Originally Posted by
SASless
Fact....How long had the engines been running when they quit due to fuel starvation?
Dave (or any Pilot) should have had that fact worked into the situation along with the possibly confusing indications.
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SAS I believe I understand your point being the relationship to his expended flight time and his assumed endurance. However, the helicopter was recovered with 76 kgs in the main tanks and there was zero fuel in the supply tanks. The total quantity of fuel on board being around 25 minutes flight time. His VFR FRF limit being 20 minutes in EASA Land. He was less than 2 minutes from his base. In a serviceable EC135 this condition (fuel locations) is generally associated with the fuel transfers pumps being selected OFF for some time, allowing the balance in the supply tanks to be consumed independently until fuel starvation of the engines occurred. In a fully serviceable helicopter this would be presented to the pilot as a Blue graphic showing 76 kgs remaining in the Main and the supply tanks blue graphics reducing to zero. Associated Amber and Red Fuel Low warnings occurring along the way.
We do know, with a degree of certainty, was the Fuel Low Warnings appeared and were cancelled by the [crew]. This being recorded by the NV memory in the CAD system.
What we do not know, is what the graphic presentation looked like (the indication of where exactly the fuel was). This argument appears to be supported by several events after Dave's accident whereby the graphic indications of fuel did not match the warnings being delivered by the Red Low Fuel Backstop indicators. Dave's fuel contents indication system was subsequently tested and appeared to function normally. However, in the subsequent events, it was determined that only a minute amount of water in the Capacitance Sensor was enough to give an indication that the tank was full. The Thermistor fuel backstop Red Warnings are independent of the capacitance contents sensors.
Taken holistically, we could make an argument that Dave left his transfer pumps OFF. This caused his supply tanks to deplete to zero, triggering many warnings of FUEL LOW, Amber and Red. Why did he not react???? Maybe what he saw, and more importantly trusted above all else, was the graphic indications of where the fuel was. Maybe his supply tanks were indicating FULL, caused by a minute amount of water the capacitance sensors which subsequent to recovery of the helicopter post accident, had dried away. If you read the report, the amount of water required to create this illusion is miniscule. To accept this we would also have to accept that Dave did not realise the independent and robust nature of the Thermistor Sensors (providing Red FUEL LOW Warnings) and thus allowed himself to be "driven" by the contents indications alone.
In conclusion, I do not think we can accuse Dave of not managing his endurance appropriately.
It is for these reasons, that many of us conclude that the learning points are, 1. The importance of the Red FUEL LOW warnings, regardless of what appears on the CAD Contents graphic indications. In addition, the crystal clear association between a FUEL LOW warning of any kind, and an immediate requirement to check the status of the Transfer Pumps (ON).