Slashdot Mirror
First Hover Flight Test of X-50A Dragonfly
kbielefe writes "On Wednesday, flight testing began on the X-50A dragonfly canard rotor wing unmanned aircraft. For those of you not familiar with the dragonfly, its rotors work like a helicopter for takeoff, hovering, and slow-speed manouvering, and then lock into place like a fixed-wing aircraft for cruising. The X-50A's reaction drive makes it "much lighter, simpler and more affordable to operate and support than traditional rotorcraft." And the technology is scalable to larger, manned vehicles. Truly a revolutionary aircraft, with a multitude of potential military and commercial applications." There are some more photos and artwork.
Did you know that in the 50's the Army almost decided not to use helicopters at all after about a hundred soldiers were killed during trials of the Piasecki helicopters? There were people in the Army who were screaming that it was criminal to keep putting men into helicopters.
While I think that the Osprey getting grounded for a year and a half while they fixed the safety-critical problems was appropriate and justified, I'm glad that it's back in the air, and I think that it can really change the face of airmobile combat.
This space for rent.
Does this actually mean something, or is it just a bunch of big words to confuse the general public?
A bit of both.
Conventional helicopters need a tailrotor because main rotor is spun by a mechanism that is fixed to the body of the aircraft which tends to spin the body around too. This thing seems to use a tip-jet mechanism to spin the main rotor, ie the tips of the blades contain little jet nozzles to spin it around and since it isn't mechanically fixed to the body it won't tend to spin the body around too.
Sorry if that didn't as much sense as i wanted it to, i haven't slept in 2 days.
It means that there's nothing inside the vehicle, cranking the rotor around, so the vehicle never tries to crank itself the other way.
This space for rent.
This vehicle isnt designed for the civil market. at all. The FCC would never approve this vehicle in its current form. It has no pilot, no redundancy, and no business case for civil aviation. It is a technology demonstrator for a warcraft, developed in response to DARPA and DoD requests.
This space for rent.
Ah, but that's exactly why it does make sense.
In a conventional helicopter, the rotor is spun by a driveshaft coming up into the center of the rotor. This creates a torque on the rotor, spinning it. By Newton's third law, there is an equal but opposite torque applied to the rest of the helicopter, causing it to rotate in the opposite direction. Thus, the tail rotor.
In the Dragonfly, hot gas is exhausted at the rotor tips, in a direction perpendicular to the rotor's axis. Since the gas is travelling down the rotor axis, a force must be applied to cause it to change direction, and Newton's third law again says that a complementary force will exist on the exhaust housing, and thus the rotor tip. This force produces the torque to spin the rotor.
Since no torque is applied to the rotor by the helicopter, no torque is applied to the helicopter by the rotor.
But then again, I could be wrong.
I have no idea what you think is so bad about the lift fan design, what "enourmous mechanical stresses" are you talking about which aren't present in a traditional STOVL aircraft? Harriers and the Boeing JSF entry both create lift with exhust nozzles from the engine. This design is on the ragged edge of stability, it barely creates enough lift to lift the aircraft and has the inherrent danger that if the engine inhales its own exhaust it can stall, which is a very bad thing when you're trying to take off or land! The lift fan is a revolutionary design which creates a cushion of cooler air below the aircraft, eliminating the intake threat and has an excess of lift capacity. The initial test was amazing, the plane literally shot up 20 feet! The design has won numerous awards as well, you are the first I have heard to disparage it.
When you lose something irreplaceable, you don't mourn for the thing you lost, you mourn for yourself. - Harpo Marx
Page is out of date by almost a year.
:-)
Wow. They've had a year to correct the typo "f light test" (first paragraph, second sentence)?
Maybe they should switch their proofreading staff to metric.
Five percent of one year's DoD budget puts us on Mars.
The Harrier has a high rate of failure.
- ha rrier-day1.story
c fm ?Id=303
a ir craft/av-8-variants.htm
http://www.latimes.com/news/specials/harrier/la
"Over the last three decades, it has amassed the highest rate of major accidents of any Air Force, Navy, Army or Marine plane now in service. Forty-five Marines have died in 143 noncombat accidents since the corps bought the so-called jump jet from the British in 1971. More than a third of the fleet has been lost to accidents."
"If the Harrier had been decisive many times in battle, we would all still regret horribly the tragedies of the pilots who have been killed, but at least you'd be able to say that the Harrier made a difference," said Philip E. Coyle, the Pentagon's chief weapons tester from 1994 to 2001.
"What makes this situation so difficult is that we just don't have that kind of battlefield record to support the accidental deaths."
In the Persian Gulf War in 1991, the hot thrust-producing nozzles in the heart of the fuselage -- the devices that allow the Harrier to rise and balance in the air -- made the plane a magnet for heat-seeking missiles. Its loss rate was more than double that of the war's other leading U.S. combat jets. Five Harriers were shot down and two pilots died.
"It's the most vulnerable plane that's in service now," said Franklin C. "Chuck" Spinney, who evaluates tactical aircraft for the Pentagon. "You can't hit that thing without hitting something important."
http://www.nationaldefensemagazine.org/article.
"The AV-8B Harrier--a single-engine attack jet that can take off vertically and hover--has a mishap rate of 12 per 100,000 flight hours, among the highest in the U.S. military aviation community. But only one-third of Harrier mishaps are caused by human error, Dirren said. "Two-thirds [of the mishaps] are related to the aircraft failures."
http://www.globalsecurity.org/military/systems/
"In 1982, after eleven years of AV-8A operational flying, including 55 peacetime aircraft losses, the Commandant of the time (Gen Robert Barrow) asked the Harrier community to address the serious problem of flight safety. The impetus for his concern was "a high mishap rate within the AV-8A community... anticipated continuing turbulence... and a pressing requirement to reduce the mishap rate in order to provide the assets needed for successful transition to the AV-8B." At the time, the community had a cumulative Class A rate of 39 per 100,000 flight hours."
"By 1998, USMC Harrier operations (including Naval Air Systems Command) had resulted in 17 fatalities, one permanent disability and 68 AV-8B aircraft lost. With a cumulative Class A mishap rate of 12.1 per 100,000 flight hours, the AV-8B has consistently outpaced all USMC aircraft types in this statistic."
The FAS website estimates 815 Harriers built in all models all the way from the Kestrel and P.1127 test planes
http://www.faqs.org/docs/air/avav83.html
The air pressure on the turbofan.
The harrier is designed to produce lots of thrust at zero-speed. F-16's are designed to produce lots of thrust at high speed. While the F-16's produce a pretty good amount of thrust at low speeds (20kts), it's nowhere near that of the harrier.
It's an aerodynamic dichotomy. You can't have both (easily at any rate), unless you go the JSF route and use a big ol' fan that hides itself away. It's like trying to get a semi to do a 13 second mile.
The Fairey Rotodyne was built nearly fifty years ago. Like the Dragonfly, it used (what was then called) tip-jet rotors, so there was no need for a counter-torque rotor on the tail.
The Rotodyne was advanced technology for its day, but it was killed by the politicians.
Aircraft status: "oh shit!"
The pilot made it back, sucseeded in landing, and the aircraft was repaired to full flightworthy status. Altough, I'm not sure on the 48 hour turnaround time.
A similar story is here
I also saw an article on another A-10 that was on almost constant missions during Desert Storm and saw a tremendous amount of action. When the ground crew finaly got her in the hanger for maintence they they went over her and counted over 1,400 impacts on the outer skin from weapons of various calibers, from small arms to AAA.
The only A-10 that I heard of being shot down, was during Gulf War II. Where a doomed A-10 was running a mission near the airport in Bagdad and got nailed with a lucky shot from an Iraqi firing a RPG (an anti-tank weapon, mind you).
For more information on A-10s go here and here.
"The engines can create an unusual vortex that has never really been seen before. When this vortex happens they loose lift and control of the aircraft and it crashes."
