On a 700 mile trip the Total Savings/Loss should be: 700 x $0.04 = $28.
Drive slower and save $28 and get home 1.7hrs later.
Drive faster and lose $28, but get home 1.7hrs earlier.

As you can tell I don’t get good gas mileage unless I’m on the highway =P

Once you are in the highest gear, standard or automatic, then it is the wind resistance which most effects mileage.

Does RPM effect the calculations? The higher the revolutions the faster the gas is burned for ignition. So 55 MPH at 6,000 RPM’s has to burn faster than 55 MPH at 2,000 RPM right? Same speed, same horsepower.

Let me know what you think.

I flew the CH-47D for a while in the Army. The CH-46 can losely be said to be a smaller version of the -47. Them there are some hydraulics and aerodynamics that are tough. But if you are a testosterone type of person the CH-47 or H-53 are the way to go.

I hear the H-65 is a sweet machine but underpowered.

Both formulas are deal with mass flow rate, in your case rho factors much more importantly than in mine because your altitude changes. In my formula the V is cubed because we are talking about power, which is defined as energy use over time, which is another formula.

My guess is that they speed up the tail rotor with respects to the main rotor to give the aircraft more directional stability. Just a guess though, as I know very little about helicopters.

Most of my helicopter time was in CH-46′s and a few HH-65′s. I did manage to fly on one CH-53E and was somewhat taken aback by the hydraulic fluid running down the inside of the aircraft. The young Marine crew chief must have seen the look on my face, so he shouted in my ear something about “thats how we know it still has hydraulic fluid.” Comforting.

Thanks for the vote of confidence but Paul is W A Y smarter than I. I could never compete with him on this stuff.

Paul,

Looking at your power equation, it is kind of close to the Lift or Drag Equation

L=Lift
ρ (pronounced «rho») is the air density (1.21kg/m3)
Cl = coefficient of lift (This is a product of airfoil shape and angle of attack)
V is the velocity in meters per second

L = ½ρ Cl V^2

This is important to me because the helicopter I fly the tail rotor speed is very critical. Its speed is 7.1 times the main rotor speed. If you droop the main rotor speed you droop the tail rotor speed by a factor of 7 squared, thereby severely reducing its lift capabilities. This results is the aircraft spinning in the opposite direction of the main rotor. Y I K E S!

Just for you Paul I know you like this math stuff. And I would have never figure this stuff out unless I was taught over and over again and tested on it every single year of my flying career. (I just took my checkrides so it is fresh in my mind).

Fred

I’ll give it a shot and see. Right now at 70mph on a trip to Albany and back home I get 31mpg in the summer and 34 during the winter (A/C does make a difference versus heat with Windows always open in both scenarios).

I’ll try just one trip (I HATE driving slowly, if I could still afford tickets I would do more than 5mph over the speed limit) to go 65mph the whole way and average out my mpg’s.

I too use my breaks as little as possible, I down shift and let the car roll, but at the same time I do take off at a light like a jack rabbit leaving everyone behind….

Excellent post and comments so far. Really relevant to current times.

Joe, what Fred said. I’ll go one further, saving $0.04 per mile adds up to $480-600 per year (12-15K miles driven). That is not bad just for slowing down a little bit, just a little bit Joe.

Jen, You are also right, driving habits, such as jack rabbit starts and excessive braking can reduce mileage. Good point.

BTW, I hate using brakes. I do it as little as possible, but it drives my wife crazy sitting over there in the passenger seat stomping on the floor with her left foot and all.