Forum: F-35 Lightning II

Joint Strike Fighter acing tests, pilots report By Dave Majumdar - Staff writer Feb 27, 2011

http://www.airforcetimes.com/news/2011/ ... t-022611w/

"...The aviators have completed 23 vertical landings with the B-model aircraft, more than half of the 42 needed for the Marine Corps to begin trials at sea aboard an amphibious assault ship.

“We’ve done more vertical landings in the month of January” — 13 — “than we did last year. So this is coming fast now,” one of the test pilots, Marine Lt. Col. Matt Taylor, said in a telephone interview from Naval Air Station Patuxent River, Md.

Landing vertically in the F-35B is easy, Taylor said.

“I’ve flown a lot of airplanes. This is the easiest one there is to land,” said David “Doc” Nelson, who flies for Lockheed Martin, the F-35’s prime contractor.

Nelson said that even pilots who have never flown a vertical-landing aircraft, such as colleague Jon Beesley, have no trouble handling the F-35B.

The test pilots also raved about the JSF’s maneuverability, calling it a nimble machine. For example, the F-35 can handle better than a 40-degree angle of attack, which is related to the amount of lift...."

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I kind of thought I said multiple times that the F-35B was simpler for the pilot to land, it was what goes on "behind the scenes" that is more complex. As indicated in the recent posts, the computers handle the stuff, the entire slowing, hovering and landing sequence is a program, executed by the FCS, with the pilot controlling the rate of the descent from the hover.

According to a couple of sources, one recent one being the special F-35 supplement in the May, 2011 Air International, once the program takes you to the hover, it will hold the a/c in position, no doubt compensating for relative wind, and the pilot can reposition in all axes by 1 meter. It's sort of like manual vs. automatic transmission in a car. Manual gives you more control and can be more flexible, but automatic, while more complex, is simpler to operate and requires far less input.

aaam, I could have been clearer in my response: It was to this aspect 'of less flexibility' for F-35B mentioned. Yes I agree about complexity behind the scenes (so to speak) making life easier for F-35B pilot. You said in part:

"However, my understanding is that the idea is to deliver the aircraft to a hover, and there is little freedom during this process or to reposition the aircraft once the hover is achieved, the FCS holding the a/c over the touchdown point. In fact, I believe the pilot input at this point is to move the sidestick until a stop is felt and hold it, and the the FCS controls power and everything else until the F-35B is firmly on the ground. Much simpler for the pilot, but less flexibility." (My emphasis).

To make my life easier (looking for different quotes) I decided to put all the 'easy to fly F-35B' in one place for future reference but I was responding to the 'less flexibility issue'. One particular part of the many quotes above got me started....

Flight test ‘lite’:
Qinetiq’s VAAC Harrier highlights capabilities of Lockheed Martin’s STOVL Joint Strike Fighter
By Craig Hoyle on August 25, 2006

http://www.flightglobal.com/blogs/fligh ... -vaac.html

"... the stability offered by the F-35B’s liftfan and roll posts will be truly spectacular, with only slight inputs required to manoeuvre it around an airfield or onto the deck of an aircraft carrier or assault ship."

How about typing out the relevant quote from the Air International May 2011 please. Or is it online?

spazsinbad wrote:

How about typing out the relevant quote from the Air International May 2011 please. Or is it online?

OK, I don't believe it's online, so let me just type out the relevant bit, which probably won't violate copyright [Peter Wilson is an ex-RN Sea Harrier pikot and presently the STOVL lead test pilot at Pax River]:

begin quote

Commenting on the hover Peter Wilson told Air International, "It is absolutely astonishing, the aeroplane is rock solid in the hover and holds its position extremely accurately without pilot input".

The aircraft can be accurately moved left to right, fore and aft, and up and down by 3ft. [1m] at the preferred position of 100ft (33m) above the ground before descent.

end quote

BTW, they do say that the the Unified Control Law which governs control of the F-35B was developed during research on the VAAC Harrier.

aaam thanks. There is some information about development of the VACC Harrier Unfired Control Law on the 'very long thread':

http://www.f-16.net/index.php?name=PNph ... acc#176845
&
Search for 'VACC' to get more bits. A remarkable aircraft was the VACC Harrier.

BTW I read the quote (without any other context) as saying that the aircraft can be moved with precision in increments of 3 ft. in any direction in the hover. Are you reading it that the aircraft can be moved only 3 feet? To me being able to control any aircraft with that precision in those unusual circumstances (hover) is remarkable.

