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and the nodding caused by the blades passing over the cockpit I'd guess a decently balanced and correctly tracking 2 bladed rotor should not infere more mechnical vibration to the fuselage than any other number of blades. |
I think the blade passing frequency as the downwash impacts the cockpit roof is a quite well-documented source of vibration and noise - well tracked or not.
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The Chinook had a tendency to cause Flicker Vertigo with the right sun direction beaming down through the Forward Rotor System and reflecting off the Attitude Indicator.
Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light."[1] It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.[2][3] The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy. This phenomenon has been observed during helicopter flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes. Flicker vertigo in a helicopter occurs when the pilot or front passenger looks up through the blades of the main rotor as it turns in the sun causing the light to strobe. The strobe light effect causes persons who are vulnerable to flicker vertigo to become disoriented, lose control of the aircraft or have a seizure. A similar situation can occur in fixed wing flight whenever flickering light conditions exist. An example would be looking through a slowly spinning propeller while the airplane is landing facing the sun.[4] According to The US Naval Flight Surgeons Manual, flicker vertigo is a rare occurrence.[5] Flicker vertigo has been considered as a principle for various forms of non-lethal weapon.[6][7] A related crowd-control device was invented by Charles Bovill, which "employed a combination of ultra-sonic waves and strobe lights to induce acute discomfort, sickness, disorientation and sometimes epilepsy."[8] |
crab@, may I surmise that you don't have a lot of time in the 205/212 series?
For most of us it's the Mack truck of the skies, and should have a Mack bulldog on the nose ;) Cockpit blade noise is purely a background issue since most of the work done is of a short range/aerial work type. I managed to throw water at the ground again yesterday and hit it every time; any blade noise was only noticed when a bit of 'fly neighbourly' was called for :ok: Flicker vertigo is neatly negated by having a sunshade in the overhead...... cue howls of outrage for reducing vision, etc, from those who don't flog around in 35C+ :p |
Have to agree John, although i have friends who say it would be the Peterbuilt of the sky...
Busy in OZ yet? or just a normal start to the fire season? |
crab@, may I surmise that you don't have a lot of time in the 205/212 series? Flicker vertigo/flicker epilepsy is also well documented on some French roads where the spacing of the trees causes the low sun to flash at exactly the right frequency if you are driving around the speed limit. ISTR it was one of the things covered in initial aircrew medicals for the British Military - they wired you up to an EEG and then flashed strobes at you to see if it triggered a fit. |
Indeed, the same test is part of the medical for a Netherlands commercial licence. Mind you, their medical takes a whole day from specialist to specialist; no doubt the CAA are the same these days?
Whilst we've danced around the UH1/205 series blades for unique noise, for sheer decibels the 214B on the fireline doesn't need a siren prior to a drop :cool: |
Come on guys!!!
It's not NOISE, it's .....the sound of FREEDOM! Wock! wock! wock! or in an Agusta-Bell, Wop! wop! wop! The best noise complaint generated was from a B222 in a high hover over North Sydney back in 1985 when on trials for the Polair boys- apparently the police switchboard lit up like a Xmas tree, and Base called us to ask what the heck we were doing to make so many people ring up? The answer was simply - hovering. And then when I got back to base, a bird decided to commit suicide by dividing itself on the angled tip of the blade. A Cocka-one became a cocka-two. More feathers and guts than you could poke a stick at, and a really strange POP! sound. |
or in an Agusta-Bell, Wop! wop! wop! |
If Memory serves me right....the 412 requires an overhead shade for IFR flight. Not that we ever did but I do recall a Warning or Caution Note to that effect.
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214ST
In '80 or '81 three 214 ST's, 18401, 18402, 18403 joined up in return flight to Arlington airport from morning's data flights. (Development flights pre-production 214ST) I was FTE onboard 18403, broke the control tower's glass. We were at medium GW but the other two A/C were both heavy at the time.:=
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Here are 2 more, one from a B214B in winter and the other from a B205 at altitude
JD B214B B205 |
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