No doubt that one of the most critical moments during the operation of any aircraft is the engine start. If it experiences unusual difficulty accelerating during start, a “hot start” may occur, which means that there won’t be enough airflow to cool the initial combustion of fuel within the engine.
Following the starting procedures correctly, and controlling the ITT (Inter-Turbine Temperature) is crucial to avoid those hot starts, which can damage and destroy the engine very easily.
Knowing that the engine is the most expensive part of any aircraft, and although it seems to be clear that the use of a proper external engine starter is imperative, you would be surprised to know that a huge number of operators still use non efficient and low-quality jump starter units, which are not reliable and powerful enough to ensure the delivery of the peak energy needed in any occasion.
Please, always remember that the acceptable temperature (ITT) and time limits are published within individual Aircraft Flight Manuals to prevent engine damage.
The following chart can be used as a good reference to illustrate this situation. We can distinguish four areas: A, B, C and D.
Engine manufacturer’s diagram of over-temperature conditions
Reference: US Patent 4575803
Area A shows a safe zone, where the engine starts on a short time, which results in low ITT values, being controlled and always remaining below the limits set by the engine manufacturer. The pilot is therefore performing a “cold start”, safeguarding the engine and its lifespan.
If you have selected a high-quality external engine starter, you’ll always keep these parameters in this safe zone, you will be able to enjoy your flight, and no actions will be required.
However, if you are attempting to perform and engine start using only the aircraft batteries, or a non-reliable or low-quality jump starter unit, the engine will need more time to start, resulting in the ITT getting higher, and you may follow within Area B or Area C.
Area B shows a warning zone, where the pilot has exceeded the temperature (ITT) and time limits of the aircraft. If this happens, a visual inspection will be needed through the exhaust ports of the power turbine blades and through the exhaust duct turning vanes where appropriate. Therefore, the aerial mission can be aborted, and the pilot must record this event in the engine log-book. This event causes a lack of confidence for the pilots and the technical staff, who usually won’t be sure to try another engine start again. The flight can be cancelled and maintenance actions may be required, meaning potential economic losses for the operator.
Area C shows a danger zone. The temperature (ITT) and time limits of the aircraft have been completely exceeded, and the aerial mission must be aborted immediately. A hot section inspection is mandatory. The compressor blades should be stretch checked, and a fluorescent penetrant inspection should be made of the compressor turbine and power turbine disks and blades, without removing those. The flight must be cancelled and expensive maintenance actions will be required, meaning significant economic losses for the operator.
Finally, Area D shows a critical zone. The aerial mission must be aborted immediately. If this event happens (for example, if the Max. Temperature is exceeded for 2 seconds), the complete engine must be returned to an overhaul facility. The compressor turbine blades and power turbine blades must be discarded and both of the turbine disks must be subjected to a stretch check and fluorescent penetrant inspections. The flight must be cancelled and very expensive maintenance actions will be required, meaning highly relevant economic losses for the operator.
How does ENERCRAFT’s innovative technology prevent hot starts?
ENERCRAFT is the only manufacturer of Ground Support Equipment that has developed a hybrid battery to equip all of its Ultra-Starter units!
A hybrid battery combines two different energy storage components, Lithium Batteries and Ultracapacitors, which are complementary technologies: the Lithium Batteries provide energy for the long term, while the Ultracapacitors provide the fast reaction and high power, needed during the first few seconds of any engine start cycle. Together, Ultracapacitors and Lithium Batteries are the future of electrification, making our Ultra-Starters unique in the market, due to its ability to deliver enough energy to perform the start-up of large engines and turbines of a wide variety of helicopters and airplanes.
ENERCRAFT has also developed the whole intelligent energy management system, which consist on the electronics needed to control the energy coming from both energy storage components integrated inside all of their Ultra-Starters, in order to be used in the right moment during an engine start.
With this innovative configuration, the effect of the Ultracapacitors is manifold. On the one hand, they become solely responsible for absorbing the high peaks or pulses of current demanded for several seconds at the beginning of the engine start, so that they free the Lithium cells from the delivery of that energy, thus respecting their discharge curves, and ensuring their useful life. In addition to protecting the battery pack, the Ultracapacitors reduce the voltage drop of the Ultra-Starter equipment itself, ensuring its integrity, optimizing engine starting, and protecting the aircraft’s own electronic systems and components.
And finally, the Ultracapacitors, which have an excellent behavior and efficiency in extreme temperatures, where most batteries are limited, will ensure that the current peaks necessary for starting an engine are delivered at all times, and regardless of the environmental conditions in which the aircraft operates, ensuring that, at all times, the operator will be able to complete their air missions, by always guaranteeing the “cold start” of the engines.
Invest in the right technology! Our Ultra-Starters will always keep your engine within the safe zone!
