If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#25
|
|||
|
|||
The Melting Deck Plates Muddle - V-22 on LHD deck....
On Dec 9, 11:22*pm, Mike wrote:
StrategyPage.com December 2, 2009 The Melting Deck Plates Muddle by James Dunnigan Earlier this year, the U.S. Navy discovered that the heat from the MV-22's gas turbine engines, which blow their exhaust right on to the deck of the LHD while waiting to take off, caused high enough temperatures to the steel under the deck plates, to possibly warp the understructure. This was already a known potential problem with the new F-35B vertical takeoff jet fighter. So now the Navy has two hot new aircraft that require an innovative solution to the melting deck problem. The Navy also discovered that the exhaust heat problem varied in intensity between different classes of helicopter carriers (each with a different deck design.) The Navy is looking for a solution that will not require extensive modification of current carrier decks. This includes a lot of decks, both the eleven large carriers, and the ten smaller LHAs and LHDs. This is shaping up as another multi-billion dollar "oops" moment, as the melting deck problem was never brought up during the long development of either aircraft. Previously, the Harrier was the only aircraft to put serious amounts of heat on the carrier deck, but not enough to do damage. But when you compare the Harrier engine with those on the V-22 and F-35B, you can easily see that there is a lot more heat coming out of the two more recent aircraft. Someone should have done the math before it became a real problem. Here is the problem laid out in numbers F-35 and V-22: Keeping it Cool on Deck Posted by Graham Warwick at 6/24/2009 8:43 AM CDT We've heard how the stealthy F-22 and F-35 are flying thermos bottles, struggling under the huge heat loads imposed by their powerful engines and systems. Well it seems the latest generation of vertical-lift aircraft is turning the flight decks of US Navy amphibious assault ships into frying pans. blog post photo Photo: US Navy The initial culprit is the MV-22 tiltrotor, but the big concern is the STOVL F-35B, which is due on deck after 2012. With nacelles tilted and rotors turning, hot exhaust from the Osprey's engines is buckling the decks, and Navy studies warn repeated buckling will cause deck failure at 40% of planned ship life. F-35B exhaust plumes are expected to have a "severe thermo-mechanical impact" on the structure and non-skid surface of the flight deck. That's according to a new solicitation from the Office of Naval Research, which is looking for new ideas for flight deck thermal management. The solicitation is looking for alternatives to a DARPA/ ONR program that is already looking at "cooled heat pipe technologies" to overcome the thermal issues. It's not a trivial problem. For the MV-22, where the exhausts are close to the deck when the nacelles are vertical, buckling has been observed after just 10min of sitting on the deck, rotors turning. The F-35B will be in STOVL mode for a fraction of that time, but is expected to cause even more heating of the deck. ONR is looking for thermal management technologies that can keep the deck surface temperature below 300ºF when exposed to MV-22 exhaust plumes for 90 minutes before takeoff, and F-35B exhaust plumes for 2 minutes when landing. And cooling the deck is not enough - any solution has to be compatible with the deck's non-skid coating. It also has to be affordable and capable of being installed below deck or retrofitted above deck. Tall order. blog post photo Photo: Lockheed Martin Based on measurements taken during recent hover-pit tests, Lockheed Martin does not believe there will be an issue with deck temperatures. One acknowledged area of concern is the combined auxiliary/emergency powerpack, or IPP, which exhausts downwards on the STOVL aircraft. (It exhausts upwards on the F-35C carrier variant to protect deck crew, but downwards on the F-35B and CTOL F-35A to save weight and gain fuel volume.) The IPP has two modes: bleed and bleed-and-burn. In bleed mode the exhaust is relatively cool, Lockheed says. In bleed-and-burn, fuel is burned in the IPP to generate more power, and exhaust temperature rises. Because of operator concerns about surface heating, Lockheed says the pilot will have the ability to switch the IPP back to bleed mode if holding on the runway, or deck. http://www.aviationweek.com/aw/blogs...6-08049291946b |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Flight deck queens | Michael Huber[_2_] | Aviation Photos | 2 | January 19th 08 06:38 AM |
Kiev's deck - with Yak-36s and Ka-25s | Dave Kearton | Aviation Photos | 0 | March 2nd 07 06:12 AM |
Ka-25s on Kiev's deck | Dave Kearton | Aviation Photos | 0 | March 2nd 07 06:09 AM |
Straight deck ops | Greasy Rider | Naval Aviation | 18 | January 10th 07 01:35 AM |
Deck height | Sean Trost | Home Built | 5 | July 16th 04 03:46 AM |