A320 Power Set...

[EMER_CANC]

Two quick questions:

What does your company specify as tolerance limits for the prior to 60 knots "power set" callout on takeoff?

Does Airbus specify any tolerance limits for this callout?


Thanks PPRUNERS
EC

[TopBunk]

We have A320 CFM and A319/320/321 IAE engined 319 aircraft.

The Flying Manual does not specify limits for the IAE engined aircraft (or I can't see them!) maybe due different FADEC systems?, but on the CFM engined A320's we enter any difference of greater than 1% N1 in the Aircraft Log.

There is no guidance that I can see as to when to abandon, personally I would probably use about -2% as a trigger to set TOGA, and then abort if original planned N1 not achieved.

Having said that I can remember taking off at TOGA from a short runway and seeing a Vib level of 7 units on a CFM engined aircraft, and continuing beyond 80kts with the Vib levels reducing to 3-4 units by V1/Vr and then 1-2 units in cruise. Probably a lot to do with the infrequent need to use TOGA.

[FlapsOne]

FCOM 3.5.6

Check that the actual N1 of the individual engines has reached the N1 rating limit, before the aircraft reaches 80 knots. Check EGT.

Also says they should be within 1% of each other.

I read that as it should match the Flex or TOGA value calculated.

[Sawbones]

I agree. With us, if N1 is 1% or lower below the required/calculated limit when at 80 knots, the call by the PNF will be "Low Power" and the take-off will be abandoned.

[TopBunk]

Flaps1

You 'read' it that they should meet the calculated number....what if they are 0.8% less N1, 0.3% less, 0.1% less? Are you seriously saying that you abort take-off? I think you would be wrong, having said that I feel it to be a weakness that FCOM doesn't specify explicitly what is acceptable.

[mcdhu]

Fuel flow can be a help here. On the CFM 319 at SL, Toga ff is circa 3600kg/hr and at max flex about 3050kg/hr. I am not saying that you can use ff to decide what you are going to do if the actual does not match the predicted, but it might help you to decide what best to do - along with the host of other things that flash through our minds in a situation such as this.

Cheers,
mcdhu

[A-3TWENTY]

I think it`s necessary good sense..
You have to consider...
-All other paramaters
-obstacle clearance
-if you are on main base or out of.

I think if you have all this paramaters OK,you continue your flight and report to maintnance at arrival..

[idg]

On the IAE we have to call "power set" between 60 and 80 knots.

The lower value is to allow the EPR to 'grow' to the T/O value which will only happen beyond 60 knots.

Your discussions about N1 are interesting. On the IAE when the FADEC calls for an EPR, that is what you get regardless of the N1s. I suppose that we would never see a low EPR because the fuel will just be pumped in until the EPR reaches the rating. If we were over the limit for N1. N2 or EGT then we would see an ECAM.

If there were an EPR probe fault then it might be possible to get a mismatch on the N1s etc, This would then be a clue that there was incorrect thrust being produced, along with the assymetric effects and the smaller speed trend vector.

[EMER_CANC]

Thanks..

It nice to know that at least CFM specify tolerance limits. However, the IAEs differ. I just can't seem to find a tolerance limit or maybe it does not exist. Either way, there has to be some acceptable EPR range for continuation for takeoff!

I have heard of at least one European carrier operating IAEs using 0.01% EPR as a guide. However, neither can I locate the origins of this number, nor can I verify its truth.

Thanks PPs

EC

[alf5071h]

A human factors presentation at a recent safety conference suggest that the ‘Power Set’ call be modified to include the value of the thrust parameter, i.e “Power Set, 95%” or “Power Set, 1.66”, N1 / EPR value depending on engine type. The reason for this was that the call would improve the situation awareness of the pilot flying and provided a safety crosscheck that the correct setting for take off had been achieved i.e fewer ‘seeing what you expect’ mistakes. The addition of the ‘value’ call enhanced the crew’s picture of what was intended / expected, provided a quicker comparison with the pre take-off set up, and added to the crew’s experience level of what normal setting would be for the particular operation, thus aiding the crew’s diagnostic or comparative capability in future operations.
Do any operators already use a power set call that includes the value?
Mcdhu, and others, I don’t know about the Airbus operation, but there could be dangers in using other engine parameters to support the check of the take-off power setting. Noticing discrepancies of other engine parameters may add or detract from safety; e.g. do you have an SOP to call these deviations, if so what are the limits of the deviations, and what would the response be? The use of other parameters may aid a decision to reject, but they may also confuse the situation.
My understanding of the certification requirements are that the ‘performance’ thrust value must be checked before take off, and that providing it is within limits there should not be any noticeable deviation in the other engine parameters (limits required again). If there were deviations then the crew could (may) treat these as a lower (insignificant) risk with regard to a high speed abort. Thus use of the words ‘power set’ to indicate that the thrust levers are in the correct position is incorrect; the power set (+value) call should indicate that the required (certification) thrust value is within limits and that any creep remains within limits.
Again, do any operators have any SOPs on this issue?

[mcdhu]

Alf - I was careful to add a clear government health warning about all this. We can dream up scenarios until the cows come home, but in the abscence of clear information in a situation, we need as many inputs as we can reasonably cope with. Interesting discussion though!

Cheers
mcdhu