Winglets and a missed opportunity for the USAF

[NutLoose]

Much of the drive that led to a KC-135 flying with winglets — as early as 1979, long before they became commonplace — was the energy crisis of that same decade. The effects of the Yom Kippur War caused interruptions in exports of Middle Eastern oil and Western countries began to feel the pinch, with another worsening of the situation in 1979, triggered by the Iranian Revolution and the events that followed (https://www.thedrive.com/the-war-zone/38664/what-if-the-iran-hostage-rescue-attempt-hadnt-ended-in-disaster-at-desert-one). As the crisis drove up fuel prices, the effects were felt keenly by the gas-thirsty Air Force.

Between July 1979 and January 1981, the winglet-equipped 55-3129 completed 39 flights and over 170 flying hours in this configuration, demonstrating a 6.5 percent fuel saving throughout the aircraft’s usual flight regime, equivalent to nearly 45 million gallons per year across the entire fleet. At the same time, the reconfigured aircraft also demonstrated improved takeoff performance and fuel offload capability.

Except they decided against it, partly due to not expecting the fleet to soldier on so long, so 40 years later and a saving of 45 million gallons per year across the fleet works out at a mind blowing 1.800 million gallons of fuel bought and burnt that need not have happened assuming other factors did not come into play..

https://usanewswall.com/news/automobile/the-air-force-blew-it-when-it-decided-not-to-give-its-kc-135s-winglets-40-years-ago/

[Mr N Nimrod]

Except they decided against it, partly due to not expecting the fleet to soldier on so long, so 40 years later and a saving of 45 million gallons per year across the fleet works out at a mind blowing 1.800 million gallons per year of fuel bought and burnt that need not have happened assuming other factors did not come into play..

https://usanewswall.com/news/automobile/the-air-force-blew-it-when-it-decided-not-to-give-its-kc-135s-winglets-40-years-ago/
Only it wouldn’t be 1800 million gallons per year would it brainbox!

[garyscott]

Only it wouldn’t be 1800 million gallons per year would it brainbox!

Nope, it would be 1 POINT 8 million gals as stated. Not 1800 million.

[NutLoose]

Only it wouldn’t be 1800 million gallons per year would it brainbox!

lol I copied the 45 mil line across changed the total and forgot to remove the per year.

[megan]

To install winglets the wings would have to be beefed up, considerable work required. What Boeing has to say.

https://www.boeing.com/commercial/aeromagazine/aero_17/winglet_story.html

[tdracer]

To install winglets the wings would have to be beefed up, considerable work required. What Boeing has to say.

https://www.boeing.com/commercial/aeromagazine/aero_17/winglet_story.html

Given the KC-135 and 767 are similar sized/weight aircraft, the retrofit costs should be similar as well, so lets look at adding winglets to a 767.
Round numbers, adding winglets to a 767 is around $2 million per aircraft. Now, when you're flying 3,000 to 4,000 hours per year, you can pay that back in (again, round numbers) about 18 months.
USAF tankers don't get to anywhere near those numbers - according to the numbers we were given during the KC-46 program, figure more like 200-300 hours per year. Payback is now more like 20 years, without taking into account the costs of money. Also, the photo with the OP's linked article shows a JT3C (J57) powered aircraft - which has much higher fuel burn numbers than the CFM re-engined aircraft, so fuel savings after the engine upgrade would be much less.
Not exactly a no-brainer...

[NutLoose]

Kc135 was re-engined starting 25 years ago and saved a 25 fuel burn, but the winglets would have still continued reducing the burn and costs then would have been less to fit.
https://www.boeing.com/news/frontiers/archive/2005/july/qt_ab1.htmlSo

That would still leave 15 years at a 45 mil gal per year saving. Fuel is still an ultimate finite resource, tin can be recycled.

https://www.boeing.com/news/frontiers/archive/2005/july/qt_ab1.html

[tdracer]

Kc135 was re-engined starting 25 years ago and saved a 25 fuel burn, but the winglets would have still continued reducing the burn and costs then would have been less to fit.
https://www.boeing.com/news/frontiers/archive/2005/july/qt_ab1.htmlSo

That would still leave 15 years at a 45 mil gal per year saving. Fuel is still an ultimate finite resource, tin can be recycled.

https://www.boeing.com/news/frontiers/archive/2005/july/qt_ab1.html
Do you remember 1979? I bought my first house in 1979 - the mortgage was 11% :eek:. It went up from there, peaking around 15% five years later. The fuel savings wouldn't have even paid the interest on the cost of the winglets retrofit until interest rates started dropping years later...

[BEagle]

We were given a briefing about winglets and the cost/benefit at an ARSAG conference a few years ago.

After loads of data and graphs, the presenter concluded that there would be no significant overall cost saving.

But that was when the KC-46A was expected to replace the KC-135R rather quicker than has proved to be the case....