Forum: F-16 News

Typical media misunderstandings in the Time article - fan blades and engines don't "explode" and turbine blades are not the same as fan blades.

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maus92 wrote:

For all those who consider the risk of a single engine failure low, they still do happen with some regularity. This one did not allow the aircraft to recover to a nearby airfield

For all those who consider twin engine aircraft safer than singles, think about 'quality of maintenance' or the mentality of the people working the aircraft.

Explain how the F100-PW-229 is 'safer' statistically in the Viper than in the Eagle?

(TEG's responce - we pay attention more than our 'spare engine thinking' counterparts!)

Ref USAF Safety Center data: http://www.afsec.af.mil/organizations/a ... /index.asp

Remember, it's typically NOT the engine causing the mishap; it's a human who is starting the chain of events that causes the engine to lead to the mishap.

Missing something ,not paying attention, not caring, doing it wrong, wrong parts, wrong materials chosen, etc.

Keep 'em flyin' Thumb

(safely!)
TEG

neurotech wrote:

ruderamronbo wrote:

Gamera wrote:

http://www.startribune.com/nation/168790886.html?refer=y

Air Force: Engine failure caused F-16C Falcon to crash in Utah training range; pilot ejected

Updated: September 6, 2012 - 1:35 PM

NORFOLK, Va. - A fighter plane crashed during a training mission in Utah this May because of an engine failure that possibly could have been avoided if inspectors had noticed an anomaly in a fan blade when it was installed in 2004, according to an Air Force report released Thursday.

Could/should this anomaly have been detected during 8 subsequent years of post flight and periodic maintenance inspections? Not throwing stones just curious about what can be seen looking down the intake.

Also, is 8 years of installation normal for an Viper motor?

They are saying the fan blade was installed 8 years ago. I'm pretty sure the engine didn't stay in the jet that long. It would have been borescoped multiple times for inspections. I don't think they CT Scan complete engines routinely, although I've seen it done with a bizjet engine by a university. Even a 2D X-Ray of a fan disk might help, but again it would be very expensive to do outside depot overhaul interval.

This has to be balanced with the cost of replacing a $30-$60m F-16 after the pilot ejects out. There have been cases of F-16s doing a successful engine-out landing.

It's not that the engine wasn't removed, or the fan hadn't been changed.

What WAS a factor here; the blades had not been removed from the hub and inspected in a 'disassembled' state.

If the defect was inside the root of the blade, the inspections you mention here have a very VERY remote chance of detecting it.

Looking at blades through a borescope (or the inlet for 1st stage) only gives you the portion of the blade 'above the platform'. Which we'll guess at 80-90% of the blade's mass? That's IF it wasn't a 2nd or 3rd stage blade that is ONLY visible through a scope.

Even if you looked at the blades in the hub (disk) if the defect weren't along the forward/aft edge of the root, it would not be visible.

So YES, fan blades can stay installed in their respective 'hubs' for 8 years between depot overhauls. If there is no FOD/DOD to them (or an associated component that required their removal for access) over that time frame there would be no reason to remove them from the Fan and/or Engine.

I've seen defective parts make it through a decade of service. When the modules/parts are returned to depot for overhaul someone says LOOK LOOK what I found, you're doing it wrong!!!! only to realize that we in the field have NEVER accessed that area since the last time it was 'built up' by them.

USAF depots and contractors get to operate by a completely different set of rules than the Jet Engine Intermediate Maintenance (JEIM) and Flight Line Units. Often these differences in practice/theory lead to situations like this.

Seen it before (many times) and will see it again. The term used in the industry is "quality escape" (IE - someone f-ed it up and you need to inspect them before you use them or return them to us ASAP)

Remember F110 powered Viper that crashed due to the oil passages being plugged in the gearbox during 'overhaul'? Many MANY F110 gearbox needed to be removed and reinspected over that one. It wasn't that the F-16 unit's engine folks weren't inspecting the engines or gearboxes properly, it was that the defect lay internal where we in the field either don't or aren't allowed to go.

You only hope that you can 'find' the error prior to it becoming an accident or worse a fatality.

Below you can see how much of a 'blade' is hidden in the disk/hub. If an inclusion, void, crack, etc is located in the 'root' of a blade and not noticed during assembly, it would continue to fly unless other damage in the compressor required the blades' removal.

Keep 'em flyin' Thumb

TEG

exfltsafety wrote:

Typical media misunderstandings in the Time article - fan blades and engines don't "explode" and turbine blades are not the same as fan blades.

Two on that! (Media Slap

)

What blades do is 'release' under tremendous forces.

REF: Blade out test on youtube http://www.youtube.com/watch?v=wcALjMJbAvU

Keep in mind military fighter engines aren't designed to contain themselves when they come apart. Weighs too much and there isn't anyone sitting next to them in the body of the aircraft.

Here is an F100 engine that failed due to the disk lugs allowing blades to 'liberate' during high RPM.

http://www.youtube.com/watch?v=5F-I08xLWqM

If you watch the video closely, you can see the fan inlet case bouncing around on the N1 hub before it drops to the floor. The oil tank was destroyed during the 'liberation' causing the fire that ensues. (Note sparks on concrete floor from blade ricochet)

Keep 'em flyin' (Safely) Thumb

TEG

PS - triple post tonight? guess I'm not visiting often enough?

exfltsafety wrote:

Typical media misunderstandings in the Time article - fan blades and engines don't "explode" and turbine blades are not the same as fan blades.

Was thinking the same thing.

Thanks for all the detailed answers--I figured you might be the one with the real scoop Very Happy

Quote:

F-16 Crash Report Updated

Air Combat Command investigators released an addendum to the report on the <a href="http://www.f-16.net/news_article4564.html">May 2012 crash of an F-16C from Hill AFB</a>, Utah, at the Utah Test and Training Range. In its report issued last September, ACC's accident investigation board determined that a manufacturing flaw in a blade in the first stage fan of the aircraft's engine caused the crash and loss of the fighter during ground support training. The AIB president reopened the investigation to re-examine whether maintenance crews should have identified the manufacturing inconsistency at the base of the blade, according to ACC's Feb. 7 release. The report addendum indicates that the blade's surface inconsistency could have been detected during installation at Tinker AFB, Okla., in April 2004, states the release. However, the ability to detect the defect was limited due to the lubrication applied during machining work and the transfer of the part, it states. Procedures also did not require an inspection, and were not typically completed at Tinker for new blades arriving from the manufacturer, noted ACC. (Updated AIB report)

Source: http://www.airforce-magazine.com/DRArch ... dated.aspx

Forum: F-16 News

F-16 crashes at Utah Test and Training Range - May 4th 2012