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HARM selective jettison


snipy
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When using the S-J page, selecting a HARM, and hitting the pickle button, the rocket engine on the HARM is ignited, sending the explosive weapon somewhere. 

This occurs even with the master arm not set to on.  Master arm off, or simulate, meaning weapons safe, allows a HARM's engine to ignite. 

I'm told this is correct as is, but it strikes me as highly unlikely that the United States military would allow a rocket engine'd explosive to come off the rail at full blast, with the safety on. 

Does anyone else think it logical that both the weapon manufacturer, the airplane manufacturer and the DoD would allow weapons to launch with the safety on?  I find it illogical, so much so, that I can't believe that is correct as is. 

Anyone have any comment on why S-J just wouldn't do exactly what emergency jettison button does, or why the US military believes it should fire off rockets when the safety is on? 

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It would depend how the HARM is held onto the pylon on the real aircraft. I do not know the answer to this, but there may be no facility to "drop" the weapon off the pylon, It may need to propel itself forward off the pylon. As far as I know when its being fired normally its not a drop-free and then ignite weapon, It lights its motor while still attached the to the aircraft and propels itself forward off the rail. I'm sure many IRL F-16 peeps can chip in, but that would be my first guess.

Does the emergency jettison drop the pylon adapter as well?

ST on Twitter: "Perfect capture of F-16 #Viper launching AGM-88 #HARM  anti-radiation missile. Quality of US rocket motors is unparalleled.  https://t.co/TxENmjeamf" / Twitter


Edited by Deano87

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3 minutes ago, Deano87 said:

It would depend how the HARM is held onto the pylon on the real aircraft. I do not know the answer to this, but there may be no facility to "drop" the weapon off the pylon, It may need to propel itself forward off the pylon. As far as I know when its being fired normally its not a drop-free and then ignite weapon, It lights its motor while still attached the to the aircraft and propels itself forward off the rail. I'm sure many IRL F-16 peeps can chip in, but that would be my first guess.

Does the emergency jettison drop the pylon adapter as well?

ST on Twitter: "Perfect capture of F-16 #Viper launching AGM-88 #HARM  anti-radiation missile. Quality of US rocket motors is unparalleled.  https://t.co/TxENmjeamf" / Twitter

 

Emergency jettison doesn't ignite, it drops.  It might drop pylon as well, but it does demonstrate that there is a way to jettison that doesn't involve an active launch.

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In general AG missiles have two methods of jettison:

  • Unguided launch of the missile from the rail
  • Jettison of rack which holds launcher rail

On SJ SMS page often you can cycle through multiple modes of jettison for a station. Just keep pressing the OSB and different things will highlight. For example Mk82 on TER you can jettison a bomb from TER or you can jettison TER from airplane. Here is a track showing jettison ofHARM by unguided launch, then LAU-118+HARM, then LAU-118 alone. The choice is up to the pilot.

It's not possible to drop a missile off a rail. They can only slide off the rail in a forward direction. When loading the prongs on top of the missile are loaded by sliding it backward on a rail and then a pin locks it in place so it doesn't fall off. During launch the rocket motor breaks the pin and the missile slides forward again.

Master arm switch is for a weapon to be armed with its targeting electronics operating and fuze ready. Stuff can still come off the airplane with master arm in safe position: chaff, flares, jettisoned fuel tanks, jettisoned stores, etc. A missile is relatively safe when fired unarmed. Obviously if it hits you it would hurt but the warhead doesn't do the same thing hitting the ground unarmed compared with armed.

F-16 HARM jett options.trk

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2 hours ago, Frederf said:

In general AG missiles have two methods of jettison:

  • Unguided launch of the missile from the rail
  • Jettison of rack which holds launcher rail

On SJ SMS page often you can cycle through multiple modes of jettison for a station. Just keep pressing the OSB and different things will highlight. For example Mk82 on TER you can jettison a bomb from TER or you can jettison TER from airplane. Here is a track showing jettison ofHARM by unguided launch, then LAU-118+HARM, then LAU-118 alone. The choice is up to the pilot.

It's not possible to drop a missile off a rail. They can only slide off the rail in a forward direction. When loading the prongs on top of the missile are loaded by sliding it backward on a rail and then a pin locks it in place so it doesn't fall off. During launch the rocket motor breaks the pin and the missile slides forward again.

Master arm switch is for a weapon to be armed with its targeting electronics operating and fuze ready. Stuff can still come off the airplane with master arm in safe position: chaff, flares, jettisoned fuel tanks, jettisoned stores, etc. A missile is relatively safe when fired unarmed. Obviously if it hits you it would hurt but the warhead doesn't do the same thing hitting the ground unarmed compared with armed.

F-16 HARM jett options.trk 183.37 kB · 0 downloads

 

Thank you, this is a fantastic explanation, and track.  There is a way to S-J the HARM without launching it, and I'm just not pushing enough buttons.

I was working under the incorrect assumption that the only way to get it off the plane, using S-J was to launch it, and that felt wrong.  I seem to remember that in an earlier version, soon after HARM release, that I just needed to press the OSB button once, and pickle, and the rack and missile came off.  But now I need to press twice, make sure both are highlighted, and there we go. 

Is it a quirk of the F-16's systems design that the default S-J method for an A-G missile is unguided launch and not jettison rack and missile? Seems like the default should still be the same as the emergency jettison, which is rack and missile.

