Durandal drop profile?

[Andurula]

Does anyone have some basic specs for dropping the Durandal anti-runway bomb?

Sight depression?  Minimum drop height? Maximum release speed?... Something like that?

[Nealius]

Brochure numbers are minimum 200ft maximum 550kts (I think?). In DCS any drop below 500ft results in the rocket motors failing to ignite, and anything below 800-1000ft won't allow a proper vertical shot into the runway. 

In my tests, something like 600ft 500kts the impact point is so low the sight wouldn't even be visible, so it's literally guesswork using the dashboard as a fixed sight. 

Edited July 31, 2022 by Nealius

[jojo]

20 minutes ago, Nealius said:

Brochure numbers are minimum 200ft maximum 550kts (I think?). In DCS any drop below 500ft results in the rocket motors failing to ignite, and anything below 800-1000ft won't allow a proper vertical shot into the runway. 

Yes, the very low impact point is a thing on that kind of weapon. On M-2000C with BAP-100 this is a "delayed CCIP", where you have a delay between the moment you press the trigger and the bomb drop !

[chichowalker]

I have been dropping durandals at 500 kts, between 200-300 ft AGL and 140 depression. Up to now, always succesfull attacks.

Edited July 31, 2022 by chichowalker

[Frederf]

I have the actual specs somewhere. The worst case is low and fast which I remember as 250ft, 620 KCAS. There is a min speed based on arming mech and a too high height. Arming time is as near as I could reverse engineer 1.2 sec. Having the rockets swing vertical is a concern.

[jojo]

AFAIK, the vertical angle isn't mandatory nor necessary for the bomb to work.
If the rocket engine doesn't work, that is a real problem.
 

 

[Nealius]

6 hours ago, Frederf said:

Having the rockets swing vertical is a concern.

This is the part that gets me in DCS. You have to be at nearly 1000AGL at release in DCS to get the munition to swing vertical before firing the rockets.

[Glide]

We had these in Falcon4 before BMS removed them.  I recall you had to pop up to 1000agl or they wouldn't arm in time which made for some puckering moments.

[Nealius]

54 minutes ago, Glide said:

We had these in Falcon4 before BMS removed them.  I recall you had to pop up to 1000agl or they wouldn't arm in time which made for some puckering moments.

When were they removed? I remember using them in 4.32 and dropped at about 500' or less. 

[Frederf]

They still in. The Matra Durandal has a few versions. The USAF version can do 630 KCAS but the old one was limited 550 (600?) KCAS. Also the older (original) fired at a ~30° angle while the later USAF version fired at a steeper angle. The original had a lower 200 foot height minimum. There are two warheads a primary and secondary at 100kg and 15kg respectively.

The -109 sequence is: arming wire extraction, R1500 delay element, R350 delay, R2200 delay, rocket motor, impact, warhead detonation. Since the delay element time is about 77~86% of the "R" number I'm guessing the R1500 is about 1222ms. Arming is enabled after two of the delays so about 2000ms which is then followed by the extra swing down delay of 1700ms. I assume the Mirage F1 uses a non-BLU-109 design so they might be slightly different but the difference might just be the higher speed parachute and final swing delay to achieve the steeper angle.

Serial production 1977, 1983 initial USAF order, 1986 programmable secondary fuze offering (hours delay), 2005 production halted.

Anyway a grazing penetration produces the best runway-destroying effects as it heaves a larger area of runway surface. They aren't designed to make easily-filled circular bomb crater holes. They are designed to screw up a lot of pavement and make repair difficult. As long as they are rocket firing and hitting the ground at 30 degree from the horizontal down to 200ish feet that should be considered good.

[Nealius]

The 30° angle thing is a nice tidbit to know. I thought they were supposed to go straight down to make a deeper hole; deep hole = harder to fill was my logic but apparently that doesn't fit engineering logic lol.

[Glide]

10 hours ago, Nealius said:

I remember using them in 4.32 and dropped at about 500' or less.

You are correct.  I've spent maybe 1 hour in BMS.  Guess I wasn't looking hard enough.  There are some good youtube videos of the BLU-107 delivery from BMS.

[Automan]

Il 1/8/2022 at 06:07, Frederf ha scritto:

They still in. The Matra Durandal has a few versions. The USAF version can do 630 KCAS but the old one was limited 550 (600?) KCAS. Also the older (original) fired at a ~30° angle while the later USAF version fired at a steeper angle. The original had a lower 200 foot height minimum. There are two warheads a primary and secondary at 100kg and 15kg respectively.

The -109 sequence is: arming wire extraction, R1500 delay element, R350 delay, R2200 delay, rocket motor, impact, warhead detonation. Since the delay element time is about 77~86% of the "R" number I'm guessing the R1500 is about 1222ms. Arming is enabled after two of the delays so about 2000ms which is then followed by the extra swing down delay of 1700ms. I assume the Mirage F1 uses a non-BLU-109 design so they might be slightly different but the difference might just be the higher speed parachute and final swing delay to achieve the steeper angle.

