The SR-71 was powered by JP-7 fuel. The JP-7 had a very high flash point, which means it was extremely difficult to ignite. This "feature" was essential for the SR-71 because the aircraft operated at high speeds and altitudes where conventional fuels would have ignited due to the high temperatures involved in high speed flying. The high flash point of JP-7 allowed the SR-71 to withstand these conditions. Above Mach 2.6...another aspect came into consideration, which is the vaporization of the fuel inside the fuel tanks. To eliminate the ignition of vaporized fuel in the tanks, the tanks were pressurized with Nitrogen rather than compressed air.
*The nitrogen tanks pressurization is being simulated in the VSKYLABS SR-71-TB as well!.
Due to the unique characteristics of the JP-7, a dedicated ignition system was required for normal engine and afterburner ignition; the 'TEB' system:
TEB (Triethylborane) system in the SR-71 was used to ignite the engines. The TEB system injected a small amount of Triethylborane, a pyrophoric chemical, into the engine's afterburner. TEB spontaneously ignited upon contact with the air, creating a high-temperature flame that initiated the engine's combustion process. This system was crucial for starting the engines at high speeds and altitudes where traditional ignition methods wouldn't work effectively.
On the practical aspect, at least 16 metered TEB injections could have been made with one full tank of TEB. Every time that the throttles passed through the afterburner threshold, the TEB counter stepped down accordingly, showing the remaining TEB shots available.
The pilot had to carefully manage the use of afterburner and engine start-ups during flight as it could potentially lead to a limitation on its mission duration or range, as it might not be able to restart the engines in case they flamed out.
The limited availability of TEB *shots* was a practical consideration in SR-71 operations, and careful planning and management were necessary to ensure the aircraft's safe and efficient performance during its high-speed, high-altitude reconnaissance missions.
The TEB system is being simulated in the VSKYLABS SR-71-TB.
In the attached images:
- The TEB 'counters' can be seen, located in the throttles base.
- Throttles Aural Warning: The VSKYLABS SR-71-TB is equipped with throttles-aural-warning system, to allow you aural-warning each time you are getting close to the TEB-Injection thresholds: From cut-off to Idle (and vice versa), and from full dry power to Afterburner ignition (and vice versa). This is a 'smart-solution' that overcomes the lack of physical detents in common Throttle hardware.
