A330 Thrust reduction altitude

[South Prince]

Hi 330 drivers, I fly B767, been a pax few times on RR powered A330 with same Airline recently and noticed engine revs actually increase at thrust reduction altitude. I'm a bit confused by this. Thanks for any answer coming.

[flyboyike]

You may notice the same thing next time you are on an E170/190. I suspect for the same reason, but I'll let the Bus guys chime in first.

[NOLAND3]

Simply because in 'some' situations the selected flex temp will give a lower N1 then the full rated climb thrust. Once you select the CLB detent at thrust reduction alt you will get an increase in thrust.

It has nothing to do with the engine type.

[South Prince]

in 'some' situations the selected flex temp will give a lower N1 then the full rated climb thrust



thanks, could you describe the situation when take off thrust is allowed to be lower than climb thrust?

[NOLAND3]

Not my words however here is a quote from a previous post on this subject a while back..

Here's the reasoning at our operator - We lease the engines on a 'Power by the hour' agreement from the manufacturer. Prior to 1000' AGL the manufacturer gives credit for de-rated or assumed temperature takeoff power reduction. That equals less cost to the airline.

Above 1000' AGL these 'credits' end. At this point it saves fuel to climb to the optimum cruise altitude as fast as possible using maximum climb thrust. Again, equalling less cost to the airline.

This is true for a CFM-56-7 power plant under a power by the hour agreement on our 737NG.

[FE Hoppy]

You may notice the same thing next time you are on an E170/190. I suspect for the same reason, but I'll let the Bus guys chime in first.

Really?

The minimum flex takeoff thrust is limited to 75% maximum rated takeoff
thrust or CLB-2 + 1% N1, whichever is higher.

and

Whenever
the selected takeoff thrust is lower than CLB-1 the CLB-2 mode becomes
the default until the next airplane power down / power up.
Manual switching between the climb modes is possible anytime in flight
on the MCDU - TRS page.
On ground the CLB-1 mode is inhibited if the take off thrust selected is
lower than CLB-1 thrust.

Would suggest not. :-)

[B350-900]

Now can FLX further to 34% of total rated thrust.
Some manefuctore were not ready for this, and missed up,

IF FLX thrust is lower than CLB THR, CRZ THR rating should be selected @ THR REDU ALT.

[flyboyike]

Not sure what you're getting at, Hoppy. Last leg I flew (less than 20 hours ago) on climbout I made the call "Flaps 1, Climb 1". The PM went to the TRS page, selected CLB 1, and the engines revved up rather than down.

[FE Hoppy]

From CLB 2 to CLB 1. Not from TO to CLB.

[OPEN DES]

A320 family:
Between mach 0.30 and mach 0.40 the Climb thrust rating increases. On an airbus fbw Flx can never be less than CLB. To cater for high flex reductions, CLB thrust is limited at low mach. Normally during flap retraction a thrust increase is noticeable as the aircraft accelerates.

I would imagine that on the 330 it must be similar.

Brgds

[South Prince]

appreciate everyone's reply. the flight condition where the rev up was noticed is at thrust red altitude, with further climb at constant speed up to accel altitude. Just hope "Derate and Flex" was not mixed up. safe flying to all.

[flyboyike]

From CLB 2 to CLB 1. Not from TO to CLB.


You may have missed my point. The sound change from FLX to CLB2 is very slight. From CLB2 to CLB1, on the other hand, it's quite noticeable.

[I-2021]

Hi South Prince,

noticed engine revs actually increase at thrust reduction altitude

That can happen in case of a highly derated takeoff with an associated full climb thrust.

Cheers.

[Natstrackalpha]

Perhaps, that instead of climbing in Managed, and waiting for the spd to build up at cruise altitude, when they levelled out - they decided to go for something like . . . 340kts, at a lower level in the climb, like here at thr red alt ok? and hold that spd 340kts until level at cruise, at which time - they would not have to accelerate. If all of that was below 10,000' they could have done that if ATC let them do it.

