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Myths and Crosswinds and Know-It-Alls


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So I was talking to this 206B pilot recently - young guy. I mentioned how much I liked the machine and the guy made a face. "Oh, I prefer the R-44," he said. I was, like, huh? Then he related a story of how he was doing a flight in a 206B with a really heavy load. He came into his LZ with a right crosswind and could barely hover *and* had just about full left pedal applied.

 

"Well there's your problem, you had the wind on the wrong side," I said.

 

"No!' he said suddenly. "The left side is the wrong side! You'll get into tail rotor LTE!"

 

I asked him how much time he had in 206's, and he admitted that his 206 time is under 50 hours. Probably well under, I'd guess. Most of his flight time was accrued as a CFI, and he boasted to me that he ran a flight school for a period of time (implying that HE knew what he was talking about and I did not).

 

Anyway at that point I realized I was talking with a gen-you-wine helicopter expert, so I gently eased out of the conversation and went back to my table and my beer.

 

Next day he called me up - one of my nitwit friends gave him my number. He said that overnight he thought about our little talk and said he had to reconsider his thoughts on the subject. Perhaps weathervaning tendency *was* a more dominant force when deciding which crosswind to select for a hot/heavy approach. I had to admire his openness.

 

But then he said something that truly pissed me off. "Still, I just prefer an R-44 with its strong tail rotor over a 206 with that weak-ass tail rotor."

 

I shook my head and looked at my phone. "Say WHAT?"

 

I explained to the youngster that, look, I've been flying 206's all my life - got six or seven thousand hours in them - admittedly all at sea level, but I've done some really hairy things over the course of my career. And I have never, ever, EVER hit the left pedal stop. I have NEVER gotten into LTE. And yet I read on the internet all the time about how the 206 has this terrible, deficient, defective, weak-ass tail rotor.

 

Something doesn't compute.

 

Apparently, two myths have grown in flight schools across the land: 1) That the 206 has a deficient tail rotor; and 2) That you should avoid wind off the left because it will cause the ship to IMMEDIATELY enter into T/R VRS and start spinning around uncontrollably. Pilots are genuinely scared to have the wind off the left, which to me is simply astonishing.

 

Both of the above myths are WRONG. Some of us have been flying 206's for many, many years and have somehow, perhaps miraculously avoided spinning around uncontrollably like a top even though we make our approaches with the dreaded left crosswind.

 

Yes, a direct left crosswind *can* get the t/r into LTE. But AS SOON as the nose yaws even a little, the tail rotor exits LTE. It does NOT "stall" or quit working entirely. Same with a wind from the left-front. Yes, the main rotor vortices *can* impinge on the tail rotor, causing variances in thrust. But they are minor and, more importantly, MOMENTARY.

 

I was quite frustrated and disappointed with both convesations I had with this young 206 expert. I had planned on giving him some friendly, fatherly advice, but ultimately decided against doing so. I feel badly about this. I mean, I really could give this kid a very thorough 206 make/model checkout, something he apparently did not ever get before getting a job as a 206 PIC. But when "2,000 hour" pilots come off as if they already know everything there is to know about flying, I back off.

 

I still don't know all there is to know about flying. These friggin' S-55's I'm flying this summer are teaching me new stuff every time we go up. And this is my third season flying them. And I've got a little more than 2,000 hours total time.

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Air Evac Life Team flies the B206L4. They have had a number of incidents in which the pilot lost control of the tail. Either LTE or the aircraft nose started turning and the left pedal input resulted in an over torque. One such recent incident was caught on CCTV. I have not seen it though.

 

I have also seen the EC130 loaded to max gross weight at 2200 feet and 110 degrees. That is also a litle difficult to manage. Again, a little right pedal and there is an exceedance.

 

I still learn form and seek information from "higher time" pilots as well. It is a never ending learning process. One which as we learn should pass down to others.

