How to - Performance Management System (PMS)

mattY · Tuesday at 11:30 AM

The TriStar’s Performance Management System (PMS) provides real-time calculations for thrust settings, fuel predictions, and vertical flight profiles across all phases of flight.

Unlike modern FMCs, the PMS operates through a structured page system, requiring manual data entry and validation to generate accurate performance outputs.

(Click to enlarge image)

Data Entry – General Procedure

Navigate to desired page
Press softkey on left corresponding to line to be modified
Verify field clears and INSERT button illuminates
Enter value using right keypad (observe correct format, decimals, signs)
Verify entered value
Press INSERT (light extinguishes)
Use CLR to cancel / start over if needed

Note: Entering an empty value usually exits entry mode without saving.

Step 1 – TAKEOFF Page

First page displayed after pressing PERF MGT.

Enter / verify (values often persist from previous flight – always check):

GMT – Zulu time (HHMM) at initialization - Should be modified for estimated takeoff time
EPR – Computed from pressure altitude (after all parameters are inserted)
PR ALT – sensed by ADCs (not entered)
GW – Gross weight in thousands of lb (round up to nearest 1,000 lb)
FUEL – Fuel weight in thousands of lb (decimal shown automatically)
SAT – Static Air Temperature (°C); enter sign first if negative

Once all values are entered with valid values the PMS will calculated the optimum takeoff EPR value and will display it in the EPR line

Note: SAT valid range for EPR calc is –20 °C to +54 °C. Out-of-range values are clamped. Fuel value is limited to three digits, so you can enter decimals if the value is below 100.

E.G. 85.700 would be 85.7. Otherwise, you must round up the value. For example, 155.200 pounds would be rounded up to 1560.

Step 2 – FLIGHT SETUP Page

Navigate using AFT / FWD keys
Initial performance modes (most economical and only current availables modes):
- CLIMB: OPTIMUM / 250 kt
- CRUISE: 3 ENG CRZ STD
- DESCENT: OPTIMUM / 250 kt
Enter BOD (Bottom of Descent) data:
- BOD DIS – distance to descent point (NM)
- BOD ALT – altitude at BOD (ft)
- BOD SPD – speed at BOD (kt)

Recommendation: Update BOD values enroute after INS is aligned for better accuracy.

Step 3 – TAXI & TAKEOFF (Update GW)

Return to TAKEOFF page
Update GW (subtract taxi fuel burn)
Leave page open during takeoff and initial climb for monitoring

Step 4 – CLIMB Page

Automatically displayed after takeoff or by selecting first line on FLIGHT SETUP.

Displayed values include:

CLB – IAS targets (below 10,000 ft / intermediate / high-alt Mach×100)
EPR – min & max
ALT – selected cruise altitude (FL) – must be entered
OPT – computed optimum cruise altitude
TOC – distance & time to Top of Climb
CLB MANUAL ? - Erase speed portion on CLB line and allows to change it, then the PMS will adjust climb rate to match that airspeed using the OPT EPR value.
SAT - Static air temperature in C degrees
TAS - True air speed in knots

Step 5 – CRUISE Page

Displayed values include:

CRZ - Mach and IAS target - opens CRUISE sub-page
FUEL REM - Remaining fuel in thousands of pounds
ALT - Selected cruise altitude
OPT - Optimum cruise altitude
STEP - TBD - opens STEP DATA sub-page
TOD - DIstance in NM and Time zulu to the top of descent - opens TOD sub-page
SAT - Static air temperature in C degrees
TAS - True air speed in knots

Engagement procedure (especially after VNAV/TM interruption):

Set AFCS pitch mode to ALT HOLD
Press PERF MGT → select CRUISE page
Press TM button (light on) + set ATS to ON
Verify AFCS mode changes to THR MGT
Adjust EPR manually if necessary
Confirm Mach target is maintained

Typical values (STD cruise): 0.830 M / 285 KIAS

CRUISE sub-page (press CRZ line):

3 ENG CRZ STD → 0.830 / 285
3 ENG CRZ LRC → long-range cruise (see tables – pending)
3 ENG MANUAL → allows direct Mach/IAS entry

STEP DATA sub-page:

WIND - Current wind velocity and direction
CLB - Distance in NM and Time zulu at the beginning of the step-climb to STEP ALT
STEP ALT - Step climb altitude in 4000ft increments
FUEL SAVE - Total fuel save or lost by climbing to the STEP ALT compared to present altitude
NEW ALT SAT - Assumed SAT at STEP ALT using non-standard ISA values
SAT - Static air temperatures in C degrees
TAS - True air speed in knots

