Prototype Gyrocopter Crashes in Texas
Thread Starter
Prototype Gyrocopter Crashes in Texas
From this morning's Avweb news...
CarterCopter Claims To Break Mythical Barrier...
"From Exhilaration To Devastation"
... Along with the prototype. The staff at CarterCopter, in Olney, Texas, was busy on Friday afternoon preparing a press release about that morning's success -- they had finally achieved an aerodynamic breakthrough they'd been working on for years -- when news came in that the one-of-a-kind prototype gyrocopter had been destroyed in a crash. Pilots Larry Neal and Brad King were out on a test flight when something went wrong. "We don't know what it was," CEO Jay Carter Jr. told AVweb on Saturday. "Things happened really fast. It was like somebody slammed on the brakes. The nose pitched down and it started rolling to the left. Larry thought it was going inverted." The aircraft righted itself, and Neal and King were able to regain some pitch control just before they hit mesquite trees. The rotor provided enough lift in the descent that it essentially acted as a built-in parachute, Carter said.
The aircraft plowed through the trees at about 70 mph, Carter said, and hit the ground. The landing gear absorbed much of the impact. The cockpit remained intact, but everything else was torn apart. The pilots walked out of the woods to a nearby road, where they were found by CarterCopter staff about 20 minutes later. "That pressurized fuselage is so super-strong, it saved their lives," Carter said. The fuel tank is in the cockpit, a design that some were uncomfortable with, but Carter said this accident proved the wisdom of it. That was the best-protected place, and there was no fuel spill and no fire. The aircraft is not repairable, Carter said.
Despite his disappointment over the loss, Carter said he was "ecstatic" over the success of Friday morning's flight. "We exceeded a Mu of 1 for the first time in history. This has been our goal ever since we started flight-testing in 1998. ... History will prove out the significance of this." The "Mu-1 barrier" is an aerodynamic limit defined by a forward speed and rotor rpm combination that results in advancing (moving into the relative wind) blade tips reaching speeds of twice that of the aircraft. At the same time, the retreating blade tips experience zero airspeed (as they rotate away from the relative wind) on the opposite side -- the entire inboard portion of the blade sees "reverse" air flow. The predicament prevents rotorcraft from achieving high forward speeds (CarterCopter sports small wings). According to the company, the barrier was breached during normal flight-testing Friday morning, while collecting data on a newly developed speed controller for the rotor. Initial data from Friday's flight shows that the airspeed was 170 mph and the rotor was slowed to 107 rpm, for a Mu value of 1.02. A Mu of 1 would enable a gyrocopter to fly up to 300 mph, Carter said.
The milestone attempt wasn't planned but evolved as the rotor proved to be stable as the rpm was decreased. Carter said he believes the breakthrough paves the way for rotorcraft to reach up to Mu-5 and fly up to 500 mph. With vertical takeoff and landing capabilities and the safety of a lifting rotor that acts as "built-in parachute" -- "That's pretty darn good. We hope we'll get the opportunity to build another one," he said. It was a combination of patented technologies that led to the breakthrough. "It's about eight things combined, but the key things that made this possible are the rotor-blade design and the computer-automated controls," Carter said. The data and video from the morning's breakthrough flight are being analyzed. As an element of a current U.S. Army contract the Army is scheduled to verify the calibration and accuracy of the data in the next few weeks.
CarterCopter Claims To Break Mythical Barrier...
"From Exhilaration To Devastation"
... Along with the prototype. The staff at CarterCopter, in Olney, Texas, was busy on Friday afternoon preparing a press release about that morning's success -- they had finally achieved an aerodynamic breakthrough they'd been working on for years -- when news came in that the one-of-a-kind prototype gyrocopter had been destroyed in a crash. Pilots Larry Neal and Brad King were out on a test flight when something went wrong. "We don't know what it was," CEO Jay Carter Jr. told AVweb on Saturday. "Things happened really fast. It was like somebody slammed on the brakes. The nose pitched down and it started rolling to the left. Larry thought it was going inverted." The aircraft righted itself, and Neal and King were able to regain some pitch control just before they hit mesquite trees. The rotor provided enough lift in the descent that it essentially acted as a built-in parachute, Carter said.
