If you look at the flight plan paperwork from this LANTAM video, it shows the flight plan... the Great Circle Distance is LONGER than the Air Distance. How could that be physically possible? Its about halfway down in the center column.

https://youtu.be/gVM8XZaZ5ok?t=34s

If you have a tailwind the air distance will be shorter.

What he said. There is the Distance and then there is the air miles flown.

If you look at the GND DIST that is 5217. So there is a slight tailwind. If you look at the far right hand column there is AVG W/C (average wind component) of T17 which is a tailwind of 17 knots averaged over the entire flight.

Woodreau wrote:

If you have a tailwind the air distance will be shorter.

I don't understand. Isn't the great circle distance the shortest possible connection (in terms of length, not time) of two points on a globe?

I understand that another, longer route can be faster but not shorter.

BartSimpson wrote:

Woodreau wrote:

If you have a tailwind the air distance will be shorter.

I don't understand. Isn't the great circle distance the shortest possible connection (in terms of length, not time) of two points on a globe?

I understand that another, longer route can be faster but not shorter.

Don't think of air distance as an actual distance.. It's more of an equivalent distance.

If the Great Circle Distance was say 5 000 nm, but you have a tailwind of 100 kts all the way, then you can think of it as a distance of only 4900 nm. You'll still fly the same track over the earth, but you will do it faster.

BartSimpson wrote:

Woodreau wrote:

If you have a tailwind the air distance will be shorter.

I don't understand. Isn't the great circle distance the shortest possible connection (in terms of length, not time) of two points on a globe?

I understand that another, longer route can be faster but not shorter.

Think about the air distance as the distance the aircraft travels through the air.
You can compare the moving airmass with a moving walkway. As an example: you walk with 5 km/h (that's the True Airspeed) and the walkway is moving with 3 km/h (that's the tailwind). After an hour you are 8 kilometres from your starting point, but still you walked only 5 kilometres on the walkway. In this comparison the 8 kilometres are the ground distance, the distance you travelled effectively from point A to B. The 5 kilometres are the Air Distance, the distance you were walking on the walkway - or back to the aircraft: the distance the aircraft travelled through the air.

SAAFNAV and Glen: Thanks for your explanations. I get it now!

SAAFNAV wrote:

If the Great Circle Distance was say 5 000 nm, but you have a tailwind of 100 kts all the way, then you can think of it as a distance of only 4900 nm.

More like 4200 nm.

timz wrote:

SAAFNAV wrote:

If the Great Circle Distance was say 5 000 nm, but you have a tailwind of 100 kts all the way, then you can think of it as a distance of only 4900 nm.

More like 4200 nm.

Indeed yes, thanks.

It is still counter-intuitive that just because there is a tailwind the distance covered will be less. Time reduction I can relate to but not the reduction of distance just because you're being pushed along a little faster. Crazy.

glen wrote:

BartSimpson wrote:

Woodreau wrote:

If you have a tailwind the air distance will be shorter.

I don't understand. Isn't the great circle distance the shortest possible connection (in terms of length, not time) of two points on a globe?

I understand that another, longer route can be faster but not shorter.

Think about the air distance as the distance the aircraft travels through the air.
You can compare the moving airmass with a moving walkway. As an example: you walk with 5 km/h (that's the True Airspeed) and the walkway is moving with 3 km/h (that's the tailwind). After an hour you are 8 kilometres from your starting point, but still you walked only 5 kilometres on the walkway. In this comparison the 8 kilometres are the ground distance, the distance you travelled effectively from point A to B. The 5 kilometres are the Air Distance, the distance you were walking on the walkway - or back to the aircraft: the distance the aircraft travelled through the air.

So you're saying the distance travelled is FURTHER with the tailwind. As I understand the OPs question, this is opposite, conflicting logic.

The distance, over the ground, is the same, but with the tailwind the plane traveled thru LESS airmass to arrive at the destination.

GF

glen wrote:

BartSimpson wrote:

Woodreau wrote:

If you have a tailwind the air distance will be shorter.

I don't understand. Isn't the great circle distance the shortest possible connection (in terms of length, not time) of two points on a globe?

I understand that another, longer route can be faster but not shorter.

Think about the air distance as the distance the aircraft travels through the air.
You can compare the moving airmass with a moving walkway. As an example: you walk with 5 km/h (that's the True Airspeed) and the walkway is moving with 3 km/h (that's the tailwind). After an hour you are 8 kilometres from your starting point, but still you walked only 5 kilometres on the walkway. In this comparison the 8 kilometres are the ground distance, the distance you travelled effectively from point A to B. The 5 kilometres are the Air Distance, the distance you were walking on the walkway - or back to the aircraft: the distance the aircraft travelled through the air.

Thanks Glen, the walkway analogy made sense of it! Im a Captain for an airline in the states, but we only go out to about 2,000 miles, so great circle distance is never on our paperwork. Only flight plan distance.

After doing about a zillion (technical term) practice questions on groundspeed vs airspeed for the ATPLs I feel like I should grasp this much more intuitively than I do.

Just to throw a bit more confusion into the mess: flying above the surface level means traveling on longer trajectory compared to the ground track due to spherical shape of the earth.
That means air distance is about 1/637 longer for 10 km (FL300) altitude, e.g. there is extra 1.5 mile of flying compared to surface distance for a 1000 mile track...

thefactorypilot wrote:

glen wrote:

Thanks Glen, the walkway analogy made sense of it! Im a Captain for an airline in the states, but we only go out to about 2,000 miles, so great circle distance is never on our paperwork. Only flight plan distance.

I'm with you. I flew long haul for many years 6000nm+ and our flight plans never had the great circle distance nor the 'air distance'; just the flight planned distance and average wind components. Maybe some airlines/crews use those numbers but I have no idea what for.

RetiredWeasel wrote:

thefactorypilot wrote:

glen wrote:

Thanks Glen, the walkway analogy made sense of it! Im a Captain for an airline in the states, but we only go out to about 2,000 miles, so great circle distance is never on our paperwork. Only flight plan distance.

I'm with you. I flew long haul for many years 6000nm+ and our flight plans never had the great circle distance nor the 'air distance'; just the flight planned distance and average wind components. Maybe some airlines/crews use those numbers but I have no idea what for.

Most of the flight plans I see, do in fact have a NAM number on them. Certainly a good indicator of the wind impact, especially on a 6000NM leg. The fact that Singapore or NWA did not, is not indicutive of the rest of the world. It;s amazing how different airlines create a flight plan. In the case of Jeppesen, there are dozens of formats for an ETOPS flight plan, sand the difference are simply eye watering from a user perspective.

BravoOne wrote:

The fact that Singapore or NWA did not, is not indicutive of the rest of the world. It;s amazing how different airlines create a flight plan.

I can tell you categorically both SQ and NW DID have NAM on the flight plans. In fact, after working with/for about a dozen international carriers, I have yet to see one which doesn't have NAM.

mmo wrote:

BravoOne wrote:

The fact that Singapore or NWA did not, is not indicutive of the rest of the world. It;s amazing how different airlines create a flight plan.

I can tell you categorically both SQ and NW DID have NAM on the flight plans. In fact, after working with/for about a dozen international carriers, I have yet to see one which doesn't have NAM.

You and I both worked for the same airlines. Here's a training flight plan, but was just like the real flight plans. First page only, but I can't find the NAM nor is it on any of the other pages. This is kind of ancient, but I swore when I was on the 400, it was the same thing.

BravoOne wrote:

Actually don't recognize that flight plan or at least don't remember it:) My most recent flying was in a corporate 767-200ER and a 757 that was tanked to give no more than 13 hours so your long range experience exceeds anything I have seen. Did many HKG/LAX legs, and don't think that was what we were using back then. I do run numerous flight plans for polar ops thede days the NAM is simply a part of the format.
FWIW (not much), the Boeing default Jeppesen flight plans do show a NAM number. They actually show both the NAM and airway miles.

That was meant for MMO and is a NW flight plan.

Actually don't recognize that flight plan or at least don't remember it:) My most recent flying was in a corporate 767-200ER and a 757 that was tanked to give no more than 13 hours so your long range experience exceeds anything I have seen. Did many HKG/LAX legs, and don't think that was what we were using back then. I do run numerous flight plans for polar ops thede days the NAM is simply a part of the format.
FWIW (not much), the Boeing default Jeppesen flight plans do show a NAM number. They actually show both the NAM and airway miles.

RetiredWeasel wrote:

That was meant for MMO and is a NW flight plan.

I do remember seeing them on the 400. All my NW "treasures" are long gone, after a move to the UK, Singapore, back to the UK...6 years commuting to AUH for Amiri (Presidental Flight), QR and a final move to Spain.....But, I do remember them on the 400 and every long haul ever since then.

I do remember that question coming up as it was a topic for new Cadets who couldn't quite get their head around things.

Good example on a 737-8MAX flight plan from SEA to HNL with a M063 overall headwind component.

GREAT CIRCLE DISTANCE 2326 NM AIR DISTANCE 2748 KSEA TO PHNL

-N0458F320 DCT BTG J136 ONP/N0455F340 C1419 HEMLO/M079F340 A332
HALLI/M079F360 A332 AUNTI/N0461F360 DCT APACK MAGGI3