Forum: General F-35 Forum

spazsinbad wrote:

. He forgets that the LHDs can be a spare deck in emergency for Harriers/F-35Bs as required or just for cross-decking ..) .

Fair dinkum, mate.

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spazsinbad wrote:

. He forgets that the LHDs can be a spare deck in emergency for Harriers/F-35Bs as required or just for cross-decking ..) .

Fair dinkum, mate.

With a stutter Very Happy

F f f fair D d d d dinkum OR as our recent EX PM would say ockerly 'Fair suck of the sauce bottle'. Rolling Eyes

spazsinbad wrote:

With a stutter Very Happy

F f f fair D d d d dinkum OR as our recent EX PM would say ockerly 'Fair suck of the sauce bottle'. Rolling Eyes

Obviously switching browsers didn't work..,I'm convinced it has to,do,with the latest version ofAndroid I downloaded.. problems started soon thereafter.

spazsinbad wrote:

With a stutter Very Happy

F f f fair D d d d dinkum OR as our recent EX PM would say ockerly 'Fair suck of the sauce bottle'. Rolling Eyes

..

pc, you may want to avoid using the 'back' arrow to return to the general forum after you post.

count_to_10 wrote:

The ramp is useful to fixed wing aircraft because it gives them a higher angle of attack on launch and a little bit of vertical velocity, which means they have more time to accelerate to flight speed before they hit the water.
Helicopters use rolling starts mostly because it gets undisturbed air under their rotors. Tilting them back at an angle just causes the rotors to thrust the wrong way.

A ramp trades horizontal velocity for vertical acceleration depending on the ramp and the change of velocity, the same on a helicopter as a fixed wing aircraft. You might not have watched many Russian helicopters, but they tend to use rolling starts because they lack the raw horsepower to weight ratio of their western counterparts. Some of them depend on forward velocity just to stay airborne when fully loaded, with a huge drop in lift when they stall. Mind you they stall at ridiculously low speeds compared to a fixed wing aircraft, but they do stall.

You also do realize that a helicopter rotor is a complex system, not something that is at a fixed tilt, right? I don't know why you think disturbed air is an issue in ground effect. That is where a book about helicopter flight dynamics would help you understand why a ramp would work for takeoffs.

Wind direction and strength relative to the helicopter takeoff direction are also important. I have looked for helicopter / ramp / ski jump testing to find nothing. I'll keep looking and let youse know.

quicksilver wrote:

pc, you may want to avoid using the 'back' arrow to return to the general forum after you post.

Thanks,,will give it a try.. but this only manifests on F16.net w/c is what's puxxling..

Last edited by spazsinbad on Aug 26, 2012 - 10:11 PM; edited 1 time in total

Back from the 'dead' in 1996 another USMC perspective on Ski Jump Ramps. I wiill try to get the Proceedings NALLS article mentioned in a footienote.

STOVL Air Power
The Ramps, Roads, and Speedbumps to Exploiting Maneuver Air Warfare
Major Charles R. Myers
Conference Group Ten April 1, [UhOh] Twisted Evil

1996

http://www.dtic.mil/dtic/tr/fulltext/u2/a527872.pdf (50 Kb)

Page 7
"Amphibious Ships
The most significant contribution that the Navy could make to STOVL air and helicopter-borne power projection is adding a ramp (ski jump) to all Tarawa- and Wasp-class amphibious assault ships. The technology is proven and for return on investment relatively inexpensive. A ramp not only improves dramatically a STOVL aircraft's takeoff performance, it facilitates concurrent fixed- and rotary-wing operations afloat. Of all countries that operate STOVL aircraft (the United States has more STOVL aircraft and ships to employ them than anyone) the United States is the only country without a ramp-equipped STOVL assault ship. Now is the time for ramps...."

& on page 9:
"...The skeptics insist that ramps will displace landing spots. Tests prove otherwise.

On a 12 degree ski jump approximately 150 feet long, the slope gradually increases from zero up to 12 degrees at the bow. The first half of the ski jump has a slope no greater than that of an LHA during wet-well operations with the well-deck flooded – both Harriers and helicopters can land on it.10..." [Major Art Nalls, USMC, "Why Don't We Have Any Ski Jumps," U.S. Naval Institute Proceedings, November 1990, 81.]

The ramp not only bolsters a STOVL aircraft’s combat payload to its maximum and enhances fixed- and rotary-wing interoperability, it provides a margin of safety to the pilot in emergency situations. The upward vector off the bow offers the pilot extra precious seconds to handle takeoff emergencies and an expanded ejection envelope if required. The price of one saved STOVL aircraft, and potentially the pilot’s life, would probably fund several ramps on amphibious ships. The Navy and Marine Corps need ski jumps on the big-deck amphibious ships.

