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