Does the F-35 making vertical flight look easy???

Discuss the F-35 Lightning II
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alloycowboy

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Unread post30 May 2013, 04:29

Is one else impressed with how easy and precise the F-35 makes vertical flight and landings look? Check out the one minute mark where the F-35 touches down like a feather.



https://www.youtube.com/watch?v=wFUAFJGH0t0[/b]
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Unread post30 May 2013, 04:45

If the LM video editor had not in the past done a lot of 'slowups and fastdowns' quick editing effects I would not have considered that at the point of 1min 05 secs for the next few seconds it looks to me like the video editor has done a quick 'slowdown' effect. I could be wrong I acknowledge. That is just my impression from the other 'fastup/slowdown' effects on earlier videos. Shame that LM video editor does that.
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Unread post30 May 2013, 14:36

IIRC the F-35B has a WOW sensor that cuts the engine on touchdown for easier landings. it was designed to have a VL be the easiest thing a pilot has ever done.
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Unread post30 May 2013, 21:09

Yes I have no problem with how the VL is carried out - just that the sudden slowdown looks to have been artificially created by the video editor - who in the past has had a habit of making these random 'fast slowdown/speedup' edit effects. As the video is now composed of many random edits some of these also random effects appear. Without understanding completely how a VL is controlled by the pilot - by this I mean can the vertical descent be controlled to the nth degree or is it ultimately controlled to limits imposed by the computer flight controls - the VL descent rate has been tested between 12 to 4 feet per second with an ideal descent rate being 8 feet per second as I recall. There will be a quote to this effect on the forum (which I will find soonish).

I have no problem with pilot reports universally stating that the F-35B is easy to land and it is easy to learn how to do it etc. Yes the engine does shut down automatically when the main wheel WOW (weight on wheel) switch actuates. It has been reported (and disputed) that an F-35B has carried out a completely automatic VL in much the same manner as the VACC Harrier demonstrated the same some 8? years ago now on a UK CVS. I imagine that NOT having JPALS to use today (but will be available in future) makes ordinary use of a completely automatic VL problematic in the same way a completely automatic F-35C (or F-35A on a runway) carrier landing is not possible until the JPALS becomes available. The X-47B demonstrates this completely automatic landing 'JPALS-temporarily made available for X-47B' enabled look doable eh (with 9 touch and go landings aboard CVN-77 recently).

One day I will fly an F-35B physical sim demonstrator and report back. :D Don't hold your breath though. Perhaps a pilot will describe in detail how the F-35B flies in STOVL mode - to the nth degree - one day. The aircraft will stop where it is in the air if the controls are let go in STOVL mode and it can move in small increments subsequently but how smoothly? And can this smoothness be pilot controlled? Dunno.
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Here is the quote I was referring to above and there are other references on this forum here for example: http://www.f-16.net/f-16_forum_viewtopi ... rt-30.html And there will be other references on this forum to same material (search on NORRIS).

Vertical Validation by GUY NORRIS 03 Oct 2011

"...Beesley’s flight in the second F-35B, BF-2, on Jan. 19 [2011] marked the first vertical landing achieved by a non-Harrier-trained pilot. In addition, at least one other pilot in the initial cadre did not have legacy Harrier experience. However Wilson says ab initio conversion training for hovering and vertical-landing qualification took as little as half a day, compared to “at least” three times that for the Harrier.

Speaking at the Society of Experimental Test Pilots symposium in Anaheim, Calif., last month, Wilson said results vindicate the simple design concept of the “unified” Stovl control mode. The mode is activated by the push of a “decelerate-to-hover” button in which the throttle commands acceleration and deceleration in the hover. In this mode, the stick commands upward/downward vertical velocity with a backward-forward motion, while in the hover mode sideways movement of the stick commands bank angle. If released, it returns the aircraft to wings level. Pedals command yaw rate in the hover.

The fastest descent rate, as controlled by pushing the stick forward, is set at 7 fps., though the testing has included rates as low as 4 fps. and high as 12 fps.

