higney85

(Also posted on another forum)
I know there are quite a few -200 pilots on here. I was bored on some long flights over the last few weeks and started going through performance numbers and the possible fuel savings with different climbs/cruise/decent speeds as well as cruise altitudes. I am wondering what other carriers have as a "best burn" climb/cruise/decent profile.

Here is our "published" climbs:

Best Climb 250/.70M
Normal 290/.74M
High Speed 320/.77M

I was "experimenting" or maybe better to say "interpolating" with climb rates with slight variations to these climbs and found that using 270/.70M kept us at 700-1Kfpm all the way up and saved a couple hundred pounds of fuel and only cost us a couple mins of time. 280/.70 wasn't much difference in fuel but didn't change the time. The problem I have with the 290/.70M climb is the plane just dies after about FL250 trying to hold 290. At about FL250 you will indicate roughly .70M so you could climb at that speed and still be well above the 250IAS limitation for a climb and maintain more than 500fpm up. Trying to climb at 250IAS all the way up seems to have 2 big problems- 1) ATC will hate you and 2) Through FL180 at 250 the plane is a dog!

As far as cruise I have been looking at winds and such and many times we are legal and able to go up 2K and many times 4K feet with a lower fuel burn and many times the winds aren't much different and we even go faster. This is something that all pilots look at (well most), but my issue is why does dispatch/the company not look at this in the planning process. It does seem to work out better to level off at FL280 (an example for original filed ALT), pick up some speed, then continue up to FL320.

Decents for us are typically 290IAS and we have the Vnav set at 3.0degrees. Fiddling with 3.5degrees kept us higher for a little longer and still gave us the ability to slow to 250 for ATC (of they need us to) but we decend with a much lower power setting and save some fuel.

I have been going through various flights and charts and find that just a few changes will (many times) reduce burns by 300-500lbs on a 2 hour flight. At $110+/barrel gas I am curious why others haven't really started looking at burn numbers. You are talking about $100/hr savings which isn't huge, except when you look at the big picture- thats Alot of $$$..


Now I am fully aware the company published numbers probably came from Bombardier and I am sure there are many engineers and lots of science behind all the numbers, but many times the book says one thing and reality is another- we all remember the GA days of a Cessna that should climb but really won't! I am really just curious what other carriers do for the climb mainly. Also curious what people do on the ground (APU and single engine taxi procedures).
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Vader

You'll be getting a new book from Delta in the next few months. It has the best fuel saving numbers for a given weight, Alt and temp.

flyandive

Comair has the top secret PPAS. Basically a book with the most optimum numbers for our old aircraft. Generally 290kias until we reach the cruise mach which could be anything from .65 to .74 depending on weight, temp, and wind and then we'll climb at that mach until cruise then that could be as fast as 0.8 with a strong headwind. Also during the climb if we need to get higher or maintain a certain climb rate it allows us to fly really slow. 250 is the min without the book but with the book it is much slower. It also has a section for descent.

higney85

Yea.... let the good times begin...

schone

A very interesting topic indeed. However, I only have one little problem with your numbers.... Our limitation calls for a min climb speed of 250KIAS to the point where it marries .70M. That only occurs at roughly FL320.

So for all our tight captains that seem to see you climb at 250 and .67M at some odd level (say.... 290...) and then get all antsy and tell you to speed up to .70 because that's what our book says.... NEWSFLASH!

That only occurs at FL320 and only on the longer flights the mach becomes a limiter for our climb speeds.

BoilerUP

I too experimented and got to where I used IAS 290 until the climb rate dropped below 1000fpm, then climbed in VS mode at 1000fpm to cruise altitude. Normally the IAS would be around 260-270 when you leveled off if you were going FL300-340, and I never saw lower than 250kts. I found it got you to altitude in a reasonable amount of time and still with enough airspeed on the wing to allow acceleration to .74M or higher under all conditions (well, without cowls anyway).

saab2000

I usually try to fly what our training "Guru" wants us to fly - 290 until .70 and then .70. In "Climb" mode. Yeah, it sucks maintaining 290 and a decent rate above about FL220, but by FL250 you have .70 and then follow that up and the climb rate is actually not bad. Besides, if you climb like that you usually have some reserve indicated speed in case ATC asks you to expidite.

higney85

I don't know about that one... What alt will you indicate (roughly) .74M and 290IAS... about FL280. I was up at FL340 and FL360 this past week and we were just below the 250IAS but we were doing well above .70M. I never was below 250IAS or .70M in the climb up to FL360 although our initial level off was FL300 and we let it accelerate before climbing and climbed at 500fpm for a healthy margin above .70. I will keep looking but keep in mind mach transition is actually different depending on temp and the aircraft (at least how I understand it). The CRJ transitions at 31,600 where our planning is FL280 and higher a .74M cruise. I may be wrong and this is the point of discussion so keep the comments coming. I am debating on making a formal proposal to Flight Standards about this. This would be fun to deal with in addition to the new checklists... yea we are getting another checklist revision (a few actually). I personally like the changes...


I also have no problem bringing out documentation to prove a CA wrong. Safety is first but keep in mind many of the crusty guys only flew tprops before the RJ. I have flown with some guys who want to stay low just so they have a "margin". I am not condoning anyone go outside the aircraft's operation envelope, yet utilizing the aircraft to max efficiency should not be a topic of contention. I will do some more research myself but the RJ does have a large operation envelope. I just wish it had another 1000lbs of thrust per side and fadec. I guess I will need to fly the -900....

mooney

actually it isn't the "tight ass CA's" fault. It is usually training dept. Any CA who has been here a few years will tell you some of our procedures/systems knowlegde have changed about 6 times since we got the RJ, its kinda hard sometimes to keep up with all those.

"married" is not a word used in the CFM. The word is "transition to." Therein lies the problem. At what altitude do we transition to mach? F280. Therefore, with the way our CFM/training dept. has worked in the past, this can be interpreted as min of .70 when transitioning to mach at F280. However, several chapters later it does say in plain english, 250 or .7, whichever is less.
In addition, if the CA want you to fly faster for better margins, that's his perogative, so long as you're not bustin a limitation. He's the head honch, big cheese, numero uno...
Lots of new FO's have no respect for the slow speed performance/deep stall characteristics of this aircraft. I'd rather see 15 knots fast on a sloppy approach than 5 knots slow and no effort to correct. Or flying at .7 instead of 250 in the climb because you cant look up every few seconds from you USA today...

mooney

"As far as cruise I have been looking at winds and such and many times we are legal and able to go up 2K and many times 4K feet with a lower fuel burn and many times the winds aren't much different and we even go faster. This is something that all pilots look at (well most), but my issue is why does dispatch/the company not look at this in the planning process. "


2 reasons. Our SOC has always been stuck in the saab era, even tho we havent had them in 6 years. Hence going to MEM-HSV at 14000 when you could easily do mid 20's and burn less fuel and get your true airspeed up.
reason 2...they give you whatever the computer spits out, with no human thought process involved.