Go around thurst and MCT

[md-100]

Does the GA thrust have a limit time or it acts like the MCT???

[Mad (Flt) Scientist]

If it's the same thrust as TO (its sometimes called TOGA) then the same limitations will apply.

If its a different rating then the manual should give limitations.

I find it hard to believe anyone's using MCT as their go-around thrust, since it's leaving performance 'on the table'.

[fantom]

TOGA is full thrust and is time-limited (rules for Yankees differ from Europeans' rules).
MCT means what it says: Max Continuous.
What don't you understand?

[BizJetJock]

Your theory sounds very simple and logical. However, we sit in the cruise scratching our heads over the fact that on the ThrustLimit page on the FMS our cruise N1 is higher than MCT N1....:confused:

[Mad (Flt) Scientist]

In such circumstances I suggest you check the Powerplant Limitations section of your Flight Manual and regard that as authoritative. If it says Max Continuous is below the supposed cruise N1, I'd be reluctant to go above the book MCT, without knowing a lot more.... wouldn't be the first malprogrammed FMS.

[Piltdown Man]

It depends on your engine. RR suggests that for the Tay 620/650 (when fitted on Fokkers) that the TOGA thrust can be used for 5 minutes N=2 and 10 minutes for N-1 and MCT is exactly what it says on the tin.

PM

[BizJetJock]

Oh, we've done that; it says see ThrustLimit page in FMS!! More interesting is it adds a caveat that FMS figures are only valid if two ADC's are functional, but gives no advice on setting cruise thrust if you lose an ADC. Good game!
To answer the original question though, on my aircraft the answer is - it depends. Since we have flat rated engines GA N1 may or may not take the temps over the normal limit. If they don't, then there is no limit. If they do then we are time limited

[Empty Cruise]

Guess your CRZ is higher than GA as per FMC N1 LIMIT page during cruise because CRZ is calculated as per actual conditions, and GA is calculated based upon landing field elevation + parameters entered on the DES FCST page.

Try the same exercise on the ground and enter a low level as your cruise altitude - that should produce a CRZ N1 well below the GA limit.

If not - :confused: :sad: :confused:

[barit1]

Raw N1 (physical rpm) isn't a useful number for comparing performance in widely different conditions (cruise vs airfield elevation & temp).

A performance guy/gal could correct these values back to standard day conditions and give you a rational basis for your observation. Good question to ask the OEM - and you may not be the first to ask the question. :8

[Max Angle]

I find it hard to believe anyone's using MCT as their go-around thrust, since it's leaving performance 'on the table'.No need to use full power for an all engines running go-around. The 737 (and probably other Boeings, never flown them) gives you 2000fpm at the first push of the TOGA buttons and full thrust with another push which made things much more manageable. Unless there is a specific note giving different go-around profiles for engine out and all engines the performance is worked out for the engine out case (normally 2.5% gradient) which you will more than meet with all engines running. The Airbus system means you have to use TOGA to get into the correct mode but you can come back on the power before accel. attitude if you want to.