Topic Author
Posts: 25
Joined: Sun Jan 13, 2002 8:52 pm


Wed Jun 05, 2002 9:19 pm

I have a question,

On an HMU of any high bypass engine, the medium used to transmit any form of adjusting of the vanes and valves is done by pressurised fuel from the HMU.
But when fuel is pressurised at such an extend, it there a safety built in to protect the pressurised fuel lines from air/oxygen entering the fuel pressurised system. Because if air did get in, you would have not only an engine fire, but a wing fire I think.

What do you think??

Ivo 21
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am


Wed Jun 05, 2002 11:19 pm

It's a closed system...and in any event, "air" is just that: Air, a 21/78 O2/N2 mix...not 100% oxygen. The largest concern however would be a leak, in either the fuel lines, or the dynamic/static seals in a component; This is why line couplings for high pressure fuel running in the core (hot ) area are shrouded and provided with their own overboard drain system. This is also the case for the VBV and VSV actuators: They're constructed in such a way that a blown seal would be directed to a drain line or lines, and run out of the drain mast instead of spraying all over the hot core. Fuel pumps, and HMU's ( or MEC's, or FFG's, as the case applies ) etc are provided with drains as well if the shaft or other seals fail or "weep" fuel.

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