Continuing with our exploration of MDE Semiconductor, Inc. TVS semiconductor devices used in military applications, today we’re digging into the specific application of devices within the F135 turbofan. This is an afterburning turbofan developed by American aerospace manufacturer Pratt & Whitney. It has specifically been designed for the Lockheed Martin F-35 Lightning II strike fighter.
Our MAX-100, MAX-422, 30KW60CA, and 20KP30CA devices are those integrated for ESD protection of the F135. Let’s have a closer look at each of these devices’ roles in protecting equipment on board the F-35 Lightning II.
What is the F135?
The F135 is an afterburning turbofan designed by American aerospace manufacturer Pratt & Whitney. The afterburner’s job is to give the plane’s take-off a boost of extra thrust for a short period of time. This improves the aircraft’s ability to climb during take-off or combat. The F135 produces around 40,000 lbf of thrust.
There are two variants of the F135, developed for the single-engine strike fighter, the Lockheed Martin F-35 Lightning II:
- Conventional Take-off and Landing (CTOL)
- Short Take-Off Vertical Landing (STOVL)
CTOL is used in the F-35A and F-35C, while STOVL is used in the F-35B, which includes a forward lift fan.
“One of the many aspects that sets the F-35 above the rest is its Pratt & Whitney F135 engine, which utilizes cutting-edge technologies – many of which are designed and manufactured by Canadian companies – to provide a step change in performance, safety, and reliability over 4th generation fighter engines.” 
How are TVS Semiconductor Devices Playing a Role?
MDE Semiconductor, Inc.’s devices play their role within the Ultra Electronics Ice Protection System.
A plane’s turbine engine must have some sort of protection against ice forming within the inlet. There must also be a way of removing any ice that does form. That’s where Ultra Electronics & Plextek stepped in.
The partnership’s innovative new Ice Protection System is hard at work within the F135.
“The efficient and effective removal of airframe/engine ice is critical to the performance and flight safety of an aircraft. The system that Plextek assisted Ultra Electronics Controls in developing adheres to the DAL-A safety specification; the highest level possible. The system is designed to operate in either an anti-icing, de-icing or hybrid mode and caters to a range of ice protection requirements; from simple, time/voltage, on-off control through to very complex multi-zone, closed loop feedback control.” 
And to ensure the Ice Protection System can function properly, MDE Semiconductor, Inc.’s TVS semiconductor devices are in place to prevent power anomalies from shutting the whole system down.
As with any microprocessors connected to complex electrical and data networks, one problem is their sensitivity to unexpected and fast electrical transients which can damage their components. Transients are unpredictable and can propagate from external terminals. Transients can also be induced by lightning. Electrical anomalies can lead to complete failure of the circuitry, not to mention damaging the equipment altogether. Given the role ice protection systems must play in the event of bad weather during flights, any such occurrences could be catastrophic.
As a result, circuit protection from transients is a priority. The measure typically taken to prevent such disaster is to use a TVS Semiconductor Diode, or TVS Diode, in the circuit. And that’s exactly what’s going on within the Ultra Electronics Ice Protection System within the F135 turbofan.
Gareth Williams, Director, Digital & Analogue at Plextek explains,
“The biggest challenge in designing technology for the aerospace industry is conforming to the understandably strict safety requirements – if the ice protection system fails the results could be catastrophic and this is why we’ve worked hard to meet the DAL-A level of safety specification.” 
How a TVS Semiconductor Diode is Effective in Protecting Sensitive Electronics
TVS Diodes make an attractive choice for protecting critical electrical components for many reasons:
- They respond almost instantaneously (picoseconds) to transients.
- TVS Semiconductor Diodes have high impedance, so they act like open circuits during normal operating conditions (have low current leakage).
- They do not degrade, provided they are operated within the limits for which they are designed.
- They are manufactured in a variety of surface and through-hole circuit mounting options, making them perfect as board level protectors.
- TVS Diodes have low clamping voltages, making them ideal for sensitive circuits operating at low voltages (e.g., microprocessors).
- They also protect circuits from Electrostatic Discharge (ESD)
A TVS semiconductor relies on “the avalanche effect” to protect circuits from transient voltages.
The excess transient current is diverted from the protected circuit and flows through the Transient Voltage Suppressor Diode to ground. When the voltage across the circuit exceeds the Breakdown Voltage of the TVS Diode, the diode clamps the excess voltage, allowing the protected circuit to operate safely.
Which MDE Semiconductor, Inc. Devices Are Used in the Turbofan?
Our MAX-100, MAX-422, 30KW60CA, and 20KP30CA devices are those integrated for protection of the F135 turbofan.
The MAX-100 High Current Transient Voltage Suppressor is bi-directional with excellent clamping capability and sharp breakdown voltage. It has a 10kA surge capability at 8×20 µsec waveform (per IEC- 61000-4-5). It’s peak power dissipation is 144KW, and it boasts a fast response time: typically less than 1.0 µs from 0 Volts to BV. (https://secureservercdn.net/18.104.22.168/az2.5b0.myftpupload.com/wp-content/uploads/2017/08/MAX-100-8-16-17.pdf)
The MAX-422 High Current Transient Voltage Suppressor is bi-directional with excellent clamping capability and sharp breakdown voltage. It has an 8kA surge capability at 8×20 µsec waveform (per IEC- 61000-4-5). It’s peak power dissipation is 1288KW, and it boasts a fast response time: typically less than 1.0 µs from 0 Volts to BV.
The 30KW60CA Glass Passivated Junction Transient Voltage Suppressor has a 30000W Peak Pulse Power capability on 10/1000 µs waveform. Peak pulse current is 297.1 IPP (A). It’s repetition rate is 0.05% and has low incremental surge resistance. It’s reverse standoff voltage is 60.00, breakdown voltage is 67.00 VBR (V) MIN, and reverse leakage of 15 @ VRWM IR (µA). As with previous devices, the 30KW60CA TVS semiconductor has excellent clamping capability and a fast response time: typically less than 1.0 ps from 0 volts to BV.
The 20KP30CA Glass Passivated Junction Transient Voltage Suppressor has a 20,000W Peak Pulse Power capability on 10/1000 µs waveform. Peak pulse current is 392.2 IPP (A). It’s repetition rate is 0.05% and has low incremental surge resistance. It’s reverse standoff voltage is 30.00, breakdown voltage is 33.51 VBR (V) MIN, and reverse leakage of 250 @ VRWM IR (µA). As with previous devices, the 20KP30CA TVS semiconductor has excellent clamping capability and a fast response time: typically less than 1.0 ps from 0 volts to BV.
Praise & Progress for the F135 Engines
The first F135 engines were rolled out for testing and use starting around 2009. Trouble within the engine turbines was revealed in inspections around 2013 and again in 2014. Re-engineered solutions were reached, and the engine production has continued. Changes in foreign contracts are causing a projected hike in the cost of production for both the F135 engine and the F35 planes themselves.
The Pentagon’s F-35 Joint Program Office is “continuing to work with Pratt and Whitney on steps to address the projected cost growth to ensure that the F135 Propulsion System remains affordable component of the F-35 air system,” F-35 program executive Lt. Gen. Eric Fick stated in written testimony to lawmakers. 
In addition, challenges from the COVID-19 pandemic have added difficulties in sustaining the F135 due to a power module shortage.