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DPE

RB211 START BLEED VALVES

Phil Milne

Technical Support Manager

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Start BOV HistoryAs a result of the starting difficulties experienced by the Ind RB211-24-GT engine standard with the phase II combustor. The Ind RB211-24-GT has a Trent 800 HPC, which has a lower sub-idle stall line than the HPC used in the Ind RB211-24-G. This could cause the HPC to stall when the 3 off HP3 starting bleed valves (SBOVs) closed during the accel to idle resulting a failed start.

The solution to this problem was to change the material of the springs that are located internal to the SBOVs so that a higher HP3 operating pressure was required to close the valves. This had the result that the SBOVs closed later during the starting sequence when the HPC has enough stall margin for the HP3 SBOVs to close without the HPC stalling.

The existing bleed valves (LW17699) used on the Ind RB211-24-GT phase II engines may be reworked through RRC facilities to the new standard of valve with Rolls-Royce part number LW100165.

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RB 211 Bleed Valves.

AC66768L913567AC65152LW10425LW100169LW17699RB211 24 GT

AC66768L913567AC65152LW10425LW17699RB211 24 G

Dunlop PNIP BleedDunlop PNHandling BleedReworked Start Bleed Start BleedBleed Type

2 off1 off3 off3 off

Bleed Valve Part NumbersEngine Type

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Stage 1.With the engine starting the HP3 control air pressure will increase closing the Start Bleed valves gradually. Depending on the ambient these will close between 130 to 183 NDS, with higher ambient conditions this will be near the 183 NDS.Stage 2.HP and IP bleeds have HP3 control air applied to them until 345 NDS when the ECS will initiate the close command removing HP3 air allowing them to close. These valves will open on a decel at 337 NDS.

Figure 1 below shows HP3 Air at stage 1, Figure 2 below shows HP3 Air at stage 2.

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HP Handling Bleed ValveStarting Bleed Valves

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Current Problem

SBOV intermittently not working correctly at various stages.Water drained from HP3 lines.Excessive condensation in HP3 line during the highest humidity days is believed to be the cause. Three sites with same problem in same conditions.SBOV internal seals breaking up from water locking.

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SBOV Damage

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Trial resolution

Connect drain to lowest section of SBOV HP3 line.Install needle valve to set required flow

To Atmosphere in the package floor

Lockable Needle valve

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RB211 HP3 PipingHP3 Line Filter HP3 line to SBOV HP3 line to SBOV at lowest point