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F-35 Cancelled, then what ?

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F-35 Cancelled, then what ?

Old 23rd Jun 2015, 12:11
  #6321 (permalink)  
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Handy for take-off on runway 04; but a bit of a bummer on finals for runway 22......
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Old 23rd Jun 2015, 12:24
  #6322 (permalink)  
 
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Unless you match your approach angle to the ramp. It flares for you.
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Old 23rd Jun 2015, 12:30
  #6323 (permalink)  
 
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Originally Posted by John Farley View Post
Incidentally, if you look at any video of a B flat deck takeoff and watch the tailplane activity crossing the end and compare that with the tailplane activity off the ski-jump you will notice that even modern flight control systems find life easier from a ramp.
True but the engine side of the control system on the B is working pretty hard - just look at the thrust vectoring nozzle dancing around.
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Old 23rd Jun 2015, 12:41
  #6324 (permalink)  
 
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Really, JTO? In the clip that Engines posted? Not sure I can see any movement. Or are you talking flat take offs?
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Old 23rd Jun 2015, 12:50
  #6325 (permalink)  
 
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Yep, visible in that clip on the first take-off.
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Old 23rd Jun 2015, 13:04
  #6326 (permalink)  
 
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the engine side of the control system on the B is working pretty hard - just look at the thrust vectoring nozzle dancing around
Not dancing around, more puckering prior to piloting
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Old 23rd Jun 2015, 13:37
  #6327 (permalink)  
 
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I wonder why the US Navy and USMC have studiously avoided any form of ramp for their amphibious carriers. I've read several reasons such as a ramp affects the ships handing or the loss of deck space is unacceptable etc. Surely some bright spark could come up with a portable ramp that can be dropped/moved once the Harriers/F-35s have launched?
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Old 23rd Jun 2015, 13:50
  #6328 (permalink)  
 
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I thought the USMC had decided that ops from the smaller decks were to be VTO and VL - not much room for anything else. Where there's space, the flat TO is fine. USN will have proper carriers and no need for ramps.

The snag with a demountable ramp may be the fact that it's curved. If you could lower it, you'd be left with a big dip in the deck. And what would you do with that deck space if it's going to be needed again for the next launch. Mind you, International Rescue had a retractable ramp for Thunderbird 2, so it must be possible.
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Old 23rd Jun 2015, 14:26
  #6329 (permalink)  
 
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Good to see an F35B taking off in a very easy looking way from a ramp, it proves that the software can support taking off on a ramp, a positive move forward.

Courtney you could always have your ramp supported by jacks so that it can be a ramp for F35s and a flat deck from MV 22s...
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Old 23rd Jun 2015, 14:39
  #6330 (permalink)  
 
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Courtney, Dat, JTO, DD,

Perhaps I can help out a bit here. What I can't do is improve on JF's succinct and 'spot on' comments about ski jump takeoffs. They are, by some distance, the lowest workload way of getting a combat jet into the air. The flat STO presented many more challenges to the F-35B team, and the lack of aft control surface movement shows how straightforward the evolution is.

However, it's a lot more than 'straightforward'. It's a little surprising, given that this is a pilots' forum, how few people mention the significant advantages it delivers. Firstly, operational: the ski jump will allow the F-35B to launch on task with at least another ton and a half of fuel and/or weapons. That's a ton (or two) of pure military goodness. Secondly, safety. As JF points out, the aircraft leaves the jump nose up and climbing without the pilot having to do anything. If anything does go wrong, the pilot has many more precious seconds to dump stores/jump out. At night, or in bad weather, or from a pitching deck, that's also a lot of goodness.

I do understand why some posters think this looks like a 'pucker' heavy evolution, but it's really, honestly, not. Every Harrier pilot I worked with said that it was a complete non-event. What's really amazing is that these gains come without penalty to the aircraft, which is fairly rare. The Harrier needed no mods to do ski jumps, save extra servicing checks on the nose leg. The F-35B has needed none. The flat deck STO drove the design, the ski jump came basically free.

Oh, and don't forget that it's another brilliantly simple and effective naval aviation idea from the UK's Fleet Air Arm. Respect.

JTO: Yes, the aft nozzle is definitely moving. I am not familiar these days with the F-35B control laws. but I would guess that what is happening here is that the aft nozzle is being left as far 'up' as possible to get to ramp exit speed in the shortest time (and distance), then programmed 'down' after ramp exit to support the 'fly away' profile. The Harrier did this manually, with the pilot selecting nozzles down to an adjustable 'STO stop' as it neared the ramp exit. F-35B does this for him/her.

For those that might not be familiar with the way a ski jump STO works, the key thing to 'get' is that the aircraft leaves the ramp BELOW flying speed. So the rate of climb starts to decay after ramp exit, depending on how much wing lift and jet lift is being provided. However, the aircraft is still climbing. As it accelerates, wing lift increases and jet lift can be reduced by altering the angle of the propulsion system's nozzles. At some point after ramp exit, the aircraft reaches an 'inflexion point', and the rate of climb starts to increase again. That distance between the end of the ramp and the 'inflexion point' is essentially a 'free runway in the sky' - around 1 to 1.5 km, depending on launch weight, temperature and other factors. That 'free runway' delivers the payload improvement.

The UK legacy performance limit for Harrier ski jump STOs was a minimum ROC of 400 feet per minute at the 'inflexion point'. Other nations have different limits.

