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I'm not a pilot, but was wondering if someone may help.

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I'm not a pilot, but was wondering if someone may help.

Old 25th Jun 2019, 21:02
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I'm not a pilot, but was wondering if someone may help.

I was trying to determine the approximate height that a helicopter can hover at for a prolonged period without being buffeted by the wind, and at such height what would be the approximate visible distance if you were to look out to sea. Many thanks in advance.
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Old 25th Jun 2019, 23:03
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1. Many thousands of feet.
2. Many miles. Perhaps 30+ on a clear day.

It all depends on the weather on the day.
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Old 25th Jun 2019, 23:56
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The distance depends on quite a few variables but this will give you the maximum possible distance for any given height

Distance to the Horizon Calculator

For example:
1000' = 33Nm
5000' = 75Nm
10,000' = 106Nm
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Old 26th Jun 2019, 00:55
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Originally Posted by Dan9048 View Post
I was trying to determine the approximate height that a helicopter can hover at for a prolonged period without being buffeted by the wind, and at such height what would be the approximate visible distance if you were to look out to sea. Many thanks in advance.
Well, one time at Half Moon Bay I got the shit buffeted out of me by the wind, and I was at only a five foot hover.

I could see miles out to sea though, as it was a nice, clear day :-)
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Old 26th Jun 2019, 05:01
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It differs from helicopter to helicopter. For a very still day where wind isn't pushing you around (that's hypothetical - above 2000ft AGL you'll always find some wind) you'd be limited by the helicopter's power and Hover Out of Ground Effect ceiling for your particular mass. For the distance part, you're welcome to crack on with the Tangent-Secant theorem in your own time but the answers will be theoretical maximums because real-world visibility will often be less than the earth's horizon. Especially above the sea, high humidity will give you either haze on a warm day or clouds and showers on less warm days, and you can't see through much of either.
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Old 26th Jun 2019, 06:07
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Dan, if you can put why you want to know this into some sort of context it might help you get more specific answers.
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Old 26th Jun 2019, 22:00
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Data point: a few months back I did a project where we sat at 5500' MSL (5000' AGL) with a 500lb camera system on the aircraft, for two hours, in one position. Well, "in one position" is relative as the aircraft wasn't autopilot-equipped so positional accuracy was limited to the pilot's ability, given limited reference points from that altitude. That was in an AS350B3e.

Given, there was some breeze up at that altitude, and it's unlikely you'd find no wind that high up. Like was mentioned earlier in the threads, all depends on the weather (and the machine).
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Old 27th Jun 2019, 12:15
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Originally Posted by MikeNYC View Post
Data point: a few months back I did a project where we sat at 5500' MSL (5000' AGL) with a 500lb camera system on the aircraft, for two hours, in one position. Well, "in one position" is relative as the aircraft wasn't autopilot-equipped so positional accuracy was limited to the pilot's ability, given limited reference points from that altitude. That was in an AS350B3e.

Given, there was some breeze up at that altitude, and it's unlikely you'd find no wind that high up. Like was mentioned earlier in the threads, all depends on the weather (and the machine).
How was your foot after pushing on the pedals in the hover for 2 hours???!!!
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Old 27th Jun 2019, 14:33
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Originally Posted by Kulwin Park View Post
How was your foot after pushing on the pedals in the hover for 2 hours???!!!
I was in the back seat manning the camera system. The pilot, on the other hand, probably went to the chiropractor after our flight.
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Old 27th Jun 2019, 14:43
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I was taught a big handfuls method whereby you take your ht in feet and the sq root of that gives the horizon in miles. I.e. 900ft high visible horizon is approx 30 miles away; 5000ft and horizon is about 70 miles.
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Old 27th Jun 2019, 15:11
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Back in the late 60’s/early 70’s ( I think ) there was a test program called Project High Drink, wherein a USN SH-3 was to hover for extended periods at 10,000 ft, refueled by a flexible metal fuel line. Kurt Cannon was the project test pilot and Larry Russel a senior test engineer. They did the flying at the Augusta Ga. airport as I recall, but I do not recall what the purpose was. I do recall seeing pictures of the ground support equipment, fuel line on a huge reel etc. They did a bunch of flights, but that’s all I can recall.
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Old 27th Jun 2019, 17:59
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John,
It is a little foggy, but I think it was Jim Sherry who was there for a while who told me that eventually the tube failed into many pieces and rained down without hurting anyone. I don't know if it was filled with fuel. If it was it must have been a scary situation. I think the idea was to use the helicopter as a sensor platform.
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Old 28th Jun 2019, 06:48
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Jeez, the pressure at the bottom would be huge. I could work it out, but I'd rather finish my beer.
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Old 28th Jun 2019, 12:07
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Thanks for the history Al M. You have better memory on this one than I. There were two Sherry brothers as I recall, Jim and I think Maurice, both very good folks. I recall that there wasn’t a long list of guys wanting to get into that test program, to put one aspect of the discussion in perspective, delicately. You know, one of those situations where one didn’t want to show real interest.......

Last edited by JohnDixson; 28th Jun 2019 at 12:17. Reason: wording
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Old 28th Jun 2019, 12:25
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Well if it takes 1 atmosphere to push water up 34 feet .. about 4.6 psi / 100 ft; it isn't a hard calculation. about 460 psi. 2 miles of pipe must have been a bit heavy though.
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Old 28th Jun 2019, 21:22
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Originally Posted by Dave Gittins View Post
Well if it takes 1 atmosphere to push water up 34 feet .. about 4.6 psi / 100 ft; it isn't a hard calculation. about 460 psi. 2 miles of pipe must have been a bit heavy though.
Watch out where you put your decimal point.
14.7psi / 32.2 feet = ~4600psi at 10,000'. A bit less for fuel with a relative density of less than 1.

(I feel vaguely dirty doing that in imperial units)
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