TWAtwaTWA
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How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:04 am

I always find it amusing when the captain announces "sorry for the late departure today ladies & gentlemen, we will certainly do our best to make up time in the air to get us there earlier."

Occasionally, less knowledgeable co-passengers have commented to me- what does that mean- make up time? Why can't they make up time all the time and just make flights shorter?!

Of course we all know that A/C have optimum cruising speeds to maximize fuel economy. Do any of you pilots or industry insiders have any idea how much fuel economy suffers when airspeed increases? Does ground control have any authority on the flight speed? Is there ever a reason to slow down the plane for scheduling or fuel economy issues? thanks
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fbk
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:08 am

I am no expert, but i have had chats with many pilots that say there is as you say a perfect crusing speed and altitude range for the particular aircraft.

Generally your pilots will say make up time to just smooth the air over inside the cabin, it makes people feel better, but might also mean there is a tail wind that night.
 
flyf15
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:20 am

In general its all made up. The plane isn't flown any differently at any greater of a speed. Its just that with schedule padding, you still have a window to help you arrive "on time". When your flight goes as scheduled, you don't realize you're early arriving. When it is delayed, it looks awesome that the pilots "made up time" in flight and got you there on time.
 
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Crosswind
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:30 am

The airline I work for does not recommend pilots to fly faster than normal cruise speed to make up for a delay unless there are special circumstances; ie destination airfield is about to close or crew are limited by hours to complete the flight.

Flying faster burns a disproportionately large amout of fuel when weighed against the time saved, in the order of several hundred kilos of jet fuel to save 2 minutes over a 4 hour flight on the 757 - it just isn't financailly worth doing it.

In fact the airline recently reduced the cruise speed on the 757/767 fleet on flights of under 5 hours to M0.78 from M0.80. The time penalty on those flights is 1-4 minutes per sector but the total fuel savings over the course of a year are huge. The A320/321 fleet already cruise at M0.78 as standard.

Incidentally, the classic "took off late, landed early" scenario is often nothing of the sort but a misunderstanding of scheduled departure and arrival times...

All airline scheduled time of departure and arrival times are push-back/on blocks times and include taxi times before takeoff and after landing and usually a few extra minutes to account for other factors such as en-route weather etc.

A flight that is scheduled to leave at 09:00 and arrive 11:00 that takes off at 09:15 and landed at 10:50 neither took of late nor landed early - it probably pushed back bang on time and arrived at the gate exactly as scheduled!

Regards
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commavia
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:38 am

Well, in addition to seeking a faster route or getting clearance for a different routing or altitude, another major function of "making up time" in the air is often the fact that even if planes depart late, they still really have enough time to land on schedule, thanks to schedule padding used by most airlines.

Quoting TWAtwaTWA (Thread starter):
Do any of you pilots or industry insiders have any idea how much fuel economy suffers when airspeed increases?

Sure, but airlines often have to make the decision about what costs more -- greater fuel consumption or a delayed plane perhaps delaying other flights and leading to misconnects throughout the day. If the delay is too far in either direction, meaning the plane is so close that padding will easily cover it, or so far off schedule that there's no point in pushing the fuel for shaving a few extra minutes off, the airlines probably just decide to stick with the routings and speed they have. However, in certain instances, when the difference could be close, airlines sometimes may decide its worth it to push the plane and get the aircraft on to the gate at the destination on time, especially if it is a "time-critical" flight, like an early morning departure that will ripple delays throughout the day if late, or a plane going on to become a major international flight.

Quoting TWAtwaTWA (Thread starter):
Is there ever a reason to slow down the plane for scheduling or fuel economy issues?

Yes, and many airlines have been actively seeking to do this in recent years with the dramatic spike in jet fuel prices. Airlines are "optimizing" their routes and trying to use expensive technology to best plan routes so as to get the planes in on time, but not a minute too soon, so as not to waste a drop more fuel than necessary.
 
EMBQA
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:39 am

They can cut corners...No, not those kind of corners...!! Jet routes are set up like highways in the sky. Sometimes they can ask for a more direct routing to shave a little time off. Also, if the winds are good you can get an extra little push.
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c680
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 9:42 am

There are lots of ways to "make up" time in the air. The easiest is to ask for direct routing. Other ways include asking for a runway that is closer to the ramp, asking for a long or short roll out to get you closer to where you need to be, or crusing higher or lower to take advanage of better winds.

Most of the time, we ask fo these things as a regular course of business, but they do save time over predictied block times.

If we are really late, we can get a little more agressive or creative with requests. (All done politely, of course!)
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fly727
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 10:04 am

As EMBQA and C680 said, direct routes, shorter taxi distances, even pushing the power a bit can help you make a slightly faster operation.

We have one captain who likes to race our slow and fat 737s. He's one of a kind and one of the last old-school pilots we have (thank goodness). On the short legs with him, usually the block times look about 5 minutes short of usual. Not bad. On longer routes, we have arrived up to 50 minutes before schedule!

Funny thing is that once he gave me a lift from the terminal to our parking lot and he drives S-L-O-W!

RM  Smile
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flylondon
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RE: How To "Make Up Time" In The Air

Sun Jun 25, 2006 10:08 am

Take a look at morning flights from AMS-LHR. A flight that actually takes about 30 minutes is sometimes scheduled for as much as 1.5 hours.

Airlines build extra time into flight schedules from congested hubs to improve on-time performance, and so when the plane "arrives early" the passengers are pleased.

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