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Killing time watching a bit of TOP GUN, it came across my mind on the term missile lock. It comes off as meaning the live missile notably an AIM-9 heat seeking missile in a dog fight  has lock. But  confirm or counter my point, missile lock does not mean the bogie is incapable of breaking a missile lock. Am I correct to say a bogie under missile lock performing a quick and hard maneuver could break that lock prior to the missile being fired. Or is the seeker head quick enough to keep lock on with even a hard jerking bogie in a  dog fight?

 

I believe once the missile has been launched the bogie it's going after will have a harder time breaking away from this missile in flight and locked on, but again,  any qualitative stats showing odds of avoiding say an AIM-9 or similar dog fighting missile?

 

As to longer range missiles such as older AIM-7's and AMRAAM'S or even Phoenix missiles. I assume they are generally launched  towards a  incoming flight of bogies and as such would these missiles not be detected by these bogies electronically and even in time visually with the  smoke/vapour plumes and would a bogie not be able to commit a maneuver to  reduce the odds of a  strike, or I guess if proximity fused how close did/do AIM-7, AMRAAM and did PHOENIX missiles have to get before exploding?

 

These are genuine questions please as my mind was just wondering about these points.

 

Thanks in advance

Edited by Gordon Shumway
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Radar guided missiles need a radar lock on, to have a target to go to, that lock can be broken when the firing aircraft is for instance no longer pointing towards the target due to manoeuvering. The Heat seekers can also lose lock, but they are fire and forget, so you sling it away and do your thing... simplified, and I'm not a fighterpilot...

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Yes, my understanding is that AMRAAM's and PHOENIX are/were also fire and forget as they track their  targets. AIM-7's needed the firing aircraft hold a radar lock. As to evasive maneuvering once the aircraft being tracked knows a missile is heading towards it, how much time   for one   do they have to  try to it evade and  I assume these missiles have proximity fuses, how close  do they get before exploding?

 

As to AIM-9's the aircraft locked on to by one, does the pilot/crew know that an Aim-9 has it in lock  (I assume not except he/they may be worried about the  attacking aircraft having them on their 6.) even prior to weapons release. I know RWR allows crews to know their aircraft   is illuminated for radar guided missiles  but what tech may they have on  heat seeker detection if any at all? I know  on the offensive an AIM-9 gives the attacker a growl sound telling him that it has a lock.

 

 

BTW the F-15 PDF lok col... lots to read though

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For a heat-seeker launch, the defending aircraft will get no warning via the RWR as the IR-guided missile uses passive guidance. In this case, the pilot will have to visually see the attacker launch its missile and take evasive action. Some aircraft like the A-10C are fitted with a missile approach warning system which can detect a missile rocket motor ignition and give the pilot warning of a launch. 

 

Mark

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I'm certain that there are people more know more about this than me, but I'll share my understanding of how they work.

 

AIM-9s have a seeker head that can be locked into forward looking or "uncaged" to bounce around until it finds a heat source.  Current HUDs will display a diamond showing where the seeker head is looking, and when it locks onto a heat source the pilot will see it in the HUD on top of the targeted aircraft.  The seeker head can also be "slaved" to the radar, so what the radar designates the seeker head will "look" at, and if the heat source is of sufficient level, it will lock on.  For aircraft with the Joint Helmet-Mounted Cueing System (JHMCS), the seeker is slaved to the helmet sight, with a high off-boresight capability.  Once the target is locked on and in sufficient range and other parameters, the missile can be fired.  Once fired, it can lose track for a number of reasons, such as something blocking the view of the target, flares "spoofing" the missile, etc.  Missiles can also be outmaneuvered with careful planning.  Even though they travel very fast and can pull high G-forces, high G-forces at high speeds can still require a greater turn radius than a slower aircraft, so the aircraft can break at the right time and force a miss.

 

Radar guided missiles are similar in concept, and can be outmaneuvered the same way, but of course use different targeting and tracking tools.  AIM-7s only have passive radar, so the targeting aircraft must keep the target locked onto with the radar in a special tracking mode until the missile hits.  AIM-54s and AIM-120s require guidance from the launching aircraft through the first portion of the flight using a digital data link, then activate their shorter-range on-board radar for the remainder of the flight. Chaff is used instead of flares to spoof them. 

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Our AIM-9s also had a scan feature provided by the SEAM system. (Sidewinder Expanded Acquisition Mode) It would make the seeker head scan in a figure eight pattern until it sensed something, then it would lock on. By using VTAS (Visual Target Acquisition System) the seeker head could be slaved to either the radar antenna or the pilot's line of sight. This was in the mid '70s on F-4Ns.

 

AIM-7s don't lock on to the target, but they do need to be tuned to the aircraft radar's frequency mixed with the Doppler shift of the radar's locked target. Otherwise the missile's receiver won't see the reflected RF energy from the target. The missile is pre-programmed by the radar set's target intercept computer with the correct frequency and with the initial direction to the target. When it is ejected from the aircraft it rolls to orient the missile to an X configuration of the wings and fins from the + configuration that it is carried in. The missiles nose antenna pointed at the target and away it goes. The way it works is there's an antenna in the nose of the missile that sees the shifted frequency and an antenna in the tail that sees the transmitted frequency and by comparing them it knows closing velocity and can calculate its path for a lead pursuit intercept. The tail antenna is fixed as it's receiving the strong transmitted energy from the aircraft, not the weak reflected return and is only using it for the frequency shift and I think range information that encoded into the RF guidance beam. That's why semi-active is better than a beam rider, it can lead the target while a beam rider has to do a tail chase intercept that eats up range.

 

The search and track radar is a pulse system, the missile guidance radar is continuous wave (CW). That's how a target's RWR can know whether it's being pinged, locked on to or actually has a missile guidance radar illuminating it. It wouldn't be able to tell if there was actually a missile on the way though. Back when I worked on this stuff, I don't believe there was any way to know if a heat seeker was targeting you other than seeing the motor's smoke.

Edited by Grey Ghost 531
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3 hours ago, GW8345 said:

The AIM-7 Sparrow is a semi-active guided missile.

Correct:

Semi-active radar homing (SARH) is a common type of missile guidance system, perhaps the most common type for longer-range air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is only a passive detector of a radar signal – provided by an external (“offboard”) source — as it reflects off the target(in contrast to active radar homing, which uses an active radar: transceiver). Semi-active missile systems use bistatic continuous-wave radar.

 

https://en.wikipedia.org/wiki/Semi-active_radar_homing

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On ‎7‎/‎08‎/‎2017 at 1:07 PM, Gordon Shumway said:

Yes, my understanding is that AMRAAM's and PHOENIX are/were also fire and forget as they track their  targets. AIM-7's needed the firing aircraft hold a radar lock. As to evasive maneuvering once the aircraft being tracked knows a missile is heading towards it, how much time   for one   do they have to  try to it evade


Not much. See the "Towering Inferno" mission flown during the AIMVAL/ACEVAL trials in 1977, so named because all the combatants were killed. Four F-15's launched ACMI simulated AIM-7's at four F-5's. The need to keep a lock for the semi-active homing AIM-7 drew the F-15's within range of the AIM-9L the F-5's had. All of the F-5's were shot down, but not before they all launched simulated AIM-9L shots that killed the F-15's.

Edited by Mumbles
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