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Apparently, two myths have grown in flight schools across the land: 1) That the 206 has a deficient tail rotor; and 2) That you should avoid wind off the left because it will cause the ship to IMMEDIATELY enter into T/R VRS and start spinning around uncontrollably. Pilots are genuinely scared to have the wind off the left, which to me is simply astonishing.

 

 

#2 was taught to me in flight school as well. #1 at the Robinson Safety Course,...big surprise right?

 

When I first flew the 206 I noticed a diagram showing the "avoid area" from the right instead of the left as I was taught, and was confused,...still am a bit!

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206s are great ships. I learned to fly in them, and even as a lead footed newbie I never ran out of left pedal. There were times I ran out of torque hovering around with three heavy dudes and full fuel, but that was easy enough to deal with. Never ran out of pedal...

 

I ran out of pedal in an OH-58A, but I was being dumb and it had nothing to do with a tail rotor deficiency.

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There is a huge difference between LTE and just running out of pedal.

 

Many threads have been filled on this and other forums about the way that the Bell spin wizards have made everybody think that EVERY helicopter can get LTE, whereas it was only the early 206 with the small tail rotor that had the problem. These guys are so good, that LTE is now in FAA books and 150-hour instructors have been teaching it to their 20-hour students for untold numbers of cycles. People blindly say that any incident where the pilot demanded too much from the pedals MUST have been LTE and therefore not their fault.

 

Horsefeathers.

 

Like Nearly Retired, I have over 7000 hours on the 206. I have come close to running out of pedal, but always kept a little up my sleeve and flew away. Never has this LTE monster showed its face.

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It's easy enough to get into LTE in a 206. Come in hot, and flare the thing hard, pulling pitch to 100%+ torque, and you can certainly get the nose to start turning. Like Bob, I've been flying 206s for a long time. I have more than 10,000 hours just in the 206, and I have never, ever come close to LTE. The secret to avoiding it is to make approaches slowly, never cowboy it. I also prefer the wind off the left, because the 206 weathervanes very strongly. Offshore, I've gone from flat pitch to an OGE hover and back, repeatedly, with my feet flat on the floor. Put the nose into the wind, with > 10 knots, and it won't move. If you must maneuver with a crosswind, and you certainly must now and then, put the wind to the left if possible, and do everything S L O W L Y. Almost all overtorques and LTE incidents are caused by being too fast for the conditions. I've landed offshore many times with 40 knot winds and a left crosswind, as well as with very light crosswinds and every speed in between, and never come close to LTE, because I make slow approaches. Being slow and smooth on the controls works every time, for every make and model, for every weather condition. Being fast and making quick twitchy control movements is asking for trouble.

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But when "2,000 hour" pilots come off as if they already know everything there is to know about flying, I back off.

 

 

Nice post! It's sad to say but there are so many know-it-alls out there!

 

 

...and 150-hour instructors have been teaching it to their 20-hour students for untold numbers of cycles

 

This is what our system produces. Can you really blame these guys for acting like "know-it-alls"? If you don't like the quality of the new guys then change the system so that new pilots are taught by pilots who actually have experience! Then maybe this attitude and misinformation will go away? But if all I can teach you is what I've been taught (and I've never been away from the school), then, well, you've seen what happens!

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I guess I should acknowledge that LTE *does* exist. Sure, I mean look at that huge vertical fin on the 206 and how it blanks off so much of the inflow above *and* below the t/r gearbox! (And apparently Bell has not learned anything since the 206 was introduced because their new EC-120-beater has the exact same fin!) If you're heavy and you hover a 206 with the wind up your butt, you can EXPECT that it's going to want to swap ends, maybe completely, and maybe without any warning. You have to be ready, willing and able to stuff FULL left pedal in AND HOLD IT until the yaw rate stops. Like Gomer, I always keep a little left pedal in reserve. When I feel myself getting close to the stop, I do something different.

 

Personally, I think that most "LTE accidents" in the 206 are really just a matter of the pilot being behind on the controls and not using them to the fullest. But can it happen? Sure, I suppose. But remember, the tail rotor never stops working...never stalls...never stops producing thrust. So pilots who ALLOW rotation of more than 180 degrees or so are asleep at the switch.