Say CRZ IAS330 TAS564 = JSA -56.6 (default)+15=- 45.6 deg C = then the crew have set themself up nicely for Mach .81 cruise . . ? see? You also cover more ground in the climb, you also climb more readily, and you also use more fuel, but, you save on time to accel = 0
you save on accel fuel at alt = 0 Hence the sound you heard -

If you can work out how much fuel you burn climbing up to FL330 at 340kts and how much fuel you`ll save AT FL330 already doing 340ktsIAS plus the fuel thus saved in the performance climb - then maybe it could be worth it - but all in all, they would be further, faster, and faster sooner.

[Natstrackalpha]

nobody likes this do they . . .?

[SloppyJoe]

I bet they were not going for 340kts in a 330. Climbing at 340kts till FL330, bet you don't cover more ground in the climb as it will take you longer to get into high TAS levels. 340kts at FL330 really?

If you don't know the answer why answer the question?

[Natstrackalpha]

fine, fine, fine, That was really clear sloppyjoe.

Maybe the crew had got a Direct to - then - that portion of the flight plan consisted of a higher TAS, having chomped out all the interim waypoints in the Direct To process - the Flt Pln settled in in the new higher speed, then.:rolleyes:
whats wrong with 330 . . ? Anyway, are we talking TAS or IAS? Is that too fast? Or not fast enough? What are you saying? I worked out the Goddam figures, what more do you want?

[Natstrackalpha]

well logically, if you take longer to climb and you are going faster then you cover more ground in the climb........!:O

See? I told you nobody would like this.

If you don't know the answer why answer the question

If you cannot understand the answer why pose an argument? and, and, if you time it right you need not go into the barbers pole you can climb just below it and keep it there throughout the flight until TOD, try it with 320 knots then.

[Lord Spandex Masher]

FE Hoppy, not to question your Embraer knowledge but I do distinctly remember an increase in N1 from take off thrust to climb thrust. It happened rarely, I can't remember actual numbers as it's over two years since I flew the 195, but it definitely happened.

I can't remember if we selected CLB1 as a matter of course after acceleration, or not.

[SloppyJoe]

Anyway, are we talking TAS or IAS?

You were talking about 340Kts IAS in cruise. Obviously you do not know what you are talking about, especially regarding an A330.

well logically, if you take longer to climb and you are going faster then you cover more ground in the climb........!

Again you show that you do not know what you are talking about, you mentioned 340kts IAS in the climb, lets assume you meant 320kts IAS. In a 330 you are right it will take you longer to climb. You will be lower for much longer doing your 320kts resulting in not that much better TAS for quite a while. Meanwhile I will have climbed in about half the time to FL330 and be sitting there with a GS of 500kts, you will only be doing about a GS of 400kts by then.
Who travels the furthest in the time it took you to climb at 320kts?

If you cannot understand the answer why pose an argument?

I understood your answer but what you are saying is wrong and shows a total lack of aviation knowledge, its obvious you don't do this for a living. So once again if you don't know what you are talking about why bother answering someones question?

Maybe the crew had got a Direct to - then - that portion of the flight plan consisted of a higher TAS, having chomped out all the interim waypoints in the Direct To process - the Flt Pln settled in in the new higher speed, then.

This is helping to prove the point, if you don't know what you are talking about why try to answer a question?

[South Prince]

Hi again, few months have lapsed but recently came across an A330 FCOM perf section; any comments from 330 flyers?

From page PER-TOF-THR-FLX-30 P 1/.....

‐ Thrust must not be reduced by more than 25 % of the full rated takeoff thrust.‐ The flexible takeoff N1 cannot be lower than the Max Climb N1 at the same flight conditions.

[Luke SkyToddler]

At my previous employer (which features a large purple goat on the tail) it was SOP to set D2 climb as part of the FMGS setup unless particularly heavy - and it was very common for the guys to clear the derate and go to normal full power climb shortly after thrust reduction.

Sometimes with a heavy amount of flex on takeoff and a D2 climb set, there is virtually no change in the engine power / engine noise at thrust reduction altitude, as you move from the MCT to CLB detent.

I suspect the power increase you're hearing is not actually the "thrust reduction" move from MCT to CLB detent - it's a few seconds later when the pilots clear the D2 climb and it powers up to normal climb.

[sonicbum]

Deliberately going against the SOPs in the goat airline ? Bad boys:cool:

[South Prince]

Thanks Luke, same gazelle:ok: