Error Budget

Question 1

Define Error Budget

Answer 1

Error Budget is the influence of the hardware, environmental conditions and human factors that affect accuracy and consistency.

Question 2

3 Major Categories of Error Sources

Answer 2

1. Fixed Bias
2. Variable Bias
3. Random Error

Question 3

Define Fixed Bias

Answer 3

Errors induced by ammunition, weapon, and fire control system that at any given range will cause a round to miss the desired aiming point predictably.

Question 4

3 Types of Fixed Bias

Answer 4

1. System Parallax
2. Ballistic Drift
3. Mean Jump

Question 5

(Fixed Bias)
Define System Parallax

Answer 5

System Parallax is the difference in position between the axis of bore, and the line of sight for each sight.

Question 6

(Fixed Bias)
What compensates for System Parallax

Answer 6

Proper boresighting, which establishes a relationship between the axis of the bore and aiming marks of the sight at a range appropriate to the equipment.

Question 7

(Fixed Bias)
Define Ballistic Drift

Answer 7

Drift is the lateral deviation from the line of trajectory (AOB) due to the spinning of the projectile- and the buildup of air pressure around the projectile nose (ogive).

Spin stabilized projectiles will drift in the same direction as the spin caused by the rifling of gun.

The largest contributing factor causing drift is rifling.

Question 8

(Fixed Bias)
What compensates for Ballistic Drift

Answer 8

The fire controllercalculates a correctionbased on ammo type andrange to target.

Question 9

(Fixed Bias)
Define Mean Jump

Answer 9

The average difference between the actual impact of a group of rounds fired over many occasions and the intended strike of those rounds, given that all inputs to the FCS are correct or within tolerances.

Question 10

(Fixed Bias)
What accounts for Mean Jump?

Answer 10

It is accounted for by zeroing

Question 11

Define Variable Bias

Answer 11

Error sources whose value remains nearly constant when firing one type of ammunition at a particular target at a given range (single engagement), but can change considerably from one engagement to the next

Variable biases are the major contributing factor effecting accuracy and will move the mean point of impact unpredictably.

Question 12

11 Types of Variable Bias

Answer 12

1. Boresight and Boresight Retention
2. Cant
3. Crosswind
4. Fire Control
5. Air Density
6. Ballistic Solution
7. Muzzle Velocity Variation
8. Range Estimation
9. Optical Path Bending
10. Variable Jump
11. Zeroing Errors

Question 13

(Variable Bias)
3 Causes of Boresight / Boresight Retention Errors

Answer 13

1. Tolerances in the muzzle boresight device (MBD)
   -An MBD is an optical instrument used to accurately define the axis of the bore (AOB) of a gun at the muzzle end.
2. Round-off in splitting the means
3. MBD operator and gunner not sighting on the same aim point.

Question 14

(Variable Bias)
Correction for Boresight / Boresight Retention Errors

Answer 14

Training

Question 15

(Variable Bias)
What causes Cant?

Answer 15

Trunnion Tilt (cant) occurs when the vehicle is on a side slope (one trunnion is higher than the other). If this occurs and only quadrant elevation is applied to the gun, a line error will occur.

Question 16

(Variable Bias)
Effect of Cant on the projectile

Answer 16

When cant occurs and is not corrected the round will impact low and in the direction of the cant (downhill side of the trunnion).

Question 17

(Variable Bias)
Manual Correction for Cant

Answer 17

Sabot- No correction (due to the extreme speed)

Slower rounds- Hold ½ target form uphill (against the direction of cant) in azimuth only.

Question 18

(Variable Bias)
Define Crosswind

Answer 18

Crosswind is air turbulence (wind) traveling across the Axis of Bore (AOB) which can force a projectile off its intended trajectory.

Question 19

(Variable Bias)
Correction for Crosswind

Answer 19

MET Data collection sensor integrated into the FCS

Question 20

(Variable Bias)
Define Fire Control

Answer 20

Errors and stresses of both a physical and environmental nature applied to various components of the fire control system.

Question 21

(Variable Bias)
3 Types of Fire Control Errors or Stressors

Answer 21

1. Metal Fatigue
2. Design Tolerances
3. Vehicle Vibrations

Question 22

(Variable Bias)
Fire Control

Define Metal Fatigue

Answer 22

Metal Fatigue - Consists of Thermal Bending and Gun Tube Droop

-Thermal bending is uneven heating and cooling of a warm or hot barrel. It can be caused by cold wind or rain striking one side of the barrel, with the result that one side cools more quickly than the other.

-On Stryker platforms, thermal bending is prevented by a thermal shroud which provides evenly distributed heating and cooling (MCWS), or compensation is not required due to barrel swapping and inherent design (i.e. M2, MK 19).

