What's the latest on tilt rotors?

[sprocket]

Scattercat,check out this thread on this forum (pprune)
http://www.pprune.org/ubb/NonCGI/For...ML/000289.html
or go to the "MV22 Osprey Accident Theory" on pg 2 of this forum....A bloke who goes by the user name "PTI UAE" has put some addresses on a couple of his posts. Or try emailing him at his "Profile address"

Good Luck

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Its a big thing..when you look into it!!

[flyerh]

The FAA are the only ones that have given this serious consideration,the CAA will probably wake up to the fact when one buzzes them at Gatwick. so far the FAA have said that if you want to be a captain after the factory coarse you will need a helicopter ATP and a multi engined fix wing CPL.
If you only have a ATP(H)you will need 500 hrs on type before you can be a captain.
This may all change though as the project progresses,I know I will be getting mine!

[PTI UAE]

Scattercat,

As far as I have heard, the only regulatory agency working with the FAA on certification and regulatory issues for tiltrotors is Transport Canada, although I would imagine that the Italian aviation authorities must be involved to some degree because of the Agusta participation. It appears that others are taking a ‘wait and see’ attitude, and are not participating directly in the process. I’m sure they will have access to all of the certification data etc. to use in developing their own regulations, and they will have the FAA and Transport Canada established regulations and procedures to use as a baseline. If the other agencies delay too long, it could create difficulties for a number of operators that plan on flying 609s in Europe, Australia etc. The following will provide you with an update on the current plans by Bell for certifying tiltrotor pilots and engineers.

In order to be admitted into the Bell training program, they require that you have three ratings: helicopter, airplane and an instrument rating in EITHER one. This is a BHTI requirement to enter the BA609 Pilot Qualification Course, not an FAA requirement. The program is scheduled to be four to six weeks in duration, and will include a minimum of 24 hours of simulator time and initially 15 hours in the aircraft. The time in the a/c may be reduced later based on observed performance by early participants in the program. It is a proficiency-based course, so additional time may be provided on an individual basis as needed, and obviously nobody will pass unless they meet the performance guidelines. The purchase of the simulator has been fully funded (initially Level ‘C,’ then later to be certified as Level ‘D’), and will be set up in the combined Pilot and Engineer Training Center being built at Alliance field in Texas.

I received some clarification from Bell on the specific type of license and ratings needed to qualify for a commercial/instrument powered lift (Part 142):

When seeking a Commercial/Instrument Powered-Lift rating, you DO NOT need to have a commercial license for BOTH categories. You must have a commercial (CPL) issued for one or the other, EITHER airplane OR helicopter (as is the case with the instrument rating). So having a commercial-helicopter, and private-aeroplane (or vice versa) is sufficient.

A multi-engine rating is NOT a mandatory requirement, although it is strongly recommended. A single-engine land rating is acceptable. It was also stated that although experience with pressurized aircraft is preferred, it is NOT mandatory.

Requiring the powered-lift candidates to have airplane, helicopter, and instrument ratings have helped BHTI gain approval for the reduced training hours under Part 142. Part 61 requires 72 hours, and Part 141 would likely require 40 to 50 hours. In order to qualify for a Powered-Lift ATP you would need to complete the Bell course for Commercial/Instrument, then accumulate 250 hours as PIC in tiltrotors along with the other requirements detailed in FAR Part 61 which would then make you eligible to take the check ride.

At this point Bell says it appears likely that the training slots allotted for each aircraft sold by BAAC will be 2 pilots and 3 technicians although we would like to see higher numbers.

The engineer/mechanic course is expected to be 3 weeks long. Each technician may attend 3 maintenance slots, or 3 may attend one of the following:

Field Maintenance Course - (4 Wks)
Line Maintenance Course - (2 Wks)
Electrical Maint Course (2 Wks)
Flight Control Maint Course (2 Wks)
Integrated Avionics Maint Course (1 Wk)

The above info. Is not yet set in stone, but it is what Bell is using as their basic guidelines at this time. Below is a statement issued by Joel Brown, the Supervisor of Tiltrotor Training at Bell.

************************************************************ *********

BA609 Pilot and Maintenance Courses

We are in the process of developing the BA609 Pilot Qualification Course
curriculum. The course will be validated via internal training for our company test pilots, instructor pilots, and pilots from the FAA Certification Office & FAA Flight Standards Service.

After first flight and during flight test, we will update the curriculum for customers who will be operating the BA609. The BA609 Pilot Qualification Course will be offered to support issuance of FAA Powered Lift Private, Commercial, and Airline Transport (ATP) ratings, in conjunction with BA609 Type Certification. This course will include academic, Full Flight Simulator (FFS), and flight training. The course length is not yet set, but may range from 4 to 6 weeks and include approximately 30 to 40 hours combined FFS and aircraft flight time.

Customers must meet the prerequisites of Airplane/Helicopter dual rating and a commercial certificate with an instrument rating in either category prior to attending the BA609 Pilot Qualification Course. Additional training will be available for applicants who do not meet course prerequisites. The Bell Agusta Aerospace Company (BAAC) or BHTI will provide this training for a fee, or assist the customer in obtaining it from another source.

We expect to begin training customer pilots shortly after aircraft type certification. Initially, training slots will be limited and the priority will go to:
1st: BA609 customers to be trained in conjunction with a new aircraft delivery.
2nd: BA609 Operator Customers requesting training at own expense.
3rd: Other Customers requesting training at own expense.

