This article (which goes into a ton of detail on the weather conditions, Visual Flight Rules, Instrument Flight Rules, and special VFR) states that they climbed 875’ in 36 seconds which would be in line with the rates mentioned here fpm:
It would seem to be some sort of mechanical thing; seems pretty silly to barreling downward at even 500 fpm in dense fog; even if you don't do a CFIT, you could hit a tree or power line, either would be a bad thing.
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I can do absolutely anything. I'm an expert!
IRStuff:
"The helicopter was essentially in a dive in the last 20 seconds, going from +1000 fpm to almost -5000 fpm before signal was lost. Unclear how much noise is in the data; a casual estimate would be 300 fpm rms, which makes the one large upblip going from -4000 fpm to -2000 fpm for about 1 second, 8 seconds prior to loss of signal, very curious."
You can have -ve fpm, too. I'm speaking out of ignorance, here. Just want to know.
@dik
Not sure what you mean. The change from -4000 to -2000 fpm, if real, and not just noise, means the pilot attempted to kill the descent for about 1 second and then resumed the rapid descent.
-4000 fpm is 45 mph downward, which is insanely fast for low visibility conditions, even if the pilot thought there was clear air below him, particularly since his altitude wasn't that high, and there's risk of hitting stuff like other aircraft and trees on the way down through the muck.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
I down loaded the raw altitude ADS-B data.
I suspect that some of those bumps are caused by data lag. There may be a slight lag in the GPS signal. Some one second time windows have more than one data point recorded.
The big picture, that is from beginning to end of the final 10 or 12 seconds is more important than relatively small variations in the FPM.
Doing an FPM calculation based on the reported data for three consecutive seconds gives a dropping FPM of 4500FPM, 0,and 5250 fpm.
When you consider going from a drop of 45 MPH to zero in one second and then an acceleration from zero to almost 60 MPH in one second it is obvious that the data needs to be smoothed, or averages taken over a greater time frame than one second.
Bill
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"Why not the best?"
Jimmy Carter
For those of you unfamiliar with the area, the crash site is very near (~2 miles north) of the site where the 1980s TV show MASH was filmed. Many of you will remember the iconic opening scene with the helicopters coming into the medical camp with mountains in the background. The hills where the crash occurred are not as high as those you saw there, but are still substantial.
The crash site is just inland of Malibu Canyon, which often provides a path for coastal fog and low clouds to make their way inland. From the flight path reconstruction linked by Alistair above, it appears that the helicopter got squeezed between rising terrain heading west out of the San Fernando Valley and a lower cloud ceiling, and was attempting to turn around and head back to the San Fernando Valley. (A layman's interpretation for what it's worth.
I really question the validity of those vertical velocities. If you watch the EAR WITNESS that itsmoked linked to above, he didn't indicate any rapid movements or change in engine sound. He just thought the pilot flew into the hill.
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
Looks like the pilot might have been changing attitude controls, since the speed curve mirrors the vertical speed, which would not drastically change engine sound, as he might have kept the throttle at the same position.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
I know this area pretty well. The crash site is several hundred yards east of the Las Virgenes Municipal Water District offices and corporation yard. From 1981 to 1986, I worked in Boyle Engineering's Ventura office. During that time, about 80% of my billable hours were on LVMWD projects. Among other things, I worked on the design of a reclaimed water pumping station in the corporation yard and I inspected construction of a 24-inch reclaimed water pipeline that originated at the pumping station.
At Wikipedia's coordinates (34.1368°N 118.6923°W), the hillside has an elevation of about 1020 feet.
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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill
In a fixed wing aircraft if you suddenly plunged into dense fog you would likely see smooth but still harmful control inputs that would probably result in some reasonably smooth but still fatal CFIT.
With a rotary wing craft what would happen? I'm guessing (possibly incorrectly) that the lack of fixed wing 'flies itself' (when trimmed) stability would instead cause very rapid loss of control. Yes/no? Rather like trying to ride a unicycle blindfolded?
My fluids prof way back when called the urge to get there influencing decision making 'Getthereitis' when we were talking about a crash in class (a 14 year old making a trans-us record attempt with her instructor stalled a mooney on takeoff), and my dad said that was the reason he never wanted to learn to fly to travel for business.