Last edited by aaam on Jun 30, 2011 - 04:02 AM; edited 1 time in total

spazsinbad wrote:

aaam thanks. There is some information about development of the VACC Harrier Unfired Control Law on the 'very long thread':

http://www.f-16.net/index.php?name=PNph ... acc#176845
&
Search for 'VACC' to get more bits. A remarkable aircraft was the VACC Harrier.

BTW I read the quote (without any other context) as saying that the aircraft can be moved with precision in increments of 3 ft. in any direction in the hover. Are you reading it that the aircraft can be moved only 3 feet? To me being able to control any aircraft with that precision in those unusual circumstances (hover) is remarkable.

As I read it, once the button is pushed the FCS automatically delivers the aircraft from a speed < 250knots to a stable hover over a designated (I don't know how) spot at 33m with 1m accuracy and holds it there, which is a remarkable achievement, The pilot can then microcorrect the final position (that's where the 1m comes in) and when ready moves the sidestick forward and holds it until the a/c senses touchdown, at which point the system brings power to idle and rotates the nozzle back for taxi. Hopefully, the system that detects touchdown is better than the one on the Mars Polar Lander! Doh

OK thanks for clarification of F-35B autoland 'aaam'. Also if required the pilot can 'go to manual' to make corrections or move to another landing spot with precision as described.

spazsinbad wrote:

OK thanks for clarification of F-35B autoland 'aaam'. Also if required the pilot can 'go to manual' to make corrections or move to another landing spot with precision as described.

For sure

Hopefully that's so, but then we thought you could 'go to manual' to open the canopy on the Raptor! Very Happy

For the F-22 these days you only need to switch off the OBOGS and then it is manual all the way..... Twisted Evil

Last edited by spazsinbad on Jul 01, 2011 - 10:25 AM; edited 1 time in total

VACC Harrier First Auto Vertical Landing May 2005 .FLV video 5.8Mb

Hmmm... says Extension .FLV not allowed...

Found FREE 'FLV converter' so it has done the job now .FLV to .WMV attached 6Mb

Second Verse Same as the First (above). The .FLV proved to be untranslatable to another video format with wot I got so here is original: All change - found FREE FLV Converter so original converted to .WMV available above also.

http://www.a4ghistory.com/VACCharrierAu ... ay2005.flv (5.8Mb)

Best to right mouse click and 'Save Target As...'

Now here is an excerpt from the LM Guy Demonstrating F-35B functions in simulator talking about flight control computer etc. Necessarily this is only a small part of the Utube version available at: http://www.youtube.com/watch?v=OkWuB9wA ... r_embedded

Another report about Harrier 'rolling landings' and other 'how to fly' AV-8 stuff excerpt:

Jeff Ethell's Pireps - AV-8 Harrier January 19, 2010

http://www.airlandseaweapons.com/blog/4 ... 8-harrier/

“...Flying the Harrier requires an absolute mastery of vertical flight basics and helicopter experience is usually mandatory, even if a new pilot has to be given several hours in a chopper before flying the jet. The coordination required to transition from vertical to level flight, especially when accelerating away from a hover, is critical. If the aircraft gets turned "out of wind," that is, if it is not pointing into the wind, it begins to roll over and fall out from under you. A little ten cent weathervane in front of the windshield turns out to be the most valuable instrument on board, indicating wind direction in relation to the aircraft. Keep it pointing forward and everything is fine.

Take-off and landing comes in eight possible combinations...the pilot never gets bored. Take-off: conventional, short (STO), rolling vertical (RVTO), vertical (VTO). Landing: conventional, slow, rolling vertical (RVL), vertical (VL).

Since I was looking forward to the jet's vertical capabilities, my first conventional take-off in the AV-8A took me by surprise. With a combat weight of 20,000 pounds and 21,000 pounds of thrust, the Harrier has the same acceleration as the F-16 or F-15...a greater than 1-to-1 thrust-to-weight ratio. As I quickly moved the throttle forward my head was slammed back into the headrest and in seconds the Harrier was airborne, then climbing virtually straight up. The controls are immediately sensitive to the touch, so much so the jet is best flown with fingertip pressures on the stick. Important information such as speed, altitude, angle of attack, heading and thrust vector all read out on the HUD (Head Up Display) glass in front so you don't have to spend much time with eyes inside the cockpit.

My first landing was conventional, though this is actually the more dangerous way to land since four sets of landing gear have to touch down at the same time while traveling very fast. If not done right the aircraft can bounce out of control. The more stable slow landing is flown at 120 to 140 knots with 60 degrees of nozzle deflection.