Unquestionably, an LHA and LHD could never replace an aircraft carrier in total air power projection or air space dominance; however, if task organized properly, either could greatly augment it...."

& on page 12:
"...Sea-based platforms are not the only places where ramps are effective. The Marines must focus on their employment once phased ashore. An all STOVL aviation component provides the Marines an opportunity to double its current EAF capability by simply installing ramps at each end. Today's typical 4,000-foot EAF would decrease to less than 2,000 feet using ramps, yet still provide a maximum gross weight takeoff capability to STOVL aircraft. Additional EAF matting provides vertical landing spots and parking space if needed. More over, ramps provide almost limitless EAF locations wherever there is a straight quarter-mile stretch of road or highway. Korea and Sweden, for example, have designed much of their highway systems for use as conventional runways. A STOVL aircraft requires a mere fraction of that if augmented with light-weight, high-strength modular ramps. Smaller EAFs provide several advantages. A reduced footprint makes it less susceptibile to targeting and the chance of being hit. Reduced construction time, especially when a road or highway is used as the runway, maintains operational tempo...."

Last pages have a scenario for manuever warfare from USMC perspective.

madrat wrote:

count_to_10 wrote:

The ramp is useful to fixed wing aircraft because it gives them a higher angle of attack on launch and a little bit of vertical velocity, which means they have more time to accelerate to flight speed before they hit the water.
Helicopters use rolling starts mostly because it gets undisturbed air under their rotors. Tilting them back at an angle just causes the rotors to thrust the wrong way.

A ramp trades horizontal velocity for vertical acceleration depending on the ramp and the change of velocity, the same on a helicopter as a fixed wing aircraft. You might not have watched many Russian helicopters, but they tend to use rolling starts because they lack the raw horsepower to weight ratio of their western counterparts. Some of them depend on forward velocity just to stay airborne when fully loaded, with a huge drop in lift when they stall. Mind you they stall at ridiculously low speeds compared to a fixed wing aircraft, but they do stall.

You also do realize that a helicopter rotor is a complex system, not something that is at a fixed tilt, right? I don't know why you think disturbed air is an issue in ground effect. That is where a book about helicopter flight dynamics would help you understand why a ramp would work for takeoffs.

Unless the helicopter actually has wings to take part of the load, all the rolling start does for a helicopter is get it out of it's own down-wash. Giving it a little extra altitude at the expense of slowing it down and tilting it in the wrong direction isn't going to help one get off a carrier.

As a matter of fact many Russian helicopters do employ wings. And many experimental helicopters that use separate engines to boost power in forward flight also use them. But wings are in most cases irrelevant to operating a helicopter in forward flight if it has enough power to not use them. Your rotor doesn't have the same lift statically as it does with velocity. If you do a little studying you would understand why a ramp would work.

Just putting this out there. Regardless of whether a ramp can actually improve the takeoff dynamics of a rotary-wing aircraft, I highly doubt a helo pilot would be willing to fly a bird so heavy that it can't effectively lift itself off the deck like normal. Besides, wouldn't the ramp pose a hazard to the tail-rotor? No, I think ramps are a non-starter for helos (excluding possible experimental types that are irrelevant anyways).

madrat wrote:

As a matter of fact many Russian helicopters do employ wings. And many experimental helicopters that use separate engines to boost power in forward flight also use them. But wings are in most cases irrelevant to operating a helicopter in forward flight if it has enough power to not use them. Your rotor doesn't have the same lift statically as it does with velocity. If you do a little studying you would understand why a ramp would work.

You keep repeating that, but you aren't demonstrating any understanding why it should be so. If you tilt the rotor backward, you are only slowing the craft down without improving lift. It simply isn't going to work the same way for a rotor craft as it does for a fixed wing aircraft.
For a tandem rotor or coaxial rotor, it may be a different story -- in those cases, a forward velocity can be used to generate more lift on the forward moving blades of both rotors. But you still have to deal with the problem that the ramp would be tilting the rotors backward, causing their thrust to slow the craft down.

I could see a ramp with a shallow inclination working with an Mi-35-type aircraft that really does use its wings for lift. In all honesty, navalized Mi-35s could be an interesting platform for the USMC, with the ability to perform routine or emergency troop movements in addition to providing fire support. Of course, the airframe is huge, but...

Forum: General F-35 Forum

Possibility small STOVL carrier USN/USMC