Short Leg Fuel Efficiency Question

[atpcliff]

Hi!

Flying a small jet (falcon 20), what is most fuel efficient for a short leg: A continuous climb until u hit the descent point (parabola) or a level off at a lower altitude and cruise level for a while?

I think that the parabola thing is the most fuel efficient.

I also think it doesn't matter what kind of jet you are flying (citation/-747), or even which kind of plane you are flying (recip/turboprop/jet).

However, I realize that the different powerplants MAY have differing best-fuel burn practices AND it may matter in a jet if you have a low vs. high-bypass engine or a straight wing vs. a swept wing.

I would like to hear everyone's opinion, because I would like to fly as efficiently as possible.

cliff
DAL

 

[MauleSkinner]

I was told that 1/3 of the time in climb, 1/3 in cruise, and 1/3 in descent was most efficient for a jet. Probably a tradeoff between fuel and flight time.

Seems like for piston airplanes they recommended 1/4, 1/2, and 1/4, but I think there was some difference between the best for a turbocharged vs normally aspirated, and I can't remember that.

The rule of thumb I use for short hops in corporate jets is an altitude of 15% of the distance...IOW, for 100 miles I go to 15k.

Probably a bigger factor is not using max continuous power down low...we limit the Hawker to 1000#/side fuel flow in cruise. Specific fuel consumption really climbs fast above that.

Fly safe!

David

 

[Lead Sled]

I've wrassled with this very question quite a bit over the years and the answer always comes out the same; the basic rule of jet operation applies - you should normally climb as high as you can, as quickly as you can, stay up there as long as you can then descend as fast as you can. Running the scenario on various computer simulations and in the actual aircraft the most efficient altitude on extremely short legs was to climb until it was time to descend. That being said, ATC isn't always going to allow you to fly a "mortar shell" profile. On 731 powered jets the penalty wan't very significant.

The rule of thumb that I use is 2.5 or 3 to one - on 100 mile leg you can climb to 25,000 to 30,000 feet. It's not ideal, but it work just fine in the real world.

LS