Testing has also focused on the translational rate command (TRC) mode, which in the hover allows the pilot to make small positional corrections and which brings the aircraft to a standstill if the pilot releases the controls. “It is used to capture the current longitudinal groundspeed and is important for precise positioning in shipboard operations,” says Wilson...."

Aviation Week & Space Technology; October 3, 2011; pages 31-32
OR
http://ehis.ebscohost.com/ehost/detail? ... N=67279269
OR
http://ehis.ebscohost.com/ehost/detail? ... N=67279269
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lamoey

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Unread post31 May 2013, 00:09

alloycowboy wrote:Is one else impressed with how easy and precise the F-35 makes vertical flight and landings look? Check out the one minute mark where the F-35 touches down like a feather.



https://www.youtube.com/watch?v=wFUAFJGH0t0[/b]


Spaz is 100% correct that this is the film editor making it look super smooth. Look at the video of the first vertical take-off, which look unedited for smoothness.

http://www.youtube.com/watch?v=zW28Mb1YvwY
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Unread post31 May 2013, 00:52

spazsinbad wrote:Yes I have no problem with how the VL is carried out - just that the sudden slowdown looks to have been artificially created by the video editor - who in the past has had a habit of making these random 'fast slowdown/speedup' edit effects. As the video is now composed of many random edits some of these also random effects appear. Without understanding completely how a VL is controlled by the pilot - by this I mean can the vertical descent be controlled to the nth degree or is it ultimately controlled to limits imposed by the computer flight controls - the VL descent rate has been tested between 12 to 4 feet per second with an ideal descent rate being 8 feet per second as I recall. There will be a quote to this effect on the forum (which I will find soonish).

I have no problem with pilot reports universally stating that the F-35B is easy to land and it is easy to learn how to do it etc. Yes the engine does shut down automatically when the main wheel WOW (weight on wheel) switch actuates. It has been reported (and disputed) that an F-35B has carried out a completely automatic VL in much the same manner as the VACC Harrier demonstrated the same some 8? years ago now on a UK CVS. I imagine that NOT having JPALS to use today (but will be available in future) makes ordinary use of a completely automatic VL problematic in the same way a completely automatic F-35C (or F-35A on a runway) carrier landing is not possible until the JPALS becomes available. The X-47B demonstrates this completely automatic landing 'JPALS-temporarily made available for X-47B' enabled look doable eh (with 9 touch and go landings aboard CVN-77 recently).

One day I will fly an F-35B physical sim demonstrator and report back. :D Don't hold your breath though. Perhaps a pilot will describe in detail how the F-35B flies in STOVL mode - to the nth degree - one day. The aircraft will stop where it is in the air if the controls are let go in STOVL mode and it can move in small increments subsequently but how smoothly? And can this smoothness be pilot controlled? Dunno.
________________

Here is the quote I was referring to above and there are other references on this forum here for example: http://www.f-16.net/f-16_forum_viewtopi ... rt-30.html And there will be other references on this forum to same material (search on NORRIS).

Vertical Validation by GUY NORRIS 03 Oct 2011

"...Beesley’s flight in the second F-35B, BF-2, on Jan. 19 [2011] marked the first vertical landing achieved by a non-Harrier-trained pilot. In addition, at least one other pilot in the initial cadre did not have legacy Harrier experience. However Wilson says ab initio conversion training for hovering and vertical-landing qualification took as little as half a day, compared to “at least” three times that for the Harrier.

Speaking at the Society of Experimental Test Pilots symposium in Anaheim, Calif., last month, Wilson said results vindicate the simple design concept of the “unified” Stovl control mode. The mode is activated by the push of a “decelerate-to-hover” button in which the throttle commands acceleration and deceleration in the hover. In this mode, the stick commands upward/downward vertical velocity with a backward-forward motion, while in the hover mode sideways movement of the stick commands bank angle. If released, it returns the aircraft to wings level. Pedals command yaw rate in the hover.

