F-16.net

The statement that STOVL requirements impacted the overall performance negatively of other versions, was written in an article in Air International by somebody who was in the design team of the Kestrel/ Harrier GR.1.

'shedload of software', in 2002 there was a shortage of software design/ development capacity regarding the F-35 program, I do not know if this problem is solved.
The F-35 contains 5.000.000 lines of code, compare this to the F-22 with it's 1.7 million LoC and even this is more than the number of LoC in the Aegis system on board of the Ticonderoga class cruisers.
Software development is seen as the biggest risk in the JSF program, a large part of the F-35 software is commercial off the shelf. Although installing, integrating, testing and certification takes a lot of time.

F-16.net Sponsor

This message from our sponsor will disappear if you log on as a member.

I've seen higher numbers for F-35 code. I agree 100% that it's the biggest challenge for the development team.

Can you tell me which edition of Air International? I occasionally purchase a copy so I may have it already. If it focuses on just the design compromises caused by the STOVL requirement that it's not telling a complete story because the unique USAF & USN requirements also forced compromise. I'm not impressed in general by the UK's enthusiast press on JSF. Much too much flag waving.

It was an article focused on the STOVL requirement.

RonO, the Air International edition is from June 1993.
In this article the author writes about the joint UK/US ASTOVL program, which started in 1986.
He was involved in the P.1127 (Kestrel/Harrier) and supersonic P.1154, he wrote that the Americans are the world's greatest inventors, perhaps because they are brought up on 'Popular Mechanics'.
However, the problem with inventors is that they are peculiarly inept at distinguishing between good and bad ideas, the USA has an unbroken record of total disasters in the V/STOL field.

In the ASTOVL program, 4 concepts were examined: 1. advanced vectoring thrust (X-32), 2. remote augmented lift system, 3. ejector lift, 4. tandem fan.

'Nr 4 tandem fan', was rejected because of weight and technical risk.
'Nr 3 ejector lift' was tested in the Rockwell XFV-12 in the seventies, rejected because it did not work; tested again!, in the US/Canadian E-7: a STOVL derivative of the F-16, second conclusion = do not work.
'Nr 2 remote augmented lift system' (RALS), rejected from a ground erosion viewpoint.
'Nr 1 advanced vectored thrust', the X-32 Bullfrog was rejected.

It is funny, that BAe/MDD left the Harrier concept, first were researching the RALS, later they teamed up with Northrop. BAe/MDD dropped RALS and together with Northrop they favoured the Yak-141 concept, a vectoring nozzle in the stern and a lift engine 'behind the bridge'.

The author compared the mechanical shaft-driven remote fan concept (X-35, f-35B) with the GE/Ryan XV-5 Vertifan.
Aside from the obvious weight and volumetric penalties, the major problem with lift-fans is that the large mass flow (which provides the desired thrust magnification and low downwash energy) is naturally associated with a correspondingly large momentum drag.
In essence, a large tube of air that is whistling toward the aircraft during the take-off roll is suddenly brought to a halt so that it can pass vertically down through the lift-fan.
There must also be some concern that a lift-fan has considerable inertia, and may take several seconds to spin up and generate the lift advertised.
If such an aircraft were to take off in the manner of a Sea Harrier, the lift-fan might be run up prior to brakes release, then all the thrust diverted aft for acceleration. However, as the thing went over the bow and power was switched back to the lift-fan , there would still be some white-knuckle moments as the revs built up again and the salt spray washed the flies off the windscreen.

The shaft-driven remote fan (SDRF) provides an interesting design challenge, especially in regard to the clutch, which is going to handle something in the order of 25,000 shp (18,382 kW). This is going to be an aviation first for some trail-blazing rotating machinery company.
Given the poor STO performance of the SDRF, the F-35B might end up in the V/STOL 'Wheel of MisFortune'.

I would rather put my money on: AV-8C Harrier III, F-35B with mid-ship lift-engine (a derivative of the CF34-8 in combination with the F-136, Jack Welsch's quality products) in Yak-141-style, or F-35C ESTOL-style.

At http://ails.arc.nasa.gov/Images/WindTun ... 30-30.html
you can find a picture of the General Dynamics/ de Havilland Canada/ NASA and DARPA E-7.
I have more pictures of the E-7, but I am to clumsy to export to this site, maybe the 'site-possums' (moderators) can help me.

Last edited by locum on Aug 11, 2006 - 09:40 AM; edited 2 times in total

The French aircraft carrier Charles de Gaulle is 265 m. / 869 ft long and is 40,600 metric tons heavy, the Tarawa/ Wasp class LHA class is 257 m./ 844 ft long (flightdeck=249m./ 816ft) and is 40,500 tons (36.450 metric tons) heavy, the CdG can also launch the E-2 Hawkeye. Retrofit the Tarawa/Wasp and proposed LHA (R)-class with a longer and Nimitz-class style deck.

The F-35Bullocks has a significant shorter range; significant higher development-, purchase- and maintenance price; shorter MTBF then F-35A & C; higher spot factor then the F-35C; higher attrition and the F-35B needs better trained pilots and ground personel, in the meantime USMC grunts body armour is bought by themselves!
As USN and USMC air fleets are getting integrated, CTOL aircraft modified LHAs add flexibility and a USMC operating F-35Cs gives more commonality.
Eventually, ESTOL capability could be added to the F-35C eventually combined with a Jaguar-style landing gear so the F-35Estol could operate from bare base unpaved short runways.
Although, I think it is to late to incorporate a Jaguar-style landing gear, what a pity!, in this case it could also operate from grass fields.
The F-35B contagious?

locum, forgive me for interupting the conversation you have with yourself. The fears about the F-35B lift fan working were fully dispelled during the X-35B flight test program. Anyone who still clings to the thought that the technology being American does not work has his head firmly where the sun doesn't shine.

