High Speed Climb more efficient?

[Dani]

Our management has urged us to fly our A320 in high speed climb due to fuel conservation matters (if ATC allows it). Asia doesn't have a strict FL100/250kts rule. So as soon as you rise the flaps, you accelerate to around 300 kts.

Is it correct, that you safe fuel which this strategy? I would assume that the fuel flow on lower levels is much higher, so you should climb first.

Does anyone have tables to support this for the Airbus family?

Thank you for your help,
Dani

[Dream Land]

Our SOP is CI=35, this will give us a 280 kt climb without the speed restriction, by that logic a lower CI should give you a higher climb speed but we know it doesn't, awaiting more information. :confused:

[fireflybob]

Dani

There is a (small) fuel saving if you immediately accelerate to en route climb speed as soon as the aircraft is clean. It is a little late after a long day so the theoretical reasons for this do not come to mind but I am sure someone will post to re-educate us on this!

[misd-agin]

Let your FMC calculate it for you. Enter 250kts to 10,000' on the climb page and one with no speed restriction.

757 saves about 100 lbs of fuel and 1 minute of flight time by removing the domestic U.S. restriction of 250 kts below 10,000'

[alexban]

From what I know,you will save fuel arriving asap at cruise level.On the 737 the best rate climb is around 250 kts.The 737 is capable of high ROC,and we use 250 bellow FL100 ,which usually give 3000-4000 feet/min ROC ,and accelerate to around 290-300 kt (CI -30) over FL100 with a resultant ROC of around 2000-2500 f/m . This way we can exit fast the TMA, and get shortcuts in busy airspace,like LHR,FCO,CDG,VIE..
One other point -after few bird strikes at low altitude with high speed, they'll change for sure this policy. Do a serarch for the AA 767 in CDG ,bird strike years ago,resulting in depressurization ,at FL120 ,right after acceleration. Or ,are there no birds in Asia?:E

[captjns]

I can only quote from the Boeing planning and performance manual. The 737-800 assumes a climb speed of 280 knots. Climbing at 250 below 10,000' which is required in the US about 25 kg additional fuel will be consumed.

The 727 and 757 are better if you climb the aircraft at their best climb speeds based on current gross weights rather than the standard 280 knot speed.

[Iceman49]

It works great until you hit a bird below 10000' and greater than 250kts. Several web sites out on the problem.

[gimmesumvalium]

For fuel efficiency:
1. IN A JET, Achieve Best Rate-of-Climb Speed (varies with weight) ASAP so that you get to your OPTIMUM alt ASAP. Overall fuel burn will vary depending on if you are climbing into a headwind or a tailwind.
2. Above 10,000ft is NO guarantee that you are not going to have a birdstrike. This is a somewhat arbitrary figure based on stats. I personally have had a birdstrike at 21,000ft while climbing at 290 knots. Very fortunately, a glancing impact on the side of the fuselage.
So, you need to define your criteria.

[gimmesumvalium]

Econ Climb is based on weight & Cost Index. CI is a relationship between fuel costs and time-based (maint, engs, deprec etc, maybe lease also) costs:
More fuel = less time
Less fuel = more time

Econ Climb is based on your operator's cost structure, whereas Best Rate-Of-Climb is based on aerodynamic efficiency based on your performance manual.

Would pay to read your Perf Man, also, if Boeing, there is valuable information in the FCTM (Flight Crew Training Manual).

[huckleberry58]

http://www.wingfiles.com/files/systems/fueleconomy.pdf

Take a look at the table on page 35.

[411A]

Personally seen at KRT on the ramp, some years ago...

A B727 that had a bird strike at 4000MSL, while doing 340 KIAS.
The bird went through the radome, forward pressure bulkhead, broke the First Officers left leg, went through the FD door, and what was left if it ended up in the FC lounge area.
Not a pretty sight.

Sometime that haste to go fast has unintended consequences.

[llondel]

Haven't there been sightings of some of the larger avian species at over 30000ft? Admittedly somewhat lower probability of hitting one, but something the size of a swan or goose would make a bigger mess at Mach 0.8 or more.

[fireflybob]

Haven't there been sightings of some of the larger avian species at over 30000ft? Admittedly somewhat lower probability of hitting one, but something the size of a swan or goose would make a bigger mess at Mach 0.8 or more.

Since 1st Jan 2007 all avian species with a mass greater than 2 kg flying in RVSM airspace are required to be fitted with a functioning mode S transponder, TCAS and also fully trained to deal with TA/RAs as notified by EU directive AV/SPEC/SQWAUK/SPLAT 2007/ SI 95 (BS). France have notified a difference prohibiting all avian species movements in the French UIR.

[VORDME2]

For the best fuel economy,cost index 0 (this is max range,at least on B767/57)and climb at the given speed (econ speed)..

[robin747]

post #8/10 both can be referred to, diff. model nos will have diff affect on efficiency. In a large b744, with no restriction on speed after clean up saves 700kg at the min as per the perf manual.

[javelin]

320/321/330 - if you want to save time and fuel, forget high speed cruise - doesn't save anything really.

Clean up - accel to 340/330kts depending on type, climb at that until you reach your cruising mach - switch to mach, climb increases once you switch to mach - stay at cruise mach as per CI, reverse for descent.

Works a treat :ok: