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Xplosion2002

What are the chronometer used for in the 737 in the real world

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Hello,

 

Recently I have been on youtube and watched some real boeing 737 take-off and land and all that. I see them use the  chronometer ALOT. As soon as they start the engines they start the chronometer, when they take-off, when they land. I was wondering why they use the chronometer so much. If any of you know when and what the chronometer is used for (Ex: Chronometer starts after engine start up so the engines have time to get ready for take. IDK) I would like to use the clock instead of it being decoration.

 

 

Thanks,

 

Jack Roberts

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what the chronometer is used for

 

It's used to time things  :P

 

What it's used for is all up to company SOP or pilot preference. I personally rarely use it. I know FS2Crew will start it (in the 777 - not sure about the 737) when you announce "takeoff." This would obviously count the time since the departure roll. Others use it block to block (parking spot to parking spot). Another use might be to time an instrument approach (kind of antiquated, but still used).

 

It's kind of asking "what do you use a hammer for?" Well, you use it to hit things...

...but AAA Handyman Services uses it to hammer grommets onto things, while Harry's Homebuilders uses it to hammer nails into wood.

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My usual list:

 

APU start

Bleed air

Light off

Cleared for T/O

Engine cool-down

 

Some add more for things like T/O thrust limit.

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It's used to time things  :P

 

What it's used for is all up to company SOP or pilot preference. I personally rarely use it. I know FS2Crew will start it (in the 777 - not sure about the 737) when you announce "takeoff." This would obviously count the time since the departure roll. Others use it block to block (parking spot to parking spot). Another use might be to time an instrument approach (kind of antiquated, but still used).

 

It's kind of asking "what do you use a hammer for?" Well, you use it to hit things...

...but AAA Handyman Services uses it to hammer grommets onto things, while Harry's Homebuilders uses it to hammer nails into wood.

I see. Is there anything like a flows and procedures booklet that would have anything in there about when to use the clock. Someday I would like to use the clocks.

My usual list:

 

APU start

Bleed air

Light off

Cleared for T/O

Engine cool-down

 

Some add more for things like T/O thrust limit.

two questions 1) for bleed air when do I turn it on and off 2) what do you mean by light off.

 

 

Thanks,

 

Jack Roberts

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two questions 1) for bleed air when do I turn it on and off 2) what do you mean by light off.

 

The APU should run for at least one minute before opening the APU bleed valve.  During the engine start if there is no light off, indicated by EGT increasing, within 10 seconds of moving the start lever to idle an aborted start is required.

 

After landing the engine needs to run at idle or taxi thrust for three minutes prior to shutting it down.

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Don't forget that the FARs require a chronometer for IFR flight, back in the day we always used ET on final approach.

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I'm not sure about using the clock to time engine starts, etc. But in instrument flight navigation, it's important to know what time you will arrive, which requires knowing what time you left and adding ETE to that to get an ETA at your next and subsequent fix.

 

I know that the ND has computed arrival times fo you.. but what if the ND failed and all you had was a hard copy of the flight plan (with estimated time enroute between fixes- after all the hard copy was generated in dispatch before you left and doesn't know what time you will depart. So you would start the elapsed timer when you departed and then be able to get your ETA's. After all you you need to make a compulsory report to ATC if you deviate within limits from the ETA on your flight plan (actually TAS)- but if you are at a compulsory reporting fix you need to know the ETA at the next fix and the one after that.

 

In the little C172 that I fly- at least the one with steam gauges- the only way I know how much fuel is in the tanks is using fuel-burn tables and the clock, since the fuel gauges are useless. (In an airliner you will have a reliable indication of fuel weight.)

 

Also, a clock "with a second hand" is a required equipment (MEL) for instrument flight.

 

 

Thanks, Bruce.

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I set the timer at the Takeoff-Roll and if you use PFPX like me, i then check the minutes on the timer against PFPXs minutes column and see how much i'm late or early on my PLOG.

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Timing for start up might be operator specific, but some have the procedure to start timing once the start valve is open to monitor the starter duty cycle, plus you can time the ten seconds mentioned above for the no ignition case. Nevertheless I doubt many actually do this.

 

Also some start the timer once take off thrust is set to monitor the take off thrust time limit. A good time to switch it off again would be the reduction to climb thrust.

 

ET can be set from take off until landing.

 

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In the past  it was used to check the time from start of roll of take-off to V1

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