Additional courses will be offered to support issuance of FAA Powered Lift Instrument, Certified Flight Instructor (CFI), and Certified Flight Instrument Instructor (CFII) ratings in the BA609. Refresher Courses will also be offered in each of these categories.

The following maintenance courses will be developed and offered to customers to support maintenance of the BA609: Field Maintenance, Line Maintenance, Component Repair and Overhaul, Electrical Maintenance, Flight Control Systems Maintenance, and Integrated Avionics Systems Maintenance. In addition, Bell will update the existing BHTI Composite Repair Course to include unique BA609 structural repairs.

At this time, the prices for BA609 courses have not been established.
************************************************************ *********


[This message has been edited by PTI UAE (edited 25 August 2000).]

[HeliFlight]

PTI UAE:

EXCELLENT post (as usual). This is exactly what those of us interested in the Tilt Rotor are looking for! I'll definitely circulate this around. Please keep us updated. Thanks

[Scattercat]

Thanks for the exellent info' PTI UAE. Sorry it's taken so long to get back. (I've been out of the loop for a couple of weeks).

[Cyclic Hotline]

Another MV-22 lost.

Tuesday December 12 10:03 AM ET
Marine Corps Osprey Suffers Another Fatal Crash

By Charles Aldinger

WASHINGTON (Reuters) - The Marine Corps faced new questions Tuesday about its tilt-rotor MV-22 "Osprey'' aircraft after one crashed in North Carolina Monday night, killing three marines and leaving a fourth missing and presumed dead.

No cause was immediately determined for the accident in a wooded area north of the Marine Corps New River Air Station in southeastern North Carolina. It was the second fatal training crash this year of the revolutionary MV-22, which uses rotating wingtip engines to take off and land like a helicopter.

The Navy recently postponed for several weeks a decision on whether to go into full-scale production of the first of 360 MV-22s, built by Boeing Co. and the Bell Helicopter division of Textron Inc., after a Pentagon (news - web sites) report criticized maintenance problems in the aircraft.

That initial production contract to be signed next spring would be worth up to $1 billion for 20 aircraft. But the long-range value of production could be $30 billion including sales to the Marine Corps, Navy and Air Force Special Operations.

The Marine Corps itself plans to buy 360 of them at a cost of more than $44 million each, although a recent report by Philip Coyle, the Pentagon's director of test and evaluation, worried that the cost could escalate sharply.

Another of the hybrid helicopter airplanes crashed on a training mission in Arizona last April, killing all 19 marines on board. That crash was blamed on pilot error.

Defense Of The New Aircraft

The MV-22 is designed to replace the Marine Corps CH-46 medium-lift helicopter first bought in 1964, and both the Pentagon and Marine Corp recently defended the new aircraft despite Coyle's report.

Monday night's crash occurred during a training mission, the Marine Corps said.

Rescuers reached the crash site in a heavily wooded area about 10 miles (16 km) north of the Marine Corps New River Air Station in the southeastern part of the North Carolina.

Marine spokesman Capt. James Rich said rescuers located the remains of three crewmembers but were unable to immediately identify them, and were searching for the fourth.

The crewmembers were Lt. Col. Keith M. Sweaney, 42, from Richmond, Va.; Maj. Michael L. Murphy, 38, from Blauvelt, N.Y.; Staff Sgt. Avely W. Runnels, 25, from Morven, Ga.; and Sgt. Jason A. Buyck, 24, from Sodus, N.Y.

The aircraft belonged to the Marine Medium Tiltrotor Training Squadron 204 based at New River.

Coyle said in his recent report that the MV-22 was effective for its intended mission of delivering Marine troops ashore. But he said there were troublesome and potentially costly maintenance problems.

"I don't agree that the V-22 is a troubled program ... it is a maturing program,'' Marine Brig. James Amos told reporters on Nov. 30 in response to questions about the Coyle report.

Both Pentagon spokesman Ken Bacon and Amos, deputy director of aviation for the Marine Corps, stressed at the time that while there are always maintenance problems with new aircraft, those are ironed out and fixed over time.

Amos said problems with attaching cables and wires to the carbon airframe of the V-22 had been fixed along with some initial difficulty in folding the propellers and wings to make the aircraft better fit aboard navy launch ships.

"In terms of the costs of making the plane operate, the costs of keeping the plan operating, it (the Coyle report) does conclude that they could be lower,'' Bacon said.

"And the Marines are confident that the costs will be lower, and that they will get lower as they begin to get this into the force and they begin working on the plane.''

[212man]

Sad news. To put it in perspective though, what is the 'normal' accident rate that the US Army/USMC experience in night training? I gather it is quite high (in absolute numbers, not necessarily relative to the high hours flown).

Things don't auger too well for the '609 though, I guess it must raise questions of confidence in the basic viability of the thing.

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Another day in paradise

[HeloTeacher]

It hasn't shaken my confidence, but unfortunately the common man on the street who isn't aware of the operating environment, newness of the design, or of the nuances of VTOL flight will carry the fear of tiltrotors long after this incident is put to rest.

We will have that much more work cut out for us later on...

[widgeon]

If you want to check out a particularly nasty thread on this see rec.aviation.rotorcraft , there is an almighty pissing match going on between the Bell Boeing and Sikorsky supporters.
Condolences to all close to the victims.

[HeliFlight]

You are right 212 man, we must keep it in perspective. The F117 crashed twice in one year, and it went on to have the most lethal accuracy rate of any aircraft in the Gulf war.

