Ive been searching for pics of it “hovering” and all the pics i can find its running dirty (flaps down, gear down etc) is it always like this or does it have the ability to “hover” with everything up like the harrier? (except the fan doors of course)
Also can it truly hover or is it just extremley slow faward flight?
I couldn’t find any pics of the Lightning II like that either. One would assume that it would have a clean hover though. After all it is supposed to have stealth capability.
I’ve seen videos of it in stationary hover, so I guess the answer to that is yes.
http://www.youtube.com/watch?v=XIsIzjVi7j4
I don’t think the hover capability is used other than for landing/take-off, so I don’t know if there is any reason to hover with the gear up. Having the gear down also lowers the CG, giving added stability (lower roll centre). I think that you will find that when a Harrier hovers with the gear up, the flaps are usually still lowered.
I don’t think there is a reason for it to hover other than for take off and landings. STOVL (Short Take Off Vertical Landing) are really intended to be used where traditional runways are not available, such as the deck of an assault ship or runways that have been damaged by enemy attacks. They are not designed to be helicopters. I read somewhere that the flaps on the Harrier are used to trap some of the gases when hovering and improve lift. Maybe there is a Marine pilot of a Harrier here that can verify?
I believe the flaps on the Harrier are also lowered to help smooth the airflow and reduce turbulence around the trailing edge of the wings (Acting as a “dam” to prevent air coming over the trailing edge and coming “backwards” toward the rear nozzles, forming vortices below the wings which would create instability and reduce lift? Only an educated guess on my part)
PS: I recently saw a bird hovering stationary in a strong headwind coming up a hill off the ocean. It remained perfectly still in the one spot for about 3 minutes despite gusting winds. You could see its wingtips and tail twitching to maintain position, but relative to the ground it did not move at all. Every few minutes it would move to a different spot and repeat the act. A truly amazing sight to watch. They know a hell of a lot more about flying than we do…
EDIT: Another guess, but “flaps down” also puts the wing in maximum lift configuration for transition to/from “winged” flight mode.
Like the F-22, the F-35 is only stealthy when it’s buttoned up. The F-22 armament bay doors open and close quickly to facillitate rapid weapons launch to keep the radar cross section as low as possible. I would imagine the F-35 Marine version in hover mode would have a rather large radar cross section with all the ducting covers open. Hovering with the landing gear up probably wouldn’t make that big of a difference.
Didn’t Obama cancel the engine for the Marine version making this a moot point anyway?
Its never a moot point when curiosity is involved. i dont care if its going into marine production or not, i was just curious as to why its never seen gear up hovering.
British harriers use the hover to perform ambushes, or so ive been told. seen a couple photos of them, hovering below tree lines to mask radar signatures then pop up, take a shot and move on.
That would be a great ambush tactic but the Harrier is extremely loud when hovering. I am sure the Pratt & Whitney F135 engine would be much quieter but we may never know.
Oh well, cheers for the help guys. so long story short nobody knows, and the much anticipated JSF is a no go?
As far as I am aware, the JSF program continues. The engine cancellation referred to is the proposed cancellation of the alternate engine (RR/GE) program. JSF (for now) continues with the P/W as the primary (and probably sole) engine design for the type.
Oh ok, cheers. was the new engine to be more powerful? quieter? what was the deal?
Scorpiomikey, you’re absolutely right about curiosity not being a moot point and I’m sorry if I implied it was. As far as the RR/GE engine the knowledge I have is second hand at best so take it with a grain of salt but here goes: When Lockheed/Martin got the bid for the JSF they did so on the strength that their design met the specs for all three branches of the service with the provision that the Navy and Marine versions would have a lower combat load due to the increased weight of the Navy version’s gear for carrier landings and the Marine version’s STO/VL gear and still be capable of super cruise (mach plus w/o afterburner) and 80% parts commonality.
Problems immediately arose with the Marine version’s weight due to the STO/VL design and it was found that it could only hover and transition with a minimum of fuel and payload. Unlike the Harrier which uses all of its equipment for both forward and vertical flight the JSF uses vectored exhaust and ducted fan with about a 60/40 thrust split. This design was felt best in order to meet the super-cruise requirement.
The main problem is that all of the ducted fan equipment (fan, ductwork, drive shaft, gearbox and extra bulkheads) is just dead weight in normal flight. It was believed the best way to shave weight and improve performance was to up grade the engine and P/W set about to do this. About this time RR/GE stepped in and said it already had an engine which would meet the new performance requirements but that it would be considerably more expensive. Even so, it was decided to go with the RR/GE engine for the Marine JSF in order to keep the program on schedule.
P/W didn’t like losing business that it felt was rightfully theirs and used their lobbying clout to get the RR/GE deal nixed with the hope that the extra money would go to them instead for further developement of their engine. The RR/GE deal was dropped but no extra money was given to P/W thus leaving the Marine JSF in limbo. The Navy and Airforce versions remain in certification testing with the Marines having to “make do” with the Harrier for the foreseeable future. The whole project is behind schedule and over budget.
