SAM countermeasures for passenger jets

With the recent shootdown of MH17, there is talk of fitting anti-missile countermeasures to passenger jets. This seems ridiculous for a bunch of reasons, but it got me to wondering about how you (a pilot of any target aircraft) know a missile has been targeted and is now inbound.

A radar-guided missile would need to be painting you with radar, or communicating via radio with a ground-based radar system that is painting you with radar. Your plane could certainly be equipped with a radar detector - but how would you distinguish between the missile’s radar and any other radar (e.g. ATC)? And how would you know that a missile has actually been launched (as opposed to the launcher just tracking/targeting you)?

An IR-guided missile wouldn’t be expected to emit any radiation. So if one of those locks on to the heat signature of your engine and launches, how do you know it’s headed for you and that you should drop some flares?

Many modern military aircraft can automatically drop flares, chaff, and do other countermeasures without human input. Of course the aircrew can manually deploy countermeasures also.

However this stuff isn’t cheap. It would probably add a $1 million or so to each aircraft and more so to retrofit existing aircraft. Plus it would need to be constantly maintained; loaded; and tested.

I remember them testing the chaff dispenser on a F-111D years ago. I’d hate to be near it if someone deployed it on the ground. Flares would even be worse.

Sure, but how does it know “radar-guided missile inbound” versus “being painted by SAM launcher radar” or “being painted by ATC radar”?

And how does it know “IR-guided missile inbound”?

YouTube is full of videos of flares being dispensed from military aircraft, and yes, when they fire off a bunch, it’s pretty spectacular.

Wikipedia shows a chaff package as just a tube of tiny metallic threads that get dispersed. Is chaff dispensation/dispersal notably energetic? Or you do you just have a strong aversion to being draped with metallic threads?

I’m not sure about the IR-guided missile.

During the chaff test that I witnessed, the chaff shot into a tube that connected to a barrel. The chaff went round and round inside the barrel at a pretty high rate of speed before stopping. I assume that they want the chaff to be pretty far away from the aircraft; however, we all know what assume means!

This is only the second or third time this has happened in all history? The problem is that equipment is expensive, and it can even malfunction.

Another problem is that this problem is fundamentally unsolvable. A passenger jet is a gigantic metal can with extremely hot exhaust. You can devise tricks to fool a given generation of SAM, but, ultimately, I don’t see how the long term situation won’t be “sams hit the jet at least 90% of the time”

You could have a couple of wild weaselsfollow the aircraft.
I have not idea how to pay for it.

These people sure did.

Aren’t airliners already pretty hard targets? They fly high and fast, which puts them out of reach of all but the most capable anti-aircraft missile systems. Sure, some can reach out and touch a jumbo jet, but most bad actors are limited to man-portable weapons (at best) that just won’t come close.

Some late WW2 AAA gunscould reach those heights. And those are easier to get hold of than SAM systems.

For one thing, an anti-aircraft missile will typically have an X band radar, whereas airport surveillance radars will be of a lower frequency. Within the X band, any radar has unique characteristics, so if you’re getting pinged by a radar of this frequency with those attributes, it is not difficult to know that an SA-2 is coming at you.

IR missiles are typically detected with optical sensors operating in the IR or UV wavelengths. If the sensor sees something coming at it that is very hot and fast, the klaxons go off.

No, I saw a report claiming that commercial airliners have been shot down 18 times in the last 40 years or so. Not always during a shooting war – IIRC at least one time it happened during a live-fire missile test when a plane was hit at what they thought was beyond the range of the missile.

Wiki lists 21 shoot downs since the 50s.

Military planes have radar warning receivers which detects incoming radar signals. All types of radars generate pretty unique signals because of their different technologies, requirements, and design. Search radars use a different frequency band than tracking radars, and they also use much different sweep rates. Military radars have specific pulse, frequency, and other patterns that will easily let a RWR quickly classify it as a certain system. Many radars also switch patterns from tracking to active guidance when they’re actually guiding a weapon, which makes it clear to the target aircraft that they’re being fired at. Some missiles actively guide themselves with their own radar, which would also tip off the targeted aircraft.

IR missiles are much harder to detect. They’re also much shorter ranged, so if you’re in their effective targeting range you have very little time to react. There’s no way for a RWR to detect an incoming IR missile since it emits no signals. There are some systems that detect incoming missiles by looking for their heat signature of even detecting them with a radar unit on the targeted plane, but I’m not sure how commonly or effective they’re actually deployed.

Or just not fly over danger zones.

El Al, Israel’s national airline, has anti-missile technology on its jets.

That is a different threat profile - El Al is worried about a shoulder-launched IR missile during take-off/landing. In that situation, flares/ICRMs are suitable and manageable. The missiles are also likely to be targeted to hit an engine, which would be problematic but not necessarily disastrous.

Countermeasures for high altitude radar guided SAM missiles are quite different and far more complex. Not the sort of thing suitable for a commercial jet. But then, generally the sort of people interested in destroying commercial airliners did not have access to SAM missiles and the training to operate them.

Don’t fly over what kind of zone?

Those systems are on probably every military aircraft that fly in potentially dangerous airspace, from utility helicopters to cargo jets to fighter aircraft.

Why do missiles and airport radars use different frequencies? what makes one frequency range better suited for one use, and not for the other?

If the missile is coming straight at them, how does the system assess missile speed?

Isn’t the problem fundamentally unsolvable in that military surface-to-air missile systems

  • are intended to shoot down military aircraft fitted with state of the art countermeasures
  • would not continue to be bought and deployed if they did not have a decent chance of success in that mission
  • so, would still be able to shoot down civilian airliners if these were fitted with all countermeasures available for military aircraft?

Not really; the missiles are intended to shoot down aircraft, with or without countermeasures. Not every military plane from every possible adversary is going to have countermeasures of any sort installed, so the missiles have to be able to shoot them down as well.

Countermeasures are hardly foolproof; they come in 3 basic flavors- ECM, chaff and IR flares.

ECM stands for electronic countermeasures; this is when the aircraft jams either the search radar, making it hard to locate the aircraft at all, or they jam the missile guidance radar and directly interfere with the missile’s guidance. This is very missile type specific, as each one uses a different frequency and band and signal type, so if the attacking missile is unknown, it might be hard to jam.

Chaff is basically a bunch of little aluminum foil strips that reflect radar. Blow a big cloud of those out of the back of the plane and all of a sudden that discrete airplane return on radar becomes a 300 yard wide cloud. This makes it harder to both pick up the plane and track it.

Flares are used against IR missiles, since all that ECM and chaff business doesn’t do anything against them. The idea behind flares is that since the IR missiles are homing on the jet engines as the hottest thing on the plane, if you fire out some flares, they’re going to be hotter, and either distract the missile, or paralyze it by giving it too many things to try and home in on.

The bigger question is why bother? Very few airliners get shot down- enough to where it’s a totally freak occurrence. I’d imagine that in terms of lives saved over any given time period, improvements in weather radar and in better maintenance procedures would probably be far more cost-effective than defending against missiles.