 

I guess my rant was really about how certain misconceptions can fester. It's like children playing the game of "telephone." One guy relays a story about an "LTE" experience in a 206 and down the line "conventional wisdom" becomes that the 206 has a weak, defective tail rotor.

 

We had a safety meeting recently with our group of pilots. I showed them an NTSB accident report of a 206 that reportedly got into LTE as the pilot was trying to set it down on a dolly in California. We discussed the pilot's statement to the feds, and then I showed them the video of the event which was captured by the cameraman in the back seat. Sure enough, during this "LTE" encounter, the pilot's feet on the pedals were NEUTRAL, not "full-left" as he told the FAA.

 

And personally it galls me when people make disparaging comments about the 206 while having less than 50 hours in it.

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I think it's important for pilots to be confident in their flying skills as well as their knowledge. Confidence needs to be tempered with humility to prevent "knowitallness". But by the same token the very experienced shouldn't misinterpret confidence for a pilot being a know it all. All other things being equal, self confidence makes a pilot a much better pilot.

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There are to many LTE reports for me to poo-poo them all.

The 206 didn't (doesn't?) have a lot of tail rotor authority. I have hit some stops trying to get the back end to swing into the wind. Stop and think of other ways to do it. Don't do hard, low speed banks with sudden power changes into the hover and a tail wind...

Always seemed a very forgiving, easy ride.

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Wally, the 206 RFM says that they only demonstrated the aircraft to 17 knots, and even that was not a limit or a guarantee. I agree that LTE is possible in a 206 but like main rotor VRS you have to work at it to get into it. But I *seriously* doubt that people get into LTE by having a wind from either the left or left-front. To me it just seems incredible.

 

The video of the "LTE crash" at Van Nuys airport that I mentioned in an earlier post is actually linked in a thread on PeePrune. It's from an episode of a crappy television program called "Real TV" or something like that. The video completely contradicts what the pilot told the FAA. This makes me be skeptical of *anything* a pilot tells the feds after a crash.

 

And aeroscout, I'm with you, man. I believe that helicopter pilots need a good dose of confidence bordering on arrogance. Call it "tempered aggressiveness." Whatever. In my opinion, an "average" helicopter pilot is a dead helicopter pilot. But there's a fine line. We've all got to *know* we're damn good at what we do without actually ever telling someone that we are. I get wary when a pilot tells me right off the bat how good he is. Especially when other factors persuade me to the opposite opinion.

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Please, people, don't keep using the term "loss of tail rotor EFFECTIVENESS" - the T/R is still effective in 99% of cases, it is just unable to provide enough power for the situation YOU have put it in.

 

If it had lost effectiveness, it wouldn't matter if you put in opposite pedal, because supposedly it is no longer effective. But if you have the left pedal on the stops, and you are turning right, you will scare yourself sh*tless if you took out some of that left pedal. It is still effective, just unable to do what you are asking of it.

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eagle5, on 22 Jun 2013 - 10:11, said:

 

 

When I first flew the 206 I noticed a diagram showing the "avoid area" from the right instead of the left as I was taught, and was confused,...still am a bit!

 

That is one of the Myths about Crosswinds. They’ve taught that there’s a good side and a bad side to be avoided. That’s a generalization and over simplification of the actual flight characteristics. Both left and right crosswinds present their own unique flight characteristics. Once you learn those characteristics you’ll see it’s sometimes a pick your own poison situation (left or right crosswind).

 

Winds from the right require more tail rotor thrust (more left pedal) to maintain heading due to impingement of main rotor wake on the tail boom, main rotor torque, and the wind speed increase from the right trying to also turn the nose right into the wind; however, that relative wind will not caused much if any undesirable tail rotor thrust variations; therefore, very little handling issues with respect to increased pedal activity are required.

