So, I wanna ask a kind of silly question. When I fly the 747, and I am starting the pushback I start the ET timer. So far so good, when I start the takeoff roll I then press the clock button on the glareshield which is a stopwatch essentially. Now, I know it from the NGX or Airbus that once you reach one hour it goes 01:00 but the 747 just goes 60 and then up to 100. How am I supposed to read it? Do I actually need to calculate how many hours I've flown based on GMT time and then add the minutes of the stopwatch?

I hope somebody can help me with this, It has been really messing with my mind lately :D

There are two functions that you may have confused.  The elapsed timer is generally used for time since takeoff, since this is important in estimating the ETP points, and the stopwatch or timer is commonly used for non-precision approaches or to time holding (without a FMS).  The  stopwatch will rollover at 60 min, the ET timer keeps on going for as many hours as you are airborne. The FCOM is the first place to look when you want to know how something operates.... use Ctrl+F 'clock' or go directly to pg 10.10.95.

No silly questions, but you should be signing your full name on every post as requested by PMDG forum rules.

Oh yeah I did forget about the signature. What I mean is, you have the rotary knob on the clock itself which reads ET, I always thought it would be running from gate to gate. Then you have the clock button on the glareshield, as in the NGX, which goes up to 100 and then resets in the 747. (I'm flying in the NGX right now and I see here it resets at 60, in the 747 at 100). So the clock button on the glareshield is used for holdings or something similiar, and the rotary elapsed time switch gets activated seconds before take off, do I get that right?

Kind of makes sense, doesnt it... 

Depends. Personally I always run the elapsed timer from pushback (and that is SOP in the Big Airline) as block time is what goes in the logbook/tech log etc. 

Your mate in the other seat could run their elapsed timer from the takeoff roll. Either way, generally speaking both off-blocks and takeoff time is noted on the flight plan and the latter used to monitor flight progress.

The stopwatch as mentioned above would be used for timing short-period things: raw data NPAs (!)/circuits or indeed very useful for non-normals (e.g.timing 30 seconds between firing fire bottles/motoring engines, or another good use is to set it running if you ate extending the flaps in secondary mode - 1-5 takes about 4 minutes, so if you set the watch running when you make the selection you have a good indication of how far through the process you are).

3 minutes ago, skelsey said:

Depends. Personally I always run the elapsed timer from pushback (and that is SOP in the Big Airline) as block time is what goes in the logbook/tech log etc. 

Your mate in the other seat could run their elapsed timer from the takeoff roll. Either way, generally speaking both off-blocks and takeoff time is noted on the flight plan and the latter used to monitor flight progress.

The stopwatch as mentioned above would be used for timing short-period things: raw data NPAs (!)/circuits or indeed very useful for non-normals (e.g.timing 30 seconds between firing fire bottles/motoring engines, or another good use is to set it running if you ate extending the flaps in secondary mode - 1-5 takes about 4 minutes, so if you set the watch running when you make the selection you have a good indication of how far through the process you are).

It's funny you mention the 30 second wait for the fire bottles and what not.

When we do these things in the sim, it's one hell of a long 30 seconds...

 

I was just wondering, as in the videos I watched where I wanted to see what they press on the clock I actually never saw a pilot reaching out to the actual clock and starting the ET Timer...

Anyway thanks for the answers :)

On the B744 the elapsed timer is normally started by both pilots moving the SET selector on the clock to RUN at the start of the take-off roll i.e. immediately before the handling pilot applies the thrust for take-off.  It is then left running for the rest of the flight - hence 'elapsed time'. 

The chronograph or stopwatch is used as part of the normal operation and also in an emergency, usually by pressing the CLOCK button on the side of the glareshield .  The stopwatch function replaces the elapsed time as long as it is left running and it is used to time things like the outbound leg in a hold, procedure turns etc and as Simon and others have said  in an emergency to time the engine fire bottle discharge 30 secs before firing the second shot.   

4 hours ago, ahsmatt7 said:

It's funny you mention the 30 second wait for the fire bottles and what not.

When we do these things in the sim, it's one hell of a long 30 seconds...

 

Yep, and it feels even longer on the aircraft when an engine really is on fire!

Bertie Goddard