F-35B STO using liftfan

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madrat

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Unread post02 Dec 2017, 14:27

I know there were originally claims that an F-35B was incapable of VTO, that is, vertical takeoff. We now know it is possible to operate the lift-fan for much more than simply on vertical landings. And we know the lift-fan can augment landings to seriously enhance the bring back capacity of the platform. Why is the reverse not also true? A short takeoff is possible at a significant weight limit reduction. Why not enhance short take offs with the lift-fan to enhance maximum weight under that condition?
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blindpilot

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Unread post02 Dec 2017, 16:23

madrat wrote:I know there were originally claims that an F-35B was incapable of VTO, that is, vertical takeoff. We now know it is possible to operate the lift-fan for much more than simply on vertical landings. And we know the lift-fan can augment landings to seriously enhance the bring back capacity of the platform. Why is the reverse not also true? A short takeoff is possible at a significant weight limit reduction. Why not enhance short take offs with the lift-fan to enhance maximum weight under that condition?


????? That's what a short take off is now, and was with the Harrier, and .... ?? "STOVL F-35B." "STO"VL. "S"hort "T"ake "Off. It uses the fan. It was designed that way and it works that way now.

Not sure what your question is?
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steve2267

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Unread post02 Dec 2017, 16:30

Uhh, I am confused by your question.

Are you asking "why doesn't the F-35B use the liftfan during a STO?"

The reason I am confused is because it already does.

Any time the F-35 is in "Mode 4" or "STOVL Mode 4", the F135 exhaust nozzle is canted down some degree, and the liftfan is engaged. How much the nozzle is canted, and how much power is run through the shaft to the liftfan (i.e. how much thrust the liftfan is generating) is all controlled automagically through the flight control software.

Thinking about this some more, I know I've seen the term "Mode 4" in relation to vertical landings. In Mode 4, the flight controls change the way they command the aircraft. In "normal" flying, that is, conventional flying, for example, left/right stick command roll (roll rate, if I remember correctly), whereas in Mode 4, left/right stick control lateral translation to the left (left stick) or the right (right stick). Having said all this, I am unsure if there is a "Mode 3" or "Mode 5" for STO where I think you want your flight controls acting more conventionally. Perhaps Rheo can clear up any of my confusion.

But my point is that the liftfan IS being used during STO.
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010137

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Unread post02 Dec 2017, 16:53

steve2267 wrote:Uhh, I am confused by your question.

Are you asking "why doesn't the F-35B use the liftfan during a STO?"

The reason I am confused is because it already does.

Any time the F-35 is in "Mode 4" or "STOVL Mode 4", the F135 exhaust nozzle is canted down some degree, and the liftfan is engaged. How much the nozzle is canted, and how much power is run through the shaft to the liftfan (i.e. how much thrust the liftfan is generating) is all controlled automagically through the flight control software.

Thinking about this some more, I know I've seen the term "Mode 4" in relation to vertical landings. In Mode 4, the flight controls change the way they command the aircraft. In "normal" flying, that is, conventional flying, for example, left/right stick command roll (roll rate, if I remember correctly), whereas in Mode 4, left/right stick control lateral translation to the left (left stick) or the right (right stick). Having said all this, I am unsure if there is a "Mode 3" or "Mode 5" for STO where I think you want your flight controls acting more conventionally. Perhaps Rheo can clear up any of my confusion.

But my point is that the liftfan IS being used during STO.


Mode 4 simply refers to the configuration the jet is in when it is completely transitioned to stovl with all the doors open and the lift fan completely engaged. Yes, there is a mode 2/3 but we don’t see it in the cockpit, it’s transitional. Same is true as the jet is transitioning back to mode 1 (ctol). The flight controls don’t truly change until you’re completely jetborne around 35-55 kts. You can transition to mode 4 at up to 250 kts and at that point the control laws are traditional. Bottom line, and awesome thing the designers did with the flight controls, is pushing the stick forward always makes you go down, whether in mode 4 (decreases thrust) or mode 1 (stabs down to descend). Throttle fwd always makes you accelerate (nozzle moves in mode 4, simple increase in thrust mode 1) and vice versa.
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rheonomic

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Unread post02 Dec 2017, 17:45

I'll just leave it at the STOVL semijetborne and jetborne modes are really cool.
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Unread post02 Dec 2017, 20:24

Perhaps 'madrat' has viewed too many cartoon videos showing inaccurate STOs from the CVF ski jump which show the F-35B NOT IN STOVL mode and usually (if it can be seen) is in burner. TODALLY RONG. And by the by the oft seen cartoon-like CVF graphic with a JBD is also inaccurate. JBD removed - shown not to be effective whilst restricting T/O flexibility.

Probably 'madrat' has not seen the 'zillion by now' STO real life videos from LHAs from testing and now deck landing quals.