 

Winds from the left require less tail rotor thrust (less left pedal) to maintain heading due to the main rotor torque being countered by the wind speed increase from the left attempting to turn the nose left into the relative wind. However, relative winds for the left are undesirable as they oppose the tail rotor induce flow velocity and lead to main rotor vortex interference, tail rotor vortex ring state, along with handling issues that require increased pedal activity. The pilot ends up dancing on the pedals, swing left and right, trying to settle down a consistent heading.

 

These handling issues with winds from 225º - 330º lead to the wild pedal swings shown in the figure below. These swings can and will give the pilot the false appearance of Loss of Tail Rotor Effectiveness (LTE) as they try to correct for these unanticipated yaw swings.

 

Though unlikely in most cases, LTE is possible when the helicopter is operating at low airspeeds OGE, especially at gross weight under the crosswind conditions above when the margin between power available and power required narrows to near zero.

 

That’s what’s being explained in this recent safety notice.

 

Quote

Safety Notice SN-42

 

Issued: May 2013

 

UNANTICIPATED YAW

 

A pilot's failure to apply proper pedal inputs in response to strong or gusty winds during hover or low-speed flight may result in an unanticipated yaw. Some pilots mistakenly attribute this yaw to loss of tail rotor effectiveness (LTE), implying that the tail rotor stalled or was unable to provide adequate thrust. Tail rotors on Robinson helicopters are designed to have more authority than many other helicopters and are unlikely to experience LTE.

 

To avoid unanticipated yaw, pilots should be aware of conditions (a left crosswind, for example) that may require large or rapid pedal inputs. Practicing slow, steady-rate hovering pedal turns will help maintain proficiency in controlling yaw. Hover training with a qualified instructor in varying wind conditions may also be helpful.

 

Scan1_zps51617644.jpg

 

Scan2_zps6d62fc27.jpg

Edited by iChris
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That is one of the Myths about Crosswinds. They’ve taught that there’s a good side and a bad side to be avoided. That’s a generalization and over simplification of the actual flight characteristics. Both left and right crosswinds present their own unique flight characteristics. Once you learn those characteristics you’ll see it’s sometimes a pick your own poison situation (left or right crosswind).

 

Winds from the right require more tail rotor thrust (more left pedal) to maintain heading due to impingement of main rotor wake on the tail boom, main rotor torque, and the wind speed increase from the right trying to also turn the nose right into the wind; however, that relative wind will not caused much if any undesirable tail rotor thrust variations; therefore, very little handling issues with respect to increased pedal activity are required.

 

Winds from the left require less tail rotor thrust (less left pedal) to maintain heading due to the main rotor torque being countered by the wind speed increase from the left attempting to turn the nose left into the relative wind. However, relative winds for the left are undesirable as they oppose the tail rotor induce flow velocity and lead to main rotor vortex interference, tail rotor vortex ring state, along with handling issues that require increased pedal activity. The pilot ends up dancing on the pedals, swing left and right, trying to settle down a consistent heading.

 

These handling issues with winds from 225º - 330º lead to the wild pedal swings shown in the figure below. These swings can and will give the pilot the false appearance of Loss of Tail Rotor Effectiveness (LTE) as they try to correct for these unanticipated yaw swings.

 

Though unlikely in most cases, LTE is possible when the helicopter is operating at low airspeeds OGE, especially at gross weight under the crosswind conditions above when the margin between power available and power required narrows to near zero.

 

That’s what’s being explained in this recent safety notice.

 

 

Scan1_zps51617644.jpg

 

Scan2_zps6d62fc27.jpg

 

Excellent explanation.

 

I would just add that DA plays a critical part in one's ability to manage LTE. You could be operating at sea level, at high gross weight in a critical wind azimuth and still have plenty of tail rotor authority.

 

In the same scenario at a high DA, the pilot may not have sufficient T/R authority due to the inherent decrease in thrust while operating in thin air.

