NO TRACK LAUNCH is driving me loco!

[Yurgon]

2 hours ago, JetCat said:

By the way ..... is it true that the recoil of the Gau8 equals full thrust of one of the A-10 engines?

Wikipedia and, more importantly, Randall Munroe of xkcd both agree.

Wikipedia:

Quote

The average recoil force of the GAU-8/A is 10,000 pounds-force (45 kN),[5][21] which is slightly more than the output of each of the A-10's two TF34 engines of 9,065 lbf (40.3 kN).[22] While this recoil force is significant, in practice a cannon-fire burst slows the aircraft by only a few miles per hour in level flight.

xkcd:

Quote

The GAU-8 Avenger fires up to sixty one-pound bullets a second. It produces almost five tons of recoil force, which is crazy considering that it’s mounted in a type of plane (the A-10 “Warthog”) whose two engines produce only four tons of thrust each. If you put two of them in one aircraft, and fired both guns forward while opening up the throttle, the guns would win and you’d accelerate backward.

So yes, the GAU-8 has slightly more recoil than the thrust of one of the engines.

Of course my favorite quote from that xkcd is still this one:

Quote

To put it another way: If I mounted a GAU-8 on my car, put the car in neutral, and started firing backward from a standstill, I would be breaking the interstate speed limit in less than three seconds.

14 minutes ago, ASAP said:

No. The gun firing has no real effect on the airspeed of the aircraft. that is a myth.

In a typical one-second burst, there shouldn't be much of an effect. Since the gun is typically fired in a descent, we also have to factor in the pull of gravity in a dive that would further counter the recoil's effect. However, in level flight, a full 18 second salvo that empties the entire ammo drum should actually lead to quite a significant speed reduction.

[jaylw314]

2 hours ago, JetCat said:

Wonderful this is a super-detailed tutorial about the Maverick. It was the first time I tried the A-10 and did what the Maverick tutorial said, but without really knowing what is going wrong.

So the targeting pod is only stabilizing itself with the help of a build-in gyro system without actually locking on something when doing this, interesting. And the IR view of the Maverick must extra be locked onto something with clearly visible thermal differences.

Is the Maverick (or any of the screens) reacting to the force correlate mode? I have noticed that nothing on the screens or the crosshair change when clicking the boat switch center.

In the tutorial videos no one is using correlate mode, in the videos they rotate the seeker of the Maverick with China hat forward long to their target pod point, and manually lock on the Maverick with TMS up short button press which makes the crosshair lines of the Maverick screen flicker a bit.

I am looking forward to test-fly the A-10 more tomorrow get both the visually guided and laser-guided Mavericks into the target.

By the way ..... is it true that the recoil of the Gau8 equals full thrust of one of the A-10 engines?

 

The MAV page can be a little confusing.  If you move the seeker somewhere by slaving it to something else (like the TGP or TAD), the Maverick seeker stays pointing in that direction but is not actually tracking anything.  In that case, you need to press TMS Up short to tell it to start tracking something, then you can fire.

OTOH, if you move the Maverick seeker with the slew controls, it will start tracking something when you let go immediately.  Of course, whether it tracks the correct blip on the screen is the source of much heartburn...

@ASAP detailed this in his soliloquy above, it's worth a read again  

[ASAP]

Found this quote from a Col that flew the Hawg:

One retired Air Force Col. Steve Roehl once said, "I have fired as many as 500 rounds in one trigger burst, that takes just about seven, eight seconds, and it had no impact on the airspeed of the aircraft.

It boils down to simple physics: Force = Mass x Acceleration. Working all this out, the bullets are only about three-quarters of a pound. The airplane, in a typical combat mission, is 40,000 pounds. When you got 40,000 pounds moving at 350 knots, that's a lot more momentum than a three-quarter pound bullet moving at 2,000 feet per second.
Momentum of aircraft approximately = (530)*(40,000)
Momentum of bullets approximately= (.75)(65)(2000)
 

That's 21,200,000 ft/lbs of energy vs 97,500 ft/lbs of force.

Edited May 2 by ASAP

[ASAP]

24 minutes ago, jaylw314 said:

OTOH, if you move the Maverick seeker with the slew controls, it will start tracking something when you let go immediately.  Of course, whether it tracks the correct blip on the screen is the source of much heartburn...

This is where the art of the maverick comes into play. In actuality the pilot has to be very deliberate about slewing the maverick onto the correct target and verifying the quality of the lock before pressing the pickle button. From what I've heard DCS is a lot easier than real life in that regard.

[Yurgon]

2 hours ago, ASAP said:

Momentum of aircraft approximately = (530)*(40,000)
Momentum of bullets approximately= (.75)(65)(2000)
 

That's 21,200,000 ft/lbs of energy vs 97,500 ft/lbs of force.

