Witness Lionel Douglass, who was attending a wedding on a bluff about 1,000 yards away from where the helicopter crashed and exploded. Douglass told ABC News that he saw the helicopter plummet from the sky after doing two complete circles as if the pilot was searching for a spot to set the aircraft down.

"It happened so fast. When I saw them turning, I wasn't sure what he was doing and by the time I yelled to everybody to turn around and look, it was all out of control," Douglass said. "It fell down between the mountains, the tail broke in half, it hit the bottom and it was the biggest explosion you ever heard and then flames like you never seen before."

He said the initial explosion was followed by five or six others.

...and who is confused?

Well the witness suggests it all got out of hand whilst circling so my dead mans curve theory just went south.

I'm curious what people's understanding of dead mans curve is, and how you might apply a HV chart in an operational context.

From the eye witness account the helicopter was out of control, and the tail boom was chopped off before it hit the ground. Engine failure is still a possibility...the eye witness description might fit a low RRPM situation during an auto-rotational descent.

But surely low rpm would mean blades would bend up and away from the tail ? Either way it changes everything if the tail came off before impact .

Low rpm also brings less stability, so a little cyclic stick movement can lead to a lot of response...

you will probably have slower response to cyclic input but the aerodynamic damping will also be less - the apparent lack of response can lead to larger control inputs and over-controlling.

As with TC - my theory about it happening on approach or departure also went South.

I'm not sure there is any confusion about dead-man's curve - inside it you are unlikely to be able to achieve a safe autorotative state that will allow you to carry out a normal EOL - it assumes a one second delay between engine failure and pilot action. It doesn't mean you will die but unless you are very skillful or very lucky, you are probably going to bend the machine and possibly yourself.

Having been persuaded by my wife, she and I took a tour flight some years ago. We were taken from the top and dropped off at the bottom of the canyon for a boat trip then flown back up. There was quite a bit of time during our particular flights that there was no safe landing point within autorotational distance. I was not comfortable at all having spent most of my career flying twins.

Well perhaps take comfort from the fact that most accidents are due to pilot error and single engine helicopters are more reliable than twins. :}

Maybe, but pilots need to be mindful that the HV diagram is predicated on <5kts of wind on the nose, operating at maximum allowable takeoff weight, and having a hard surface runway infront of you to safely land straight ahead should an engine suddenly become inoperative.

If you are lighter than max then obviously more fudge factor goes in your favour the lighter you are.

Without the hard surface runway you are outside the test parameters under which the HV chart was drawn. Obviously if the landing area is instead a boulder field full of big rocks you aren't likely to pull off a safe landing if the donk quits even if you've avoided flying within the shaded area of the chart. Which is why I was puzzled somewhat at the initial mention of dead-mans curve in the operational context of this accident.

I took a Papillon EC-130 tourist flight from the Grand Canyon Airport a couple of years ago. The whole flight was within the National Park, was above the canyon rim and followed a predefined GPS-waypoint flightpath.

I had no idea that there was another operation downstream of the National Park in the Hualapai reservation, which included flights and landings within the canyon. While looking for information on this, I stumbled on a very interesting National Geographic article about the impact of tourism on the canyon:

https://www.nationalgeographic.com/m...ational-parks/

In the article is this amazing time-lapse photo of the helicopter and boat traffic in the Hualapai reservation:

http://i.imgur.com/hYPkmpY.png

160 helicopters in eight hours - one every three minutes. It's a very busy place!

IFT - I agree - last September I was a passenger on such a Papillon Ec-130 flight and I could clearly see five to eight helicopters in the 'Queue' of traffic making its way over the reservoirs and valley route from Boulder City - the higher route apparently. I did not see any helicopters lower than us but I was not looking for them. In my uneducated view, there was about a half-mile separation between us.

I am not making any implication as to the cause of this particular tragic accident. I was only making a point regarding the overall safety of flying singe engined helicopters over hostile terrain.

Show me the evidence that demonstrates that single engined helicopters have a lower engine failure rate PER INSTALLED ENGINE than multi engines helicopters, excluding intentional precautionary shut-downs

You also need to show me the evidence that singles have a lower forced landing rate than multis.

The logic of your statement above would indicate you are arguing for single engine helicopters to replace twin engine helicopters for all offshore operations over hostile seas.

Hugh, his comment was a jocular reference to a certain poster here who continuously maintains that a single engine helo is safer than a twin. Note the emoticon he concludes with.

Thanks for that megan I learn something every day. I didn't recognise the connection of a face with bad teeth and humour. Too subtle for me :O

I don’t actually think his post was a reference to another poster. However, it was certainly intended to incit a reaction. Hugh bit.

I saw this on a site,

" on the trip immediately before the fatal flight the helicopter abruptly turned around on the eastern (outbound) leg of the trip and returned home without touring the canyon"
probably a pax was airsick , sounds like there where quite gusty conditions

the wedding witness as mentioned on a previous post flew out and back in a helicopter and reported a rough ride , media have dramatized it

https://www.azcentral.com/story/news...ays/348127002/

Bravo, you're obviously not familiar with the thoughts and writings of AnFI.

I am. You are obviously not familiar with the 'thoughts' and writings of chopjock.

is it thought that the engine failed?
seems more likely the tail failed?