Question to Airbus 320 and 330 Pilots/Engineers

[Netset]

From an operational and technical point of view, are there any significant differences between the CFM56 and the IAE V2500 for the Airbus 320 family?

The same question goes for the Airbus 330 which offers three engines (GE CF6-80E; Pratt&Whitney PW 4000; and Rolls-Royce Trent 700). Going through their respective websites, as expected, all three claim to have the best engine for the job.

Thanks

[SKYYACHT]

From an operational point of view there are one or two very obvious differences. Firstly, the CFM is a slightly older engine, and uses % of N1 (Shaft speed) as a primary performance gauge. The IAE V2500 series uses Exhaust Pressure Ratio (EPR) to gauge engine performance. To all intents and purposes, once crews are familair with idicated output power, the engines are operated in a similar manner.

With regard to starting, the procedures vary quite a lot. Both engines use a Full Authority Digital Engine Control (FADEC) which monitors all engine parameters. However, when starting the engines normally, the Autostart system is used.

When auto-starting V2500 engines, they will perform a dry crank for between 30 to 50 seconds (according to model and operator) before fuel is injected and ignition activated. This is to allow any unburnt fuel to be purged from within the cowling, and to allow all of the compressor baldes to settle down before putting the engine under load.

The CFM engine lights up without performing a dry crank, and simply puts ignition on at 16% N2 and fuel in at 22% N2.

Operationally, the fault handling on the engines via the ECAM system is essentially the same.

CFM engines are much more susceptible to cold soak, and normally require a run up of up to 70% N1 for 30 seconds prior to take off, whilst the V2500 does not have the run up requirement to my knowledge.

So, As far as I am aware, the selection of power units will depend on operator choice (ie., what are they currently using, are they operating on a "power by the hour" basis etc. etc.), or what incentives the manufacturer is offering at the time.

In my 'umble opinion, the V2500 is a slightly better unit, as it seems to offer better economy for thrust.

Hope that helps!


Blue Skies
:ok:

[Spearing Britney]

In my totally personal and neccessarily subjective view based on my operational experience of both engine types on the 320 and 321 the CFM would be my choice every time. Why? Firstly, IAE takes longer to start which can be a pain when making for a slot etc. Second, the CFM has less restrictions on run time prior to and after landing - KISS. Third, in icing the CFM needs less care - mainly not poorly predicated run-ups like the IAE. Fourth, autopilot and autothrust speed control is (subjectively) better with the CFM's. Fifth, when using manual thrust its easier to glance at the top gauge on the CFM and set an approximate power to sort out things if they are getting out of shape - EPR's mean little to most pilots I know who look down the the N1 even on the IAE's. Sixth, they look better on the wing!

I have also heard that the time on wing is better for the CFM and that this makes up for the different burn at cruise. IAE has a lower bypass ratio so is better in the cruise, CFM better low down. I guess IAE's suited to operators with long sectors and CFM's to short hoppers - what did Easy go for?

[lomapaseo]

A couple of points.

I believe the dry start procedure being referred is to pump oil in the oil damped bearings in order to get rid of a shaft critical speed vibration during runup and a resulting blade tip rub deep in the compressor.

I believe that the icing procedures are meant to be the same on both engine models since they both operate in the same conditions and under the same regulations. Differences may be operator interpretations rather than engine manufacturer caused.

However all subjective comments above, still stand even though probably the bean counters and engineering maintenance chiefs make the decisions of what's best:O

[Jet II]

probably the bean counters and engineering maintenance chiefs make the decisions of what's best

Engineering very seldom get a look-in - the beancounters rule everything now I'm afraid:{

[Port Strobe]

I believe that the V2500 engine is offered with an extra surge of power available on take off (I think its called "bump", not 100% though). In the words of someone who described this on another post I remember reading somewhere, it sh*gs the life out the engine, which would suggest to me that the V2500 produces less power, but I don't know that for sure, especially as its the more modern engine. This is activated by a small red button on the back face of the thrust lever (possibly just the no.1 thrust lever at that, for both engines).

Hope this is of some use to you, depsite lacking the exact details, but I'm sure it does affect matters from an operational point of view.

[Spearing Britney]

Just to clarify the icing procedures I referred to were ground run ups not use on bleed air for anti-icing. The former differs, the latter is the same.

As for Bump, yes its as you describe but on (A4??) an intermediate version of the IAE, the newest (A5???) just have more go to begin with. Bump is a bit of a pain and drastically shortens the life of the engine between overhauls. Again due in part to the bypass ratio of the IAE being low to optimise it for the cruise not low level ops. Bump was occasionally needed to comply with GA criteria at places like Salzburg and to have it available for that eventuality we had to use it on departure irrespective of its need then! Silly! I did like having little red 'turbo' buttons though :O

Anyone else found speed control with automatics in to be better with CFM's?

[Groaner]

I think the relative desirability depends on which particular model of CFM or IAE is being used.

The later ones have better thrust-specific fuel consumption and (so I hear) better maintenance costs.

As to thrust ratings, that's a whole different topic. An engine can have different max thrusts depending only on paperwork filled out (and a large fee paid).

[Netset]

Any info regarding Airbus 330 engines would be greatly appreciated