LR - Attempting a ski-jump without the "bin lid" (or '57 Chevy hood, as it is known in these parts) open would be rapidly followed by a landing in the style of that great "Lockheed Martin legacy" product, the F2Y Sea Dart.

The drag factor from the bin lid may not be as scary as it looks. With the 20 megawatt garbage disposal on full blast, the airflow in that region is going anywhere but straight aft.

Just checking chaps - some dodgy ex navy guy told me it was going to be launched with the bin lid shut ... after all the russkies do it :)

Was it S*****y W**d?

The Russky aircraft in question have respectably sized wings, not sawn-off penguin-like appendages bolted to the side of a brick-like body.

LR and others,

Perhaps this post might help sort out fact from invective on ski jump stuff.

Ski jumps can be used by both conventional and powered lift (STOVL) aircraft. In both cases, they launch the aircraft into the air below its normal takeoff speed, and the aircraft then spends a period of time in a reducing rate of climb while it accelerates to full wing borne flight, and then climbs away. It's been described to me as a 'runway in the sky'.

However, the two types get very different levels of advantage.

A conventional aircraft (e.g. Flanker, or Fulcrum as used by Chinese and Russia) cannot be launched below normal takeoff speed at max gross TO weight (MGTOW), as the only way they can maintain a safe minimum rate of climb is to adopt a high angle of attack and use engine thrust as best they can. That creates more drag, which delays acceleration, which means lower rate of climb away from the sea. This is why you don't see these aircraft launch with many external stores, and it helps explain an unusually public complaint by a Chinese Navy Admiral over the poor performance of his aircraft.

Conventional ski jumps aren't new, but have usually been discarded due to the inherent limitations I've summarised above.

A STOVL aircraft can launch at much higher relative weights, because it can vector its thrust to the optimum angle to support the aircraft by a combination of wing lift and powered lift so as to deliver the required acceleration and climb out. The angle will be scheduled after launch to move aft as wing lift builds. (Of note, the UK sets a minimum 400 fpm rate of climb as the limiting performance measure for ski jump launches).

Ski jump launch is an extremely effective system for maritime STOVL aircraft, is low workload and safe, as the pilot is guaranteed to be climbing away from the sea, and has more time to react in the event of an engine failure. It also delivers a large improvement in launch weight compared with a flat deck STO.

Oh, and the ski jump was a Royal Navy invention. And the F-35B lift system integration and flight controls design was led by some amazingly talented Brits. And Brits are leading the STOVL flight testing.

I know that there are plenty of folks here who disparage the STOVL variant, and it's technology. It's a free forum, and they can do so as much as they like. But it's a shame that it sometimes prevents very smart and hard working people getting the credit they deserve. Perhaps this post will help restore a bit of balance.

Best regards as ever to all those doing the hard work and bashing out the hard miles

Engines

Really Whiteovies? Happy to be corrected but I believe the jumps at Yeovilton and Wittering are still in place. A quick search of google and bing map overhead views still shows them there, but I am not sure of the date of the pictures. Were they torn down?

Engines is correct. Ski-jump is synergistic with STOVL - partly because of powered lift and partly because a STOVL aircraft has not only lift, but also control below its wingborne flying speed.

But to get back to the "bin lid" point: A Harrier-type STO has a certain elegance in that you start the roll with 100 per cent thrust straight aft and can then quickly and smoothly dial in any amount of vectoring. The F-35 is a bit more restrictive in that the aft nozzle is delivering part thrust for acceleration (because the lift fan and roll posts are active), the lift fan vectors to 45 deg only and the roll posts (9000 lb thrust) do not vector aft at all.

Luckily the F135 is a :mad:ing big engine...

Thanks again 'Engines' your point about "...And the F-35B lift system integration and flight controls design was led by some amazingly talented Brits...." always amazes me how all this innovation by youse Brits is not acknowledged here. I guess this is not a British forum eh. Just crabs scuttling about. :}

Guys,

Just thought it might be helpful if I made a further post on this STOVL ski jump stuff.

LO is quite right in that the powered lift system on the F-35B can't vector all the thrust aft like the Harrier does. That's part of the trade off in getting your main propulsion engine located at the rear of the aircraft, where it really belongs for a fighter/strike type aircraft.

The lift fan can vector aft to around 50 degrees: on the X-35 there was a sort of 'pram hood' device that gave further aft vectoring - however, this was replaced in development by a much lighter 'vane box' device (UK designed) which still gave enough aft vector to meet the requirements. These were a set distance for a flat deck STO, and another shorter distance for a ski jump launch. The launch weight was driven by a defined operational scenario. J

The roll posts deliver around 2000 pounds thrust each in balanced operation, but they are turned off during the STO run and switched back on just before launch. This facility was suggested by a very talented RN FAA air engineer, and gratefully adopted during the weight saving programme. Another excellent Brit contribution.

The point overall is that the F-35B meets all its STO requirements, as well as its short landing targets. And it's a much heftier bird than the Harrier - over 55000 pounds off the ramp.

Happy to keep this sort of stuff coming as long as it helps. Do let.me know when I start boring people.

Best regards as ever to young and talented navy aircraft engineers

Engines

Ski Jump optimisation
 

Is a ski jump a ski jump or for optimal launch weight at a standard wind over deck and pressure, is the geometry different for a Harrier and an F35?

I suppose the subsidiary question is there a plan to build an appropriate ski jump at Marham?

San Diego,

Yeovilton's has certainly gone but I may be wrong about Wittering, I've not been there for a few years. Unfortunately I'm not based in that part of the Country these days.

