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Vertical Power By Eric Hehs Posted 15 September 2007
http://www.codeonemagazine.com/article.html?item_id=32
"Development Testing In Detail
"Most of our development testing in Florida is associated with low speeds and low altitudes, the lower left-hand corner of the flight envelope," notes Mark Tracy, manager of test operations for Pratt & Whitney at the Florida test site. "We are mitigating the risk for the powered lift flight test program for F-35B. Our work here verifies that the propulsion system will produce the amount of downward thrust needed for a successful flight test program for the F-35B and later for a successful real-world operation."
Recent developmental testing in Florida has focused on a redesigned inlet shape for the lift fan to get more lift and performance and to reduce flow distortion at the face of the lift fan. "The inlet is at ninety degrees to the airflow, so it presents a unique situation," explains Tom Sylvester, a senior engineer for Lockheed Martin present for these particular tests. "We used traditional methods for the initial design, but they just don't work well for a lift fan inlet because of the short distance between the inlet lip and the face of the fan. Unlike more traditional inlets, the airflow doesn't settle out before it gets to the fan surface."
The differences between the original inlet (called the development inlet) and the redesigned inlet (called the flight inlet) are imperceptible to an untrained eye. "The lip of the new inlet is only slightly different — an inch or two wider on the sides and a little taller," Sylvester explains. "The fan itself didn't change, but the inlet door was re-contoured to close securely against the new shape."
Northrop Grumman produced a metal/composite model of the new inlet shape. The model includes an aerodynamic fairing that replicates the fuselage area around the inlet that affects airflow into the inlet. The C14 test stand structure was modified for this model, which was installed on the stand with the rest of the vertical lift system in March 2007.
The vertical lift system with the new inlet and door combination was put through 116 hours of testing. During these tests, a crosswind generator used for testing effects of crosswinds on commercial jet engines was set up next to the test stand. The performance of the new inlet design was evaluated in crosswind angles of ninety degrees and wind speeds up to thirty-five knots.
The testing reduced a lot of un-certainties. "The lift fan performed better than we predicted," Sylvester explains. "The thrust numbers needed for hover are there." The biggest success is the additional thrust achieved from going to the development inlet to the flight inlet. "We increased the thrust and reduced the distortion in the lift fan, which will improve the durability and longevity of the system."
"The results were excellent," says Fran Ketter, research engineering director for Lockheed Martin and the program management interface for F-35 propulsion integration. "The inlet redesign resulted in significant improvements...."
__________
INGENIA ISSUE 41 DECEMBER 2009:
A FLEXIBLE JET FIGHTER
http://www.ingenia.org.uk/ingenia/issue ... /mehta.pdf (0.5mb)
___________
http://www.theengineer.co.uk/in-depth/r ... 08.article
_________
http://www.aviationweek.com/aw/blogs/de ... d&plckScri
Vertical Power By Eric Hehs Posted 15 September 2007
http://www.codeonemagazine.com/article.html?item_id=32
"Development Testing In Detail
"Most of our development testing in Florida is associated with low speeds and low altitudes, the lower left-hand corner of the flight envelope," notes Mark Tracy, manager of test operations for Pratt & Whitney at the Florida test site. "We are mitigating the risk for the powered lift flight test program for F-35B. Our work here verifies that the propulsion system will produce the amount of downward thrust needed for a successful flight test program for the F-35B and later for a successful real-world operation."
Recent developmental testing in Florida has focused on a redesigned inlet shape for the lift fan to get more lift and performance and to reduce flow distortion at the face of the lift fan. "The inlet is at ninety degrees to the airflow, so it presents a unique situation," explains Tom Sylvester, a senior engineer for Lockheed Martin present for these particular tests. "We used traditional methods for the initial design, but they just don't work well for a lift fan inlet because of the short distance between the inlet lip and the face of the fan. Unlike more traditional inlets, the airflow doesn't settle out before it gets to the fan surface."
The differences between the original inlet (called the development inlet) and the redesigned inlet (called the flight inlet) are imperceptible to an untrained eye. "The lip of the new inlet is only slightly different — an inch or two wider on the sides and a little taller," Sylvester explains. "The fan itself didn't change, but the inlet door was re-contoured to close securely against the new shape."
Northrop Grumman produced a metal/composite model of the new inlet shape. The model includes an aerodynamic fairing that replicates the fuselage area around the inlet that affects airflow into the inlet. The C14 test stand structure was modified for this model, which was installed on the stand with the rest of the vertical lift system in March 2007.
The vertical lift system with the new inlet and door combination was put through 116 hours of testing. During these tests, a crosswind generator used for testing effects of crosswinds on commercial jet engines was set up next to the test stand. The performance of the new inlet design was evaluated in crosswind angles of ninety degrees and wind speeds up to thirty-five knots.
The testing reduced a lot of un-certainties. "The lift fan performed better than we predicted," Sylvester explains. "The thrust numbers needed for hover are there." The biggest success is the additional thrust achieved from going to the development inlet to the flight inlet. "We increased the thrust and reduced the distortion in the lift fan, which will improve the durability and longevity of the system."
"The results were excellent," says Fran Ketter, research engineering director for Lockheed Martin and the program management interface for F-35 propulsion integration. "The inlet redesign resulted in significant improvements...."
__________
INGENIA ISSUE 41 DECEMBER 2009:
A FLEXIBLE JET FIGHTER
http://www.ingenia.org.uk/ingenia/issue ... /mehta.pdf (0.5mb)
___________
http://www.theengineer.co.uk/in-depth/r ... 08.article
_________
http://www.aviationweek.com/aw/blogs/de ... d&plckScri
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber