put the bomb in this place, your chances of survival improve a little".

That those chances are going up from 1% to 1.05% doesn't really matter. It's still better than doing nothing.

If not this answer, then what? What do you tell people who say "We found a bomb in our airplane, what do we do now?"

Christoph ZurniedenApril 26, 2007 9:00 PM

> The LRBL is a slightly more refined answer, namely "If you put the bomb in this place, your chances of survival improve a little".
> That those chances are going up from 1% to 1.05% doesn't really matter. It's still better than doing nothing.

Is it really better than doing nothing?
If you do not know anything about the bomb and you do not even know if it is a bomb you get a slightly higher chance of survival if it is a bomb and if it explodes at the LRBL and a slightly lower chance if it explodes when moved.
So the overall result is, that the LRBL is useless for things which might be bombs or are bombs.

But the LRBL is quite usefull for dangerous materials which are known, e.g. http://www.pcmag.com/article2/0,1895,2122224,00.asp. If you know that these things are save to move, move it to the LRBL but do not touch them otherwise.

> If not this answer, then what? What do you tell people who say "We found a bomb in our airplane, what do we do now?"

If you are sure that it is a bomb, you might already know what to do with it, e.g. if it is save to move.
But that is rarely the case (I don't know any case, but my personal memories are not statistically significant), the number of false positives is several magnitudes higher than the number of false negatives. So it is most probably not a bomb. Can it be savely moved than? You don't know that for sure, so the correct answer for your question is in most cases[1] "Don't touch it, help is on the way."

CZ


[1]the call "We have a bomb in here!" might have caused a panic already so the personell on board might choose to take the slightly higher risk and move the packet to the LRBL.

Mike KellarMay 19, 2007 11:34 PM

Regarding the "dense material" covering the bomb in the LRBL; I think the passengers would be better served if the crew placed bags of water on/around the explosive device.

I remember seeing a detonation experiment in College. The instructor placed a thin wafer of high explosive (about the size/shape of a quarter) on a block of steel, and laid a section of 2X4 on top of the wafer. After the detonation, the steel had a 4" diameter
spall (dome-shaped section) blown from the bottom, and a hole in the top about the size of the wafer - the 2X4 had disappeared. The instructor opened the blast door and pointed to the walls of the chamber, which were covered with large railroad ties. A small portion of the board directly above the explosive had vaporized; the remaining pieces were embedded in the ties, like so many deadly toothpick sized projectiles.

Most of the blast energy tends to travel through the denser material it is in contacet with. Put something just as dense in the way (luggage), and you get shrapnel. Put a water wall in the way (trash bags of water), and you - hopefully - just get wet.

They plan to use water to dissipate the deadly blowback from shoulder-launched rockets (Future Weapons, Discovery Channel.) Might work on an explosive device as well.

BobFebruary 28, 2008 10:15 AM

Great comments and questions, but I'm not sure everyone understands what the purpose of LRBL is. LRBL is useless if a terrorist is holding the IED. It's not a "safe box" to deposit suspected bombs that we collect from passengers as they enter the plane. It's not a secret place that terrorists try to avoid. It's just a location of the plane, determined by the manufacturer, that we choose to place an IED, in the event that one is found on an aircraft. It is the location that would minimize the loss of life, and allow the greatest opportunity to land safely. If we have control over the suspected IED, then the suspected terrorist has already been disabled, or is not on the aircraft, so it's not a secret that needs to be kept from anyone. The only advantage a terrorist would get from knowing where the LRBL is, is to stand somewhere else when detonating the device.

bluefogMarch 21, 2008 1:46 AM

Maybe the companies like Boeing et al don't want the bombs ejected or defused for some insane reason...

Leave a comment

Allowed HTML: <a href="URL"> • <em> <cite> <i> • <strong> <b> • <sub> <sup> • <ul> <ol> <li> • <blockquote> <pre>

Photo of Bruce Schneier by Per Ervland.

Schneier on Security is a personal website. Opinions expressed are not necessarily those of Co3 Systems, Inc..