|Quoting N808NW (Thread starter):|
-what take off settings are used on a 100/70/50/20% (differnt settings for each load?) full (fuel and pax) 744 or 772? and for other aircraft?
-what setting are used at cruse, and once again how dose N1 N2 compare to the throttle location?
DISCLAIMER: Forgive me, professional pilots and AMEs, if I get some of this wrong. I've had very little training in turbine engine theory.
Answer #1: as many posters have said above, it varies on the weight of the aircraft, length of runway, temperature outside and other factors. Usually, the pilots use a thrust settings table in either the POH or QRH (I'm not sure which one, though) to determine the takeoff thrust for that leg's flight. Most of the times, to save engine wear and fuel, a de-rated (Boeing) or FLEX (Airbus) thrust setting is used if there is a long enough runway or the payload is lighter and does not facilitate a full-throttle takeoff.
During pre-flight, the pilots will cross-check the N1 thrust settings in the manual with the PERF INIT page on the FMC, and can select various thrust settings on the FMC.
Example: I'm using the PMDG 737NG manual for a reference; I don't have an actual 737NG manual with me, so this is the closest bet.
Departure airport: CYYC (Calgary International Airport) runway 34
Altitude (MSL/Mean Sea Level): 3,557 feet.
Using the PMDG table, with the selected temperature and altitude parameters, a thrust setting of approximately 96.1% N1 (fan spool) would be used. That's at 24KN full-thrust takeoff power if the aircraft is fully loaded. De-rated thrust could be anywhere between 5-10% lower than max thrust (86.5-91.3%), the former being if the aircraft is extremely light and there is a long enough runway.
Answer #2: Cruise settings are generally varied for weight, speed, altitude and different types of flight. From what I have heard, or I've noticed during a sim ride or two, the cruise N1 at altitude generally appears to be anywhere between 86-90% N1 to maintain cruise speed. Thankfully, with the introduction of FADEC and other marvelous technological advances, the autothrottle sets the thrust levers to a certain position that correlates with the N1 demands of cruise flight.
Once again, if someone who is type-rated in the 737 or knows more than I do about this wishes to correct some of my mistakes, please do so.
I need a drink.