Serial production 1977, 1983 initial USAF order, 1986 programmable secondary fuze offering (hours delay), 2005 production halted.

Anyway a grazing penetration produces the best runway-destroying effects as it heaves a larger area of runway surface. They aren't designed to make easily-filled circular bomb crater holes. They are designed to screw up a lot of pavement and make repair difficult. As long as they are rocket firing and hitting the ground at 30 degree from the horizontal down to 200ish feet that should be considered good.

Hi, IndiaFoxTechEco have officially introduced this common bomb (like BAT-120 and BAP-100) to the database, not Aerges: the bomb is platform independent, we have tested them with our MB-339, but the Mirage F1 is not different. So, the Durandal we have in DCS is based on BLU-107B (Durandal II) data: optimum profile is straight levelled at 250fts and fast (maximum 630kts). 
The braking force of the first chute (deceleration chute) is very strong and it will decelerate the bomb to 25m/s. At that speed it will detach and trigger the deployment of the 2nd chute (main chute) that will stay in position until the optimal angle to avoid ricochet is reached (almost 40°).
After that, the jettison of the chute will automatically ignite the rocket that will boost the bomb to 250m/s, a sufficient speed to penetrate 
In the eighties, a lot of testing were performed by USAF at Eglin to improve the original Durandal: the latest tests included dropping at 1000ft with F-16A, and others between 300 to 500ft with F-4D.
Even if Durandal have an internal altimeter to delay the rocket motor ignition (the boost will last only half of a second), the test for profile different from 250fts were 1 miss to 2 hits(66% reliability), significantly worse then the 96% performed with lower profile.
Considering that flight were performed levelled and straight over the runway, the miss occurred mainly for ricocheting (more height expose bombs to wind factor that can alter the optimal angle and/or due to not enough energy to penetrate the concrete in case of a premature rocket initiation) than for overshooting.

Actually the Durandal altimeter and fuzing delay is not emulated in DCS, and other effects should be adjusted later.
BTW, we hope you are enjoing this weapon, along the beautiful Mirage F1 introduced by our friends of Aerges.
Cheers.

[Frederf]

Far as I can tell -107 has no altimetry, just timed delays and deceleration sensors. Good gouge on that 2/3rds rate at marginal parameters

[Automan]

Yes, I would say the same reading the weapon scheme, but well... documentation of latest Durandal is frammented and sometime discordant (even from reliable sources...), so some assumptions were made.
As a prologue, the Red Flag ‘88 that involved runway denial missions with F-111 and Durandal, while performed well in flat desert with surprise effect, showed limitations in case the strike would occurs in areas not viable for low approach and high speed, like an airport with surrounding mountains or placed in a valley depression. So USAF ordered further testing on F-111 and Durandal II to achieve an alternative solution of employment.
The test flights occurred between 1988 and 1989 and since mentioned higher altitude profiles of up to 3000ft, we assumed a radar altitude device or a ground proximity sensor would be necessary to control the delay of the rocket motor to do the right job, like the design of BetAB-500ShP (russian Durandal with steroyds...) that when bomb reaches 150m AGL the rocket motor is fired. 
But we can only speculate about this, unless we have a reference of a USAF's weapon system specialist that manipulated them over 30 years ago.
By the way, the test were unsuccesful, with a lot of mishaps, ricocheting, half penetration and the reccomandation of 250ft and a maximum height below 1000ft was retained.

[DJBiscuit1818]

On 8/9/2022 at 6:03 PM, Automan said:

So, the Durandal we have in DCS is based on BLU-107B (Durandal II) data: optimum profile is straight levelled at 250fts and fast (maximum 630kts). 

Does anyone know if there's a sight depression that results in a good delivery with that profile?

[Automan]

Il 22/8/2022 at 20:07, DJBiscuit1818 ha scritto:

Does anyone know if there's a sight depression that results in a good delivery with that profile?

 

Il 31/7/2022 at 19:13, chichowalker ha scritto:

I have been dropping durandals at 500 kts, between 200-300 ft AGL and 140 depression. Up to now, always succesfull attacks.

 

Using this hint of chichowalker, I would say that with more than 500kts, a depression of 125 should be enough.

[Get_Lo]

you can make your own table using active pause in singleplayer, get the speed and altitude you want and then active pause and drop. adjust the sight to match the impact point and record the value.

[Dragon1-1]

On 8/1/2022 at 4:07 PM, Glide said:

You are correct.  I've spent maybe 1 hour in BMS.  Guess I wasn't looking hard enough.  There are some good youtube videos of the BLU-107 delivery from BMS.

Only certain F-16 blocks carry them IRL, and the other sim reflects that. As does DCS, since the F-16 that we have is not one of those blocks.

[sasquatch98]

On 8/22/2022 at 1:07 PM, DJBiscuit1818 said:

Does anyone know if there's a sight depression that results in a good delivery with that profile?

I did some experimenting and a depression of 110 works really well between 250-300 ft and around 550 knots.