Much of the concern over LTE comes from an early design flaw built into Bell 204 and 205 tail rotors and later carried over to the AH-1G Cobras. These early Bell tail rotors were situated on the left side of the tail boom and turned in an anti clockwise direction. This combination resulted in the tail rotor blade traveling down through the main rotor flow rather than up through it. Certain low speed and cross winds situations dramatically degraded tail rotor performance resulting situations identified as LTE. Bell rectified this by retaining the same tail rotor but relocating it on the right side of the tail boom. In this configuration the tail rotor blades travel up through the main rotor flow and were less susceptible to LTE.
There have been many instances where modern helicopters have experienced some form of LTE. The Blackhawk rolling down the hill and Erickson Aircrane rotating out of control during a water pickup are two recognizable examples. In these examples main rotor torque required exceeded tail rotor anti torque available. The tail rotors were operating as designed but in excess of there capabilities resulting in a loss of directional control.
LTE is caused by an aerodynamic interaction between the main rotor and tail rotor. Some helicopter types (Jetranger) are more likely to encounter LTE due to the insufficient thrust produced by having a tail rotor which meets certification standards, but which is not always able to produce the thrust demanded by the pilot.
Quote taken from a UK Safety organization report on LTE.
I see theres been another CH-53 accident in Afghanistan, reported as a D model which seems surprising as theyd be long in the tooth now. Also mentioned the Hawaii based unit will be transitioning to the V22. The article talks about a possible technical fault but who knows with newspapers these days. Either way a new V-22 has to be alot safer than an old CH-53D.
WASHINGTON (Reuters) - The Pentagon's $525 billion budget plan for fiscal 2013 calls for spending of $178.8 billion to develop and buy new warships, fighter jets and other major weapons, a 7.5 percent drop from the level initially projected for the coming year, according to a detailed budget document obtained by Reuters. The total acquisition spending amount is about 12.2 percent down from the level the Pentagon requested in last year's budget, the document shows. The fiscal 2013 plan foresees spending of $109.1 billion for procurement and $69.7 billion for research and development, compared with earlier projections of $117.6 billion for procurement and $75.7 billion for R&D. The document shows that the U.S. military is maintaining high levels of spending on most aircraft and ships as it shifts its focus to the Asia Pacific region, a new military strategy announced last month by President Barack Obama and Defense Secretary Leon Panetta. At the same time, funding for ground vehicle programs will be far lower as the U.S. military reduces the size of the Army and Marine Corps after 10 years of war in Afghanistan and Iraq. Panetta last month gave highlights of the 2013 budget, his first as defense secretary and the first that takes into account a deficit-reducing measure passed by Congress that requires cuts of $487 billion from projected spending over the next decade. It is also the first Pentagon budget since the September 11, 2001, attacks that requests less funding than the year before. Weapons makers like Lockheed Martin Corp, Boeing Co, Northrop Grumman Corp, General Dynamics Corp, Huntington Ingalls Corp and Raytheon Co have been anxiously awaiting details about their programs. The Pentagon is due to formally release the details on Monday when Obama sends his 2013 budget request to Congress, which must approve the spending plan. AIRCRAFT FUNDING DOWN The plan for the 2013 fiscal year, which begins on October 1, requests $9.17 billion for the Pentagon's biggest weapons program, the F-35 Joint Strike Fighter, down slightly from $9.25 billion requested in fiscal 2012. That includes $2.7 billion for ongoing development of the radar-evading supersonic jet, and $6.15 billion to pay for 29 jets, down from $6.33 billion for 31 jets in 2012. Panetta announced last month that the Pentagon would slow the ramp-up in production of the new fighter to allow more time for testing and avert costly retrofits. Overall spending on aircraft programs will drop 12 percent to $47.6 billion in fiscal 2013 from $54.2 billion in the fiscal 2012 budget request, mainly due to a 41 percent drop in funding for the