A320 Improved Climb.

[420]

Just a question that has been like a splinter in my mind...

In my airline,we tend to use improved climb with flex thrust quite often. but im just wondering whether its the same in other airlines or is it a "last option"?:confused:

it seems risky to me to be using it as it is absolutely high speeds for weights that we can use normal take off speeds. And based on the lift formula,it seems like at improve climb speeds,the aircraft wants to take off way way before V1 but we're practically keeping it on the ground. :eek:

And some excuses that i've heard is that they use improved climb at high flex temps to actually save fuel due to lower thrust settings....which seems absurd as once again...high speeds which are unnecessary and also...

lower thrust settings+longer time on ground VS high thrust+ less time on ground = same thing!:bored:

or am i wrong?

appreciate some words of wisdom here. personallly i'd rather do a take off with packs off and normal take off rather than improved climb.

example of a case i've seen...

take off weight = 69500
possible to do normal climb with TOGA for a weight of 69700 which speeds are around about 125++

pilot does improved climb with flex52 with speeds of 155++!

WHY?:confused:

[Dream Land]

Can't give you a bunch of technical information about performance but I think you'll find that MOST operators operate in a similar manner, this saves engine reserve, not fuel. As the engine gets older, the reserve margin gets smaller, although it's not our SOP, I normally due a packs off T/O above 35C to help engine life.

[airseb]

this last is the answer, the fuel is nearly balanced. but the engines cost more (about the third of the price of the aircraft). so the logic is to use the runway length as much as possible (that's where you get the balanced V1 concept)

and also you should see the graph of the engine failure occurence vs the flex temp setting. it's an exp graph meaning that a bit more degrees means a much bigger failure rate.

seb

[DesiPilot]

420,

You will actually burn more fuel by doing a flex take off compared to a TOGA take off. So your company is not doing it to save money, rather they are doing it to extend the engine life (wear and tear).

Our company policy is to perform Flex take off except the first flight on the first of every month, where it is mandatory to perform a TOGA take off.

[Canuckbirdstrike]

DesiPilot:

You are technically correct that less fuel is burned to climb to 1500 feet at TOGA vs. FLEX, but the amount is negligible. The wear and tear on the engines of a TOGA thrust creates considerable engine maintenance cost because the engine ends up coming off for overhaul sooner.

However, the NET fuel burn is less with FLEX. With FLEX since engine wear is less the incremental fuel burn for engine wear is less i.e. Fuel Burn Correction factor. That affects each flight for the entire flight and results in significant savings.

Sometimes we need to stand back and look at the total net fuel impact and not isolate analysis by phase of flight.

[Dream Land]

and also you should see the graph of the engine failure occurence vs the flex temp setting. it's an exp graph meaning that a bit more degrees means a much bigger failure rate by airseb Great information, do you have any links to this information, cheers.

[PantLoad]

According to the "Getting to Grips with Aircraft Performance" (a really nice publication from Airbus), TOGA takeoffs are slightly more fuel-efficient than FLEX takeoffs. As far as long-term effects of engine wear, yes, it's true, a tired engine burns more fuel...and the engine gets tired quicker when doing all TOGA takeoffs. So, I guess an argument could be made that, in the long term, TOGA takeoffs really are not much more fuel efficient compared to FLEX takeoffs. But, a discussion of this really starts to get banal.

Personally, I pretty much take what Airbus publishes as gospel truth.

Now, regarding the question concerning improved climbs.... Let's say, at a given weight, you have enough runway to do a FLEX takeoff with the maximum allowable FLEX temperature. And, let's say that, not only do you have enough runway to takeoff with maximum FLEX (under the conditions of weight, temperature, runway elevation, etc., etc.)...but, you still have thousands of feet of runway extra...on top of that.

So, If you have a zillion meters of runway to play with, but need only half a zillion to takeoff with max FLEX....and operations tells you that they want to load a couple of tons extra of freight....no problem...

So, you still may not be runway limited...because you have a zillion meters of runway at your disposal (accelerate-stop, or accelerate go to the end of the first segment....and, let's assume for this discussion that you're not tire speed limited)... But, now, you're second-segment climb limited with the flap setting you are planning to use that is related to your desired FLEX temperature and the other conditions as stated above.

OK...having said that....you could reduce your FLEX temperature....despite the fact that you have more than enough runway at the maximum FLEX temperature...you reduce the FLEX temperature to get a better second-segment climb at your new, heavier weight. (By the way, freight is a very profitable part of flying.)

Or, you could use up even more of the runway (which you have plenty to spare)....and get a 'jump-start' on the climb...to get an increased second-segment climb gradient...since, from your reading of the Airbus "Getting to Grips with Aircraft Performance" publication, you'll note that increasing the V2 speed will, to an extent, increase the angle-of-climb....again, "to an extent"...since, increasing the speed to 980 kts will give you less of a second-segment climb gradient that what you'll have with the improved climb situation.

So, if you have a lot more runway than you really, but are second-segment climb limited, and you still want to get as much FLEX as possible to save the engines...this is what you do.

All this assumes that you have RTOW charts for all of this...making it legal, safe, and OK to do without soiling your underpants.....



Fly safe,

PantLoad