As oft has been quoted on this forum the F-35B is able to launch from the CVF ski jump with a Maximum All Up Weight load (the WOD & Temp not stated whilst loadout is made clear by the RAF in another quote wot we put together nicely).
CVF STO Ski Jump Deck F-35B Sim Details Pilot [Pete Kosogorin BAE test pilot]: “...STO 800 feet with FULL operational load [F-35B CVF off Ski Jump]...”

LIGHTNING STRIKES
winter 2012_13 ETS

“...Onboard the Queen Elizabeth aircraft carriers, the aircraft would take off at its maximum weight of nearly 27 tonnes using a UK-developed ski-jump,...” 2204.62lbs = 1 tonne 59,535lbs = 27 tonnes [Wing Commander Hackett explained]"

Source: http://content.yudu.com/A219ee/ETSWin12 ... ces/20.htm

F-35B Lightning II
Whenever years ago now RAF MoD

"Maximum weapon payload
of 6 Paveway IV,
2 AIM-120C AMRAAM,
2 AIM-132 ASRAAM & a
missionised 25mm gun pod"

Source: http://www.raf.mod.uk/equipment/f35join ... ighter.cfm

Ship Shape — F-35/QEC simulator
SEP 2014 PAUL E EDEN

"300 Take-off run in feet from QEC for lightly loaded F-35B

800 Take-off run in feet from QEC for fully loaded F-35B"

Source: AEROSPACE TESTING INTERNATIONAL September 2014


Jumping Jack Flash
July 2014 unknown author AIR International F-35 Special Edition

“…Two power setting options are available for take-off: Mil STO and Max STO, as Maj Rusnok [USMC] explained: “When you taxi to the tram line you stay in mode one, the conventional flight mode. You convert the aircraft into mode four, the STOVL flight mode, and it takes about 15 seconds or so for the doors to open up and the lift fan to engage….”

FULLER QUOTA BELOWA

"...There are three ways to conduct a short take off (STO) in the F-35B: stick STO, button STO – and auto STO. “That’s a completely automated way to STO the aircraft off the flight deck. You punch in a distance and the aircraft will auto rotate to its optimal fly-out condition. It’s all based on distance: we know where the aircraft is spotted [before it starts its take-off run] and where it should start its actual rotation,” explained Rusnok. “Unlike a Harrier, which launches off the end of the ship flat, the F-35 rotates at about 225 feet from the bow, sits on two wheels until it gets to the end of the ship and actually takes off, a much different process to a Harrier. From a pilot perspective, you lose some sight of the front of the ship; in a Harrier you can see all the deck. But that’s all part of optimising a 35,000lb aeroplane to get off the ship compared to the Harrier, which is only 16,000 to 25,000lb.”

With stick STO the pilot controls the take-off by pulling back on the stick, holding it there and then rotating to the optimal pitch angle to fly off. In button STO, the pilot uses a trim switch which rotates the aircraft when pushed in, activating it when the aircraft passes the yellow STO rotation line positioned 225 feet from the bow of the ship.

“That was a temporary marking applied on the flight deck for this trial and is now being permanently installed on the ship with lighting,” explained Rusnok. “It’s based on optimising the performance of the aircraft and its flying qualities, so we can get the aeroplane off with the maximum amount of nozzle clearance and performance. The STO line is our visual cue to either pull the stick aft or hit the button; or if you’re on automated STO you should start seeing the aeroplane’s flight controls moving by the line, otherwise the pilot can intervene and pull back on the stick. We’ve never had to intervene.”

The pilot also has command of the throttle. Two power setting options are available for take-off: Mil STO and Max STO, as Maj Rusnok explained: “When you taxi to the tram line you stay in mode one, the conventional flight mode. You convert the aircraft into mode four, the STOVL flight mode, and it takes about 15 seconds or so for the doors to open up and the lift fan to engage.

“Then you push the throttle about halfway up the throttle slide into a detent position at about 34% engine thrust request. It sits there and you check the engine gauges: if the readings are okay you slam the throttle to either Mil or Max position and then release the brakes simultaneously. Pushing through to max is like an afterburner detent. But it’s not an afterburner – you can’t go to afterburner in mode four.

“It’s a very fast acceleration. The closest we would spot from the bow is 400 feet, so about 175 feet before we would actually start rotating the aeroplane [at the STO rotation line]; so very, very quick.”

One of the big test points for DT I was to ensure adequate nozzle clearance in all the different test conditions. The engine nozzle swings down and back up during the take-off in accordance with inputs from the aircraft control laws.

“It’s all automated,” said Rusnok. “The pilot is not in the loop whatsoever – either they’re pushing the button and letting the aeroplane do its own thing or pulling back on the stick to help it. Monitoring systems cue when something is wrong, so you have to rely on them to keep you safe because the flight controls are being moved unbelievably quickly.”

