Example adjustment factor for mission profile tasks

This example defines a condition that if the total readings for all mission profile meters equal the total flight hours for the aircraft, task frequencies are recalculated. The recalculation formula multiplies each meter reading by a coefficient that is specific for that mission profile type. Also, task frequency is adjusted based on the relative time that is spent during each phase of the mission.

The formula for recalculating frequencies based on mission profile meter readings includes the ratios that apply for each mission profile type. In this example, the aircraft has the following mission profile types:
  • Long logistical
  • Short logistical
  • Tactical
  • Training
In the Meters application, the following mission profile meters are configured:
  • LL meter records readings for the long logistical type of mission profile.
  • SL meter records readings for the short-logistical type of mission profile.
  • TA meter records readings for the tactical type of mission profile.
  • TR meter records readings for the training type of mission profile.
Standard ratios of mission profile types for a mission are defined. For a typical mixed mission, the following ratios are applied to mission profile meter readings:
  • LL = 0.2325
  • SL = 0.4425
  • TA = 0.2
  • TR = 0.1250
All inspections have initial threshold and interval values that are based on the worst-case scenario for a mission. The following values are the initial frequencies for the task:
  • Threshold = 2935 flight cycles
  • Interval = 1505 flight cycles
When the aircraft completes a mission, if the total time recorded on mission profile meters does not equal the total flight hours for the aircraft, the initial threshold and interval values apply. The total time that is recorded on mission profile meters is the same as the total flight hours for the aircraft. Then, task frequencies are recalculated to allow for the relative time spent in each phase of the mission.

Each mission profile type has coefficients for thresholds and intervals. The coefficient is the multiplier that is applied to readings from the corresponding mission profile meters in the adjustment formula. The following table lists the coefficients to apply for each mission profile type.

Table 1. Example threshold and interval coefficients for mission profiles
Mission profile Threshold coefficient Interval coefficient
Long logistical (LL) 1.000 0.2644
Short logistical (SL) 0.3878 1.000
Tactical (TA) 0.6783 0.3711
Training (TR) 0.3775 0.1894

The calculation to determine the threshold adjustment factor is 1/((0.2325*1)+(0.4425*0.3878)+(0.2*0.6783)+(0.1250*0.3775)), which results in a threshold adjustment factor of 1.7037. When this adjustment factor is applied to the initial threshold, 1.7037*2935, the threshold for the next inspection is adjusted to 5000.3595, which is rounded to 5000 flight cycles. The calculation to determine the interval adjustment factor is 1/((0.2325*0.2644)+(0.4425*1.0000)+(0.2* 0.3711)+(0.1250*0.1894)), which results in an interval adjustment factor of 1.6615. When this adjustment factor is applied to the initial interval, 1.6615*1505, the interval for the next inspection is adjusted to 2500.5575, which is rounded to 2500 flight cycles.

The following table shows that frequency values are adjusted based on the condition that all mission profile meter readings are equal to the total flight hours recorded for the flight. If the condition is not met, frequency values are reset to initial values.

Table 2. Example adjustment factor for mission profiles
Adjustment factor Condition Formula
1 [FH] = ([LL]+[SL]+[TA]+[TR]) 1/((([LL]/[FH])*1)+(([SL]/[FH])*0.3878)+(([TA]/[FH])*0.6783)+(([TR]/[FH])*0.3775))