Well, I must confess, I'm not quite as studious as Thomas Edison, shown to the right, in this dated photograph (of a likewise rather dated Mr. Edison). But after the cookies and milk run out, I do pay some attention in class (Airframe and Powerplant).One of the interesting activities was a field trip to a local repair shop, where there was a demonstration of working with composites, especially repairing them after some ham-fisted damage is done. (The instructor stared at me a lot during this demonstration, for some reason or other). It turns out that, much to my surprise, that composites are really pretty darned easy to repair. The basic technique is to-
1) Identify the area of damage
2) Remove damaged material
3) Glue new stuff in
That all sounds simple, and when performed by someone familiar with the methods, it really IS simple.
A little tap hammer is used to acoustically listen for delaminations and damage, although there are acoustic "scanners" which can do the same thing with ultrasound.
Then material is sanded down until the delamination is removed.
If a honeycomb core is used, even it can be cut out and "plugged" with a honeycomb insert (and lots of glue/resin).
Layers of Carbon Fiber fabric are then laid over the damage, in orientation described dictated by the specific location (and load path at that location) as described in a repair manual. Plies are alternated 0-90 and 45-135 degrees, up to 4 plies thick, and then resin is worked into the fabric and heat cured. Another set of up to 4 plies is laid, and cured. Etc, until the desired strength is obtained.
Lightning strike fiber (copper mesh, or some such) is then laid over the repair- some sort of smoothing jel for a nice finish is applied, and it's cured and painted. Typically a repair takes one to two shifts, I was told. Neat!
One thing we were cautioned about regarded working with the materials. The resins of course, are rather nasty. But fragments/filliments of the carbon fiber itself are pretty bad news too: the work bench was actually a vacuum table, to capture the dust. Wikipedia has a nice article about Carbon Fibers ("Carbon fibers are the closest to asbestos in a number of properties...").
Although discovered in the good ole US of A, it seems our plucky British friends were early adopters of this rather, um, "disruptive" technology:
"The high potential strength of carbon fiber was realized in 1963 in a process developed at the Royal Aircraft Establishment at Farnborough, Hampshire.. The process was patented by the Ministry of Defence and then licensed by the NRDC to three British companies: Rolls-Royce, already making carbon fiber, Morganite and Courtaulds.. They were able to establish industrial carbon fiber production facilities within a few years, and Rolls-Royce took advantage of the new material's properties to break into the American market with its RB-211 aero-engine.
"Even then, though, there was public concern over the ability of British industry to make the best of this breakthrough. In 1969 a House of Commons select committee inquiry into carbon fiber prophetically asked: "How then is the nation to reap the maximum benefit without it becoming yet another British invention to be exploited more successfully overseas?" Ultimately, this concern was justified. One by one the licensees pulled out of carbon-fiber manufacture. Rolls-Royce's interest was in state-of-the-art aero-engine applications. Its own production process was to enable it to be leader in the use of carbon-fiber reinforced plastics. In-house production would typically cease once reliable commercial sources became available.
"Unfortunately, Rolls-Royce pushed the state-of-the-art too far, too quickly, in using carbon fiber in the engine's compressor blades, which proved vulnerable to damage from bird impact. What seemed a great British technological triumph in 1968 quickly became a disaster as Rolls-Royce's ambitious schedule for the RB-211 was endangered. Indeed, Rolls-Royce's problems became so great that the company was eventually nationalized by Edward Heath's Conservative government in 1971 and the carbon-fiber production plant sold off to form Bristol Composites."
Now it doesn't quite date back to Edison's time (February 11, 1847 – October 18, 1931), but some keen eared folks (unfortunately, Mr. Edison was rather deaf) will recall that the RB211 was destined for the Lockheed L1011.
"Because Lockheed was itself in a vulnerable position, the government required that the US government guarantee the bank loans that Lockheed needed to complete the L-1011 project. Despite some opposition, the US government provided these guarantees. In May 1971, a new company called "Rolls-Royce (1971) Ltd." acquired the assets of Rolls-Royce from the Receiver, and shortly afterwards signed a new contract with Lockheed. This revised agreement cancelled penalties for late delivery, and increased the price of each engine by £110,000".
"A major differentiator between the L-1011 and the DC-10 was Lockheed's selection of the Rolls-Royce RB211 engine for the L-1011. As originally designed, the RB211 turbofan was an advanced three-spool design with a carbon fibre fan, which would have better efficiency and power-to-weight than any competing design. This would make the L-1011 more efficient, a major selling point.
"American Airlines opted for the Douglas DC-10, although it had shown considerable interest in the L-1011. American's intent in doing so was to convince Douglas to lower its price for the DC-10, which it did. Without the support of American, the TriStar was launched on orders from TWA and Eastern Air Lines. Although the TriStar's design schedule closely followed that of its competitor, Douglas beat Lockheed to market by a year due to delays in power plant development. In February 1971, after massive development costs associated with the RB211, Rolls-Royce went into receivership. This halted L-1011 final assembly and Lockheed investigated the possibility of a US engine supplier, one option presented would have been the potential outsource of the RB-211 production to Orenda, but by then it was considered too late to change engine suppliers to either General Electric, or Pratt & Whitney.
"The British government agreed to approve a large state subsidy to restart Rolls-Royce operations on condition the U.S. government guarantee the bank loans Lockheed needed to complete the L-1011 project...
"Kenneth Keith, the new chairman who had been appointed to rescue the company (RR), persuaded Stanley Hooker to come out of retirement and return to Rolls. As technical director he led a team of other retirees to fix the remaining problems on the RB211-22. The engine was finally certified on 14 April 1972,[11] about a year later than originally planned, and the first TriStar entered service with Eastern Air Lines on 26 April 1972. Hooker was knighted for his role in 1974."
It is interesting to note that the original Eclipse engine (the Williams EJ-22) was also a three-spool design. Disruptive engine technology is a real pain!
Speaking of that...the name Orenda made MY ears perk up (although this late at night, that's about all). Fellow GA propeller heads (as opposed to turbofan fans), will perhaps recall one of the pseudo urban legands of late, the Orenda V8.
"The Orenda OE600 is a 600 hp-class liquid-cooled 8-cylinder V-block aircraft engine intended to re-introduce piston power to aircraft normally powered by the famous Pratt & Whitney Canada PT6 turboprot. The piston engine offers much better fuel economy, which Orenda Aerospace felt would be attractive for older aircraft whose engines were reaching the end of their lifespan. However, changes in Orenda's business in the post- 9/11 time frame led to the project being canceled.
"Unfortunately, the events of 9/11 required Orenda to re-focus entirely on their military projects, and the OE600 project was canceled. The design was later purchased by a group of investors who intend to sell the engine under the Texas Recip brand, but it is unclear if this project is continuing. On August 29, 2006 the president of Texas Recip, Paul Thorpe was sentenced to 3 years and five months for defrauding investors, telling them the money was being invested in the engine project, or other investments, when it was actually being used to pay off investors in a previous scheme.
"More recently the project has been picked up by TRACE Engines of Midland, Texas. Yorkton Aircraft is handling Canadian installations in agricultural aircraft."
While current VLJ Engines are Candian (PWC-61X), Orenda is also Canadian.
It seems the disruptive engine game can lead to knighthood, a Collier trophy, or a jail sentence- (overall, I'd say Eclipse should be pleased with the Collier! :)