Maj Rusnok said the take-off was very much like that ashore, with very little sink off the end of the deck. “The aeroplane is ridiculously powerful in STOVL mode. Just raw, unadulterated power.”..."

Source: AIR International F-35 Special Edition July 2014
Last edited by spazsinbad on 03 Dec 2017, 02:05, edited 6 times in total.
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Unread post02 Dec 2017, 20:48

Yes. Mia Culpa can my part. Only watched A's take off on land and the C on sea trials. I've seen the B landing with the top cover open. I never bothered to look at B takeoffs before asking. It just seemed if SRVL worked for landing then surely an enhanced takeoff should also work.
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Unread post02 Dec 2017, 20:52

Somewhere on the forum IIRC there is a PDF about STOing STUFF (not up to date but enough)....

F-35+STOVLengine&FlightControlSystemPotPourriPP137.pdf

download/file.php?id=23780 (PDF 10.8Mb 137 pages)
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Unread post03 Dec 2017, 05:56

Attached 172 page reprinted PDF (URLs not live but readable) about STOs Short Take Offs & Ski Jumps specific to CVFs.
Blue Sky OPS
26 April 2012 AIR International F-35 Lightning II

"...F-35B Take-off Options
The F-35B STOVL variant has a range of take-off options using different modes to suit the basing. Take-offs from a ship, with either a flat deck or one with a ski jump, are also possible with a mode for each scenario. These are short take-off scenarios that can be achieved at speeds as low as 50kts with a deck or ground run of no more than a 200ft (60m). In the same mode, a take-off as fast as 150 knots is possible if the weight of the aircraft requires that speed. If the aircraft is light it can take off at a slow speed and faster when heavy.

Take-off at speeds as low as 5, 10, 15, 20kts (9, 18, 27 and 36km/h) are also possible, each of which is effectively a vertical take-off while moving forward. There are different ways of rotating the aircraft in STOVL mode, including the usual ‘pull on the stick’. Other ways are by pressing a button or programming a ground distance required after which, the aircraft control law initiates the rotation and selects the ideal angle for climb-out...."

Source: http://militaryrussia.ru/forum/download ... p?id=28256?
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F-35B STO & CVF Ski Jump INFO 30NOV17 PRN pp172.pdf
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geforcerfx

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Unread post04 Dec 2017, 18:43

Wait.... I though the F-35B could do VTO?


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Unread post04 Dec 2017, 19:25

The F-35B can do VTO and it's a part of the spec.. It's just not something that will be used operationally all that often.
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Unread post04 Dec 2017, 20:24

SpudmanWP wrote:The F-35B can do VTO and it's a part of the spec.. It's just not something that will be used operationally all that often.

I remember reading that it can do it, it just can't convert to forward flight from it. Because of this the only usage was to move around short distances (like a few miles at most) in case of swapping ships or air strip damage.

***no Credible sources asking if anyone knows if that's true.
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Unread post04 Dec 2017, 20:39

SpudmanWP wrote:The F-35B can do VTO and it's a part of the spec.. It's just not something that will be used operationally all that often.


I suspect it will be one of those once every five years things, as a low fuel emergency ...
1. where the pilot lands on an LPD deck. They then give it a couple hundred pound of fuel and the LPD sails back over to the LHD for a hop takeoff, and quick landing back home ... followed by an investigation as to whether he melted the LPD deck and new procedures written up for ....

OR.

2. An unusual long range deployment where the refueling probe breaks, and they can't make it to the alternate so he has to land on an AKE supply ship enroute in the area, followed by an investigation, and new procedures for deployments,

OR

3. Over land and low fuel, the plane lands on a parking lot, where they truck fuel to him, for a hop home, followed by an investigation ... well you get the point.

I don't see this as a standard operation. It is an STOVL aircraft, not a VTOL.

MHO,
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Unread post04 Dec 2017, 20:42

https://www.lockheedmartin.com/us/news/ ... -vtol.html

An F-35B test aircraft completes the first-ever vertical takeoff (VTO) at NAS Patuxent River, Md., on May 10, 2013. While not a capability used in combat, VTOs are required for repositioning of the STOVL in environments where a jet could not perform a short takeoff. In these cases, the jet, with a limited amount of fuel, would execute a VTO to travel a short distance.


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Unread post04 Dec 2017, 22:06

Everything I read on the internet is true - especially when written anonymously - but did anyone read this? The 'stupid author' forgot to put in VTO, perhaps these had not been tested when article written April 2012 (I'll check) but whatever.

As per 'SWP' LM VIDEO 10 May 2013 is FIRST VERTICAL TAKE-OFF TEST DATE. :devil: Unknown author I take that back. :doh:
"...Take-off at speeds as low as 5, 10, 15, 20kts (9, 18, 27 and 36km/h) are also possible, each of which is effectively a vertical take-off while moving forward...."
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