Vortex ring states are common to all rotary-wing aircraft. It involves a toroid-shaped volume of air surrounding the rotor disc, in which air pushed downward is recirculated into the top of the rotor disc, instead of pushing against the ground. All helo pilots are trained in how to avoid them and attempt to recover from them. It is a subject of thorough investigation in aerodynamics, and a problem inherent to every helicopter. What makes its presence in the V-22 significant is that even a mild vortex ring state in one of its rotors can cause a drastically sharp roll movement (due to uneven lift on both sides) that is very difficult to recover from.
"The B-1 bomber also suffered a number of crashes in testing."
The B-1B has also proven to be a hangar queen with tremendous operating costs, going against your point of "here are some aircraft which vindicated themselves in actual usage".
I do agree that tilt-rotor technology is the logical evolution of transport helicopters. This isn't just some novel "hey that's neat" offshoot of helos; this is the next generation of rotary-wing tech, something that will eventually replace Chinooks, Sea Knights, Mi-6's and the like.
whilst it is entirely true that they're FRAGILE (ie: you can shoot most down with a pistol), they are FAR from "flaky". aside from the fragility issue, they are no different from fixed wing aircraft in their "flakiness". they simply trade high speed for the ability to hover, that is ALL. and, incidentally, there is no fix for the speed issue in a conventional chopper, at some "N" speed, the retreating rotor blade stalls and the bird flops over.
most people don't realize that helicopters share EVERY flight characteristic (sans high speed) with a fixed wing aircraft, including the ability to "glide" (they call it autorotation in choppers, the air rushing up through the rotor keeps it spinning, and you flair at the last moment. every helo pilot can do it, and you land without a scratch as long as the surface is apporpriate)
mas cerveza, por favor politically incorrect stu
Just curious, anyone knows how this compares to a regular automobile ?
If your car has a problem with the steering, you put on the brakes, and maybe have enough steering capability to get out of traffic. If something jiggles loose in the engine, even in the worst case if a piston were to stick, a rod thrown or timing belt cracked, timing got out of wack and you busted the valves and cracked the block, etc, you stick it in neutral and coast to the side of the road.
The Harrier has had "steering" and engine problems similar to these over its life. Almost all the time, it crashes and the pilots die. Mechanical failure in a car means you pull over to the side of the road in the majority of cases. Even in an airplane you can usually glide to a relatively safe crash-landing, although commercial jets aren't exactly graceful in air. But the Harrier? No way. If you have problems it will probably tip on the side or upside down, making it problematic even to eject and safely observe the wreckage. Assuming the eject mechanism works, of course.
24 beers in a case, 24 hours in a day. Coincidence? I think not!
The F-35C can go supersonic, and I think the Yak-141 can as well.
Just a couple data points.
Why yes, I AM a rocket scientist!
Also the Navy actually has an extensive fleet of fixed wing aircraft. Quite a few are for transport
C-2A
C-9B
C-20G
C-40
They also have quite a large collection of Cargo Rotary wing aircraft:
CH-53
UH-60
fas.org the best source of US Military information if you don't have a library near by for Janes.
But ask any British Falklands vet what he thinks of the Harrier and I bet you he'll love 'em. So they have their uses.
Human genome = 3 billion base pairs = 6 GBit. Windows + Office = 20 Gbit. Which is more impressive?
The biggest problem here was a question of tactics. Army doctrine (now being adjusted) still called for coming to a hover before firing weapons. This obviously exposes the aircraft to high risk small arms fire. Marine doctrine on the other hand has helo pilots firing on the run, not slowing below 60 knots in combat. This difference accounts for much of the combat robustness of the Cobra over the Apache. In fact, before the war, I believe the Marines upped their minimum combat speed.
/. have seen/heard a V-22 approach an LZ at 100 feet AGL in airplane mode. It is nearly silent until a 100 or so yards away. Transition can be quick (15s) land, dump cargo, and transition to forward flight again. Because of this reduced exposure/announcement time, the V-22 is more survivable than an old CH-47 or CH-46.
That said, landing involves stopping, and is always risky. The V-22 has the ability to enter and egress an LZ faster and quiter than any other current rotary wing aircraft. I doubt many on