My high school physics is a few years in the past, but for starters I'm pretty sure that acceleration is not the same as speed and you're missing a second squared here or there. It's also a but unclear where you get the 530 that gets multiplied with 40,000 (530 knots? Or 350 knots converted to feet/second, in which case it should actually be closer to 590 feet/second?) or what the 65 means in the second calculation - the number of bullets for a 1 second burst?

The thing is, assuming all your math was correct, then...

That's 21,200,000 ft/lbs of energy vs 97,500 ft/lbs of force per 65 bullets, and with an 18 seconds burst (expanding the full gun) that would still bring us up to 1,755,000 ft/lbs and thus about one twelfth of the aircraft's energy, which I'm sure would lead to a fairly noticeable reduction in aircraft speed.

But once again, there's usually not much of a reason to fire the gun in horizontal flight, and when we add the typical acceleration that happens in a dive, that should easily overcome the stopping power of the gun's recoil. Without further context regarding the above quote, I'll go ahead and assume that the Colonel was not in fact referring to firing from level flight.

Ultimately, though, no one said the gun would stop the jet or even slow it down to a noticeable degree (well, I actually did, but this discussion wasn't started by that argument). The question was if the gun generated more recoil than a single engine provides in thrust, which according to multiple sources is a true statement. Put differently, if the gun was fired at the beginning of a takeoff roll, the jet would accelerate as if one engine was simply not producing any thrust. And if two GAU-8s were firing from one A-10 (ignoring where the second one would go, and the weight that it adds) at the beginning of the takeoff roll, it seems that with two good engines operating at full power, the jet would still go backwards while the guns keep firing.

Edited May 2 by Yurgon

[jaylw314]

Urrrgh, you guys are killing me; you guys are talking momentum, not energy 

The momentum calculation is the correct approach, and luckily, the units don't really matter if you compare the two, but don't call them ft x lbs or energy! 

If you lose 1/12 of your momentum, you lose 1/12 of your speed, so that's a drop from 350 knots to 320 knots over 18 seconds (level with engines idle).  That's pretty trivial compared to engine power and diving I think.

Sorry OP -- waaaaaaaay OT 

Edited May 2 by jaylw314

[Yurgon]

7 hours ago, jaylw314 said:

Urrrgh, you guys are killing me; you guys are talking momentum, not energy 

Don't look at me! I'm just following ASAP's lead.

But yeah, it's a bit OT, and in this regard there's simply nothing for me to add on topic because ASAP already covered everything there.

Edited May 2 by Yurgon

[ShuRugal]

13 hours ago, ASAP said:

No. The gun firing has no real effect on the airspeed of the aircraft. that is a myth.

That isn't the question which was asked.

The GAU-8 has a recoil force of roughly 45 kN when firing at its maximum rate.  The TF-34 has a thrust of 40.3 kN.  So, the answer to the question asked is "yes", or if we want to be pedantic, "no, it's 4.7 kN GREATER than one engine".

 

What you said was TRUE, firing the gun has no notable effect on airspeed, but this is because the gun is typically fired in short bursts, and the total mass of the aircraft is great enough for a short burst to not make an appreciable change, especially when both engines are producing thrust and/or the aircraft is diving on a target.  is is NOT because the gun does not have significant recoil thrust.

Edited May 2 by ShuRugal

[jaylw314]

2 hours ago, ShuRugal said:

That isn't the question which was asked.

The GAU-8 has a recoil force of roughly 45 kN when firing at its maximum rate.  The TF-34 has a thrust of 40.3 kN.  So, the answer to the question asked is "yes", or if we want to be pedantic, "no, it's 4.7 kN GREATER than one engine".

 

What you said was TRUE, firing the gun has no notable effect on airspeed, but this is because the gun is typically fired in short bursts, and the total mass of the aircraft is great enough for a short burst to not make an appreciable change, especially when both engines are producing thrust and/or the aircraft is diving on a target.  is is NOT because the gun does not have significant recoil thrust.

 

Just to clarify, that statement 45 kN "when firing at its maximum rate" is deceptive.  The "firing at its maximum rate" suggests its the sustained recoil force when the trigger is held down.  That figure appears to be the maximum instantaneous recoil force, which would be the same whatever the firing rate was (or how many rounds fired).  Since the round only applies an impulse to the plane's momentum for a fraction of the time between rounds, it doesn't change the momentum of the plane by 45,000 kg x m/sec every second.

Instead, the sustained recoil force can be easily calculated if we assume each round is 0.3 kg, the speed is 670 m/sec, and firing 60 rounds/sec, the sustained force is more like 13.5 kN.  That doesn't include some small additional force from gases being blown forwards, but still much less than 40 kN.