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This is one where the FAA is spot on I believe -

 

"LTE is a critical; low-speed aerodynamic

flight characteristic which can result in an
uncommanded rapid yaw rate which does not subside
of its own accord and, if not corrected, can result
in the loss of aircraft control. "
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To HGP, a lot of the loss of T/R effectiveness you predict stemming from higher DA's is offset by the reduction in torque that results from higher DA's.

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To HGP, a lot of the loss of T/R effectiveness you predict stemming from higher DA's is offset by the reduction in torque that results from higher DA's.

 

I disagree.

 

With a piston engine, torque and power output will decrease as DA increases (less oxygen/fuel combusting within the cylinders, resulting in less energy being produced). However, I would say that the decrease in torque is not proportional to the decrease in thrust produced by the tail rotor.

There is a relatively small decrease in total power output (and torque), but a large decrease in aerodynamic efficiency (of both the main rotor and tail rotor).

 

With a turbine engine, you can still create tremendous amounts of torque, even at a high DA. You could be operating at a very low temperature, with a very high pressure altitude and reach your torque limitation before reaching the TOT limit.

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With a turbine engine, you can still create tremendous amounts of torque, even at a high DA. You could be operating at a very low temperature, with a very high pressure altitude and reach your torque limitation before reaching the TOT limit.

 

 

I don't think the method of combustion has much to do with it. You're still going to have the resident reduction in power available regardless. Never flown a piston engine either, so I will caveat my experience is based on book knowledge only. Your basically saying that a piston engines main rotor will tend to take more power than the tail rotor relative to a turbine powered aircraft. I will say that the same is just as true for turbine engines. I would also say that blade efficiency is also a minor cause but the main culprit is the high DA. Piston powered aircraft also tend to be lighter than turbine aircraft, which also affects blade efficiency.

 

Which is exactly what you see in this clip below...with turbine powered aircraft...Note that the T700 engine depending on model will put out about 1700 SHP, and there are two on H-60s. I've been in that exact situation that you describe and been limited by TOT. I'd put decent money that these guys hit their TOT limits before TQ.

 

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I don't think the method of combustion has much to do with it. You're still going to have the resident reduction in power available regardless. Never flown a piston engine either, so I will caveat my experience is based on book knowledge only. Your basically saying that a piston engines main rotor will tend to take more power than the tail rotor relative to a turbine powered aircraft. I will say that the same is just as true for turbine engines. I would also say that blade efficiency is also a minor cause but the main culprit is the high DA. Piston powered aircraft also tend to be lighter than turbine aircraft, which also affects blade efficiency.

 

Which is exactly what you see in this clip below...with turbine powered aircraft...Note that the T700 engine depending on model will put out about 1700 SHP, and there are two on H-60s. I've been in that exact situation that you describe and been limited by TOT. I'd put decent money that these guys hit their TOT limits before TQ.

 

 

I'm not talking about the distribution of 'power' between the main rotor system and the tail rotor, but rather tail rotor authority- the ability of the tail rotor to effectively manage torque.

 

It is my understanding that any reduction in torque due to the powerplant operating at high DA does not off-set the decreased thrust produced by the tail rotor. Tail rotor authority decreases as DA increases, even if there is a lower torque output.

 

I could be mistaken about reaching torque limits at a high PA/low temp; TOT or Ng may actually be the limiting factor. I'm still in the process of learning about turboshaft engines.

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It seems to me that although this is a discussion of the 206s tail rotor's effectiveness versus the R44, but the real underlying issue is the Know-it-all attitude. Students who become instructors and their instructors becomes a bit of a catch 22. They have no real world knowledge and so it becomes an issue of "I've been told this" and they then begin to distribute somebodies opinion as fact, and after it's passed down enough times there's no longer the knowledge of who originally said it and how credible they are. Much like the famous "come to our school because we fly the R22 and it's the most difficult, and it'll be easier to get a job" blah blah blah. Which originated with who knows and gets passed down enough times that it's impossible to know who said it originally and if that person had even ever flown anything else before making the statement.

