how do pilots know a missile is coming?

Inspired by this thread, which describes the shoot-down of a military helicopter that appears to take no evasive action.

The basic question: how do military aircraft and/or their pilots know when a missile has been launched at them?

Obviously it’s possible to know when one is being painted with radar; this was the basis for the Wild Weasel program. But how does one know when a radar-guided missile has actually been launched, and that one needs to dispense chaff and/or take evasive action?

And what about IR-guided missiles? Flares can distract/confuse them, but you have to know that one is on its way before you can even consider using flares. So how do you know when a Sidewinder is inbound?

I don’t know what systems are on the Turkish aircraft such as the one in the video, but there are sensors on many types of aircraft that are more or less cameras that are mounted all around aircraft that are good at detecting the heat signatures of missiles. These systems can be so sophisticated that they can determine the type of missile fired by the characteristics of the heat signatures, and then automatically tell the other systems on the aircraft to take countermeasures (i.e., dump chaff, launch flares, activate other jamming systems, etc).

Here is one example of such a system:

ETA: there’s also software upgrades to some of these type of systems so that they can tell if someone is shooting at you (bullets, not missiles) by detecting muzzle flashes from small arms, crew served weapons, or anti-aircraft artillery.

Being painted with a fire control radar (as opposed to being pinged by a search radar) pretty much means a radar guided missile is about to be or has been launched at you, so it’s time to start looking for the smoke trail of a missile headed your way. As a side note, the F-117 shot down by the Serbs with an ancient SA-3 didn’t have said warning because the SA-3s were launched ‘blind’ without using the fire control radar until they were nearing the end of their flight at which point the fire control radar was turned on performing what’s known as a lock-on after launch.

That’s historically been a lot harder, since IR guidance is passive the target plane would have to rely on keeping their eyes open in dangerous areas; but often aircraft lost to SA-7/Stinger type shoulder fired IR missiles never knew they were coming.

If operating in an area where you think there is an IR threat, usually you have a visual system operating–either EO, and/or the mark-I eyeball, which means you have crew mounted in the aircraft dedicated to watching the ground below.

ETA: I credit the guys at the windows in my plane for saving our sorry asses when we got launched at. Twice.

There are some YouTube videos by SR71 pilots where they talk about being tracked by enemy fire control radar. That was nothing to worry about, but the did worry when the missile started communicating with the ground radar. That meant the missile was in flight, and they knew they were being shot at. Apparently, just bumping the throttle up a tad was enough to throw the radar off and send it into a re-acquisition mode, which took a minute. In that minute the SR71 had moved 35 miles. They were never hit. Mach 3.2 must be quite a thrill.

On the issue of radar-guided missiles, the frequencies, pulse repetition frequency (or choice of continuous wave vs pulses) changes depending on whether a radar is searching, tracking or guiding.

If the enemy is using AESA radar, the target may never know it was being lit.
I’d expect the cameras Ravenman mentions to be useful for most ground-launched IR missiles since they will often have a short range and so they burn close enough to the target for the target to see it. Against IR missiles launched from the air or which are launched from the ground while having some kind of non-IR guiding assistance, the burn could occur at longer distances and be more difficult to spot.

The advantage of lock-on after launch is leaving less time to countermeasures and evasive action, correct?

If so, I get the impression that the F-117 was not the kind of aircraft that could or would do much in terms of countermeasures and evasive action. Evasive action requires maneuverability and high acceleration which the F-117 didn’t have. I don’t know what kind of countermeasures it had but it seems like it relied very heavily on stealth and little else for survivability.

So, why do a lock-on after launch when shooting at a F-117?

“We ascend to…well, I can’t tell you that…We dive to accelerate to…I can’t tell you that.”

IR doesn’t tell you distance to target.

So if the F117 is on a curve, which it will be knowing that it protects from IR missiles , the missile can’t match or predict the turn rate or velocity or heading and pitch … As it closes, the mismatch in direction and speed of the plane means the IR missile misses. At that range its going to take radar to get distance, and hence speed and heading, and preemptively cut the corner and get the plane into the centre of the cone…

I understand they fired three, hoping one would get a lock.

At least in the HAWK anti aircraft missile system, a semi-active radar homing system which paints the target with radiation, and the missile follows and tracks the reflection of that radiation, the Continuous Wave tracking radar locks onto the target, which can detect that radiation if so equipped and alert the crew. When the missile is launched, the tracking radar goes dark momentarily so as to avoid overpowering the missile sensors. This dip in signal and return to full strength mean the shit just got real.

Yes, with the disadvantages of it being harder to perform and relying on a good element of luck. Semi-active radar homing is designed for the receiver on the missile seeing the reflection from the guidance radar on the target aircraft from launch until impact (or at least command and inertial midcourse guidance combined with SARH in the terminal phase), doing a lock on after launch is flying by the seat of your pants. The missiles are launched ballistically to the guestimated place that the plane will be; the guestimate could be wrong, the plane might change course, the receiver might not pick up on the reflection and react in time, etc.

My understanding is they were doing it as standard procedure, not specifically for the F-117. They were reluctant to turn any of their radars on more than briefly out of fear of NATO sending an anti-radiation missile their way. Apparently they had their radars on for less than 17 seconds in this engagement, and only one other NATO aircraft was lost to a SAM during the entire bombing campaign.