The fastest descent rate, as controlled by pushing the stick forward, is set at 7 fps., though the testing has included rates as low as 4 fps. and high as 12 fps.

Testing has also focused on the translational rate command (TRC) mode, which in the hover allows the pilot to make small positional corrections and which brings the aircraft to a standstill if the pilot releases the controls. “It is used to capture the current longitudinal groundspeed and is important for precise positioning in shipboard operations,” says Wilson...."

Aviation Week & Space Technology; October 3, 2011; pages 31-32
OR
http://ehis.ebscohost.com/ehost/detail? ... N=67279269
OR
http://ehis.ebscohost.com/ehost/detail? ... N=67279269


A few notes --

The VL at the time mark noted was edited -- as Spaz suggests.

One's right hand controls movement in the Z axis whilst in the hover. 7 fps is the standard rate of descent for landing and is commanded/controlled by moving the right inceptor forward to the "soft" stop. If one wants less rate of descent, one does not push the right inceptor (ie the side stick) as far forward as one might do for the standard RoD. If one wants more RoD, then one pushes the stick past the soft stop. If you relax forward pressure on the stick allowing it to return to the null/neutral position, you will command the propulsion system to zero fps RoD. Wanna go back up? Just pull on the stick. Corrections for lateral movement (line up) during the descent are made by moving the stick right or left. It's that simple.

What Gus meant to say was that the propulsion system goes to idle with wow.

Rumors of a hands-off VL are true.
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Unread post31 May 2013, 00:57

Thanks 'quicksilver', also the VL F-35B does not want to hover in the 'ground effect' but wants to get through any potential adverse effects (during VL) to get a good precise touchdown. On a ship the TD point on deck is important. No need to mess about doing an unnecessarily gentle landing. One has a spot to land on and land on it you shall. :D Remember the flat deck may be doing many movements (in six degrees of freedom) so it is best to get there promptly; and of course, before the fuel runs out.
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Unread post31 May 2013, 01:09

Does the pilot need to account for wind direction during a VL? .. don't see a tiny wind vane perched on the jet's nose..
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Unread post31 May 2013, 01:16

AFAIK - that wind direction is not so important as it is FOR SURE in the Harrier VL. That big Harrier wind vane is there prominently for good effect during necessarily 'into the wind' Harrier VLs. I have read that the F-35B incept computer flight controls for STOVL work make auto adjustments for adverse conditions - up to a limit of course. So and 'out of wind' vertical landings - within the known limits - will be fine. The F-35B flight controls are constantly adjusting to keep the aircraft safe - within limits - and to prevent the pilot from requiring some unsafe control input. Apparently these computer controls can be overridden - but who wants to do that? Get really fouled up and you will be automatically ejected anyway! :D Not a nice way to end a sortie.

I think I have read that the second/third USS Wasp testing will discover more about VL wind limits with operationally significant loads etc.

The bit of earlier info about the F-35B being able to go backwards at 30 Knots I think also mentions that this flexibility will allow the flat deck to steam NOT into the wind - up to whatever the limit might be - so as to give the ship a lot of flexibility for what she will be doing during a VL by the F-35B. Unlike conventional carrier landings which require some semblance of steaming into the wind - unless some odd weather conditions prevail. The unpredictable flight ops course for VLs will make sub tracking solutions that much more difficult. One hopes anyways. :roll:
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Unread post31 May 2013, 01:47

popcorn wrote:Does the pilot need to account for wind direction during a VL? .. don't see a tiny wind vane perched on the jet's nose..


Short answer is yes.

However, the wind vane on the Harrier is used principally (and most importantly) for transition flight to/from wing-borne to jet-borne flight or vice versa. Its primary indicating function is sideslip. Zeroing, or at least minimizing, sideslip is how Harrier pilots avoid being headliners at fundraisers for their wives and children.

In Harrier, sideslip in transition flight can generate rolling moments that the flight control system doesn't have the bandwidth to overcome. Easy prevention? Zero the sideslip (ie keep the vane centered). 'Centered vane' does not necessarily translate to 'into the wind'. Below 30 knots it doesn't much matter where the vane is if the winds are light, but handling qualities are always better with the nose into the wind. On the ship, that's not always an option.