The short take-off can be made two ways: accelerate to 65 knots and deflect the nozzles to 65 degrees, which makes the machine jump off the ground in a scant 300 feet...one second it's normal linear acceleration, then the thing is clawing vertically into the sky like an elevator. A quick shove on the nozzle lever to full forward and the Harrier jolts ahead immediately to accelerate away. The less intimidating procedure is to accelerate to 110 knots then pull the nozzles to 50 degrees for a longer take-off run.

Bringing the jet around for the first vertical landing can be an unnatural act for a fixed wing jet pilot since you have to ignore the fear of losing airspeed. Power is reduced to 90% and nozzles set at 90 degrees as the nose ever so gently comes up while airspeed falls below 100 knots. Before you know it the Harrier is hovering on a column of jet exhaust just above the pad. The puffer reaction controls on the end of each wing and at nose and tail operate off bleed air from the engine with thrust activated and increased as the nozzles are deflected down. Movements of stick and rudder bring quick response, much like a helicopter but with no vibration and the moment arm being below the fuselage instead of under a rotor head.

With the jet stabilized at an 8-degree angle of attack, the power is brought back slightly until a descent of about five feet per second lowers us to the pad. Here, more than ever, I had to be very light on the controls but immediate with any input. Entering ground effect is unsettling as the exhaust hits the wings and tail plane...the entire machine trembles and shakes and control inputs have to increase to the point it feels as if you are moving the stick all over the cockpit to stay level. The power then has to be increased to avoid being sucked down into the ground. With a last great rumble the jet bounces onto the ground...immediate idle on the power and nozzles full aft to avoid ingestion of any foreign objects into the engine. If there is a great deal of debris on the landing surface the best technique is a rolling vertical landing with nozzles at 70 degrees and a forward speed of 50 knots.

There is really nothing to prepare one for a vertical take-off...nozzles to the hover stop, then slam the throttle forward. The Harrier instantly rockets off the earth straight up. At 50 feet bring the power back to 95% and the aircraft is hovering again. Throttle up to 100%, nozzles gradually to full aft and you accelerate away from a midair start to over 200 knots in a few seconds at that same fabulous rate. Flying the Harrier is a unique experience in military aviation, and certainly one of the most breathtaking.”

spazsinbad wrote:

aaam, yes the F-35B can carry out an automatic hover vertical landing and it has demonstrated that ability. However the pilot is able to control it in any phase of flight - within limits - under control of the FCS, which necessarily starts to limit what the pilot can do in certain configurations. However this computer system limits the aircraft in any other flight situation - not just in vertical landing mode.
______________________

Just Push ‘Auto-Land’: April 2011
“A Lockheed Martin F-35B short takeoff & vertical landing test aircraft last week achieved an impressive milestone, according to Warren Boley, Pratt & Whitney military en-gines president. “For the first time,” Boley said in an in-terview, “a pilot pushed a button & the [air]plane landed autonomously.” Boley joked that the pilot could fold his hands behind his head or ‘read the paper’ while the air-plane safely settled down to a vertical landing from hover. The flight was the 74th vertical landing of the F-35 test program, & the fact that the Marine Corps was willing to allow the test indicated high confidence in the airplane & its Pratt-supplied F135 engine, Boley told the Daily Report April 8.” — John A. Tirpak http://www.airforce-magazine.com/Pages/default.aspx

aaam wrote:

As I read it, once the button is pushed the FCS automatically delivers the aircraft from a speed < 250knots to a stable hover over a designated (I don't know how) spot at 33m with 1m accuracy and holds it there, which is a remarkable achievement, The pilot can then microcorrect the final position (that's where the 1m comes in) and when ready moves the sidestick forward and holds it until the a/c senses touchdown

Sorry to burts the bubble, but the F-35B has definitely not conducted an automate, i.e. hands-off, vertical landing (at least not yet). That rumour has been floating around for quite a while but, to date, no one has produced a video, photos or any other fanfare over the event. Only the Pratt&Whitney 'higher-ups' seem to think it did....go figure! Even Lockheed-Martin haven't posted anything about this amazing capability.

Whilst the FCS does (or should) prevent the pilot from performing manoeuvres that would depart the aircraft, he/she is in control as far as deceleration and flight path whilst in STOVL configuration. Definitely 'in the loop' all the way from that perspective, but the system is far more stable/controllable as far as positioning is concerned.

Pecker, what photo or video would convince you of that news report at:

http://www.airforce-magazine.com/DRArch ... -Land.aspx

Forum: F-35 Lightning II

Lockheed: Many F-35B landings won’t be vertical