Technical Questions
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Joined: May 2013
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From: Philippines
Technical Questions
im student,currently having a training on commercial engines,i need someone who can educate me about the functions of the following engine system components: HMU,PRSOV,PRV,HPSOV and IDG, thanks..
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From: Brighton, UK
have a look at this website. I found it very usefull on loads of things when I did my license The Boeing 737 Technical Site
Last edited by ec155mech; 24th May 2013 at 07:23.
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From: Siliconia
Large gas turbine domain
A Hydro-Mechanical Unit (HMU) [alternatively a Fuel Metering Unit (FMU)] is the assembly used to house most (if not all) electrical control to fuel valve interfaces. By this (my) definition, the Hydro-Mechanical Unit must therefore contain: -
a metering valve, with electrical drive and position feedback
a spill valve (return excess HP to the LP fuel system), usually with no electrical interfaces
a high pressure shut-off valve (HPSOV), with electrical drives and position feedback.
The high pressure shut-off valve (HPSOV) is usually designed for both FADEC (e.g. Autostart) and aircraft functions, i.e. related engine run/cut-off switch and fire switch operation. These particular aircraft function examples must be reasonably isolated from the FADEC fuel metering role, so that simple failures can not propagate into an inability to shut-down when the metering system is faulty.
The fuel delivery system has to work over a very wide range of fuel flows and (engine burner required) delivery pressures, whilst some of the valves require high end pressures to satisfy servo force margin designs. It is therefore normal for the Hydro-Mechanical Unit assembly to include a pressure raising function, this can be arranged as one of the following: -
a Pressure Raising Valve (PRV) that acts independently and without electrical interfaces, or
a Pressure Raising Shut-Off Valve (PRSOV), i.e. merged function with the above SOV, or
a Pressure Raising Spill Valve, i.e. merged function with the above spill valve.
In my experience an IDG is an Integrated Drive Generator, this unit provides electrical power exclusively for the aircraft, i.e. it does not directly power the HMU or FADEC. The Boeing 787 combines this generator role with the engine starter motor role, in a starter/generator – this is discussed elsewhere in PPRuNe due to some
battery interactions!
A Hydro-Mechanical Unit (HMU) [alternatively a Fuel Metering Unit (FMU)] is the assembly used to house most (if not all) electrical control to fuel valve interfaces. By this (my) definition, the Hydro-Mechanical Unit must therefore contain: -
a metering valve, with electrical drive and position feedback
a spill valve (return excess HP to the LP fuel system), usually with no electrical interfaces
a high pressure shut-off valve (HPSOV), with electrical drives and position feedback.
The high pressure shut-off valve (HPSOV) is usually designed for both FADEC (e.g. Autostart) and aircraft functions, i.e. related engine run/cut-off switch and fire switch operation. These particular aircraft function examples must be reasonably isolated from the FADEC fuel metering role, so that simple failures can not propagate into an inability to shut-down when the metering system is faulty.
The fuel delivery system has to work over a very wide range of fuel flows and (engine burner required) delivery pressures, whilst some of the valves require high end pressures to satisfy servo force margin designs. It is therefore normal for the Hydro-Mechanical Unit assembly to include a pressure raising function, this can be arranged as one of the following: -
a Pressure Raising Valve (PRV) that acts independently and without electrical interfaces, or
a Pressure Raising Shut-Off Valve (PRSOV), i.e. merged function with the above SOV, or
a Pressure Raising Spill Valve, i.e. merged function with the above spill valve.
In my experience an IDG is an Integrated Drive Generator, this unit provides electrical power exclusively for the aircraft, i.e. it does not directly power the HMU or FADEC. The Boeing 787 combines this generator role with the engine starter motor role, in a starter/generator – this is discussed elsewhere in PPRuNe due to some
battery interactions!
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From: Seattle
an IDG is an Integrated Drive Generator,
The Boeing 787 combines this generator role
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From: Seattle
Rolls Royce Trent 1000 "HMU" uses a PRSOV (Pressure Raising Shutoff Valve) not "Regulating" : It does not regulate pressure. It is a simple valve that is operated by the PRSOV servo valve.
So in essence PRSOV "Raising" is misleading, it neither raises nor regulates.
So in essence PRSOV "Raising" is misleading, it neither raises nor regulates.
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From: Dharan
Someone on the MH370 forum asked about fluid venting from a pipe inboard of the no.2 engine. Somebody suggested fuel, but that does not seem sensible.
Are there any P-3 techies familiar with the fuel system that can enlighten us. Can you post the answer on the MH370 forum too.
Thanks.
Are there any P-3 techies familiar with the fuel system that can enlighten us. Can you post the answer on the MH370 forum too.
Thanks.
Last edited by buttrick; 29th March 2014 at 10:29.
Joined: Jun 2006
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From: Dharan
Someone on the MH370 forum asked about fluid venting from a pipe inbord of the no.2 engine. Somebody suggested fuel, but that does not seem sensible.
Are there any P-3 techies familiar with the fuel system that can enlighten us. Can you post the answer on the MH370 forum too.
Thanks.
Are there any P-3 techies familiar with the fuel system that can enlighten us. Can you post the answer on the MH370 forum too.
Thanks.
Joined: Jun 2010
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From: Brisbane, Australia
In response to the Q regarding the P3 having a 'pipe' laying on top of the wing inboard of the #2 engine, I know of no such pipe.
The only component that 'dirties' the upper wing surface of the wing, as far as I recall, is the fuel jettison pipe. This pipe outlet is only about 2 foot (60 cm) long, and located right back almost at the wing trailing edge, on the left wing, right inboard near the aft wing fillet. It does not run anywhere near the engine nacelle! It's located there because fuel can only be jettisoned from the centre tanks.
It's so close to the fuselage that it can only be seen from the port overwing hatch window, or the port aft observers window.
The only component that 'dirties' the upper wing surface of the wing, as far as I recall, is the fuel jettison pipe. This pipe outlet is only about 2 foot (60 cm) long, and located right back almost at the wing trailing edge, on the left wing, right inboard near the aft wing fillet. It does not run anywhere near the engine nacelle! It's located there because fuel can only be jettisoned from the centre tanks.
It's so close to the fuselage that it can only be seen from the port overwing hatch window, or the port aft observers window.
