Ivo21 From Netherlands, joined Jan 2002, 25 posts, RR: 0 Posted (12 years 9 months 5 days 18 hours ago) and read 2733 times:
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.
NKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 1, posted (12 years 9 months 5 days 16 hours ago) and read 2709 times:
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.