Something Engines hasn't mentioned in his excellent posts is that because of the UKs involvement in F-35B the flight control software has always been written with a ski-jump take-off in mind. It is not something to be newly coded and loaded into the aircraft.

Geometry is no different for the new carriers in that a 12 degree ramp was fitted to CVS and is fitted to Queen Elizabeth. The difference is that the QE ski jump is longer and less abrupt.

Not sure about putting one at Marham. I think some people are still struggling to think of 617 Sqn having to go to sea :p

Engines,

I presume that the lift-fan stays static and the vanes move to direct the thrust? Can the vanes go past 90 deg and act as a brake?

I am certainly not taking a swipe at the extremely talented brits slaving away on the F35b although I might be a little jealous of their salary :)

I do know some of them :)

The trouble is - the whole thing is being done kind of ar5e about face,the carrier is in build and can only be built with a ski jump now (no possibility of cats and traps) and yet the a/c still has not completed a land based ski jump take off !
Just seems a dumb way of going about things LOL It is usually more sensible to trial things before committing to production !

I am never taking a swipe at our engineers/pilots btw - we always have to cope with the mess left by politicians and top management.

Thanks for the info Engines,much appreciated and I hope you understand that I am not taking a swipe at the people involved - just the concept and the unfortunate way that it has all panned out.

rgds LR

F35 to display in the UK this year.
 

LR and others

Yes, the lift fan is fixed and the vane box can deflect the thrust forward of the vertical. Used to help decelerate the aircraft to the hover as well as other things.

LR, in truth the programme isn't doing things 'ar5e about face' nor are things being done in a 'dumb' way.

The ship and the aircraft have proceeded side by side for many years now. At meetings in 2003, the CVF team were demanding a ski jump profile from LM. That profile wasn't available then, but was provided around 2006/7 once the F-35 team had done enough sim work on ski jumps with mature flight control models.

The thing to grasp is that ski jump ops are a low risk area of the F-35B programme. Ski jump launch is not as 'dynamic' as a flat deck STO, and in some areas the F-35B offers less challenges than the Harrier.

What was definitely 'dumb', in my view ( others can disagree) was the UK MoD's two year game of 'F-35 variant hokey-cokey'. Swapping from B to C and back again disrupted the STOVL test programme and, I think, made the UK look less than professional.

The fact is that the programme is where it is, and many people are working hard and cleverly to make it a success. Lots of them are Brits, who find it a little difficult to understand why so many people spend so much time and effort talking the project down.

It's a free country, and a free forum, as I've said many times. Post whatever you like. Just make it accurate and factual.

Best regards to absolutely everyone

Engines

I would not disagree too much with that statement except it must be remembered that the carriers had been 'sold' to us as completeable (new word :)) as either a ski jump carrier or a conventional carrier with cats n traps but of course the reality was a little more er complicated than that...it usually is when wastospace and politicians are involved !

Glad to hear it - wouldnt be surprised if somebody had said that about the tailhook on the 'C' ; )

rgds LR

If it is coming to the UK....note for COS.
 

1.Put it on static display (as a minimum) at both RN Air Stations when they have their Air Days (if they still are or do). That alone will put thousands on the attendance (and money in someone's pocket needy pocket other than....
2. You've got to sell this hard. The public are becoming jittery about the UK defences overall military ability. They need to see something positive that is being bought in their name for their defence.
3. Need to back this up with the public to see and meet the people who will be flying, maintaining and operating this aircraft. Show off the best young Naval people.
4. Spin it, spin it and spin it.


And if you have any balls... invite the Russians over to the same party and let them show off their latest hardware.
* If its too late to do this this year then do it next year, but do something.

Perhaps not, since it will give an opportunity for the daft old story of it being conceptually a Yak-141 (FREESTYLE) knock-off being dredged up yet again......

EVERYTHING I saw in the run-up to the "main gate" decision on 25th July 2007 to go ahead with the CVF program said "to be built as STOVL with a ski jump, but convertible as part of their mid-life refit to catapult & trap operation".


I never once saw anything from the UK government or BAE that either said or implied that the switch was supposed to be possible during construction, until the 2010 SDSR came out.


Could you point us to where it was said otherwise before the 2010 SDSR?

If memory serves the 'convertible' carrier was the original 300m and then 290m designs. The government then insisted on more budget cuts and forced a redesign to a smaller version, they then realised that that smaller craft had a poor sortie rate so forced another redesign up to the current 280m version. Along the way the ability to change launch systems was dropped which the government OK'd as it saved a few pennies.

So in brief, various governments introduced years of delays and cost increases due to constant re-design and engineering work while going about trying to save money in some of the most stupid ways possible.

At the height of the nonsense when the press and public was questioning what was going on the government of the day conviently forget it was them who changed the design brief and agreed to the dropping of various features.

Sandiego89;


The 'Ramp' at Yeovilton was dismantled not long after the Sea Harrier was decommissioned. The run-up is still there, as is the 'pit' but the actual ramp itself has gone.
I can't say for definite but I think the Wittering ramp has also gone.




A couple of years back I attended a RAeS lecture by Doug Taylor ( ski-jump creator) and he said that the US tested virtually all their fast-jet aircraft at that time on the Ski-Jump.
He showed some slides of various aircraft 'jumping' and, from memory, included A-4 Skyhawk, F-5 Freedom Fighter and, I think, an F-4 Phantom.
I believe the trials were successful at the time.


I never could understand why the US Marines never fitted a 'Jump' to their ships. I'm told that whenever the USMC cross-decked to one of our carriers they spoke very highly of the Ski-Jump.

There is still one ramp in existence in the British inventory http://en.wikipedia.org/wiki/HMS_Illustrious_(R06) :D