Can someone explain this to me?

[ADRidge]

So I'm trying to plan a cross-country to an airport about 40nm away at 125. Winds are 170 and blowing fairly heavy, which axed the flight. My CFI told me that because of the headwinds, we'd burn more than the standard 8gph for the R-22 Beta we'd be taking that day. I don't really understand why a headwind would change our fuel burn rate, because isn't airspeed the same regardless of wind condition?

 

I understand the relationship between airspeed and ground speed and all that, I'm just baffled that 80kts Calibrated AS with a tailwind would burn less fuel than 80kts Calibrated with a headwind. Is there something I'm missing here?

[RotorWeed]

So I'm trying to plan a cross-country to an airport about 40nm away at 125. Winds are 170 and blowing fairly heavy, which axed the flight. My CFI told me that because of the headwinds, we'd burn more than the standard 8gph for the R-22 Beta we'd be taking that day. I don't really understand why a headwind would change our fuel burn rate, because isn't airspeed the same regardless of wind condition?

 

I understand the relationship between airspeed and ground speed and all that, I'm just baffled that 80kts Calibrated AS with a tailwind would burn less fuel than 80kts Calibrated with a headwind. Is there something I'm missing here?

 

If you have a head wind it's going to take you longer to get to your destination; hence you burn more fuel then if you didn't have a head wind. The CFI probably wants to make the trip and not have to refuel at the destination. I'm not sure what the Beta burns but I always flight plan the Beta 2 at 10 gallons per hour.

 

RW

[DanceswithCyclic]

I agree with RW.

I use 9 gph in R22 BII. Ground speed is key, not CAS. A 20 kt headwind over 40 Nm will take an additional 10 minutes at 80 kts CAS. The headwind direction will take an additional 1.5 gal. and there is no guarantee under the blue sky you can 'make up' the extra burn with a tailwind. Remember your VFR Fuel Reserves?

[PhotoFlyer]

I think you might have misunderstood your CFI, or he/she may not understand. He/she didn't mean that the fuel burn rate would increase, but that the total fuel burned for that leg would increase. Manifold pressure dictates fuel burn. Higher airspeeds require higher MP, but 80 knots with a tailwind will require the same MP as a headwind.

 

I would ask your CFI to clarify the next time you see him/her.

[Mikemv]

To all, fuel burn would be the same no matter what the wind speed or direction. A strong headwind leg will definetly require more fuel than a no wind leg. Also, it will not average out on the return with the same winds because the headwind leg acts on you for a longer period. Plan a 100 mile leg with no wind and return and note fuel burn. Then plan the same route with 20kts on the nose and tail respectively and see the difference in fuel used compared to the no wind trip. Fly safe, Mike

[ADRidge]

No I'm clear on the fact that it'll take more fuel with a headwind, but I think maybe I'm just misunderstanding my CFI. I don't know if he was trying to talk about headwind issues or something else. I'll ask him tomorrow.

[Scarab]

just curious how much the two of you weigh. It's only 40 miles each way. How much fuel can you carry and still be in w/b?

[Witch]

ADRidge,

 

The only thing that'll change the burn rate is the weight. Heavy bird=increased engine workload=greater fuel consumption. Lighter bird=decreased engine workload=less fuel consumption. Just like your car?

 

Wind has no effect on fuel burn rate.

 

Other than that, happy flying.

 

Later