Lockheed-built C-130J transport plane, and a 32 percent cut in funding for the V-22 Osprey. The Pentagon proposed spending $835 million on seven more C-130J airlifters in fiscal 2013, down from $1.43 billion for 12 planes in fiscal 2012. Funding for the V-22, a tilt-rotor aircraft built by Boeing and Bell Helicopter, a unit of Textron Inc, would drop to $1.91 billion for 21 aircraft, from $2.8 billion for 35 planes in fiscal 2012. The plan foresees spending of $1.25 billion for six high-altitude unmanned Global Hawk spy planes built by Northrop Grumman - three for NATO and three for the Navy. Panetta announced last month that the Pentagon was cancelling work on the Air Force's Block 30 variant. The plan would increase funding for the AH-64 Apache helicopter built by Boeing by 55 percent, funding 40 remanufactured helicopters and 10 new aircraft. Northrop Grumman and Lockheed also have a big role in the program. Funding for the UH-60 Black Hawk helicopter built by Sikorsky Aircraft, a unit of United Technologies Corp, would continue a five-year procurement agreement with $1.3 billion for 59 of the twin-engine helicopters. GROUND VEHICLE BUDGET DROPS 32 PERCENT The Pentagon's spending plan includes $10.9 billion for ground vehicles, 32 percent less than the $16 billion requested in fiscal 2012. The new request includes $117 million for continued development of a new light tactical vehicle for the Army and Marine Corps and a heavier new Ground Combat Vehicle. Funding for the Family of Heavy Tactical Vehicles built by Oshkosh Corp would drop to $58.1 million for 1,534 vehicles from $650 million for 9,336 vehicles funded in fiscal 2012. Missile defense spending would remain fairly stable at $9.7 billion under the fiscal 2013 request, maintaining work on several air and missile defense capabilities such as the Patriot PAC-3 missile built by Lockheed. It would fund the MEADS joint program with Italy and Germany at $400.9 million, completing development testing. Shipbuilding programs would get $22.6 billion in the fiscal 2013 request, down from $24 billion in the fiscal 2012 request. That will fund 2 Virginia-class nuclear attack submarines, 2 DDG-51 destroyers, 4 Littoral Combat Ships and the first year of construction of a second new aircraft carrier. Space programs would get $8 billion, a drop of 22 percent from the $10 billion requested in fiscal 2012, due to fewer satellites and launches, and the cancellation of Northrop's Defense Weather Satellite System.
Section 2.5 starting on page 27 discusses "Autorotation" in detail, the procedures, probability, shortcomings, and training. It is an older document (circa 2001) but I would assume it is still valid as to describing the situation....and that suggested improvements in training, simulators, and NATOPs procedures have been made.
I may be getting old and worry about my mortality more than I used to do...but even at spending 30% of my flight time in a phase of flight where the lack of a viable auto rotational capability might prove deadly....it would give one pause for thought.
If it isn't 1600 feet....what does the H/V diagram look like?
I have no doubt that the V-22 has the ability to establish an autorotative descent. The report provided by SASless clearly states that, “that the probability of a successful autorotational landing from a stable autorotative descent is very low.” As a result the manufacturer implies that the recommend method of landing with both engines inoperative would be an airplane type glide to a touchdown to a hard surface. SASless, it sounds as it 30% is the best one might see. From my perspective nearly 100% of the time a viable autorotation is not a choice. An airplane mode glide to a touchdown gets my vote as the procedure of choice, if for no other reason than that it will provide a little additional time to sort out the situation while inroute to the mishap site.
If I had the time and interest I would go back through the thread and find the information John Dixson posted that detailed the Emergency Procedures and a discussion of the H/V diagram which showed a fair old height being required for the transition from Hover Mode into a No-Engines Operating Airplane Glide. It was startling to see how high one needed to be in order to achieve a proper Glide Speed and descent rate.
As the Marines say...it is not a helicopter....it is a tilt rotor and thus cannot be expected to autorotate like a helicopter.
Also...the odds of having a dual engine failure is quite remote....but possible as we all know about "Sod's Law".