Fortunately I don't think it will have much impact on the 609 program because they are so far from first delivery. The newly announced schedule shows that customers won't be seeing them for over three years (1st quarter of 2004). But for the V-22 program it's real bad news. The pentagon was just about to decide on whether to go into an accelerated acquisition rate. The Marines are completely confident in tiltrotor technology after over 10 years of test flying it, but they won't be getting them as fast as they would like to.

[Lu Zuckerman]

Assuming that the mechanical and electronic systems are 100% reliable the major problem with the V22 is reparability. When I worked on the program, I had to assess the maintenance actions that would result from the failure of every composite structural element in the aircraft. In all of my years in the business of Product Integrity this was the first time I had to deal with structure. It seems that the US Navy is the only military service in the States that has elected to use this option of the specification governing the preparation of Failure Modes and Effects Analyses (FMEA).

Since the structural elements were made from composite materials they had no natural or generic failure modes. This meant that the only means of failure of function was to consider external mechanical forces that would cause structural failure. The way the V22 is constructed the entire back end was made of one-piece construction and all of the internal structure was attached to the tail section by clips.

If in fact the external force caused structural deformation or failure of the part under analysis the force necessary to cause the damage had to pass through the outer shell which is one piece. Although the predicted rate of occurrence was minimal it could be shown that the overall availability would be seriously effected. The very nature of the construction of the back end was that the repair had to be made under the same conditions as those used in the manufacture of the back end. This meant that they had to have a very large number of spares at the second level of maintenance or the entire back end had to be shipped back to the factory or overhaul facility.

Another problem (at least at that time) was the Navy had only one approved method of repairing structural composites. After completion of the repair the entire damaged area had to be X-rayed.
The problem was that the repair material was opaque to X-rays and the efficacy of the repair could not be determined.

The analytical approach to the damage process only considered external force trauma. Battle damage or, hard landings or being hit by a Stinger type missile were not considered. So when this composite monster gets down and dirty with the grunts it will be wide open to ground fire of all types and landings on unprepared strips will also take its’ toll. When it has returned to the Assault Ship it will most likely not be able to be repaired and as the assault goes on the attrition rate could be 100%.

I personally don’t think this part of the operational process ever got much thought.


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The Cat

[Tricky Woo]

As always, Lu Zuckerman, you continue to surprise me as your deep involvement in some amazing projects...

However, while you raise some valid points as to the long-term viability of the airframe under harsh conditions, I think that the US Marines are going to be more concerned as to why two Tilt-rotors have fallen out of the sky in only a few months.

More development required?

[offshoreigor]

My condolences to the families.

I don't think we should be making such comparisons between the V-22 (Military, doing a military job) and the Bell/Boing 609 (Civilian offshore/Ambulance flying).

I think you could look at any type in the world that is both military and civilian and you would find similar accident rates weighted against the military. The nature of the job has certain built in risks that would be totally unacceptable to a customer in the civil aviation world.

I don't think the V-22 loss rate will affect the 609 program unless it too experiences similar losses.


Cheers, OffshoreIgor

[212man]

I tend to agree, and to add to my earlier point: look at the Apache losses in Kosovo (well, they didn't actually get to Kososvo, but let's not rub that in!). Night training at low level is inherently risky and the accident rate bears that out. What I was trying to say was that it's 'perceived' viabilty by the buying client may be damaged. If they see hidden software or mechanical problems lurking and waiting to give them a headline grabbing bite, they may back off slightly from buying it.



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Another day in paradise

[Lu Zuckerman]

To: Tricky Woo

I agree that the solution to the two crashes is paramount. However, the main reason that the V22 exists was that the Marines convinced the US Congress that the V22 was extremely reliable. If for a moment you could look at the V22 as a tandem rotor helicopter that can fly like an airplane they took comparitive reliability histories and proved the reliability of the V22 because they said it was made mainly of composite material which under all applications had proven to be more reliable than aluminum structure.

They said it was resistant to corrosion, it was resistant to exfoliation and it had a longer life than metal structure. When you manipulate the numbers in this way it is easy to prove your point.

This aircraft is far more sophisticated than a CH-47 and as such is subject to a lot of failures that would cause loss of the aircraft. In the design they tried to design out all single point failures but obviously they didnt.

One V22 was lost because they didn't take into consideration that flammable fluids could leak into the engine nacel and catch fire. A second V22 was lost because the flight control system and associated computer systems were miswired. Now, they have to determine what caused the last two crashes.

In my post above I eliminated mechanical failure and only addressed structural damage which could seriously effect the availability of the V22 Fleet. The mechanical and electronic problems will also add to the unavailability.

Regarding the Arizona crash which was blamed on too rapid a desent you may have read my previous posts on Just helicopters and possibly here on PPRuNe where I said that the V22 and the 609 were being certificated as a powered lift aircraft and there may be no requirement to demonstrate autorotation.

In those posts I indicated that a Boeing Engineer told me that the autoration decent speed was 4-6000 feet per minute. He may not have been autorotating when he crashed but it was said that the pilot was decending at to high a rate. Just imagine what will happen if the V22 has to autorotate and he does not have time to make a run on landing as an aircraft. They will have to install airbags in the seats for pilots and passengers.

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The Cat

[Cyclic Hotline]

The accompanying article details a couple of pertinent aspects of the seriousness of this accident, not only in it's timing, but also politically.

• The aircraft was returning from a night landing training mission when the accident occurred. The crew issued a Mayday prior to the crash.
• The aircraft commander was the chief of the test programme and was to command the first operational squadron.
• The final build decision was to be made next week, and is being postponed until a full review is complete.
• All of this is occurring during a change in Presidential administration.
  Dick Cheney (under the previous Bush administration} cancelled the programme, only to see it reinstated by the current administration!

Regarding the potential effects upon the AB609 (or other tilt-rotors), they must be considered significant. The manufacturers had envisioned generating considerable operational experience with the military programme. This allows a significant number of aircraft to be proven in the field and the identification and rectification of potentially hazardous conditions prior to an adverse condition occurring on a flying machine.

If the V-22 programme should be curtailed or cancelled, it might prove to be difficult for the operators to convince the customerthat the aircraft can be operated safely. This is certainly one of the highest priorities of anyone operating utilising,or insuring helicopters. Just look at the history of commercial helicopter operations, and the traumatic times that virtually every type has experienced, principally, but not limited to, the inception of service.

In the early operational stage of a new type, every flight is an exploration ito unknown territory. Every component and system is being exposed to the realities of operational, environmental and practical maintenance experience. This trend continues until the overhaul and life-limit cycle is completed and the knowledge from experience can be quantified. (The complexity of the Marine version of this machine must be seen to be believed - it is amazing.)

The secondary stage is the replacement of parts due to overhauls, life limits, maintenance related removal, or failure. In this stage the growth from experience continues during component overhaul. It also continues with the replacement of original parts with new, improved, or modified parts. There always remains the possibility that modifications or alterations may compromise the integrity of the original design, for a variety of reasons, including environmental conditions, corrosion, manufacturing defects, etc.

The tertiary stage is the mature aircraft, where the predictabilty and reliabilty of parts can be accurately forecast. The performance and envelope is known and understood. The maintainability of the aircraft is proven, and identifiable defects have been remedied. At this stage the longer term effects on airframes and non-removed systems become apparent. Skin and airframe fitting corrosion, flight controls and electrical wiring become primary areas for maintenance activity and inspection. There continues to be the risk of manufacturing production, material, or process defect in replacement parts during this phase, which may create previously unknown problems to occur. On condition items may ultimately display failure rates that determine appropriate action be taken to intercept failures.

The problem for any product is to successfully transition from each of these stages to the next. If you consider the commercial helicopters curently in the marketplace and the path to success from certification, the process is anything but predictable, and there is a real possibility of failure at each and any stage. At one point you couldn't give an S76 away, likewise the failure and removal of the BV234 Chinook from offshore support, is related directly to customer decisions not to utilize these aircraft (applies to other products also). The Wessex was withdrawn from service overnight, by the sole commercial operator of the model. When reliability and safety are not to acceptable and predictable standards for commercial operation, the customer walks away from the product and the operator is left holding the bag!

These are not theories, but proven experience in the helicopter (and aviation) world.
A couple of examples:

• Sikorsky S61. Main Rotor Spindles,(Process, Design, Corrosion). CT58 Engine Turbine wheels (design and manufacture).
• Sikorsky S76. Main Rotor Spindles, (design, process). Main rotor mast (current). Allison C30 Engine (Engine lube system)
• Boeing Vertol BV234. Forward Gearbox (design, corrosion)
• Eurocopter AS332. Main transmission (design, materials). Main Rotor Spindles, (design, materials).

This could be a long list, Bell models, A-stars, Lycoming 101 engines, Allison 250 series engines, the Westland W30, but I'm sure you have the picture.

For the MV-22 and the tilt-rotor concept as a whole, the near future will hold some tremendous challenges. I am not suggesting the programme will not succeed, simply that the path ahead, is anything but clear, and the scrutiny the programme is attracting may affect it's marketability in the initial stages.


Marines Ground Osprey Fleet

By ROBERT BURNS, AP Military Writer

WASHINGTON (AP) - The Marine Corps' chief of aviation says the crash of an MV-22 Osprey in North Carolina should not be a "show stopper'' for the troubled $40 billion program. It appears increasingly likely, however, that it will be up to the next administration to decide whether to build a full fleet.

The Marines now plan to buy 360 over the next 14 years to replace aging helicopters. Three of the first 15 delivered - including prototypes and experimental models - have been involved in fatal crashes, including two this year that reduced the fleet of operational models from 10 to eight.

Four Marines were killed in the crash Monday several miles from Marine Corps Air Station New River, near Jacksonville, N.C. The four bodies remained at the scene Wednesday morning. The $43 million aircraft burst into flames upon crashing in a heavily wooded area.

The Pentagon (news - web sites) grounded the aircraft, and Defense Secretary William Cohen planned to appoint a panel of outside experts to review Osprey performance, cost and safety issues.

The tilt-rotor Osprey takes off and lands like a helicopter but flies like an airplane. Built by Boeing Co. and Bell Helicopter Textron, it is a linchpin of the Marine Corps' aviation future. The Air Force also plans to buy 50 of the aircraft, which have the potential to be adapted for a wide variety of missions.

Lt. Gen. Fred McCorkle, head of Marine Corps aviation, told a Pentagon news conference that the Osprey had been conducting night landing practices and was returning to New River when the pilot issued a distress call at 7:27 p.m. That was the last word from the Osprey before it crashed about seven miles from the base.

"Whatever is wrong with it - or if there was something wrong with it that caused this accident - we plan on finding out what it was and fixing it,'' the three-star general said. He said a flight data recorder had been recovered intact, but there was no immediate indication of what caused the accident.