In Harrier, one centers the vane with one's feet. Would be same in F-35B if it had one -- it does not (in the production form). Big difference is that when one makes a rudder pedal input in F-35B, he or she is redirecting~18Klbs of thrust for effect; in Harrier rudder pedal input opens the yaw puffer on the tail boom and moves the rudder surface -- to far less effect.

Lotsa other differences (like sideslip doesn't create the same concerns in F-35 as it does in Harrier) but I don't wanna rewrite the manual... 8)
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Unread post31 May 2013, 03:01

Probably some of these quotes will mimic what may be in the F-35B manual (NATOPS) but that is only my guesswork. Go here [ http://www.f-16.net/f-16_forum_viewtopi ... eslip.html ] with a bit of that page repeated here. Other threads have more including graphics so search on 'Farley'. "UNIFIED" is the method/way the F-35B is controlled by flight computers. Searching forum on 'Tomlinson' will find heaps more etc.

Excerpt from : A V/STOL FLIGHT CONTROL JOURNEY ENABLED BY RAE SCIENTISTS John Farley c.2006

"ANNEX – CONTROL LAW RESEARCH USING THE VAAC HARRIER by John Farley c.2006
Two decades ago the controversial aspects of the Unified law were well appreciated by the VAAC team. This led them to thoroughly flight test various other concepts. By 1999 they were left with three serious contenders: Unified, Mode Change and Fusion.

UNIFIED. Unified was the most radical mode. Here the pilot pulls back on the stick to go up and pushes to go down, regardless of airspeed. At all speeds above 40 kt ground speed the stick commands flight path rate and so relaxing it to the centre position when the aircraft is flying level maintains height. If the aircraft is in a climb or a dive, relaxing the stick maintains the existing climb or dive flight path angle. As the aircraft decelerates through 40 kt the stick response blends to become a height rate control by 30 kt ground speed so, in the hover, with stick centre commanding zero height rate, it appears to the pilot as a height hold.

When flying up and away lateral stick commands roll rate. This blends between 130 and 100 kt to become a closed loop roll attitude control, so that relaxing the stick to centre below 100 kt commands wings level. Above 40 kt ground speed the rudder pedals command sideslip. Decelerating below this speed the pedals blend to a yaw rate command by 30 kt, providing a heading hold in the hover with feet central.

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.

In summary, if the pilot centres both the stick and throttle when flying on the wings, the aircraft holds the existing speed, bank attitude and climb or dive angle. In the hover, centralising everything maintains the existing hover height, position and heading. Such hover characteristics are the stuff of dreams for every Harrier pilot at the start of their conversion although, as discussed earlier, many experienced Harrier pilots were critical of Unified...."

http://www.rafmuseum.org.uk.nyud.net/do ... -Story.pdf (26Mb)
_____________________

Test Flying The Joint Strike Fighter by Graham Tomlinson 17 Jun 2011
"...The STOVL mode control system is derived from ‘Unified’ developed by the ‘RAE’ on the VAAC Harrier. The throttle commands acceleration and deceleration (or thrust on the ground and in the STO mode, and in all conventional modes); in the hover the stick moved backwards/forwards commands upwards/downwards vertical velocity (or pitch rate elsewhere); in the hover the stick moved from side to side commands bank angle (or roll rate elsewhere) and if released returns the aircraft to wings level; in the hover the pedals command yaw rate (or sideslip elsewhere).

Future development will clear full envelope autopilot/auto throttle, automatic deceleration to a spot, and TRC (translational rate command) which in the hover allows the pilot to make small positional corrections easily, and will then bring the aircraft to a standstill if the pilot releases the controls....

