Forum: F-35 Engine

F-35B Completes First Airborne Engine Start Tests Sep/4/2012
By Victor Chen, F-35 Integrated Test Force Public Affairs

http://www.navy.mil/submit/display.asp?story_id=69384

"EDWARDS AIR FORCE BASE, Calif. (NNS) -- The F-35 integrated test force announced the completion of a major prerequisite test for in-flight performance on the short take-off and vertical landing variant of the F-35 Lightning II Joint Strike Fighter Sept. 4.

BF-2 completed the first air starts, which test the ability of the F-35's propulsion system to restart during flight. Verifying the restart capability of the propulsion system is part of the initial flight test program for the F-35 and a prerequisite for high angle-of-attack testing, scheduled to start next year.

"High alpha, or angle-of-attack tests, are important for us to fully evaluate the aircraft's handling characteristics and warfighting capability," said Marine Corps test pilot Lt. Col. Matthew Kelly. "Maximizing the performance of the airplane around the very slow edges of the flight envelope is probably some of the most challenging testing we will conduct. After we get through it, we'll know a lot more about how this aircraft will perform during combat within visual range."

Using multiple restart methods during the tests, BF-2 successfully completed a series of 27 air starts at various altitudes Aug. 15.

To execute air start testing, the F-35 Integrated Test Force (ITF) at Naval Air Station Patuxent River ferried BF-2 and an F/A-18 chase aircraft from Air Test and Evaluation Squadron (VX) 23 to the F-35A testing facility at Edwards AFB.

"At Edwards, we have a unique testing range, which provides ideal and controlled conditions for completing air start testing. The Edwards range is comprised of 20,000 square miles of airspace, and has 65 linear miles of useable landing area on Rogers and Rosamond Dry Lakes, if required during engine out testing," said Lt. Col. George N. Schwartz, commander of the 461st Flight Test Squadron and government site director. "In addition, we've recently completed air start testing on the F-35A, so we're able to share some of our expertise with the Pax team as well."...

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Let's face it - the F-35 will never be as good as... (insert your fave aircraft - HOKAY?) Very Happy

USMC's F-35B completes air start testing at Edwards AFB By Dave Majumdar Sept 4, 2012

http://www.flightglobal.com/blogs/the-d ... -star.html

"...Both versions of the jet will have an angle-of-attack limit of 50 degrees, which is comparable to the Boeing F/A-18. But while the F/A-18s top out at about 50 degrees AOA--though with some effort one can momentarily exceed that--the Hornet/Super Hornet doesn't have an alpha limiter. Neither does Lockheed Martin's other 5th generation fighter, the F-22 Raptor.

At the Farnborough air show in July, Lockheed F-35 test pilot Al Norman told me it was a safety feature... But it's still kinda curious as to why the company and F-35 Joint Program Office chose to have a hard 50 degree limit...."

My guess as to why there is a hard limit is that the F-18 can barely get to 50 so a hard limit was not needed but the F-35 can go past 50 if the pilot tried so a hard limit was needed.

Your GLASS is HALF FULL SWP whereas others are sadly half empty.... Very Happy

SpudmanWP wrote:

My guess as to why there is a hard limit is that the F-18 can barely get to 50 so a hard limit was not needed but the F-35 can go past 50 if the pilot tried so a hard limit was needed.

Older F/A-18A-D could depart controlled flight at above 45 AoA and can't maintain the energy above 30 AoA, so the limit was rarely hit, although some falling leaf departures occured.

The F/A-18E/F can handle higher AoA limits, and can get to over 50 AoA in clean configuration although not sustained for very long.

Last edited by 1st503rdsgt on Sep 05, 2012 - 09:16 PM; edited 1 time in total

It's just simpler to limit the thing. Fifty degrees of sustainable AoA is plenty respectable as there will be little need to perform useless airshow tumbling in real combat. Only the fanboys care if it can do a cobra or not.

1st503rdsgt wrote:

It just simpler to limit the thing. Fifty degrees of sustainable AoA is plenty respectable as there will be little need to perform useless airshow tumbling in real combat. Only the fanboys care if it can do a cobra or not.

Departing controlled flight isn't a game. There is a significant chance the pilot will have to eject and loose a $30m - 150m jet.

The MiG-29A can do a maneuver that looks like a cobra, but only at risk of departing controlled flight, within the post-stall envelope. The Super Hornet can do a similar maneuver with lower risk of a compressor stall, but still risking a departure.

As for "combat" one advantage the MiG-29 has in a knife fight is the jet can bleed energy during a high alpha roll, resulting in the bogie overshooting. The F/A-18E/F can do this better than F/A-18A-D models, but not quite as sharp as the MiG-29. A sharp roll with heavy external stores, and it will do damage to the jet. FCS limits exist for a reason.

Once the AoA limits have been properly tested, then they can start to determine the Tactical ACM performance guide for the jet, as this is also a significant step towards IOC.

A F/A-18 can go into a spin departure and even with spin-mode FCS, recovery is difficult. Depending on CG, Altitude etc. a flat spin may result, which is basically unrecoverable. A F-35 would have similar characteristics, but hopefully FCS limiters reduces the chance of it happening. They use a spin chute during testing to recover the jet.

Remember, pushing the envelope too hard is a good way to end up in a flat spin for certain jets. Its not just in Top Gun. An F-15 almost went into a flat spin during a dogfight in '91 over Iraq. An F-15E went into a flat spin during Odyssey Dawn over Libya and the crew ejected and were rescued. Another F-15 went into a flat spin near Nellis in 2011.

neurotech wrote:

[..... They use a spin chute during testing to recover the jet...

http://www.f-16.net/f-16_forum_viewtopic-t-20307.html

"Right now, engineers are in the final stages of attaching an anti-spin parachute to aircraft AF-4. "We've finished almost everything for that," Schwartz says. The next step will be to test deploying the chute during runway taxi trials in order to make sure it works properly."

High AoA testing will be on A model, first; etc, Smile

Forum: F-35 Engine

F-35B Completes 1st Airborne Engine Start Tests Edwards AFB