Forum: F-35 Lightning II

That_Engine_Guy wrote:

Perhaps the seat-pack is red? Doh

I hope there is a titanium shield behind the cockpit, or a large piece of Kevlar somewhere between that fan and the pilot. Shrug

It would make me a little nervous sitting in that seat, I don't even like to sit next to props on commuter flights!? Shocked

As I recall, there is a titanium bulkhead between the lift fan and the cockpit. I'm thinking that was actually one of the critical design challenges for the X-35...the titanium bulkhead was necessary for safety but extremely costly and heavy.

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I'm not sure about that on the F-35. My guess is that they've probably got the safety factor covered by kevlar in the lift fan casing. Thats how they combat thrown blades (or try to at least) on big turbofans.

Elite Joined: Jul 22, 2005 Posts: 821 Status: Offline

If the blades are composite could they make them so they shred if they fail rather than have heavy fragments try to tear through the bulkhead? Question

sferrin wrote:

If the blades are composite could they make them so they shred if they fail rather than have heavy fragments try to tear through the bulkhead? Question

Are the blades made of composite? I wouldn't think so, but I don't know one way or another. I think composites tend to shatter rather than shred. But composite fragments would be better than metal ones.

LMAggie wrote:

I think composites tend to shatter rather than shred.

habu2 wrote:

LMAggie wrote:

I think composites tend to shatter rather than shred.

...or not...

Elite Joined: Dec 14, 2005 Posts: 586 Status: Offline

Mute point.... Cheers

Seems the LiftFan has hollow metal blades that are welded into the disk to create a "blisk"

Being hollow would reduce their mass in a "blade out" situation allowing easier containment, and the fact they are welded into a blisk assembly would keep them in place much more effectively. Two Cents

Quote:

Each fan has a diameter of 1,270 mm (50.0 in), and comprises a ring carrying hollow radial blades, which are described as world-leading technology. Appreciable weight was saved in a critical area by making not only the first-stage blades hollow, but also the second (these were originally solid). Each ring is forged as a disc, which after turning and milling has the hollow blades attached precisely to its periphery by Linear Friction Welding (LFW). The monolithic blisk is then heat-treated, finish machined and vibro-polished. Its integrity is tested by the need to accelerate so extremely rapidly from rest to maximum rpm.

Keep 'em flyin' Thumb

TEG

That_Engine_Guy wrote:

Seems the LiftFan has hollow metal blades that are welded into the disk to create a "blisk"

Does that mean if a blade gets FOD damage they have to replace the whole thing?

Elite Joined: Dec 14, 2005 Posts: 586 Status: Offline

I would imagine it would be a 2-level maintenance concept. (1 Flight-line & 2 Depot) Two Cents

1 Flight-line engine technicians would remove the liftfan and change it with another, the unserviceable liftfan would be put into a container and returned to depot (or the contractor)

2 At the depot or contractor the damaged blisk would be changed with another. The liftfan would then be available for the next aircraft. At the depot (or OEM) the bad blade(s) would be cut from the blisk and then new ones would be welded into place. This blisk would then be ready for installation into another liftfan.

From what I know, the F119, F135, and F136 all have blisks in the fan, but all are very tolerant of FOD. Besides metal treatments to help resist FOD, the damage limits for a blisk fan are much more liberal than a hub/disk fan. The blades are a long-chord design that is much stronger than older designs.

I doubt the liftfan would ingest much debris given it's intake position above the aircraft. Nothing like a Vipers intake only 3 feet above the ramp. Shocked

Sure you may get a stray bird, or ice but overall I believe it would be in a much safer position as relating to FOD in general. Two Cents

Elite Joined: Jul 11, 2007 Posts: 633 Status: Offline

That_Engine_Guy wrote:

Sure you may get a stray bird, or ice but overall I believe it would be in a much safer position as relating to FOD in general. Two Cents

You could always strap on one of those bug screens from AutoZone

Elite Joined: Dec 14, 2005 Posts: 586 Status: Offline

How about the test mount screens like this? Shrug

Nothing getting through it! Laughing

Elite Joined: Jul 11, 2007 Posts: 633 Status: Offline

Now that would look funny sitting on top of a jet. How well do you think it would fly? Doh

Elite Joined: Dec 14, 2005 Posts: 586 Status: Offline

Some RR Blisk info.

Quote:

ROLLS-ROYCE SHIPS FIRST BLISK FOR JOINT STRIKE FIGHTER SDD PROGRAMME 2 April 2003

Rolls-Royce has produced its first LiftFan™ blisk for the Joint Strike Fighter (JSF) in the programme’s System Development and Demonstration (SDD) phase.

The blisk, which was machined from a solid piece of material, was completed at the company’s factory in Annesley, Nottinghamshire, England and has been dispatched to the Rolls-Royce facility in Indianapolis, Indiana, US. There it will be assembled into the first SDD aerodynamic rig for the LiftFan, which is due to be tested in July of this year. The first F135 STOVL engine will go to test in early 2004.

The blisk pictured was manufactured as a single part in order to meet a demanding test schedule. Future SDD blisks, which will have fan blades friction bonded onto the hub, are already in manufacture.

A blisk (also called an integrally bladed rotor or IBR) is a one-piece component, consisting of a disk and blades. One of its major advantages over the conventional disk and blade arrangement is the potential weight saving through the elimination of the fixings that secure the blade root to the disk.

Rolls-Royce is a member of the F135 STOVL Propulsion System team, which is led by Pratt & Whitney. Rolls-Royce received a $1 billion contract from Pratt & Whitney in December 2001 for the development work undertaken during the SDD phase.

A high-resolution version of the image is available with this release on the Rolls-Royce website at www.rolls-royce.com/latestnews.

May 23rd, just might be the day! But don't expect to see much at the NAS.

Looks like RR took a little time to catch on to the GE blisk game!

Forum: F-35 Lightning II

F135 blade failure could hold up STOVL JSF