Forum: F-35 milestones

http://www.flightglobal.com/news/articl ... ff-385757/

F-35B performs first vertical take-off

By: DAVE MAJUMDAR WASHINGTON DC

.........test pilots at Naval Air Station Patuxent River, Maryland, performed the first Lockheed Martin F-35B Joint Strike Fighter vertical take-off on 10 May.

.......Corps' short take-off and vertical landing variant had a requirement to perform vertical take-offs right from the outset of the JSF programme. However, the capability is not emphasised because the F-35B would not be able to carry a tactically significant payload in that configuration.

...the USMC envisions its F-35Bs performing short rolling take-offs carrying a full load of ordnance and fuel, and then performing a vertical landing once the aircraft returns to the amphibious assault ship or expeditionary airfield.

The concept of operations is similar to that currently flown by the USMC's Boeing AV-8B Harrier II squadrons. Although the Harrier is often touted as a vertical take-off and landing machine, it flies a similar short take-off and vertical landing profile for the overwhelming majority of its missions.

The original X-35B prototype demonstrated the ability to take off vertically in 2001.

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Now THAT was a sight to see!

No video?

The day of the unmanned aircraft 15 May 2013 By Dave Majumdar

Quote:

"... Speaking of Lockheed--the company showed us a video of the F-35B performing a vertical take-off from last Friday, but paradoxically because of the Navy and Joint Program Office, are not allowed to release it--which sucks for you guys. Frankly, it's just bizarre--it's a big base with lots of people and when a large 40,000lbs fighter takes-off vertically and hovers, folks are going to take notice."

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

Video

http://youtu.be/zW28Mb1YvwY

orkss wrote:

Video

http://youtu.be/zW28Mb1YvwY

So, actually, it looks like the 'B is able to spool up it's engine pretty high without rotating it's exhaust all the way down. The lift fan must be vectoring forward to counter the thrust.

Why does Lockheed call this the first F-35B VTOL? Is the aircraft in this video posted in 2007 not the F-35B?

http://www.youtube.com/watch?v=XIsIzjVi7j4

I have noted that the jet in the video has some different hatches then the one from Naval Air Station Patuxent River, but what is the main difference?

'guy@rdaf.dk' the video you cite was uploaded in 2007 - it shows the X-35B demonstrator which does have different hatches. The main difference is that the aircraft is the 'demonstrator' demonstrating in 2001. A good bunch of X-35B photos here:

http://www.jsf.mil/gallery/gal_photo_cdp_loc_stovl.htm

An explanation of the 'demonstrator' differences compared to production aircraft is in this PDF:

http://www.codeonemagazine.com/images/C ... 8_6299.pdf (7.1Mb)

SAME INFO as in PDF above here:

X to F: F-35 Lightning II And Its X-35 Predecessors By Eric Hehs 15 May 2008

http://www.codeonemagazine.com/article.html?item_id=28

X-35B was also a much lighter aircraft as it did not have the weapon bays or any avionics above what was needed to get it to fly.

'count_to10' commented above:

Quote:

"So, actually, it looks like the 'B is able to spool up it's engine pretty high without rotating it's exhaust all the way down. The lift fan must be vectoring forward to counter the thrust."

One thing to keep in mind is that the distance of the video camera from the aircraft means that there is a lag of the sound to what we see (by whatever time delay). Jet engines are slow to spool up from idle; but once at a signficant RPM (for example 85% in the A-4) engine acceleration is rapid by comparision to earlier 'from idle accel'. Without knowing more about what is going on inside the aircraft and relying only what you see and hear (which is not in synchronisaton) may lead to erroneous speculative conclusions and you may well be correct I'll add.

All F-35s have a quality wheel brake system which I will guess is able to hold the aircraft still (as in the A-4 case at 85% RPM or higher) until they cannot. Whatever else is going on just before the Vertical Takeoff is anyone's guess. I can see the aircraft lifting nicely vertically with wheels still on the ground - then just at lift off the aircraft nudges forward - air/jet bourne - showing a slight lag between the thrust aft and the counter thrust from the lift fan forward. Both work together in STOVL mode. I wonder if that 'lag' slight forward movement will be countered by a change in software controls. Perhaps there was some wind and again I'll guess the aircraft is pointing into the wind? This is all automatic unless the test pilot is going to do a manual style VTO (if that is possible). I'll make a slomo video snippet of the lift off at half speed with sound at same half speed. At slower video speeds the 'nudge forward' is lost and the sound is weird.

Well, I noticed that the engine sound was spooling up while the exhaust was at a 45 degree angle -- so a delay really isn't an issue.

'count_to_10' I'll repeat, unless you know what is happening in the cockpit regarding engine and the automatic sequence required for a Vertical Takeoff, all you are doing is guessing. One day all will be revealed. As indicated in another thread - the F-35B is able to fly / hover backwards at 30 knots so it has a ton of ability to withstand a lot of abuse. Very Happy

For ease of reading here is the quote:

F-35 Flight Testing At Pax By Eric Hehs 15 October 2012

Quote:

"“...While many test points are shared across all three variants of the F-35, others are variant-specific. The vertical lift capability of the F-35B, for example, creates a unique flight envelope that goes all the way down to zero airspeed at zero feet altitude. “The F-35B can fly backwards,” noted Eric Faidley, a Lockheed Martin flight test engineer assigned to BF-1. “In fact, its maximum backwards groundspeed is thirty knots.”

The only time an F-35B might hover at thirty knots in reverse in an operational setting would involve an overshot landing, Faidley explained. “In such instances, pilots would typically not back up and, instead, go back around in the pattern and attempt another landing,” he said...."

http://www.codeonemagazine.com/f35_arti ... tem_id=110
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"...ANNEX – CONTROL LAW RESEARCH USING THE VAAC HARRIER by John Farley [UNIFIED Control Laws which are used by the F-35B and tested initially in the VACC Harrier along with other variations of Control Laws]

Quote:

"...A throttle-type left hand inceptor, incorporating two detents, commands longitudinal acceleration.

Putting the inceptor in the centre detent holds the current speed. Acceleration or deceleration is selected by moving the lever forward or aft of the detent, with full travel demanding maximum available performance. Decelerating through 35 kt ground speed starts a blend and below 25 kt the aft detent commands zero ground speed. Either side of the aft detent gives the pilot a closed loop control of ground speed up to 30 kt forwards or backwards...."

http://www.rafmuseum.org.uk.nyud.net/do ... -Story.pdf (25Mb)
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Discussions about this aspect may be found by searching "backwards" in this forum - here is one example: http://www.f-16.net/f-16_forum_viewtopi ... wards.html