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zachlog

Managing Takeoffs Fenix A320 CFM vs. IAE Engines

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I have noticed a difference managing and configuring takeoffs with CFM vs. IAE engines.  There are two areas on which I need some feedback:

  • Takeoff Configuration- With the CFM frame, the EFB-recommended optimum flap configuration varies depending on TOW, runway length, etc.  I have seen optimum flap configurations from flaps 1 to flaps 3.  With the IAE frame, I have yet to see a flap configuration other than flaps 3; it's always flaps 3 regardless of airport and runway length.  Has anyone else seen this ?  Any suggestions, feedback ?
  • Initial Climb and Speed-  With the IAE frame, the A/C seems to have difficulty maintaining its speed after rotation to avoid a stall.  On a couple of occasions, the A/P disconnected (I had engaged it at about 1000') and I had to lower the nose to avoid a stall then gingerly raise the nose to resume the climb and re-engage the A/P.  The initial climb just seems trickier with the IAE frame.  Anyone else seen this ?  Any feedback managing the IAE vs. the CFM frame ?

Thanks

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zachlog

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Can't comment on the flap setting - I don't recall exactly what performance calculation results I've been getting on CFM versus IAE.

5 hours ago, zachlog said:

With the IAE frame, the A/C seems to have difficulty maintaining its speed after rotation to avoid a stall.

I've never seen this issue. I would suspect a conflicting control configuration or thrust lever calibration issue.

Can you post a screenshot (PFD and upper ECAM) during the takeoff phase when you're seeing these issues? I'd like to confirm autopilot modes and engine indications. 

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Excellent question !  Looking fwd for "professional" insight !!!

Been there too....


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5 hours ago, zachlog said:

I have noticed a difference managing and configuring takeoffs with CFM vs. IAE engines.  There are two areas on which I need some feedback:

  • Takeoff Configuration- With the CFM frame, the EFB-recommended optimum flap configuration varies depending on TOW, runway length, etc.  I have seen optimum flap configurations from flaps 1 to flaps 3.  With the IAE frame, I have yet to see a flap configuration other than flaps 3; it's always flaps 3 regardless of airport and runway length.  Has anyone else seen this ?  Any suggestions, feedback ?
  • Initial Climb and Speed-  With the IAE frame, the A/C seems to have difficulty maintaining its speed after rotation to avoid a stall.  On a couple of occasions, the A/P disconnected (I had engaged it at about 1000') and I had to lower the nose to avoid a stall then gingerly raise the nose to resume the climb and re-engage the A/P.  The initial climb just seems trickier with the IAE frame.  Anyone else seen this ?  Any feedback managing the IAE vs. the CFM frame ?

Thanks

Both of your problems arise from the fact that you use config 3. Config 3 is hardly ever used in real life. The reason the EFB suggests config 3 is because the calculations are bugged; you should always use config 2 (legacy carriers) or config 1+f by choosing it manually.
There's another bug with flaps 3 which makes you almost stall on takeoff. Not sure if it's a an aerodynamic issue or a wrong EFB flex value, but it's so bugged that you will crash into any obstacles behind the threshold with the given values for flaps 3.

So tldr: Avoid config 3 for takeoff.

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I only fly the IAE version so can’t help with comparisons.

I’ve seen both flaps 1, 2 and 3 as a result of the T/O calculator, with most often 2, then 1 and very rarely 3.

There’s an acknowledged problem with the SRS not guiding you to V2+15, but only V2. I,ve seen this on a few flights, but the team is looking into it.

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I use toga when efb calculate conf 3 for TO.

Maybe iae is less power than cfm 


Frédéric Giraud

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2 hours ago, grandfred29 said:

I use toga when efb calculate conf 3 for TO.

Maybe iae is less power than cfm 

I think they take a bit longer to spool up. But at Vr I assume the thrust is similar. Others are probably far more knowledgeable on this.


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4 hours ago, Fiorentoni said:

Both of your problems arise from the fact that you use config 3. Config 3 is hardly ever used in real life. The reason the EFB suggests config 3 is because the calculations are bugged; you should always use config 2 (legacy carriers) or config 1+f by choosing it manually

This is the key here.  There was a YouTube video posted recently (I believe by a real world Airbus pilot) explaining this and how you should generally only use 1+F or 2…only using flaps 3 if 1+F or 2 do not give you safe takeoff speeds.


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Posted (edited)
4 hours ago, Fiorentoni said:

Both of your problems arise from the fact that you use config 3. Config 3 is hardly ever used in real life. The reason the EFB suggests config 3 is because the calculations are bugged; you should always use config 2 (legacy carriers) or config 1+f by choosing it manually.
There's another bug with flaps 3 which makes you almost stall on takeoff. Not sure if it's a an aerodynamic issue or a wrong EFB flex value, but it's so bugged that you will crash into any obstacles behind the threshold with the given values for flaps 3.

So tldr: Avoid config 3 for takeoff.

Flaps 3 is used quite a bit especially one carrier in the UK. It’s not a bug. Obviously the airline they have the data which mostly go for opt and spits out flap 3

“There is no one method of calculating take-off performance. The current implementation is based from one real world operator which optimises for TOPL, which in some cases doesn't make a lot of sense, but is what the real one does for various other reasons. Because of this you'll generally see flap 3 because the maximum take-off weight in that configuration is usually higher than if you'd be using flap 1+F.

In such cases where your desired take-off flap is different to the one that the "OPT" setting produces then just manually select the flap setting.”

 

 

Edited by carlanthony24

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Posted (edited)

Flap 3 is a valid take off computation, especially when optimising for TOPL as the EFB does. Some other airlines do not use this optimisation and instead optimise for other factors - hence they never land up with F3 takeoffs. To say it is a bug for providing the computation is probably a bit far. I will do a bit more research into the actual behind the scenes here, however. 

4 hours ago, SierraDelta said:

There’s an acknowledged problem with the SRS not guiding you to V2+15, but only V2. I,ve seen this on a few flights, but the team is looking into it.

SRS guides you to V2+10, the system does this in the background whilst speed target remains at V2, so visually it "looks" a little weird but the FD is not guiding you to that speed. You can see it here: 

 

Edited by Aamir
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Aamir Thacker

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4 hours ago, grandfred29 said:

I use toga when efb calculate conf 3 for TO.

Maybe iae is less power than cfm 

IAE is more powerful.

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4 hours ago, Fiorentoni said:

Both of your problems arise from the fact that you use config 3. Config 3 is hardly ever used in real life. The reason the EFB suggests config 3 is because the calculations are bugged; you should always use config 2 (legacy carriers) or config 1+f by choosing it manually.
There's another bug with flaps 3 which makes you almost stall on takeoff. Not sure if it's a an aerodynamic issue or a wrong EFB flex value, but it's so bugged that you will crash into any obstacles behind the threshold with the given values for flaps 3.

So tldr: Avoid config 3 for takeoff.

I agree.  The calculations in the EFB are probably buggy and I suspected this is the case simply because for the IAE frame I have yet to see an OPTIMUM EFB-recommended flap setting other than flaps 3.  What surprises me is that for the CFM frame, the OPTIMUM flap recommendations vary and they tend to parallel my expectations per the runway length, etc.; not the case for the IAE frame.  I think now I am at a point where I can make a flaps 1+F vs. a flaps 2 decision for safe takeoffs.  Thanks again.


zachlog

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Posted (edited)

Wow, I didn't know Flaps 3 was ever used for take-off. You learn something new as they say. It seems like a lot of flappage* for take-off.  I've always used Flaps 1+F in both engine models, except when close to MTOW or on a short runway.  But I innocently and naively choose the flap take-off myself 😊   I use all of the rest of the TO data in the EFB but just assumed the F3 suggestion in the IAE was a bug.    I guess an A320 taking off with F3 would be similar to a 737 taking off with around flaps 25?

*made up word

Edited by JYW
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Bill

UK LAPL-A (Formerly NPPL-A and -M)

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Posted (edited)
12 hours ago, zachlog said:

Any suggestions, feedback ?

No one forces you to use the suggested configuration of the calculator. Just pick Flaps 2 or 1+F and recalculate.

Edited by Farlis
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There seems to be a few different methods. I tend to use whatever flap setting the EFB recommends, for both IAE and CFM variants. Don’t recall that it has given me any problems so far.

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