Dash8 MCR VS LRC / Fuel economy

[A380MSN0001]

Hi everyone, I'm currently working on a University project regarding Regional Airlines.

Would this make sense for a regional airline operator in order to be competitive and save some cash to operate as follow :

- Days Operations :
Speed : MCR in order to compete with the regional jets
Network : from 250 to 400NM sectors / Competing with the regional jets

- Night Operations
Speed : LRC as less competition
Network : From 600 to 800NM sectors / Leisure destinations type clientele who don't mind to fly at nights and just looking for cheap fares //

Does the saving between the MCR and the LRC is significant at the end?
Does some regional airlines operates their Dash8 Fleet like this?

Many thanks for your feedbacks.

[+TSRA]

Without giving too much away, my company saves over $1 million by slowing to ICR (Intermediate Range Cruise) from MCR, so going down to LRC maybe call it another $300,000 to $500,000. We are planned by the dispatchers for all flights at MCR and then once at cruise we determine based on the schedule, anticipated arrival and approach, and other factors whether to slow to ICR (Intermediate Range Cruise) or LRC. We decide in 15-minute blocks. If we are late or up to 15 minutes early, tend to stay at MCR and accelerate to VMO-10 or whatever is shown on the flight plan for TAS at Cruise. From 15 to 20 minutes we tend to slow to ICR, and from 20 minutes on we slow to LRC. Of course, all of this depends on the sector length. We have a couple two and three-hour sectors where we might not slow down until we have a better idea of what the winds ahead of us are doing - 20 minutes early at TOC can easily become 20 minutes late if you don't think ahead.

A competing airline to mine always plans at IRC because most airports for our area of operations do not treat the Q400 like a jet, so they've found they're the ones always getting speed reductions or vectors anyways. Indeed, the "jet" performance of the Q400 is only because we can keep up below 10,000' because of the speed limit order. Above 10,000' and we're just another turboprop. I think the book says we cruise at around 0.5 Mach, but there is nothing in the flight deck as standard equipment to tell you the speed in Mach, and we're blown out of the water by most jets above 10,000'.

There are two other main ways of saving money in Q400 operations: single engine taxi and the FL270 supplement. We use single engine taxi whenever we can. Bombardier says you'll save an extra 3% in fuel by going up to FL270, but you need to install the drop-down oxygen masks for that supplement and just the maintenance costs outweigh the fuel savings for most Q4 operators.

So does it make sense to plan the way you've suggested? Sure. But you give your pilots zero wiggle room to make up time at night if you plan at LRC and only load that amount of fuel. Furthermore, night ops are where all the compounding delays from the day build up to bite you, so you don't want to be slow as you're likely trying to prevent your OTP from going out the window. Better to always plan for the higher speed, then let your pilots decide to keep going fast to maintain the schedule or to slow down to save fuel (and maintain the schedule).

Consider it the difference between theoretical operations and practical operations.

[FE Hoppy]

Cost index.

if it’s done correctly it’s optimum cost. But doing it correctly is often difficult in the real world.

[A380MSN0001]

Without giving too much away, my company saves over $1 million by slowing to ICR (Intermediate Range Cruise) from MCR, so going down to LRC maybe call it another $300,000 to $500,000. We are planned by the dispatchers for all flights at MCR and then once at cruise we determine based on the schedule, anticipated arrival and approach, and other factors whether to slow to ICR (Intermediate Range Cruise) or LRC. We decide in 15-minute blocks. If we are late or up to 15 minutes early, tend to stay at MCR and accelerate to VMO-10 or whatever is shown on the flight plan for TAS at Cruise. From 15 to 20 minutes we tend to slow to ICR, and from 20 minutes on we slow to LRC. Of course, all of this depends on the sector length. We have a couple two and three-hour sectors where we might not slow down until we have a better idea of what the winds ahead of us are doing - 20 minutes early at TOC can easily become 20 minutes late if you don't think ahead.