McCorkle said he remained confident in the Osprey, despite the second fatal crash this year.

"I don't think this will be a show-stopper,'' he said, referring to the possibility of the program being canceled.

The Marine Corps already has spent $10 billion on the program.

If George W. Bush (news - web sites) is the next president, he will bring to Washington the man who tried unsuccessfully to cancel the Osprey program billions of dollars ago - Dick Cheney (news - web sites), who scratched the Osprey from the Pentagon budget shortly after he became secretary of defense in 1989. Congress put it back.

The Navy Department, which has responsibility for naval as well as Marine Corps programs, had been expected to make a final decision this month whether to approve moving the Osprey into full-rate production. On Tuesday, the day after the Osprey crash, the Marines asked that a decision be put off indefinitely.

The Marines had hoped to get the go-ahead for full-rate production this year and to field the first operational squadron next year.

Defense Secretary William Cohen, a supporter of the Osprey, is going to appoint a panel of technical experts to review the entire Osprey program, spokesman Kenneth Bacon said Tuesday. The review will focus on safety, performance and cost issues in light of Monday's crash and other issues.

Lt. Col. Keith M. Sweaney, 42, of Richmond, Va., the pilot of the Osprey that crashed Monday, was to become commander of the first Osprey squadron. He was chief of the Osprey testing program and had recently briefed top Marine Corps and Navy leaders on the aircraft's performance and suitability.

The three other victims were identified as Maj. Michael L. Murphy, 38, originally of Blauvelt, N.Y. and most recently of Wilmington, N.C.; Staff Sgt. Avely W. Runnels, 25, of Morven, Ga.; and Sgt. Jason A. Buyck, 24, of Sodus, N.Y.

Before becoming a test pilot for the Osprey, Murphy spent three years as one of the pilots flying President Clinton on the Marine One helicopter.

In April, an Osprey crashed in Arizona, killing all 19 Marines aboard. That stirred questions among the victims' families and in Congress about the Osprey's safety. The aircraft were grounded until June, and this fall, after more testing and evaluation, the Marines declared the aircraft to be "operationally suitable.''

At a news conference Tuesday, McCorkle, the Marine Corps aviation chief, expressed sympathy for the families of the latest victims.

He said the accident investigation board will be headed by a general officer - a more senior official than normal - indicating the seriousness of the problem.

"We want to make sure everyone knows that this is not `business as usual,''' McCorkle told reporters. "This program is very, very important to the Marine Corps, to me and I think to the nation, and we're going to work very hard to find out what happened.''

[This message has been edited by Cyclic Hotline (edited 14 December 2000).]

[HeliFlight]

Tricky Woo & Lu (that rhymes!),

There is no mystery about the Arizona crash that occurred in April. That accident was investigated and closed by the Marines, the manufacturers, and an independent investigation by NASA. They all came up with the same conclusion: pilot error. The pilot in the lead a/c lost his wings after the investigation. The V-22 developed settling with power due to a rate of descent in excess of 2000 fpm at 285 ft AGL! There was a quartering tailwind, 2100ft elevation, and 28 deg C. The pilot violently pulled full aft on the stick, rapidly decreasing a/s and developed the inevitable vortex ring state. Because of the unique side by side rotor configuration, it developed 'asymmetrical’ settling with power. If the wind was directly on the nose or tail, it would have been 'normal' settling with power, but it doesn't matter, they would have all been killed regardless. If you put a CH-46 in the identical scenario, the result would have been the same.

Look at the thread at <A HREF="http://www.pprune.org/ubb/NonCGI/Forum11/HTML/000289.html" TARGET="_blank">http://www.pprune.org/ubb/NonCGI/Forum11/HTML/000289.html</A>
This was the incredible discussion that started off slamming tiltrotor technology, and by the end, when the true facts were presented, it turned around into a positive discussion.

Lu is right about the other accidents. In the 11 ½ years it has been flying, there have been four V-22 accidents, three of them fatal. None of them though showed tiltrotor technology to be flawed. It seems that all of them could have been anticipated and prevented though.

Accident 1 (Jun 91): Miswiring of two of the three lateral cyclic inputs, crashed on first flight in a hover (no fatalities). Should have been caught by quality control at many levels.

Accident 2 (July 92): Ingestion of transmission fluid during transition to H-C mode. A simple drain hole could have prevented it.

Accident 3 (Apr 00): Pilot Error (see above).

As far as accident 4 (Dec 00), – the black boxes will tell. In the mean time, the press will have a field day slinging mud at the military as they always do (see Cyclic Hotline's post).

The bottom line is it’s not the technology that’s flawed, and 4 accidents of a military a/c over 11 ½ years is not out of line with what has been experienced with other a/c. As 212man said, we need to keep it in perspective..


[This message has been edited by HeliFlight (edited 14 December 2000).]

[This message has been edited by HeliFlight (edited 16 December 2000).]

[UNCTUOUS]

Subject: V-22 Settling Problem Disclosed, Navy Claims It's Unrelated ToMishap


Inside The Navy
August 21, 2000


V-22 Settling Problem Disclosed, Navy Claims It's Unrelated To Mishap

An audit of the V-22 Osprey program by the Pentagon's inspector general reveals officials knew a year ago the tiltrotor had a problem with "settling due to loss of interim power" but decided the deficiency was not important enough to immediately spend money correcting it.

