LONG-RANGE CRUISE AND COST INDEX The relationship between LRC
speed and ECON speed is different for each Boeing airplane
model. As stated, LRC is based on a 1 percent penalty on fuel
mileage, while the ECON speed uses CI as an input that is based
on a more detailed accounting of actual costs. However, it is
possible to derive a CI for normal cruise conditions that
approximates LRC in terms of the cruise speed that results.
Figure 2 shows the approximate relationship for Boeing
commercial airplanes. Entered Cost Index (CI) |AIRPLANE
MODEL||MRC||TYPICAL AIRLINE CI VALUES||APPROXIMATE LRC
EQUIVALENT| |717||0||5 to 25||25| |737-3/4/500||0||10 to 30||30|
|737-6/7/800||0||10 to 30||35| |757||0||15 to 50||85|
|767||0||15 to 55||70| |777||0||90 to 150||180| |MD-11||0||80 to
120||200| |747-400||0||25 to 80||230| It is very important to
note that the LRC speed is almost universally higher than the
speed that will result from using the CI selected by most
carriers. If faced with a low fuel situation at destination,
many