F16 Nozzle position Schedule

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leonidasth

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Unread post07 Apr 2019, 00:18

Greetings ,
My name is Leonidas and I am a Mechanical Engineering student. I started my thesis on the F110 and F100 engines that power the F16 fighter jet. I need to create a model that calculates with precision the performance parameters of these engines at any given conditions. I am missing some vital information though and I would like to ask you the following questions.
1) Does anyone know what the Nozzle position schedule is or the exact position of the nozzle for different PLA inputs?
2)Is the connection between the PLA and the fuel mass flow linear?
Thank you.
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f119doctor

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Unread post09 Apr 2019, 21:10

For the F100 engine (can't speak for the F110), the major throttle positions (Power Lever Angle - PLA) are:
0 degrees - cutoff
16 degrees - Idle
86 degrees - Intermediate or Military
91 degrees - Min AB
130 degrees - Max AB

With the landing gear handle down, the nozzle is open to approximately 80% - 90% at Idle. It ramps closed to approximately 10% open as the throttle is advanced to 50 degrees. It stays fixed at the 10% open position as the throttle is advanced toward Intermediate. With the landing gear handle up, the nozzle stays at that 10% position all the way down to Idle.

At around 80 degrees PLA to Intermediate, the -220 and -229 engines pick up a Fan airflow vs Engine Pressure Ratio (EPR) schedule that trims the nozzle position slightly up or down from that 10% nominal number, but it will stay in the 5% to 15% range under normal conditions. The -100/-200 engines trimmed nozzle position to maintain a N1 fan speed to N2 core speed ratio at Intermediate and above, with similar nozzle position results.

In AB, the nozzle opens on a nominal AB fuel flow to nozzle position schedule. At Min AB, the nozzle opens to around 15 - 20%, then continues to open to 70 - 90% as the PLA is advanced to Max AB, depending on flight conditions and engine model. This nozzle position is trimmed from that nominal schedule to maintain the N1 to EPR schedule (-220 and -229), or to maintain the N1 to N2 schedule (-100 and -200)

In backup control mode (-200 BUC, -220 & -229 SEC), the nozzle is fully closed all the way to the minimum 0% to -2% from Idle to Intermediate. For the -220 and -229, AB is inhibited in SEC regardless of PLA position. In the -200, the pilot was prohibited from using AB, since moving the PLA into AB would still get AB fuel flow and ignition but the nozzle would remain closed and the engine would immediately stall. The SEC system on the -220/-229 is 1000% better than the BUC system on the -200 for this reason and many more.

For you last question, the engine schedule is intended for a relatively linear relationship between PLA and thrust at any particular flight condition. Fuel flow is whatever it has to be (within the engine operability and durability limits) to make that happen. Fuel flow does increase with increased PLA, but it is not linear. The -100 / -200 engines schedule core fuel flow against a Core N2 schedule, with the EEC supervisory control trimming that core fuel flow to achieve the desired N2 speed and FTIT turbine temperature, while trimming nozzle position to achieve the desired N1 speed. The -220 and -229 engine DEEC full authority electronic control schedules fuel flow to achieve the desired N1 fan speed at any commanded PLA position (while respecting the N2 core speed, temperature, and operability limits), and trims nozzle position to achieve the desired EPR for that N1 fan speed near Intermediate and in AB.
P&W FSR (retired) - TF30 / F100 /F119 /F135

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