The report discloses for the first time that military testers identified a specific settling deficiency associated with the V-22 last September, and Osprey program officials labeled the problem "nonmajor" and not worth fixing before the start of operational testing and evaluation, the phase in which Marines were participating at the time of an April 8 crash that killed 19 Marines. Such deficiencies are valid but do not restrict the V-22 from meeting its mission, the audit report says.

V-22 program officials told Inside the Navy last week the problem is minor and not related to the phenomenon called power settling that is believed to have contributed to the fatal April 8 Osprey crash.

The Marine Corps and the Defense Department have a lot riding on the V-22, which operates like a helicopter for takeoffs and landings and, once airborne, converts to a turboprop plane. The Marine Corps is buying 360 of the aircraft and the Air Force is buying 50. Defense Secretary William Cohen has predicted all of the military services will one day rely on tiltrotor technology. A team of Bell Helicopter and Boeing builds the high-profile V-22.

At press time, the V-22 program office told ITN in brief comments the settling deficiency is not related to vortex ring state, nor related in any way to the mishap, even though the words used in the DOD IG report to describe the problem echo terms used to explain the fatal April 8 crash.

"Interim power is selectable by the pilot and provides for additional rotor thrust and power margin up to mast torque values of 109 percent at a rotor speed of 103.8 percent Nr," the program office said in a written statement to ITN. "By design, interim power is deactivated at nacelle angles less than 80 degrees or airspeeds greater than 50 knots."

ITN has learned that V-22 pilots who fail to observe certain airspeed and rotor-angle rules can lose interim power, causing the aircraft to settle without warning. While this concern was noted by military testers, Rear Adm. John Nathman, then the Navy's top aviation requirements official, said last September the program could proceed to operational evaluation without immediately fixing the problem. Officials maintain this issue is not a serious safety concern. The Navy's response to the DOD IG report,
published with the audit on Aug. 15, claims the deficiencies described are "in no way safety related."

For months, the Marine Corps has publicly dismissed the possibility that the V-22 might be especially susceptible to the vortex ring state.

"No, absolutely not," Lt. Gen. Fred McCorkle told reporters on May 9 when asked if there was is any evidence to suggest the V-22 is more susceptible than other rotorcraft to power settling or settling with power. McCorkle, the assistant commandant for aviation, said he believes the V-22 is less susceptible to such conditions when compared to other helicopters. "In fact, I would say [the V-22 is] less [susceptible] because of the amount of power that it's got." That day, McCorkle also said the mishap investigation was "concentrating on flight characteristics which are not peculiar or unique to the V-22 but can be experienced in all our helicopters . . . or any others in the world."


The Marine Corps concluded the mishap aircraft was piloted into a descent that was too rapid and steep. That flight induced the "vortex ring state" or rotor blade stall, which caused an asymmetric loss of lift of the rotors, the service announced. The pilots of the two aircraft involved were deemed responsible for the mishap and those from the surviving aircraft were disciplined.

When the Marine Corps Judge Advocate General investigated the recent Osprey tragedy, it concluded the mishap did not appear to be a result of any design, material, or maintenance factors specific to tiltrotors, but the JAG noted it is relatively unusual for the contributing factors in this mishap to cause the loss of a helicopter.

"It's primary cause, that of a MV-22 entering a Vortex Ring State and/or blade stall condition is not peculiar to tiltrotors," the JAG report states. The contributing factors to the mishap -- a steep approach with a high rate of descent and slow airspeed, poor aircrew coordination, and diminished situational awareness -- are also not peculiar to tiltrotors, the report continues. "However, the end result, departure form controlled flight, is more extreme than results experienced in most rotorcraft to date," the JAG report concludes.

When the service released copies of the JAG report, the opinions and recommendations sections were deliberately omitted, leaving unresolved key questions about their contents.

It is well documented that the vortex ring state is powerful and dangerous enough that pilots of rotorcraft caught in the unstable flight condition can lose control of aircraft if they fail to take proper action. Rotorcraft caught in the state require an unusual amount of power to maintain rotor thrust. The term "power settling" comes from pilots' observations that in some cases a helicopter keeps coming down even though full engine power is applied, according to "Practical Helicopter Aerodynamics" by R. W. Prouty.

The V-22's settling problem is one of the "nonmajor" deficiencies referenced in the Naval Air Warfare Center's integrated operational assessment, which was completed on Sept. 20, 1999. The NAWC report, which said major tests planned for the V-22 were not completed, identified limitations in major operational effectiveness. Additional testing would be needed to resolve certain critical operational issues, the NAWC concluded. However, fixes would not be in place to support operational evaluation testing. NAWC recommended various flight envelope and mission limitations, and prohibited maneuvers and operations for operational evaluation testing. However, despite the limitations, that report recommended the V-22 proceed to operational evaluation testing.

Some key Osprey problems -- such as those concerning the cargo handling system and protection from nuclear, chemical and biological agents -- were given high priority and the program office made plans to correct them during operational testing, the report indicates. Other deficiencies, including the settling problem, were dismissed by the program office as lesser issues, according to the DOD IG report.

The V-22 program office believed it "did not need to delay operational test and evaluation or to commit scarce program resources" to correct the settling deficiency before operational test and evaluation, the report states.

Pentagon spokesman Rear Adm. Craig Quigley spoke generally about the V-22 audit on Aug. 17.

"Let me just say everybody wants this system to work properly," Quigley said. "It is in everybody's interest that a good, tough review of the program at all levels be conducted. But as with any other new aircraft development program, there are going to be bugs in it."

