Switching to NEO engines saves 15%, or in your example 4500#. Even saving 1% in an industry that regularly has 2% margins can make a difference.

SeaTac airport makes a big deal of having pre-conditioned air and ground power available at every gate so there is no need to run the APU at the gate until you're ready to start engines.

When your flight is fully booked never accept anybody on jumpseat to keep a/c weight low :ugh:

Learn your three times table

Be careful comparing directs to original route, as (unless winds are known along/abeam waypoints on direct clearance) the time increment cannot be relied upon.
This is the reason why, when all actual winds are used at waypoints, the ABEAM functions in FMC on NG exists, so not to loose valuable data in case of direct clearance...

An operator entering AVG WIND at first waypoint after TOC does so for preflight planning and estimate of time and fuel on arrival in comparison to flight plan, not for inflight use.
Same operator requiring TOC WIND to be entered (wind after ~20 minutes would be good) does so for optimising fuel burn up to TOC, not for estimate time and fuel on arrival.
Therefore not applying both above upsets the preflight prediction on longer flights with multiple wind changes, giving inaccurate data for crew to work with, showing incorrect times and fuel prior to flight.

If FMC is left unchanged and no actual winds for each waypoint are entered (which could be done when time permitting preflight or in cruise flight), when executing a direct clearance, last known wind (AVG or TOC in prior example) is used to predict from next waypoint and onward estimates, however actual wind at time of execution is used for prediction to next waypoint.

When getting cleared for a direct clearance of an hour, where FMC entered TWC at TOC was ~100kts, but wind at execution of direct is HWC ~100kts a ~40% groundspeed differential is observed in estimate for next waypoint, this equates to ~25 minutes.


On similar narrow body you can save up to 50-70kg if you land using idle reverse thrust which can sometimes only be achieved by wasting those 15kgs saved through use of lower flaps. (Slow it down +15kgs, ability for landing with idle reverse -70kgs, saving 55kgs!)

Superpilot nailed it.

I suspect I know what tree he’s barking up.

If you are 30 miles to run, flap 2, 180 knots 3000’ with the chicken stick out then you are wasting more fuel than the savings just listed above save.

Seen it too many times in my career, so many pilots totally clueless about altitude versus track miles.

Agree. also a good one is if you've gone for high speed but get an intermediate level off FFS SLOW DOWN. Keeping the higher speed at low or mid altitudes haemorages fuel like nothing else. Not that ATC gives a hoot....

Any one knows what the difference in full consumption is if you modify the descent speed from CI (around 270kias) to say 300 on a medium size aircraft? You'll keep cruise power a few minutes longer but your descent will be shorter, taking advantage of the higher GS/TAS.

I've done this to save a couple of minutes when going behind schedule but don't know how does it affect fuel economy (haven't done the fuel gauges vs computer flight plan math to be honest).

Work out the fuel flow for your aircraft type in cruise (~2200/2500 kg/hour for 737);
Work out time spent extra in cruise (check against calculated TOD to get minutes extra) then based on above work out additional cruise fuel requirement;
Work out the fuel flow for your aircraft type in descent (~500 kr/hour for 737);
Work out time spent less in descent (use RTA for runway prior and after KIAS increase (earlier arrival therefore time gained, then reduce it by additional time spent in cruise), this gives descent saving;
You WILL find out that a minute extra in fuel in cruise (~40 kg) can only be regained by reducing descent time by >6 minutes which means this was it is to generate a fuel saving.
Starting an idle descent as soon as possible at best glide speed (lowest CI) is most fuel efficient.

Thanks Skyjob, that's quite helpful. Should be interesting to run the math even if you already gave out the answer haha

@ehwhatezedoing

Forget a runway overrun. That's taking it to the extreme. Depending on runway length, current conditions and aircraft weight, you would need to reduce flex to a lower degree to meet perform requirements plus the increase in fuel associated with the increase in power. Unless really light on weight (i.e. no reduction in flex for takeoff) I don't think it would save too much.

P.S. We aren't allowed to do intersection takeoffs at our gig

Isn't higher climb power better for fuel consumption?

I would assume the same applies to takeoff power no?

I thought this thread was about saving fuel cost ;)
Just put a spare engine in the cargo compartment.

Several years ago, we were investigating a particular Asian airline that had horrible time-on-wing for their 737/CFM56 engines. Mainly sort haul, they were running out of EGT margin in ~3,000 hours - at a time when the typical operator was in the range of 15,000-20,000 hour time on wing.
Come to find out, they were using max TO every single takeoff - never a derate of any kind. At around a million dollars to overhaul an engine, you'd have to save a whole lot of of fuel to justify an extra two million dollars/year in engine maintenance...