Cost index.
if it’s done correctly it’s optimum cost. But doing it correctly is often difficult in the real world.
The Universal FMS does not permit a Cost Index entry as many FMC's do. As far as FMS's go, the UNS-1Ew is not much more capable than a Garmin 430. In fact, the Garmin 430 is sometimes the better product!
That's all really interesting, many thanks +TSRA.
I take advantage of the fact you know the Dash 8 pretty well. Can you give ballpark numbers of Fuel Burn at ICR and LCR?
The following figures are for ISA conditions at 58,000 lbs with the ice protection system off.
Long Range Cruise (LRC): 2,462 lbs/hr (245 KTAS) at Sea Level to 1,704 lbs/hr at FL250 (297 KTAS)
Intermediate Range Cruise (IRC): 2,462 lbs/hr (245 KTAS) at Sea Level to 1,907 lbs/hr at FL250 (321 KTAS)
High Speed Cruise (HSC): 2,462 lbs/hr (245 KTAS) at Sea Level to 2,212 lbs/hr at FL250 (344 KTAS)
Maximum Cruise Rating (MCR): 2,462 lbs/hr (245 KTAS) at Sea Level to 2,501 lbs/hr at FL250 (361 KTAS)
Notice that for LRC, IRC, HSC, and MCR that the Sea Level Fuel Flow and Speed remain constant. That is because we are limited a) by the Speed Order Limit for 250 knots below 10,000' and b) the aircraft VMO, which is set at 248 KIAS until 8,000' increasing linearly to 282 KIAS by 10,000'. But because we legally can't fly faster than 250 KIAS, they don't provide data for what you could actually get out of the engines below 10,000'.
The fuel will vary typically no more than about +/- 20 to 40 lbs/hr from the values I've shown you for every 2,000 lbs in aircraft weight and about +/- another 30 to lbs/hr for every 10*C change in ISA. Those are rough estimates and from a basic calculation from the charts while sitting at the kitchen counter here.
For the ice protection system on, the book says "For Vmo limited data increase Torque by 0.3% and Fuel Flow by 15 lb/hr; otherwise reduce speed by 1 KIAS and 2 KTAS." So, you only have a fuel flow penalty for the ice protection system when limited by Vmo.
In terms of maintenance, is it an expensive aircraft to operate with unexpected failures or is it a very reliable aircraft?
That I don't know and I'd honestly be taking a stab in the dark as I'm more involved in training at my airline than operations and cost control. I find that it is a fairly reliable aircraft with some definite quirks, but I also know there are some engineers that feel it is the bain of their existence. So, I'll let someone else more knowledgeable about the maintenance side of things pipe in on this question.
Also, by desactivating the NVS, does the difference of the sound level in the cabin is huge or it's just a slight difference?
The book claims the NVS reduces the cabin noise to 75dB from about 85dB, so definitely noticeable if it fails or malfunctions in flight, but I doubt most people would notice the difference if the system was off at the beginning of the flight.