The trick will be operating in the Hover Mode at heights lower than required to make that transition....where one cannot autorotate or go gliding....not that will ever happen mind you!
The difficulty of a transition from Hover Mode to an authoritative descent and landing must rather sporty as it is only done in the Simulator....and unless I misunderstand....it was not done in much detail during testing.
The other quote I found interesting is the Civil version has a different system for controlling the prop rotors angles and uses "Detents". I wonder why the difference and which system is the better? Could it be the Military froze the design in order to get into production and decided not to use the "Detent" method as Agusta has for the 609.
Venanzi said autorotation tests have been conducted at altitude, and that “it doesn’t take much altitude” to achieve a power-off full flair (sic) to a sink rate of zero fpm.
SAS (and everyone else), what Pietro Venanzi was obviously talking about there was the ability of the 609 to flare (correct spelling) to zero sink rate while already established in an auto. He's clearly trying to appease the critics who say the tilt-rotor cannot autorotate to a safe landing.
Presumably, a run-on landing in helicopter mode would be less risky than a forced-landing in King Air mode. Either way, the landing is going to be breathtaking! With regard to the former, imagine timing that flare? Hoo! But even King Air pilots don't practice dual engine failure landings in real life - probably not even in the sim. Then again, King Airs aren't often asked to hover.
However, one has to chuckle a little at Venanzi's clever use of that vague, "doesn't take much" phrase. Sooooo...how much is "not much?" And how much more "not much" would it take for the heavier V-22 to flare to zero fpm in an auto? Ah, semantics, gotta love them.
When it comes to engine failures, we know that the transition from hover-to-stabilized-auto or hover-to-airplane-mode is going to take up quite a bit of altitude. But let's dismiss the idea of having a dual engine failure while hovering and then transitioning to airplane mode. When would that ever happen? When would a V-22 be hovering high enough to even consider such a procedure?
On the other hand, if both of an Osprey's engines quit when it's cruising along up high, it becomes a bank safe with little stubby wings. Look for something soft to land on (hopefully near a hospital), not Interstate-10.
If you have a dual engine failure at the end of a flight when you're on approach and transitioned back to helicopter mode, you're pretty much screwed; we understand this. But you would have to be having a REALLY bad day. (Hopefully nobody would experience a dual engine failure on take-off.)
It's a compromise aircraft. Those who fly it (and fly in it) accept those compromises that come with the increased capability. They look at the instances of dual engine failures in existing multi-engine aircraft and they consider the risk of that particular emergency to be low enough to not worry about.
Osprey Driver.....found a reference to the 1600 Feet AGL number.
The proper wording should be "....following sudden dual engine failure or failure of the operating engine in OEI Flight....".
Indeed, the 2005 OT-IIG report itself says in reference to “emergency landing profiles following sudden dual-engine failure” that: “dependent on altitude, the aircraft flight manual directs conversions to airplane mode or autorotation.”167 Yet this report’s own executive summary states: “Emergency landing after the sudden failure of both engines in the Conversion/Vertical Take-Off and Landing modes below 1,600 feet altitude are not likely to be survivable. ... The V-22 cannot [author emphasis] autorotate to a safe landing.”168 A subsequent comment in the summary states: “Additional flight tests should be conducted to provide validated procedures for dual-engine failure.”169 Any volunteers? Clearly, safe engine-out landing is a major unresolved issue for the V-22.
Mr. Gaillard seems a bit unimpressed with the Osprey....and reading his paper does raise some interesting questions. One example that I just read....
the countermeasures dispensing system was found to have insufficient capacity for longer missions, and radar reflection from the V-22’s total propeller disc area of more than 2,267 square feet rivals that of two Boeing 707s in formation.146 (Given that situation, one can only wonder at the logic behind the development of top-secret “stealth paint” for the fuselage at a cost of $7,500 per gallon; the one aircraft they painted required 10 gallons for a paint job costing $75,000—but those huge, whirling discs were still there, bouncing back radar signals with gusto.)
God bless...I can't believe I'm in this discussion again.
To clean up some smaller issues...