...In the Harrier the pilot must obey the rules. The F-35B flyby-wire system gives angle-of-attack and sideslip control, and departure protection. Further pilot workload reduction is given by performance deficit protection, conversion speed window protection and FOD protection warning;... ...Pilot cognitive errors (of trying to control thrust with the throttle) have been mitigated in the design...."

http://myweb.tiscali.co.uk/hawkerassoci ... ghter.html
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Unread post19 Sep 2013, 06:58

I'll keep me eyes peeled for the video whenever released...

"...This autumn will see a futher two Flight Test Group organised lectures, the first of which taking place on September 19th, ‘Revolutionising STOVL Flight Control for the Joint Strike Fighter‘, will describe the flight tests conducted on the Harrier, how and why the evaluation was set up as it was, and the results achieved...."

http://media.aerosociety.com/news/2013/ ... iety/9497/

Flight Test Group Lecture
REVOLUTIONISING STOVL FLIGHT CONTROL FOR THE JOINT STRIKE FIGHTER
JUSTIN PAINES, CHIEF FLYING INSTRUCTOR - FIXED WING, EMPIRE TEST PILOTS’ SCHOOL
LONDON / 19 SEPTEMBER 2013
"The Harrier was one of the most iconic aircraft in RAF and RN service, but it’s unique capabilities came at a price in the complexity of the piloting task. As a result, a number of research programmes in the US and UK sought to simplify STOVL flight control for the next generation of STOVL aircraft.

The debate was complicated by the US research effort taking a strong different line to the UK effort, which was pioneered at RAE Bedford, and the resulting transatlantic impasse threatened to leave the Joint Strike Fighter programme with no clear direction on how to improve the Harrier’s complex piloting task. As a result, the UK research effort took a step back, implementing a variety of concepts for international evaluation by a mixed team of Harrier and non-Harrier experienced pilots, using the UK’s Vectored-thrust Aircraft Advanced Control (VAAC) Harrier.

The challenges in conducting the flight test were matched only by the challenges of what continued to be a heated and emotional debate between the research teams. Pilot opinion was deeply divided and based strongly on prior experience and apriori opinion. A seemingly endlessly controversial topic that could only be solved by hard data, led ultimately to a decision to adopt the preferred UK strategy.

This lecture will describe the flight test conducted, how and why the evaluation was set up as it was, and the results achieved. But it will also chronicle one of the most controversial and revolutionary decisions in flight control history. With the benefit of hindsight, the F-35 well into flight test and many pilots now operating in STOVL mode, the lecture will also look at the question “Were we right”?

Justin Paines entered the RAF in January 1988, joining the Harrier force in 1990. After a long tour on No 1 (Fighter) Squadron, including operational duties over northern Iraq, he completed Test Pilot School at Edwards Air Force Base, flying all the main US fighter types and several historic aircraft over that year. He joined Boscombe Down as a Test Pilot on the experimental (VAAC) Harrier programme and also flew test programmes in Harrier GR7 and T-10, Hawk and Tucano aircraft. He returned to the US to join the Joint Strike Fighter programme and flew the X35 A, B and C experimental aircraft.

After a tour as an Instructor on ETPS, he left the RAF and joined QinetiQ, once again flying the VAAC Harrier programme, developing advanced control concepts for the F-35B STOLV aircraft, and innovative landing technologies for Queen Elizabeth class aircraft carriers.

Justin rejoined ETPS in 2009, where he now serves as Chief Flying Instructor (Fixed Wing)."

http://aerosociety.com/Assets/Docs/Even ... ecture.pdf (100Kb)
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popcorn

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Unread post19 Sep 2013, 08:12

Anyone know how many seconds it takes to do one pirouette?
I recall the short F-35B clip in the video the Navy released some time back and it showed the jet pirouetting like Baryshnikov :lol:

OK, I exagerate a bit but it was really impressive... but now I'm having second thoughts and maybe a little video editing was involved.
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Unread post19 Sep 2013, 09:26

Yes I know the video and have looked for it a number of times unsuccessfully. I thought it was one of the year roundup videos for pax, maybe 2011, but can't find it.
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Unread post19 Sep 2013, 09:29

It was a very short clip within the montage part towards the end of the video
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