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 What Is The "N" In N1 Or N2?
 Norseman From United States of America, joined Feb 2001, 41 posts, RR: 0Posted Wed Feb 6 2002 02:54:17 UTC (14 years 3 months 3 weeks 17 hours ago) and read 12121 times:

 I was discussing turbine engine operations with a captain today, when we both pondered what the "N" in N1 or N2 stands for. I am having a hard time finding any information on this. I know that N1 indicates low pressure compressor speed, and N2 indicates high-pressure compressor speed, but what does "N" stand for? Any insight?
 Airplay From , joined Dec 1969, posts, RR: Reply 1, posted Wed Feb 6 2002 03:29:22 UTC (14 years 3 months 3 weeks 17 hours ago) and read 12022 times:

 The International System of Units was developed in an effort to standardize measurement in scientific circles. The "SI" system really represents a modern form of the metric system. The generally accepted SI symbol for rotational frequency is "n". Rotational frequency is normally expressed in "radians per second". "n" rotational speeds in turbine engines are predetermined maximum rotational speeds of specific shafts. Indicated rotational frequency is typcially expressed in percent of "n". Why "n" instead of some other symbol? You could ask the same question about pi....
 Delta-flyer From United States of America, joined Jul 2001, 2682 posts, RR: 6 Reply 2, posted Wed Feb 6 2002 03:42:17 UTC (14 years 3 months 3 weeks 17 hours ago) and read 11969 times:

 N has always been used for rpm (i.e. Number of revs...) as opposed to the Greek letter omega for for angular velocity in radians per second. Pete
 "In God we trust, everyone else bring data"
 IMissPiedmont From United States of America, joined May 2001, 6544 posts, RR: 29 Reply 3, posted Wed Feb 6 2002 04:24:04 UTC (14 years 3 months 3 weeks 16 hours ago) and read 11950 times:

 In other words, the N itself doesn't mean anything. It's just a letter. One of the aviation oddities as most every other letter means something starting with that letter.
 The day you stop learning is the day you should die.
 Norseman From United States of America, joined Feb 2001, 41 posts, RR: 0 Reply 4, posted Wed Feb 6 2002 04:48:44 UTC (14 years 3 months 3 weeks 15 hours ago) and read 11928 times:

 Thanks a lot guys. The captain I was talking with said he has never gotten a good answer about "N". I even asked some guys in maintenance and their answer was "Uh, well you see...Um, It's probably..." I knew you guys would come through! Norseman
 AJ From Australia, joined Nov 1999, 2406 posts, RR: 24 Reply 5, posted Wed Feb 6 2002 04:51:00 UTC (14 years 3 months 3 weeks 15 hours ago) and read 11927 times:

 Similar to air pressure being denoted by 'Q', as in Qnh, Qfe etc etc. Odd.
 Bobsmuggle From Australia, joined Jul 2001, 49 posts, RR: 0 Reply 6, posted Wed Feb 6 2002 13:55:43 UTC (14 years 3 months 3 weeks 6 hours ago) and read 11882 times:

 QNH, QFE etc are from the old morse and alike days. QNH is short for "Question - Nil Height" which would be interpreted as "I have a question, what is the nil height"
 AJ From Australia, joined Nov 1999, 2406 posts, RR: 24 Reply 7, posted Wed Feb 6 2002 22:03:42 UTC (14 years 3 months 2 weeks 6 days 22 hours ago) and read 11833 times:

 Well done Bob, I thought that info had been lost into history. Likewise at my company runway heading is still called QDM.
 Airplay From , joined Dec 1969, posts, RR: Reply 8, posted Thu Feb 7 2002 03:13:23 UTC (14 years 3 months 2 weeks 6 days 17 hours ago) and read 11804 times:

 Yes....Omega is the primary SI symbol for angular velocity. "n" is an alternate. I did a bit more research (asked some of my engine buddies) and found that the "n" I was referring to is not the same as the "N" used in N1 and N2 engine indications. N is the symbol for "specific speed". Specific speed is defined as "the speed of an ideal pump geometrically similar to the actual pump, which when running at this speed will raise a unit of volume, in a unit of time through a unit of head". Here are some links that explain what specific speed is: http://www.negia.net/~nelik/ns.htm http://www.tasonline.co.za/toolbox/pump/powns.htm http://www.mcnallyinstitute.com/07-html/7-03.html Again....I have no idea why they chose "N".
 Bobsmuggle From Australia, joined Jul 2001, 49 posts, RR: 0 Reply 9, posted Thu Feb 7 2002 13:50:35 UTC (14 years 3 months 2 weeks 6 days 6 hours ago) and read 11753 times:

 I have never heard QDM before... would that mean Question - Direction Magnetic???
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