Quigley said the Pentagon looks forward to rigorous testing and reviews of the V-22 program to find bugs, "so that those responsible for the program can work out a plan to correct them and come to an aircraft that will serve our military well for many years to come."

The admiral said reviewing and fixing problems with the V-22 is not something officials are shying away from. "We welcome the closest possible scrutiny of the program at all levels, so that we can all work towards a good aircraft that's safe and reliable and affordable and meets all of our criteria by the time it's put into the field," he said.

-- Christopher J. Castelli

[UNCTUOUS]

Lunch this week with Tom McDonald after the RAEs Lecture that Tom gave (as part of Farnborough). They are very apprehensive about the "settling with power" situation for a number of reasons (which I'll address shortly). So no-one should expect the Farnborough display by the V-22 to include much of a "wringing out". The draft GAO Report, of which I have a copy thanks to an insider, indicates a distinct reluctance to refer to more than a "power settling problem". It does not mention Marana nor AsymmVR (per se) and hides the sole reference amongst many other quite innocuous house-keeping style engineering underway fixes. It's this report that will decide the October go-ahead on production. So it would seem that they are still in denial and I can understand that after all the time, effort and expense.
McDonald offers no excuse for the exclusion of VR or AsymmVR from the FlightTest Program. As I have pointed out before, much of what should have been done in wind-tunnels was achieved parametrically via high-speed computation and the VMS (vertical motion simulator). I'd have thought Blind Freddy could have picked the flaw in this approach - however no-one did.
There were other reasons for it. Just like simulator time, actual blowing wind-tunnel time was at a premium so they had to go over and use a Dutch Tunnel for essentials. It was also a fact that commercial pressures related to noise certification for the FAA of the 609 changed all their priorities for testing somewhat. Whatever, it all fell through the cracks.
McDonald showed slides of a V-22 in a frightening momentary &gt;40 deg AOB towards the island during its flight-deck trials. It was the only one of 330 deck approaches that came unstuck. Theory now is that it wasn't really the PIO that it was then ascribed to, it was a transient settling condition (i.e. AsymmVR) caused by transitting the bad air abaft the ramp. It's quite possible depending on carrier speed and relative wind to get quite bad transitory turbulence effects (from the island) just behind the ship.
Normally an F14 or such-like is quickly through such turbulence but an Osprey is at a low IAS and quite vulnerable at that stage. Perhaps it's why all the Harrier approaches terminate abeam their spots and they then cross the deck sideways to alight. Of course a transient condition caused by bad air is much different to the ingrained condition caused by self-induced flight parameters entering the VR envelope.

I assume you are not PTI-UAE. I was becoming quite bored with the exchange with him simply because he wasn't addressing the issues directly. I found his come-backs very trite. He obviously has a vested interest. However I have had quite a number of emails asking for a response/further input so I may do that soonish - time permitting. I imagine that (from your address)
your company can see itself getting necessarily involved in the 609 and has become a "stake-holder" so to speak. I myself am quite supportive of the project but the admissions by McDonald plus some other project insights that I've had (Pentagon level and USMC) make me very wary that suppression of genuine concerns about the basic concept has become the order of the day.
Only time and a concerted effort to define the safe flight envelope will prove me wrong. Defining a safe flight envelope and providing an acceptable buffer zone without unduly limiting the V-22 will be a huge challenge. In other words, Marana is eminently repeatable - notwithstanding any errors that may have been made by the lead ship or the accident crew.

If you were to ask me for a solution I would offer up increasing the number of blades and going for greater disk solidity. That tends to cut down the vortex size, intensity and delay the VR threshold. McDonald agreed that they do need a fix of some sort that will take care of the incipient condition. But I'm betting that that will not become any sort of priority until after the next accident. Some correspondents have asked me why it's of any greater concern than the wing drop that you get at the FW stall. My easy answer to that is that anyone with any situational awareness can tell that he's near that stall and can take normal stall recovery (including some rudder to halt the further wing drop). As he adds power and unloads, a FW pilot will fly it out and the asymmetry will have been of no great concern (except in an accelerated "g stall" involving a "flick" roll -
but that should never be the case near the ground). The Marana accident did involve something akin to a "flick" roll, it always will. The instinctive corrective action (differential collective applied laterally through the cyclic to pick up the dropping wing) is the one thing that is always going to greatly exacerbate the condition into a rapidly terminal roll. So if we simplistically take the MV-22B at Marana (as a function of total V-22 flight hours to that date) or the 1/330 deck approaches and extrapolate this across a 400 aircraft military fleet, I calculate a loss at about every 12,700 hours of Mil V22 flight hours (in a fully mature fleet circa 2007)- about four times a year to AsymmVR. Whether this will be acceptable or not as an attrition rate remains to be seen. Because it's a people carrier it's not really the same as losing an F16 every so many flight hours. After a few accidents, Marines will have to be boarded at gun-point.


This is just a quick note and I have other thoughts on the subject so if you
have any response, criticisms or inputs I'd be glad to receive them. Perhaps
you'd like to address them on that same thread on Pprune.

regards


&gt;From: [email protected]
&gt;To: [email protected]
&gt;Subject: Vortex Ring
&gt;Date: Mon, 10 Jul 2000 14:10:04 EDT
&gt;
&gt;Jim -
&gt;
&gt;Back on May 16, you provided us with an interesting perspective on "That
&gt;Vexing Vortex Ring." Is there any more recent information that would cause
&gt;you to expand upon or change the theories expressed in that communication?
&gt;
&gt;Many thanks.
&gt;
&gt;Rhett Flater
&gt;AHS Executive Director

[UNCTUOUS]

It's not likely that this latest MV22 accident was Asymmetric Vortex Ring
(asymmVR). They have been having troubles with the cross-ship drive-shaft
couplings that link the two rotors (and that were designed to resolve the
problem of engine failures i.e. the power-plant itself).


