30 minutes early into HNL. Which begs the question: how much credit do pilots deserve for being early? Or late?
Well, I’m here to explain as simply as I can. I even got into a race w/ Alaska to illustrate…I’ll tell you about it in tweet 2.
First thing to know is the best way for me to get us there early is to have all passengers & bags loaded early. I have very little control over that, but if we have all the passengers & bags, I can push back from the gate up to 10 minutes early. If I get permission from ops, even earlier.
The second best shot at making up time is from our “out” time (pushing back from the gate) to our “off” time (wheels leave the ground). The flight plan accounts for a historical taxi average & the jets “elapsed time” doesn’t start until the wheels lift off. If lucky & there isn’t much ground traffic, I can beat the historical average taxi.
If very lucky, I can both push back early & beat the taxi average. That’s where I start eyeing an arrival 10-20 minutes earlier than the flight plan.
Tonight, we pushed “out” 10 early, but only got off 5 minutes before our “off” time. So, my taxi actually took longer than average (out of my control), but the early push still gave us a 5 minute head start on the flight plan.
At this point, you should know the flight plan already had us landing 22 minutes early. So the pushback saving us the 5 min head start now put us at 27 minutes early into HNL.
This is where you might be disappointed to learn that there usually isn’t a whole lot else I can do beyond that. Yes, I picked up 3 more minutes tonight…over a 4 hour, 55 minute flight.
The biggest factor once in the air is almost always winds aloft. When you book your ticket, the flight time is based on a historical average plus a pad. If the winds are wildly off that average, your flight time will be different. Could be good, could be bad. Tonight, we had almost no headwind going West & even had a tailwind at some points…which is not normal & is why the basic flight plan at the most efficient speed had us arriving 22 minutes early before I did anything.
Now, winds can be very different depending on your altitude. You can climb or descend a few thousand feet to improve your situation, as long as ATC will allow it. As w/ all things aviation, though, there’s a catch.
It’s fuel. Airlines have to be very efficient w/ fuel. Anytime the jet is heavier, it takes more fuel to fly. So, loading extra fuel beyond what you need adds weight & now you’re burning more fuel than needed to just to carry extra fuel you don’t need. Expensive!
Winds aside, going higher is more efficient, up to an optimum, then burns more fuel again. Staying lower always burns more fuel. Tonight, at Flight Level 350 (FL350, or 35,000’) I was projected to land w/ 8.0k lbs.. The computer said if I climbed to FL400, I’d land w/ 7.7k lbs, and if I flew at FL300, I’d land w/ 7.0k lbs..
That’s plenty of fuel, but I’m trying to save the airline money. If I burned an extra 300 lbs, it’s about $194 extra. Now imagine every pilot did that on the 4k flights daily…that’s $776k a day, or $283M a year.
So, there’s a balance to be found here on winds & altitude.
Altitude also plays a role in speed. Speed is going to be the hardest thing to explain, but I’ll try not to make it mystifying:
At higher altitudes, we measure speed in terms of “Mach”, or a percent of the speed of sound. So, .75 Mach is 75% of the speed of sound. Got it?
Here’s the next catch: the speed of sound changes w/ altitude & air density. At Sea Level, it’s 720 mph. At FL350, it’s 678 mph, and at FL400 it’s 659 mph. Just remember it’s slower the higher you go.
I asked the computer how we’d do if I bumped up the speed:
At our current .78M, we land 18 minutes after the hour w/ 8.0k lbs of fuel.
At .80M, land 4 min earlier (forgot to write down fuel).
At .81M, land 6 min earlier w/7.4k fuel.
So, bumping speed is a trade for fuel. Sometimes, you don’t have it to spare.
Now, the race…
1/2