Elapsed time and chronograph

[Will]

Questions about real-world line operations.

I assume the chronograph is used for short-term timing of things you need to keep track of, such as flying a hold with one-minute legs, or making note of  how long the captain can hold his breath.

Q1: Are there instances in various airline SOPs where use of the chronometer is required? If so, what are they?

In contrast, elapsed time is probably most useful for things like fuel calculations while enroute. Therefore...

Q2: Do SOPs require this to be set to RUN at pushback? Engine start? At "line up and wait?" Or at the beginning of the takeoff roll? Do different operators have different requirements for when ET is set to RUN?

[double-alpha]

According to my A340 SOPs :

We are required to use the chrono for these situations :

1) PM starts the chrono when PF set the thrust levers to FLX or TOGA, to ensure that the maximum time with the engines at T/O thrust is not exceeding 10 minutes.

2) for manual engine start procedure, when N2 reaches the maximum monitoring speed (20% minimum) PM starts the timing in order to monitor the light-up duration.

3) for circling approach, when wings level after the break, and when the aircraft is abeam RWY threshold, start the chrono.

There are various cases when you can use the chrono :
A fuel leak is suspected, your collegue is taking a nap etc, you starts a fuel crossfeed etc...

For fuel calculation (at each waypoint) you don't need the elapsed time. You just need to check Fuel on board FOB (ECAM) and fuel prediction (FMGC) and compare with the computer flight plan.
Check that FOB + FU is consistent with FOB at departure

I never need elapsed time (in the old days you had to start the elapsed time when you release the parking brake before the Pushback, and stop it at the gate park brake ON) because it is automatically calculated by an ACARS function (the flight time as well, from T/O to landing)

I am in the middle of a 787 type rating course, I use the chrono even less than when I was in the a340

[Will]

Thank you! That's very interesting and helpful.

[Jeroen Hoppenbrouwers]

Recently I was on a bunch of 777s and whereas half the fleet had standard clocks just as the 744 and many other Boeings, the later half didn't have a clock at all. It took me a bit to spot the chrono and ET readouts at the bottom of the PFD, as small numbers only. Clearly modern procedures don't really rely on clocks any more.


Hoppie

[Roddez]

I was under the impression that the clock is what is used to set the time in the FMC on the 747-400.  There is an ARINC 429 output on the clocks.

Now that all aircraft had GPS units, is this still the case?

I also saw some versions of the clock that accept and ARINC 429 feed and will set the time based on the FMC.  I assume the FMC gets its time from the GPS.

Rod.

[Hardy Heinlin]

The 744 FMC can get its time from the GPS units and from the pilot clocks. So it has some backups. The GPS has the priority, then comes the captain's clock, then the F/O's clock.


|-|ardy

[Will]

So it looks like the elapsed time is a feature of the clock that has been made redundant because of more sophisticated, more durable methods of measuring time since the flight originated. While this does make perfect sense to me (after all, we no longer use our sextants for in-flight celestial navigation), does anyone disagree?

[Hardy Heinlin]

I would use it anyway, as a backup.

It's just one flip of a switch, and I like to flip switches.

[Britjet]

My airline would start the elapsed time as we rolled. The only other times that the stopwatch was used (usually) were:
1) Manual engine starts - one side does starter motor timing, other sure does time to light-up.
2) Fire bottle 30-second timing
3) Advisory timing for alternate leading or trailing edge extension.
4) Anything else!

Peter.

[Avi]

Wasn't there, back in time, a procedure to start the chrono at FAF (or other specific point) when starting the final approach (descent) in bad weather and if by X seconds (depending on speed) runway was not in sight, a go around was mandatory?

Cheers,

[Britjet]

Avi, ah - yes! And of course it would still apply if flying one of the old raw-data NDB or VOR approaches, probably with a time/altitude table also on the approach plate.
Other uses might be -
Timing "controlled rest" (yes, they really do covet those few minutes!).
Flying a manual hold (God forbid). Unfortunately that also requires small-planet-sized mental agility!