However transmission failure, drive-shaft, couplings etc are not the V22's
biggest potential failing. These are hardware problems and not "designed
in". The asymmVR problem is such that, once encountered, it is a fatal
conclusion. As far as I know, nothing that has been done or trialled during
the months of recent proving flights at Patuxent River have circumvented
this fact of life. Recovery is possible, recognition and height permitting,
in a normal helo but the unsubtle asymmetric nature of it in the Osprey
simply means that recovery (as for a "dropped" wing) simply exacerbates the
condition and increases the terminal roll-rate. Marine and Eval Team
attention has been concentrating on avoiding the condition. Unfortunately
the type of dynamic flight profiles that a combat aircraft will fly simply
means that the condition will always be lurking at the edge of that flight
envelope - and very definitely EASILY encountered.


It's indeed a pity that the designers didn't do more design proving and
tunnel-testing because it became slowly obvious (after the Marana crash)
that the problem is married to the tri-bladed prop-rotor decision. A four-bladed prop-rotor design
would be much less likely to encounter VR and a five-bladed rig supposedly
would not. This trend away from VR susceptibility is a function of
rotor-disc "solidity". The tri-bladed prop-rotor was decided upon as a compromise
between span and blade technology management (weight and complexity of the
pitch-control at the rotor-head and tilt mechanisms).


At this late stage of development (of both the Osprey and 609) asymmVR is a
disastrous failing. I honestly don't see how they could certify a civil
variant of the V-22 or the 609.


It would now appear that the Osprey has more than one basic design problem. If asymmVR wasn't bad enough, there is now evidently also the problem wrought by the failure of the cross-ship drive-shaft and its intricate coupling. As you can appreciate, without it a donk failure on one side would be uncontrollable - so it was a facility logically and necessarily provided in order to accommodate an engine failure. However, if that facility itself fails, the only solution in airplane mode is to uniformly and simultaneously flatten the blade-pitch on each side, and enter autorotation by "tilting" the nacelles toward helicopter mode (wherein the airflow - and not the engine- is driving the blades ). My spies tell me that the Marine Corps does not permit full-blown entry into auto-rotation for practise. My guess is that whilst it may have been a real engine failure, it was more likely brought about by a simulated (training) failure. Recent failures associated with the cross-ship drive have been "warning lights". I assume they'd be eccentricity, overtorque or chip detector lights for gear-box oil.


In the engine failure case, the cross-ship drive should enable full controllability. However if the cross-ship drive failed, they would have to very quickly reduce the good engine to flight idle. The differential thrust of flight idle on one side (and a truly dead donk on the other) would soak up much of the differential collective control available - i.e. they would thereafter simply run out of lateral controllability as they reduced airspeed near the ground (simply because the aileron's aerodynamic control effectiveness diminishes as forward speed is lost). What they needed to do (but which would have required the mental agility of the Shadow and the reflexes of J.C. Van Damme) was to flame-out (fuel-chop) the other engine also. However this then diminishes the hydraulic and electrical generating capability somewhat - so firstly they'd have to start the APU. Not likely in the time available I hear you saying. So, in these circumstances, slowing down for the classic helicopter-style autorotative zero-groundspeed arrival was not an option. Perhaps it needs an auto-deploying RAT (ram air turbine).


But I would guess that this highly experienced MV-22 crew found the fatal flaw in the design whilst simulating engine failure (i.e. by winding back one engine to flight idle). If the cross-ship drive-shaft or coupling failed under the torque-stress of wind-up or -down, the drag on the simulated inoperative engine's reduction gear-box would likely lead to a loss of RPM/decreased pitch on one side and a resulting rolling moment. You then have a similar (to engine-failure case) differential residual thrust situation - both engines at flight idle but one carrying the drag of the cross-ship drive. I'd guess that no weak-link was able to be built into the cross-ship system - or even a manual disconnect - it having to be capable of carrying the power in either direction.


I've nursed a sneaking suspicion about the cross-ship drive being unequal to some situations. A gracefully degrading engine or even a sudden flame-out would probably not transfer excessive torque to the drive. But an uncontained failure, engine seizure, transmission gear-box failure? Any of these would be hard on a drive that passes large amounts of raw power through angled-drive gear-boxes - and so I'd guess those gear-boxes and couplings are probably the Achille's Heel in the system.


So stand by to be fascinated as the tester-boys at Patuxent River try to find a way around this major glitch - assuming that I'm right in my analysis of what's been disclosed. As I've been saying all along, the lack of real tunnel-testing and an over-reliance on computational modelling has led them into one bind after another. Garbage in, garbage out is not necessarily the same processed problem as "nil entry always equates to nil result". IMHO that's why test-flying and tunnelling was first utilised. It always disclosed problems that you never dreamed existed. And if you never suspected them, how could you ever model them for computational number-crunching. If number-crunching is now your primary proof-testing method, you must be prepared to learn further in the hard school of knocks. The USMC is rediscovering that truism.


But it's good to see Gen McCorkle on CNN supporting the Osprey to the hilt. What else is a Marine General to say?


[This message has been edited by UNCTUOUS (edited 05 February 2001).]