 

It all comes down to airmanship and the dedication to professionalism which sadly isn't taught in schools. Any Joe Shmoe can get through flight school and memorize regulations, fewer of those guys know how to apply their knowledge professionally, and even fewer know how to be a helicopter pilot with dignity. I really get upset when I hear guys spout off knowledge for the purpose of showing off rather than offering advice to educate.

 

I remember reading "Redefining Airmanship" and the sequel "Flight Discipline" (and I eagerly await Flight Discipline 2: Electric Boogaloo"). These touched on personal flight integrity and discipline and I still emphasize to students these practices. I realize that it's difficult when all you do is pattern work to practice approaches, but a student, like a teacher needs to always be presentable, professional and disciplined.

 

Guys who brag about what they do and what they know don't strike me as professional, just as I would never discuss politics or religion at work, I don't brag about anything. I'll happily educate and offer advice, but not without a goal of increasing safety or awareness in mind. I don't presume to know everything, but I study and try to learn something new everyday. That's my personal discipline and integrity. Never fly unless the helicopter is presentable, I'm presentable and I feel completely ready to handle any situation that may come up. Never get complacent, this is a career for professionalism not hotshots.

 

When you climb in that cockpit you're entering an agreement, you're agreeing to the passengers that you're professional and safe, you're agreeing to the people whose houses you fly over that you're professional and safe, you're agreeing to the tower, the other pilots in the air, the student next to you and to yourself that you're dedicated to professionalism, and when that's forgotten, it leads to accidents.

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With a piston engine, torque and power output will decrease as DA increases (less oxygen/fuel combusting within the cylinders, resulting in less energy being produced). However, I would say that the decrease in torque is not proportional to the decrease in thrust produced by the tail rotor.

There is a relatively small decrease in total power output (and torque), but a large decrease in aerodynamic efficiency (of both the main rotor and tail rotor).

 

With a turbine engine, you can still create tremendous amounts of torque, even at a high DA. You could be operating at a very low temperature, with a very high pressure altitude and reach your torque limitation before reaching the TOT limit.

 

That’s another area of difference between piston and turbine engines, the effect of atmospheric conditions on power available. The power available from a piston engine depends upon density altitude, whereas the power available from a turbine engine depends upon pressure altitude and mainly temperature.

 

This is confusing to some since pressure altitude and temperature makeup density altitude; however, that same density altitude can be made from a variety of pressure altitudes and temperatures, just take a look at any density altitude chart.

 

Put another way, the thermodynamics of a turbine engine are affected more by the inlet air temperature than by the density of the air, whereas a piston engine is more affected by the overall air density.

 

Study the torque available chart for a TH-67 (Bell 206) below. The torque available is actually higher at 10,000’ PA@-10C (9,380’ DA) than for 5,000’ PA@40C (8,860” DA). This increase in torque available (From 87% to 95%) at the higher PA and DA is mainly due to the decrease in inlet air temperature.

 

TH67_B206TorqueAvailable_zps46aca685.jpg

Edited by iChris
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Which is exactly what you see in this clip below...with turbine powered aircraft...Note that the T700 engine depending on model will put out about 1700 SHP, and there are two on H-60s. I've been in that exact situation that you describe and been limited by TOT. I'd put decent money that these guys hit their TOT limits before TQ.

 

 

What are we seeing? We see two Navy MH-60’s that have the capability (Performance wise, aerodynamically, and other wise) to safely hover over Lake Tahoe and make pedal turns in any direction. So why would one end up in the drink? It appears to be pilot error or some type of mechanical failure? Are you saying this was LTE?

 

"A retired Navy pilot told the San Diego paper he thinks the helicopter crew may have had a legitimate reason to do whatever they were doing. Steve Diamond said if they were hot-dogging they wouldn't do it in view of another aircrew, or over a popular tourist spot."

 

"It's possible they were troubleshooting a problem," Diamond told the paper. He added it would be easy to make a snap judgment, but cautioned there are other possibilities."

 

New Details From Choppers' Dip in Lake Tahoe

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