How is range increased when flying into a headwind?
Joined: Feb 2006
Posts: 157
Likes: 0
From: FL430
Simple
Guys, this is a very simple question and if you follow this principle it works for all machines from Gliders to 747's.
follow the stops below
1. draw your typical drag curve graph
2. draw a tangent to that drag curve that starts at the origin (ie where the x and y axis cross)
That's your STILL AIR best range speed.
now...
3. move the tangent line "forward" by 20 knots (ie. to the right of the x axis) to represent a 20 knot headwind. Notice how the best range speed now touches the drag curve at a higher speed, therefore best range speed is a little higher.
4. Now do the reverse to represent a tailwind. Notice how the best range speed is less.
Simple rule of thumb... fly a little faster to get out of the headwind quicker, it aint helping you!
Fly a tiny bit slower to stay in the tailwind longer, it is helping you!
In theory this is practical and from my days on the straight winged props it did make a measurable difference.
In a swept wing jet where the drag curve is very shallow anyway and the fuel consumption is marginally different.... in my experience/opinion, the difference is very hard to measure unless you are on a 7 or 8 hour flight, but even then so many other factors come into play.
I like this question because it does have some practical application, even if it is limited, but it really tests you knowledge of the drag curve.
Remember though, if you are flying significantly above your best range speed, ie high speed, all this doesn't matter as you might be getting close to your Mmo and as such compressibility comes into play and the theory is shot. This is a max range theory question.
follow the stops below
1. draw your typical drag curve graph
2. draw a tangent to that drag curve that starts at the origin (ie where the x and y axis cross)
That's your STILL AIR best range speed.
now...
3. move the tangent line "forward" by 20 knots (ie. to the right of the x axis) to represent a 20 knot headwind. Notice how the best range speed now touches the drag curve at a higher speed, therefore best range speed is a little higher.
4. Now do the reverse to represent a tailwind. Notice how the best range speed is less.
Simple rule of thumb... fly a little faster to get out of the headwind quicker, it aint helping you!
Fly a tiny bit slower to stay in the tailwind longer, it is helping you!
In theory this is practical and from my days on the straight winged props it did make a measurable difference.
In a swept wing jet where the drag curve is very shallow anyway and the fuel consumption is marginally different.... in my experience/opinion, the difference is very hard to measure unless you are on a 7 or 8 hour flight, but even then so many other factors come into play.
I like this question because it does have some practical application, even if it is limited, but it really tests you knowledge of the drag curve.
Remember though, if you are flying significantly above your best range speed, ie high speed, all this doesn't matter as you might be getting close to your Mmo and as such compressibility comes into play and the theory is shot. This is a max range theory question.
Joined: Aug 2007
Posts: 184
Likes: 0
From: London, UK
Lightning Mate wrote:
I think you mean 'by the way'. What was the point you were making about JAA not being able to construct questions in clear English? U r a level 1 spooker write? Have you thought about speaking to a professional? 
Borderdash.........
Ex-JAA exam question consultant. Bye................
Bye the way,
If you are contemplating a professional licence, then I suggest you speak to professionals.
Bye again.
Ex-JAA exam question consultant. Bye................
Bye the way,
If you are contemplating a professional licence, then I suggest you speak to professionals.
Bye again.