You are totally incorrect in your statements that the F-35B is more expensive, less reliable, needs better trained pilots/ground personnel than the F-35C. The opposite is true.

The F-35B may have less unrefueled range than the F-35C but it can operate from a thousand more airfields in the world and from ten times the numbers of ships. Neither does the B have a higher spot factor that the C when the need for the required air tankers are added to the equation.

Your dream of operating F-35C's from LHA's is as ridiculous as your name for the F-35B. You need to grow up.

Isnt the lift-fan technology actually Russian? As found on the Yak-watever Freestyle?

No. The Russians used a seperate engine.

They used a seperate lift fan... but the TVC idea was liscenced from them.

Last edited by locum on Aug 11, 2006 - 10:01 AM; edited 1 time in total

The lift-fan technology is American, it was first applied to the Vanguard Omniplane 2D which only did thetered hover tests but was discontinued in 1962.
The second attempt was made by the GE / Ryan XV-5 Vertifan, which made a transition in November 1964. The drawbacks of the XV-5 were: large volume & weight occupied by the liftsystem, slow control response and the narrow transition corridor.

Catapult TO But Arrested Recovery (CATOBAR) on Tarawa and Wasp LHAs? Ingalls Shipyards said: Mission Impossible, I admit RonO that's rediculous. Although the British refitted the 29.000 tons HMS Hermes with catapults and arresting gear to operate jetfighters, later this was removed because the Hermes was turned into a 'Harrier carrier'.
However, Short TO But Arrested Recovery (STOBAR) is in theory possible on the Wasp-class. The Tarawa ships are too old, but the Wasp ships can be modified with arresting gear.
STOBAR would contain most of the advantages of STOVL and CTOL but without the disadvantages of each.
Preferrably the Wasp-deck needs a stretch from 816 to 888 ft /270.8 meter, so it can operate the F-35C during very hot weather and/or increased weight, the Wasp-hull has a modular construction and the ship can be stretched at a place just in front of the 'island'. In this case the only disadvantage is: it does not have an angled deck.
The proposed LHA (R) weighs over 50,000 tons (45.350 metric tons) and 921ft /280,9 m. long, this ship-class will replace the Tarawa in the next decade. As it is still on the drawing board, it can be designed to operate the F-35C in CATOBAR or STOBAR with an angled deck but and deck overhang for greater flight deck area. But not so much overhang as the 'Charles de Gaulle' to prevent rolling problems, such a ship could also fullfill the UK CVF requirement.

RonO, there is a big difference between the Xperimental-35B and the Fighter-35Bravo (bravo?), according to the Royal Navy: the F-35B is the most risky and costly version and has severe operating limitations.
ESTOL is a practical alternative to STOVL and CATOBAR/STOBAR, conventional landing approaches are typically flown at airspeeds 1.3x stall speed. ESTOL would enable aircraft to land at speeds below their stall speed, with: a significant reduction in landing distance required; less structural stress in shipdeck and ESTOL-airframe and less stress in arresting gear if applied.

ESTOL is essentially an autoland system using STANDARD technologies; where it differs is in allowing a pilot-selectable AoA to maintain a below stall speed approach.
Altitude and position during the approach are critical and are determined by an extremely accurate navigation system blended with inertial navigation. Known as the Integrity Beacon Landing System, it is based on a differential global positioning system, augmented by ground-based pseudolites and gives accuracy to within approx 2-10 centimeters/ 0.8-4inch.
Unlike conventional landings, where the aircraft flares (pitches up) immediately prior to touch-down, ESTOL touch-down manoeuvres are initiated when 'minimal tail clearance' is reached and this altitude is maintained by pitching nose down (de-rotating). It is claimed, that a F-18 sized ESTOL aircraft needs a take off roll of 110 meter/ 361 ft and a landing roll of 175 meter/ 574 ft.

I have no reason to doubt that the F-35B will perform exponentially better than todays STOVL technology (Harrier). I think it's obvious that a shaft-driven lift fan is far more efficient than a series of ducts and shoulder nozzles. Also, it's my understanding that because the Harrier has little airflow over the engine while hovering, it has to carry water to be injected into the engine to keep it cool thus limiting hover time. The F-35B doesn't suffer this limitation because some air is always being ducted to the intake.

Alright guys, I've got a slightly odd question about landing the B-model. If the F-35B comes back damage, possibly heavily damage, do the carriers in question have arresting cables to stop the plane so they can do a conventional carrier landing? Basically, say the fan is damaged in combat "somehow" is that plane doomed unless it can get to an AF controlled strip of Navy carrier? I'm not trying to troll, you know me... I ask stupid questions.

Nope. If the fan is damaged but the rest of the engine is fine, the choices are eject or divert to a land base with a long runway. Same as for the Harrier. Same as for an F-18 that's had its hook shot off.

Don't carriers have those blockade nets? The big rubber strips which are strung across the deck to stop the aircraft?

F-16.net

Forum: F-35 Lightning II

B Model Engineering