It also doesn't make sense to me that someone could be out on the range on SIM, doing a dry run for some training, and, for whatever reason, launch an A-G missile into someone's back yard, but, I suppose that too is a quirk of the systems. 

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2 hours ago, snipy said:

Is it a quirk of the F-16's systems design that the default S-J method for an A-G missile is unguided launch and not jettison rack and missile? Seems like the default should still be the same as the emergency jettison, which is rack and missile.

Only AGM-88's. It's an anti compromise feature. The F18 does it too I believe.

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3 hours ago, snipy said:

Is it a quirk of the F-16's systems design that the default S-J method for an A-G missile is unguided launch and not jettison rack and missile? Seems like the default should still be the same as the emergency jettison, which is rack and missile.

It's just the way the SMS works. First button selects the weapon, second press selects the weapon plus suspension gear. That goes for all weapons, bombs, Maverick, whatever. I think it's a perfectly reasonable logic, progressively removing more and more hardware requiring more presses. As before, no way to drop a missile off of a rail. They slide on front-to-back and they come off back-to-front. The only way a missile and rail separate in flight is by the rocket motor.

SOP might be to jett the LAU and missile together preferentially but that's a rule by the Air Force. You couldn't tell by looking at the system. I wouldn't read much intent on which one is accessed by one press or two presses as being more or less desirable.

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Just now, Frederf said:

It's just the way the SMS works. First button selects the weapon, second press selects the weapon plus suspension gear. That goes for all weapons, bombs, Maverick, whatever. I think it's a perfectly reasonable logic, progressively removing more and more hardware requiring more presses. As before, no way to drop a missile off of a rail. They slide on front-to-back and they come off back-to-front. The only way a missile and rail separate in flight is by the rocket motor.

SOP might be to jett the LAU and missile together preferentially but that's a rule by the Air Force. You couldn't tell by looking at the system. I wouldn't read much intent on which one is accessed by one press or two presses as being more or less desirable.

In a crisis, the fewer things one needs to do the better.  So I'm thinking, if I need to jettison the HARM, I'm probably going to want to do the fewest things possible to achieve the result, while minimizing additional damage or destruction, to me or something else.  So to me, that would mean default to the thing that doesn't launch a missile and possibly strike something, or go somewhere.  Dropping the HARM, like dropping the tanks, someone in flight could just mark it.  But a launch... now I've got to bring a lot of variables in to actually figure out where it landed.

So, to me, from a systems and repetition stand point, I'd want the same thing to happen like everything else, but if I couldn't make it like everything else, then I'd want to put a check somewhere in the middle of the process, to clue me in that what I'm doing is wrong.  Such... if it's going to be a launch, requiring master arm on.  Now you say that arms the weapon.  Ok, then make the check WPN ON.   Or does WPN ON also arm the missile?

This whole process just seems to be missing a step, that could cause some things to go sideways in a high pressure situation, that don't need to be missing.  But, if that is the way it is, that's the way it is.  At least if I remember to hit it twice, I can at least just drop it and mark.

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4 hours ago, snipy said:

In a crisis, the fewer things one needs to do the better. 

In a crisis shouldn't you use Emergency Jettison? 

"Subsonic is below Mach 1, supersonic is up to Mach 5. Above Mach 5 is hypersonic. And reentry from space, well, that's like Mach a lot."

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6 ore fa, Frederf ha scritto:

It's just the way the SMS works. First button selects the weapon, second press selects the weapon plus suspension gear. That goes for all weapons, bombs, Maverick, whatever. I think it's a perfectly reasonable logic, progressively removing more and more hardware requiring more presses. As before, no way to drop a missile off of a rail. They slide on front-to-back and they come off back-to-front. The only way a missile and rail separate in flight is by the rocket motor.

Makes sense, it is just how racks work. Then, out of curiosity, should also the Maverick jettison work the same way? Following this logic it should. I am not sure whether jettisoning a Maverick without the rack should ignite the motor or not and what is the current behavior in DCS


Edited by Tormox

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23 hours ago, snipy said:

When using the S-J page, selecting a HARM, and hitting the pickle button, the rocket engine on the HARM is ignited, sending the explosive weapon somewhere. 

This occurs even with the master arm not set to on.  Master arm off, or simulate, meaning weapons safe, allows a HARM's engine to ignite. 

I'm told this is correct as is, but it strikes me as highly unlikely that the United States military would allow a rocket engine'd explosive to come off the rail at full blast, with the safety on.

Selective jettison requires master arm on in the real-world aircraft (this is currently modeled inaccurately in DCS). It is true however that an S-J of an AGM-88 will result in an unguided launch.

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10 hours ago, Tormox said:

Makes sense, it is just how racks work. Then, out of curiosity, should also the Maverick jettison work the same way? Following this logic it should. I am not sure whether jettisoning a Maverick without the rack should ignite the motor or not and what is the current behavior in DCS

 

I haven't checked but if there's a Mav jettison then it's by rocket motor for the same reasons.

EDIT: Selective jettison by firing is currently only available for AGM-65 on LAU-88 but not LAU-117. Apparently -117s can't do that. I don't know why but it's in the book. With LAU-88 the normal logic of weapon first, rack second applies. The word "HOT" should appear at the bottom center of the page in place of the normal "RDY" when jettisoning stores by any method.

However with AGM-65, the missile is launched whenever RDY is displayed and WR is pressed, tracking or not. The warhead is armed which is less safe but it would be a method of jettison by firing from a single rail.


Edited by Frederf
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