TOD sub page:

In the CRUISE page, press TOD line and the DES BOD page will be displayed with the following information:

DES - Mach, airspeed above 10000ft and airspeed below 10000ft
BOD - Distance in NM and Time zulu to BOD
BOD ALT - Desired altitude in ft at BOD
BOD SPD - Desired speed (IAS) in knots at BOD
TOD - Distance in NM and Time zulu to reach TOD
SAT - Static air temperature in C degrees
TAS - True air speed in knots

STEP 6 - DESCENT

To start a descend, the operator should follow the next procedure:

Select the desired altitude on the glareshield panel
On the PMS go to the CRUISE page and update the ALT value to this new altitude and press insert
Press VNAV mode and check ATS and TM are engaged too

If the descent is started at any moment of the flight up to 10 minutes before TOD, the following page will be displayed:

DES - Descent profile with Mach and flight level
ALT - Selected altitude and optimum cruise altitude
SAT - Static air temperature
TAS - True air speed

Once the aircraft reaches the desired altitude, it will resume the cruise mode and CRUISE page will be displayed

If the descent is started within 10 minutes before TOD, the page will be slightly adjusted to show "DES OPT (DIST)NM":

Page title - Distance in NM (could be positive or negative including the (-) sign) where the aircraft will reach BOD altitude relative to the its waypoint position (could be before or after the actual BOD)
DES - Descent profile with Mach, airspeed above 10000ft and airspeed below 10000ft
BOD - Distance in NM and Time zulu to BOD
BOD ALT - Desired BOD altitude
BOD SPD - Desired BOD speed
SAT - Static air temperature in C degrees
TAS - True air speed in knots

STEP 7 - Landing

After descent phase and once BOD altitude is reached, the LANDING DATA page is displayed:

VTH - Indicated airspeed at threshold
GA EPR - Go-Around calculated EPR
PR ALT - Current pressure altitude
GW - Computed gross weight
GS - Ground speed
FUEL - Computed remaining fuel
SAT - Static air temperature in C degrees
TAS - True air speed in knots

Operation Notes:

BOD DIS is the distance between the aircraft position at the moment the data is entered and the point where the user intends to complete the descent.

It is strongly recommended that this point be the last waypoint of the flight plan entered in the INS, in order to obtain the along-route distance between the current aircraft position and the BOD.
BOD ALT is entered in feet, not in Flight Levels (FL).

The value must be entered directly; for example, an altitude of 3,000 feet must be entered as 3000.
The BOD line on the DES BOD OPT page displays the distance and estimated time of arrival at the BOD, calculated based on groundspeed and the distance traveled as a function of groundspeed.
It is important to note that if BOD DIS is entered incorrectly, the BOD estimates will not be coherent, since all horizontal and vertical VNAV profile calculations are based on this distance.
During OPT (standard) descent, an airspeed setpoint of 250 knots must be used.
Each time a BOD value is entered or modified (DIS, ALT, or SPD), the system resets the distance-traveled estimation.

This is done to recalculate BOD DIS and ensure that all estimates remain accurate.
On the CLB OPTIMUM, 3ENG CRUISE STD, and ENROUTE DESCENT pages, the ALT value can be read and updated.

This value is expressed in Flight Levels (FL) and is used by the system to calculate the difference between the current altitude and the BOD altitude.
The system dynamically calculates the required descent distance, descent time, and required vertical speed, using a dynamic method similar to the 1:4 rule.
Considering the previous point, if the distance required for the descent maneuver exceeds the BOD distance, the system will not be able to correctly compute the descent profiles.

To verify this condition, it is recommended to check and compare BOD and TOD, ensuring that a TOD distance exists and that the distance to BOD is greater.

The difference between these two values represents the distance allocated for the descent (this applies only if the TOD distance is greater than zero).

(Click to enlarge image)

Important Notes for Descent:

To initiate a correctly computed descent profile, you must keep the cruise ALT value unchanged (the value entered on the CLB or CRZ page). The PMS calculates the required descent altitude difference (and therefore the TOD/BOD distances and required VS) based exclusively on the difference between cruise ALT and BOD ALT.

If you manually change the ALT value to match the BOD ALT (or set both to the same altitude), the system will detect zero altitude difference. As a result:

Descent distance becomes 0
The required descent VS becomes invalid
The TOD and BOD predictions will be incorrect or show as zero

Recommendation: Leave the cruise ALT exactly as it was set during climb/cruise planning. Only enter or modify the BOD ALT when you want to start the descent profile. The cruise ALT must remain the original reference altitude for the calculation to work correctly.

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How to - Performance Management System (PMS)

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