The aircraft plowed through the trees at about 70 mph, Carter said, and hit the ground. The landing gear absorbed much of the impact. The cockpit remained intact, but everything else was torn apart. The pilots walked out of the woods to a nearby road, where they were found by CarterCopter staff about 20 minutes later. "That pressurized fuselage is so super-strong, it saved their lives," Carter said. The fuel tank is in the cockpit, a design that some were uncomfortable with, but Carter said this accident proved the wisdom of it. That was the best-protected place, and there was no fuel spill and no fire. The aircraft is not repairable, Carter said.
Despite his disappointment over the loss, Carter said he was "ecstatic" over the success of Friday morning's flight. "We exceeded a Mu of 1 for the first time in history. This has been our goal ever since we started flight-testing in 1998. ... History will prove out the significance of this." The "Mu-1 barrier" is an aerodynamic limit defined by a forward speed and rotor rpm combination that results in advancing (moving into the relative wind) blade tips reaching speeds of twice that of the aircraft. At the same time, the retreating blade tips experience zero airspeed (as they rotate away from the relative wind) on the opposite side -- the entire inboard portion of the blade sees "reverse" air flow. The predicament prevents rotorcraft from achieving high forward speeds (CarterCopter sports small wings). According to the company, the barrier was breached during normal flight-testing Friday morning, while collecting data on a newly developed speed controller for the rotor. Initial data from Friday's flight shows that the airspeed was 170 mph and the rotor was slowed to 107 rpm, for a Mu value of 1.02. A Mu of 1 would enable a gyrocopter to fly up to 300 mph, Carter said.
The milestone attempt wasn't planned but evolved as the rotor proved to be stable as the rpm was decreased. Carter said he believes the breakthrough paves the way for rotorcraft to reach up to Mu-5 and fly up to 500 mph. With vertical takeoff and landing capabilities and the safety of a lifting rotor that acts as "built-in parachute" -- "That's pretty darn good. We hope we'll get the opportunity to build another one," he said. It was a combination of patented technologies that led to the breakthrough. "It's about eight things combined, but the key things that made this possible are the rotor-blade design and the computer-automated controls," Carter said. The data and video from the morning's breakthrough flight are being analyzed. As an element of a current U.S. Army contract the Army is scheduled to verify the calibration and accuracy of the data in the next few weeks.
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Does slowing the rotor RPM down to acheive a high Mu mean you can do the same at 500mph?
I hope they get another ship up and in the air soon.
edit: removed inline image
I hope they get another ship up and in the air soon.
edit: removed inline image
Last edited by zhishengji751; 24th Jun 2005 at 02:01.
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So the aircraft was testing at low Nr, high forward speed and rolled uncontrollably towards the retreating blade side?
Now, when I was a boy.........surely not......
Or did it occur in another flight regime?
Not knocking, just intrigued.
Now, when I was a boy.........surely not......
Or did it occur in another flight regime?
Not knocking, just intrigued.
Thread Starter
Nick,
Would a roll to the left (assuming a US turning rotor system) not be the anticipated direction in a single rotor system as compared to the coaxial ABC concept?
Would a roll to the left (assuming a US turning rotor system) not be the anticipated direction in a single rotor system as compared to the coaxial ABC concept?
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"The milestone attempt wasn't planned but evolved as the rotor proved to be stable as the rpm was decreased."
I know I bring a wealth of inexperience to this forum, but does that sentence bring a sense of unease to anyone else?
I know I bring a wealth of inexperience to this forum, but does that sentence bring a sense of unease to anyone else?
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The quote at the begininning doesn't make it clear, but the accident occurred during a test flight several hours after the one that broke Mu-1. I do not believe they were flying into high Mu numbers at the time of the accident.
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Hmmm....
That's a teetering head isn't it? How can a teetering head run with lift imbalance? The only way to balance the lift at mu>1 is to use reverse velocity airflow over retreating blade. Unless there is a specialised control system this requires collective is down and cyclic is forward (assuming gyro precession of 90 degrees). Interesting how the accident involved rolling to the left and autorotation...
