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Coldbear
20th Dec 2009, 18:37
Hi,

Looking for some silver haired captains who can help me understand the indications on the E/WD and general engine handling. I am rated on the A320, but haven't flow it for a while (yes one of the unfortunate)
I am also helping the developers making a very realistic simulation of the A320. (see AirSimmer (http://www.airsimmer.com)) This inevitably means that there is some questions that is not readily explained by the FCOM.

(All in ISA conditions and I am looking at both engines)


- When we climb up the EPR increases to maintain a constant N1 (V2500 engine), but why? and still the N1 is not really constant as it increases a little bit up to 5000feet and is then constant to about 17000feet where it starts to fall. This is all based on data from the FCOM

- The Max EPR, the amber line. Am I right it falls when we climb up? or does the Climb limit increase up to the Max EPR?

- If you put the thrust levers all the way forward the thrust will go up to the Max EPR limit?

- Can someone tell me the Max EPR/N1 for different altitudes if it changes, otherwise if the Max EPR/N1 is constant what is the value then?

Thank very much for you help,

Martin

Coldbear
27th Dec 2009, 19:57
Is there realy no one who knows :\

Martin

rudderrudderrat
29th Dec 2009, 21:54
Hi Coldbear,

Let's call the inlet pressure P2 and the fan exhaust pressure P5 and EPR = P5/P2.
I'm sorry but this is just from memory of TriStar RB211 EPR behaviour :-

1) EPR reduced during take off with constant N1 and with increasing airspeed due to the increase in the P2.

2) With constant IAS and climbing (into less dense air) the EPR increased.
(P2 remains constant but P5 increases due to the V squared value of the airspeed of the fan exhaust airflow.)
We set a reduced climb power initially (Climb 1) until the rate of climb fell below some value, then set an increased power (Climb 2). Maybe your V2500 has a schedule like this as it blends from a climb power which was set from the flex take off value?

3) I think Max climb EPR increased with Altitude.

4) The apparent reduction in EPR of your V 2500 between 8,000 and 12,000 feet is probably due to accelerating from 250 kts to something around 300 kts.

On the TriStar, there was no FADEC so you could over boost the engine by pushing the TLs forward. Your V2500 is probably protected by the FADEC under normal operations.

Regards, RRR.

Dani
29th Dec 2009, 22:45
Problem is that hardly any V2500 A320 pilot ever looks on the EPR gauge ;)

It's so useless, because difference between min and max EPR lays maybe in a quarter of the gauge. So most of us look at the N1, some on the FF.

Other than that, I would also guess what RRR said in general about the dynamics of a modern jet engine, and I also agree with you that:

- the amber line will fall with alt
- with TOGA thrust you will reach the line
- the EPR limits change with altitude

What the values are - I guess nobody knows, because that's different to atmospheric conditions. If you get hold of an FCOM, maybe you find tables about it?

All the best for your project,
Dani

aidey_f
1st Jan 2010, 11:47
That level of detail of the engine dynamics are covered by the models that Airbus sell as part of the simulation data package, and that make up a very large portion of the price of your level D sim.

They're also covered by some pretty strong non-disclosure agreements, and in the area of engine controllers, the information is export controlled. Indeed, the license agreements are so strict that only specified people who have signed the agreements are allowed to see the data and models. Breach of these licenses can lead to multi-million dollar fines for the company involved and criminal prosections for the companies and people who breach them. It would also make vising the Home of the Free and the Land of the Brave somewhat problematic, seriously upsetting plans to take the kids to Disneyworld, causing severe turbulence on the domestic front... anyway, I digress.

Hence you're probably going to find a great deal of dificulty getting public domain information.

Good luck though - I hope I haven't rained on your parade too heavily.

Coldbear
2nd Jan 2010, 14:45
Thans guys for the answers, especially to RRR and Dani.

Martin