Question 23

(Variable Bias)
Fire Control

Define Design Tolerances

Answer 23

Everything within our platforms is built within a tolerance window. Fire Control systems are designed to make inherent corrections for within these tolerance windows.

Corrected by PMCS

Question 23

(Variable Bias)
Fire Control

Define Gun Tube Droop (Gravitational Bending)

Answer 23

-Gun Tube Droop (Gravitational Bending) is caused by gravity acting on the gun and can disturb the gun-sight relationship established through boresighting.

-Gravitational pull of the gun tube downward due to length and weight.

-On Stryker platforms, gun tube droop is mitigated by fluting in the barrel which reduces weight and expedites cooling (MCWS), or barrel swapping.

Question 24

(Variable Bias) Fire Control Correction for Vehicle Vibrations

Answer 24

For design tolerances and vehicle vibrations proper PMCS is the only way to identify, troubleshoot, repair, and mitigate equipment that has been adversely affected during use or exposure to the elements.

Question 25

(Variable Bias) Define Air Density

Answer 25

Air density is the weight of a certain volume of air reflecting moisture content, air temperature, and barometric pressure. Air density affects the ballistic characteristics of the projectile during flight in the external ballistic phase.

Question 26

(Variable Bias) What affects Air Density

Answer 26

-Temperature: cool air = more dense / warm air = less dense -Humidity/moisture: More moisture = more dense / dry air = less dense -Your altitude Higher Altitude = less dense / Lower Altitude = more dense -Barometric Pressure Higher Pressure = more dense / Lower Pressure = less dense

Question 27

(Variable Bias) Define Ballistic Solution

Answer 27

Errors associated with calculating a ballistic solution based on incorrect information applied to the computer by the crew or by automatic inputs

Question 28

(Variable Bias) What are 6 sources of Ballistic Solution Errors

Answer 28

1. Incorrect Ammunition Selected 2. Incorrect Range Determined 3. Undetected Failure of an automatic input 4. Incorrect individual zeroing procedures 5. Incorrect manual input to the FCS 6. Incorrect ammunition subdesignated

Question 29

(Variable Bias) What is the correction for Ballistic Solution Errors?

Answer 29

Training

Question 30

(Variable Bias) Muzzle Velocity Variation

Answer 30

Changes in the velocity of the projectile due to characteristics of the ammunition or weapon.

Question 31

(Variable Bias) 4 Causes of Muzzle Velocity Variation and their Corrections

Answer 31

1. Propellant Temp-Manual Input 2. Change in load density-Firing Table inputs from FCS 3.Tube Length-Proper Maintenance 4. Damaged Rifling-Proper Maintenance

Question 32

(Variable Bias) Range Estimation

Answer 32

Errors associated with incorrect determination of a range to a specific point. Range is the most important element of a ballistic solution.

Question 33

(Variable Bias) Optical Path Bending

Answer 33

The apparent difference between the target’s perceived location and its actual location due to refraction caused by reflection of emitted heat radiation.

Question 34

(Variable Bias) Optical Path Bending Correction

Answer 34

Day Conditions: - Aim one and a half target form high. Night Conditions: - Aim one and a half target form low.

Question 35

(Variable Bias) Variable Jump

Answer 35

Variable jump is the difference between the actual impacts for a particular occasion and the intended point of impact of those rounds, given that all inputs to the FCS are correct or within tolerance.

Question 36

(Variable Bias) Correction for Variable Jump

Answer 36

Perform standard sight adjustments after subsequent round misses

Question 37

(Variable Bias) Zeroing Errors Correction

Answer 37

Training

Question 38

2 Types of Random Error

Answer 38

1. Round to Round Dispersion 2. Gunner Lay Error

Question 39

Define Random Error

Answer 39

These are error sources that vary from each round fired that can not be predicted from one round to the next nor can the crew compensate for them. Can affect both accuracy and consistency

Question 40

(Random Error) Round to Round Dispersion

Answer 40

This refers to the spread between the points of impact of two or more rounds in relation to the Mean Point of Impact (MPI) when fired under identical conditions.

Question 41

(Random Error) Factors that affect Round to Round Dispersion

Answer 41

Crosswind Thermal Bending The lot of ammunition

Question 42

(Random Error) Gunner Lay Error

Answer 42

Gunner lay error occurs when the gunner fails to make a correct lay to the target aiming point. Gunners must be trained to lay the aiming point on the target, with elevation being the last movement of the sight. This action is a movement of the sight that looks like a "G" pattern.

Question 43

(Random Error) Factors Affecting Gunner Lay Error

Answer 43

-Identifying the center of the target -Laying reticle on the center of the target -Optical path bending -Parallax caused by the operator's eye not being rigidly located as part of the sight. -Firing too quickly Firing too quickly due to criticality of time when sight picture is incorrect (pulling up on control grip)

Question 44

(Random Error) Correction for Gunner Lay Error

Answer 44

Training