Must admit to being more comfortable with the idea of a rigid rotor for high mu. Even better if there are two, whether coaxial, intermeshing or interleaving. In this case the wings are just optional. Rotor&wing on one machine will have increased hover power and increased high speed drag over counter-rotating rotor system. Me prefer Sikorsky ABC approach...
Mart
[Edit: 'cos i gets my gyros confused sumtimes - don't we all...]
Must admit to being more comfortable with the idea of a rigid rotor for high mu. Even better if there are two, whether coaxial, intermeshing or interleaving. In this case the wings are just optional. Rotor&wing on one machine will have increased hover power and increased high speed drag over counter-rotating rotor system. Me prefer Sikorsky ABC approach...
Mart
[Edit: 'cos i gets my gyros confused sumtimes - don't we all...]
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Sounds like the problem is that the rotor was stable, but the rotorcraft was not! I would expect the left side of the disk to produce no lift, and the right to have to be fully flattened in pitch so it had no lift either, (and the wings providing the necessary lift).
The big question is why they encountered this circumstance as an unplanned event. Bad ju-ju for a flight test to discover a bad behavior (poor rotor rpm control, in this case) that is so bad they lose the helo as a result. It is a miracle that the crew survived, and just that.
None of this takes away from the interesting and possibly important work the Cartercopter guys are doing. I met Jay Carter at an AHS symposum once, and I know he is serious and hard-nosed in his engineering approach to the problem. No flaky pie in the sky thinking going on down there.
I have contended that the best way to explore the high speed regime here was to force the rotor to get there while it was not the prime lifting surface. In other words, strap the rotor to a bigger airplane and step out in speed while messing with rotor rpm, and measuring all the rotor forces and moments and control responses.
The big question is why they encountered this circumstance as an unplanned event. Bad ju-ju for a flight test to discover a bad behavior (poor rotor rpm control, in this case) that is so bad they lose the helo as a result. It is a miracle that the crew survived, and just that.
None of this takes away from the interesting and possibly important work the Cartercopter guys are doing. I met Jay Carter at an AHS symposum once, and I know he is serious and hard-nosed in his engineering approach to the problem. No flaky pie in the sky thinking going on down there.
I have contended that the best way to explore the high speed regime here was to force the rotor to get there while it was not the prime lifting surface. In other words, strap the rotor to a bigger airplane and step out in speed while messing with rotor rpm, and measuring all the rotor forces and moments and control responses.
Last edited by NickLappos; 21st Jun 2005 at 19:57.
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Hilico:
Don't forget the wings. This isn't a conventional rotorcraft; at the higher end of the speed range, the wings are holding the thing up, not the rotor. I've read that the only reason they don't brake the rotor to a complete stop is to save the weight and complexity of a brake etc.
Decreasing the rotor RPM to keep advancing blade tip Mach numbers under control is part of the game plan. No unease required.
'Not planned, but evolved...' now THAT rings alarm bells!
R1
"The milestone attempt wasn't planned but evolved as the rotor proved to be stable as the rpm was decreased." I know I bring a wealth of inexperience to this forum, but does that sentence bring a sense of unease to anyone else?
Decreasing the rotor RPM to keep advancing blade tip Mach numbers under control is part of the game plan. No unease required.
'Not planned, but evolved...' now THAT rings alarm bells!
R1
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Prophesy by J. Carter
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Nick,
"Sounds like the problem is that the rotor was stable, but the rotorcraft was not!"
Do you mean the fixed wingy bit or the rotor craft controlly systemy bit?
"I would expect the left side of the disk to produce no lift, and the right to have to be fully flattened in pitch so it had no lift either, (and the wings providing the necessary lift)."
Makes sense, I'm just amazed a fixed wing (without FBW) can go so unstable so quickly - design looks sensible enough (long/lat dihedral etc). I did wonder about structural failure, but the description sounded more like the rotor suddenly "gripped" in front quadrant. Maybe the control system still has some gremlins. From news clip:
"The nose pitched down and it started rolling to the left. Larry thought it was going inverted."
----
"No flaky pie in the sky thinking going on down there."
