Flying slow to save fuel?

[PCL_128]

Now what do you suppose would happen when Citrus or Southwest or anyone else came burning up my ass on the airway? Wait for it, wait for it..... Oh yeah, the center controller would speed me up or vector me off the airway depending on what he needed. Seems like it's my job to fly the aircraft efficiently, and his job to manage traffic. Works good lasts long time.

Sometimes he'll do that, or sometimes he'll just slow down the people behind you, which seems to be the more common solution from most controllers. If you're flying on busy airways with people behind you, then you need to be flying your flight planned speed.

 

[time builder]

I can't speak for every operator out there, but engine mx can affect slowing down. Power by the hour means go fast and save on engine mx cost, but burns more fuel. Obviously, the opposite is true. Since I have no idea of what mx costs are for engines on a per hour basis, I wonder what scenario is better, and by how much.

There can be MX savings in going slow. We use a reduced power setting on our turboprops to not only save gas, but it also saves on compressor washes and hot section inspections. Not to mention turboprop engines going over 20,000 hours without a major overhaul, the effects of running at a lower temperature can be more important than the time accumulated on the engines.

I know my company is considering reducing power settings even more. My personal opinion is that if you can catch a tailwind, pull the power back and milk it (particularly if you're running ahead of schedule and you know your ground crew won't be ready for you anyway), if you're encountering a strong headwind, you're only prolonging the time spent battling the headwind and not saving much fuel, heck, that's 9th grade algebra.

Another thing I don't get, why do some people insist on taking a delay vector over a speed reduction. I can just see my coworkers scratching their heads when I request a speed reduction after getting a delay vector (as if I'm just asking for punishment), but then they almost immediately vector me back on course and I arrive at the same place at the same time having burned less fuel.

That, and if something opens up (the C208 ahead switches routing, or one of your other freight dog friends cancel IFR, for instance), you have less distance to cover being on your original course, and you might get there sooner.

 

[BoilerUP]

Flex thrust climb to 10,000 also keeps engine temps lower, and therefore hot section inspections cheaper and engine time on pylon longer. I think it also saves a bit of fuel, though that isn't the primary motivator...

 

[SBD]

To the CMR folks, I don't know if anyone knows the JFK FO who did his own independent study of PPAS v.s. flying at .77. It turns out that flying at .77 actually saves more fuel than flying the PPAS profile. I only heard it second hand so it is probably not true, just wondering if anyone has heard about it.

 

[5ontheglide]

yup just like everyone else said, more money in your pocket, saves the company money, and you dont have to sit on the ground for 20minutes waiting for a gate to open. but agreed if you are holding someone else up pick it up and get out of the way

I'll take a vector to let whoever is in hurry get by us. My goal is six minutes extra per leg. For me it averages out to $40-50 extra on a 4day trip. I can cover my food bills on that! Yes I eat cheap and pack snacks. Out early and arrive on time baby!

 

[SKYWRJGUY]

2 cents:

I use the VNAV page to see if slowing actually saves any fuel on the proposed profile. Many times I have noticed the increases inflight times nearly offset lowered fuel flows, so it's a push--lower fuel flow doesn't equate to less overall burn. On longer legs, I've actually played around and had higher burn at lower speeds--too slow and you get on the back side of the power curve. At 250kts the -700 burns ~3000lb/hr at any altitude, and when we slow to a clean holding speed (i.e. 210 or so), the fuel burn comes back up to around that number.

If you're that early, land and then shut down an engine [both if on the power-by-the-hour program] and leave the APU off (-700); at 450-500pph, that 15 minutes early on the ground translates into 100+lbs .

 

[PCL_128]

Flex thrust climb to 10,000 also keeps engine temps lower, and therefore hot section inspections cheaper and engine time on pylon longer. I think it also saves a bit of fuel, though that isn't the primary motivator...

It actually burns a tiny bit more fuel (extra time spent at lower altitude), but the engine mx savings under most mx programs more than makes up for the extra fuel burn. We use de-rated climb power on almost every flight. Saves a ton of money on mx. I wasn't aware that any RJ operators had a FLEX climb program going, but GE did put out some documentation on it.

 

[BoilerUP]

AWAC went to it about 8-10 months ago in their never ending quest for lower engine MRO expense. It supposedly has helped put our engines' reliability even further at the top of the list of CF34 operators (along with restricting use of TRs, no single engine taxi, etc).

Guess they were following AirTran's lead...we both get yelled at departing PHL for flex climbing! :laugh:

 

[PCL_128]

Guess they were following AirTran's lead...we both get yelled at departing PHL for flex climbing! :laugh:

I solve that problem by avoiding PHL as best I can. Guess you can't do that, though.

 

[SSDD]

Skywest has been doing FLEX takeoffs for about 7-8 years.