Tsufang@ci From Taiwan, joined Feb 2002, 39 posts, RR: 0 Posted (12 years 4 months 3 weeks 1 day 23 hours ago) and read 3325 times:
there are 30 fuel nozzles around the cf680c2 engs combustion chamber
but the # 15 an # 16 nozzle different from other 28 fuel nozzle
as the manual said "no 15 and 16 will provide richer fuel during decent and part number also different "
the two nozzles install on bottom of the chamber about 6 o'clock position
why they different with others and why provide more fuel during decent?
Cdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 26
Reply 1, posted (12 years 4 months 3 weeks 1 day 6 hours ago) and read 3110 times:
The fuel nozzels at the number 15 and 16 positions are designed differently than the other 28 nozzles. They are also color coded differently than 26 other ones (The 2 which are attahced to the ignitors also have different p/n). Nozzles 15 & 16 have larger primary spray patterns. They are always going to provide more fuel. Fuel nozzles are designed to provide the most efficient spray patterns at high power settings. During descent when the throttles are at times idled and at much lower power settings, these nozzles with the extra fuel output provide flameout protection.
Most aircraft ignition/fuel systems do a little extra during the approach phases of flight to prevent flameouts at such a critical time (also during adverse weather). An example if high idle. When flaps are down, or mayeb gear down under certain altitudes on some aircraft - the engines will go into high idle. In some aircraft, ignition will be initiated with anti-ice on. All to prevent flameouts.