KC-46 Milestone C may be delayed as new problem found

A fairly significant issue has been found during fuel transfer testing with the KC-46. Boeing doesn't seem to think that it will take long to fix, but it will require a redesign of the boom. During transfer testing with the C-17, the test team measured higher than expected axial stresses on the boom, and were unable to transfer fuel to the receiver aircraft.

They have successfully transferred fuel to an F-18, AV-8B, F-16, as well as taking on fuel from a KC-10. Both Boeing and the Pentagon expect the first 18 aircraft to be delivered on time, although the Contract Management Agency has previously said they will miss that date by seven months.

A problem that has prevented Boeing Co.'s KC-46A tanker aircraft from transferring fuel to a C-17 transport plane may delay a Pentagon decision approving low-rate production of the new tanker in May, the U.S. Air Force said on Thursday.

"We don't yet know the schedule impact to the planned May Milestone C decision, but the problem is well understood and we don't expect an extended delay," said Air Force spokesman Daryl Mayer.

Mayer said the issue arose during testing of the refueling boom that is used to transfer fuel from the 767-based tanker aircraft to a C-17 transport plane, also built by Boeing.

The issue marks another setback for the Boeing program, which has run into delays due to wiring issues and other problems. However the program's projected cost dropped by $3.5 billion to $48.2 billion in a Pentagon report to Congress.

www.stltoday.com...

a reply to: Zaphod58

Didn't you post last month about a milestone delay ? Or is this a different bird to the one you posted ?

If it's the same seems like Boeing aren't having much luck with this one

a reply to: Discotech

The previous Milestone C delay was due to Pentagon availability. The people required to make the decision were booked through April with other commitments, so the decision was going to be delayed until May. This is a new issue that they just announced.

a reply to: Zaphod58

Sounds like it's a cursed project with all the delays then, what's the lifespan supposed to be for these ? By the sounds of it by the time it gets completed it'll be time for new replacements to be planned

I wish them the best of luck... I like the 135... but a 1950's aircraft should not be our main refueler.. we need the 46 up and running asap.

a reply to: Discotech

They'll be in service a long time. If the KC-135 is any indication they'll be around 70 or 80 years.

a reply to: Irishhaf

It looked like things were going really well there for a few months. They weren't running into any issues with previous transfers. I'm assuming it's something to do with the bow wave from a heavy that's causing it.

The cynic in me says despite the decades of data that they have some mutton head decided to try and reinvent the wheel on something they considered inconsequential...

But your probably right... good thing they found out with the 17, rather than a Fred.

a reply to: Irishhaf

More than likely that's exactly what it is. They wanted to come up with the newest, latest, and greatest ultra high tech wheel, and started from scratch, instead of just updating the existing one, and now it's biting them in the ass.

And now they've slipped the full rate production decision six months, and combat testing from April 2017 to October 2017. The full rate production decision will be March 2018 now.

I really need to keep a faceplant image handy. The problem was that the axial stress was too high to allow fuel to flow, so the system didn't allow it too.

The solution? Find out why the stress was so high? Make procedural changes to try to reduce the stress?

No. Rewrite the software. According to an interview with the AF, one likely fix is altering the control laws or parameters.

Because what could possibly go wrong with that idea.

Milestone C has been slipped to June. Boeing is working a hardware and software fix. They're going to attempt the software fix first, with the hardware fix on standby. They're expecting to try the C-17 and A-10 late this month.

a reply to: Zaphod58


Well if the engineers say it will be strong enough for the parameters to be safely altered than here's to hoping it works. It's a shame there are only really 3 suppliers of American aircraft nowadays. They are suffering from a chronic lack of industrial diversity.

Hi,newly joined,but read mant of your threads Zaphod.I was a crew chief on KC10s in the late 80`s and haven`t seen a comparison between their capabilities and the KC46 with a bang for the buck added in.Are they going to be more capable or less expensive than building more 10`s?And on another subject,had a long drunken talk with a Lockheed worker long ago and heard some details about a certain spy plane thats supposed to start testing soon,hah!Not going to say much,but all he said has been confirmed,they may have done away with the crew with the acknowledged version.
any way Really enjoy your threads,Would liquid methane cause a green flame?And would the KC46 have fuel cells that can handle it?

The boom has been fitted with a relief valve and has successfully refueled a C-17 and F-16.