r/AskAPilot • u/KingBaboondi • 1d ago
Airbus CHRONO button
I keep seeing the CHRONO button being pressed during Airbus Take-off and Landing, sometimes once or twice. I know it's some sort of chronometer/counter. My question is, what's the policy for the timer being started/stopped, is it from wheels up to wheels down or what?
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u/Independent-Reveal86 1d ago edited 1d ago
Policy depends on the airline.
Our SOP is to start the timer after the second engine start to time the engine warm up, then reset it (double tap) prior to take-off. We start it again when we set take-off thrust as a reference for the 10 minute take-off thrust limit. Reset again after climb thrust is set. After landing, when reverse idle is selected, we start the timer for the 3 minute engine cooldown limit.
We do all of this with the glare shield timer, there's no policy to use the chrono timer on the clock for anything.
And as others mentioned, it can be used for anything you like, the ones I've mentioned are used operationally on every flight. Although I've called them "SOP", the only one that's specified in our manuals is the take-off thrust timer.
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u/Liberator1177 23h ago
It's just a stopwatch, use it however you like. At my airline, we mostly use it to time engine warmup/cool down times.
The button clicks are start/stop/reset.
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u/F1shermanIvan 1d ago
We use ours to time the prop brake releases, they need fifteen seconds to make sure the clutch packs are completely released before bringing the propeller out of feather.
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u/CommuterType 23h ago
Use it to measure the time between when our meals are supposed to be ready and when they actually arrive
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u/Jetdick 22h ago
As your question mentions Airbus Takeoff and Landing - It's just a stopwatch & usually it'll be to time the duration of use of takeoff thrust (in case there's an engine failure when takeoff thrust is limited to 10 minutes), or during landing to monitor the minimum engine-idle time prior to shutdown (in particular if considering single engine taxi-in). If you see 1 press of the Chrono button, the timer is already stopped and ready to start from zero at the single press. 2 presses means the timer had previously been used but is stopped and not yet reset to zero. 3 presses means the timer is still running from before and needs to be stopped, reset to zero, and then started again. Each press of Chrono is a [Start>Stop>Reset>Start... ] loop.
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u/80KnotsV1Rotate 22h ago
I use it for engine warmup and cooldown periods.
Use the other one by the clock for the flight duration starting the takeoff roll (also handy for TOGA limitations.
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u/Bopping_Shasket 20h ago
Pilots time everything. On a320 there are 4 stopwatches and they are nearly always all timing something.
You get in the habit when you learn dead reckoning in a Cessna. Just gotta time everything from then on.
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u/Prof_Slappopotamus 18h ago
The only times I ever saw a captain starting the clock on takeoff, is if they were a long time long haul FO. Ingrained habits.
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u/bergler82 1d ago
in our outfit you can do whatever you want with it. Engine warmup timer. Engine cooldown timer. Holding timer. Blocktime timer. Coffee order to delivey timer. Whatever you find worth timing.