Long Range Tank Gunnery -- Again

[DB]

I find Arrow's data to be very interesting, but it confuses me, because I would have expected mechanical differences between vehicles to dominate. Either manufacturing tolerances are much higher than I would have expected, and don't change much over time due to wearing, etc., or I'm missing something.

 

Do the vehicles in your tests get re-calibrated in terms of turret position and gun elevation sensors, and what about FCS to gun boresighting?

 

David

[jwduquette1]

Yes, see my statement in post #97:

The fleet zero used at the firings was a rough estimation, which has to be tuned to the actual fleet zero.

For the comparison of different tank gun calibration policies, I posted in this thread with post #21 of 25 June 2006 a statistic model and the standard-deviations for the calculation of hit-likelihoods with one round, under the assumption that MPI is identical to the aiming point.

 

For fleet zero of modern tanks and APDSFS these standard deviation for a single round (sr) is:

 

s_sr = sqrt(s1^2+s2^2+s3^2)

std dev in height = sqrt(0.10^2+0.15^2+0.20^2) = 0.27 mils

std dev in azimuth = sqrt(0.05^2+0.10^2+0.20^2) = 0.23 mils

 

Good correspondence with the Swiss trial (0.26 resp 0.24mils)!

 

The standard deviation of the investigated fleet zero correction – i.e. with the 24 Swiss tanks and one round per tank – can be estimated with the following formula (individual for height and azimuth):

 

s_fz = sqrt(s1^2/n1 + s2^2/n1/n2 + s3^2/n1/n2/n3)

 

n1 = number of involved tanks

n2 = number of firings per tank

n3 = number of rounds per tank and firing

 

Swiss trial:

 

n1 = 24  /  n2 = 1  /n3 = 1

 

height: s_fz = 0.055

 

azimuth: s_fz = 0.047

 

You see, with only 24 tanks and one round per tank we got a very good estimation for the fleet zero correction.

 

Regards

360670[/snapback]

 

Thanks Willi. Very helpful as usual.

[arrow]

I find Arrow's data to be very interesting, but it confuses me, because I would have expected mechanical differences between vehicles to dominate. Either manufacturing tolerances are much higher than I would have expected, and don't change much over time due to wearing, etc., or I'm missing something.

Hi David:

 

Did you read the article "New tank Gun Calibration Policy - Armor July-August 1982"? Probably not. See my post #90 in this thread.

Mechanical differences between the tanks don’t dominate. The MPI of an individual tank changes relativly fast in dependence of the time. You can see this in the following graph:

 

 

The circles show the individual zeroings of 147 Swiss Leopard 2 with 5 MP rounds. With 4 tanks we repeated the zeroing weekly. The results are plotted with colored symbols. Per tank the symbols are joined with lines in the chronological sequence.

 

Do the vehicles in your tests get re-calibrated in terms of turret position and gun elevation sensors, and what about FCS to gun boresighting?

The only thing we did on the firing range was boresighting with a muzzle boresight device. The tanks had no fire control computer.

 

Willi

[jwduquette1]

Hi David:

 

Did you read the article "New tank Gun Calibration Policy - Armor July-August 1982"? Probably not. See my post #90 in this thread.

Mechanical differences between the tanks don’t dominate. The MPI of an individual tank changes relativly fast in dependence of the time. You can see this in the following graph:

 

 

The circles show the individual zeroings of 147 Swiss Leopard 2 with 5 MP rounds. With 4 tanks we repeated the zeroing weekly. The results are plotted with colored symbols. Per tank the symbols are joined with lines in the chronological sequence.

 

The only thing we did on the firing range was boresighting with a muzzle boresight device. The tanks had no fire control computer.

 

Willi

361329[/snapback]

 

Excellent post Willi. Thanks again.

 

A number of reports were written by Aberdeen on the effects of the amount of time involved in conducting lot acceptance testing shoots. Moreover, one of the acceptance criteria of any lot of tank ammunition is of course keyed to the amount of inherent shot dispersion. A particular lot must not exceed a certain level of dispersion – per the appropriate manufacturing specifications for the round of interest. The greater the amount of time required in conducting the acceptance shoots, the greater the typical shot dispersion and the greater the potential for out right lot rejection if maximum acceptable dispersion was exceeded.

 

Best Regards

[DB]

Hi David:

 

The only thing we did on the firing range was boresighting with a muzzle boresight device. The tanks had no fire control computer.

 

Willi

361329[/snapback]

Thanks, Willi.

 

I did read the paper, a while ago. Whether I took it all in and whether I remember it all now are different matters, of course.

 

I think I'd also misunderstood the way that the fleet zero was established - I'd assumed that it was propagating the corrections provided by a single extensively tested vehicle across the fleet, rather than using a single shot (or a small sample, perhaps) from each vehicle.

 

Would this method work with a mixed age fleet, though - vehicles with a lot of rounds fired would be likely to belong in a different set from new vehicles, surely?

 

David

[arrow]

I think I'd also misunderstood the way that the fleet zero was established - I'd assumed that it was propagating the corrections provided by a single extensively tested vehicle across the fleet, rather than using a single shot (or a small sample, perhaps) from each vehicle.

Hi David:

For establishing a reasonable fleet zero correction it makes sense to determine the correction as a mean value of firing results of 20 to 30 tanks of the fleet with 2 to 3 rounds per tank. To investigate the fleet zero correction for the whole Swiss fleet Leopard 2, which consisted of 380 tanks, we fired with 22 tank 3 rounds of each type (DM18, DM23, DM33 and DM53).

Would this method work with a mixed age fleet, though - vehicles with a lot of rounds fired would be likely to belong in a different set from new vehicles, surely?

Our Leopard 2 fleet is not a mixed age fleet. But our Pz68 fleet consisted of 4 lots with very different ages. The fleet zero correction was for all lots the same although there were two different size of turret. But the gun system wasn’t modified. Pz68 is no longer in use.

 

Willi