A powered lift aircraft can 'schedule' (adjust) wing and jet lift so as to maximise the payload that can be delivered from the ramp. It can also be controlled well below wing borne flying speeds. Unfortunately, conventional aircraft can't do either of these. They have to launch at a speed at which they can fly controllably on wing lift alone. Their only option (with all thrust already applied) to arrest ROC decay is to apply more pitch, which increases drag, which slows the aircraft, which.....you probably get the picture. That's why the STOBAR option, being used by the Chinese and others, is, in my view, always going to be severely limited in effective payload.

Good questions on USN/USMC non-use of the ramp. The answer I always got was that the operational concept for the 'Gators' was a mixed air wing, with the requirement to carry out mass helicopter launches driving the flight deck layout. I know for a fact that many USMC aviators would love to have a ramp for F-35B. They aren't at all hard to fit, and ship handling wasn't affected. The loss of the most forward spot was not a problem for the UK - in any case, trying to operates helicopters from '1 Spot' in anything more than light airs was, in my experience, a bit of a mare. However, I gladly cede to the USMC, who know what they want.

However, there is no doubt that for a given deck (or say, a short expeditionary runway) a ski jump gives improved combat efficiency plus safer operations.

It's interesting that with the advent of the MV-22, short rolling takeoffs (STOs) are being considered as a standard shipboard operating procedure. Perhaps they could use a ramp as well?

Hope this lot of drivel helps - I'm always happy if it fills in any (quite understandable) gaps in some posters' knowledge. After all, that's what a 'forum' is supposed to do.

LO, I hope this isn't a 'meme' - whatever that is.

Best regards as ever to the clever folk who think up this sort of stuff,

Engines

Last edited by Engines; 23rd Jun 2015 at 14:42. Reason: Text changes
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Old 23rd Jun 2015, 15:39
  #6331 (permalink)  
 
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Engines,

Does that change in aft nozzle position account for the slight upwards pitch of the nose just after the a/c goes off the ramp?
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Old 23rd Jun 2015, 16:09
  #6332 (permalink)  

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Dave

Perhaps the pilot even forgot himself and interfered in order to exactly perfect the AOA for climb out......
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Old 23rd Jun 2015, 16:17
  #6333 (permalink)  
 
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Dav,

I honestly don't know. However, my best guess (but warning - this IS a guess) is that the aircraft flight controls are designed to get the aircraft to the optimum pitch angle as soon as possible after launch for the 'fly away' - this is a fairly low speed launch, I'd guess (again) at relatively low weight, so the exit speed will be low, giving a low pitch rate at exit.

My guess, therefore, is that what you have noted is the flight control system 'capturing' the aircraft pitch angle - as I understand it, the pilot has no direct control over pitch angle in the powered lift mode - this is all controlled by the computers. However, the pitch angle would be driven by the desired flight path commanded by the pilot.

At no time will I presume to know more than a hundredth of what John Farley knows, though.

Best Regards to all,

Engines

Last edited by Engines; 23rd Jun 2015 at 16:17. Reason: Edit
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Old 23rd Jun 2015, 16:46
  #6334 (permalink)  
 
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Thanks, Engines. An excellent post as always. Yes I do understand the advantages of a ramp, some of my stuff here was a bit flippant. In fact there are even more advantages than you mention. One of the few things I recall from Officer Training was a five minute lecture given by one of my classmates explaining the vectors involved. I recall it was the five minute talk that delayed the whole day because of the interest and questions it provoked. That makes me an expert, by the way

As our previous generation of through deck cruisers clearly demonstrated, it is the way forward. And now, no one can argue that F-35 cannot do it.
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Old 23rd Jun 2015, 16:55
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hey - a ski jump at last

Now all they have to do is prove the heavier AUW take offs and the hundred other serious problems with the aircraft and it will be a winner LOL
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Old 23rd Jun 2015, 19:30
  #6336 (permalink)  
 
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Nice video footage.

Well done to the Pax folks and all the people working long hours getting through these test points. BZ!
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Old 23rd Jun 2015, 20:33
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NOted by BAESYSTEMS that the pilot was Peter Wilson:

https://www.youtube.com/watch?v=P5LdkPaERhI
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Old 23rd Jun 2015, 21:50
  #6338 (permalink)  
 
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Originally Posted by dat581 View Post
I wonder why the US Navy and USMC have studiously avoided any form of ramp for their amphibious carriers. I've read several reasons such as a ramp affects the ships handing or the loss of deck space is unacceptable etc. Surely some bright spark could come up with a portable ramp that can be dropped/moved once the Harriers/F-35s have launched?


Because the 30+ m of ramp doesn't just lose number 1 spot, it hems in the aircraft deck park forward, see phot for details. On a ship with 33m beam at the flightdeck, losing half that forward for a ramp means chaos for the handlers.

A moveable ramp that'll support a 25te cab with an entry speed of 80kts or so and remain reliable and bug-free when subjected to salt-water, being goffered, and little or no maintenance will not be cheap or simple.
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Old 23rd Jun 2015, 22:54
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Originally Posted by evansb
Such a complex and expensive solution to such a primitive question, i.e. to blow up the enemy. Such a curious, insatiable and violent species we humans are. Oh well..
Oh, thank God you came here and commented. Now you've said that I feel terrible about my military past. I must recant. Wait, what am I going on a Military Aviation site?

Oh thank you Evans for saving me.
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Old 24th Jun 2015, 03:12
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It's ok CM, perhaps it'll make him feel better when someone uses one of those complex and expensive solutions to prevent him from being blown up..
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