A320 T/O question

[Two6Left]

I've noticed after watching a lot of reduced thrust takeoffs on the A320 that once the PNF calls Flex "xx" SRS Runway and Autothrust on they then lean forward and cancel a button.
Can someone tell me what it is and why.

Thanks
:)

[Beavis and Butthead]

It's the 'chrono' button which is the Airbus name for a stopwatch. There is a limit to the time that the engines can remain at take off thrust so that's why we start the watch at that point. Only really becomes an issue should we experience a loss of thrust on takeoff and want to keep take off thrust for longer than normal.

Hope this answers your question.

B&B

[togsdragracing]

So can I ask the dumb question: say for the sake of argument that take off thrust is 100%, when you've finished climbing and are happily cruising, at what % are the engines then?

[Beavis and Butthead]

Not a dumb question at all.

We rarely takeoff at full power (TOGA) but use what's called a FLEX takeoff. This simply put is just a reduced power setting to preserve engine life when the runway doesn't require the use of TOGA power. Even at TOGA power the thrust is reduced soon after takeoff. In the cruise the thrust is normally around 84-87% depending on weight and speed.

Hope this answers the question.

B&B

[Dan Winterland]

There is no time limit at ''take off power'' if flex is used. There's a time limit to use TOGA power of five minutes (10 in an emergency)*. Stopwatches were often started at the commencemnet of the take off roll to accurately time the flight time for the maintenance log entry. However, the advent of ACRS and the OOOI page, there is no necessity to do this. It's not in our SOPs, yet, half the pilots I fly with still do it.

Personally, I only do it if I select TOGA.



*(These figures are for the V2500. I don't know about the CFM56.)

[HPbleed]

Keeping a lookout whilst doing a visual approach isn't in your SOPs either I bet, it's airmanship, something you're taught during training. I tend to start the chrono so that IF we have an engine failure, or windshear or any other situation that requires TOGA during the T/O run or soon after, I know roughly how long I have been using it for, without having to worry about taking my hands off the thrust levers once I have selected TOGA. I tend to start the ND chrono and the internal clock chrono, but cancel the ND chrono at thrust reduction altitude. I leave the internal clock running in case of ACARS failure to be able to record T/O and Landing times.

Max time at TOGA with both engines operating is 5 minutes, single engine 10 minutes. However, there's a reason there's a limit and if you only have one engine running anyway, you may want to think about reducing thrust back to max continuous asap.

[togsdragracing]

B&B, only just seen your reply for which many thanks.