Depends a bit on the game version you used for testing.
On 4.12 it runs for 16 mins - simple test: Chocks in, start engine, full power, wait for the engine to shut off.
On 4.14 TD introduced a new "FuelRocketCoeff" value, which results in an operation time of 9~10ish minutes. Right direction, yet still wrong
I used to set a 9-minute timer to know when to run home, hoping there would be enough fuel for the evasive manoeuvres near the home base if there were enemy fighters.
That's the next question where I'm wondering whether it's worth implementing real life, or if we'd just make life too hard for our fellow armchair pilots:
The HWK 109-509A needed two minutes cooldown before starting if the pilot shutdown the engine in flight.
Two minutes like "with a little luck, one and a half might do, and if you grab the short straw, it either won't ignite or simply blow up".
Would it make sense to implement this?
Furthermore, the fuel system relied on gravity.
Prolonged negative G-Forces would first cause the engine to cut off, and finally pour fuel into the fuselage/wings/cockpit section where - if both T- and C-Stoff remain - it would ignite and blow up the plane, or - if only T-Stoff remains (usual case in landing condition) - will combust the pilot, literally (thankfully the germans put two small T-Stoff tanks to either side on the cockpit, how comfortable!).
Would it make sense to implement this?
Finally, the stock implementation of the Me 163 rocket engine got the idea of "nozzle groups" wrong.
There are three groups, with groups 1 and 2 featuring 3 T-Stoff injectors each, and group 3 featuring 6 of them. All injectors worked on one central C-Stoff supply vane.
1C/Maddox apparently thought that the nozzle groups were used in an "on/off" fashion to imitate thrust regulation, but the truth is that each of the groups could almost seamlessly be regulated between idle and full supply.
Therefore, the Me 163 thrust doesn't operate in "steps", but smoothly between 100kp (idle thrust, 13° throttle lever position) and 1600kp.
I will implement this accordingly.
Mike