A competing airline to mine always plans at IRC because most airports for our area of operations do not treat the Q400 like a jet, so they've found they're the ones always getting speed reductions or vectors anyways. Indeed, the "jet" performance of the Q400 is only because we can keep up below 10,000' because of the speed limit order. Above 10,000' and we're just another turboprop. I think the book says we cruise at around 0.5 Mach, but there is nothing in the flight deck as standard equipment to tell you the speed in Mach, and we're blown out of the water by most jets above 10,000'.

There are two other main ways of saving money in Q400 operations: single engine taxi and the FL270 supplement. We use single engine taxi whenever we can. Bombardier says you'll save an extra 3% in fuel by going up to FL270, but you need to install the drop-down oxygen masks for that supplement and just the maintenance costs outweigh the fuel savings for most Q4 operators.

So does it make sense to plan the way you've suggested? Sure. But you give your pilots zero wiggle room to make up time at night if you plan at LRC and only load that amount of fuel. Furthermore, night ops are where all the compounding delays from the day build up to bite you, so you don't want to be slow as you're likely trying to prevent your OTP from going out the window. Better to always plan for the higher speed, then let your pilots decide to keep going fast to maintain the schedule or to slow down to save fuel (and maintain the schedule).

Consider it the difference between theoretical operations and practical operations.

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?

In terms of maintenance, is it an expensive aircraft to operate with unexpected failures or is it a very reliable aircraft?

Also, by desactivating the NVS, does the difference of the sound level in the cabin is huge or it's just a slight difference?

Thanks for your feedback ;)

[+TSRA]

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.

[+TSRA]

I did forget to mention too that running the bleeds in the MIN position (rather than NORM or MAX) will also save a little bit of fuel. By going from MIN to NORM to MAX, we command more bleed air from the pneumatic system. Commanding more bleed air causes a reduction in airflow which results in decreased engine performance. The reverse is true where commanding less bleed air causes an increase in engine performance up to turning the bleeds off. However, there will always be a slight draw because the Q400 uses bleed air for airframe de-icing, so you can never turn ALL the bleed air off, only that part going into the air conditioning system unless you turn both engines off.

However, modulating the amount of bleed air used has the most direct impact on passenger comfort for all the fuel savings methods. Most pilots I fly with either ignore the potential fuel savings or come up with some sort of easy-to-remember system like 20 people or less use MIN, 21 to 60 use NORM, and over 61 use MAX - something like that.

[Machdiamond]

Bombardier used to have a Q400 Fuel Efficiency Manual pdf available for download on their web site for awhile, there are still copies of that pdf floating around if you google these title words (PM me if you cannot find it).

The document provides several answers to the OP questions, and touches the topic of cost index.

[+TSRA]

Here is the link for the above-noted document: Q400 Fuel Efficiency Manual (https://studylib.net/doc/18500975/q400-fuel-efficiency-manual---commercial-aircraft)

The unfortunate sentence in that document is found on page 33: "If a cost index solution is developed..." That is, Bombardier has everything ready to go if someone else is willing to develop the software and uplink data. Many companies have developed their own EFB related software, but it is not a Cost Index in the true sense of the word where a value of 30 or 50 actually means something. Often it is nothing more than "set for the fuel flow to this and hope for the best."

[A380MSN0001]

That's awesome guys, thank you very much. This is very helpful.

Bombardier is promoting the "Q400 NEXTGEN" is fuel burn reduced compared to the "non NEXTGEN". Did you guys noticed this aswell? If yes, do you have some numbers in order to compare?

Again, thanks ;)

[+TSRA]

Yeah, there is a slight difference between the Q400 and Q400NextGen, but I don't have a copy of the Q400 Aircraft Operating Manual to provide you firm data with - just the NextGen; maybe someone else?

[Machdiamond]

I checked the numbers you posted above with an older non-NextGen Q400 AOM and they are all exactly the same.

[A380MSN0001]

Thanks guys, very helpful for my study.

The Dash 8 seems to be a versatile aircraft able to do various missions and being cost competitive against the regional jets on mission until 350-380NM.
It's a bit surprising that apart Flybe, so few European Regional Operators have them in numbers on their fleet.