Hehehe, i's jus' a dumb ol' speculatin' engineer.
"...explore the high speed regime ... strap the rotor to a bigger airplane ... measuring all the rotor forces and moments and control responses"
Is the NASA Rotor System Research Aircraft still running? I'm suprised this hasn't pushed the boundaries for Carter...
Mart
"Sounds like the problem is that the rotor was stable, but the rotorcraft was not!"
Do you mean the fixed wingy bit or the rotor craft controlly systemy bit?
"I would expect the left side of the disk to produce no lift, and the right to have to be fully flattened in pitch so it had no lift either, (and the wings providing the necessary lift)."
Makes sense, I'm just amazed a fixed wing (without FBW) can go so unstable so quickly - design looks sensible enough (long/lat dihedral etc). I did wonder about structural failure, but the description sounded more like the rotor suddenly "gripped" in front quadrant. Maybe the control system still has some gremlins. From news clip:
"The nose pitched down and it started rolling to the left. Larry thought it was going inverted."
----
"No flaky pie in the sky thinking going on down there."
Hehehe, i's jus' a dumb ol' speculatin' engineer.
"...explore the high speed regime ... strap the rotor to a bigger airplane ... measuring all the rotor forces and moments and control responses"
Is the NASA Rotor System Research Aircraft still running? I'm suprised this hasn't pushed the boundaries for Carter...
Mart
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Mart,
At this point in time, there can only be speculation as to the cause of the crash, IMHO.
However, the CarterCopter's web pages and referenced patents provide a lot of information about the intended aerodynamic and flight-control features of this unique craft.
As with other unique rotorcraft, the CarterCopter would make for interesting study, discussion and assumptions, for those who are intrigued by 'the rotor'.
Dave
At this point in time, there can only be speculation as to the cause of the crash, IMHO.
However, the CarterCopter's web pages and referenced patents provide a lot of information about the intended aerodynamic and flight-control features of this unique craft.
As with other unique rotorcraft, the CarterCopter would make for interesting study, discussion and assumptions, for those who are intrigued by 'the rotor'.
Dave
Improved crash worthiness?
My back of the napkin design for a more crashworthy helicopter is a one piece carbon fiber shell that is bolted to the gearbox. (the same way F1 cockpits are simply bolted to the transmission)
In a crash, chances are that the cockpit would break free of the rest of the airframe and tumble around rather than suffer the gearbox twisting itself into the cockpit.
As I see it the current designs could be better, as they have to cushion the engine and gearbox as well as cockpit.
Making the cockpit a breakaway design would (wild a little luck) leave all of the energy absortion for the preservation of the carbon life forms.
Perhaps this crash is evidence that such a design could have merit?
Mickjoebill
In a crash, chances are that the cockpit would break free of the rest of the airframe and tumble around rather than suffer the gearbox twisting itself into the cockpit.
As I see it the current designs could be better, as they have to cushion the engine and gearbox as well as cockpit.
Making the cockpit a breakaway design would (wild a little luck) leave all of the energy absortion for the preservation of the carbon life forms.
Perhaps this crash is evidence that such a design could have merit?
Mickjoebill
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Hmmm....
Been doing a little lunchtime reading, and i'm actually quite impressed with the level of thought that has gone into this concept. I'm still not entirely convinced that rigids aren't a better rotor system than teetering for high mu, but Carter have certainly done their sums. The mu=1 out of track divergence is a concern, since it suggests that some instability is inherent.
I'll watch this project with interest.
MickJoeBill,
I actually spent some time as a crash engineer (Rover 75 mostly), before i answered my natural calling in powertrains
. Agreed that the most important thing in a crash is for the structure to protect the occupants from the powertrain. As to the rest breaking away, well whatever method absorbs the energy to provide a continous decceleration from impact start to finish.
Mart
I'll watch this project with interest.
MickJoeBill,
I actually spent some time as a crash engineer (Rover 75 mostly), before i answered my natural calling in powertrains
. Agreed that the most important thing in a crash is for the structure to protect the occupants from the powertrain. As to the rest breaking away, well whatever method absorbs the energy to provide a continous decceleration from impact start to finish.Mart