"Detents." I'm not an expert on the 609, but to my knowledge, it doesn't have 0-97 degrees of nacelle settings selectable by the pilot, but only some key settings representative of certain flight regimes or speeds. This isn't a flaw in either design. Long story short, the military design allows for more flexibility on the part of the pilot. Some scenarios call for use of nacelles, e.g. big changes in airspeed. Some require nose attitude, e.g. small adjustments. The military environment is tactical, and thus more dynamic than the civil one. The civil "detent" concept is probably easier to fly, but takes some control away from the pilot. The Osprey can set 0, or 60, or 90 degrees or whatever, but allows intermediate settings as the situation requires.
The Osprey doesn't auto as well as a helo. It autos well enough. It is practiced in the sim. That's no secret.
It glides decently as an APLN, and that's the preferred regime.
In a line squadron, it spends the vast majority of its time in APLN.
As others have said, it's a compromise between a helo and an airplane. It takes strengths and weaknesses from both.
The Marine Corps and Air Force have both decided that in the final analysis, those tradeoffs make sense. I concur. There will always be the corner cases where it isn't better, but in the vast majority of flight regimes, it is more survivable than other platforms. As a 46 turned 22 guy, I'll tell you that there are a lot fewer "land immediately" EPs in a V-22 than a 46.
Of course the Marines do not want to discuss the Over The Horizion (OTH) issue as it cannot be defended with any reasonable basis. The concept sounds good...and if achieved would promise good results in budget battles against the other Forces within DOD.
In shrinking budgets of course Costs are important issues....again the Marines want to avoid the spotlight getting shined on the Osprey Program as it is a huge chunk of their budget.
Think what you want about the Osprey in operations it is fit for....but remember it was sold as being the answer to every mission conceivable which it plainly is not and never was.
When you pull out the stops to get your Program and keep your Program...and let yourself get carried away in that process....don't be surprised when a critical review finds fault with the advertising claims.
Now...with that being said....let's hear a Marine Corps summary of the OTH Strategy as it stands now...right now....and where has it been a success and where has it failed to meet expectations. What is the true capability of the USMC/USN re OTH. How many Billions have been spent...and what operational capability have they purchased? Did we (the US Taxpayer) get our money's worth?
I plainly think NOT! Did we get something...sure....but what and at what cost?
Osprey Driver and others that think highly of the Osprey are quite welcome to do so and have a basis upon which to make that evaluation. Likewise, as Professional Marines and probably readers of "Proceedings", "The Marine Gazette" and other DOD related professional outlets...they can form an opinion about OTH and its current status.
Perhaps some googling and quoting from those sources might lay out other informed evaluations.
No matter how one wishes to try....divorcing the Osprey Program from OTH is not reasonable as OTH was the driving motivation for the Osprey. In actuality, even if OTH is finally acknowledged to be a complete failure....the Marines will find valuable uses for the Osprey just not the one it was designed for and sold as being critical in need.
This article discusses the Expeditionary Fighting Vehicle (EFV) which was one of the three legs of the OTH Stool...the other two being the Osprey and the LCAC. If you take the time to read the article...compare the thrust of the argument to that of the Osprey program. Consider the EFV program was cancelled by DOD recently as it was a total failure....leaving OTH without a self deployable armored amphibious infantry fighting vehicle. The author politely evades the OTH discussion by stating it is beyond the scope of the article despite the impact success or failure of the AFV Program has on OTH.
Just as in the EFV Program....does not success or failure of the Osprey program not have a similar effect upon OTH?
Having instructed in Simulators at two different helicopter manufactures....I am curious about the techniques used by the USMC in their Sim Training. What scenarios are used to do the Autorotations? It is well briefed, well planned, and done as a stand alone maneuver....or do you mix it up so at times the need to autorotate presents itself as an unannounced emergency situation. Do you introduce the evolution as being a second engine failure after some OEI flight?
What percentage of authoritative landings in the Sim are successful...no damage to the aircraft or occupants? Does that success rate improve with practice?