Any others?!
Peter

[double-alpha]

Wasn't there, back in time, a procedure to start the chrono at FAF (or other specific point) when starting the final approach (descent) in bad weather and if by X seconds (depending on speed) runway was not in sight, a go around was mandatory?

Cheers,

Timing During Approaches (with the 787) :

Since FMC use is appropriate for instrument approach navigation, timing is not the primary means to determine the missed approach point. The probability of multiple failures that would result in timing being the only method of determining the missed approach point is remote. However, some regulatory agencies may still require the use of timing for approaches. The timing table, when included, shows the distance from the final approach fix to the MAP.

Timing for instrument approaches is not necessary as long as there is no NAV UNABLE RNP alert displayed.

[Phil Bunch]

Should the instrument panel be required to have a panel of about 5-10 timers?  I think it would be necessary to provide timer labeling (through a keypad or perhaps a pull-down menu)...  If the timer(s) are flight-critical, I suppose they would need all sorts of confirmation before stopping or resetting them.

Without such a multiple timer system, how could the pilots run more than one timer/chronograph at a time?  For example, what if I need to use a timer to estimate fuel burn rate at the same time as I am timing some other activity or event?  I guess that the copilot would need his own dedicated bank of timers.

[Holger Wende]

Hi,

What about EICAS advisories, warnings etc.
Some messages seem to require to monitor elapsed time since a message appeared.
See also e.g. the Airbus A340 EMERGENCY - Engine Failure video at https://www.youtube.com/watch?v=rEf35NtlBLg  at 2:10, oil temp between 140° and 155° for more than 15 min.

Question: Do pilots "automagically" start timing when certain messages pop up?

Thanks, Holger

[double-alpha]

Hi

Absolutly, when something non-normal occurs and you don't know what to do, it is a good practice to start your timing.

But in your video (very interesting), it is the condition (oil temp between 140° and 155° for more than 15 min) that triggers the ECAM caution ENG OIL HIGH TEMP.
The crew don't have to monitor this condition for 15 min.
They only must do the ECAM actions when the caution appears on the ECAM, 15 minutes after oil temp reached 140°.
If the crew notice that oil temp goes above 140° (no ECAM message at this time), they may start their chrono, but a good thing according to me is to write down the exact time at which the anomaly has occurred (because you may have to start your timing for another reason during these 15 minutes).

But usually, electronic check-lists (Boeing777/787 and Airbus) displays a timer.
The xx minute or second timer starts from the point the checklist was displayed or a specific action is performed (for example, with the 787, in case of engine fire, the timer starts for 30 sec when the crew rotate the engine fire switch. If after 30 sec the FIRE ENG message stays shown, you must rotate the switch to the other stop)

[Will]

with the 787, in case of engine fire, the timer starts for 30 sec when the crew rotate the engine fire switch. If after 30 sec the FIRE ENG message stays shown, you must rotate the switch to the other stop

I live and work in a world where most of the incoming tech "fixes" actually end up making the user experience worse. It's very discouraging.

However, the idea that the checklist starts a timer and then prompts you to do something after the right amount of time has elapsed actually seems like a brilliant idea.

One has to wonder why other circumstances aren't automatically timed, like the 10-minute TOGA limit described above.

[double-alpha]

I think the a340 is nowadays rather an old plane, and the a350 has probably a lot more interesting new electronic features .
And the 10 minutes-toga is used for an engine out takeoff (it is 5 minutes for an all engines takeoff). Maybe it is the reason?

In a 787, the crew can read the elapsed time from the auxiliary display just next to the PFD.

If you are interested, have a look at the digital clock and checklist timer for the « airbus like » 787:

https://www.dropbox.com/s/9k4706e7l4gxumr/Photo%2025-09-2019%2C%2013%2038%2018.png?dl=0

https://www.dropbox.com/s/twv5lpqf9e5mmwn/Photo%2025-09-2019%2C%2013%2041%2048.png?dl=0