Bristow MAYDAY off Stavanger
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That is surprising HB, are you referring to single engine a/c? Even the S61 with 1950's technology has overspeed protection. Do Puma's not have it?
I am sure there are others here who will know more detail on that accident than I do.
There are numerous others i am aware of on different types, but most are unconfirmed due to lack of CVR/FDR.
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OK, HB......just wanted to clarify your statement that said:
The L1 you mention had it, but it did not function correctly.....
none of these had an automatic overspeed protection system
The Puma had an agricultural system that relies on on two bobweights spinning against a spring and fuel pressure. The drive for this is from the rear of the turbine to the throttle control unit. There being no anticpator with this system some horrendous rotor droops can be attained.
However it is a saviour if the flector drive or input shaft fails because as the turbine spins up the speed monitoring shaft automaticaly slows the engine at the same rate. One case in 1979 at Teeside resulted in the pilot totally unaware that he had had a input drive shaft failure; he thought it was a simple engine rundown.
Both the 330 and the 332 used to have a system whereby No 1 engine could be disconnected from the gearbox and despite the wails from the engineers about the turbine overspeeding the engine would settle at ground idle with the Rotor Tacho showing the turbine at about 175 equivalent.
However it is a saviour if the flector drive or input shaft fails because as the turbine spins up the speed monitoring shaft automaticaly slows the engine at the same rate. One case in 1979 at Teeside resulted in the pilot totally unaware that he had had a input drive shaft failure; he thought it was a simple engine rundown.
Both the 330 and the 332 used to have a system whereby No 1 engine could be disconnected from the gearbox and despite the wails from the engineers about the turbine overspeeding the engine would settle at ground idle with the Rotor Tacho showing the turbine at about 175 equivalent.
Last edited by Fareastdriver; 26th Sep 2011 at 09:06.
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Both the 330 and the 332 used to have a system whereby the engine could be disconnected from the gearbox and despite the wails from the engineers about the turbine overspeeding the engine would settle at ground idle with the Rotor Tacho showing the turbine at about 175 equivalent.
I need not have worried, the start was completely normal, but spooky sitting in a 212 with 2 engines at 100% and the blades stopped
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HB
You statement regarding the HS L1 is totally incorrect. The vibration was caused by an imbalance in the shaft due to the nut connecting the shaft to the gearbox coming off. This caused the the shaft to rub against the overspeed sensors to the point where the overspeed protecting failed when the shaft eventually failed. I had one 3 years later and the system worked as advertised.
BTW good post on the NL offshore union bit. A few idiots out there making life hell for the operator and their fellow workers. Tail wagging the dog out there at present. Not a healthy working environment. Second guessing every decision made!
You statement regarding the HS L1 is totally incorrect. The vibration was caused by an imbalance in the shaft due to the nut connecting the shaft to the gearbox coming off. This caused the the shaft to rub against the overspeed sensors to the point where the overspeed protecting failed when the shaft eventually failed. I had one 3 years later and the system worked as advertised.
BTW good post on the NL offshore union bit. A few idiots out there making life hell for the operator and their fellow workers. Tail wagging the dog out there at present. Not a healthy working environment. Second guessing every decision made!
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Horror box -
Orxys -
Sorry I must have interpreted the Accident report incorrectly, but I did not think I was that far off. Although I will admit that my Puma tech knowledge ís a dim and distant memory now!
From the AAIB report LN-OPG (issued November 2001) AAIB/N REP : 47/2001.
Cracks in the No.2 input shaft resulted in a large imbalance in the shaft, followed by catastrophic failure. The power turbines burst and cut the control rods. The aircraft had an overspeed warning and protection fitted, however it did not function correctly.
You statement regarding the HS L1 is totally incorrect. The vibration was caused by an imbalance in the shaft due to the nut connecting the shaft to the gearbox coming off. This caused the the shaft to rub against the overspeed sensors to the point where the overspeed protecting failed when the shaft eventually failed.
From the AAIB report LN-OPG (issued November 2001) AAIB/N REP : 47/2001.
the direct cause of the accident was that several fatigue cracks had occurred in a splined sleeve in the R/H shaft input of the main gearbox. This led to a lock washer getting into the power transmission shaft (Bendix shaft) of the R/H engine. This caused a large imbalance of the Bendix shaft and its subsequent failure. This gave rise to vibrations that caused malfunction of the engine's system for regulating and controlling the engine speed. As a result of this and the loss of loading due to the fracture in the Bendix shaft, the power turbine RPM rose out of control. When the number of revolutions reached approx 175%, the power turbine burst and fragments from this cut two flight control rods to the main rotor and the flight control rod for the tail rotor. It also destroyed the power turbine section on the L/H engine.
