Dani,


I think they invented a parameter called "thrust" on the A380, whereby 0% represents idle and IIRC 100% represents the maximum possible thrust for the current flight phase...
Seems quite comfortable and intuitive to me...

Excellent! :ok:

Hopefully all future types and versions will have that.

I'm not sure if this has already been touched upon but,
EPR is an indicator of actual thrust.
An EPR of say 1.15 is associated with XX,000lbs of thrust at sea level and at the same FL200.
However, an N1 fan speed of say 60% will correspond to a higher actual thrust value at sea level than at FL200.
That being said as a pilot you want to be able to be able set a thrust lever angle that gives you the thrust you need to maintain your required speed alt etc.
N1 gauges are easier to use but the EPR is more accurate.
I wonder if anyone has ever considered setting the EPR as a function of its scale and not the number.
Say EPR needles at 9 o'clock to reduce from high speed.
Or say 10 oclock for flap full MLW VAPP ETC.
nyone with me?

FLX/MCT
Zero is not idle thrust. Zero is zero idle is ahead of that.

I had started a thread about IAE and CFM engines I had observed following shortcomings of IAE engines:
CFM VS IAE Engines A320
IAE engine takes longer to start than CFM. Also thrust response to thrust levers appears sluggish as compared to CFM.
IAE engine as you open thrust for take off appears bit noisier than CFM.
IAE has fan flutter that is why there is KEEP OUT ZONE between certain RPM when applying take off thrust while there is no such thing in CFM. IAE requires or puts on ignition for more conditions than CFM.
IAE engine for circling approach OEI and flap3 is seven tons more weight restricted than CFM for circling.
IAE engine aircraft have Flap full with flaps at 40 while CFM engine aircraft have flap full with flaps at 35. I don't know is it because engines size or shape.

Having flown for 3 years with an operator having a mixed fleet of IAE and CFM engines, this is what I perceive as discernable difference between the IAE and CFM engines, in addition to what has been already elucidated in this thread.
1) IAE has higher thrust idle, hence as a pilot you'd have to apply brakes considerably more during taxi. Leads to frequent usage of brake fans to keep the brake temperatures under control. The difference is significantly noticeable when with the parking brakes on, you feel that the aircraft is constantly pushing against the brakes, causing a bobbing motion.
2)IAE has higher start time compared to CFM due to the extended motoring to get rid of an unique problem called 'Bowed rotor condition'. And the idle time required before take off after a cold start is higher compared to CFM.
3) IAE is much more noisier compared to the CFM, though as a pilot I'd complain because, pun intended, I'm made more aware of the thrust changes without having to look down at the gauges.
4) IAE gives you a remarkably lower fuel consumption compared to CFM engines.
5) The target speed achieving characteristic of the ATHR on the IAE engines was inferior to the CFM ones, though I've my suspicions that it's the software standard of the specific ATHR that makes it look that bad.

IAE's lesser fuel consumption may come from the fact that it is under powered. CFM has many thrust variants so may be the lowest one has higher consumption as compared to IAE. Requirement of KOZ, Ignition, fan flutter. bowed rotor, not a hallmark of a better engine.

In addition to what has already been said, the Engineering folks in my company were of the opinion that IAE engines had a longer life time compared to the CFM engines. I'm not sure if there's empirical data supporting the argument. Can anyone support or contradict the same?

IAE vs CFM
 

IAE:

Better deceleration by the reverser
Lower fuel / ENG oil consumption
Had the "feeling" of more Thrust in high density altitudes


CFM:

Quicker ENG start sequence
N1 engine instruments are easier to handle vs. EPR

Regards!

Would anybody have any data for thrust available from these engines at normal cruise level?I think around the tropopause it should be about 20% of max sea level thrust.

I think it should be a little more, shouldn't it ?
Thrust should not decrease faster than atmospheric pressure, else you're not gonna be faster at altitude.
You're gonna be slower because of greater drag (due to greater Coefficient of Lift required)

CFM used to have that information on its website, but thats been dumbed down considerably so try wikipedia...

CFM has higher thrust at higher levels and the drift down ceiling with OEI is at least 5000ft. higher than IAE.

I have been flying the A319 with IAE V2500-A5 and CFM 56-5B and some protoype A320 with CFM 5A engine
(double digit msn).
Additionally to the items mentioned above:
1. V2500s stink. Doing an outside check shortens your live. I try to hold my breath when nearing a V2500. Sometimes you see the vapours rising from the oilbreather or lingering near the fan
2. V2500 AP speed control is sluggish. But when a speed just above green dot is selected you have the occasional "TOGA" thrust surge to gain 5 knots of speed.
3. Speed deceleration is slower on IAEs due to high idle setting and the slightly smaller engine diameter.
4. During landing you need to retard the throttles (yep I am aware its called thrust levers, spent my formative years on a boeing) earlier on the V2500 than on a CFM otherwise the AC will float.
On the CFM retarding the thrust levers early might result in a firm touchdown.
5. In gusty conditions the IAE engined aircraft seem to react more sluggish than CFMs. CFMs react prompt
BTW Our company policy is "manual flight, manual thrust" and raw data is encouraged. Never done an A/THR landing in real life except during autoland.
With regard to EPR, I use fuel flow as prime parameter when flying IAEs. Values are the same across both fleets for all intents and purposes.
All be said I prefer the cfm.
Speaking to our engineers low oil and fuel consumption for the IAE seems to be a valid argument.

Flew several thousand hours on V25A1 and CFM.
V25 was generally unreliable in service and always 'felt' fragile.
Met a design engineer at a party years ago who had been involved with the hot section.
His comment " yeah, I think we were trying to be too clever with that engine"