 

[JetCat]

Why is the file size of attached screenshots and pictures are getting smaller and smaller by the day? A few days ago it was 300kb, now 100..... this size is so small it is almost impossible to create such small JPEG´s with Photoshop.

Thanks to the awesome guide here and a bit of learning I am now able to shoot Mavericks even without infrared guidance but computer waypoints. Lovely! This is especially important to target buildings and areas in the scenery without infrared lock for more personalized missions with background story.

The backstory of this Normandy map mission was, the evil scientist Dr. Kruger S. Krötenbrugger has a doctor´s meeting on his farm where all local doctors, pharmacists and surgeons are instructed to make certain human experiments in a normal civilian environment (outside of camps and prisons) possible. But worry not the A-10 loaded with Mavericks is here to prevent this from happening! A background story more than "over there parks enemy tank!" makes missions more interesting, cool, and fun. That´s why every mission gets one, with the most stupid and clichè protagonist names possible.

The mission was accomplished by shooting a Maverick without infrared lock:

MCDU round switch is switched to MARK (well at least in the Fenix Airbus it is called MCDU.)

Lightning target pod is used to visually track something, with point lock and not area lock, but with no visible infrared signature for the targeting pod or the Maverick to lock on. Was done by using the HUD marker and the targeting pod display zoom for more precise targeting.

After visually finding the target TMS switch right short is pressed, a waypoint in the MCDU was created. MCDU showing WAYPT T, HUD showing A/MRK A. Three waypoints where created this way, can be selected with the HUD keypad "STEER" switch and China hat forward long to make the TGP camera jump to the waypoint quick.

Selecting Maverick, making the Maverick display SOI, China hat forward long and the crosshair of the Maverick jumps to the waypoint of the MCDU.

Moving the seeker head of the Maverick just a bit a millimeter or so just short touching it for a slight movement, and pressing force correlate button center made a lock on possible.

 

[razo+r]

6 minutes ago, JetCat said:

Why is the file size of attached screenshots and pictures are getting smaller and smaller by the day? A few days ago it was 300kb, now 100..... this size is so small it is almost impossible to create such small JPEG´s with Photoshop.

You need to delete some of your attachments (profile - > attachments) . You have a total of about 200mb available. If you get close to it, you need to delete some of the old ones you don't need anymore, or start using external sites like Imgur. 

[JetCat]

Ah I see. Thank you very much for the info Uploading the picture to a file hoster is no problem!

I think the no track launch comes from not moving the seeker crosshair of the Maverick just a tiny bit - because the crosshair immediately closes and locks afterwards (and blinks or flickers which is also a sign for a functional lock). So pressing the force correlate (boat center) button and moving the crosshair just a bit seems to solve the blocked missile launch problem.

 

 

Edited May 3 by JetCat

[Yurgon]

5 hours ago, JetCat said:

MCDU round switch is switched to MARK (well at least in the Fenix Airbus it is called MCDU.)

Well this ain't no Airbus.

It's just CDU, and the control in question is the STEER PT dial on the Auxiliary Avionics Panel. I find that it always helps to have a quick look at the DCS A-10C manual and pick the "official" designation, because every DCS player will know these names (or can easily look them up in that very same manual).

5 hours ago, JetCat said:

Lightning target pod is used to visually track something, with point lock and not area lock

Like ASAP already said, when your target is not moving, it's usually preferable to use AREA track instead of POINT track. Any particular reason you prefer POINT track in this case?

5 hours ago, JetCat said:

Three waypoints where created this way, can be selected with the HUD keypad "STEER" switch and China hat forward long to make the TGP camera jump to the waypoint quick.

Selecting Maverick, making the Maverick display SOI, China hat forward long and the crosshair of the Maverick jumps to the waypoint of the MCDU.

China Hat Forward Long is "Slave All to SPI". In this description, you're slaving all sensors to SPI, don't to anything with that SPI, and then slave all sensors again. That's one step that's not needed. With TGP on the right MFCD and MAV on the left MFCD, a single "Slave All to SPI" will slave both the TGP and the Mav to the same SPI simultaneously, regardless of SOI.

5 hours ago, JetCat said:

Moving the seeker head of the Maverick just a bit a millimeter or so just short touching it for a slight movement, and pressing force correlate button center made a lock on possible.

For starters, when you slave the Maverick directly on the desired target, you could just as well hit TMS Forward Short with MAV as SOI to command a track, which was already explained above.

And then, why would you attempt to FORCE CORRELATE when you already get a good track? That's not needed here and it's a bit unclear why you would try force correlate after already achieving a track. The original NO TRACK LAUNCH INHBT happens when the Maverick is not tracking and is not using force correlate. Either a track or force correlate are enough to get the missile off the rail, and using both methods together doesn't (usually) offer any benefit whatsoever and just adds a step that's not needed.