I have an acquaintance that’s in the lobbying business in D.C. and this came from him. Like I said, take it with a grain of salt.
This is a little speculative, but I suspect that the RR connection was something of a carrot to keep Britain committed to JSF as the Royal Navy is supposed to be one of the customers. I believe the higher thrust engine was also favoured by the British to fit in with their “bring unexpended ordnance home” policy. Extra engine power is a handy thing when making a vertical landing on a pitching carrier deck.
So as it stands the harrier is still the better of the 2 aircraft? even though its slower? if i remember corectly it took 2 companies a long time to perfect the Harrier (and 2 countries maybe?) so maybe the best thing here would be to get hawker/sydley involved and see what insight they have into it. but yeah.
Thanks for the help guys. interesting to know. And sorry for getting a little hot under the collar about that moot point thing
I don’t think the hover capability is used other than for landing/take-off, so I don’t know if there is any reason to hover with the gear up. Having the gear down also lowers the CG, giving added stability (lower roll centre). I think that you will find that when a Harrier hovers with the gear up, the flaps are usually still lowered.
Phil: it does have the ability to switch flight profile and angle of attack with the hover mode. The History Channel had a great “Dog Fights” episode on a while back where they talked about a war with China. The F-22 and F-35 were the main A/C discussed and this was shown through CGI. Kinda like the famous “I’ll hit the breaks and he’ll fly right by!”
I haven’t seen any pics of it in “clean hover” as most of the picks were snapped during the test and I think the flaps and gear help stabilize the plane.
Travis/STFD637
I don’t know if you could say that the Harrier is the better of the two without putting them head to head. Certainly the Harrier has earned it’s stripes in combat while the F-35B is still under development.
The Harrier, while brought up to date with digital avionics and modern composite materials and such, is still based on a design which began development in the late '50’s.
Going by the numbers, the F-35 should be able to carry a much greater payload a much greater distance. As far as VTOL performance is concerned, it’s one aspect of the flight envelope but it’s not the F-35’s raison d’etre as it was for the Harrier.
Comparing the two just because they have VTOL capability is like comparing apples and oranges because they are both fruit.
I haven’t seen the program, but you may be thinking of the use of vectored thrust to augment manoeuvrability in otherwise conventional forward flight. F-22 has movable exhaust nozzles which can be “steered” up/down to enhance pitch rates. This has nothing to do with “hover” mode per se (F-22 does not hover).
I believe that the F-35 had been designed originally with a similar vectored thrust nozzle at some stage in its design life, but this was deleted from the “primary” production model (cost/weight/complexity perhaps?).
F-35B’s engine nozzle can vector downwards to provide vertical lift but as far as I know, it doesn’t vector upwards, which would be required to use this to increase AOA while maintaining forward flight.
Then again, I’m not fully read up on the F-35, so I could be wrong.
Unfortunatly I saw that program about a year ago. It was called “Dog Fights Of the Future”…or something like that. It was awesome! The new uses for the B-1B as a Air to Air missle carrier basically. I guess they have ubgraded it, and with the F-22 ability to target multiple A/C the fighters would just guide the missles to the targets.
I really don’t know all that much with regards to the flight characteristics either…I guess that is why those are called “Secret.” [;)] What the show had shown was the F-35 using the downward nozzle setting and the mid-fusilage fan and exhaust to assist in accomplishing this. Then again this was all Computer generated and who knows? Fun to think of. I would love to find the DVD of the show.
Cheers,
Travis/STFD637
Hi Travis,
I found the videos on Youtube. While it was somewhat interesting, I found myself wondering what the source material was. Dale Brown’s novels perhaps? [proplr]
Certainly there are some capabilities presented which actually exist, but there was also much which I would consider to be speculative. B1’s armed with AAM’s with V-tails? I am guessing that there is a certain amount of Brown’s “Megafortress” influence there. The only thing missing from that was the forward sweeping wings. Do a search on Brown’s “EB-1C” concept.
The Raptor doing the “Cobra maneuver” in mid-dogfight is a little unrealistic. Speed is life, especially if there’s a gomer on your six. Pulling such a maneuver in the way depicted will bleed airspeed to effectively zero and then it takes time to acellerate again. Not clever if there’s more than one bad guy around - you would force the one on your tail to overshoot, yes, but you would be a sitting target for anyone else trailing.
If you can use thrust vectoring to perform such a maneuver (and no, it’s not essential, a number of aircraft can do this without thrust vectoring), then you can use it equally to break away hard while maintaining your energy Where vectored thrust will save your butt is in the enhanced pitch and roll rates that it affords and knowing when and how to use them effectively - but there’s no point doing airshow display maneuvers while theres a bad guy on your tail.
And no, there was no mention of the F-35 using the lift engine to augment maneuverability.
The reason there’s no pics of the JSF in a clean hover is cause it’s still in the early testing phase. When the test aircraft that are VSTOL do a first flight with hover the gear and such will always be down in case of an emergency. As they expand the flight envelope they’ll start the more complex flight manouvers. That’s of course if they don’t cancel the program all together. It’s getting closer to being canceled due to program delays and MASSIVE cost overruns.